Robot behaving weirdly (extreme abrupt movements) in collision for custom imported asset from URDF

Robotics & Edge Computing Robotics - Isaac Isaac Gym
1

Hello all,

I am working on training a uFactory xARM 6 that I imported using URDF Importer workflow. I noticed that in RL training using Isaac Lab, the joint velocities and action rates approach infinity. After manually investigating the behavior of the robot in collision with the table (as can be see in the associated video), the robot starts moving around as if physics becomes unstable and causes the robot to jump around abruptly.

UF_XARM6_WITH_GRIPPER = ArticulationCfg(
    spawn=sim_utils.UsdFileCfg(
        usd_path="omniverse://localhost/Users/yrh012/ufactory/xarm_with_gripper/ufactory.usd",
        rigid_props=sim_utils.RigidBodyPropertiesCfg(
            disable_gravity=False,
            max_depenetration_velocity=10.0,
        ),
        articulation_props=sim_utils.ArticulationRootPropertiesCfg(
            enabled_self_collisions=False
        ),
        activate_contact_sensors=False,
    ),
    init_state=ArticulationCfg.InitialStateCfg(
        joint_pos={
            "joint1": 0.0,
            "joint2": -0.3,
            "joint3": -1.17,
            "joint4": 0.0,
            "joint5": 0.0,
            "joint6": 0.0,
            "gripper.*": 0.00,
        },
    ),
    actuators={
        "arm": ImplicitActuatorCfg(
            joint_names_expr=["joint.*"],
            velocity_limit=50.0,
            effort_limit=40.0,
            stiffness={
                "joint1": 1000,
                "joint2": 1000,
                "joint3": 1000,
                "joint4": 1000,
                "joint5": 1000,
                "joint6": 1000,
            },
            damping={
                "joint1": 200,
                "joint2": 200,
                "joint3": 200,
                "joint4": 200,
                "joint5": 200,
                "joint6": 200,           
            }
        ),
        "gripper":ImplicitActuatorCfg(
            joint_names_expr=["gripper.*"],
            velocity_limit=0.2,
            effort_limit=200.0,
            stiffness=2e3,
            damping=1e2
        ),
    },
)

I tried changing articulation_props and rigid_props position and velocity solver parameters but still similar behavior was observed. I would like to ask, how can I avoid such behavior and better simulate the robot?