[Question] Custom single-steering-wheel robot can't turn when steering angle is set below 0.6

[Shaw-Way]

Question

I built a custom single-steering-wheel forklift robot. I set the drive joint config as follows.

"drive": ImplicitActuatorCfg(
            joint_names_expr=["steerTopToSteerWheel"],
            effort_limit_sim=1000000,
            velocity_limit=20.0,
            stiffness=5729.578,
            damping=572957.8,
        )

And the steering joint config is as follows.

"steering": ImplicitActuatorCfg(
            joint_names_expr=["bodyToSteerTop"],
            effort_limit_sim=1000000,
            velocity_limit=5.0,
            stiffness=5729578,
            damping=5729.578,
        ),

The forklift also has six additional passive support wheels, and I set the friction coefficients for the steering wheel and the support wheels as follows.

steering_wheel_material_cfg: RigidBodyMaterialCfg = RigidBodyMaterialCfg(
        static_friction=1.0,
        dynamic_friction=1.0,
        restitution=0.0,
    )
support_wheel_material_cfg: RigidBodyMaterialCfg = RigidBodyMaterialCfg(
        static_friction=0.3,
        dynamic_friction=0.3,
        restitution=0.0,
    )

I’ve noticed something strange: when the steering angle of the wheel is set below 0.6 rad, the forklift can only move in a straight line and cannot turn. But when the steering angle is set above 0.6 rad, the forklift is able to turn. I don't know how to set the appropriate parameters for the drive joint and steering joint.

Build Info

Describe the versions that you are currently using:

• Isaac Lab Version: [2.3.0]
• Isaac Sim Version: [5.1.0]

[Shaw-Way]

This is the running video, and the green part is the cylinder collider of the steering wheel.

Screencast.from.2025.11.18.15.04.10.webm

[Shaw-Way]

Can anybody give me some help? This issue has been bothering me for several days.

[RandomOakForest]

Thank you for posting this. Here are a couple of steps to consider. I'll move this post to our Discussions section for follow up.

• If the forklift only turns above 0.6 rad, inspect whether wheel-slip or support wheel drag is preventing the pivot at smaller angles.
• Visualize the contact forces between the support wheels and the ground. If these are high even at low steering angles, decrease the support wheel’s lateral friction further.

[Shaw-Way]

Thank you for your answer. But how to visualize the contact forces?

[Shaw-Way]

I finally resolved this issue by switching the steering-joint config to DCMotorCfg as follows:

"steering": DCMotorCfg(
            joint_names_expr=["bodyToSteerTop"],
            effort_limit_sim=20,
            saturation_effort=1000,
            velocity_limit=1.5,
            stiffness=5729578,
            damping=5729.578,
        )

But I don't know why it works.

[Shaw-Way]

Another issue has occurred: when using DCMotorCfg and set_joint_position_target to control the steering angle of the wheel, at lower driving speeds, the steering angle gradually increases until it reaches the joint's rotation limit.