System Dynamics and Control: Module 4a - Introduction to Modeling Mechanical Systems

[@EslamMohamedX]

This is by far the best explanation of this concept out there! Thanks a lot.

[@manumohan1986]

Great explanation.

[@TjipzPK]

Why not (x2-x1) or (x2+x1) or (x1+x2) to me it just seems completely random what is chosen. Because if we chose the positive direction to be to the right, and we compress the spring by moving x1, to the left, and freezing x2 in place. In my head x1 moves negatively. Replacing x1 with the number we found, we get a negative force, but the force should be in the positive direction, counteracting the compressing force. What am I doing wrong? Thank you.

[@sooooleh]

Thanks for your efforts, How can I model coulomb damping friction in simulink? i don't know where to put the sgn!