Jiqiang Wang

Nonlinear Control of Aircraft Engines Using a Generalized Gronwall-Bellman Lemma Approach

Model-based design has attracted much attention in the field of aircraft engine control in recent years. As an aircraft engine is a complicated thermomechanical system, it can only be represented by a nonlinear process model. This necessitates the study of the nonlinear control techniques. Based on our recent results, this paper proposes a novel design approach based on a generalized Gronwall-Bellman lemma. Important results are obtained on bounding behavior of the nonlinear states of the engine. The proposed method is easy to design and tune with the appealing feature of enlarging the feasible control envelope. Finally, a simulation study is provided to validate the effectiveness of the control design approach.

Sensitivity Analysis and Experimental Research on Ball Bearing Early Fault Diagnosis Based on Testing Signal From Casing

The ball bearings of an aero-engine are key parts that frequently fail, and it is very important to effectively carry out fault diagnosis of the ball bearings. However, in the present research work, the ball bearing faults characteristics are extracted mainly from the bearing house signals, it is well known that usually only the casing signals can be measured in practical aero-engine test, and the ball bearing faults characteristics will greatly weaken after transmitting to the casing from the bearing house, therefore, it is very important to extract the fault characteristics of ball bearings from casing vibration signals for the ball bearing fault diagnosis in the practical aero-engine. In this study, simulation experiments for ball bearing faults are conducted using two rotor experimental rigs with casings. In addition, by means of the impulse response method, the transfer characteristics from the ball bearings to casing measuring points are measured, and a sensitivity analysis is performed. Faults are created on the inner ring, outer ring, and ball of the ball bearings in the two experimental rigs. The ball bearing experiments are carried out, and the fault features are extracted by means of a wavelet envelope analysis. The experimental results indicate that, with high connection stiffness between the bearing house and the casing, there is little vibration attenuation. However, with low connection stiffness, the vibration attenuation is great. After the impulse vibrations caused by the ball bearing faults are transmitted to the casing, the casing vibration is very weak and is often submerged in other signals. However, the ball bearing fault characteristic frequencies can still be effectively extracted from the weak casing vibration signals by using a wavelet envelope analysis. The research results in this study provide an experimental basis for a ball bearing fault diagnosis based on a casing test signal from a practical aero-engine. [DOI: 10.1115/1.4027926]

Static feedback stabilization of nonlinear systems with single sensor and single actuator.

This paper considers a single sensor and single actuator approach to the static feedback stabilization of nonlinear systems. This is essentially a remote control problem that is present in many engineering applications. The proposed method solves this problem that is less expensive to implement and more reliable in practice. Significant results are obtained on the design of controllers for stabilizing the nonlinear systems. Important issues on control implementation are also discussed. The proposed design method is validated through its application to nonlinear control of aircraft engines.

Model-based Acceleration Control of Turbofan Engines with a Hammerstein-Wiener Representation

Abstract Acceleration control of turbofan engines is conventionally designed through either schedule-based or acceleration-based approach. With the widespread acceptance of model-based design in aviation industry, it becomes necessary to investigate the issues associated with model-based design for acceleration control. In this paper, the challenges for implementing model-based acceleration control are explained; a novel Hammerstein-Wiener representation of engine models is introduced; based on the Hammerstein-Wiener model, a nonlinear generalized minimum variance type of optimal control law is derived; the feature of the proposed approach is that it does not require the inversion operation that usually upsets those nonlinear control techniques. The effectiveness of the proposed control design method is validated through a detailed numerical study.

LIDAR-assisted wind turbine gain scheduling control for load reduction

A gain-scheduled feedforward controller employing pseudo-LIDAR wind measurement is designed to augment the baseline feedback controller for wind turbine load reduction during above rated operation. The feedforward controller is firstly designed based on a linearised wind turbine model at one specific wind speed, then expanded for full above rated operational envelope with gain scheduling. The wind evolution model is established using the pseudo-LIDAR measurement data which is generated from Bladed using a designed sampling strategy. The combined feedforward and baseline control system is simulated on a 5MW industrial wind turbine model developed at Strathclyde University. Simulation results demonstrate that the gain scheduling feedforward control strategy can improve the rotor and tower load reduction performance for large wind turbines.

