Simulation example using Falcon internal PID control?

[prensing]

I am working on trying to implement simulation for our past year’s robot. Right now, I am trying to get a simple arm working. I can get it working in terms of visualising and some simple control, but not using the “same” code as we used on the robot.

For the arm, we used a TrapezoidalSubsytem. It is driven by Falcon500 motors, and we used the PID control in Position mode, within the Falcon/TalonFX to actually handle controlling the arm. When I try to do that in the simulation, the motor does not get any input. That is, the “internal” control is not doing anything.

Does anyone have a working example of a simulation which used internal controller PID control? Falcon and NEO would be appreciated (we NEOs elsewhere). Can it be done, with out completely re-writing (faking) the internal PID controller?

[Joe_Ross]

Have you looked at this?

[prensing]

Thanks. I had seen the drivetrain simulation, but not this one. However, unless I am missing something, that so called “PhysicsSim” has nothing to do with what is in the “real” robot code. The real robot control will do drive to a position under PID within the Falcon, but (unless I am misreading it), the simulation just ramps the motors up to some really fast value in equal steps.

I was hoping there was something already written, but I guess we will have to create a simulation with pure WPILib classes.

[jdao]

Is this closer to what you’re looking for?

Team 4201 2023 Season Documentation

Team 4201 is thrilled to share our 2023 robot, Gridlock, with the FIRST community! We’ve put a lot of hard work into both our CAD and code this season, and we are excited to release our work to the public. Our code highlights include: Trajectory following with PathPlanner and 4 different auto paths State Machine to define and transition between different scoring, intaking, and stowed states Limelight Pipelines to identify and adjust our chassis towards game pieces in auto Superstructure, LED,…

[prensing]

Thank you!!

It seems to actually do the PID in the simulation. My error was I was using “motor.get()” to get the speed. Switching to “motor.getMotorOutputVoltage()” works.

[bhall-ctre]

I think a better example of using our simulation APIs with WPILib is our Phoenix 6 Motion Magic example. We also cover a lot more information about integrating our API with physics simulators like WPILib’s sim classes in our Phoenix 6 docs. The APIs are slightly different compared to Phoenix 5 (namely with the new Orientation field), but overall the same principles apply.

In the old Phoenix 5 example linked here previously, we just wrote a very simple function that used the motor output voltage to ramp towards a proportion of the max possible velocity. It doesn’t just ramp to a really fast value because eventually PID will output a lower voltage, causing it to ramp back down to a slower velocity.

In the new Phoenix 6 example, we replaced all that math with more realistic physics simulation provided by WPILib’s DCMotorSim, just as team 4201’s code linked here does. But the principle is still the same: pass in the motor’s output voltage, and get back the new position and velocity to apply to the motor.