I'm not sure if this is expected behavior or a bug.

I'm trying to attach an IMU sensor to a frame that does not have a RigidBodyAPI. Specifically, the prim path is:

/ergoCub/root_link/torso_1/waist_imu_0

As shown in the image below, the prim exists and has valid transform data, but no RigidBodyAPI component:

When I try to create the IMU sensor using:

imu = ImuCfg(prim_path="{ENV_REGEX_NS}/Robot/root_link/torso_1/waist_imu_0", debug_vis=False)

I get the following runtime error:

RuntimeError: Failed to find a RigidBodyAPI for the prim paths: /World/envs/env_.*/Robot/root_link/torso_1/waist_imu_0

This error originates from this section of the code:

Question

Is it required that the target prim for an IMU sensor has RigidBodyAPI?
I was expecting it to be possible to attach IMUs to arbitrary (static or articulated) frames, not just rigid bodies.

I'm using Isaac Lab v2.1.1 and IsaacSim 4.5.0