Velocity - Position Controller

[csal3]

I am trying to use the velocity controller on my 7 DOF robotic arm, however when starting the Gazebo simulation there is a drift in position and so the joints of the robot are not standing still even though I am not giving any velocity commands. When using the effort interface with the position controller it works fine (when setting the appropriate PID gains), however I need to give velocity commands not position. Is there a way where I can use both velocity and position controllers, and use the position controller when I need the velocity to be 0? Or can I add the PID controller with the velocity controller? Is there any other solutions or do I need to write my own plugin? How does the joint_mode_interface work? Thanks

[littlejohnyang]

I actually want to be able to set both position and velocity at the same time. For example a robot arm with multiple joints, I want to be able to reach a position at a specific time. So all joints maybe varying speed on the way. I failed to see this implementation at joint_trajectory_controller in ros_controllers. Either I have to directly send message to driver or is there any way to do it in ROS at the moment?

joint_mode_interface looks like it's just allowing switching between position and velocity control mode.