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Glossary
A
Absolute Feedback
With the shaft in any position at motor start, the data from an absolute feedback
mechanism always relays the position of the shaft. A non-absolute feedback
mechanism must start from a known rotational position, such as the index pulse.
Absolute Move
A positioning mode in which all moves are referenced to a fixed origin position.
for examble, if a stage is at +5 inches, an absolute move to +3 inches would
result in a move of 2 inches toward the origin.
Absolute Positioning
Refers to a motion control system enploying position feedback devices (absolute
encoders) to maintain a given mechanical location.
Absolute Programming
A positioning coordinate reference where all positions are specified relative to
some reference, or "home" position. This is different from incremental
programming, where distances are specified relative to the current position.
AC (Alternating Current)
The commonly available electric power supplied by an AC generator and is
distributed in single- or three-phase forms. AC current changes its direction of
flow (cycles).
AC Motor
A motor operating on AC current that flows in either direction (AC current). There
are two general types: induction and synchronous.
Acceleration
A change in velocity as a function of time. Acceleration usually refers to
increasing velocity, and deceleration to decreasing velocity.
Accuracy
A measure of the difference between expected position and actual position of a
motor or mechanical system. Motor accuracy is usually specified as an angle
representing the maximum deviation from expected position.
Actuator
A device which creates mechanical motion by converting various forms of energy
to mechanical energy. Also known as a self contained leadscrew system which
converts rotary motion (from a motor) to linear motion.
Adaptive Control
A technique to allow the control to automatically compensate for changes in
system parameters such as load variation.
Amplifier
Electronics which convert low-level command signals to high power voltages and
currents to operate a servo motor. Electronics that convert low level command
signals into high power voltages and currents to operate an electrical device.
Amplifier, PWM
A device which draws power from an independent source to produce a magnified
pulse width modulated power signal form of a controlling input signal.
Analog
A device or circuit in which the output varies as a continuous function of the input.
ASCII (American Standard Code for Information
Interchange)
This code assigns a number to each numeral and letter of the alphabet. In this
manner, information can be transmitted between machines as a series of binary
numbers.
Asynchronous Machine
Any machine in which the output speed is not dependent of the excitation
frequency.
B
B. EMF Harmonic Distortion
Root sum squares of the rms values of non fundamentals as a percentage of
fundemental rms values.
Bandwidth
The frequency range in which the magnitude of the system gain expressed in dB
is greater than -3 dB.
BCD (Binary Coded Decimal)
A binary numbering system in which the decimal digits 0 to 9 are represented by
a 4 bit binary number. Each digit in a decimal number assigned a four bit binary
code.
Example: 156 = 0001 0101 0110.
Base two numbering system. Each number being expressed in the powers of
two, by 0 or 1.
Bit (Binary Digit)
A unit of information equal to 1 binary decision or having only a value 0 or 1.
Bode Plot
A plot of the magnitude of system gain in dB and the phase of system gain in
degrees versus the sinusoidal input signal frequency in logarithmic scale.
bps
Bits per second
Brush
A piece of current conducting material (usually carbon or graphite) which rides
directly on the commutator of a commutated motor and conducts current from the
power supply to the armature windings.
Brushless motor
Class of motors that operate using electronic commutation of phase currents,
rather than electromechanical (brush-type) commutation. Brushless motors
typically have a permanent magnet rotor and a wound stator.
Brushless Servo Drive
A servo drive used to control a permanent magnet synchronous AC motor. May
also be referred to as an AC Servo Drive.
Brushless Servomotor
A class of servomotors which operates using electronic commutation of phase
currents rather than electromechanical (brushes) commutation. Commutation is a
function of rotor position. These motors typically have a permanent magnet rotor
and wound stator. An "inside-out" DC motor with a permanent magnet rotor and
electrical coils in the stator. Commutation of current in the windings is typcially
achieved via external switching transistors and Hall-effect detectors. This type of
motor avoids the limited life of brushes and their radiated EMI.
Biss
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C-face mounting
A standard NEMA mounting design, where the mounting holes in the face are
threaded to receive the mating mount.
CAM Profile
A technique used to perform non-linear motion electronically similar to that
achieved with mechanical cams.
Cantilevered Load
Any load not symmetrically mounted on a stage. Such loads exert torque
moments upon the ways, and the resulting deformations can degrade accuracy.
Capacitor
A device which, when connected in an alternating-current circuit, causes the
current to lead the voltage in time phase. The peak of the current wave is
reached ahead of the peak of the voltage wave. This is the result of the
successive storage and discharged of electric energy used in single-phase
motors to start, or in three-phase motors for power factor correction.
CE
The designation shows that a product such as a motor or control meets European
Standards for safety and environmental protection. A CE mark is required for
products used in most European Countries.
Closed loop
A broadly applied term, relating to any system in which the output is measured
and compared to the input. The output is then adjusted to reach the desired
condition. In motion control, the term typically describes a system utilizing a
velocity and/or position transducer to generate correction signals in relation to
desired parameters.
Closed Loop Positioning
The use of information from external feedback devices, such as encoders, in
controlling a motor's movement to reach a desired position.
Command Position
The desired angular or linear position of an actuator. The command position is
typically a signal that represents a realization of a motion control strategy.
Command Signal Generator
A device that supplies a command position signal to an automatic control system.
This signal represents the desired motion of the actuator that is required to
accomplish a task such as making a part. This signal is usually in the form of an
electrical signal.
Commutation
1. A term which refers to the action of steering currents or voltages to the proper
motor phases so as to produce optimum motor torque. In brush type motors,
commutation is done electromechanically via the brushes and commutator. In
brushless motors, commutation is done by the switching electronics using rotor
position information obtained by Hall sensors, a Tachsyn, or a resolver.
2. Commutation of step motors is normally done open loop. Feedback from the
motor is not required to hold rotor position precisely.
Comparator
A device where the feedback signal is subtracted from the command signal. The
difference output of the comparator is called the error signal.
Compensation
The adjustment of gain and requency parameters in a closed-loop system to
achieve the desired dynamic response and also to insure a stable (nonoscillating) condition.
Compensation, Feed-forward
A control action which depends on the command only and not the error to
improve system response time.
Compensation, Integral
A control action which is proportional to the integral or accumulative time error
value product of the feed back loop error signal. It is usually used to reduce static
error.
Compensation, Lag
A control action which causes the lag at low frequencies and tends to increase
the delay between the input and output of a system while decreasing static.
Compensation, Lead
A control action which causes the phase to lead at high frequencies and tends to
decrease the delay between the input and output of a system.
Compensation, Lead-Lag
A control action which combines the characteristics of lead and lag
compensations.
Compensation, Proportional
A control action which is directly proportional to the error signal of a feedback
loop. It is used to improve systems accuracy and response time.
Compliance
The amount of displacement per unit of applied force.
