1、外文原文：Feedback linearization based control of a rotational hydraulic drive Control Engineering Practice,Volume 15, Issue 12,December 2007, Pages 1495-1507Jaho Seo, Ravinder Venugopal and Jean-Pierre KennAbstract The technique of feedback linearization is used to design controllers for displacement, v
2、elocity and differential pressure control of a rotational hydraulic drive. The controllers, which take into account the square-root nonlinearity in the systems dynamics, are implemented on an experimental test bench and results of performance evaluation tests are presented. The objective of this res
3、earch is twofold: firstly, to present a unified method for tracking control of displacement, velocity and differential pressure; and secondly, to experimentally address the issue of whether the system can be modeled with sufficient accuracy to effectively cancel out the nonlinearities in a real-worl
4、d system. Keywords: Nonlinear control; Feedback linearization; Hydraulic actuators; Real-time systems 1. IntroductionElectro-hydraulic hydraulic servo-systems (EHSS) are extensively used in several industries for applications ranging from hydraulic stamping and injection molding presses to aerospace
5、 flight-control actuators. EHSS serve as very efficient drive systems because they posses a high power/mass ratio, fast response, high stiffness and high load capability. To maximize the advantages of hydraulic systems and to meet increasingly exacting performance specifications in terms of robust t
6、racking with high accuracy and fast response, high performance servo-controllers are required. However, traditional linear controllers (Anderson, 1988 and Merritt, 1967) have performance limitations due to the presence of nonlinear dynamics in EHSS, specifically, a square-root relationship between t
7、he differential pressure that drives the flow of the hydraulic fluid, and the flow rate. These limitations have been well documented in the literature; see Ghazy (2001), Sun and Chiu (1999), for example. Several approaches have been proposed to address these limitations, including the use of variabl
8、e structure control (Ghazy, 2001; Mihajlov, Nikolic, & Antic, 2002), back-stepping (Jovanovic, 2002; Kaddissi et al., 2005 and Kaddissi et al., 2007; Ursu & Popescu, 2002) and feedback linearization (Chiriboga et al., 1995 and Jovanovic, 2002). Variable structure control in its basic form is prone t
9、o chattering (Guglielmino & Edge, 2004) since the control algorithm is based on switching; however, several modifications have been proposed to address this problem (Ghazy, 2001, Guglielmino and Edge, 2004 and Mihajlov et al., 2002). Back-stepping is a technique that is based on Lyapunov theory and
10、guarantees asymptotic tracking (Jovanovic, 2002, Kaddissi et al., 2005, Kaddissi et al., 2007 and Ursu and Popescu, 2002), but finding an appropriate candidate Lyapunov function can be challenging. The controllers obtained using this method are typically complicated and tuning control parameters for
11、 transient response is non-intuitive. Other Lyapunov based techniques address additional system nonlinearities such as friction, but are also prone to the same drawbacks as those listed for back-stepping (Liu & Alleyne, 1999). Feedback linearization, in which the nonlinear system is transformed into
12、 an equivalent linear system by effectively canceling out the nonlinear terms in the closed-loop, provides a way of addressing the nonlinearities in the system while allowing one to use the power of linear control design techniques to address transient response requirements and actuator limitations.
