Were does to oscillating come from?

Hello everybody,

For an assignment we have to make a simple model of a RC car which gets as an input the throttle and steering percentage from the controller and as an output it has to give the longitudinal speed, the lateral speed and the yaw rate. After finding the correct formulas and implementing these into simulink, it does not give the correct output. When the longitudinal and the lateral speed are plotted it gives a oscillating graph, which obviously is not right.

We have tried to remove all variables and only inputting constants, but still whatever we try, we keep getting oscillating formulas.

I have attached our model. Does somebody know where the oscillating comes from?

Thank you in advance, Jan Willem

Answer 1

[Zack Peters]

Hi Jan,

Quick look at hte model shows that your 'u' signal hovers around '0' at around time 2.79. When that happens, your F_lat subsystem divides by 'u' getting close to a divide by zero condition, causing the calculations to go haywire.

Do you have the equation of motions written out by hand? Perhaps you can paste them into here and someone can double check that there were no modeling mistakes.

~Zack