Compliant Coupling
The limited motion of one coupled shaft without causing motion of the other
coupled shaft that does not permit permanent displacement of one shaft with
respect ot the other.
Conductor
A material such as copper or aluminium which offers low resistance or opposition
to the flow of electric current.
Control Systems or
Automatic control
Systems
An engineering or scientific field that deals with controlling or determining the
performance of dynamic systems such as servo systems.
Controller
A term describing a functional block containing an amplifier, power supplies, and
possibly position-control electronics for operating a servomotor or step motor.
Controller /
Microncontroller
A device that incorporates many or all functions of a computer in a single
integrated circuit. Used to perform and logic required to do motion or process
control.
Current
The measure of electrical flow, measured in Amps.
D
Daisy Chain
A term used to describe the linking of several RS232C devices in sequence such
that a single data stream flows through one device and on to the next. Daisychained devices usually are distinguished by device addresses which serve to
indicate the desired destination for data in the stream.
DBF
Data base format; data base file
DC (Direct Current)
A current that flows only in one direction in an electric circuit. It may be
continuous or discontinuous and it may be constant or varying.
Deceleration
The rate velocity decreases as a function of time.
Decibel (db)
A logarithmic measurement of gain. If G is a systems gain (ratio of output to
input) then 20 log G = gain in decibels (db)
Dielectric Material
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Dielectric Test
A high voltage breakdown test of insulation's ability to withstand an AC voltage.
Test criterion limits the leakage current to a specified magnitude and frequency,
applied between the specified test points.
Differential
An electrical input or output signal which uses two lines of opposite polarity
referenced to the legal signal ground.
Digital
A device or circuit in which the output varies in discrete steps, i.e., pulses or onoff operation.
Distributed Processing
A technique to gain increased performance and modularity in control systems
utilizing multiple computers or processors.
Drive
An electronic device that controls torque, speed and/or position of an AC or
brushless motor. Typically a feedback device is mounted on the motor for closedloop control of current, velocity and position.
Drive, Analog
Usually refering to any type of motor in which the input is an analog signal.
Drive, Digital
Usually referring to any type of motor drive in which the tuning or compensation is
done digitally. Input may be an analog or digital signal.
Drive, Linear
A motor drive in which the output is directly proportional to either a voltage or
current input. Normally both inputs and outputs are analog signals. This is a
relatively inefficient drive type.
Drive, PWM
A motor drive utilizing Pulse-Width Modulation techniques to control power to the
motor. Typically a high efficiency drive that can be used for high response
applications.
Drive, SCR
A DC motor drive which utilizes internal silicon controlled rectifiers as the power
control elements. Usually used for low bandwidths, high power applications.
Drive, Servo
A motor drive which utilizes internal feedback loops for accurate control of motor
current and/or velocity.
Drive, Stepper
Electronics which convert step and direction inputs to high power currents and
voltages to drive a stepping motor. the stepping motor driver is analogous to the
servo motor amplifier.
E
Eddy Current
Localized currents induced in an iron core by alternating magnetic flux. These
currents translate into losses (heat) and their minimization is an important factor
in lamination design.
EEPROM
Electrically Erasable Programmable Read Only Memory. Re-writable non-volatile
memory chip. The contents of the EEPROM is not lost after power is turned off.
Effective Torque
The root mean square value of the instantaneous torque value over a given
cycle.
Efficiency
The ratio of power output to power input.
Electrical Degree
A unit of measurement of time as applied to alternating current. One complete
cycle equals 360 electrical degrees. Once cycle in a rotating field moves from
one pole to the next pole of the same polarity. There are 360 electrical degrees in
this time period. Therefore, in a two pole machine there are 360 degrees in one
revolution, and the electrical and mechanical degrees are equal. In a machine
with more than two poles, the number of electrical degrees per revolution is
obtained by multiplying the number of pairs of poles by 360.
EMI (Electro-Magnetic Interference)
EMI is noise which, when coupled into sensitive electronic circuits, may cause
problems.
Enable
A signal that permits a circuit to be activated.
Encoder
A feedback device which converts mechanical motion into electronic signals. The
most commonly used, rotary encoders, output digital pulses corresponding to
incremental angular motion. For example, a 1000-line encoder produces 1000
pulses every mechanical revolution. The encoder consists of a glass or metal
wheel with alternating transparent and opaque stripes, detected by optical
sensors to produce the digital outputs.
Encoder Resolution
A measure of the smallest positional change which can be detected by the
encoder.
Encoder, Absolute
A digital position transducer in which the output is representative of the absolute
position of the input shaft within one (or more) revolutions. Output is usually a
parallel digital word.
Encoder, Incremental
A position encoding device in which the output represents incremental changes in
position.
Encoder, Linear
A digital position transducer which directly measures linear position.
Encoder, Marker
A one-per-revolution signal provided by some incremental encoders to specify a
reference point within that revolution. Also known as Zero Reference signal or
index pulse.
ERP
Enterprise Resource Planning
Ethernet Hub
A device for combining multiple Ethernet segments (typically 10BaseT) into a
single segment. All traffic appearing on any port of a hub will be echoed to all of
the other ports instantaneously.
Ethernet Switch
A device for connecting multiple Ethernet segments, while maintaining them as
separate segments. Unlike a hub, a switch will intelligently route packets to the
appropriate port (only) based on the MAC-level (OSI Layer 2) address in the
packet.
F
Feed Forward
A technique used to pre-compensate control a loop for known errors due to
motor, drive, or lead characteristics. Provides improved response.
Feedback
A signal which is transferred from the output back to the input for use in a closed
loop system.
Ferrite
A type of permanent magnet consisting of ceramic compounds made up of
oxides of iron, barium and strontium.
Field
A term commonly used to describe the stationary (stator) member of a DC motor.
the field provides the magnetic field with which the mechanically rotating
(armature or rotor) member interacts.
Field Weakening
A method of increasing the speed of a wound field motor by reducing stator field
intensity by reducing winding current.
Filter (control systems)
A transfer function used to modify the frequency or time response of a control
system.
FIM
Facilities information management
Flatness OT Travel
The extent to which the straight line movement of a linear actuator is parallel to
the base of the unit.
Flutter
Flutter is an error of the basic cycle of an encoder per one revolution.
Flux
The magnetic field which is established around an energized conductor or
permanent magnet. The field is represented by flux lines creating a flux pattern
between opposite poles. The density of the flux lines is a measure of the strength
of the magnetic field.
Following Error
The positional error curing motion resulting from use of a position control loop
with proportional gain only.
Force
The action of one body on another which tends to change the state of motion of
that body. Typically described in terms of magnitude, direcion, and point of
application.
Form factor
The ratio of RMS current to average current. This number is a measure of the
current ripple in a SCR or other switch-mode type of drive. Since motor heating is
a function of RMS current while motor torque is a function of average current, a
form factor greater than 1.00 means some fraction of motor current is producing
heat but not torque.
