模糊理论在数控铣床加工中的应用研究

基于对数控铣床加工过程智能优化与提高加工效率的目的,改变传统的数控铣床加工过程中加工参数一成不变情况。本文从加工过程中,人的思维逻辑作用出发,选定模糊理论作为调整加工参数的方法设计一个能够自动调整伺服电机进给速度的模糊控制器,实现伺服电机的恒功率加工,提高铣削加工效率。并结合仿真手段对模糊控制器的控制作用进行仿真分析。找到一个合适的进给速度,对模糊控制器在数控铣床实际加工中的应用提供一个参数指导。     

Robust and fault-tolerant linear parameter-varying control of wind turbines

High performance and reliability are required for wind turbines to be competitive within the energy market. To capture their nonlinear behavior, wind turbines are often modeled using parameter-varying models. In this paper we design and compare multiple linear parameter-varying (LPV) controllers, designed using a proposed method that allows the inclusion of both faults and uncertainties in the LPV controller design. We specifically consider a 4.8 MW, variable-speed, variable-pitch wind turbine model with a fault in the pitch system.We propose the design of a nominal controller (NC), handling the parameter variations along the nominal operating trajectory caused by nonlinear aerodynamics. To accommodate the fault in the pitch system, an active fault-tolerant controller (AFTC) and a passive fault-tolerant controller (PFTC) are designed. In addition to the nominal LPV controller, we also propose a robust controller (RC). This controller is able to take into account model uncertainties in the aerodynamic model.The controllers are based on output feedback and are scheduled on an estimated wind speed to manage the parameter-varying nature of the model. Furthermore, the AFTC relies on information from a fault diagnosis system.The optimization problems involved in designing the PFTC and RC are based on solving bilinear matrix inequalities (BMIs) instead of linear matrix inequalities (LMIs) due to unmeasured parameter variations. Consequently, they are more difficult to solve. The paper presents a procedure, where the BMIs are rewritten into two necessary LMI conditions, which are solved using a two-step procedure.Simulation results show the performance of the LPV controllers to be superior to that of a reference controller designed based on classical principles.     

基于直线电机的数控机床驱动控制技术

针对传统传动链中作为动力源的电动机的不足,提出了直线电机。分析了直线电机原理、特点,介绍了基于直线电机的驱动控制技术。通过对比传统控制技术、现代控制技术、智能控制技术优缺点,提出了采用直线电机位置控制器解决在数控机床中活塞车削数控系统的响应和精度问题。设计采用了PC机与开放式可编程运动控制器构成数控系统。结果表明,利用直线电机结构简单、运动平稳、噪声小,运动部件摩擦小、磨损小、使用寿命长、安全可靠等特性,采用直线电机的开放式数控系统使数控机床驱动控制技术获得新发展。     

A linear motor damper for vibration control of steel structures

A hybrid mass damper based on the linear motor principle is developed to suppress structural vibration. We will call it a linear motor damper in this paper. This paper deals with the design, analysis, and manufacture of the linear motor damper. It consists of the NdFeB permanent magnets, a coil-wrapped nonmagnetic hollow rectangular structure, an iron core, mechanical springs, and so on. It is designed to be able to move the auxiliary mass of 1500 kg, up to ±250 mm stroke. A series of performance tests for the linear mass damper with H_∞ robust controller are carried out on a steel frame structure. Through performance tests, it is confirmed that the developed hybrid mass damper has reliable feasibility as a control device for structural control. In addition, the linear motor damper is more economical than both hydraulic and electric motor driving mass damper with respect to simple structure and low maintenance cost.     

Gain-scheduled robust control for lateral stability of four-wheel-independent-drive electric vehicles via linear parameter-varying technique

This paper proposes a robust gain-scheduled H_∞ controller for lateral stability control of four-wheel-independent-drive electric vehicles via linear parameter-varying technique. The controller aims at tracking the desired yaw rate and vehicle sideslip angle by controlling the external yaw moment. In the design of controller, uncertain factors such as vehicle mass and tire cornering stiffness in vehicle lateral dynamics are represented via the norm-bounded uncertainty. To address the importance of time-varying longitudinal velocity for vehicle lateral stability control, a linear parameter-varying polytopic vehicle model is built, and the built vehicle model depends affinely on the time-varying longitudinal speed that is described by a polytope with finite vertices. In order to reduce conservative, the hyper-rectangular polytope is replaced by a hyper-trapezoidal polytope. Simultaneously, the quadratic D-stability is also applied to improve the transient response of the closed-loop system. The resulting gain-scheduling state-feedback controller is finally designed, and solved utilizing a set of linear matrix inequalities derived from quadratic H_∞ performance and D-stability. Simulations using Matlab/Simulink-Carsim® are carried out to verify the effectiveness of the proposed controller with a high-fidelity, CarSim®, full-vehicle model. It is found from the results that the robust gain-scheduled H_∞ controller suggested in this paper provides improved vehicle lateral stability, safety and handling performance.     

一类区间控制系统鲁棒绝对稳定性的LMI方法

本文对于区间Lurie控制系统，基于区间矩阵的等价描述和S-过程，构造了关于Lurie型Lyapunov函数中正定矩阵和积分项系数等自由参数的线性矩阵不等式(LMI)，通过LMI的解构造的Lyapunov函数来保证系统的鲁棒绝对稳定性，不必选择和调整参数。不仅讨论了无穷扇形角的情形，而且还讨论了有限扇形角的情形，所获得的结果适用于系统具有多个非线性执行机构的情形。最后给出一个实例说明本文方法的有效性，并通过实例分析了扇形角的大小与鲁棒稳定度的关系。     

Finite element analysis of the cogging force in the linear synchronous motor array for the Thirty Meter Telescope

In this paper, a finite element analysis of the cogging force generated by an array of linear synchronous motors (LSM) moving on a curvilinear track is presented. This system is under consideration as the driving system for the two main axes of the proposed Thirty Meter Telescope that will be built in Mauna Kea, Hawaii. The main objective of this work is the quantification of the effects of the curvilinear track of LSM arrays on the cogging force. The finite element analysis is carried out using planar cross sections, and the results found are used to find an approximate solution for the three-dimensional model. The results show that the presence of the curvilinear-configured track increases the cogging force of a single LSM significantly, while the presence of the array of LSMs interacts in limiting the increase in the cogging force. A geometric optimization in regards to the relative positions of the LSMs along the curvilinear tracks is subsequently carried out in order to reduce the total cogging force.