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

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 Servo Motor Control means of angle measurement –optical encoder incremental absolute –potentiometer –resolver 4 rotary encoderlinear encoder

EML 2023 Department of Mechanical and Aerospace Engineering Incremental Optical Encoder this disk has 12 slots (30º resolution) typical incremental encoders have 2500 counts per revolution (0.144º resolution) ($ each at McMaster-Carr) 5

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

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

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

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

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 problem:- you start up the device - where are you when you start? Incremental Optical Encoder 11

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

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

EML 2023 Department of Mechanical and Aerospace Engineering 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 14

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

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