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International Conference on Innovations in Electrical and Electronics Engineering (ICIEE'2012) Oct. 6-7, 2012 Dubai (UAE) Physical Implementation and Control of MultiAxis Motion Control System using LABVIEW D. K. Krishna Kumari, Arvind Kumar, Sagar Narang The basic architecture of a motion control system contains: Abstract— Multi axis motion control system plays a major role in the efficient use and cost effective applications of CNC machine tools. In this paper, an attempt has been made to control the axes motion by controlling the speed of both DC as well as Stepper motors. A PC-to-Motor interface and driver circuit board has been designed and developed for the present system. The software of the system has been developed using LabVIEW-based graphical programming language. LabVIEW provides the flexibility of integration of data acquisition software/hardware with the motion control application software for automated test and measurement applications. The control system proposed in this paper has the capability to control four axis of motion using DC motors or two axis of motion using stepper motors[1]. • A motion controller to generate set of points (the desired motion profile) and a closed loop for position or velocity feedback. • A drive or amplifier to transform the control signal from the motion controller into a higher power electrical current or voltage that is presented to the actuator. Newer "intelligent" drives can close the position and velocity loops internally, resulting in much more accurate control. • An actuator such as a hydraulic pump, air cylinder, linear actuator or electric motor for output motion. Keywords— CNC machines, LabVIEW, DC and Stepper Motors • One or more feedback sensors such as optical encoders, resolvers or Hall effect devices to return the position or velocity of the actuator to the motion controller in order to close the position or velocity control loops. • Mechanical components to transform the motion of the actuator into the desired motion, including: gears, shafting, ball screw, belts, linkages, and linear and rotational bearings. I. INTRODUCTION M OTION control is an important part of robotics and CNC machine tools. In Personal Computer (PC)-based motion control systems, the PC performs all the real-time motion control operations including feedback loops and multi-axis coordination. It also serves as a user-friendly graphical interface. Figure 1 illustrates the block diagram of a basic PC-based motion control system. The main components of the system includes a PC to develop application software, a motion controller to create the trajectories for the motors to follow but outputting a ±10 V signal for DC motors, or a step and direction pulses for stepper motors, Driver (amplifier) to take the commands from the controller and generate the current required to drive the motor, a feedback device to sense the motor position and reports the result to the controller, thereby closing the loop to the motion controller[2]. A. Speed control of DC motor In practice, the motor should rotate in a rated speed, if the speed is more than rated speed then the motor will be damaged, in order to control the speed of motor a rheostat should be connected to the field side of motor. By varying the rheostat we can control the speed of motor[3]. There are different methods of controlling the speed of the DC motor. The methods are listed below: 1. Variation of Flux or Flux Control Method Here, by decreasing the flux, the speed can be increased and vice versa. With the help of a shunt field rheostat, the flux of a DC motor can be changed by changing I sh . Since I sh is relatively small, shunt field rheostat has to carry only a small current, which means I 2sh R loss is small, so that rheostat is small in size. Fig. 1. A basic PC-based Motion Control System Motion control is widely used in the packaging, printing, textile, semiconductor production, and manufacturing industries. D.K. Krishna Kumari, Asst. Professor, Manipal Institute of Technology, Manipal University, Manipal, Karnataka, India ([email protected]) Arvind Kumar, Manipal Institute of Technology, Manipal University, Manipal, Karnataka, India,( [email protected]) Sagar Narang,, Manipal Institute of Technology, Manipal University, Manipal, Karnataka, India,( [email protected]) Fig 2 Flux control method 272 International Conference on Innovations in Electrical and Electronics Engineering (ICIEE'2012) Oct. 6-7, 2012 Dubai (UAE) 2. Armature or Rheostat Control Method A. Interface and Driver Circuit It is a method of controlling the speed of electric motors that involves varying the resistance or reactance in the armature or field circuit, used in motors that drive elevators. This method is used when speed below the no-load speed are required. Since the supply voltage is normally constant, the voltage across the armature is varied by inserting a variable rheostat in series with the armature circuit. The armature speed is decreased when the controller resistance is increased and voltage across the armature is decreased. For a load constant torque, speed is approximately proportional to the voltage across the armature. From the speed/armature current characteristic, it is seen that greater the resistance in the armature circuit, greater is the fall in the speed.. To implement the PC-based multi-axis motion control system, an Interface and Driver Circuit (IDC) Board has been designed and developed. The IDC board shown in figure 6, is used to connect and interface motion control motors to a PC which has the capability to drive/control four DC motors or two stepper motors using its eight digital output lines. 3. Voltage Control Method: Multiple Voltage Control: Here, the shunt field of the motor is connected permanently to a fixed exciting voltage, but the armature is supplied with different voltages by connecting it across one of the several different voltages by means of suitable switchgear. The armature speed will be approximately proportional to these different voltages. The intermediate speeds can be obtained by adjusting the shunt field regulator. Fig. 6 Photograph of IDC board B. Components used in the driver circuit The following are the components used in the driver circuit. 