Grijper Documentation

Table of Contents

• Command-line tools
  • Grijper.launch
• ROS Grijper API
  • gripper_console
    • Commands
    • Usage
    • topics ROS topics
  • gripper_controller
    • Usage
    • topics ROS topics
  • gripper_actuator
    • Usage
    • ROS topics
  • phidget_reader
    • Usage
    • ROS topics
  • rviz_gripper
    • Usage
    • ROS topics
  • rviz_object
    • Usage
    • ROS topics
• Grijper

Grijper: Collection of nodes controlling a gripper

A ROS based set of nodes to controll a rebotic hand with a infrared distance sensor.

• Homepage: http://ros.org/wiki/Grijper

Grijper

Controlling a robotic hand

https://github.com/svanschooten/Grijper

Grijper is a package containing nodes that are used to control a motorised robotic hand, henceforth called the 'gripper'.

This is done by reading and evaluating a sensor and it's values using the phidget in the phidget_reader node. These are compared to set threshold values to decide if the gripper should be opened or closed. This is done in the controller. Commands are then sent to the actuator which controlls the motor powering the gripper. This actuator node then publishes the motor state.

This state is picked up by an rviz node that visualises and controls the gripper model in rviz. The state is given as a float between 0.0 and 1.0. 0.0 indicating the gripper is completely open and 1.0 indicates the gripper has been closed. Another rviz node listens to the phidget sensor values and visualises a cyllinder mimicking the position of the oject relative to the gripper.

---

Command-line tools

The Grijper package can also be built by launching the Grijper.launch file. It will encapsule the console in the current console, enabling control but hiding all reduntant information from the other nodes.

Grijper.launch

Description of what this script/file does.

Usage

$ roslaunch Grijper Grijper.launch

back to top

---

ROS Grijper API

Because of the independent and standardised setup of this package, Grijper only consists of communicating nodes that can run independently (though having almost to no functionality without their proper messages).

List of nodes:

• gripper_console
• gripper_controller
• gripper_actuator
• phidget_reader
• rviz_gripper
• rviz_object

back to top

---

gripper_console

gripper_console makes the system controllable by the user through console input and output.

Commands

• 'open' Opens the gripper.
• 'close' Closes the gripper.
• 'relax' Relaxes the gripper.
• 'force < target force >' Sets the target force to '< target force >' to be used in future commands.
• 'get_force' Returns the current target force.
• 'exit' Sends the shutdown signal to all nodes and shuts down.

Usage

$ rosrun Grijper gripper_console [standard ROS args]

topics ROS topics

Publishes to:

• "gripper_force": [std_msgs/Float32] The set target force at which the gripper should close.
• "command": [std_msgs/String] The command to be passed on.
• "shutdown" [std_msgs/Bool] The shutdown command.

back to top

---

gripper_controller

gripper_controller listens to the phidget and console, thus deciding and controlling the system. Published commands to the actuator.

Usage

$ rosrun Grijper gripper_controller [standard ROS args]

topics ROS topics

Publishes to:

• "gripper_control": [Grijper/command] The command to be passed on, contains a 'cmd' string and a 'force' float.

Subscribes to:

• "gripper_force": [std_msgs/Float32] The set target force at which the gripper should close.
• "command": [std_msgs/String] The command to be passed on.
• "shutdown" [std_msgs/Bool] The shutdown command.
• "phidget_value" [std_msgs/Float32] The calculated distance from the read value.

back to top

---

gripper_actuator

gripper_actuator listens to the controller and sends commands to the threemxl to acutuate the gripper and then publishes the state of the gripper

Usage

$ rosrun Grijper gripper_actuator [standard ROS args]

ROS topics

Publishes to:

• "gripper_state" [std_msgs/Float32] The state of the gripper 0 opens, 1 closes, 0.5 relax.

Subscribes to:

• "gripper_control": [Grijper/command] The command to be passed on, contains a 'cmd' string and a 'force' float.
• "shutdown" [std_msgs/Bool] The shutdown command.

back to top

---

phidget_reader

phidget_reader reads the raw value of the sensor and calculates the distance to the object out of this value

Usage

$ rosrun Grijper phidget_reader [standard ROS args]

ROS topics

Publishes to:

• "phidget_value": [std_msgs/Float32] The calculated distance from the read value.

Subscribes to:

• "shutdown" [std_msgs/Bool] The shutdown command.

back to top

---

rviz_gripper

rviz_gripper does publishes the state of the joints of the gripper to rviz

Usage

$ rosrun Grijper rviz_gripper [standard ROS args]

ROS topics

Publishes to:

• "jstates": [sensor_msgs::JointState] The calculated states of the joints.

Subscribes to:

• "gripper_state" [std_msgs/Float32] The state of the gripper 0 opens, 1 closes, 0.5 relax.
• "shutdown" [std_msgs/Bool] The shutdown command.

back to top

---

rviz_object

rviz_object listens to the distance of an object and sends a marker message to rviz to show an object at the measured distance

Usage

$ rosrun Grijper rviz_object [standard ROS args]

ROS topics

Publishes to:

• "visualization_marker": [std_msgs/Float32] A marker object send to rviz with the measured coordinates.

Subscribes to:

• "phidget_value": [std_msgs/Float32] The calculated distance from the read value.
• "shutdown" [std_msgs/Bool] The shutdown command.

back to top