lets say the given system is the wheel of car running over a bump with the function S. now there is no fixed connection between the wheel and the bump so its not able to transmit any kind of pulling force from the wheel to the bump. my question how can i deactivate any kind of pulling(left side should never be positive (sorry i made a mistake with saying it should only be positive)).

m[1]*(D(D(x)))(t)+d[0]*(D(x))(t)+d[1]*(D(x))(t)+c[0]*x(t)+c[1]*x(t)+50000 = -(1/1000)*c[1]*S-(1/1000)*d[1]*DS*((1/60)*(2*Pi*250))-(1/1000)*m[1]*DDS*((1/60)*(2*Pi*250))^2;