13、 The use of feedback linearization for control of EHSS has been described in Chiriboga et al. (1995) and Jovanovic (2002). In Brcker and Lemmen (2001) disturbance rejection for tracking control of a hydraulic flexible robot is considered, using a decoupling technique similar to the feedback lineariz
14、ation approach proposed herein. However, this approach requires measurements of the disturbance forces and their time derivatives, which are unlikely to be readily available in a practical application. In contrast to the above mentioned techniques, which are all full-state feedback based approaches,
15、 Sun and Chiu (1999) describe the design of an observer-based algorithm specifically for force control of an EHSS. An adaptive controller which uses an iterative approach to update control parameters and addresses frictional effects with minimal plant and disturbance knowledge is proposed in Tar, Ru
16、das, Szeghegyi, and Kozlowski (2005) based on the model described in Brcker and Lemmen (2001). Most of the literature on the subject shows simulation results; notable exceptions with actual experimental results are Liu and Alleyne (1999), Niksefat and Sepehri (1999), Sugiyama and Uchida (2004), and
17、Sun and Chiu (1999). The focus of this study is on presenting a controller design approach that is comprehensive, that is, one that covers displacement, velocity and differential pressure control, addresses the nonlinearities present in EHSS and considers practical issues such as transient response
18、and real-time implementation. Thus, a significant portion of the paper is dedicated to the experimental aspects of the study. In addition, this paper is intended to serve as a clear guide for the development and implementation of feedback linearization based controllers for EHSS. The paper is organi
19、zed as follows: Section 2 describes the rotational hydraulic drive that is used as an experimental test bench. In this section, the mathematical model of the system is also reviewed and validated using experimental data. Section 3 describes the design of PID controllers for this system with simulati
20、on and experimental results that serve as a baseline for evaluating the performance of the feedback linearization controllers; Section 4 describes the design and implementation of the feedback linearization controllers and finally, concluding remarks are provided in Section 5. 2. ModelingSystem desc
21、riptionThe electro-hydraulic system for this study is a rotational hydraulic drive at the LITP (Laboratoire dintgration des technologies de production) of the University of Qubec cole de technologie suprieure (TS). The set-up is generic and allows for simple extension of the results herewith to othe
22、r electro-hydraulic systems, for example, double-acting cylinders. Referring to the functional diagram in Fig. 1, a DC electric motor drives a pump, which delivers oil at a constant supply pressure from the oil tank to each component of the system. The oil is used for the operation of the hydraulic
23、actuator and is returned through the servo-valve to the oil tank at atmospheric pressure. An accumulator and a relief valve are used to maintain a constant supply pressure from the output of the pump. The electro-hydraulic system includes two Moog Series 73 servo-valves which control the movement of
