steering angle in gym simulator

[tajgr]

This PR enables use steering angle beside angular speed in the Gym simulator. The simulator robot uses Ackerman steering. The name of the channel is "move" as well as for Spider.

[tajgr]

For tests run: python -m osgar.go run test-gym_simulation.json -a 30 in osgar/examples/gym

[tajgr]

Yesterday we discussed the appropriateness of using the "move" command for control. move was used because it already exists in the case of the Spider robot. I don't think it is appropriate to have multiple control commands if they contain the same information (speed, steering angle). So, how to solve the point?

• Keep move. Too general, may cause confusion in the future.
• Rename appropriately. The change must also be made for Spider. This will affect other projects and make it difficult to replay older logs. But there aren't that many logs. It is solvable (probably better now than in the future).
• What name to choose? I don't think it is appropriate to use the word "ackermann" because the robot does not need to use ackermann steering.

How about: desired_steering or desired_driving @m3d ??

[m3d]

as discussed yesterday "move" is too generic and for Spider it was meant to direct all wheels in given angle (no longer true with Car mode). I would like separate control - there used to be John Deere (one of the OSGAR driven machines), where you could also steer without need to move. Then there will be PatAMat (tomorrow?) so my motivation to standardize this is also higher ;).
I liked ROS topic (probably not used often)
http://docs.ros.org/en/melodic/api/ackermann_msgs/html/msg/AckermannDrive.html
... there is even steering angle velocity. Yet another "issue" is for odometry you need more like the base length etc.
My preference would be desired_steering if "desired" has to be part of control :). But feel free to leave it for the simulator (it will change in future anyway).

[tajgr]

Ok, we can discuss it later (next Tuesday?). Thanks.