Target Feedback Loop Research Articles

On the Properties of Augmented Open-Loop Stable Plants Using LQG/LTR Control

In this technical note are presented new properties on the application of the continuous- and discrete-time LQG/LTR control methodology when an open-loop stable process plant is augmented by integrators and a specific choice of design parameters is made. It is shown that the target feedback loop transfer matrix is made equal to a diagonal transfer matrix of integrators with specifiable gains, guaranteeing equal and decoupled responses in each of the system's outputs.

A New Look at the Target Feedback Loop Parameterization for $$\mathcal {H}_{\infty }$$ H ∞ /LTR Control

In this paper, a new approach on the target feedback loop (TFL) parameterization for the \(\mathcal {H}_{\infty }\)/loop transfer recovery (LTR) control is presented. The proposed procedure, which is based on a similarity transformation, allows to obtain a first-order system behavior through a particular shaping of the TFL sensitivity in terms of singular values. Furthermore, the proposed methodology makes possible to augment the design plant model with any stable real-finite pole, and not only a pole at the origin, as classical TFL parameterization procedures suggest. Thus, the proposed methodology should gather great attention by LTR-based control applications in which the use of integrators in the open-loop is undesirable or even prohibitive. Additional properties are derived if the design plant model does not have poles at the open right-half plane. Since \(\mathcal {H}_{\infty }\)/LTR control can be viewed as a generalization of well-known LQG/LTR control, the proposed methodology in this paper to shape the TFL can be properly extended to the LQG/LTR control.

机械手臂之LQG/LTR最佳控制综合设计

本研究综合计算扭矩法与LQG/LTR对非线性机械手臂系统进行多变量强健控制设计，解决存在于系统内部的不确定性与受到随机干扰情况下的非线性机械手臂系统之控制设计问题，使得非线性机械手臂控制系统具有良好的强健性与满足性能要求。文中首先使用计算扭矩法对非机械手臂系统中各项的估计值进行控制律的设计与回授线性化，并使用变异渐进法对回授系统进行适当的加权扩增；接着使用LQG/LTR设计，使得输出回授控制器(output feedback controller)能够趋近于预先设计的目标回授回路(target feedback loop)。至于非线性机械手臂闭回路系统在形成Lu’re-type问题后，可讨论非线性项之稳定性容许在一定的上界与下界，根据多变量圆稳定准则理论(multivariable circle criterion)探索此控制器之强健性能。文末则以非线性机械手臂系统为范例，进行计算机仿真，验证控制器的有效性与可行性。 In this thesis, the multivariable robust control of nonlinear manipulator systems is based on the compute torque method and the LQG/LTR design procedure was proposed. This controller is able to handle the system that have modeling errors and external disturbances while it keeps the close-loop system robustness and satisfied the prescribed performance. In this research, the computed toque method is applied to design the proposed control law to form the main control structure by using the benefit of its feedback linearization strategy. The error dynamics of the plant is then formulated to the standard H2/H∞ control problem, which is easy to be applied by the LQG/LTR design procedure to find the optimal control gain and observer gains in the process of matching the target loop. With regard to the non-canceling nonlinear terms, the closed-loop system is formulated to the Lu’re-type problem form with sector-bounded uncertainties, which is then analyzed by the Multivariable Circle Criterion to discuss the stability and robustness. To verify the feasibility of proposed controller, one example with various external disturbances and parameter uncertainties is made and its computer simulation result shows the efficiency and feasibility of the proposed design methodology.

Optimal control design of fuel processing system by linear quadratic Gaussian and loop transfer recovery method

This paper presents an optimal control system which consists of both feedforward and state‐feedback controllers designed using a well‐developed linear quadratic Gaussian and loop transfer recovery (LQG/LTR) method for a fuel processing system (FPS). This FPS uses natural gas as fuel and reacts with atmospheric air through a catalytic partial oxidation (CPO) response. The control objective is focused on the regulatory performance of output vector in response to a desired stack current command in face of load variation. First, a Kalman filter is designed to provide an optimal estimation of state variables and to shape the target feedback loop function. And then an optimal two‐degree‐of‐freedom controller is designed subject to a linear quadratic performance index in the LTR process. Finally, the numerical simulations of compensated FPS reveal that the proposed method achieves better performance and robustness properties than presently accepted methods, in both time‐domain and frequency‐domain responses.

Multiobjective Target Feedback Loop / Loop Transfer Recovery (TFL/LTR) design with application to aircraft lateral control in high incidence regime

Target Feedback Loop / Loop Transfer Recovery (TFL/LTR) synthesis and multiobjective optimization are combined to design robust and well performing controllers in a most general sense. A TFL/LTR synthesis based on quadratic stabilization is used to efficiently synthesize robustly stabilizing controllers. Multiobjective optimization is used to tune synthesis parameters for which the TFL/LTR controller yields good performance in addition to robust stability. The technique is demonstrated in the design of a lateral controller for a high performance aircraft in high incidence regime.

Scan loop control design for a spin-stabilised seeker

A scan loop model for a spin-stabilised seeker is introduced, which includes gyrodynamics with direct- and cross-spring constants for considering the autoerection effect of the gyro. The LQG/LTR and H∞ controllers are designed for the seeker scan loop system which has model uncertainty and is subject to external disturbances. The performance of LQG/LTR controller can be improved by obtaining uniform singular values over all frequencies for the target feedback loop. The H∞ controller is designed in the framework of the standard H∞ optimisation problem with model matching. The proposed H∞ method can reflect not only frequency domain specifications but also time domain ones, such as transient response characteristics and multivariable interaction between output channels, differently from the mixed sensitivity problem. It is shown that the designed LQG/LTR and H∞ controllers offer good performance and robustness properties, and both controllers are very effective in the seeker scan loop system.