Time-limited motion generator

[MaximilianHeckl]

Hello together,

I am currently implementing a Python-based quintic motion generator, similar to the MotionGenerator class from example_common.py. The corresponding code is attached and implemented according to the boundary conditions of the initial and final acceleration and velocity being zero. With this choice of boundary conditions, I want to prevent discontinuities at the beginning of the motion. The aim of the implementation is to introduce a motion, which is finished within a given duration. However, this code leads to the errors "joint_motion_generator_velocity_discontinuity" and "joint_motion_generator_acceleration_discontinuity" for short given durations. Is the discontinuity related to some maximum absolute velocity and acceleration values, since the acceleration curve is proven to be continuous acc. to the picture? If I provide larger durations for the motion, it succeeds.

Thank you in advance and best regards!

Max

QuinticMotionGenerator.py

[AndreasKuhner]

Hi @MaximilianHeckl ,

Is the discontinuity related to some maximum absolute velocity and acceleration values, since the acceleration curve is proven to be continuous acc. to the picture?

Yes and yes. In the backend we check that velocity, acceleration and jerk doesn't ramp up/down too fast. If you see this error, it actually means that you try to accelerate too fast. I guess it then makes sense that it works if you stretch the execution time.

You can also check out the rate limiting within this repo on how you could limit it yourself - an example would be within https://github.com/frankarobotics/libfranka/blob/main/examples/generate_joint_position_motion_external_control_loop.cpp.

Cheers,
Andreas