FTC Moving 202008

Encoder Notes

Documentation and tutorials

• Lesson: Exercise: Using Encoders on PDX STEM
• [https://docs.revrobotics.com/docs/first-tech-challenge FIRST Tech Challenge - REV Documentation}
• Motor PIDF Tuning Guide
• Motor Encoder Guide
• Control Hub and Expansion Hub Firmware Update Guide
• DcMotorEx

issues with pidf

• PIDF for goBilda 5202 very slow #150
• Tuning PIDF - slow movement for small errors

Issue reported and solved

• [https://github.com/ftctechnh/ftc_app/issues/287 DC motor running too slow in RUN_USING_ENCODER run mode #287}
• Robot getting stuck with RUN_TO_POSITION
• DcMotor - Run to position not working
• Drive Straight
• Not going straight
• Straight line driving
• App Update 5.3-64b: PID vs PIDF

Firmware https://www.revrobotics.com/software/#exphubpreviousfirmware

api

• DcMotor
• DcMotor RunMode

PID

• isPIDMode
• https://stemrobotics.cs.pdx.edu/node/7268
• https://github.com/ftctechnh/ftc_app/wiki/Changing-PID-Coefficients Changing PID Coefficients]
• https://github.com/ftctechnh/ftc_app/wiki

pid api

PIDCoefficients DcMotorEx

• DcMotorEx

Code snipets

 DcMotorEx motorExLeft;
 motorExLeft = (DcMotorEx)hardwareMap.get(DcMotor.class, "left_drive”);
 PIDCoefficients pidOrig = motorExLeft.getPIDCoefficients(DcMotor.RunMode.RUN_USING_ENCODER);
 pidOrig.
 PIDCoefficients pidNew = new PIDCoefficients(NEW_P, NEW_I, NEW_D);
 motorExLeft.setPIDCoefficients(DcMotor.RunMode.RUN_USING_ENCODER, pidNew);

• getVelocity in ticks per second
• f is the tolerance

Moving the Distance

• FTC_State also ramp up motors

• Core Hex Motor
  • Output Shaft: 5mm Female Hex
  • Weight: 7 oz
  • Free Speed: 125 RPM
  • Stall Torque: 3.2 N-m
  • Stall Current: 4.4 A
  • Gear Ratio: 72:1
  • Encoder Counts per Revolution
    • At the motor - 4 counts/revolution
    • At the output - 288 counts/revolution

• 90mm Traction Wheel

 90 mm * 3.1416 = 282.7 mm / rotation = / 25.4 mm 11.13 inches / rotation
 288 couts / rotation   divided  11.13  inches / rotation   =  25.76 counts / inch
 max is 125 rev / minute   divide 60 seconds / minute = 2.08 rev /second
 2.08 rev / sec time 288 counts/  rev = 600 counts / sec   = max speed