Robotics Stack Exchange is a question and answer site for professional robotic engineers, hobbyists, researchers and students. It only takes a minute to sign up.
Sign up to join this community
So I am working with a UR10 manipulator which doesn't have a direct torque interface. However, it provides torque/velocity/position feedback for each joint as well as position/velocity interfaces for joint control.
I have a feeling the answer is "yes", but I've been having trouble finding examples and comments on the feasibility of this approach.
Thanks!
If you're trying to do torque control, then you'll probably get best results if you could work with joint accelerations, because:
$$ \tau = I \alpha \\ $$
Where $\tau$ is joint torque, $I$ is the moment of inertia, and $\alpha$ is the joint angular acceleration. It's a linear relationship and should be pretty straightforward to control with a PID controller.
You don't have an acceleration input for your joint, though. What you have is a speed input for your joint. SO, what you could do is to setup a PID controller with torque error as your input, joint acceleration reference as your output, and then perform a numeric integration of the output to get a speed reference. This would look like:
$$ \tau_{\mbox{err}} = \tau_{\mbox{ref}} - \tau_{\mbox{fbk}} \\ e_P = \tau_{\mbox{err}} \\ e_I = e_I + e_P*\Delta t \\ e_D = \frac{e_P - e_{P_{\mbox{prev}}}}{\Delta t} \\ e_{P_{\mbox{prev}}} = e_P \\ a_{\mbox{ref}} = (K_P e_P) + (K_I e_I) + (K_D e_D) \\ v_{\mbox{ref}} = v_{\mbox{ref}} + a_{\mbox{ref}} * \Delta t \\ $$
