How to setup autoware for differential drive vehicle ?

[soblin]

Hi,

We've just installed latest autoware.universe on our mobile robot following the guides here and trying to setup sim/hw configuration, but the sample vehicle is automobile type.

Now we only have our urdf model + an indoor map(.pgm, .yaml file generated from gmapping offline). First of all, we want to:

• spawn our urdf on the Rviz
• change the controller to diff-drive type
• do SLAM in our lab

Our robot is attached with

• velodyne_vls

Can you briefly educate us on how we can migrate this to diff-drive robot ?

[taikitanaka3]

• for the map in autoware
  curently we are using lanelet2 map and pointcloud map you can test it in vector map builder here and as far as I know there is no conversion tool.

• for vehicle model in autoware
  there is sample vehicle model in here so you need to change this to diff-drive type.

[TakaHoribe]

With a simple approach (described later), Autoware can handle the differential-drive robot, but some functions are limited.

As background, Autoware is basically (at least for now) designed for Ackermann-type vehicles, and the Diff-Drive vehicle is not perfectly supported. For example, the path planning module can not take spin-turn planning into account.

So, how to use the Diff-Drive vehicle in the Autoware:

The most simple way is to have Autoware operate with the Diff-Drive robot as a virtual Ackermann vehicle. A pseudo base_link wheelbase must be set as a vehicle parameter, and the planning and control module will publish the ackermann_control_command (steering, steering_rotation_rate, velocity, and acceleration) based on the Ackermann vehicle model. (See the vehicle parameter example here: sample_vehicle_description, which is used in the tutorial demo.)

By using the Ackermann kinematics equation, you can convert the ackermann_control_command into a Twist message (you need to use the pseudo base_link wheelbase here). The twist (longitudinal and angular velocity) command can be finally converted into each wheel speed in the robot interface.

You can create your own vehicle_interface and implement those conversion there.

This should allow you to use the Autoware with the diff-drive robot for basic operation. If you want to realize spin-turn motion (or something very specific to the diff-drive configuration), a large improvement of the planner is necessary.

Currently no vehicle_interface for the diff-drive robot is supported, but it would be nice if we can support in the future.

[soblin]

Thanks for your reply.

I also had a look at this diagram and was able to get a better understanding of how AckermannCommand is finally generated and fed into the vehicle :)

I have another question on planning_simulator (aka psim) -- I noticed that in this tutorial simple_planning_simulator is subscribing to control commands and publishing current_pose as the ground-truth position of the vehicle.
So is it correct understanding that this node is simulating the physics of the automobile? If that is the case, do we need to implement corresponding node for our diff-drive robot to run a precise simulation?

[TakaHoribe]

Yes, the simple_planning_simulator subscribes to the Autoware command and computes the vehicle dynamics based on the command.
You can select the model from some options. See the simple_planning_simulator design.

If you want to simulate with a vehicle-specific command, you need to create a new model for that. You'll see how to add a new model in the code (there is an interface class for the vehicle model).

[TakaHoribe]

Opps, sorry. thank you!

[TakaHoribe]

About the SLAM, currently no package for mapping is supported as the Autoware function.
There are several OSS for mapping/SLAM, and it would be recommended to use those packages.

Personal recommendation from my colleague is InteractiveSlam.