Four quadrant
Refers to a motion system which can operate in all four quadrants; i.e., velocity in
either direction and torque in either direction. This means that the motor can
accelerate, run, and decelerate in either direction.
Frictional Losses
The loss of energy due to the friction of moving parts.
Friction
A resistance to motion caused by contact with a surface. Friction can be constant
with varying speed (Coulomb friction) or proportional to speed (viscous friction).
Full Load Current
The armature current of a motor at its full load torque and speed with rated
voltage applied
Full Load Speed
The speed of a motor operated with rated voltage and full load torque.
G
Gain
The ratio of system output signal to system input signal. The control loop
parameter that determines system performance characteristics.
Gearhead
The portion of a gearmotor, which cotnains the actual gearing which, converts the
basic motor speed to the rated output speed.
Gearmotor
A gearhead and motor combination to reduce the speed of the motor to obtain
the desired speed or torque.
GIB Force
It is a clamping force between two devices.
GIS
Geographical information system, a system used to combine different types of
geographical related information, such as water mains, sewers, power lines and
roads.
GPS
global positioning system; satellites that continually transmit timing signals that
allow a receiver to find its position.
Gravitational Constant
The acceleration of a free falling body due to the earth's gravitational pull. Equal
to 9.8 m/s2, 32.2 ft/sec2
GUI
Graphical user interface; a program that lets users select icons representing
commands and prompts for parameter entries through dialog boxes
H
Hall sensor
A feedback device which is used in a brushless servo system to provide
information for the amplifier to electronically commutate the motor. The device
uses a magnetized wheel and hall effect sensors to generate the commutation
signals.
HMI
human-machine interface; discriminatory term
Holding torque
Sometimes called static torque, holding torque specifies the maximum external
torque that can be applied to a stopped, energized motor without causing the
rotor to rotate. Generally used as a figure of merit when comparing motors.
Home
A reference position in a motion control system. Often designated as the zero
position.
Home Limit Switch
Any device which locates the position of the zero reference.
Home Position
A reference position for all absolute positioning movements. Usually defined by a
home limit switch and/or encoder marker. Normally set at power up and retained
for as long as the control system is operational.
Horsepower
An index of the amount of work a machine or motor can perform. One
horsepower is equal to 746 watts. Since power is equal to torque multiplied by
speed, horsepower is a measure of a motor's torque and speed capability; e.g., a
1 HP motor will produce 36 lb-in. at 1,750 rpm.
Formula:
HP = Torque (lb-in.) x Speed (RPM)/63,025
or
HP = Torque (lb-ft.) x Speed (RPM)/5,252
or
HP = Volts x Amps x Efficiency/746
Host Computer
An auxiliary computer system which is connected to a controller or controllers.
The host computer in distributed control systems is frequently involved with
controlling many remote and distributed motion control devices. It may also be
used for off-line tasks such as program preparation, storage, supervisory control
and evaluation.
HTML
hypertext markup language
HTTP (Hypertext Transfer Protocol)
A simple extensible protocol used for data exchange over the Internet. Browsers
use HTTP to communicate with servers.
Hunting
The oscillation of the system response about a theoretical steady-state value.
Hybrid step motor
A motor designed to move in discrete increments of steps. The motor has a
permanent magnet rotor and a wound stator. Such motors are brushless. Phase
currents are commutated as a function of time to produce motion.
Hysteresis
The counter-force stored in an elastic material or mechanism after the outside
forces acting on it have been changed. Commonly referred to as the difference
between the position when approached from one direction and the same position
when approached from the opposite direction. An example is the mechanical
wind-up in the lead screw assembly.
I
I&C
information and control
I/O (Input/Output)
The reception and transmission of information between control devices. In
modern control systems, I/O has two distant forms: switches, relays, etc. which
are either an on or off state, or analog signals that are continuous in nature such
as speed, temperture, flow, etc.
I2R
Losses due to current flowing in a conductor caused by resistance (equals the
current squared times the resistance).
Idle current reduction
A step motor driver feature that reduce the phase current to the motor when no
motor motion is commanded (idle condition) for a specified period of time. Idle
current reduction reduces motor heating and allows high machine throughputs
from a given motor.
IIMS
integrated information management system, a system that links two or more
client computer systems to automatically exchange information
IMS
Information management system
Incremental Motion
A motion control term that is ued to describe a device that produces one step of
motion for each step command (usually a pulse) received.
Incremental Move
A move referenced from the current set position.
Indexer
Electronics which convert high level motion commands from a host computer,
PLC or operator panel into step and direction pulse streams for use by the step
motor driver. Indexers can be broadly divided into two classes. A preset indexer
typically accepts distance, velocity and ramp time inputs only. The more
sophisticated programmable indexer is capable of complex motion control and
includes program memory.
Inductance
The characteristic of an electric circuit by which varying current in it produces a
varying magnetic field which causes voltages in the same circuit or in a nearby
circuit.
Inductance (L) (mH - millihenries line-to-line)
The electrical equivalent to mechanical inertia; that is, the property of a circuit,
which has a tendency to resist current flow when no current is flowing, and when
current is flowing has a tendency to maintain that current flow. Electromate®
measures inductance (line-to-line) with a bridge at 1000 Hz and with the rotor
positioned so the back-EMF waveform is at the peak of the sinusoid.
Inductance (mutual)
Mutual inductance is the property that exists between two current carrying
conductors or coils when magnetic lines of force from one link with those of the
other.
Inductance (self)
The self-inductance of a coil is the constant by which the time rate of change of
the current in the coil must be multiplied to give the self-induced counter EMF.
Inertia
The property of an object to resist change in velocity unless acted upon by an
outside force. Higher inertia objects require larger torques to accelerate and
decelerate. Inertia is dependent upon the mass and shape of the object.
Inertia Match
An inertial match between motor and load is obtained by selecting the coupling
ratio such that the load moment of inertia reflected to the motor shaft is equal to
the motor moment of inertia.
Inertial match
For most efficient operation, the system coupling ratio should be selected so that
the reflected inertia of the load is equal to the rotor inertia of the motor.
Inhibit
A signal that prevents the circuit from functioning.
Inrush Current
The current surge generated when a piece of equipment such as a servo
amplifier is connected to an AC line. This surge is typically due to the impulse
charging of a large capacitor located in the equipment.
Instability
Undesirable motion of an actuator that is different from the command motion.
Instability can take the form or irregular speed or hunting of the final rest position.
Instantaneous Start-Stop Rate
The maximum switching rate at which an unloaded step motor can run without
losing synchronism, or missing steps from a stanstill, or stop without taking more
steps than pulses.
Insulation Class
The rating assigned to the maximum temperature capability of the insulating
components in a motor or other piece of equipment.
