An interval-consistency-based hybrid optimization algorithm for automatic loop shaping in quantitative feedback theory design

A computationally efficient method for automatic synthesis of quantitative feedback theory (QFT)-based robust controllers is proposed. The synthesis problem consists of obtaining a fixed structure QFT controller that ensures stability and achieves the performance specifications in the presence of disturbances and parametric uncertainty. The proposed method uses an interval consistency technique (hull consistency HC4) and hybrid optimization. The HC4 method is used to remove inconsistent values, which are not part of the solution in the controller parameter regions. The hybrid part incorporates interval global optimization and nonlinear local optimization methods. The proposed algorithm is illustrated by means of two examples. The first one concerns the longitudinal motion control of an aircraft system (flexible), while the second one describes the experimental study of the position control of the industrial plant emulator setup. The robustness of the designed control system for emulator setup is validated by adding extra weights on the load disk in the presence of disturbances. The experimental results show that the designed controller satisfies the robust performance specifications

A New Anti-Windup Compensator Based on Quantitative Feedback Theory for an Uncertain Linear System with Input Saturation

This paper devotes to the robust stability problem for an uncertain linear time invariant (LTI) feedback system with actuator saturation nonlinearity. Based on a three degree of freedom (DOF) non-interfering control structure, the robust stability is enforced with the describing function (DF) approach for an uncertain LTI system to avoid the limit cycle. A new type of anti-windup (AW) compensator is designed using the quantitative feedback theory (QFT) graphical method, which results in a simple design procedure and low-order AW control system. One of the most significant benefits of the proposed method is free of the non-convexity (intractable) drawback of the linear matrix inequality (LMI)-based approach. The analysis conducted on the benchmark problem clearly reveals that the proposed QFT-based anti-windup design is able to handle both saturation and uncertainty in a very effective manner

A New Scheduling Quantitative Feedback Theory-Based Controller Integrated with Fault Detection for Effective Vibration Control

In this work, a new integrated fault detection and control (IFDC) method is presented for single-input/single-output systems (SISOs). The idea is centered on comparing the closed-loop output between the faulty system and fault-free one to schedule/switch the feedback control once the fault occurs. The problem addressed in this work is the output disturbance rejection. The set of feedback controllers are designed using quantitative feedback theory (QFT) for fault-free and faulty systems. In the context of QFT-based IFDC, the proposed active approach is novel, simple, and easy to implement from an engineering point of view. The efficiency of the proposed method is assessed on a flexible smart structure system featuring a piezoelectric actuator. The actuator and sensor faults considered are the multiplicative type with both fixed and time-varying magnitudes. In the fixed magnitude fault case, the actuator/sensor output delivering capability is reduced by 50% (multiplying a factor of 0.5 to its actual output), while in the time-varying magnitude case, it becomes 60% to 50% for a particular time interval. In both cases, the proposed control method identifies the fault and activates the required controller to satisfy the specification with less control effort as opposed to the passive QFT design featured by faulty system design alone

Simultaneous automated design of structured QFT controller and prefilter using nonlinear programming

International audienc

Robust controller and pre-filter design using QFT and interval constraint techniques

International audienceno abstrac