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

EML 2023 Department of Mechanical and Aerospace Engineering Closed Loop Control 2 Motor Driver desired position current Computer and DAQ Motor analog speed signal digital direction signal Encoder sensed actual position

EML 2023 Department of Mechanical and Aerospace Engineering 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? 3 Motor Driver desired position current Computer and DAQ Motor analog speed signal digital direction signal Encoder sensed actual position

EML 2023 Department 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. USB 4

EML 2023 Department 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 5

EML 2023 Department of Mechanical and Aerospace Engineering NI USB

EML 2023 Department of Mechanical and Aerospace Engineering Interface to Computer 7

EML 2023 Department of Mechanical and Aerospace Engineering cost:$41.67 Honeywell / Clarostat CN1 Allied Electronics part #

EML 2023 Department 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 9

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+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 11

+5V power ground channel A channel B 12

EML 2023 Department of Mechanical and Aerospace Engineering 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 current Computer and DAQ Motor analog speed signal digital direction signal Encoder sensed actual position 13

14 Motor Driver desired position current Computer and DAQ Motor analog speed signal digital direction signal Encoder sensed actual position

EML 2023 Department of Mechanical and Aerospace Engineering 15 from power supply to motor

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EML 2023 Department 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). 17

Homing Switch to input pin on USB DAQ +5V 0V 18

EML 2023 Department of Mechanical and Aerospace Engineering Interface to Computer 0V from USB V from USB

Motor Driver desired position current Computer and DAQ Motor analog speed signal digital direction signal Encoder sensed actual position USB 20

Motor Driver desired position current Computer and DAQ Motor analog speed signal digital direction signal Encoder sensed actual position USB 21

Motor Driver desired position current Computer and DAQ Motor analog speed signal digital direction signal Encoder sensed actual position USB digital direction signal analog speed signal ground 22

Motor Driver desired position current Computer and DAQ Motor analog speed signal digital direction signal Encoder sensed actual position USB 24 volt supply PWM signal to motor 23

Motor Driver desired position current Computer and DAQ Motor analog speed signal digital direction signal Encoder sensed actual position USB 5 volt, ground, channel A, channel B 24

EML 2023 Department of Mechanical and Aerospace Engineering 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? 25 Motor Driver desired position current Computer and DAQ Motor analog speed signal digital direction signal Encoder sensed actual position

EML 2023 Department 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 2023 Department of Mechanical and Aerospace Engineering

EML 2023 Department of Mechanical and Aerospace Engineering

EML 2023 Department of Mechanical and Aerospace Engineering

EML 2023 Department of Mechanical and Aerospace Engineering