Intermittent Duty Zone
The RMS torque applied over a period of time that is not greater than the rated
torque. The peak torque should not exceed the intermittent duty zone.
Intermittent-Duty Rating
The output rating of a device operated for a limited interval rather than
continuously.
IP
Internet Protocol, the transport protocol used on the Internet and many private
networks.
IPsec
IP Security Architecture, a proposed Internet standard for providing security
services at the IP layer level. Some early implementations exist, for example in
Cisco routers.
ISDN
Integrated Services Digital Network
ISO
International Standards Organization
ISP
Information Solutions Practice; Internet Service Provider; Interoperable System
Project
ITS
Intelligent Transportation Systems
J
No terms available
K
kbps
kilobps, one thousand bps
Kerberos
An authentication protocol employing "tickets" generated with private key
encryption to authorize transactions between a user and a remote server.
Kerberos
An authentication protocol employing "tickets" generated with private key
encryption to authorize transactions between a user and a remote server.
L
L2TP
Layer 2 Tunneling Protocol, an emerging standard for "tunneling" a variety of
protocols across an IP connection. It is being forged as a compromise between
Cisco's Layer 2 Forwarding (L2F) and Microsoft's (et al) PPTP.
Laminations
The steel portion of the rotor and stator cores make up a series of thin
laminations (sheets) which are stacked and fastened together by cleats, rivets or
welds. Laminations are used instead of a solid piece in order to reduce eddycurrent losses.
LAN
Local area network
Lead
The linear distance a nut on a leadscrew will travel with one revolution of the
leadscrew.
Lead Ball Screw
A lead screw which has its threads formed as a ball bearing race; the carriage
contains a circulating supply of balls for increased efficiency.
Lead Screw
A device for translating rotary motion into linear motion, consisting of an
externally threaded screw and an internally threaded carriage (nut).
Lead Screw Pitch
The number of full rotations required to advanced a nut by 1" inch. lead is
reciprocal to pitch. Metric screws are specified by lead only.
Least Significant Bit
The bit in a binary number that is the least important, or having the least weight.
Life
The life of an actuator as a function of load and stroke length.
Limit Switch
A sensor, typically hall effect, optical, eddy current, or mechanical, which is used
to sense the end of travel of a linear motion assembly. In addition to preventing
over travel, it is frequently used to establish a precision reference. A sensor that
signals the control to do something when a preset location is reached.
Limits
Motion control systems may have sensors called limits that alert the control
electronics that the physical end of travel is being approached and that motion
should stop.
LIMS
laboratory information management system
Line Shaft
A shaft rotated by the primary motor drive. The line shaft transmits power from
the motor to a load or series of loads. In the multiple load case, the loads are
synchronized to one another because they are connected to the common shaft.
Linear Coordianted Move
A coordinated move where the path between endpoints is a line.
Linear Position Accuracy
The error between desired move and actual position achieved by a linear
positioning components or stage system. The linear accuracy of components:
motor accuracy, leadscrew accuracy, stage accuracy (Pitch and Yaw), and
thermal expansion.
Linearity
For a speed control system it is the maximum deviation between actual and set
speed expressed as a percentage of set speed.
Load
A device or mass to be moved or manipulated.
Load
The burden imposed on a motor by the driven machine. It is often stated as the
torque required to overcome the resistance of the machine it drives. Sometimes
"load" is synonymous with "required power."
Load Angle - Dynamic
The angle between the loaded and unloaded position (theoretical zero) of the
rotor at a given instant under otherwise identical conditions at a specified
command pulse rate, mode of winding excitation and phase current.
Load Angle - Static
The angle between the magnetic axis of the stator and rotor magnetic fields with
the motor driving a specified load.
Logic Ground
An electrical potential to which all control signals in a particular system are
referenced.
Loop Gain, Open
the product of the forward path and feedback path gains.
Loop, Feedback Control
A control method that compares the input from a measurement device, such as
an encoder or tachometer, to a desired parameter, such as a position or velocity
and causes action to correct any detected error. Several types of loops can be
used in combination (i.e. velocity and position together) for high performance
requirements.
Loop, PIC (Proportional, Integral, and
Derivative Loop)
Specialized very high performance control loop which gives superior response.
Loop, Position
A feedback control loop in which the controlled parameter is motor position.
Loop, Velocity
A feedback control loop in which the controlled parameters is mechanical
veloctiy.
Losses
A motor converts electrical energy into a mechanical energy and in so doing,
encounters losses. These losses are all the energy that is put into a motor and
not transformed to usable power but are converted into heat causing the
temperature of the windings and other motor parts to rise.
M
Mass
The quantity of matter that an object contains.
Master Slave Motion Control
A type of coordinated motion control where the master axis position is used to
generate one or more slave axis position commands.
Matched Load
A load inertia equal to the driving element (motor rotor) inertia.
Maximum reversing Rate
The maximum pulse rate at which an unloaded step motor is able to reverse and
remain in synchronism.
Maximum Slew Range
The maximum rate at which the step motor will run and remain in synchronism.
This velocity is usually defined in the full step mode of 1.8 degree steps or as
shaft speed in revolutions per second.
Mbps
Megabps, one million bps
MCS
management consulting services
Mechanical Damper
A device of known inertia which attaches to the step motor shaft for damping step
oscillations and preventing resonance's.
Mechanical time constant (tm) (Seconds)
In a simple first order system, the time required for the motor's speed to attain
63.2% of its final value for a fixed voltage level. Can be calculated from: where: J
is inertia in lb-in./s2 R is resistance in ohms KT is torque constant in lb-in./amp.
8.87 is a conversion factor tM is calculated in seconds
Microprocessor
A miniaturized computer system that executes instructions in a sequential
manner. The sequential instructions form a control strategy for devices that may
be connected to the system. The sequential instructions are loaded into
microprocessor and can be easily changed or modified. Modern microprocessors
are small electronic devices that execute a wide range of instructions at speeds
as high as 1,000,000 instructions per second.
Microstepping
An electronic technique for increasing a step motor's position resolution and
velocity smoothness by appropriately scaling the phase currents. Microstepping
is also a technique used to reduce or eliminate the effects of system resonance
at low speeds.
Mid-range instability
A phenomenon in which a step motor can fall out of synchronism due to a loss of
torque at mid-range speeds. The torque loss is due to the interaction of the
motor's electrical characteristics and the driver's electronics. Some drivers have
circuitry to eliminate or reduce the effects of mid-range instability.
MIPS
million instructions per second; a measure of computational speed
MIS
management information system; the suite of applications used by management
to coordinate results from other subsystems such as LIMS and SCADA
MMI
mind-machine interface
MMS
maintenance management system
Modbus/TCP
A protocol used for Modbus messaging in an Internet or Intranet environment.
Moment Load
Pitch, Roll, and Yaw.
Most Significant Bit
The bit in a binary number that is the most important or that has the most weight.
