Real-time parameter identification applied to flight simulation

In-flight simulations are normally accomplished using model-following control laws which depend on accurate knowledge of the stability derivatives of the host aircraft. Degraded simulation results if the stability derivatives deviate considerably from their presumed values. Gain scheduling is often used to compensate for plant parameter variations, but this form of open-loop compensation usually requires extensive flight testing for proper fine tuning. An adaptive, fast-sampling control law to compensate for changing aircraft parameters is described. The step-response matrix required for implementation is identified recursively using a technique which does not need special test signals, and which automatically discounts old data depending on the input excitation detected. Tracking fidelity is maintained despite parameter changes which occur abruptly or slowly, and actuator position and rate limiting are discussed. The performance of the resulting system is excellent and demonstrates the relative advantages of adaptive controllers for in-flight simulation