Contents

PI ROS Driver

PI ROS Driver

This package contains the ROS Driver for Hexapods from Physik Intrumente (PI).

This includes a controller manager as standalone node as well as launch files and configurations as easy starting point for your ROS application.

The package is using ROS control and builds on the known interfaces and paradigms.

Maintainer

Physik Instrumente (PI) GmbH & Co. KG

License

Copyright 2020 Physik Instrumente (PI) GmbH & Co. KG

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at
- http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

Github - Resource

Find at Github - PI ROS Treiber

Supported Models

H-811.I2
The ROS driver works for all PI Hexapod types. For simulation and offline use currently only a model of the H-811.i2 is available. Models for other hexapod types on request.
Please also note that the “PIHexapodemulator” – a virtual machine to simulate complete hexapod systems - can also be used in combination with the PI ROS driver.

Setup

Due to the library used for connecting to the PI Hexapod, this Driver can only be used on x86 architectures.

A number of general ROS tutorials can be found at the ROS Wiki. To install ROS Melodic for Ubuntu 18.04 follow the instructions given at Melodic for Ubuntu. For other ROS Distributions or target platforms, see ROS Wiki.

To create a workspace, refer to this tutorial or follow these abbreviated instructions for ROS Melodic:

    source /opt/ros/melodic/setup.bash
    mkdir -p ~/catkin_ws/src
    cd ~/catkin_ws/
    catkin_make
    source devel/setup.bash

Clone this repository, install dependencies and build the workspace:

    cd src
    # clone this repository: git clone ...
    cd ~/catkin_ws/
    rosdep install --from-paths src --ignore-src -r -y
    catkin_make

Now, the driver is ready to be used. For example, run the following command to start a simulated hexapod and an interactive marker to control it:

    roslaunch pi_hexapod_control interactive_marker.launch sim:=true

Documentation

This package is documented with Doxygen (apt install doxygen) . Create the documentation by executing doxygen Doxyfile in the package root directory. HTML documentation will be generated in the doc/html directory and can be easily accessed by opening doc/html/index.html in a web browser.

Usage

1. Launch files

A number of launch files are included to serve as example on how to configure and use the Driver.

hexapod_common_control.launch provides an elaborate example on how to connect to a hexapod. It can be used as standalone configuration to interact with hardware or a simulated hexapod. Also, it can be easily included in other launch files, allowing for easy configuration due to using smart default arguments. For example, interactive_marker.launch and rqt_gui.launch build onto hexapod_common_control.launch resulting in easy to understand configurations. It is advised to not use the interactive marker and the RQT gui at the same time.

interactive_marker.launch provides an interactive marker server to control a hexapod via RViz. For more information on its functionality, see Interactive Marker Node.

rqt_gui.launch provides an different interface to control a hexapod. A precofigured RQT perspective with a costum control interface is launched. If you expirience problems launching this RQT perspective, have a lock at the README provided with the pi_hexapod_gui package for more details.

2. Controller Manager Node

This node provides a controller manager and hardware interface to interact with a PI Hexapod. The driver can connect to PI Hexapod Hardware via TCP/IP or serial connection. Also, the hexapod can be simulated without requiring a connection to hardware.

3. Parameters:

Exactly one of using_tcp_ip_connection or using_rs232_connection needs to be set to true, determining the connection type.

If TCP/IP is choosen, the string hexapod_ip needs to be set. Additionally, the integer hexapod_port can be set, its default is 50000.

Currently not aviable

If serial connection is choosen, the integers rs232_port_nr and baudrate need to be specified.

is_sim can be set to true to use a simulated hexapod instead of a connection to a real one. Its default value is false.

auto_referencing allows to start referencing the hexapod on startup without the need to call the referencing action.

prefer_stop_over_halt allows to define the hardware behavior in case of a unexpected shutdown. Setting this boolean to true results in the more strict STP command word being used to stop the Hexapod instead of a HLT command. The parameters default value is false.

hardware_interface/controller_rate: positive double providing the main control loop rate in Hz, default=1000

hardware_interface/joints and hardware_interface/visual_joints need to be set. The hardware_interface/ parameters are set via the provided cfg/hexapod_controllers.yaml.

3.1. Actions:

referencing of type pi_hexapod_msgs::ReferencingAction: Allows to manually start the referencing of the hexapods axes.

4. Interactive Marker Node

This nodes provides an interactive marker server allowing the user to control the hexapod from RViz.

4.1. Parameters:

Direct node parameter: rate (default=10): Command publishing rate autostart_publishing_commands (default=false): interactive marker starts sending commands to JointGroupPosController directly after startup, if set to true topic_ns (default="pi\_interactive\_marker"): namespace in which to current marker pose is published

Parameter found in Hexapod configuration YAML: interactive_marker/control_scale (default=1): scales the size of control elements interactive_marker/base_frame (default="zero_link"): Frame name of the zero position frame of the hexapod

x/lower_limit, ''{{{x/upper_limit, y/lower_limit, y/upper_limit, z/lower_limit, z/upper_limit, u/lower_limit, u/upper_limit, v/lower_limit, v/upper_limit, w/lower_limit, w/upper_limit: defining movement limits

interactive_marker/scale/x, interactive_marker/scale/y, interactive_marker/scale/z, interactive_marker/position/x, interactive_marker/position/y, interactive_marker/position/z, interactive_marker/orientation/w, interactive_marker/orientation/x, interactive_marker/orientation/y, interactive_marker/orientation/z, interactive_marker/color/r, interactive_marker/color/g, interactive_marker/color/b, interactive_marker/color/a: defining the optics of the interactive marker

4.2. Publisher:

pose of type geometry_msgs::PoseStamped: Publishes the current pose of the interactive marker.

command of std_msgs::Float64MultiArray: Publishes JointGroupPositionController command, if set to active via startup parameter, service call or context menu in RViz.

4.3. Subcriber:

joint_states of type sensor_msgs::JointState: Requires current joint states of the hexapod.

4.4. Services:

Services can also be activated via the context menu in RViz accessed via right clicking the interactive marker.

activate_command_publishing of type std_srvs::SetBool: De-/activates command publishing.

set_to_zero of type std_srvs::Empty: Resets marker position to zero.

set_to_current of type std_srvs::Empty: Sets marker to current hexapod position.

send_single_command of type std_srvs::Empty: Send a single command message to the command topic.

Software Architecture

The packages builds onto ROS Control and provides an abstraction of PI Hexapods by implementing hardware_interface::RobotHW and a Controller Manager as standalone node. JointStateInterface and PositionJointInterface are provided to be used with common ROS Controllers or to develop costum ones.

The user can interact with the Hexapod through Controllers and tooling building onto them. There are also direct interaction options with the controller, see Controller Manager Node for details.

Contact us/Technical support

For questions about this package or ROS-Industrial in general, please contact the developers.

Contact Physik Instrumente (PI) GmbH & Co. KG