Servo Motor Control

EML 2023 Department of Mechanical and Aerospace Engineering Design Problem You are to design an automated goalie for an air hockey table. The goalie can be 1 inch wide. Tasks –determine puck location –position blocker 2

EML 2023 Department of Mechanical and Aerospace Engineering Concepts You are to design an automated goalie for an air hockey table. The goalie can be 1 inch wide. Tasks –determine puck location camera placed above table –position blocker 3

EML 2023 Department of Mechanical and Aerospace Engineering Concepts You are to design an automated goalie for an air hockey table. The goalie can be 1 inch wide. Tasks –determine puck location camera placed above table –position blocker linear motion of blocker piece using belt and pulleys linear motion of blocker using screw linear motion of blocker using slider crank mechanism rotational motion of blocker piece 4

EML 2023 Department of Mechanical and Aerospace Engineering Concepts You are to design an automated goalie for an air hockey table. The goalie can be 1 inch wide. Tasks –determine puck location camera placed above table –position blocker linear motion of blocker piece using belt and pulleys linear motion of blocker using screw linear motion of blocker using slider crank mechanism rotational motion of blocker piece 5

EML 2023 Department of Mechanical and Aerospace Engineering Concepts You are to design an automated goalie for an air hockey table. The goalie can be 1 inch wide. Tasks –determine puck location camera placed above table –position blocker linear motion of blocker piece using belt and pulleys linear motion of blocker using screw linear motion of blocker using slider crank mechanism rotational motion of blocker piece 6

EML 2023 Department of Mechanical and Aerospace Engineering Concepts You are to design an automated goalie for an air hockey table. The goalie can be 1 inch wide. Tasks –determine puck location camera placed above table –position blocker linear motion of blocker piece using belt and pulleys linear motion of blocker using screw linear motion of blocker using slider crank mechanism rotational motion of blocker piece 7

EML 2023 Department of Mechanical and Aerospace Engineering Concept Selection list the pro’s and con’s of each design formulate concept evaluation table 8

EML 2023 Department of Mechanical and Aerospace Engineering how does the computer cause the motor to turn? How does this work? desired steering angle motor gear reducer how is the motor connected to the steering shaft? how does the computer know the current steering angle? 9

EML 2023 Department of Mechanical and Aerospace Engineering DC Motor a typical DC motor can rotate at a top speed of 2600 rpm (43⅓ rev/sec) gearing is used which slows the speed of the output shaft, but increases the torque gear train worm gear drive epicyclic gear train 10

worm gear drive 11 epicyclic gear train gear train

EML 2023 Department of Mechanical and Aerospace Engineering how does the computer cause the motor to turn? How does this work? desired steering angle motor gear reducer how is the motor connected to the steering shaft? how does the computer know the current steering angle? 12

EML 2023 Department of Mechanical and Aerospace Engineering Motor and Gear Box how is the motor connected to ground? how is the motor connected to the steering shaft? 13

EML 2023 Department of Mechanical and Aerospace Engineering Motor and Gear Box 14

EML 2023 Department of Mechanical and Aerospace Engineering motor with gear reducer flex coupling 15

EML 2023 Department of Mechanical and Aerospace Engineering how does the computer cause the motor to turn? How does this work? desired steering angle motor gear reducer how is the motor connected to the steering shaft? how does the computer know the current steering angle? 16

EML 2023 Department of Mechanical and Aerospace Engineering Servo Motor Control select means of angle measurement –optical encoder incremental absolute –potentiometer –resolver how does the computer know the current steering angle? 17

EML 2023 Department of Mechanical and Aerospace Engineering Incremental Optical Encoder this disk has 12 slots (30º resolution) typical incremental encoders have up to 2540 counts per revolution (0.142º resolution) ($ each at McMaster-Carr) 18

EML 2023 Department of Mechanical and Aerospace Engineering Incremental Optical Encoder 19

EML 2023 Department of Mechanical and Aerospace Engineering you can count pulses, but which way is it rotating? Incremental Optical Encoder 20

EML 2023 Department of Mechanical and Aerospace Engineering an encoder will typically also have an index that will ‘blink’ once each revolution Incremental Optical Encoder 21

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 22

EML 2023 Department of Mechanical and Aerospace Engineering note:many encoders will have an index that will pulse once per revolution Incremental Optical Encoder 23

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 25

EML 2023 Department of Mechanical and Aerospace Engineering Absolute Optical Encoder BEI brand encoder BEI brand encoder $455 26

EML 2023 Department of Mechanical and Aerospace Engineering Homing and Limit Protection for an incremental optical encoder, we need to add a switch to set the homing position we also need to have limit switches 27

EML 2023 Department of Mechanical and Aerospace Engineering optical encoder motor with gear reducer flex coupling limit switchhoming switch 28

EML 2023 Department of Mechanical and Aerospace Engineering how does the computer cause the motor to turn? How does this work? desired steering angle motor gear reducer how is the motor connected to the steering shaft? how does the computer know the current steering angle? incremental optical encoder with homing switch to initialize position gear reducer and flex couplings (if needed) computer controls the current going to the motor 29

EML 2023 Department of Mechanical and Aerospace Engineering How does the computer control the motor? control the current (via the voltage) 30

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computer controls the current going to the motor Summary of Closed-Loop Control desired steering angle compared to current steering angle motor gear reducer gear reducer and flex couplings (if needed) connect motor to steering shaft incremental optical encoder (with homing switch to initialize position) feeds back current motor position 37

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