Danfei

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About Danfei

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    Stanford University
  1. Danfei

    External Force/Wrench Feedback

    Kind of related to this: What is in the field "endpoint_force_command" of the messages in the topic: /robot/limb/right/interaction_controller/state ? I expected to see directly my commands when I send a desired force to the interaction_controller, but that is not the case. Are they computed from \tau of the joints? Do you subtract gravity? Thanks --Roberto
  2. Hi Emmanuel, as a workaround I got close to the desired functionality by replicating part of the trajectory interface. Basically I compute a joint space trajectory to follow a set of Cartesian way points and interpolate the impedance parameters between them. Then, I command the joint configurations while synchronously publishing the dynamically changing impedance values in /robot/limb/right/interaction_control_command . This is right now "open loop" in a sense that I do not check for the execution of the trajectory and the current state on the plan, but just periodically send a new joint pose. Emmanuel, when you say trajectory tracking, do you mean TRAJECTORY_MODE in JointCommand messages or using the joint trajectory action server? I didn't try specifying a full trajectory (joint pose, velocity and acceleration) but it would be nice to be able to do it, too. It would be of course much easier if the motion_controller on the Sawyer machine would do the interpolation of impedance parameters (passed as parameters of the waypoints), but that would involve changing the "firmware" on Rethink's side... Regards, Roberto
  3. Hi, we are trying to make our Sawyer to execute Cartesian trajectories with dynamically changing interaction parameters (impedance), e.g. the waypoints are defined as 6D poses with associated impedance parameters. As first attempt we tried to use the motion interface to execute the Cartesian trajectory. However, in this interface the interaction parameters are constant (a property of the trajectory) and cannot be defined per waypoint. We tried to "hack" it by publishing our own InteractionControlCommand's during the trajectory execution but the node "motion_controller" on the Sawyer computer periodically publishes the parameters defined in the trajectory and the messages clash. Did someone succeed on implementing a similar functionality? --Roberto
  4. Danfei

    Sawyer SDK 5.2 is Now Available

    Hi, why is the simulator restricted to Ubuntu 16.04 + Kinetic? I adapted the code to compile in 14.04 + Indigo and tried the pick and place demo; it works. I'm wondering if we will encounter some limitations / errors in the future. Could you please list the features of 16.04 + Kinetic (and not available in 14.04 + Indigo) that are used by the simulator? --Roberto
  5. Danfei

    Change URDF at run time

    Thanks for the response! The problem is that we want to do velocity/torque control rather than path planning. This requires a real-time collision handler similar to the built-in one.
  6. Danfei

    Change URDF at run time

    Hi guys, we are trying to update robot URDF with external obstacles in real time for collision checking. Is there a way to overwrite existing collision avoidance state? Thanks!