egomo_node

xamla_egomo_node

General Information

This node runs on the Raspberry Pi on the Egomo sensor and offers a ROS-service which offers ROS-actions to asynchronously control a connected gripper. Furthermore different topics are offered in order to get information about the gripper, force torque (FT) and inertial measurement unit (IMU).

Overview

• Gripper message
• Joint state of the gripper
• Force Torque message
• Message IMU
• Send commands to IO-Board
• Action for gripper activation
• Action for setting gripper position
• Troubleshooting

Topic XamlaGripper

Publishes the state of the gripper using XamlaGripper.msg. Subscribe by typing the following in your terminal:

rostopic echo /XamlaEgomo/XamlaGripper

Published data	type
header	std_msgs/header
grip_force	float32
left_finger_force	float32
right_finger_force	float32
pos_fb	float32
uint8	state
bool	object_gripped

Topic XamlaGripperJointState

Publishes the state fo the gripper as joint state messages (JointState). Subscribe by typing the following in your terminal:

rostopic echo /joint_states

Published data	type
header	std_msgs/header
name	string[]
position	float64[]
velocity	float64[]
effort	float64[]

Topic XamlaForceTorque

Publishes sensor readings of the force torque sensor using WrenchStamped. Subscribe by typing the following in your terminal:

rostopic echo /XamlaEgomo/XamlaForceTorque

Published data	type
header	std_msgs/header
wrench	geometry_msgs/Wrench

Topic XamlaIOIMU

Publishes sensor readings of the inertial measurement unit (IMU) using AccelStamped. Subscribe by typing the following in your terminal:

rostopic echo /XamlaEgomo/XamlaIOIMU

Published data	type
header	std_msgs/header
accel	geometry_msgs/Accel

Service SendCommand

In order to send commands to the gripper this service was created (SendCommand.srv). The following commands are available:

Command	value range	description
reset	0 or 1	Resets the gripper when value is set from 1 -> 0 (falling edge)
max_speed	0-255	Controls the speed of the gripper
max_force	0-255	Controls the force of the gripper
pos_cmd	0.0-0.087	Moves the gripper to the position (in m)
out0	0 or 1	Turns on/off device at this board output (e.g. led, ir-led ord laser)
out1	0 or 1	Turns on/off device at this board output (e.g. led, ir-led ord laser)
out2	0 or 1	Turns on/off device at this board output (e.g. led, ir-led ord laser)

Notice that you should reset the gripper before use. During initialization the gripper moves. Here are two examples of valid calls of the service from the terminal.

rosservice call /XamlaEgomo/SendCommand "reset" 0
rosservice call /XamlaEgomo/SendCommand "pos_cmd" 0.05
rosservice call /XamlaEgomo/SendCommand "out0" 0

Action EgomoGripperActivate

This action can be used to activate/deactivate the gripper (EgomoGripperActivate.action). It gives feedback about whether the gripper has been activated.

Goal

name	type	description
activate	bool	true to activate gripper - false to deactivate gripper

Feedback

name	type	description
is_activated	bool	true if gripper is activated - false if gripper is deactivated

Result

name	type	description
is_activated	bool	true if gripper is activated - false if gripper is deactivated

Action EgomoGripperPos

This action can be used to send the gripper position commands (EgomoGripperPos.action). Furthermore the speed and the force can be set directly if needed. The feedback and the result contain the current position of the gripper and whether an object has been gripped.

Goal

name	type	description
goal_pos	float32	The desired position in m (e.g. 0.0 for close or 0.087 for open)
set_speed_and_force	bool	If true the given speed and the force are set directly with the position command.
speed	uint8	Speed of the gripper (0 is lowest, 255 is highest speed)
force	uint8	Force of the gripper (0 is lowest, 255 is highest force)

Feedback

name	type	description
pos_fb	float32	The current position of the gripper
object_gripped	bool	True if an object has been gripped and false otherwise

Result

type	name	description
pos_fb	float32	The current position of the gripper
object_gripped	bool	True if an object has been gripped and false otherwise

Troubleshooting FAQ

• Q1: I get the error "No device could be found!!!".
• A1: The IO-Board connected the the Raspberry Pi could not be found. Make sure that it is connected properly. Usually the IO-Board should be recognized by the Raspberry Pi as a device /dev/ttyACM0 or any other number.