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Hardware Requirements

To use this package you need one or more powercubes www.schunk-modular-robotics.com. Alternatively you can use a simulated version without any hardware, see schunk_bringup_sim.

Software Requirements

The installation is tested for Ubuntu 14.04 using ROS indigo. If you discover problems installing them on other platforms, please tell us.

ROS API

The schunk_powercube_chain package provides a configurable node for operating a chain of powercube modules.

schunk_powercube_chain

The schunk_powercube_chain node takes in brics_actuator/JointVelocities messages and sends this directly to the hardware. The chain can be initialized, stopped or recovered via services.

Subscribed Topics

joint_group_velocity_controller/command (std_msgs/Float64MultiArray)

• Receives velocity commands.

joint_group_position_controller/command (std_msgs/Float64MultiArray)

• Receives position commands (Not implemented yet).

Published Topics

/joint_states (sensor_msgs/JointState)

• Joint state information for all modules in chain.

joint_trajectory_controller/state (control_msgs/JointTrajectoryControllerState)

• Controller state information for all modules in chain.

driver/current_operationmode (std_msgs/String)

• Current operation mode for chain.

/diagnostics (diagnostic_msgs/DiagnosticArray)

• Diagnostics information about chain.

Services

driver/init (std_srvs/Trigger)

• Initializes the node and connects to the hardware.

driver/stop (std_srvs/Trigger)

• Stops immediately all hardware movements.

driver/recover (std_srvs/Trigger)

• Recovers the hardware after an emergency stop.

driver/set_operation_mode (cob_srvs/SetString)

• Sets the operation mode for the node. Currently only "velocity" mode implemented.

Parameters

can_module (string, default: Required)

• Can module specifier, e.g. PCAN, ESD

can_device (string, default: Required)

• Device address of can module, e.g. /dev/can0, /dev/pcan2,...

can_baudrate (int, default: Required)

• Baudrate of can module, e.g. 1000, 500,...

module_ids (list of ints, default: Required)

• Modul IDs of the powercubes, e.g. [10,11,12,13,...]

force_use_movevel (bool, default: false)

• Forces using the M5API moveVel command instead of moveStep.

joint_names (list of strings, default: Required)

• List of joint names corresponding to urdf description, e.g. [arm_1_joint, arm_2_joint, arm_3_joint,...]

max_accelerations (list of doubles, default: Required)

• List of maximal accelerations for the modules in rad/sec^2, e.g. [0.8,0.8,0.8,...]

horizon (double, default: 0.05)

• Horizon in seconds for commanding moveStep. E.g. 0.1 commands a step size of 0.1 seconds into the future.

frequency (double, default: 10 Hz)

• Controller frequency.

min_publish_duration (double, default: Required)

• Minimum duration of publishing joint states if no command is received, otherwise for each received command one joint state message is published.

/robot_description (urdf model, default: Required)

• Urdf model of the robot, including the joints and links describing the chain of powercubes

Usage/Examples

This package is not intended to be used directly, but with the corresponding launch and yaml files from e.g. schunk_bringup in the schunk_robots stack. For starting only the lwa use

roslaunch schunk_bringup lwa_solo.launch

For including the lwa in your overall launch file use

<include file="$(find schunk_bringup)/components/lwa.launch" />

All hardware configuration is done in the schunk_hardware_config package. A sample parameter file in "schunk_hardware_config/lwa/config/lwa.yaml" could look like this

can_module: PCAN
can_device: /dev/pcan1
can_baudrate: 1000
modul_ids: [1,2,3,4,5,6,7]
joint_names: [arm_1_joint, arm_2_joint, arm_3_joint, arm_4_joint, arm_5_joint, arm_6_joint, arm_7_joint]
max_accelerations: [0.8,0.8,0.8,0.8,0.8,0.8,0.8]
frequency: 68
OperationMode: position
ptp_vel: 0.4 # rad/sec
ptp_acc: 0.1 # rad/sec^2
max_error: 0.2 # rad