EML 2023 – Motor Control Lecture 4 – DAQ and Motor Controller

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

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NI USB-6009

EML 2023Department of Mechanical and Aerospace Engineering 7

Interface to Computer

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cost: $41.67

Honeywell / Clarostat 600128CN1Allied Electronics part # 753-0059

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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

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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

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from power s

upply

to motor

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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

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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