Reduced Order Control Law Research Articles

Considerations Regarding the Design of a Minimum Variance Control System for an Induction Generator

This paper presents a comparative analysis regarding a self-tuning minimum variance control system of a double-fed induction generator with load and connected to a power system through a long transmission line. A new complex nonlinear model describing this relationship between the induction generator, electrical consumer, transmission line, and power system is designed and implemented to simulate the controlled plant behavior. Starting from a simplified linear model of this complex plant, obtained through linearization of its nonlinear model around an operating point, the minimum variance control law design is performed by minimizing a cost criterion function. The main goal and also the paper novelty consists of the identification of a minimum order of this linearized model used to design a reduced order control law, which can still provide good control performance.

A Generic Model-Based Advanced Control of Electric Power-Assisted Steering Systems

Electric power-assisted steering (EPS) systems have been used to replace traditional hydraulic power steering systems in vehicles. In an EPS system, the assisting steering torque is from an electric motor. In principle, the control of an EPS system involves two aspects: 1) motor torque control to satisfy the torque requirement and 2) steering motion control to yield a satisfied feeling of the driver during the steering process in a disturbed environment. In this paper, a column-mounted steering system is taken as a generic target system to illustrate a model-based approach for advanced steering control design. In particular, we present a two-controller structure proposal for the generic EPS system, addressing motor torque and steering motion, by applying <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> and <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">infin</sub> design methods, respectively. Controller model reduction is also discussed and compared to show that, actually, a reduced-order controller could be applied. This is important for industrial applications because a reduced-order control law costs less in computing resources. Finally, simulation for the EPS control system is discussed and a software-in-loop approach is presented using off-the-shelf software. It is interesting to see that, based on the simulation results, the advanced two-controller design yields superior performance to the one-controller structure for the steering control.

Active Vibration Control for Aircraft Wing

In active vibration control, gust load alleviation and flutter suppression method are studied for aircraft. For this purpose, an aero-servoelastic analysis code was developed using the finite element code MSC/NASTRAN. Moreover, a control law synthesis method was developed and applied to the LQG (linear quadratic Gaussian) method for reduced-order control law design. To validate both aeroservoelastic analysis and the control law synthesis code, the wind tunnel test of gust load alleviation was conducted in a 2 m low-speed wind tunnel of Nagoya Aerospace Systems Works using an aeroelastic wind model equipped with an actively controlled trailing edge surface. Analytical results were compared with the results from tests, and good agreement was obtained for wing acceleration. To estimate the effects of gust load alleviation and flutter suppression, they were applied to a 150-passenger twin-engine commercial airplane. For gust load alleviation, a 46.9% wing bending moment reduction was caused, as well as a flutter suppression of 30.7% flutter speed augmentation.

Modified linear model-following controller for current-source inverter-fed induction motor drives

A modified linear model-following speed controller for current-source-inverter (CSI) fed induction motor drives is proposed in the paper. The proposed controller is designed so that only the measured plant output is used in the feedback loop. Furthermore, a reduced reference model is set to simplify the design without degrading the performance very much. To ensure the stability of the resulting system when the reduced-order control law is applied to the original system, an analysis based on an equivalent feedback system is provided and the stability criteria are derived. Finally, some experimental results are given to demonstrate the effectiveness of the proposed controller.

Reduced-Order Optimal Feedback Control Law Synthesis for Flutter Suppression

A method of synthesizing reduced-order optimal feedback control laws for a high-order system is developed. A nonlinear programming algorithm is employed to search for the control law design variables that minimize a performance index defined by a weighted sum of mean-square steady-state responses and control inputs. An analogy with the linear quadratic Gaussian solution is utilized to select a set of design variables and their initial values. An input-noise adjustment procedure is used in the design algorithm to improve the stability margins of the system. The method is applied to the synthesis of an active flutter-suppression control law for an aeroelastic wind tunnel wing model. The reduced-order control law is compared with the corresponding full-order control law. The study indicates that by using the present algorithm, near optimal low-order flutter suppression control laws with good stability margins can be synthesized.

Design of low-order control schemes using reduction technique

Abstract A new design procedure is presented to obtain a simplified control scheme using the reduction technique. In some practical cases, the optimal control may be required using only a restricted set of state variables. An attempt is made to design a reduced-order control law using only a restricted sot of state variables. The technique is illustrated by an example.