Transcript Control system using encoder and brushless dc motors

Codey Lozier
Christian Thompson
Advisor: Dr. Mohammad Saadeh
Introduction
 Control Systems
 Stability Control System Setup
 Objectives
 Components of Stability Control System
 Current Progression
 Future Progression
Control Systems
 Goal is to modify a system
so it behaves in a desirable
way over time
 Arrows (signals) represent
vector-valued functions of
time
 Basic Control System
 Plant
 Controller
 Sensor
 r- reference input
 v- sensor output
 u- actuating signal
 d- external disturbance
 y-measure signal
 n- sensor noise
Stability Control System Setup
Stability Control System Modification
 Old Shaft
 New Shaft
Objectives
 A brushless DC motor is attached to a propeller, and
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fixed onto the end of a horizontal beam.
A shaft will be fixed onto the horizontal beam creating a
90 degree angle
The opposite end of shaft will be attached to rotary
encoder.
When the motor is energized, the propeller will produce
a lift force that will stabilize the beam
Every time the motor rises or falls the shaft connected to
the rotary encoder rotates
This “index” value will be used as an error signal
Arduino Mega 2560
 Microcontroller board based on
the ATmega2560
 Contains 16 analog input pins
 Contains 54 digital I/O pins
 14 digital I/O can be used for
PWM
 User friendly programming
environment
Brushless DC Motor (BLDC)
 Fixed on shaft coupler
 Goal is to use the propeller to
create a lift force
 Electrically commutated, does not
use brushes
 Powered using brushless speed
controller
 Commutation is induced through
PWM
Brushless DC Motor Modifications
 Original propeller could not generate enough lift force
 Had to be replaced with 8 x 4.5 carbon fiber (10g)
propeller
 New propeller generates force that can stabilize the beam
Propellers
Carbon Fiber
Weight: 10 g for each propeller
Size 8 X 4.5
Lift Force
 Of the four forces of flight,
we are only concerned with
two:
 Lift Force and Weight Force
 Opposing forces
 The airfoil of an
airplane’s wing is just
like a propeller blade
Schematic of Air Flow Through the Propeller
Y
X
Pressure Variation Along Slipstream
P2 < P1 & P3 > P4 = P1 = Patm
Lift Force Continued
 Air under the propeller blade, moves slower and exerts
more of a force than the air moving above the blade.
 Force under the blade is greater than the force above the
blade
Brushless Speed Controller
 Electronic speed controller
(ESC)
 Powers motor (17Vdc)
 Used in high power RC
systems
 Receives PWM signals from
Arduino Mega
Brushless Speed Controller
 Potentiometer can be used to change the frequency and duty
cycle of PWM
 Change in resistance increase/decreases speed of motor
Micro Load Cell
 A load cell is a force sensing
element
 Small components called strain
gauges mounted in precise
locations
 Change in electrical resistance
Image Retrieved from: http://ueidaq.wordpress.com/2013/08/02/the-twists-of-strain-gaugemeasurements-part-1/
Image Retrieved from 3133 Micro Load Cell CZL635 datasheet
Phidget Bridge
 Contains 4 Wheatstone Bridges
 USB interface ( 2 )
 Amplifies signal sent from micro load cell ( 1 )
 Demo applications are provided
 Users can develop own applications
Image Retrieved from 1046 PhidgetBridge 4-Input Product Manual
Microload Cell Calibration
 Used demo program
provided by manufacturer
 Performed several trials
 Values produce were stable
 Need to amplify signals
being sent from load cell
YUMO Rotary Encoder
 Measure change in angle, direction, and speed
 Resolution of 2000 pulses/rev
 Manufacturer provides a demo
application
 Produces a signal that represents an
“index” or angular position
 Signal for direcion a
YUMO Rotary Encoder
 Shaft is stabilized with
pillow block
 Device is fixed to table
 Encoder is interfaced
with data acquisition
device
Encoder data acquisition device
 Designed to measure 4
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incremental encoders
USB interface
Interfaced with rotary encoder
Includes application demo
Users can develop their own
applications
Image retrieved from US Digital USB4 Encoder Data Acquisition USB Device User Manual
Current Progression
 The experimental setup has been established
 Two couplers and two rods are connected to the encoder’s
shaft.
 The load cell was calibrated using a calibration weight set.
 Selected propeller for the desired lift force
 Measure lift force of BLDC using micro load cell (current)
Youtube Video
Future Progression
June - August 2014
 Setup a control algorithm with the following components:
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The goal is to stabilize the output rod in the horizontal position
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The encoder reading serves as a good reference point. It can be used as
feedback
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The driving signal is the error in encoder reading (difference between
reference and actual readings)
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This error controls the magnitude of the BLDC operating voltage
Future Progression
September-November 2014
 Include a second BLDC on the other end of the rod. Repeat the control
algorithm for the new two-BLDC motors system
 Integrate all components using a data acquisition system, and a control
algorithm in real time environment (e.g. LabVIEW)