Analysis of a mixed transfer function and state space implementation of cascade control

Cascade Control is a tool to control coupled systems with a certain distance in their operating frequencies. This allows independent optimization of the inner control loop to feed an optimal setpoint to the outer controller. For the design literature recommends vague factors of 2-5, 3-10 or "much faster" between the controller crossover frequencies, but this work gives more precise lower boundaries, achievable if the system is well-known. Therefor a different implementation of cascade control is presented. The outer loop is designed and controlled in state space with an analysis of interdependencies and stability concerns. These optimized margins allow more dynamics in modern systems.