Finite-Time Regulation of Two-Spool Turbofan Engines With One Shaft Speed Control

Nonlinear control of aircraft engines has attracted much attention in consideration of the inherent nonlinearity of the engine dynamics. Most of the nonlinear design techniques, however, require the information from the rotational speeds of both high pressure compressor and fan. This is not desirable from engine health management perspective and this paper proposes a single sensor measurement and single actuator control approach. The proposed method can provide fast regulation of engine speed in a finite time in comparison with conventional infinite time stability. Important results are obtained on both controller design and disturbance tolerance. Numerical examples are provided for validation of the proposed finite time controller, demonstrating fast regulation property and remarkable disturbance tolerance capability.

WAN networked control systems implemented by computer control: Sampled-data synthesis: Dedicated to academician Si-Ying Zhang, Chinese academy of sceinecs, a great scientist and teacher

A novel discrete-time synthesis for WAN-based computer control of networked control systems with a class of nonlinear plants is developed. Such a networked control systems are assumed to comprise an affine nonlinear plant process to be controlled and a linear digital controller in presence of WAN induced time delays. It can be viewed as a typical hybrid control system with network-induced delays. Sufficient conditions for guaranteed exponential closed-loop stability have been derived via the proposed discrete-time synthesis. These novel results have been tested by application to an illustrative example from the literature. The obtained numerical and simulation results have demonstrated considerable control effectiveness as well as quality transient performance for the class of affine nonlinear plant system models.

Turbofan Engine Modelling and Control Design using Linear Quadratic Regulator (LQR)

--------------------------------------------------------ABSTRACT----------------------------------------------------------There are many applications in which gas turbine engine is used today, including aircraft propulsion for both commercial and military purposes, and power generation and in all these Control systems technology has played a fundamental role in enhancing performance. Modelling plays a significant role in the development of the entire engine system performance. This paper investigated Linear Quadratic Regulator (LQR) model-based control method to obtain estimates of performance parameters. The main control variable selected is the fuel flow to control the rotational speed of high-pressure spool speed of the turbofan engine. Firstly a suitable mathematical model of the engine is developed in MATLAB Simulink environment with both the intercomponent volume and the constant mass flow methods used. Equations of the mass flow rate and the torque balance are incorporated in the steady state and dynamic state of the thermodynamic engine model. This represents the engine model by a set of first-order differential and algebraic equations and a linearized model is extracted for the analysis and design of a controller by LQR. It is demonstrated that LQR based controllers can perform better than conventional PID controllers. The settling time, rise time and maximum overshoot for LQR based controller are all less than those for PID based controller. The input also changes more accurately for LQR than the PID controller compared.

Complexity of constrained switching for switched nonlinear systems with average dwell time: Novel charecterization

In so far developed theory of switched systems is largely based on assuming certain small but finite time interval termed average dwell time, which represents a constraint even when extremely small. Thus currently most of it appears characterized by some slow switching condition with average dwell time satisfying a certain lower bound. However, in cases of nonlinear systems, when the switching seizes to be slow there may well appear non-expected complexity phenomena of particularly different nature. A fast switching condition with average dwell time satisfying an upper bound is explored and established. Thus the theory is extended by shading new light on the underlying, switching caused, system complexities. A comparison analysis of these innovated characterizations via slightly different overview yielded new results on the transient behaviour of switched nonlinear systems, while preserving the system stability. The multiple-Lyapunov functions approach is the analysis framework

A Comparative Study on Optimal Transient Control of Aircraft Engines

Sequential quadratic programming has been widely used in the optimization of transient control of aircraft engine. On the other hand, the study of nonlinear optimization theory and method has been made great advance in recent years, of which active set method is one of the effective measures. In this article, the two algorithms are used to optimize the inputs based on one turbofan engine model. Results from the simulation comparisons of the two algorithms, advantages and disadvantages are given.