Hi together :)
First of all, thanks for delivering CRISP. It is a great set of controllers.
Problem Description
I use CRISP to control a RobCo Light Leo robot. To be more precise, I am using the crisp_controllers/CartesianController. To tune its parameters, I checked out the cartesian_controller.yaml. Lines 133-138 contain:
nullspace:
[...]
damping:
type: double
default_value: -1.0
description: "Damping of the nullspace controller. If negative, then 2 sqrt(stiffness) is used."
validation:
bounds<>: [-1.0, 500.0]
[...]However, the corresponding evaluation in lines 512-516 of cartesian_controller.cpp looks like this:
if (params_.nullspace.damping) {
nullspace_damping.diagonal() = params_.nullspace.damping * weights;
} else {
nullspace_damping.diagonal() = 2.0 * nullspace_stiffness.diagonal().cwiseSqrt();If I am correct, if (params_.nullspace.damping) evaluates to true for the default value of -1.0 since this is an implicit bool evaluation on a double. This can be dangerous since this will apply negative damping which contributes to oscillations and instability.
Note that for the task damping this seems to be handled properly because the arguments are checked against > 0.
Proposed fix
I cannot push my fix to the repo but it is tiny anyway. Simply, the if statement in line 512 should be changed to:
if (params_.nullspace.damping > 0) {
Hi together :)
First of all, thanks for delivering CRISP. It is a great set of controllers.
Problem Description
I use CRISP to control a RobCo Light Leo robot. To be more precise, I am using the
crisp_controllers/CartesianController. To tune its parameters, I checked out thecartesian_controller.yaml. Lines 133-138 contain:However, the corresponding evaluation in lines 512-516 of
cartesian_controller.cpplooks like this:If I am correct,
if (params_.nullspace.damping)evaluates totruefor the default value of-1.0since this is an implicitboolevaluation on adouble. This can be dangerous since this will apply negative damping which contributes to oscillations and instability.Note that for the task damping this seems to be handled properly because the arguments are checked against
> 0.Proposed fix
I cannot push my fix to the repo but it is tiny anyway. Simply, the if statement in line 512 should be changed to:
if (params_.nullspace.damping > 0) {