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The oscillation of a joint with no command and zero gains

Hi,

I have loaded my robot into Gazebo. This robot is 6 DOF. You can see the files from here. I have tuned PID parameters of ros_control for four joints. But, tuning two joints (joint 4 and flange) is not really easy. I have noticed the flange of the manipulator oscillates, when I do not command the joint. To reduce fluctuations, I set parameters of this file (denso_controllers.yaml) as follows:

joint6_position_controller:
type: effort_controllers/JointPositionController
joint: flange
pid: {p: 0.01, i: 100.0, d: 0.0, i_clamp: 0.0}

However, through such a change, the flange does not move when I command it. Another point is that when I set all PID parameters of the flange joint to zero, the oscillations are significant. I don't know how to remove such behavior.

In addition, the behavior of joint 4 is strange too. When the input is in the following range (1.5<$input$<2 and -2<$input$<-1.5) the joint moves correctly. Otherwise, the error signal oscillates and the process_value signal does not oscillate. The reason to this issue is not clear to me.

Would you please give me a hint how to do that.

To run the code easily please enter the following lines:

1) run gazebo:

roslaunch denso_gazebo denso_world.launch

2) run rqt to show the figures and commands:

roslaunch denso_control denso_rqt.launch

The distro of my ROS is indigo running on Ubuntu 14.04.

Thank you.

The oscillation of a joint with no command and zero gains

Hi,

I have loaded my robot into Gazebo. This robot is 6 DOF. You can see the files from here. I have tuned PID parameters of ros_control for four five joints. But, tuning two joints (joint joint 4 and flange) is not really easy. I have noticed the flange of the manipulator oscillates, when I do not command the joint. To reduce fluctuations, I set parameters of this file (denso_controllers.yaml) as follows:

joint6_position_controller:
type: effort_controllers/JointPositionController
joint: flange
pid: {p: 0.01, i: 100.0, d: 0.0, i_clamp: 0.0}

However, through such a change, the flange does not move when I command it. Another point is that when I set all PID parameters of the flange joint to zero, the oscillations are significant. I don't know how to remove such behavior.

In addition, the The behavior of joint 4 is strange too. When the input is in the following range (1.5<$input$<2 and -2<$input$<-1.5) the joint moves correctly. Otherwise, the error signal oscillates and the process_value signal does not oscillate. The reason to this issue is not clear to me.

Would you please give me a hint how to do that.

To run the code easily please enter the following lines:

1) run gazebo:

roslaunch denso_gazebo denso_world.launch

2) run rqt to show the figures and commands:

roslaunch denso_control denso_rqt.launch

The distro of my ROS is indigo running on Ubuntu 14.04.

Thank you.