| A large external disturbance coupled with a rate-limited control surface can cause system divergence. The X-50A Canard Rotor/Wing (CRW) Advanced Technology Demonstrator (ATD) has regions of its flight envelope that are characterized by a lower tolerance to wind gusts. The aircraft model diverges when the elevons are rate-limited for a prolonged period of time. The goal of this research is to increase the tolerance of the system to external disturbances. Modifications to the control laws and the aircraft model are tested using simulations to improve the transient response. These methods include: (1) increasing elevon rate limits, (2) reducing pitch loop gain, (3) limiting pitch angle error, (4) disabling the outer vertical control loop, and (5) elevon rate-limiter phase compensation. Methods (1) through (4) resulted in improved system response to gusts. The best improvement can be realized by implementing a "turbulence switch" and lowering the gain of the vertical loop. |
