Feature Inquiry: Hard Cartesian End-Effector Velocity Limiting without Modifying Joint Limits

[Sreelakshmi1S]

Hi,

I am looking for a way to explicitly set the linear speed of the end-effector (Cartesian task-space) for a trajectory.

I want to know if an option already exists—or if one can be added—where I can simply input a target end-effector speed parameter.

I am explicitly trying to avoid workarounds like manually adjusting/downscaling joint speed limits, altering the time dilation factor globally, or changing timesteps. Modifying joint limits does not guarantee a precise Cartesian speed across different robot configurations and slows down movements unnecessarily.

Is there an existing, direct parameter to set end-effector speed that I might have missed? If not, can this be considered as an official feature request for a future release?

Thank you for your help!

[balakumar-s]

1. Are you trying to limit the end-effector velocity so that the robot will not exceed a specific value across the trajectory? [inequality constraint]

2. Do you want to maintain a specific end-effector velocity for the full trajectory? [equality constraint]

[Sreelakshmi1S]

To clarify, My goal is for the end-effector to cruise at a specific target speed for the main portion of the trajectory.

As per my understanding, because the trajectory includes starting from a complete standstill and stopping exactly at the goal, a pure equality constraint across the entire trajectory would cause solver failures due to impossible acceleration demands at the boundary conditions.

What I want is setting a maximum velocity limit that will naturally force the robot to cruise flatly at that target speed for the main part of the path, while still allowing for realistic acceleration and deceleration at the start and goal.

So, the requirement is closer to an inequality constraint.

[balakumar-s]

My goal is for the end-effector to cruise at a specific target speed for the main portion of the trajectory

Adding an inequality constraint will only guarantee that the end-effector does not exceed the target speed. It does not guarantee that the end-effector will maintain that speed during any portion of the trajectory.

Is this because your robot has some emergency stop if the robot exceeds a target tool speed?

This can be implemented as a custom cost function using the kinematic Jacobian and joint velocities.

[Sreelakshmi1S]

Yes, this is exactly what i want.

I want to control the end effector (gripper) speed so that I can understand at which speed the object falls from the gripper.
As you just suggested about implementing it as a custom cost function using the kinematic Jacobian and joint velocities.

Could you maybe provide documentation on how to do this specifically?