Joint/IMU/Sensor ordering in datagram is documented and frozen

[dljsjr]

We now have robot feedback working in our software. But we (intentionally) defined an IDL that does not have identifiers for the different sensors because of payload overhead.

We just need to establish what order the joints, IMUs, and F/T sensors are serialized and know that ordering and treat it as convention.

[francesco-romano]

Hi @dljsjr
As soon as #15 is merged, you will have access to IMUs and FTs readings.
As it is written the code, the ordering is defined by the configuration file.
In particular, the order in which you specify the FTs and the IMUs will be the order used in the serialisation.

[dljsjr]

@francesco-romano But what about the joints? I see the limb ordering but that doesn't help me with the joint ordering.

I can assume that the joints will follow the kinematic chain as defined in the SDF and then I just go limb by limb in that order but I just want to make sure that a.) that is a good assumption, and b.) it isn't going to change randomly.

[traversaro]

We are going to document the joint order properly, but as a working pointer the joint order is defined in https://github.com/robotology-playground/ihmc-ors-yarp/blob/master/robots/icubGazeboSim/launch-bridgeihmcors-sim.xml#L37 .

[dljsjr]

@francesco-romano @traversaro Are those the only joints that are published/controllable? That list seems to exclude the wrist and neck joints.

[traversaro]

Those are the joints that support torque control. We can add also the wrist/neck joints, but we can't control those one in torque control mode.

[dljsjr]

@traversaro We'll definitely at least need them for feedback, at the very least the neck. Control over them would also be nice, maybe just reject the command if the mode is set to TORQUE on the receiving side for those joints? And we'll just try to be extra sure that we only send position commands to those joints. Our control architecture can handle setups where some joints are position controlled no problem.

[traversaro]

Ok, I can easily add those joints to the exposed joints.