When selecting an actuator for a controls application - e.g. choosing a servo motor for a self-balancing robot - I understand that it's important for the actuators to have fast enough dynamics that they don't significantly impact the system's linearity, and thus ensure the control algorithms function as designed. However, how much faster is fast enough? Are there any rules of thumb - c.f. Nyquist's Theorem in signal processing - for how I should choose my motor's rise time given that my controller's sample period is known?