EML 2023 Motor Control Lecture 3 Feedback Sensor

EML 2023 – Motor Control Lecture 3 – Feedback Sensor Optical Encoder

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

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

Servo Motor Control means of angle measurement – optical encoder • • incremental absolute – potentiometer – resolver rotary encoder linear encoder EML 2023 Department of Mechanical and Aerospace Engineering 4

Incremental Optical Encoder • this disk has 12 slots (30º resolutio • typical incremental encoders have 2500 counts per revolution (0. 144º resolution) ($298. 74 each at Mc. Master-Carr) EML 2023 Department of Mechanical and Aerospace Engineering 5

Incremental Optical Encoder you can count pulses, but which way is it rotating? EML 2023 Department of Mechanical and Aerospace Engineering 6

Incremental Optical Encoder EML 2023 Department of Mechanical and Aerospace Engineering 7

Incremental Optical Encoder quadrature: - there are 4 n ‘events’ per one revolution of the disk - the resolution can in effect be four times the number of slots EML 2023 Department of Mechanical and Aerospace Engineering 8

Incremental Optical Encoder note: many encoders will have an index that will pulse once per revolution EML 2023 Department of Mechanical and Aerospace Engineering 9

Honeywell / Clarostat 600128 CN 1 Allied Electronics part # 753 -0059 cost: $41. 67 EML 2023 Department of Mechanical and Aerospace Engineering 10

Incremental Optical Encoder problem: - you start up the device - where are you when you start? EML 2023 Department of Mechanical and Aerospace Engineering 11

Absolute Optical Encoder BEI brand encoder $455 EML 2023 Department of Mechanical and Aerospace Engineering 12

Homing Switch • for an incremental optical encoder, we need to add a switch to set the homing position EML 2023 Department of Mechanical and Aerospace Engineering 13

Limit Switches • If there is a limited range of motion, then limit switches must also be added. • homing switches are wired to and monitored by the control computer • limit switches are wired so that they immediately shut off the power to the motor if they are pressed EML 2023 Department of Mechanical and Aerospace Engineering 14

motor with gear reducer flex coupling optical encoder homing switch limit switch EML 2023 Department of Mechanical and Aerospace Engineering 15

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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? desired position analog speed signal current Computer and DAQ Motor Driver Motor digital direction signal Encoder sensed actual position EML 2023 Department of Mechanical and Aerospace Engineering 22