Pole Placement Designs
In the previous chapters model reference control based adaptive actuator failure compensation schemes were developed for linear time-invariant (LTI) plants with unknown actuator failures. Model reference adaptive control (MRAC) requires that the controlled plant is minimum phase. However, many physical plants are nonminimum phase, and the adaptive control schemes based on MRAC cannot be applied to such systems. For example, the linearized aircraft model may contain both minimum phase and nonminimum phase control channels. For a Boeing 737-100 aircraft, in the case of cruise flight, the control channels from aileron, spoiler, and rudder to roll rate are all nonminimum phase. In the lateral motion model of the DC-8 aircraft, the control channel from aileron to side-slip angle is also nonminimum phase. To compensate for actuator failures in nonminimum phase plants, effective control schemes such as pole placement are needed. In this chapter, we present pole placement based actuator failure compensation control designs for systems with unknown actuator failures, which are applicable to both minimum phase and nonminimum phase LTI plants. In Section 6.1, we formulate the control problem. In Section 6.2, we present a nominal pole placement control scheme for actuator failure compensation. In Section 6.3, we develop an adaptive control scheme for the case when both plant parameters and failure parameters are unknown. In Section 6.4, we present simulation results to verify the desired adaptive system performance.
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