【作者】 庞新良；

【导师】 范大鹏；

【作者基本信息】 国防科学技术大学 ， 机械工程， 2007， 博士

【摘要】 机载光电稳定平台系统能隔离机体的运动,稳定光电探测器的视轴,实现对目标的观察和跟踪,在军民用领域有着广泛的应用价值。现有的机载平台大多采用模拟控制,数字控制系统能提高系统综合性能,便于系统调试,采用数字控制方式是平台系统的必然发展方向,系统辨识、控制器设计和多采样率问题的研究是数字控制系统研究的关键问题,有关机载光电稳定平台数字控制的这些关键技术研究是本文的目的。机载光电稳定平台采用陀螺检测惯性空间速度,组成闭环控制实现对机体运动的隔离,利用头盔、视轴与目标轴之间角度偏差的牵引,完成对环境的侦察或目标的跟踪。机载光电稳定平台由俯仰轴和方位轴组成两轴两框架平台系统,主要由机构、电子箱、光电探测器、检测传感器组成。在理论研究方面,被控对象的精确模型是高精度控制系统的首要保证,合理的系统辨识模型有助于我们理解系统的内部结构和工作机制。平台系统由非线性和线性部分组成,本文研究了存在非线性摩擦时,提炼线性部分模型传递函数的问题。对存在摩擦的系统,直接检测被控对象的频率特性将产生较大的误差,采用差分、大幅值的信号激励被控对象,采集被控对象的差分响应来获取频率特性,可基本消除非线性摩擦对频率特性产生的误差影响。采用递阶最小二乘迭代辨识算法对获取的频率特性进行传递函数的辨识,可使传递函数参数在任意初始值情况下收敛至真值,基于此算法的递阶辨识方法可获得平台模型的高精度传递函数。控制策略的选择和控制器的设计是高精度控制系统的关键环节,本文研究了滞后超前校正+模糊控制组成的复合控制器对平台系统进行控制的问题。滞后超前校正控制精度高,模糊控制抗非线性能力强,综合二者优点组成复合控制器,与单纯的滞后超前校正器相比,复合控制器使平台系统具有较高的隔离效果,同时具有平滑的阶跃响应,且能有效抑制外部阻力扰动和非线性摩擦。平台系统采用DSP实现伺服控制算法,属于多采样率控制系统。基于提升、抽样和保持技术,本文研究多采样率反馈控制闭环系统的传递函数和控制器设计问题,矩阵提升传递函数将多采样率闭环控制系统由周期时变系统转换成周期时不变系统,提出滤波保持的概念,指出在设计多采样率控制器时,综合考虑系统带宽、采样频率和控制频率,适当选择滤波保持器用以消除低频采样带来的误差。在实现技术研究方面,采用V/F变换+CPLD计数解决机载平台陀螺速度信号的长距离传输问题,根据电机系统的特性,采用模拟PI电路实现电机的电流闭环控制,使电流闭环的带宽达到1.25kHz。采用DSP实现速度环和位置环的数字控制器,分析并验证了连续域高阶控制器分解成连续域低阶控制器,将低阶控制器离散后进行串联控制,这种实现方式的数字控制器与连续域控制器之间的控制误差,将远小于直接将连续域高阶控制器离散成高阶数字控制器产生的控制误差。在论文的最后,介绍了机载光电稳定平台的实验结果。更多还原

【Abstract】 Airborne electro-optical stable platform can isolate movement and vibration of the airframe, stabilizes the optic axis of the photoelectric detector, realize the observation and tracking for the object. It has comprehensive application value in army and civil field. Most of present airborne platforms are analogic control system, digital control system can improve the system general performance, digital control is the development direction of platform systems, digital control has especial techonoly, this paper focus on researching the key technologies of digital control of airborne electro-optical stable platform.By gyro detecting inertia velocity of platform to form close-loop, the airborne platform realizes the isolation to the movement and vibration of the airframe. By traction of the helmet or the angle deviation between optical axis and object axis, platform realizes the reconnaissance or tracking. Airborne electro-optical stable platform is two-axis-two-frame platform system of pitch axis and azimuth axis, its main component are mechanism, electronic box, photoelectric detector and sensor.On the aspect of theory, accurate model of the control object is the primary guaranty of high accuracy control system, reasonable system identification model let us understand system inertia structure and working mechanism. Platform system makes up of linear part and nonlinear part, this paper research as nonlinear friction existing, how to get the transfer function of linear part. To the system existing friction, there will be error if directly detect the frequency characteristic of the control object. If excite the servo control object by difference and large amplitude signal and collect the difference response, then get the frequency characteristic, this way can basically eliminate the error. The hierarchical least square iterative (HLSI) identification algorithm can converge the model transfer function parameters to their actual value. Basing on the HLSI the hierarchical identification way can get the high accuracy transfer function of airborne electro-optical stable platform system.Control strategy selection and controller design are key problems of the high precision control system. This paper research the platform control problem by lead-lag + fuzzy complex controller. The lead-lag control system has high accuracy, and the fuzzy controller has the ability of resist to nonlinear, the complex controller has their two merits, so platform system has high isolation performance, smooth step response and the better ability of external perturbation rejection and nonlinear friction rejection.Platform system use DSP to realize the servo controller, it is multi-rate sample control system. Based on lifting, sampling and holding technique, this paper research the transfer function of the feedback control multi-rate close-loop system and controller design, the matrix lifting transfer function changes the multi-rate close-loop system from time-variant system to time-invariant system. Present the concept of filter-holding, and point out that filter design can reject the vibration by sampling, the design of filter should consider the system frequency width, sample frequency and the control frequency.In the way of realization technology, the way of V/F transform + CPLD counter is used to solve the long-distance transmission of the gyro weak signal. The current close-loop is realized by PI analogy circuit, the current close-loop bandwidth is 1.25kHz. DSP is used to realize digital controllers of velocity-loop and position-loop. Analyze and validate that dividing high-level continue controller to several low-level controllers, then discretize the low-level controllers to form series controller can depress the discretization control error. In the end, introduce the experiments and their result.更多还原