A Constrained Pole Placement Method for Autopilot Gain Scheduling

In some air vehicle autopilot designs, a simple pole placement method is used to obtain autopilot gain formulas. To keep the problem analytically tractable, high order dynamic models (such processing time delay, bending filters, actuator dynamics, etc.) are often neglected in the pole placement process. Unfortunately, the presence of these high order dynamics, in some cases, causes instability if the gain formulas obtained from the simplified model are not modified. Methods of modifying these gain formulas are often heuristic and require engineers to perform enough simulation to determine empirical modifying factors. In this paper, we will show that the latter step of the design process can be avoided when a constrained pole placement method is used. This constrained pole placement method approximates high order dynamic models by simple time delay elements. Gain formulas obtained from this constrained pole placement method usually needs not be modified under the presence of high order effects in the loop.