Download Christian Thompson_13780_Lozier_Thompson_interim_powerpoint

Stability Control System for a Propeller Powered
by a Brushless DC Motor (BLDC)
Codey Lozier
Christian Thompson
Advisor: Dr. Mohammad Saadeh
Introduction & Objectives
•
This system consists of a propeller that is powered by a BLDC motor.
•
When the BLDC is operated, the propeller will create a lift force.
•
This force (if controlled properly) will allow the BLDC to move to the horizontal axis and
maintain it there.
•
The BLDC (with the propeller) are installed at one end of a rod that is pivoting around the
shaft of an encoder.
•
Later, another BLDC can be installed on the other side of the rod and control both motors
to reach stability.
•
The BLDC motor is mainly used in applications where rotary motion for extended period of
time is needed.
•
Due to their powerful performance, BLDC motors are used in remote controlled (RC) cars,
helicopters, and planes.
EXPERIMENTAL SETUP
Components of the Design Project
•
Brushless dc motor (BLDC a2208)
•
Phidgets micro load cell
•
Phidgets Wheatstone bridge interface
•
Brushless speed controller
•
Incremental rotary encoder
•
Arduino Mega2560
Brushless DC Electric Motor A2208/12
•
Rotational speed = 1800rmp/v
•
Max efficiency current = 8~10a (>74%)
•
Weight = 36g
•
Electrical resistance = 90mΩ
•
To study the lift forces generated by the BLDC, a micro load cell is used to measure this
force.
•
First, the load cell needs to be calibrated. We used a calibration weight set to identify its
readings using small weights (10g, 20g, 50g, and 100g).
•
Once identified, the BLDC is mounted on top of the load cell to measure the lift force
generated at different operating voltages.
LIFT FORCE
•
Of the four forces of flight, we are only concerned with two:
•
Lift Force and Weight Force
• Opposing forces (act against one another)
• Just like a propeller blade an airplanes wing is shaped with one side having more
surface area (curved) than the other
LIFT FORCE CONTINUED
•
From a side view, Air on the top side of an airplane wing has to move faster over a
greater surface area to keep up with the air on the bottom.
•
According to Bernoulli's Principle, which states an increase in speed will result in an
proportional decrease in pressure:
• There must be a pressure difference between the top and bottom of the wing.
LIFT FORCE CONTINUED
•
The result in the difference in the air pressure is a net upward force called LIFT
•
The air under the wing (or in our case propeller blade) moves slower and exerts more of a
force than the air moving above the blade.
•
Since the force under the blade is greater than the force above the blade, the resulting
force is UP.
Hobbywing Brushless Speed Controller
•
Output: 30a continuous, 40a burst for 10 seconds
•
Input voltage: 5.6v-16.8v/2-4s
•
BEC (battery elimination circuit) output: 2a linear mode
•
Max speed: 210,000 rpm for 2 poles; 70,000 rpm for 6 poles; 35,000 rpm for 12
poles
•
Weight = 25g
MICRO LOAD CELL
•
A load cell is a force sensing element.
•
Strain gauges mounted in precise locations measure the deformation of the cell, thus
deforming the gauges.
•
Deformation of strain gauges results in a change in the electrical resistance.
•
Load cell is interfaced with the Phidgets Wheatstone Bridge Device to translate signal
from load cell to a weight.
Phidget Bridge
•
The single point load cell is mounted down at the two points shown
•
Force is applied in the other of the arrow on the load cell
•
The load cell measures the shearing effect on the beam
•
The Phidgetbridge allows four connections for various load cells, gauges, etc
•
The data values can be configured in a software
Incremental Rotary Encoder
•
Used to measure speed, direction,
and position of rotating shaft
•
Interfaced with the USB4 with the encoder
data acquisition device
•
Power supply voltage 5v to 12v dc
ENCODER DATA ACQUISITION DEVICE
•
Designed to measure 4 incremental
encoders
•
Interfaced with rotary encoder
•
Includes libraries for various
programming languages so users can
develop their own applications
•
Includes application demo as a
graphical user interface
ARDUINO MEGA 2560
•
Microcontroller board based on the
ATmega2560
•
Contains 54 digital I/O pins, of which
14 can be used for pulse-width
modulation
•
Will be interfaced with micro load cell,
rotary encoder, and brushless DC
motor
Current Progression
•
The experimental setup has been established. The encoder is fixed to a wooden plate
using a mounting bracket.
•
Two couplers and two rods are connected to the encoder’s shaft.
•
The load cell was calibrated using a calibration weight set.
Future Progression
April – May 2014
•
Mount the BLDC on the load cell to study the lift force generated at different operating
voltages.
•
Select a propeller that can achieve the best lift within the range of voltage used.
August – September 2014
•
Setup a control algorithm with the following components:
• The goal is to stabilize the output rod in the horizontal position
• The encoder reading serves as a good reference point. It is used as a feedback
• The driving signal is the error in encoder reading (difference between reference
and actual readings)
• This error controls the magnitude of the BLDC operating voltage
October – November 2014
•
Include a second BLDC on the other end of the rod. Repeat the control algorithm for the
new two-BLDC system.