ODEintWarning: Excess work done on this call (perhaps wrong Dfun type)

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I was working on simulating suspension systems in quarter car vehicle using second order differential equations, and I was using Bees Algorithm to as PID controller.

def optimal_stiff(kt):
acc_t=-(kt\*(0-1)-ks\*(0-xt\[0\])-b\*(xs\[1\]-xt\[1\]))/Mt
return -abs(acc_t)

def cartire_optim(current_state,t):

    xs[0],xt[0],xs[1],xt[1]=current_state           # initialize the variables
    if t<1:                                         # initialize the road profile
        xr=0
    else:
        xr=1
    search_bound=([ks],[2*ks])
    optimal= BeesAlgorithm(optimal_stiff,search_bound[0],search_bound[1])
    optimal.performFullOptimisation(max_iteration=20)
    stiff= optimal.best_solution
    
    acc_s=-(ks*(xs[0]-xt[0])+b*(xs[1]-xt[1]))/Ms              # acceleration of the Sprung mass
    acc_t=-(stiff.values[0]*(xt[0]-xr)-ks*(xs[0]-xt[0])-b*(xs[1]-xt[1]))/Mt  # acceleration of the Unsprung mass
    return np.array([xs[1],xt[1],acc_s,acc_t])

solution_optim= odeint(cartire_optim,state,time_point)

When I define the variables needed and run the code, it works till a time step around 1.75 sec and spit out zeros.
The Graph of the xs

This line should stabilize at 1 not zero.

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