Automatic Rotor Balancing System Based On The Principle Of Fault Self-Recovery Regulation

In this dissertation, a novel kind of active rotor balancing system, which is designed under the guidance of the principle of Fault Self-recovery Regulation, is presented. The research project focuses especially on the balancing head, the key part of the automatic balancing system, and a new kind of continuously dripping balancing head is developed. The new balancing head has a high correction capacity, high reliability, and it is easy and cheap to make. The basic principle of this balancing head is discussed and its dynamic mathematic model is built. The calculating method of some of the major design performance parameters, e.g., correction capacity, adjusting speed, control accuracy, is introduced, and several derived versions of balancing head applicable to different situations are also designed. To avoid the possible liquid discharge excited vibration, the discharge is simply split into2streams that go to opposite axial directions. Besides, the selection of working liquid, and the hardware and software for rotating speed change compensation and other issues are discussed in this dissertation. And also. the fail safety issue concerning the new balancing head is investigated and a design that uses Magneto-Rheological Fluid (MRF) is introduced, along with its magnetic circuit design.To boost the overall reliability of the new active rotor balancing system, a fault-tolerant Pulse Code Modulation (PCM) How control system is developed. This kind of flow control device mimics bio-compensation mechanism. When one or more of its turn on/off valves fail, it can automatically perform a logic reconstruction using the remaining turn on/off valves and add a Pulse Width Modulation (PWM) signal onto the PCM signal to keep the flow adjusting accuracy and keep flow rate wave within allowable limit, while its flow adjusting range may drop. Through automatic compensation, the flow control device can maintain good controllability even when there exist some faults, thus to avoid sudden loss of control, or even accident, and leave some time margin for planned shutdown or maintenance.This dissertation put forth some concrete realizations of the said flow control device. A stochastic fault model is built and applied to analyze its life distribution using a Monte-Carlo approach. The simulation result indicates that after adopting this self-recovery regulation method, there is a19.6%～47.9%increase of life expectation for a relatively unstable control situation, and a15.2%～22.4%increase of life expectation for a relatively stable control situation when the minimum remaining flow rate adjusting range is93～60percent of original range. Under most cases, the extra life after there is a fault alarm should be sufficient to allow a more planned and less hurried shutdown. This kind of flow control device can be used as general-purpose control valve for the flow control in continuous process, aircraft control and the like. It can promote the system reliability and reduce costs caused by emergency shutdown, and avoid further confusions and accidents caused by emergency shutdown.The control simulation of a single head active balancing system on a rigid rotor is carried out to test its control properties. The basic control algorithm comprises of followings:firstly, the unbalance vector is projected to2orthogonal axes; and secondly, along each axis, the generalized object is approximated as a link with a first order delay and a pure delay and controlled using a controller; and thirdly, the outputs of the2controllers are then combined into a vector again and projects to2of the3directions of the3chambers’unbalance, to control the opening of the3flow control valves so as to adjust3liquid injection streams to form a close loop control. In simulative study, by using conventional PI control with calculated parameters, good control quality can be obtained for high-magnitude step disturbance, and the control quality is slightly worse for low-magnitude step disturbance. On the other hand, when using a PI controller with smaller gain, good control quality can be obtained for low-magnitude step disturbance and the control quality is slightly worse for high-magnitude step disturbance, and the sine disturbance response get worse dramatically. A PI&Bang-Bang hybrid controller is also tested and it yields poorer performance than the first PI controller. Therefore, for most cases using standard PI control and’standard’control parameters might be a good choice, though actually selection should highly depend on the characters of actual disturbances and the requirement and weights for the main control quality parameters during the transient period of adjusting.Above mentioned balancing head control algorithm can also be used as a low level module in the2-headed balancing of rigid rotor, or the balancing of a multi-span flexible rotor with a plural of correction planes and measurement planes. Although in these cases upper control block based on balancing equation, influence coefficient method or modal balancing method must be adopted. The head control algorithm has a good stability, but the adjusting speed is relatively low when the amplitude of disturbance is high, due to the volume property of the balancing head itself. If a high steady-state accuracy is not stressed, or the rangerability of the control valve can be improved, then the adjusting speed can be increased through increasing the maximum liquid injection speed. The active balancing system, which bases upon following2patents applications:continuously dripping balancing head, and self-compensating flow control device, is cheap, reliable, and has a high capacity and wide working temperature range. Its adjusting speed is sufficient for most applications. In future industrial practice, it can serve as a good option among other kinds of automatic balancing systems according to the nature of unbalance disturbance and the importance of each of the control performance parameters. The system can be expected to be used in more and more fields through further industrial tests and improvements.