24、 the rotary actuator and the load torque of the system. These servo-valves are operated by voltage signals generated by an Opal-RT real-time digital control system. Fig.1.Functional diagram of electro-hydraulic system. The actuator and load are both hydraulic motors connected by a common shaft. One
25、servo-valve regulates the flow of hydraulic fluid to the actuator and the other regulates the flow to the load. The actuator operates in a closed-loop while the load operates open-loop, with the load torque being proportional to the command voltage to the load servo-valve. While the actuator and loa
26、d chosen for this study are rotary drives, the exact same set-up could be used with a linear actuator and load, and thus, they are represented as generic components in Fig. 1. The test set-up includes three sensors, two Noshok Series 200 pressure sensors with a 010V output corresponding to a range o
27、f 20.7MPa (3000 PSI) that measure the pressure in the two chambers of the rotational drive, as well as a tachometer to measure the angular velocity of the drive. In order to reduce the number of sensors used (a common preference for commercial application), angular displacement is obtained by numeri
28、cally integrating the angular velocity measurement. Fig. 2 shows the layout of the system and the Opal-RT RT-LAB digital control system. Fig.2.Layout of LITP test bench. The RT-LAB system consists of a real-time target and a host PC. The real-time target runs a dedicated commercial real-time operati
29、ng system (QNX), reads sensor signals using an analog-to-digital (A/D) conversion board and generates output voltage signals for the servo-valves using a digital-to-analog (D/A) conversion board. The host PC is used to generate code for the target using MATLAB/Simulink and Opal-RTs RT-LAB software a
30、nd also to monitor the system. Controller parameters can also be adjusted on-the-fly from the host in RT-LAB.3. ConclusionsThe goal of this research is to review the nonlinear dynamics of a rotational hydraulic drive, study how these dynamics lead to limitations in PID controller performance, and to
31、 design and implement servo-controllers appropriate for displacement, velocity and pressure control. Feedback linearization theory is introduced as a nonlinear control technique to accomplish this goal in this study, and the controllers designed using this method are validated using experimental tes
32、ts. From these tests, it can be seen that for hydraulic systems that have nonlinear characteristics, feedback linearization theory provides a powerful control strategy that clearly improves on PID control in terms of tracking precision and transient response. The results show that the system can be
33、modeled with sufficient accuracy to effectively implement the controllers. This study is limited to the control of a rotational hydraulic drive. The application of feedback linearization theory to the control of more complex integrated rotational and linear drives, as well as other effects such as f