Motion Profile
A method of describing a move operation in terms of time, position, and velocity.
Typically velocity is characterized as a function of time or distance which results
in a triangular or trapezoidal profile.
Motor
A device that takes electrical energy and converts it into mechanical energy to
turn a shaft.
Motor Constant
The ratio of the motor torque to motor input power.
Motor, AC
A device that converts electrical alternating current into mechanical energy.
requires no commutation devices such as brushes. Normally operated off
commercial AC power. Can be single or multiple phase.
Motor, AC Asynchronous or Induction
An AC motor in which speed is proportional to the frequency of the applied AC.
Requires no magnets or field coil. Usually used for non-precise constant speed
applications.
Motor, AC Synchronous
Another term for brushless DC motor.
Motor, DC
A device that converts electrical direct current into mechanical energy. It requires
a commutating device, either brushes or electronic. Usually requires a source of
DC power.
Motor, DC Brushless
A type of direct current motor that utilizes electronic commutation rather than
brushes to transfer current.
Motor, DC Permanent Magnet
A motor utilizing permanent magnets to produce a magnetic field. Has linear
torque speed characteristics.
Motor, DC Wound Field
A direct current utilizing a coil to produce a magnetic field. Usually used in high
power applications where constant horsepower operation is desired.
Motor, Stepping
A specialized AC motor that allows discreter positioning without feedback.
Normally used for non-critical, low power applications, since positional
information is easily lost if acceleration or velocity limits are exceeded. Load
variations can also cause loss of position. If encoders are used, these limitations
can be overcome.
MOV: Metal Oxide Varistor
A device that suppresses the voltage transients occurring on an AC line.
Multi-axis Control System
Is a system designed to control more than one actuator. This type of controller
allows the actuators to work independently or as a coordinated group to perform
more complex tasks.
Multi-turn Encoder
A multi-turn encoder stores the number of rotations made by the shaft in nonvolatile memory. See also Single-turn encoder.
N
NC, Numerical Control
Usually refers to any type of automated equipment or process used for
contouring or positioning.
Negative Feedback
The type of feedback's used in a closed loop system where the output value is
inverted and combined with the input to be used to stabilize or improve system
characteristics. The difference is used by the system to move the actuator in such
a ways as to force the difference to zero.
Neodymium iron boron
A type of rare-earth permanent magnet material.
NIC
network interface card; PCB that interfaces a computer to a network
No Load Speed
Motor speed with not external load and full voltage applied.
Non-Volatile Memory
Information that is stored on a device that does not require continuous power to
be maintained. Typically associated with an EEPROM (Electrically Erasable
Programmable Memory) chip for memory storage.
NTC - Negative Temperature Coefficient
A negative temperature coefficient thermistor is used to detect and protect a
motor winding from exceeding its maximum temperature rating. Resistance of the
device decreases with an increase in temperature.
O
ODBC
open database connectivity
OI
operator interface; the hardware and software that shows an operator the state of
a process
OIS
operator interface station; operational intercomm system
OLE
object linking and embedding; a way of combining information from different files
OOP
Object Oriented Programming
Open Collector (NPN)
An output signal which is provided by a transistor where the "open collector
output" acts like a switch closure to ground when activated.
Open-loop
A system in which there is no feedback. Motor motion is expected to faithfully
follow the input command. Stepping motor systems are an example of open-loop
control.
Open-Loop Systems
A system where the command signal results in actuator movement but because
the mvoement is not sensed, there is no way to correct the error. Open loop
means no feedback.
Operator Interface
A device that allows the operator to communicate with a machine. This device
typically has a keyboard or thumbwheel to enter instructions into the machine. It
also has a display device that allows the machine to display messages.
Optical Encoder
A position or angular feedback device typically producing two pulse trains, phase
shifted 90 degrees from each other providing positioning and directional
information.
Optical Isolation
An interface circuit that transmits a signal with not direct electrical connection.
Optically Coupled
An interface circuit that transmits a signal with not direct electrical connection
except for the logic ground.
Optically Isolated
A system or circuit that transmits signals with not direct electrical connection.
Used to protectively isolate electrically noisy machine signals from the low-level
control logic.
Opto-Isolated
A method of sending a signal from one piece of equipment to another, which
provides electrical isolation. Signals are transmitted optically.
Oscillation
Undesirable motion of an actuator that is different from the command motion. See
Instability.
P
P&ID
process and instrumentation drawing/diagram
PC
personal computer
PCB
printed circuit board
Peak Rating
The maximum value obtained over a complete cycle, usually intermittent within
the system limits.
Peak torque (Tpk) (lb-in.)
The maximum torque a brushless motor can deliver for short periods of time.
Operating PacTorq motors above the maximum torque value can cause
demagnetization of the rare-earth magnets. This is an irreversible effect that will
alter the motor characteristics and degrade performance. This is also known as
peak current.
Not to be confused with system peak torque, which is often
determined by
amplifier peak current limitations, where peak current is typically two times
continuous current.
Phase
Is a set of electrically excited stator poles, consisting of one or more pairs of
oppositely polarized poles. Step motor manufacturers provide 4 lead motors with
bifilar ratings and 6 or 8 lead motors with unifilar ratings.
Phase and Phase Angle
The separation in electrical degrees between any specified transitions of any two
channels of an encoder.
Phase Angle Rotor-Stator
The angle of lag of the rotor to the axis of the stator magnetic field under load.
The angle of lag between rotor and stator teeth under load.
Phase Margin
The difference between 180 degrees and the phase angle of a system at the
frequency where the open loop gains is unity.
Phase-Locked Servo System
A hybrid control system in which the output of an optical tachometer is compared
to a reference square wave signal to generate a system error signal proportional
to both shaft velocity and positions errors.
PID (Proportinal-Intergral-Derivative)
An Acronym that describes the compensation structure that can be used in a
closed-loop system.
Pitch
The measurable distance between screw grooves or threads.
PLC (Programmable Logic Controller)
A programmable device which utilizes userdefined logic to control a bank of
inputs and outputs which are interfaced to external devices.
PMDC Motor (Permanent Magnet Direct Current)
A motor comprising a wound iron-core armature and a permanent magnet stator.
These brushed motors operate on DC power.
Point to Point Move
A multi-axis move from one point to another where each axis is controlled
independently. (NO coordination between axis is required.)
Pole
A frequency at which the transfer function of a system goes to infinity.
Pole Pair, Electromechanical
The number of cycles of magnetic flux distribution in the air gap of a rotary
electromechanical device.
Poles
Refers to the number of magnetic poles arranged on the rotor of the brushless
motor. Unlike an AC motor, the number of poles has no direct relationship to the
base speed of the motor.
Position Error
The difference between the present actuator (feedback) value and the desired
position command for a position loop.
Position Feedback
Present actuator position is measured by a position transducer.
