I've built a simple Simulink model of a straightforward mass/spring/damper system. It seems to work fine, but I'm puzzled why the final steady state output (displacement of the mass) doesn't converge back to zero (the initial starting point).
Have worked from standard equation:
mx''+cx'+kx=F
rearranged to give:
x''=1/m (-cx'-kx+F)
The forcing function F is a unit step input, and varying damping coefficient I get appropriate responses, but they all converge to a steady state value with a very small offset from zero position.
Why doesn't the mass come to rest back at it's starting point?
Model and output plots here:
I've set the initial condition in integrator one to "1", in order to get the mass oscillating either side of its starting position, with extremes in both positive and negative directions (as opposed to just oscillating in the positive range). Is this the correct way to achieve this behaviour?
Would appreciate words of advice…
G
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