servo motor control demonstration. eml 2023 department of mechanical and aerospace engineering motor...
TRANSCRIPT
Servo Motor Control
Demonstration
EML 2023Department of Mechanical and Aerospace Engineering
motor withgear reducer
flex coupling
incremental optical
encoder
limit switchhoming switch
computer controls the current going to the
motor
computer controls the current going to the
motor
Closed-Loop Control
desired steering anglecompared to current steering angle
motorgear reducer
gear reducer and flex couplings (if needed)
connect motor to steering shaft
incremental optical encoder (with homing
switch to initialize position) feeds back
current motor position
How does the computer do this?
How does the computer ‘read’ the encoder information?
EML 2023Department of Mechanical and Aerospace Engineering
Computer Interface
• To command the motor:– The computer must be able to generate an analog
voltage signal that is somehow interpreted by the motor.
• To ‘read’ the encoder:– The computer must be able to read the +5V and 0V
pulses coming from the two light detectors on the optical encoder.
EML 2023Department of Mechanical and Aerospace Engineering
Interface to Computer
• We will use a National Instruments USB-6009 data acquisition (DAQ) device
• specs– USB interface to PC– 8 channels of analog input, 0-5V– 2 channels of analog output 0-5V
5 mA each– 12 channels of digital input/outputs
0 or 5V, (8.5 mA for outputs)– 1 counter
EML 2023Department of Mechanical and Aerospace Engineering
NI USB-6009
EML 2023Department of Mechanical and Aerospace Engineering
Interface to Computer
EML 2023Department of Mechanical and Aerospace Engineering
cost: $41.67
Honeywell / Clarostat 600128CN1Allied Electronics part # 753-0059
EML 2023Department of Mechanical and Aerospace Engineering
Computer Interface
• Let’s start with digital inputs to interface to the optical encoder.
notice that there are four wires
+5V power
ground
channel A
channel B
channels A & B will be either 0V or 5V depending on whether that light detector detects light through a slit or not
+5V power
ground
channel A
channel B
EML 2023Department of Mechanical and Aerospace Engineering
Encoder Demo Program
computer controls the current going to the
motor
computer controls the current going to the
motor
Closed-Loop Control
desired steering anglecompared to current steering angle
motorgear reducer
gear reducer and flex couplings (if needed)
connect motor to steering shaft
incremental optical encoder (with homing
switch to initialize position) feeds back
current motor position
How does the computer do this?
EML 2023Department of Mechanical and Aerospace Engineering
Computer Interface to Motor
• To control the motor:– the computer must be able to generate an analog
voltage signal– however, the typical analog voltage signal that a
computer generates does not have sufficient current to power the motor
– an amplifier is used• a power supply provides 24V (7.5 amp max for our case) to
the amp• the computer generates an analog voltage in the range of
-5V to +5V; 0V means the motor is to stop ; -5V means the motor is to turn at a maximum speed CCW ; +5V means the motor is to turn at a maximum speed CW
EML 2023Department of Mechanical and Aerospace Engineering
Interface to Computer
from 24V power supply
to motor
emergency stop
EML 2023Department of Mechanical and Aerospace Engineering
Issue with USB-6009 & Amp
The analog command signal to the amp must be from -5V to +5V.
A negative voltage causes the motor to turn in the opposite direction.
The USB DAQ can only output from 0 to +5V.
How can we reverse the direction of the motor?
EML 2023Department of Mechanical and Aerospace Engineering
from 24V power supply
to motor
emergency stop
When we want the motor to go in the other direction, switch these two wires.
EML 2023Department of Mechanical and Aerospace Engineering
Change motor direction
To go CW, set this digital output pin to TRUE (+5V).
To go CCW, set this digital output pin to FALSE (0V).
EML 2023Department of Mechanical and Aerospace Engineering
Interface to Computer
EML 2023Department of Mechanical and Aerospace Engineering
Interface to Computer
EML 2023Department of Mechanical and Aerospace Engineering
Homing Switch
to input pin on USB DAQ
+5V
0V
EML 2023Department of Mechanical and Aerospace Engineering
Interface to Computer
0V from USB-6009
+5V from USB-6009
computer controls the current going to the
motor
computer controls the current going to the
motor
desired steering anglecompared to current steering angle
gear reducer and flex couplings (if needed)
connect motor to steering shaft
incremental optical encoder (with homing
switch to initialize position) feeds back
current motor position
USB connection
analogsignal
2 digitalsignals
USB connection
digitalsignal
digitalsignal
input power
homing switch
E stopswitch
EML 2023Department of Mechanical and Aerospace Engineering
Design Project
• If you decide to use a servo motor in your design:– include an optical encoder for motor position feedback– include a homing switch to initialize your position– include E-stop switches as needed