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EML 2023 – Motor Control
Lecture 4 – DAQ and Motor Controller
EML 2023Department of Mechanical and Aerospace Engineering 2
Closed Loop Control
Motor Driver
desired position current
Computer and DAQ
Motor
analog speed signal
digital direction signal
Encoder
sensed actual position
EML 2023Department of Mechanical and Aerospace Engineering 3
Let’s answer 3 questions.
1. How is the motor held in place and how is it connected to the shaft that it is to rotate?
2. How does the encoder work and how is it physically connected to the motor?
3. How do the DAQ and motor driver work?
Motor Driver
desired position
currentComputer and
DAQMotor
analog speed signal
digital direction signal
Encoder
sensed actual position
EML 2023Department of Mechanical and Aerospace Engineering 5
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 6
NI USB-6009
EML 2023Department of Mechanical and Aerospace Engineering 7
Interface to Computer
EML 2023Department of Mechanical and Aerospace Engineering 8
cost: $41.67
Honeywell / Clarostat 600128CN1Allied Electronics part # 753-0059
EML 2023Department of Mechanical and Aerospace Engineering 9
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 13
Computer Interface to Motor
• To control the motor:– we have to control the current going to the motor (via the voltage)– however, the typical analog voltage signal that a computer generates
from the DAQ 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 DAQ generates an analog voltage in the range of
-0 to +5V; 0V means the motor is to stop ; +5V means the motor is to turn at a maximum speed
• a digital signal will give the desired direction (0 V, CCW, 5 V CW)
* also called a ‘motor driver’ or ‘speed controller’
Motor Driver
desired position
currentComputer and
DAQMotor
analog speed signal
digital direction signal
Encoder
sensed actual position
Motor Driver
desired position
currentComputer and
DAQMotor
analog speed signal
digital direction signal
Encoder
sensed actual position
EML 2023Department of Mechanical and Aerospace Engineering 15
from power s
upply
to motor
EML 2023Department of Mechanical and Aerospace Engineering 17
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).
Homing Switch
to input pin on USB DAQ
+5V
0V
EML 2023Department of Mechanical and Aerospace Engineering 19
Interface to Computer
0V from USB-6009
+5V from USB-6009
Motor Driver
desired position
currentComputer and
DAQMotor
analog speed signal
digital direction signal
Encoder
sensed actual position
USB
Motor Driver
desired position
currentComputer and
DAQMotor
analog speed signal
digital direction signal
Encoder
sensed actual position
USB
Motor Driver
desired position
currentComputer and
DAQMotor
analog speed signal
digital direction signal
Encoder
sensed actual position
USBdigital direction signal
analog speed signal
ground
Motor Driver
desired position
currentComputer and
DAQMotor
analog speed signal
digital direction signal
Encoder
sensed actual position
USB
24
vo
lt su
pp
ly
PWM
sign
al to
mot
or
Motor Driver
desired position
currentComputer and
DAQMotor
analog speed signal
digital direction signal
Encoder
sensed actual position
USB
5 volt, ground, channel A, channel B
EML 2023Department of Mechanical and Aerospace Engineering 25
Let’s answer 3 questions.
1. How is the motor held in place and how is it connected to the shaft that it is to rotate?
2. How does the encoder work and how is it physically connected to the motor?
3. How do the DAQ and motor driver work?
Motor Driver
desired position
currentComputer and
DAQMotor
analog speed signal
digital direction signal
Encoder
sensed actual position
EML 2023Department of Mechanical and Aerospace Engineering
Design Project
• For each motor in your design:– include an optical encoder for motor position feedback– include a homing switch to initialize your position– include limit switches as needed– mount the motor driver
• For the project:– mount the DAQ
EML 2023Department of Mechanical and Aerospace Engineering
EML 2023Department of Mechanical and Aerospace Engineering
EML 2023Department of Mechanical and Aerospace Engineering
EML 2023Department of Mechanical and Aerospace Engineering
