Motor control modes

[IvLaptev]

There are four motor control modes: position, speed (velocity), torque and compound.

In this discussion will be posted different ideas about use cases of each of them.

Ideas that will be implemented will be marked with 👍
Implemented ideas are marked with 🎉

[IvLaptev]

Position mode

Main idea: Can be used for position blocking

Example: You need to fix a part of a leg at a specific angle for some time. You can set q as a current angle and large kp and kd.

Tested: No

[IvLaptev]

Position mode

Main idea: Can be used to move leg

Example: You can change joint angle in position mode. You can set q as a current angle and large kp and kd.

Tested: Yes

[IvLaptev]

I can see two different implementations of it:

1. We can divide angle into small pieces and send every tick command that will be changing angle to this value

   For example, you want to change angle from 0 to 1 during 10 ticks.
   At the beginning, we have delta = 1 - 0 = 1
   The value by which the angle should be after next tick is q = q + delta / ticks = 0 + 1 / 10 = 0.1 \

   In the next ticks we will repeat previous steps paying attention to the real q value:
   For the second tick we get that current q is not 0.1 but 0.089. It means that our step can't be as on previous iteration.
   delta = 1 - 0.089 = 0.911
q = 0.089 + 0.911 / 9 = 0,19022
   And so on.

   That approach was tested earlier.

2. We can every tick send the same command.

   I hope that it is possible to set small enough values of kp and kd so that the angle changes smoothly on its own.

   That approach was never tested before.

[IvLaptev]

Speed mode

Main idea: Can be used to move leg with constant speed

Example: You can change linearly change joint angle in speed mode. It could be more stable than in position mode. You can set dq as a current speed (rad/s) and big enough kd.

Tested: No

[IvLaptev]

There is also important to send target q to fix joint in stable position after finishing motion.