Hi @Ming
The key reason the Inertia Sensor continues to report the same values even after Weld Joint detached a component from main body is because the sensor is likely still measuring the original composite body (as defined at the beginning of the simulation). In Simscape Multibody, the structure of the multibody system is fixed at the start of the simulation, which means the dynamic creation or removal of rigid connections does not update the connected mass properties from the solver’s perspective.
Kindly refer the following two workarounds to model this kind of dynamic structural reconfiguration and accurately measure the changing mass and inertia
1. Using Simscape Component-On/Off Modeling
Instead of disabling joints or trying to switch subsystems mid-simulation, consider physically modeling the detachment using actuated joints or force thresholds (e.g., a spring-damper with a breakaway force), which would allow components to detach naturally. Once detached, they are no longer contributing forces/torques to the main body.
2. Post-Processing
If real-time measurement proves too difficult or computationally expensive, consider logging the simulation data (e.g., joint states, detachment events) and computing mass/inertia offline in MATLAB.
For more information regarding the Inertia block, kindly refer the following documentation - https://www.mathworks.com/help/sm/ref/inertia.html
I hope this resolves the issue.
