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1、DSP控制电液伺服驱动DSP Control of Electro-Hydraulic Servo ActuatorsABSTRACTHydraulic actuators are characterized by their ability to impart large forces at high speeds and are used in many industrial motion systems. In applications where good dynamic performance is important it is common to contain the actu
2、ator in a servo loop comprising a feedback transducer and electronic controller. The majority of electronic servo-controllers used in these systems are analogue based implementations of the well-known PID type. However, the requirement to implement advanced control strategies has led to an increased
3、 interest in the use of digital signal processors (DSPs) in this field. One design approach which merits special consideration is the use of computer simulation software to model the hydraulic plant and electronic servo-controller, and to generate and test embedded code for the target DSP. This appl
4、ication report discusses some of the issues involved in controlling linear hydraulic actuators, and the suitability of the TMS320C28x DSP for such systems.1 IntroductionThe range of applications for electro-hydraulic servo systems is diverse, and includes manufacturing systems, materials test machin
5、es, active suspension systems, mining machinery, fatigue testing, flight simulation, paper machines, ships and electromagnetic marine engineering, injection moulding machines, robotics, and steel and aluminium mill equipment. Hydraulic systems are also common in aircraft, where their high power-to-w
6、eight ratio and precise control makes them an ideal choice for actuation of flightsurfaces.Although electrical motors are sometimes used in many of these applications, motion control systems requiring either very high force or wide bandwidth are often addressed more efficiently with electro-hydrauli
7、c rather than electromagnetic means. In general, applications with bandwidths of greater than about 20 Hz or control power greater than about 15 kW, may be regarded as suitable for servo-hydraulic techniques.Apart from the ability to deliver higher forces at fast speeds, servo-hydraulic systems offe
8、r several other benefits over their electrical counterparts. For example, hydraulic systems are mechanically “stiffer”, resulting in higher machine frame resonant frequencies for a given power level, higher loop gain and improved dynamic performance. They also have the important benefit of being sel
9、f-cooled since the driving fluid effectively acts as a cooling medium carrying heat away from the actuator and flow control components. Unfortunately hydraulic systems also exhibit several inherent non-linear effects which can complicate the control problem.The vast majority of electronic closed loo
10、p controllers are based on simple analogue circuit designs offering robust, low cost implementations of the well known PID control strategy. This approach works well in systems with simple topology and limited bandwidth. However the growing use of complex control strategies, coupled with the need to
11、 support enhanced features such as data-logging and digital communications, has led to increased interest in the use of digital processors for control of hydraulic servo-systems. Nowhere is this more apparent than in the field of mechanical test equipment, where the use of a programmable digital pro
12、cessor allows the same servo controller to be used with a wide range of hydraulic systems.This application report reviews some of the issues facing the hydraulic control engineer and discusses the suitability of high-speed DSPs for control of servo-hydraulic systems. The application report begins wi
