I designed control systems for brushless servo motors and more recently did the power control for very power hungry ASICs of a very well known company. Tuning

I designed control systems for brushless servo motors and more recently did the power control for very power hungry ASICs of a very well known company. Tuning is important but when you come to design a control system, you need to look at the overall system - and this is something textbooks don't really tell you. Control systems are all about reacting quickly enough and accurately enough. Delay and poor incoming/outgoing signal quality are the enemies of the control system: 1. The delay from sensor to controller (e.g. SPI bus incurred delay between your gyro sensor and your processor) 2. The bandwidth of each component. If your gyro sensor is only 10hz bandwidth, it'd be difficult to control anything reasonably fast. Note that bandwidth is often given in frequency to 3dB attenuation (half the amplitude) - that's not enough, you need to understand the phase distortion: in other words, as you approach the bandwidth limit, does your signal get distorted in time? because that's very bad for a control system. 3. The resolution of your actuator - if you end up using an on-off actuator, it'd be impossible to do any precision control. Do you want to position a motor accurately? Make sure you use more than 8-bit PWM. 4. Static/dynamic response: things are usually not nicely linear. Things at standstill take a different amount of effort to move than once they are in motion. My experience has shown time and time again that if you get the system fundamentals correct, implementing and tuning the control loop is reasonably trivial. The secret is having a system that's an order of magnitude faster (higher bandwidth) than what you're trying to control. You really need to think about control systems in the frequency domain: "what I'm controlling requires the bandwidth of X, I need to sample with with n * X, my processor is this fast, my output signal is that accurate, this is the end to end delay". Someone once said "any non-linear system becomes linear when you sample it quickly enough". I don't know who said it or whether it's even remotely true for all parts of life - for control systems though, it's definitely a rule to go by.