AssertionError: Differential drive requires both wheel joints to have same min velocities!

[Daniel70-liu]

### This is the test code
Sorry to bother you, I would like to ask why such an error occurs. Can anyone explain it?

import numpy as np
import omnigibson as og
from omnigibson.macros import gm
from omnigibson.sensors import VisionSensor
from omnigibson.utils.ui_utils import KeyboardRobotController
from omnigibson.robots import Fetch, Tiago 

gm.USE_GPU_DYNAMICS = False
gm.ENABLE_FLATCACHE = True

def main(random_selection=False, headless=False, short_exec=False):
    """
    Robot grasping mode demo with selection
    Queries the user to select a type of grasping mode
    """
    og.log.info(f"Demo {__file__}\n    " + "*" * 80 + "\n    Description:\n" + main.__doc__ + "*" * 80)

    
    scene_cfg = dict(type='Scene')
    
    table_cfg = dict(
        type="DatasetObject",
        name="table",
        category="breakfast_table",
        model="lcsizg",
        bounding_box=[0.5, 0.5, 0.8],
        fixed_base=True,
        position=[0.7, -0.1, 0.6],
        orientation=[0, 0, 0.707, 0.707],
    )

    chair_cfg = dict(
        type="DatasetObject",
        name="chair",
        category="straight_chair",
        model="amgwaw",
        bounding_box=None,
        fixed_base=False,
        position=[0.45, 0.65, 0.425],
        orientation=[0, 0, -0.9990215, -0.0442276],
    )

    box_cfg = dict(
        type="PrimitiveObject",
        name="box",
        primitive_type="Cube",
        rgba=[1.0, 0, 0, 1.0],
        size=0.05,
        position=[0.53, -0.1, 0.97],
    )
   
    cfg = dict(scene=scene_cfg, objects=[table_cfg, chair_cfg, box_cfg])

    env = og.Environment(configs=cfg)
    
    
    robot = Fetch(  
        name="Fetch",
        obs_modalities=["rgb"],
        action_type="continuous",
        action_normalize=True,
    )


    og.sim.import_object(robot)  
    robot.set_position([0, 0, 0])
    og.sim.play()
    og.sim.step()
    
    robot.reset()
    robot.keep_still()
    
    
    for sensor in robot.sensors.values():
        if isinstance(sensor, VisionSensor):
            sensor.image_height = 720
            sensor.image_width = 720

    og.sim.viewer_camera.set_position_orientation(
        position=np.array([-2.39951,  2.26469,  2.66227]),
        orientation=np.array([-0.23898481,  0.48475231,  0.75464013, -0.37204802]),
    )

    print("Press ctrl+c to quit")

    max_steps = -1 if not short_exec else 100
    step = 0
    while step != max_steps:
        action = np.random.uniform(-1,1,robot.action_dim)
        for _ in range(10):
            env.step(action)  # Execute actions for the robot
            step += 1

    env.close()

if __name__ == "__main__":
    main()

Traceback (most recent call last):
File "C:\Users\rtxa6000\測試flowise_omnigibson\Fetch_create_test.py", line 130, in
main()
File "C:\Users\rtxa6000\測試flowise_omnigibson\Fetch_create_test.py", line 95, in main
og.sim.step()
File "C:\Users\rtxa6000\OmniGibson\omnigibson\simulator.py", line 783, in step
self._non_physics_step()
File "C:\Users\rtxa6000\OmniGibson\omnigibson\simulator.py", line 639, in _non_physics_step
obj.initialize()
File "C:\Users\rtxa6000\OmniGibson\omnigibson\prims\prim_base.py", line 74, in initialize
self._initialize()
File "C:\Users\rtxa6000\OmniGibson\omnigibson\robots\fetch.py", line 263, in _initialize
super()._initialize()
File "C:\Users\rtxa6000\OmniGibson\omnigibson\robots\manipulation_robot.py", line 216, in _initialize
super()._initialize()
File "C:\Users\rtxa6000\OmniGibson\omnigibson\robots\robot_base.py", line 186, in _initialize
super()._initialize()
File "C:\Users\rtxa6000\OmniGibson\omnigibson\objects\stateful_object.py", line 154, in _initialize
super()._initialize()
File "C:\Users\rtxa6000\OmniGibson\omnigibson\objects\controllable_object.py", line 124, in _initialize
self._load_controllers()
File "C:\Users\rtxa6000\OmniGibson\omnigibson\objects\controllable_object.py", line 183, in load_controllers
controller = create_controller(**cfg)
File "C:\Users\rtxa6000\OmniGibson\omnigibson\controllers_init.py", line 34, in create_controller
return controller_cls(**kwargs)
File "C:\Users\rtxa6000\OmniGibson\omnigibson\utils\python_utils.py", line 90, in wrapper
func(*values.args, **values.kwargs)
File "C:\Users\rtxa6000\OmniGibson\omnigibson\controllers\dd_controller.py", line 60, in init
min_vels[0] == min_vels[1]
AssertionError: Differential drive requires both wheel joints to have same min velocities!

[hang-yin]

Hello! Thanks for reaching out. This is a little hard for me to tell what the actual problem is, but here should be a simple fix: I see that you based this script off of the grasping mode example - do you mind try loading the robot with a robot config instead of importing it after the environment has been initialized? For example:

    scene_cfg = dict(type='Scene')

    robot0_cfg = dict(
        type="Fetch",
        obs_modalities=["rgb"],  # we're just doing a grasping demo so we don't need all observation modalities
        action_type="continuous",
        action_normalize=True,
        grasping_mode=grasping_mode,
    )
    
    table_cfg = dict(
        type="DatasetObject",
        name="table",
        category="breakfast_table",
        model="lcsizg",
        bounding_box=[0.5, 0.5, 0.8],
        fixed_base=True,
        position=[0.7, -0.1, 0.6],
        orientation=[0, 0, 0.707, 0.707],
    )

    chair_cfg = dict(
        type="DatasetObject",
        name="chair",
        category="straight_chair",
        model="amgwaw",
        bounding_box=None,
        fixed_base=False,
        position=[0.45, 0.65, 0.425],
        orientation=[0, 0, -0.9990215, -0.0442276],
    )

    box_cfg = dict(
        type="PrimitiveObject",
        name="box",
        primitive_type="Cube",
        rgba=[1.0, 0, 0, 1.0],
        size=0.05,
        position=[0.53, -0.1, 0.97],
    )
   
    cfg = dict(scene=scene_cfg, robots=[robot0_cfg], objects=[table_cfg, chair_cfg, box_cfg])

    env = og.Environment(configs=cfg)

    robot = env.robots[0]
    robot.set_position_orientation(position=[0, 0, 0])
    robot.reset()
    robot.keep_still()

Let me know if this works for you!

[Daniel70-liu]

This method can be solved, thank you for your help.