POTS
Plain Old Telephone System (see PSTN), a commonly used acronym for dial-up
analog telephone lines.
Power
1. The rate at which work is done. In motion control, power is equal to torque
multiplied by speed.
2. The rate of doing work or expending energy. It may be written as: Power (watts)
= force x distance/time. Expressed in electrical terms it is voltage x current =
power (watts)
Power factor
Ratio of true power (kW) to apparent power (kVA).
PPTP
Point-to-Point Tunneling Protocol, a standard developed jointly by Microsoft, U.S.
Robotics, 3Com, and others, for tunneling PPP packets across IP connections.
This protocol, incorporated into Windows NT, Windows 95/98, and other
products, is now being merged with Cisco's Layer 2 Fowarding (L2F) into a new
Internet standard called Layer 2 Tunneling Protocol (L2TP).
Pre-Load
The compression of a bearing used to remove play with the anticipation of a load.
Primary Winding
The winding of a motor, transformer or other electrical device, which is connected
to the power source.
Process Control
A term used to describe the control of machine or Manufacturing processes,
especially in continuous production environments.
Programmable Logic Controller
An electronic device that scans on/off type inputs and controls on/off type
outputs. The relationship between the input and outputs are logical statements
that are programmable by the user.
PSTN
Public Switched Telephone Network, typically refers to common dial-up
telecommunications, often extended to include ISDN.
PTC - Positive Temperature
Coefficient
A positive temperature coefficient thermistor is used to detect and protect a motor
winding from exceeding its maximum temperature rating. Resistance of the
device increases with an increase in temperature.
Pull In Step Rate
The (constant) maximum pulse rate at which the energized stepping motor will
start driving a specified load without missing steps under specified drive
conditions.
Pull In Torque
The maximum torque at which an energized stepping motor will start driving a
specified load and run without losing steps, on application of a fixed pulse rate.
Pull Out Step Rate
The (constant) maximum pulse rate at which the energized stepping motor can
run driving a specified load under specified drive conditions without losing steps.
Pull-out torque
The maximum friction load, at a particular inertial load, that can be applied to the
shaft of a synchronous motor (running at constant speed) and not cause it to lose
synchronism.
Pull-Up Torque
The minimum torque developed by an AC motor druing th period of acceleration
from zero to the speed at which breadkown occurs. For motors, which do not
have a definite breakdown torque, the pull-up torque is the minimum torque
developed during the process of achieving rated speed.
Pulse rate
The frequency of the step pulses applied to a step motor driver. The pulse rate,
multiplied by the resolution of the motor/driver combination (in steps per
revolution), yields the rotational speed in revolutions per second.
Pulse Width
Modulation (PWM)
1. A PWM controller (amplifier) switches DC supply voltage on and off at fixed
frequencies. The length of the on/off interval or voltage waveform is variable.
2. Pulse width modulation (PWM), describes a switch-mode (as opposed to linear)
control technique used in amplifiers and drivers to control motor voltage and
current. PWM offers greatly improved efficiency compared to linear techniques.
Q
Quadrature
Refers to signal characteristics of interfaces to positioning devices such as
encoders or resolver's. Specifically, that property of position transducers that
allows them to detect direction of motion using the phase relationship of two
signal channels.
R
Rack & Pinion
A toothed bar (rack) which engages a gear (pinion) to convert rotary to linear
motion.
RAID
redundant array of inexpensive devices; usually a group of similar devices such
as disc drives that provide 100 percent back up and can survive failure of any
single component without losing functionality
RAM (Ram Access Memory)
A memory chip that can be read from and written to. Used for temporary
information storage. Data is lost after power loss.
Rated Torque
The torque producing capacity of a motor at a given speed. This is the maximum
continuous torque the motor can deliver to a load and is usually specified with a
torque/speed curve.
RDC: Resolver-to-Digital Converter
An electronic component that converts the analogue signals from a resolver into
a digital word representing angular position. R to D (Resolver to Digital) is
sometimes used.
Reed Switch
A sealed, magnetically operated switch that, when positioned over a magnet, will
provide a signal to the controls either by contact closure or contact release.
Regeneration
The action during motor braking, in which the motor acts as a generator and
takes kinetic energy from the load, converts it to electrical energy, and returns it
to the amplifier.
Regeneration Resistance
A resistive device which purpose is to shunt excess voltage developed during a
motor being in a generation mode.
Relay Ladder Logic
This programming language expresses a program as a series of "coils" and
"contacts", simulating the operation of electromechanical relays. The resultant
program is the equivalent of a boolean equation, which is executed continuously
in a combinatorial manner. The advantage of this language is the familiarity many
electricians have with the simple operation of relays. Disadvantages include the
complexity of large, cross-connected programs, and the difficulty of expressing
such non-binary functions as motion control and analog I/O. An alternative
technique now being widely used is State Language control.
Reluctance
The characteristic of a magnetic material which resists the flow of magnetic lines
of force through it.
Repeatability
The degree to which a parameter such as position or velocity can be duplicated.
Repeatability (Bi-Directional)
The difference in the final position reached by moving away and then returning to
a common point from both plus and minus directions. The error or nonrepeatability is usually the sum of the backlash, hysteresis, and one unit of the
system resolution.
Repeatability (Uni-Directional)
The ability of a system to repeat to a desired location, approaching that location
from both plus and minus directions.
Resistance
The degree of obstacle presented by a material to the flow of electric current is
known as resistance and is measure to Ohms.
Resistance, Hot (RH)(Ohms line-to-line)
The motor's terminal resistance value specified at the hot winding temperature,
which is at the motor's maximum rated temperature.
Resolution
The smallest increment into which a parameter can be broken down. For
example, a 1000 line encoder has a resolution of 1/1000 of a revolution.
Resolver
An electromagnetic feedback device which converts angular shaft position into
analog signals. These signals can be processed in various ways, such as with an
RDC (resolver-to-digital converter) to produce digital position information. There
are two basic types of resolvers; transmitter and receiver. A transmitter-type is
designed for rotor primary excitation and stator secondary outputs. Position is
determined by the ratio of the sine output amplitude to cosine output amplitude. A
receiver-type is designed for stator primary excitations and rotor secondary
output. Position is determined by the phase shift between the rotor output signal
and one of the primary excitation signals.
Resonance
Oscillatory behavior caused by mechanical limitations.
Restart torque
The maximum friction load, at a particular inertial load, that can be applied to the
shaft of a synchronous motor without causing it to lose synchronism when
accelerating to a constant speed from standstill.
RFI
Radio Frequency Interference.
Ringing
Oscillation of a system following a sudden change in state.
RISC
reduced instruction set computer/chip
Rise Time
The time required for a signal to rise from 10% of its final value to 90% of its final
value.
RMI (Remote Method Invocation)
A Java-based messaging protocol standard that can interrogate, change and
control one or more CTC controllers.
