We also needed a windowing environment to develop the user interface. Above all, we needed speed. The hunt was on for an OS that could provide true realtime response. Our final choice was based on pure speed issues like context-switching times, but also on factors such as level of technical support provided and software development environment. QNX scored high on nearly every count.
Feedback control is the most commonly used approach for control systems.
The output from the pressure and velocity transducers is measured. The input is changed according to the difference between the desired and measured output. Compared to feedback control, feedforward control is more advanced. If you don't have a feedforward loop, any sharp change in the input signal will result in a large difference between the desired and actual output until the feedback system catches up. To partially remove this large error and help speed up the transition, a feedforward signal feeds the input change through immediately.