UR3 breaking/wobbling problem

[HTugal]

Hi,
In order to control robot, I publish the ur_driver/joint_speed based on some calculations and the robot subscribes it, yet robot occasionally breaks for a really short period of time and continues to operate normally. I am not sure whether it actually breaks or not but the smooth movements interrupted like a breaking/wobbling behaviour. Frequency of this breaking behaviour looks random, couldn't find any relationship with anything and running out of options..

I wonder whether anybody has ever come cross such behaviour in UR3 or not ?

[happygaoxiao]

I have also come cross this behavior. There are some zero value of joint speed as issuse #139

[HTugal]

Hi,
I thought that might be due to package loss/drop within the network communication, yet same behaviours appear even if I use a port switch, here is the first three joints ref and actual velocities: similar with #139. The peaks are the where robot shows jerky movements .. (the reference is smooth)

This is how I publish (within a loop) the /joint_speed:

` ros::Publisher arm_pub = nh.advertise<trajectory_msgs::JointTrajectory>("ur_driver/joint_speed",10);
trajectory_msgs::JointTrajectory g;

// When to start the trajectory:
g.header.stamp = ros::Time::now();
// First, the joint names, which apply to all waypoints
g.joint_names.push_back("shoulder_pan_joint");
g.joint_names.push_back("shoulder_lift_joint");
g.joint_names.push_back("elbow_joint");
g.joint_names.push_back("wrist_1_joint");
g.joint_names.push_back("wrist_2_joint");
g.joint_names.push_back("wrist_3_joint");

           g.points.resize(1);
           //------ Update Joint's velocity
           int ind = 0;
           g.points[ind].velocities.resize(6);
          // g.points[ind].accelerations.resize(6);
           for (size_t j = 0; j< 6; ++j)
               {
               // Velocities and accelerations
               g.points[ind].velocities[j] = Jtarget_vel(j,0);
            //   g.points[ind].accelerations[j] = Jtarget_ac(j,0);
               }
           //----- To be reached x second after starting along the trajectory
         //  g.points[ind].time_from_start = ros::Duration(DeltaT); // DeltaT

           arm_pub.publish(g);

`
The problem might be related to the joints' acceleration, yet not sure..

[gavanderhoorn]

Even though #139 was reported later, I believe it is a similar enough issue to suggest we continue trying to diagnose it there, and close this one.

I see you've already commented on #139 as well @HTugal.