13、th an evaluation of the DSP for use in electro-hydraulic servo-controllers, and introduces the TMS320C28x family: a DSP platform optimized for digital control applications. Section 3 describes the principal components of the hydraulic system. In Section 4, mathematical models for the various plant e
14、lements are developed and using Simulink. Section 5 presents a case study of a hydraulic control system and deals with fitting real data to the model to validate its behavior. The application report concludes with a brief summary and discussion of the application and design process.2 The C2000 DSP f
15、or Digital Control2.1 The Benefits of DSP for Digital ControlEmbedded digital controllers offer several important benefits to the electronic design engineer, including: immunity from errors arising from component tolerance, thermal drift and aging improved noise immunity ability to modify and store
16、control parameters ability to easily implement digital communications system fault monitoring and diagnostic capabilities data logging capability ability to perform automated calibrationThe performance of a high quality hydraulic actuator is very dependant on the servo-controller. DSPs lend themselv
17、es well to implementing real-time control algorithms, and have been widely used in high-performance digital controllers for many years.In addition to the benefits above, a DSP allows the engineer to: implement advanced control strategies, including multi-variable and complex control algorithms using
18、 modern intelligent methods such as neural networks and fuzzy logic. perform adaptive control, in which the algorithm dynamically adapts itself to match variations in system behavior. implement complex topologies such as multi-axis control where synchronization of multiple force patterns is required
19、. perform diagnostic monitoring, including frequency spectrum analysis to identify mechanical vibrations and predict failure modes. efficiently implement high-order digital filters including sharp cut-off notch filters to remove energy that would otherwise excite resonant modes and possibly lead to
20、instability. reduce system cost by taking advantage of a rich integrated peripheral set to minimize component count and board size.The use of digital controllers is sometimes avoided on the expectation that the user is obliged to invest time in learning new programming languages, and will face diffi
21、culties in testing and de-bugging the code. The Texas Instruments C28x DSP platform includes a high performance C compiler and an extensive set of software libraries to minimize development effort.Recent developments in simulation software also enable designers to model fixed-point digital processor
22、s, and to automatically generate optimized source code which may be compiled and run on the target processor directly from the simulation environment. This “hardware-in-the-loop” approach enables the control algorithms generated by the model to be executed on a real target processor such as the C28x
23、 during simulation, and increases the level of design confidence. The ease with which control algorithms can be created and modified in this manner can save months of development time and leads to earliererror detection compared with traditional hand coding methods.2.2 The TMS320C28x DSP FamilyThe c
24、hoice of processor to implement a given control algorithm is influenced by many factors. The most basic and obvious is that the device must be able to compute the control algorithm swiftly enough to keep up with the real-time demands of the system. In many cases, such as the simple PID controller, t