RMI (Remote Method Invocation)
A Java-based messaging protocol standard that can interrogate, change and
control one or more CTC controllers.
RMS (Root Mean Square)
The square root of the average of the squares of the values of a periodic quantity
taken throughout one complete period.
RMS Current - Root Mean Square
Current
In an intermittent duty cycle application, the RMS current is equal to the value of
steady state current which would produce the equivalent motor heating over a
period of time.
RMS Torque - Root Mean Square
Torque.
In an intermittent duty cycle application, the RMS torque is equal to the value of
steady state torque which would produce the equivalent motor heating over a
period of time.
Robot
A re-programmable multifunctional manupulator designed to mvoe material,
parts, tools, or specialized devices through variable programmed motions for the
performance of a variety of tasks.
Robot Control
A computer-based motion control device to control the servo-axis motion of a
robot.
ROM (Read Only Memory)
A memory chip that can be read but not altered.
Rotor
The moving part of the motor, consisting of the shaft and magnets. These
magnets are analogous to the field winding of a brush-type DC motor.
Router
A device for intelligently switching traffic between multiple networks, based on a
stored configuration and sophisticated routing software. Routers can switch traffic
based on either MAC-level (OSI Layer 2) or Protocol-level (OSI Layer 3)
addresses. These capabilities allow routers to perform security functions, as well
as adaptive network reconfiguration
RPM
Revolutions Per Minute
RPM (Revolutions Per
Minute)
The number of times per minute the shaft of the motor (machine) rotates. This is
a function of design and the power supply.
RS232C
A popular protocol for transmitting digital data over two lines in a bit-serial format.
RS232C specifies signal levels, data formats, maximum transmission
distances...etc.
RS485
A high speed, differential method of serial communication that allows for multiple
network "drop", or "nodes", to share the transmit and receive lines. rS485 is
commonly used in automation due to its extended range (4000 ft) and its
outstanding noise immunity.
RTU
Remote terminal unit
S
Samarium Cobalt
A type of rare-earth permanent magnet material.
SCADA
supervisory control and data acquisition [system]
SCR (Silicon Controlled Rectifier)
A semiconductor device which can be used to control motor power. Common
SCR controls are used to control adjustable speeds of a PMDC motors. Motors
designed for operation from the form factor produced by a full wave SCR control
are called SCR rated motors and are usually rated at 90 Volts(DC) and 180
Volts(DC).
Secondary Winding
Winding which is not connected to the power source, but which carries current
induced in it through its magnetic linkage with the primary winding.
Serial Port
A digital data communications port configured with a minimum number of signal
lines. This is achieved by passing binary information signals as a timed series of
"1"s and "0"s on a signal line.
Servo
A system consisting of several devices which continuously monitor actual
information (position, velocity), compares those values to desired outcome and
makes necessary corrections to minimize that difference.
Servo Amplifiers/Servo Drive
An electronic device which produces the winding current for a servo motor. The
amplifier converts a low level control signal into a high voltage and current levels
top produce torque in the motor.
Servo Motor
A DC motor in which position is achieved by precise linear or duty cycle control of
motor current and accurate monitoring of an external feedback device. Converts
electrical energy (winding current)into mechanical energy (torque).
Servo System
An automatic feedback control system for mechanical motion in which the
controlled or output quantity is position, velocity, or acceleration. Servo systems
are closed loop systems.
Settling time
The time required for a parameter to stop oscillating or ringing and reach its final
value.
Shock loading
A load that produces extremely high peak torques for very short durations. This
type of load is associated with conveyorized grinding, crushing and separation
processes.
Shunt Regulator
A device located in a servo amplifier for controlling the regenerative energy that is
generated when a motor brakes. This device dissipates the kinetic energy as
heat.
Shunt Resistor
A device located in a servo amplifier for controlling regenerative energy generted
when braking a motor. This device dissipates or "dumps" the kinetic energy as
heat.
Single Point Ground
The common connection point for signal grounds in a control wiring environment.
Single-turn Encoder
A single-turn encoder cannot distinguish between one turn and the next without
the aid of external circuitry. See also Multi-turn encoder.
Slew
In motion control, the portion of a move made at a constant non-zero velocity.
Slew Speed
The maximum velocity at which an encoder will be required to perform.
SMDS
Switched Multi-Megabit Data System
SMTP (Simple Mail Transfer Protocol)
A standard protocol for transporting email messages between servers.
SNA
system network architecture
Sniffer
A "sniffer" is a program that is surreptitiously installed on a computer within a
local network. The purpose of the program is to put the computer's network
interface into "promiscuous mode" ,so that it will receive every packet that
appears on the network. The sniffer creates a logfile on the computer's disk
containing this network data, which may later be retrieved by the perpetrator and
analyzed for information such as passwords or proprietary information
SNMP
Simple Network Management Protocol
SOAP (Simple Object Access Protocol)
Based around XML, SOAP is a lightweight, cross-platform protocol for data
exchange and control in a distributed environment. It can interrogate, change and
control one or more CTC controllers.
Speed
Describes the linear or rotational velocity of a motor or other object in motion.
Speed Regulation
For a speed control systems, speed regulation is the variation in actual speed
expressed as a percentage of set speed.
SPS (Steps-Per-Second)
A measure of velocity used with stepping motors.
SQL (Structured Query Language)
A standard interactive and programming language for getting information from
and updating a database via queries. Queries take the form of a standard
command language that lets you select, insert, update, or find out the location of
data.
Stall Torque
The amount of torque developed with voltage applied and shaft locked, or not
rotating. Also known as locked-rotor torque.
Starting Current
Amount of current drawn at the instant a motor is energized. Same as locked
rotor current.
Starting Torque
The torque of twisting force delivered by a motor at the instant it is energized.
Starting torque is often higher than rated running or full load torque.
State Languages
State languages are used primarily for expressing sequences of operations in the
real world. Typically, these languages divide a program into a series of "states,"
or steps - the program executes wholly in one step until some transition event
occurs which causes the program to move to a new step. As such, it represents a
reasonable way to express the operation of machinery, which itself must transit
through a series of mechanical states as it operates. Practical state languages
used for automation must allow multitasking, whereby multiple threads of steps
may be in operation at once.
Static Load
A load that is applied to a bearing while stationery.
Stator
The non-moving part of the motor. Specifically, it is the iron core with the wire
winding in it that is pressed into the frame shell. The winding pattern determines
the voltage constant of the motor.
Stator
The non-rotating part of a magnetic structure. In a motor the stator usually
contains the mounting surface, bearings, and non-rotating windings or permanent
magnets.
Step angle
The angular distance the shaft rotates upon receipt of a single step command.
Stepper Motor
Motor that receives electric pulses to command a move in discrete angular
increments (steps). Through appropriate drive circuitry, controlling the rate and
quantity of pulses will control the motor's velocity and position.
