Pilot Induced Oscillation Mitigation for Unmanned Aircraft Systems: An Adaptive Control Allocation Approach

Abstract

This paper proposes an adaptive control allocation method that can make unmanned aircraft systems recover from pilot induced oscillations. Pilot induced oscillations are undesired oscillations due to an unintentional and detrimental coupling between the aircraft and the pilot. These oscillations may be instigated due to disturbances, aggressive maneuvers and actuator saturation. Different from manned aircraft, pilot induced oscillations in unmanned aircraft systems are harder to handle due to communication time delays between the operator and the aircraft. The task of a conventional control allocator is to distribute the control effort among redundant actuators to realize a desired virtual control input. When actuators rate saturate, the difference between the desired and the achieved virtual control input introduces an effective time delay to the system dynamics which causes oscillations. In the proposed approach, instead of minimizing the error between the desired and achieved virtual control inputs, the derivative of this error is minimized which eliminates the introduced time delay effect and damps undesired oscillations. Differently from earlier works conducted by the authors, in this work, the proposed pilot induced oscillation mitigation methodology is developed for systems with parametric uncertainty. In the simulations, it is demonstrated that the proposed approach successfully damps pilot induced oscillations that are instigated by a high gain pilot command.

An Adaptive Human Pilot Model for Adaptively Controlled Systems

“…Finally, regarding the anti-windup term used in (17), and with Assumption 1 satisfied, we define J(t) as…”

“…The field of flight control reconfiguration emerged to address the issue of actuator failures by replacing redundant physical hardware with control algorithms that utilize the remaining control surfaces to compensate for loss of actuator effectiveness [11]. The consideration of such an uncertainty in the early design stage has become a standard approach in adaptive controller design [8], [12]- [15], and in adaptive control allocation methods [9], [16], [17], after its importance is highlighted in early studies such as [18], [19].…”

Discrete Adaptive Control Allocation

“…Thanks to the advances in microprocessors and progress in actuator miniaturization, which leads to actuator cost reduction, over-actuated systems are becoming ubiquitous in engineering applications. Aerial vehicles [3]- [9], marine vehicles [10], [11], and automobiles [12]- [15] can be counted as examples of systems where redundant actuators are employed.…”

A Control Theoretical Adaptive Human Pilot Model: Theory and Experimental Validation

“…Furthermore, in the tasks that require increased attention and focus, humans tend to provide high gain control inputs that can cause undesired oscillations. One example of this phenomenon, for example, is the occurrence of pilot induced oscillations (PIO), where undesired and sustained oscillations are observed due to an abnormal coupling between the aircraft and the pilot [3], [4], [5], [6]. Similarly, automation may fail due to an uncertainty, fault or cyber-attack [7].…”