ROS2 controllers necessary for KUKA robots
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The controllers in this repository can be divided into three categories.
These controllers update the command interfaces of a hardware cyclically.
The joint impedance controller listens on the ~/command topic and updates the stiffness and damping interfaces of the hardware accordingly.
The command must be of std_msgs::Float64MultiArray type and must contain the values for all configured joints. The order of the values should match the stifness_1, damping_1, stiffness_2, ... pattern. The controller only processes the commands received on this topic, when it is in active state.
Example cli command to set damping to 0.7 and stiffness to 100 for all joints of a 6 DOF robot:
ros2 topic pub /joint_group_impedance_controller/commands std_msgs/msg/Float64MultiArray "{data: [100, 0.7, 100, 0.7, 100, 0.7, 100, 0.7, 100, 0.7, 100, 0.7]}" --once
Required parameters:
joints[string_array]: Names of joints used by the controller
This package is available in the ros2_controllers repo, however the JointGroupPositionController was not ported to humble, at the time of writing only a draft PR exists for it. To add this functionality, the contents of the PR were copied here.
The effort_controllers/JointGroupEffortController is a command forwarding controller for torque command interfaces. It accepts torque input on the ~/command topic and updates the configured torque command interfaces without checking for limits.
Required parameters:
joints[string_array]: Names of joints used by the controller
The effort_controllers/JointGroupPositionController implements a PID controller: it accepts position input and calculates the needed torques according to the PID parameters for every controlled joint
Required parameters:
joints[string_array]: Names of joints used by the controllergains/<joint_name>/p[double]: Proportional term of the controller for joint_namegains/<joint_name>/i[double]: Integral term of the controller for joint_namegains/<joint_name>/d[double]: Derivative term of the controller for joint_name
Broadcasters receive the state interfaces of a hardware and publish it to a ROS2 topic.
The FRIStateBroadcaster publishes the actual state of FRI to the ~/fri_state topic, using the custom FRIState message.
Required parameters: None
The EventBroadcaster publishes server state change events as integers (enum values) on the ~/hardware_event topic. The enum values are equivalent with the following events:
- 2: Start command was accepted by the robot controller
- 3: External control started
- 4: External control stopped (by user)
- 5: Control mode switch was successful (only relevant for drivers, where control mode can be changed in active state)
- 6: External control stopped by an error (Error message is only available in the hardware interface)
Required parameters: None
Hardware interfaces do not support parameters that can be changed in runtime. To provide this behaviour, configuration controllers can be used, which update specific command interfaces of a hardware, that are exported as a workaround instead of parameters.
The ControlModeHandler can update the control_mode command interface of a hardware. It listens on the ~/control_mode topic and makes control mode changes possible without having to reactivate the driver.
The control mode is defined as an enum in the kuka_drivers_core package, the subscription therefore is of an unsigned integer type.
Required parameters: None
The receive_multiplier parameter of FRI defines the answer rate factor (ratio of receiving states and sending commands). This is a parameter of the hardware interface, which can be modified in connected state, when control is not active. To support changing this parameter after startup, the FRIConfigurationController implements a service named ~/set_receive_multiplier. Sending a request containing the desired integer value of the receive_multiplier updates the parameter of the hardware interface.
Required parameters: None