1. 2. 3. 4. 5. 6. 7. Motor driver IC L293D Optocoupler CNY17 Leds Transformer Capacitors Diodes Resistors Fig 4 voltage control method 2. Motor Driver IC (L293B and L293D) II. METHODOLOGY The system presented here has been implemented using PC Parallel-Port to Driver Circuit interface technique and LabVIEW (Laboratory Virtual Instrumentation Engineering Workbench) software which enhances the productivity and reduces the cost. The motion control application software is developed using LabVIEW on the PC and communicated to DC/stepper motors through parallel port and the interface and driver circuit (IDC). Figure 5 illustrates the block diagram of the proposed multi-axis motion control system which include; Windows based PC, Parallel Port Interface, Interface and Driver Circuit, Motors[4]. Fig 5 Block diagram of Multi-axis Motion Control System 273 The L293B and L293D are quadruple high-current half-H drivers. The L293B is designed to provide bidirectional drive currents of up to 1 A at voltages from 4.5 V to 36 V. The L293D is designed to provide bidirectional drive currents of up to 600-mA at voltages from 4.5 V to 36 V. Both devices are designed to drive inductive loads such as relays, solenoids, DC and bipolar stepping motors, as well as other high-current/high-voltage loads in positive-supply applications. All inputs are TTL compatible. When the enable input is high, the associated drivers are enabled and their outputs are active and inphase with their inputs. When the enable input is low, those drivers are disabled and their outputs are off and in the high-impedance state. With the proper data inputs, each pair of drivers forms a full-H (or bridge) reversible drive suitable for solenoid or motor applications. A VCC1 and VCC2 terminals are provided for the logic inputs to minimize device power dissipation. The L293B and L293D are characterized for operation from 0°C to 70°C[7]. International Conference on Innovations in Electrical and Electronics Engineering (ICIEE'2012) Oct. 6-7, 2012 Dubai (UAE) Fig 7 L293D Pin diagram Fig 8 External Structure of a Geared DC Motor 1. Optocoupler CNY17 The CNY17 consists of a pair of gallium arsenide infrared emitting diode optically coupled to a silicon NPN phototransistor. Signal information, including a DC level, can be transmitted by the device while maintaining a high degree of electrical isolation between input and output. It can be used to replace relays and transformers in many digital interface applications, as well as analog applications such as CRT modulation. The input and output of the CNY17 is shown in tables 1.[8] IV. RESULTS The speed of DC motors is controlled using variable speed motion control application software. The front panel and the diagram of the developed software for the system are shown in Figures 9 and 10 respectively[6]. TABLE 1 INPUT AND OUTPUT OF CNY17 Parameter Test condition Symbol Reverse voltage Value Unit VR 6.0 V IF 60 mA FSM 2.5 A 100 mW Forward current Surge current t ≤ 10 µs I P Power dissipation diss 70 Collector-emitter breakdown Voltage BV CEO Emitter-base breakdown Voltage BV EBO 7.0 Collector current t < 1.0 ms Power dissipation V V 50 mA IC 100 mA P diss 150 mW 3. Geared DC Motor In a geared motor, the energy output is used to turn a series of gears in an integrated gear train. There are a number of different types of gear motors, but the most common are AC (alternating current) and DC (direct current). The speed of the motor Fig 9 Front panel of 4-axis DC Motor speed control is counted in terms of rotation of the shaft per minute (RPM). Simple DC motors are restricted in terms of power and lack proper speed control. They can even run at speeds approximately close to 3,000 RPM which may be beyond the desired requirements of the user. However, using a geared motor can reduce down the RPM such as 150 and lower, hence providing more torque to the machine. Figure 8 shows details of the geared DC motor. A nut is placed near the shaft to allow the motor to be mounted on chassis of a machine. 274 International Conference on Innovations in Electrical and Electronics Engineering (ICIEE'2012) Oct. 6-7, 2012 Dubai (UAE) Fig 10. Block diagram of 4-axis DC Motor speed control Fig 11 Block diagram of 2-axis stepper motor motion control 275 International Conference on Innovations in Electrical and Electronics Engineering (ICIEE'2012) Oct. 6-7, 2012 Dubai (UAE) The two and four axis motion control system has been successfully developed and implemented using geared DC motors for each axis at 10RPM, 12V and 150mA. The front panel and block diagram of the software is shown in Figures 9, 10 and 11 respectively. In all the front panels of the developed motion control software, logic states (signals) driving the motors are represented by LEDs shown as D0 to D7. The ‘Green Color’ LEDs represent logic state “1” (ON) whereas ‘Dark Green Color’ LEDs represent logic state ‘0’ (OFF). The motion control system has been successfully demonstrated for controlling the axes positions for an angular range of 0º to 360º within an accuracy of ±0.05º. REFERENCES [1] E.Nesimi “Labview of electric circuits, machines,drives and laboratories”, E.Nesimi, Prentice hall, New Jersey 2002. [2] Remya ravindran, Arun kumar “A DC motor speed controller using Labview”, Dept. of Electronics & Telecommunication, BIT, Durg, CG, India r [3] D.P Kothari and I.J Nagrath, “Electric machines”, 3 edition, Tata McGraw Hill, New Delhi, India. [4] Saffet Ayasun, Gu¨ Ltekin Karbeyaz , DC Motor Speed Control Methods Using MATLAB/Simulink and Their Integration into Undergraduate Electric Machinery Courses” , March 2005 [5] P. Thepsatorn, A. Numsomran, V. Tipsuwanporn and T. Teanthong, “DC Motor Speed Control using Fuzzy Logic based on LabVIEW”, SICEICASE, 2006 [6] Jianying Liu, Pengju Zhang, “Real-Time DC Servo Motor Position Control by PID Controller Using Labview” Intelligent Human-Machine Systems and Cybernetics, 2009. IHMSC '09,volume 1. [6] National Instruments, “LabVIEW User Manual”, National Instruments, Jan. 1998 Edition [7] http://www.beyondlogic.org/spp/parallel.pdf. [8] Optocoupler CNY17, Datasheet; www.agilent.com/semiconductors. [9] http://zone.ni.com/devzone/cda/tut/p/id/3367 276