Study on Control Strategies of Adjustable Blade Angle Control System

Abstract

In this article, a type of adjustable blade angle control system was designed. The main role of the system was to achieve the function which made the blade angle follow with the change of the signal input. The article indicated the working principle of the adjustable blade angle control system combined with the relative math model. Aiming to the control target, a self-adapting fuzzy PID controller was designed. Mtalab7.0 was applied to carry out simulation and analysis on the cases that the step signals and sine signals were added to the controller, and it was validated that the self-adapting fuzzy PID controller had a good quality of dynamical characteristics, static characteristics and robust characteristics. Introduction To improve the aeroengine’s performance, widen the working range, the designers developed adjustable blade angle control technology. Nowadays the adjustable blade technology mainly achieved its blade angle following the given signal to carry out follow-up control function through adjustable blade angle control system. This article aimed to the requirements of aeroengine to the blade angle control, developed a set of adjustable blade angle control system. To realize the requirement for the adjustable blade technology as a fast and accuracy respond, this system took hydraulic control into use. Hydraulic control played a very important role in military affairs, aviation and industrial automation. In practical applications, general requirement was that the controller had fast respond and small overshoot characteristics. Considering that there were some uncertain factors in the hydraulic servo system, the time-changing characteristics of some parameters such as hydraulic nature frequency of the system, hydraulic damping ratio as well as nonlinearity of the servo valves and disturbance of exoteric load, traditional PID controllers could hardly satisfy the control’s need, sometimes even not able to be used, while self-adapting fuzzy PID controller was able to simplify the complexity of system design in an extreme degree, which was especially suitable to this kind of nonlinear system control. For this reason this system applied self-adapting fuzzy PID controller as governor [1] [2]. This article applied MATLAB7.0 to carry out simulation and analysis for the case with no disturbs to validate that the self-adapting fuzzy PID controller had better dynamical characteristics, static characteristics and robust characteristics. By practical application, the validity of the designed self-adapting fuzzy PID controller was proved and was able to satisfy the requirements of blade adjusting during the process of the tests. The working principle of the angle control system The control principle of the adjustable blade angle control system was shown in Fig.1. The computer exported the control signal to the A/D conversion module through the RS232 port and transformed it into voltage signal. The voltage signal and signal fed back by the displacement transducer were compared in the servo amplifier, the deviation signal was transformed into current signal after amplified, and transferred to the loop of the electro-hydraulic servo valve, in this way the opening control of the servo valve was achieved. After the servo valve opened, hydraulic oil 5th International Conference on Computer Sciences and Automation Engineering (ICCSAE 2015) © 2016. The authors Published by Atlantis Press 442 flowed into the actuating cylinder through the valve, made the actuating cylinder move and then achieved angle adjusting. The displacement transducer fixed on the actuating cylinder was used to measure the displacement of the actuating cylinder, and feedback to the servo amplifier. Fig.1. Control principle figure The mathematical model of angle control system Adjustable blade angle control system applied hydraulic pressure to control a pair of hydraulic actuating cylinders, this system included: servo amplifier, electro-hydraulic servo valve, displacement transducer, hydraulic pressure actuating cylinder, etc. The math models for these components were built up as followed: Servo amplifier When using current feedback amplifier, the output current 1 I and input voltage 1 U from the power amplifier were approximately proportioned and could be seen as scaled loop, the math model was: 1 1 1 ( ) ( ) I s K U s = (1) In the formula 1 K was servo amplifier increment, the enlargement factor of the servo amplifier 1 K =10mA/V. Electro-hydraulic servo valve Generally servo valve used current increment I ∆ as input, and no-load flow 0 Q as output, when the working frequency of the servo valve was nearly the same as hydraulic pressure natural frequency, the servo valve could be seen as a second order surge loop: