problem in simulation of active suspension system with actuator dynamics.

the state space equation for simulink simulation is shown below:

in the simulink file , i took some random value for PID, during simulation it showing error like this:

Derivative input 1 of 'suspmod/actuator/x5' at time 0.003 is Inf or NaN. Stopping simulation. There may be a singularity in the solution. If not, try reducing the step size (either by reducing the fixed step size or by tightening the error tolerances)

the actuator block has some non linear function in it. how to solve this problem?

Answer 1

[Sebastian Castro]

This error message happens when you put an infinite value into an Integrator block.

You see how the error message points to the derivative of x5, and that expression has a (1/x6) term in it? I bet it's that -- you may want to protect for divisions by zero when x6 = 0.

- Sebastian

[senthil kumar]

thank you for your response. i got your point. the equation goes to singularity at the denominator of x6.

i corrected this by introducing eps function. similarly when sqrt goes negative will also create complex number. so i used modulus on sqrt as attached in my simulink file.

Now the simulation is running without any problem. but the results are not as i expect. the hydraulic force is not right to actuate quarter car suspension.

something wrong in it. can you fix it?

do i change saturation value in integrator?

[Rishi Naik]

can you please share file of your final result?