[wpimath] fully discretized ElevatorFF and ArmFF

[narmstro2020]

So in a similar setup with SimpleMotorFeedforward I've discretized the Elevator and the Arm.

Here is a summary of changes

1. deprecated existing calculate methods and created 2 overloads using the units class and discretized state-space (the arm uses a different setup so only the methods exist)
2. Rewrote/reorganized the derivations for the calculate methods in Simple and Elevator.
3. Added appropriate items to protos and structs for new Elevator and Arm setup.
4. Cleaned up units in the Java docs for constructors and methods.
5. Further documentation/comment cleanup.
6. A MutableMeasure field has been added that handles the output of the calculate methods without recreating a Measure object each time its called giving the GC a break.

Left to do

1. The C++ version. I'm working on that now, but wanted some feedback first
   EDIT: DONE

Would be nice, maybe? Looking for feedback.

1. Make static factories for creation of FF's and make the constructors private for better ergonomic usage. These factories would use the units class. SimpleFF would need one each for angular and one for linear.
2. Use the units class throughout all of the FF's
3. rename SimpleMotorFeedforward to SimpleFeedforward
4. Put the A_d and B_d as private final fields precalculated during construction so the calculate isn't wasting time creating them on every call.

[narmstro2020]

@calcmogul It looks like our friend the ArmSimulationTest is back again.

[narmstro2020]

How do I fix the pregenerated files check? I cannot seem to find the error in the logs for the check.

[narmstro2020]

/format

[narmstro2020]

/format

[sciencewhiz]

How do I fix the pregenerated files check? I cannot seem to find the error in the logs for the check.

You shouldn't be modifying generated files directly, in your case
wpimath/src/generated/main/java/edu/wpi/first/math/proto/Controller.java. Instead, modify the corresponding .proto file https://github.com/wpilibsuite/allwpilib/blob/main/wpimath/src/main/proto/controller.proto

[narmstro2020]

How do I fix the pregenerated files check? I cannot seem to find the error in the logs for the check.

You shouldn't be modifying generated files directly, in your case wpimath/src/generated/main/java/edu/wpi/first/math/proto/Controller.java. Instead, modify the corresponding .proto file https://github.com/wpilibsuite/allwpilib/blob/main/wpimath/src/main/proto/controller.proto

So don't modify Controller, modify controller.proto?

Revert Controller.java back to previous?

[narmstro2020]

@sciencewhiz. Reverted back to original Controller.java and updated controller.proto, but I'm still getting a failure

[sciencewhiz]

/pregen

[narmstro2020]

/format

[narmstro2020]

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[calcmogul]

Given how many times this derivation is duplicated, it may be better to move a copy to wpimath/algorithms.md and reference the section heading in all the places that derivation is applicable.

[narmstro2020]

Given how many times this derivation is duplicated, it may be better to move a copy to wpimath/algorithms.md and reference the section heading in all the places that derivation is applicable.

Agreed. I would like to finish the cleanup in the code first before moving it if that is alright with you?

[narmstro2020]

/format

[narmstro2020]

@calcmogul how's this look before I move it to the algorithms.md file?

[calcmogul]

There's like five copies, so idk. It'll be easier to review once it's deduplicated.

[narmstro2020]

There's like five copies, so idk. It'll be easier to review once it's deduplicated.

Okay no problem. I'll get started on that.

[narmstro2020]

And I have a first draft for algorithms.md

[narmstro2020]

/format

[narmstro2020]

@calcmogul Anything left to do/check on this one.