ROS Noetic controller for Poppy robots

Quickstart

This software is distributed as a systme image for the Raspberry Pi so no setup is required except downloading the latest image file and flashing your SD card. Start the controller on the Raspberry Pi as follows:

ssh [email protected]
# Password is "poppy"

# Make sure your ROS_MASTER_URI variable is correctly set to your usecase:
nano ~/.bashrc

# Then, just run the controllers:
roslaunch poppy_controllers control.launch

Once the controller is started, the robot can be driven either via Moveit or by publishing on the ROS API as described hereunder.

ROS API overview

This controller implements the regular robot interface for ROS + custom services:

• The topic /joint_states publishes the current joint angles and speeds
• The action server /follow_joint_trajectory allows to control the robot by executing trajectories of type trajectory_msgs/JointTrajectory
• The service /set_compliant allows to en(dis)able the robot compliance
• The service /get_image allows to grab an image from the camera
• The service /close_gripper allows to close or open the gripper (motor m6 of the Ergo Jr)
• The parameters /gripper/angles/aperture and /gripper/angles/closure define the range of aperture of the gripper (in degrees from about -20° to +30°)
• The parameter /gripper/speed defines the opening/closing speed from 0.05 (slowest) to 1 (fastest)

Examples

Start the controller hereunder on the Raspberry Pi. Then, our your workstation, try the following:

1. Set the robot in compliance mode:

rosservice call /set_compliant "data: true" 

# The service must return a success message:
#   success: True
#   message: "Robot compliance has been enabled"

2. Plot the joint positions:

rosrun rqt_plot rqt_plot /joint_states/position[0] /joint_states/position[1] /joint_states/position[2] /joint_states/position[3] /joint_states/position[4] /joint_states/position[5]

You'll see a graph updated in real time. Manually move motors with your hands to see their evolution in real time.

3. Plan and execute trajectories with MoveIt

Use this package with poppy_ergo_jr_moveit_config in order to plan collision-free trajectories and execute them on the robot.

More examples and documentation

Please consult the Poppy documentation for further information.

Troubleshooting

Invalid Trajectory: start point deviates from current robot state more than 0.2

You're probably trying to replay a trajectory while your robot didn't reach the starting point first. Make sure you reach it with set_joint_value_target.

ABORTED: Solution found but controller failed during execution

Is your robot compliance disabled? No trajectory can be executed with compliance.

Robot makes abrupt trajectories

• If you are replaying a recorded trajectory, make you you first join its initial point before starting replay: use set_joint_value_target first before execute
• Poppy Ergo Jr's motors have a range of [-170°, +170°] = [-0.94 rad, +0.94 rad], if your trajectories don't fit this interval, you will likely have erratic movements, thus:
• keep away from U-turns (~ 180° = 3.14 rad) for each motor when recording a trajectory
• make sure your motors are not mounted backwards : set_joint_value_target([0, 0, 0, 0, 0, 0]) must bring your robot in that exact configuration.

Compatible robots and accessories

Although this ROS package can evolute as a ROS overlay to pypot and thus take control over all Poppy robots: Ergo jr, Torso, Humanoid... the current development status currently only supports Poppy Ergo Jr mounted with the Gripper or Lamp tools.

If you intend to control other Poppy robots, start by setting the right motors here.