When to use MotionMagicTorqueCurrentFOC vs MotionMagicVoltage?

[CYO]

I see that one uses amps as the feed forward value, whereas the other uses voltage, but I’m unclear what the differences are between the two otherwise.

[amb]

It also changes whether amps or volts are used for closed-loop control so you would have to tune that separately.

I would only use voltage control unless you really wanted to keep a constant force, since internally current control still relies on voltage control.

[daltzsmith]

MotionMagicVoltage is the traditional motion magic routine that closely follows the behavior of the v5 API. It’s similar to a Trapezoidal Motion Profile with Jerk and Acceleration constraints and some other optimizations.

MotionMagicTorqueCurrentFOC (requires a Phoenix Pro license) utilizes the benefits of FOC (more efficient, easier to tune) to achieve the set point more efficiently (less power needed to achieve a given target).

As for which one you should use, that really depends on a few factors.

• If you already have licensed devices, then you should probably use MotionMagicTorqueCurrentFOC
• If your mechanism scales well with torque applied (arms are a good example) then MotionMagicTorqueCurrentFOC will likely be easier to tune.

I also advise taking a look at Choosing Output Type in our documentation.

[CYO]

@daltzsmith

utilizes the benefits of FOC

MotionMagicVoltage provides the option EnableFOC. Is that not the same?

[daltzsmith]

I see the confusion.

Both are FOC but Torque Current controls Torque. This can be useful when you want to fine tune your acceleration without a slew rate limiter.

[Oblarg]

@daltzsmith

This can be useful when you want to fine tune your acceleration without a slew rate limiter.

It can also simplify the dynamics of the system so that there are fewer control gains to determine (and they can be determined more accurately). YMMV though - it’s still early and we don’t have many direct comparisons of the same system controlled different ways.

[CYO]

Thanks everyone for your repsonses!

Semi-related question, why does MotionMagicVoltage have OverrideBrakeDurNeutral whereas MotionMagicTorqueCurrentFOC has OverrideCoastDurNeutral? Why don’t both have both?