34、riction, may be considered as future extensions of this work. 译文：反馈线性化控制一台转动液压传动控制工程实践， 15卷， 12期， 2007年12月，页1495至1507页Jaho Seo, Ravinder Venugopal 和 Jean-Pierre Kenn摘要线性反馈技术是用于设计控制器的位移、速度和控制液压往复传动的压差。该控制器，应用了平方根非线性系统的动力学，用于实施实验性测试平台和成果的绩效评估测试。本研究的目的是双重的：第一，以目前的一个统一的方法跟踪控制的位移，速度和压差;第二，通过实验解决问题的系统是否可以
35、以足够的精确度模仿，从而有效地取消了非线性在实际体系中的应用。 关键词：非线性控制;反馈线性化;液压作动器;实时系统1 导言 电液伺服液压系统（ ehss ）广泛应用于各个行业，涉及到液压冲压、注塑成型机和航天飞行控制致动器。电液伺服液压系统作为非常有效的动力驱动系统，拥有高功率/质量比，反应快，高刚度，高承载能力等优点。最大限度地利用液压系统，并满足日益严格的性能要求，鲁棒跟踪精度高和快的响应速度是高性能伺服控制器所需要的。但是，传统的线性控制器（ Anderson， 1988年和Merritt， 1967年 ）的局限性在于非线性动力学在电液伺服液压系统中的应用，具体地说，一个平方根关系压差
36、驱动流的液压流体和流速。这些限制已在文献上都有记载了，见Ghazy（ 2001 ） ，Sun and Chiu（ 1999 ） ，例如: 若干做法已被提出，以解决这方面的不足，包括使用变结构控制（Ghazy ， 2001年; Mihajlov, Nikolic, & Antic ， 2002年） ，回步（Jovanovic， 2002年; kaddissi等人， 2005年和 kaddissi等人， 2007年; ursu Popescu, 2002年）和反馈线性（ Chiriboga et al.， 1995年和Jovanovic， 2002年 ） 。变结构控制在其基本形式是容易的抖振（ g
37、uglielmino Edge， 2004年）因为控制算法是基于转换的;但是，提出了一些方案来解决这一问题（ ghazy ， 2001年 ， guglielmino and Edge， 2004 and Mihajlov et al.， 2002年 ） 。回步这种技术，是基于Lyapunov理论，并保证渐近跟踪（ Jovanovic, 2002， ， kaddissi等人， 2005年 ， Kaddissi et al.， 2007年和Ursu and Popescu, 2002） ，但是，寻找一种适当应用函数的技术具有挑战性。使用这种方法的控制器具有典型的复杂性而且校正控制参数瞬态响应也不直
38、观。其他的Lyapunov为基础的技术解决了系统的非线性如摩擦，但也容易产生同样的缺点（Liu & Alleyne, 1999年） 。反馈线性化，实现了非线性系统转化为一个等价的线性系统有效地抵消闭环系统中的非线性计算，并提出了一种解决非线性系统的方法，同时也允许使用动力线性控制设计技术来研究瞬态响应要求和舵机的局限性。使用反馈线性控制电液伺服液压系统已被描述在Chiriboga et al. (1995) and Jovanovic (2002) 、Brcker and Lemmen ( 2001 ）的书里，为跟踪控制的液压柔性机器人而进行的抗扰被认为是利用解耦技术类似的反馈线性化方法提出了
39、此处。但是，这种方法需要测量干扰势力及其衍变的时间，在实际应用中这是不太可能的。与上述提到的都是以全状态反馈为基础的做法相比，Sun and Chiu（ 1999 ）提出了设计一个基于观测器的算法，专门为部队控制的一个电液伺服液压系统。一个采用迭代的方法设计的自适应控制器来更新控制参数并解决由于较小厂房和扰动知识造成的摩擦影响在这里被提出Tar, Rudas, Szeghegyi, and Kozlowski (2005)模型的基础上，在Brcker and Lemmen (2001) 描述了。 大部分的文献就此有着相仿的记录，与实际的试验结果Liu and Alleyne (1999), N
40、iksefat and Sepehri (1999), Sugiyama and Uchida (2004) 表现出的明显的例外 。本研究的重点是介绍一种全面的控制器设计方法，也就是涵盖位移、速度和压差控制的设计，它提出非线性在电液伺服液压系统中的弊端并探讨像瞬态响应和实时实现这样的实际性问题。因此，文中重要的部分是关于实验方面的研究。此外，这篇文章可以作为一个明确的指导，帮助其制定和实施反馈线性化控制器在电液伺服液压系统中的应用。 本文的组织结构如下：第2节提出了旋转液压传动是用来作为实验测试平台。在这一节中，该系统的数学建模，还审查和审定了实验数据。第3节描述设计PID控制器通过模仿和实验
41、结果对反馈线性控制器的基线业绩进行考核;第4节描述了设计和实施反馈线性控制器，结束语提供在第5节。 2 建模系统说明 这项研究的电液伺服系统是一种旋转液压传动技术在LITP（实验室Intgration万德科技生产）的大学学院魁北克比涅技术高等学校（TS ） 。此设立是通用，并允许简单的延伸结果应用于其他电动液压系统，例如双作用气缸。 谈到部分函数功能图，如图 1 ，直流电动机驱动泵，泵提供了石油在恒定的应压力下，从油箱到系统的每个部分。石油是用于运转该液压致动器并通过大气压力经由伺服阀回到油箱。一个蓄能器和一个减压阀是通过泵的输出量来维持一个稳定的供应压力。电液伺服系统包括两穆格系列73伺服阀
42、来控制运动的旋转致动器和系统负载转矩。这些伺服阀操作，由欧泊-逆转录实时数字控制系统产生的电压信号所驱动。图。 1 。功能图的电液控制系统致动器和负载都和液压马达相连，由一个共同的轴、一个伺服阀调节动器流体流量和调节其他流量负载。动运行在一个封闭的回路，而负荷运行在开环中，与负载转矩成正比并控制伺服阀电压负荷，尽管动器和负载在此项研究中是一种旋转驱动器，同样的设立可用于直线驱动器和负载，因此，它们派代表作为通用组件图。 1 。测试包括3个传感器，两个努肖克系列200个压力传感器，以0-10 V输出相应的一定范围内的20.7兆帕斯卡（ 3000 PSI ），可以测量这两个商会旋转驱动的压力，而且
43、是一个测速仪测量角速度的驱动器。为了减少传感器的个数（一种常见商业应用程序） ，用于进行数控整合角速度测量的角位移得到应用。 图 2 显示该套系统的布局和蛋白石逆转录实验室数字化控制系统。图 2 布局litp试验台。 该逆转录实验室系统包括一个实时目标和PC主机。实时目标按照了一个专门的商业实时操作系统（ QNX的） ，采用模拟到数字（模拟/数字）转换板来读取传感器信号来产生输出电压信号，伺服阀采用数字至模拟（ D /I）转换显示板。主机PC ，是用来产生代码，利用Matlab / Simulink和蛋白石逆转录的逆转录实验室软件，并监测系统。控制参数，还可以调整来自RT-LAB的on-the
44、fly。 3 结论这项研究的目标是探讨非线性动力学的轮训液压传动技术，研究这些如何动态产生PID控制器性能的局限性，以及设计和使用适合于位移、速度和压力控制的伺服控制器。反馈线性理论被引入作为一种非线性控制技术，在这项研究中实现这一目标，而且设计使用这种方法的控制器在实验测试中恶道了很好的利用。 从这些测试中可以看出液压系统有非线性特性，反馈线性理论提供了强有力的控制策略，这显然提高了对PID应用在跟踪精度和瞬态响应方面的控制。研究结果表明该系统可以以足够被模仿，从而有效地应用于控制器。 这项研究仅限于控制轮训液压传动。应用反馈线性理论来控制更复杂的综合旋转运动和线性驱动器，以及如摩擦等方面的影响，可被视为未来扩展这方面工作的方向。
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