ROS-i ABB driver - publish more than 6 variable through /joint_states

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I am basically trying to send the translational and rotational positions of the tip (total 7 float variables) from RAPID to the ROS as a ros topic

So if I understand you correctly, you are looking for a way to transmit the Cartesian pose of the TCP to the industrial_robot_client nodes?

And then in XYZ+Quaternion form, correct?

I was thinking of using the /joint_states topic's velocity and acceleration vectors to contain these variables

If possible, I would recommend not to do that: you'd be completely changing the semantics of the messages involved, which is really not a good idea (see also note 6 under JOINT_POSITION in the specification document linked below).

You have two options:

1. define a new message (TCP_POSE or something similar) at the simple_message level, extend the RAPID code to send the required bytes (in the correct order) over the TCP socket, extend the simple_message package to include deserialisers for the TCP_POSE message and finally extend the robot_state node to publish a ROS geometry_msgs/Pose (or perhaps a TF frame directly). This would be the recommended approach.

2. abuse the JOINT_POSITION message: instead of sending joint space poses, insert your data into the joint_data array, leave simple_message and robot_state as they are and interprete ROS JointState messages on your own. Note that doing it this way would mean that you cannot reuse the ROS robot_state_publisher, as it will expect joint space poses.

However, I cannot seem to send more than 6 variable (I tried to pack more raw data beyond 6) using the send_msg function in the ros-i abb's socket module and the ROS_StateServer module.

This suggests you went with option 2. This is definitely possible, but you need to take the layout of the messages into account: JOINT_POSITION messages contain a sequence nr (unused) and an array of 10 floats (see Message Structures of the ROS-Industrial Simple Message Protocol - Message Definitions - JOINT_POSITION). The abb_driver RAPID code fills the first 6 elements of the joint_data array with the joint poses of the first 6 axes of the robot. The 4 other elements are set to 0.

On the ROS side, the entire message is deserialised (so all 10 elements from joint_data), but only the indices for which the robot_status node has a known mapping will be included in the JointState msgs it publishes. That mapping is defined in the controller_joint_names parameter (here for an IRB 2400).

So in your specific case -- and for option 2 -- you'll have to change that parameter to include a seventh 'joint' (here you see the semantic problem).

If I have everything correct, that should lead to the robot_state node publishing all 7 values in the position array (which at this point are not the regular joint space poses but the XYZ+Quaternion TCP pose).

Note that there is no inherent limit in the length of the arrays/lists of a ROS JointState message: the only reason there are just 6 values there is because of the controller_joint_names parameter.

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