How can I send a direct movement command to carter_sim?

Autonomous Machines Robotics - Isaac Isaac SDK
1

Hi all,

I am trying my hand at some basic movement commands. I am wanting to be able to send a message to carter_sim that says something simple like spin on the spot or move forward by giving it a linear and angular velocity. I am not looking to use the goal setting functionality with the navigation stack and all that includes. Simply move the robot with a given velocity message.

Currently though I am at a loss as to where to start. I don’t know what Proto message I can send and to what module to get it to work.

My current impression is that I would send a StateProto to “base_simulation/isaac.flatsim.DifferentialBaseSimulator/diff_base_command” and that would translate the velocity messages into movement.

However, I am not sure about this and don’t know how I would correctly create a StateProto if I am correct.

Can I receive some guidance here please?

2

If you check out the proportional control tutorials in isaac/apps/tutorials, there is an example of how to build and publish a StateProto (linear speed is its “forward” travel rate while angular speed is the turn rate):

ProportionalControlCpp.cpp:

// Publish control command
  messages::DifferentialBaseControl command;
  command.linear_speed() = control;
  command.angular_speed() = 0.0;  // This simple example sets zero angular speed
  ToProto(command, tx_cmd().initProto());
  tx_cmd().publish();

proportional_control_python.py:

# Publish control command
  tx_message = self.tx.init_proto()
  data = tx_message.init('data', 2)
  data[0] = control  # linear speed
  data[1] = 0.0  # This simple example sets zero angular speed
  self.tx.publish()

You will also need to set up the output connections, variables, etc. as done in the tutorials, but that’s the meat of transmitting a StateProto with linear and angular velocity.

See https://docs.nvidia.com/isaac/isaac/doc/message_api.html#stateproto for more info on the prototype

3

Excellent! Just the pointer I needed to get me started.

Thanks!