Closed PeterBowman closed 1 year ago
Besides, ICartesianControl::pose
might no longer make sense, anymore, as movi
is now the preferred way to accept position-based targets.
Proposed control scheme:
twist
command.Similarly to movl
, we combine inputs 2 and 3 in an integral control scheme (differentiate input2-input3 and apply gain). Then, add input 1 and perform differential IK to obtain joint velocities.
Every step needs to store the expected pose (input 2 of the next iteration) resulting from input 1, expressed in terms of infinitesimal distance, added to input 3.
Tested at https://github.com/roboticslab-uc3m/kinematics-dynamics/commit/8d8dca02f56d8cff9e4af5b41063ab13b12034f1, not working as expected. Alternative solution is even worse: https://github.com/roboticslab-uc3m/kinematics-dynamics/commit/dddd23e44fadbc734170879b997554a6d6f1fa36.
Not doing. This has been superseded by CSV mode (https://github.com/roboticslab-uc3m/yarp-devices/issues/221). Also, the reason why the arm was bending down could've been that the default IVelocityControl
implementation (i.e. "velocity profile" at the firmware level instead of CSP/CSV) accelerates/decelerates prior to reaching each velocity reference. It is of course best to apply instantaneous velocities as in CSV mode, which will probably become the new default.
Cf. the ftCompensation app in which CSV is also the preferred method: https://github.com/roboticslab-uc3m/kinematics-dynamics/issues/191.
BasicCartesianControl::twist
performs open-loop velocity control, which is unsufficient if a steady, linear path is desired. Any attempts to control TEO's arms via joystick (https://github.com/roboticslab-uc3m/kinematics-dynamics/issues/173#issuecomment-493400560) will cause said arm to bend due to gravity.Position-based control (via
movi
cartesian command andyarp::dev::IPositionDirect
joint commands) does the trick (https://github.com/roboticslab-uc3m/yarp-devices/issues/231#issuecomment-575821842), but is somewhat shaky.A closed-loop setup as implemented in
movl
takes advantage of the position feedback and tries to compensate the bend-down reaction of the arm in motion. By setting an acceptable gain value, this command yields nice results (https://github.com/roboticslab-uc3m/yarp-devices/issues/221#issuecomment-575843920).So, I'd like to add position feedback in the
twist
command in case it renders beneficial.