How do I compute the impulse response of a robot? I am trying to model a robot (my question in robotics.SE), so that I may train it using some reinforcement learning techniques. I was wondering if I can compute an impulse response of a four wheel robotic chassis empirically? Or something similar that might help me model the robot. Does a thing like 'the impulse response of a robot' even make sense?

Since a single strobe of a PWM signal shall hardly cause any movement, but a steady stream of PWM signals will, can I consider the impulse response as an infinite impulse response that superposition to cause perceivable motion?

I am certain that the robot chassis is a non-linear system. Generally speaking, will impulse response make any sense on a non-linear system?
Impulse response makes sense for linear systems. If your system is nonlinear forget it. If you assume that your system is linear time invariant, you may want to measure the impulse response by exerting a short duration high energy pulse to your robot. It must have sufficiently high energy so that most of the exerted energy is transferred to kinematic energy of the robot to enable motion. 

If this is not possible you can apply longer duration pulses to your robot and then measure its response (motion). You must deconvolve then the response and the input to get the impulse response of your robot. You may try this for a number of different shape pulses and if you get impulse responses similar to each other every time, you can be fairly sure that your system is linear. 

Your comment on having an infinite impulse response is not in line with correct systems modelling, so forget about it.