5. Adding A Controller¶
5.1. Learning Objectives¶
This tutorial shows how to create and use a custom controller to move a mobile robot. It then shows how to use the controllers available in Omniverse Isaac Sim. After this tutorial, you should be more confident adding and controlling robots in Omniverse Isaac Sim.
10 Minute Tutorial
5.2. Getting Started¶
Prerequisites
Please review Hello Robot prior to beginning this tutorial.
Begin with the source code open from the previous tutorial, Hello Robot.
5.3. Creating a Custom Controller¶
Let’s code an openloop controller that uses the unicycle model for differential drive. Controllers in Omniverse Isaac Sim inherits from the BaseController interface. A forward method needs to be implemented and it has to return an ArticulationAction type.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 from omni.isaac.examples.base_sample import BaseSample from omni.isaac.jetbot import Jetbot from omni.isaac.core.utils.types import ArticulationAction from omni.isaac.core.controllers import BaseController import numpy as np class CoolController(BaseController): def __init__(self): super().__init__(name="my_cool_controller") # An open loop controller that uses a unicycle model self._wheel_radius = 3 self._wheel_base = 11.25 return def forward(self, command): # command will have two elements, first element is the forward velocity # second element is the angular velocity (yaw only). joint_velocities = [0.0, 0.0] joint_velocities[0] = ((2 * command[0]) - (command[1] * self._wheel_base)) / (2 * self._wheel_radius) joint_velocities[1] = ((2 * command[0]) + (command[1] * self._wheel_base)) / (2 * self._wheel_radius) # A controller has to return an ArticulationAction return ArticulationAction(joint_velocities=joint_velocities) class HelloWorld(BaseSample): def __init__(self) -> None: super().__init__() return def setup_scene(self): world = self.get_world() world.scene.add_default_ground_plane() jetbot_robot = world.scene.add(Jetbot(prim_path="/World/Fancy_Robot", name="fancy_robot")) return async def setup_post_load(self): self._world = self.get_world() self._jetbot = self._world.scene.get_object("fancy_robot") self._world.add_physics_callback("sending_actions", callback_fn=self.send_robot_actions) # Initialize our controller after load and the first reset self._my_controller = CoolController() return def send_robot_actions(self, step_size): #apply the actions calculated by the controller self._jetbot.apply_wheel_actions(self._my_controller.forward(command=[20.0, np.pi/ 4])) return
5.4. Using the Available Controllers¶
Omniverse Isaac Sim also provides different controllers under the many robot extensions.
Let’s re-write the previous code using the DifferentialController
class and add a WheelBasePoseController
.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 from omni.isaac.examples.base_sample import BaseSample from omni.isaac.jetbot import Jetbot # This extension includes several generic controllers that could be used with multiple robots from omni.isaac.motion_generation import WheelBasePoseController # Robot specific controller from omni.isaac.jetbot.controllers import DifferentialController import numpy as np class HelloWorld(BaseSample): def __init__(self) -> None: super().__init__() return def setup_scene(self): world = self.get_world() world.scene.add_default_ground_plane() jetbot_robot = world.scene.add(Jetbot(prim_path="/World/Fancy_Robot", name="fancy_robot")) return async def setup_post_load(self): self._world = self.get_world() self._jetbot = self._world.scene.get_object("fancy_robot") self._world.add_physics_callback("sending_actions", callback_fn=self.send_robot_actions) # Initialize our controller after load and the first reset self._my_controller = WheelBasePoseController(name="cool_controller", open_loop_wheel_controller=DifferentialController(name="open_loop_controller"), is_holonomic=False) return def send_robot_actions(self, step_size): position, orientation = self._jetbot.get_world_pose() self._jetbot.apply_wheel_actions(self._my_controller.forward(start_position=position, start_orientation=orientation, goal_position=np.array([80, 80]))) return
Press Ctrl+S
to save and hot reload the example. Then press the LOAD
button to reload the scene.
5.5. Summary¶
This tutorial covered the following topics:
Creating a custom controller to move a mobile robot
Using Controller Classes from Omniverse Isaac Sim
5.5.1. Next Steps¶
Continue on to the next tutorial in our Essential Tutorials series, Adding a Manipulator Robot, to learn how to add a manipulator robot to the simulation.