Q. Single-axis autopilot control system of an aircraft?

Figure (a) shows the block diagram of a simplified single-axis (pitch, yaw, or roll) autopilot control systemwith digital data. The objective of the control is tomake the position of the airframe follow the command signal. The rate loop included here helps to improve system stability. Figure (b) illustrates a digital autopilot control system in which the position and rate information are obtained by digital transducers. Sample-and-hold devices are shown on the block diagram.

While a sampler essentially samples an analog signal at some uniform sampling period, the hold device simply holds the value of the signal until the next sample comes along. Two samplers with two different sampling periods (T₁ and T₂) are shown in Figure(b), which is known as a multirate sampled-data system. If the rate of variation of the signal in one loop is relatively much less than that of the other loop, the sampling period of the sampler employed in the slower loop can be larger. With sampling and multirate sampling, some of the expensive components of the system can be utilized on a time-sharing basis.