gripper isn't working under Indigo

[ferherranz]

Hello,

I'm using youbot_manipulation under indigo. I launch move_group.launch file in combination with moveit_commander. When I execute:
use arm_1_gripper
go open

I get the following error:
[ERROR] [1437659114.273972520]: Unable to identify any set of controllers that can actuate the specified joints: [ gripper_finger_joint_l gripper_finger_joint_r ]
[ERROR] [1437659114.274016429]: Known controllers and their joints:
controller 'arm_1/arm_controller' controls joints:
arm_joint_1
arm_joint_2
arm_joint_3
arm_joint_4
arm_joint_5

[ERROR] [1437659114.274061944]: Apparently trajectory initialization failed

Any idea?
Thank you in advance!

[svenschneider]

Hello Fernando,

unfortunately, this is the "expected" behaviour (also under ROS Hydro). Let me explain the issue: MoveIt! can "plan" trajectories for the gripper (not that there is that much to plan for open/close ;) ). The problem is that the simple MoveIt! controller managers [1] expect either a ROS control_msgs/FollowJointTrajectory [2] action interface or a control_msgs/GripperCommand [3] action interface. However, neither of these is offered by the youbot_driver_ros_interface [4].

There are several ways to solve this issue:

1. Write a custom controller manager (see e.g. [5] for an overview of the current architecture).
2. Extend the youbot_driver_ros_interface to include the required interface.
3. Write an adapter node that translates FollowJointTrajectory or GripperCommand actions to the gripper's position interface [6].

In any case, you have to register the controller in the controllers.yaml configuration file [7].

Best regards
Sven

[1] https://github.com/ros-planning/moveit_plugins
[2] http://docs.ros.org/indigo/api/control_msgs/html/action/FollowJointTrajectory.html
[3] http://docs.ros.org/indigo/api/control_msgs/html/action/GripperCommand.html
[4] https://github.com/youbot/youbot_driver_ros_interface/blob/hydro-devel/src/YouBotOODLWrapper.cpp
[5] http://moveit.ros.org/wiki/Executing_Trajectories_with_MoveIt!
[6] https://github.com/youbot/youbot_driver_ros_interface/blob/hydro-devel/src/YouBotOODLWrapper.cpp#L207
[7] https://github.com/svenschneider/youbot-manipulation/blob/indigo/youbot_moveit/config/controllers.yaml

[ferherranz]

thank you for you help! I'm just starting with moveit and youbot. I'll have a a look at the links!

Best Regards

Fernando

[frederikhegger]

Dear @ferherranz,
does it work for you now?