Stiffness
The ability to resist movement induced by an applied torque. Stiffness is often
specified as a torque displacement curve, indicating the amount a motor shaft will
rotate upon application of a known external force when stopped.
Straightness Of Travel
The deviation from ideal straight-line motion of a linear motion assembly. This
can result from rotation around any of three perpendicular axes or translation in
two linear axes.
Synchronism
A motor rotating at a speed corresponding correctly to the applied step pulse
frequency is said to be in synchronism. Load torques in excess of the motor's
capacity (rated torque) will cause a loss of synchronism. This condition is not
damaging to a step motor.
Synchronous
The condition under which a motor runs at a speed which is directly related to the
frequency of the power applied and is not dependent on other variables.
SSi
Xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
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T
Tachometer
A device attached to a moving shaft that generates a voltage signal directly
proportional to rotational speed. Tachometers are typically attached to the ouput
shaft of DC or AC variable-speed motor requiring close speed regulation. The
tachometer feeds its signal to a control which adjusts its output to the DC or AC
motor accordingly.
Tachsyn
A brushless, electromagnetic feedback transducer which produces an analog
velocity feedback signal and commutation signals for a brushless servo motor.
The tachsyn is functionally equivalent to hall sensors and a tachometer.
TCP/IP
transmission control protocol/internet protocol
TEFC
Totally Enclosed Fan Colled. A type of motor enclosure.
TENV - Totally Enclosed Non-Ventilated
Acronym describing a type of motor enclosure, which has no outside air going
into it. It is cooled only by convection to the frame, which is usually finned.
Thermal protection
A thermal sensing device mounted to the motor to protect it from overheating.
This is accomplished by disconnecting the motor phases from the drive in an over
temperature condition.
Thermal resistance (Rth) (°C/watt)
An indication of how effectively a unit rids itself of heat; a measure of temperature
rise per watts lost. In Pacific Scientific literature, it is the specified value from the
motor windings to the ambient, under locked rotor conditions.
Thermal time constant (tth) (minutes)
The time required for a motor to attain 63.2% of its final temperature for a fixed
power input.
Thermistor (Thermally Sensitive Resistor)
A semiconductor used to measure temperature that can be attached to an alarm
or meter to detect motor overheating.
Thermocouple (Thermal Detection DEvice)
A temperature-detecting device made of two dissimilar metals, which generates a
voltage as a function of temperature. Thermocouples can be attached to a meter
or alarm to detect overheating of motor windings or bearings.
Thermostat
A temperature sensitive pilot duty device mounted on the interior of the motor to
protect it from overheating.
Thrust
Measurement of linear force. The total force required to move the load, including
gravity, friction, and acceleration.
Torque
A measure of angular force which produces rotational motion. This force is
defined by a linear force multiplied by a radius; e.g. lb-in. Torque is an important
parameter of any motion control system. Formula: Torque (lb-ft.) = 5,250 x
HP/RPM
Torque Constant (KT = lb-ft./A)
An expression of the relationship between input current and output torque. For
each ampere of current, a fixed amount of torque is produced.
Torque Ripple
The cyclical variation of generated torque given by the products of motor angular
velocity and number of commutator segments.
Torque-to-inertia ratio
Defined as the motor's holding torque divided by the inertia of its rotor. The higher
the ratio, the higher a motor's maximum acceleration capability will be.
Transducer
Any device that translates a physical parameter into an electrical parameter.
Tachometers and encoders are examples of transducers.
Transfer Function
The ratio of the Laplace transforms of a system output signal and a system input
signal.
Transformer
A device which converts electrical power (alternating current) to electrical power
of a different voltage. In this device, both primary and secondary windings are
usually stationary and are wound on a common magnetic core.
Trapezoidal Profile
A motion profile in which the velocity vs. time profile resembles a trapezoid.
Characterized by constant acceleration, constant velocity, and constant
deceleration.
TTL (Transistor-Transistor-Logic)
Refers to a family of integrated circuit devices used for control. Typically using
5VDC logic threshold.
U
UL
Underwriters Laboratory
Ultimate Winding Temperature
The maximum allowable temperature of a motor winding for a given class
insulation.
Unipolar driver
A step motor driver configuration that uses a unipolar power supply and is
capable of driving phase current in only one direction. The motor phase winding
must be center tapped (6 or 8 lead) to operate with a unipolar driver. The center
tap is used instead of providing the current reversal of a bipolar driver
V
Variable Frequency drives
An electronic device used to control the speed of a standard AC induction motor.
The device controls the speed by varying the frequency of the winding current
used to drive the motor.
Vector Control
A method of obtaining servo type performance from an AC motor by controlling
two components of motor current.
Velocity
The change in position as a function of time. Velocity has both a magnitude and
sign.
Viscous Damping (KDV) (lb-in./kRPM)
Inherent losses are present in all motors which result in lower torque delivered at
the output shaft than developed at the rotor. Losses which are proportional to
speed (i.e. speed dependent terms such as windage, friction, eddy current) are
related through the motor's "viscous damping" constant, measured as the slope
of the damping curve.
Voltage
Difference in electrical potential between two points.
Voltage constant (KE) (V/kRPM peak, line-to-line)
May also be termed back-EMF constant. When a motor is operated, it generates
a voltage proportional to speed, but opposing the applied voltage. The shape of
the voltage waveform depends upon the specific motor design. For example, in a
brushless motor, the waveshape may be trapezoidal or sinusoidal in nature. All
Pacific Scientific brushless motor designs have a sinusoidal voltage constant. For
a sine waveform, the voltage constant can be measured from line-to-neutral or
line-to-line and expressed as a peak value or "RMS" value.
Voltage constant (or Back EMF Constant)
A number representing the relationship between Back EMF voltage and angular
velocity. Typically expressed as V/KRPM.
Voltage Drop
Loss encountered across a circuit impedance from power source to applicable
point (motor) caused by the resistance in conductor. Voltage drop across a
resistor takes the form of heat released into the air at the point of resistance.
VPN
Virtual Private Network, a term typically used to refer to the creation of a
protected network channel over public networking conduits such as the Internet.
Technologies used to create VPNs include L2TP and PPTP.
VPN
Virtual Private Network, a term typically used to refer to the creation of a
protected network channel over public networking conduits such as the Internet.
Technologies used to create VPNs include L2TP and PPTP.
W
WAN
Wide-area network
Watt
One horsepower equals 746 watts.
Watts Loss
The amount of lost power due to inefficiencies of a device.
Weight
Force of gravity acting on a body. Determined by multiplying the mass of the
object by the acceleration due to gravity.
X
XML (Extensible Markup Language)
A World Wide Web Consortium -(W3C) endorsed standard for document markup
and data exchange. Highly user-configurable means of defining data and its
structure.
Y
No terms available.
Z
No terms available