This paper proposes a novel min-max control scheme for aircraft engines, with the aim of transferring a set of regulated outputs between two set-points, while ensuring a set of auxiliary outputs remain within prescribed constraints. In view of this, an optimal augmented monotonic tracking controller (OAMTC) is proposed, by considering a linear plant with input integration, to enhance the ability of the control system to reject uncertainty in system parameters and ensure no crossing limits. The key idea is to use the eigenvalue and eigenvector placement method and genetic algorithms to shape the output responses. The approach is validated by numerical simulation. The results show that the designed OAMTC controller can achieve a satisfactory dynamic and steady performance and keep the auxiliary outputs within constraints in the transient regime.
A new control scheme is proposed for aircraft engines, where the object is to transfer a regulated output (called main output) between two set-points, with the additional requirement that a set of outputs (called auxiliary outputs) remains within prescribed ranges. According to the prior outcomes, no assurance exists to protect output limits in transient regime by use of a traditional min-max scheme with linear compensators. To achieve a satisfied control performance for a corresponding output, each limitation loop is design separately. However, some auxiliary outputs still exceed their limits when other loop regulators are active or overshoot occurs. To overcome this problem, a linear matrix inequalities (LMI) approach is developed by considering the limit values in regulator design of other loops and the condition for no overshoot of auxiliary outputs. Finally, practical applicability is further demonstrated by numerical simulation. The results show that the designed controller can achieve a satisfactory dynamic and steady performance and keep the auxiliary outputs within constraints.
To accomplish the limit protection task, the Min-Max selection structure is generally adopted in current aircraft engine control strategies. However, since no relationship between controller switching and limit violation is established, this structure is inherently conservative and may produce slower transient responses than the behavior by engine nature. This paper proposes an output-based limit management strategy, which consists of the safety margin module and the parameter prediction module to monitor system responses, plus the switching logic to govern switches between the main controller and limiters, and, in this way, a faster transient performance is achieved, and the limit protections in transient states become more effective. To realize smooth switching control, the linear-quadratic bumpless transfer method is developed. The design principle of the multi-loop switching control and bumpless compensator is detailed, and the effect-on limit protection control performance-of the design parameters in the safety margin and parameter prediction modules are also analyzed. The proposed approach is tested using simulations covering the whole flight envelope on the nonlinear component-level model of a turbofan engine, and the superiority over the Min-Max architecture is also validated.
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