Accuracy of cartesian velocity control

Hi!

I am using the topic "/j2s6s300_driver/in/cartesian_velocity" to control my arm but I found that the accuracy was not satisfactory. So I wrote a .cpp script to make the arm do periodic translation movements to verify the accuracy of the controller. I set velocity along y-axis as 0.04m/s or -0.04m/s. And duration=5s which means the end-effector should move 20cm along y-axis. However, I observed that the end of the arm move less than 20cm(approximately 16-17cm). I need high accuracy of the cartesian velocity, so is it better for me to compute joint velocity from desired cartesian velocity using the Jacobian matrix. Thank you! I post the code I used for your information.

The start pose was set like this rosrun kinova_demo pose_action_client.py -v j2s6s300 mq -- 0.0 0.30 0.20 0.707 -0.707 0 0

int main(int argc, char **argv)
{

  ros::init(argc, argv, "jacoTraj");
  ros::NodeHandle n;
  ros::Publisher chatter_pub = n.advertise<kinova_msgs::PoseVelocity>("/j2n6s300_driver/in/cartesian_velocity", 1000);

  ros::Rate loop_rate(100);

  int cnt = 0;
  double dt = loop_rate.expectedCycleTime().toSec();
  double duration=5.0;

  while (n.ok()) {
    while(cnt<duration/dt){

      kinova_msgs::PoseVelocity arm_twist_cmd;
      arm_twist_cmd.twist_linear_x  = 0.;
      arm_twist_cmd.twist_linear_y  = 0.04;
      arm_twist_cmd.twist_linear_z  = 0;
      arm_twist_cmd.twist_angular_x = 0.;
      arm_twist_cmd.twist_angular_y = 0.;
      arm_twist_cmd.twist_angular_z = 0.;

      chatter_pub.publish(arm_twist_cmd);
      ros::spinOnce();
      loop_rate.sleep();
      ++cnt;
    }

    cnt = 0;
    while (cnt<duration/dt) {
      Vector9d pva;
      pva = traj_r.position_plan(dt*cnt);
      // std::cout<<desired_vel_<<std::endl;
      kinova_msgs::PoseVelocity arm_twist_cmd;
      arm_twist_cmd.twist_linear_x  = 0.;
      arm_twist_cmd.twist_linear_y  = -0.04;
      arm_twist_cmd.twist_linear_z  = 0.;
      arm_twist_cmd.twist_angular_x = 0.;
      arm_twist_cmd.twist_angular_y = 0.;
      arm_twist_cmd.twist_angular_z = 0.;

      chatter_pub.publish(arm_twist_cmd);
      ros::spinOnce();
      loop_rate.sleep();
      ++cnt;
    }
    cnt = 0;
  }
  return 0;
}

Kinovarobotics / kinova-ros

Accuracy of cartesian velocity control #395