Modelling a torque limiter in Simscape, "Equations of one or more components may be dependent or inconsistent."

Hello.

I'm trying to modell a torque limiter. Use-case: car drives over a pothole, motor is commanded the same torque as before, wheel accelerates and is rapidly braked again after the pothole, then overload-clutch should open.

I'm getting following error:

An error occurred while running the simulation and the simulation was terminated

Caused by: all components and nodal across variables involvedCannot solve for one or more variables, including dynamic variable derivatives: Time derivative of 'Ideal_Rotational_Motion_Sensor1.phi' (Angle) 'Disk_Friction_Clutch.F.w' (Rotational velocity) 'Disk_Friction_Clutch.damper.C.w' (Rotational velocity) 'Disk_Friction_Clutch.damper.w' (Rotational velocity) 'Disk_Friction_Clutch.fundamental_clutch.F.w' (Rotational velocity) 'Disk_Friction_Clutch.fundamental_clutch.S' (S) 'Disk_Friction_Clutch.fundamental_clutch.clutch.F.w' (Rotational velocity) 'Disk_Friction_Clutch.fundamental_clutch.clutch.S' (S) 'Disk_Friction_Clutch.fundamental_clutch.clutch.w' (Rotational velocity) 'Ideal_Rotational_Motion_Sensor1.R.w' (Rotational velocity) 'Ideal_Rotational_Motion_Sensor1.W' (W) 'Ideal_Rotational_Motion_Sensor1_W' (Ideal_Rotational_Motion_Sensor1_W) 'Ideal_Torque_Sensor.C.w' (Rotational velocity) 'Ideal_Torque_Sensor.R.w' (Rotational velocity) 'Tire_Friction_Parameterized.A.w' (Rotational velocity) 'Tire_Friction_Parameterized.S' (S) 'Tire_Friction_Parameterized.fundamental_clutch.B.w' (Rotational velocity) 'Tire_Friction_Parameterized.fundamental_clutch.S' (S) 'Tire_Friction_Parameterized.fundamental_clutch.clutch.B.w' (Rotational velocity) 'Tire_Friction_Parameterized.fundamental_clutch.clutch.S' (S) 'Tire_Friction_Parameterized.fundamental_clutch.clutch.w' (Rotational velocity) 'Tire_Friction_Parameterized_S' (Tire_Friction_Parameterized_S) Equations (including switched-linear and nonlinear equations) of one or more components may be dependent or inconsistent. This can cause problems in transient initialization. Here is the set of components involved: all components involved'torque_limiter/Disk Friction Clutch'Equation locations are: 'C:\Program Files\MATLAB\R2022a\toolbox\physmod\simscape\library\m\+foundation\+mechanical\+rotational\damper.ssc' (line 21) 'C:\Program Files\MATLAB\R2022a\toolbox\physmod\sdl\sdl\+sdl\+clutches\+fundamental_components\two_way_clutch.sscp' (no line number info) 'C:\Program Files\MATLAB\R2022a\toolbox\physmod\sdl\sdl\+sdl\+clutches\disk_friction_clutch.ssc' (line 353) 'torque_limiter/PS Constant1'Equation location is: 'C:\Program Files\MATLAB\R2022a\toolbox\physmod\simscape\library\m\+foundation\+signal\+sources\constant.ssc' (line 21) 'torque_limiter/Tire (Friction Parameterized)'Equation locations are: 'C:\Program Files\MATLAB\R2022a\toolbox\physmod\sdl\sdl\+sdl\+clutches\+fundamental_components\two_way_clutch.sscp' (no line number info) 'C:\Program Files\MATLAB\R2022a\toolbox\physmod\sdl\sdl\+sdl\+tires\tire_friction.ssc' (line 123)

But the simulation even runs until there is again normal force acting on the tire but then it stops.

Hopefully someone can help me, thanks and best regards...

Paul

Answer 1

[Steve Miller]

Hi Paul - typically, this error message occurs when there is a node with no inertia directly connected to it. Once the clutch opens, the node to the right only has inertia connected to it via the tire, and the tire has a compliance in it. This means the node to the right of the clutch can accelerate infinitely fast (Torque = Inertia * Acceleration), which is bad for numerical solvers.

Add an inertia to the right of the clutch and the simulation will run.

See image below.

--Steve

[Paul Richardt]

Thank You, it works now.