u/Straight_Mind3569

Hi everyone,

I'm building a 4WD EV model in Simulink/Simscape and I'm stuck on an issue that I haven't been able to solve.

My model consists of:

* Drive Cycle Source (FTP75) * Longitudinal Driver * H-Bridge * DC Motor * Vehicle Body * 4 Magic Formula Tires * Ideal Rotational Motion Sensor * PS-Simulink Converters

**Problem:**

* The Drive Cycle Source outputs the correct FTP75 reference speed. * The reference speed appears correctly on the scope. * However, the output from the PS-Simulink Converter (vehicle speed feedback) stays at **0** throughout the simulation. * The Longitudinal Driver therefore receives a zero feedback velocity. * The rotational motion sensor is connected to a PS-Simulink Converter, and I can see the angle changing, so the motor/shaft appears to rotate.

Around **20 seconds** I consistently get this warning:

> Solver was unable to reduce the step size without violating the minimum step size... This may be caused by algebraic constraints in the differential-algebraic system or by high stiffness.

Things I've already checked:

* Drive Cycle Source is connected to the Longitudinal Driver. * Vehicle Body H ports are connected to the Magic Formula Tires. * Tire normal force inputs (N) are connected to the Vehicle Body NR/NF outputs. * The rotational sensor is connected to a PS-Simulink Converter. * The PS-Simulink Converter connected to the rotational sensor is **not** unconnected (I verified the wiring).

The attached scope shows:

* Blue = Drive Cycle Source (correct FTP75 profile) * Yellow = PS-Simulink Converter output (stays at 0)

My questions are:

1. Why would the Vehicle Body velocity remain zero even though the motor/shaft rotates?
2. Is this more likely to be a Vehicle Body/Tire configuration issue, a driveline connection issue, or a PS-Simulink Converter configuration issue?
3. Could the solver warning be causing the zero vehicle speed, or is it more likely a consequence of another modeling error?

I've attached screenshots of the full model, the Vehicle Body and tire connections, the scope, and the solver warning.

Any suggestions on what to check next would be greatly appreciated.

The silver configuration says

Solver is encountering difficulty in simulating model 'ev' at time 20.001318478246887. Simulink will continue to simulate with warnings. Please check the model for errors.

Ungroup 3 similar

Caused by:

Solver was unable to reduce the step size without violating minimum step size of 7.1059E-14 for 1 consecutive times at time 20.0013. Solver will continue the simulation with the step size restricted to 7.1059E-14 and using an effective relative error tolerance of 0.00717986, which is greater than the specified relative error tolerance of 0.001. This usually may be caused by violating algebraic constraints in the differential-algebraic system or by the high stiffness of the system. Try tightening the error tolerances, and/or the tolerances for computing consistent conditions. If the problem persists, please check the system or increase the solver Number of consecutive min steps violation parameter.

Suggested Actions

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