25、he control task is relatively simple, but to implement more complex control strategies and in cases where additional processor tasks are to be performed, more CPU bandwidth is required and it is desirable to select a processor which is optimized to perform real-time computations. A multi-bus archite
26、cture and rich instruction set makes DSPs well suited to executing demanding real-time control algorithms. The TMS320C28x family from Texas Instruments represents the state-of-the-art in control DSPs and is the ideal architecture for digital control applications.Figure 1. Block Diagram of the TMS320
27、F280x DSP FamilyThe TMS320C28x DSP incorporates a high-performance 32-bit fixed-point DSP core, featuring a low latency interrupt mechanism, highly efficient instruction set including “atomic” instructions, and an execution pipeline for high-speed code execution from internal flash memory. The C28x
28、has on-chip ROM and RAM memory blocks, and a rich set of integrated peripherals including a high speed A/D converter, several serial ports, and multiple PWM generation units.Several optimized libraries are available for the C28x platform, including a set of C language peripheral header files, and an
29、 optimized mathematical library supporting 32-bit fixed point functions. The combination of a high performance DSP core, a rich integrated peripheral set, and an extensive library of optimized control algorithms renders the C28x an excellent choice for digital control applications.1引言摘要液压驱动的特点是,它能够以
30、高转速传递大转矩,在许多工业运动系统中得到应用。 在应用中良好的动态性能,是重要的是共同遏制驱动伺服回路组成反馈传感器和电子控制器。大多数电子伺服控制器使用这些系统是基于模拟实现了著名的PID型。 然而, 规定实施先进控制策略,也带来了更多的利率,使用数字信号处理器 (三十八)在这一领域的合作。 一个设计方法值得考虑,特别是利用计算机仿真软件来模拟液压装置和电子式伺服控制器,以产生和嵌入式测试码为目标DSP 。 这项申请报告讨论的一些问题涉及线性控制液压驱动,和适用性的TMS320C28X处理器DSP的这类系统。电液伺服系统的应用范围是多种多样的,包括制造系统,材料试验机, 主动悬架系统,采矿
31、机械,疲劳测试,模拟飞行,造纸机械,船舶和海洋电磁工程,注塑机, 机械,钢铁和铝轧机设备。 液压系统也很常见,在航空器上 其高功率-重量比和精确控制,使他们成为理想的选择自动飞行的表面。虽然电动机有时被用在许多这些应用, 运动控制系统的要求不是很高武力或带宽往往给更有效率电液伺服而非电磁手段。 一般来说,申请带宽大于约20赫兹或控制功率大于15千瓦; 可视为适合液压伺服控制技术。除了能够提供更高的力量在速度快, 液压伺服控制系统,提供其他几个好处超过其电气同行。 例如,液压系统都是机械式的严厉 ,导致较高的机架共振频率为某一功率水平, 高闭环增益和改进动态性能。 它们也有重要的好处是自冷自驾车
32、有效液作为冷却介质进行 热离器和流量控制元件。 不幸的液压系统还具有若干固有的非线性效应,可以复杂的控制问题。绝大多数的电子闭环控制是基于简单的模拟电路设计,提供强劲 低成本实现众所周知的PID控制策略。 这种做法行之有效,在系统简单拓扑和有限的带宽。 然而越来越多地使用复杂的控制策略, 再加上需支持增强功能,如数据记录系统和数字通信 导致利息增加,在使用数字处理器控制的液压伺服系统。 这一点是最明显的领域中的力学性能测试设备 凡使用一种可编程数字处理器允许同一伺服控制器,可用于多种 液压系统。这项申请报告审查面临的一些问题液压控制工程师和探讨适合高速多DSP 控制液压伺服控制系统。 申请报告
33、开始评估的DSP用于电液伺服控制器 并介绍了TMS320C28X处理器家族:一个DSP平台优化的数字控制应用。 第3节的主要组成部分的液压系统。 在第4 ,数学模型,对各种植物成分的开发和利用仿真。 第5列的案例研究了液压控制系统,并处理拟合真实数据模型 为了验证其行为。 申请报告最后简要介绍和讨论中的应用及设计过程。2 c2000 DSP的数字控制 2。1效益的DSP数字控制 嵌入式数字控制器可提供若干重要利益的电子设计工程师,其中包括: 待添加的隐藏文字内容1免于错误引起组成宽容,笔 0001-5733漂移和老化改进的抗干扰能力修改和贮存控制参数能力,我很容易 物排斥数码通讯系统故障监测和
34、诊断能力数据记录能力能力进行自动校准表现了高品质的液压驱动是非常依赖的伺服控制器。 DSPs的本身并实施实时控制算法, 并已广泛应用于高性能数字控制器多年。 除了在上述的好处,让DSP的工程师内容: 实施先进控制策略 包括多变量和复杂的控制算法,用现代智能方法,如神经网络和模糊逻辑。 演出自适应控制,其中动态算法,以适应比赛的变异系统行为。 执行复杂的拓扑结构,如多轴控制下同步多重力量的格局。 进行诊断监测,包括频谱分析,以找出机械振动和预测失效模式。 有效落实高阶数字滤波器包括大幅度停产陷波滤波器来消除能源,否则激起谐振模式 并有可能导致不稳定的因素。 降低系统成本,利用丰富的整合周边设定为
35、减少元件数和董事会规模。使用数码控制器有时是避免期望的,即用户必须投入时间 学习新的编程语言,并会遇到困难,在测试与德窃听的代码。 得克萨斯仪器c28xDSP平台包括高性能C编译器和一套广泛的软件库 最大限度的发展努力。最近的事态发展,在仿真软件还使设计者能够示范定点数字处理器, 并自动生成的优化代码,可以编译和运行在目标处理器直接由S 仿真环境。 这个硬件在回路的方法,使控制算法生成的模型,可以签一个实际的目标处理器等 作为c28x仿真过程,并提高设计水平的信心。 再加上控制算法,可以创建和修改,这种方式可以节省几个月的开发时间 并导致先前的错误检测与传统手编码方法。2。2 TMS320C2
36、8X处理器DSP系列选择处理器,以执行特定的控制算法是受多种因素影响。 最基本,最明显的就是设备必须能够计算出的控制算法快速足以 跟上实时需求的系统。 在许多情况下,例如简单的PID控制,控制任务,是比较简单, 但执行更复杂的控制策略和的情况下,额外的处理器的任务是表演, 多CPU的带宽要求,是最为理想的选择处理器是适合进行实时36。9% 。 一个多总线结构和丰富的指令集使得DSPs的佳人要求执行实时控制算法。 TMS320C28X处理器的家庭从德州仪器代表国家-国际艺术在控制疾病,是理想的建筑为数字控制申请。图1 。 方框图的tms320f280x DSP系列在TMS320C28X处理器DSP内嵌一个高性能32位定点DSP核心,展出低延迟中断机制, 高效的指令集包括原子的指示,并执行管线高速代码,从内部闪存。 c28x的对芯片的ROM和RAM内存块, 以及一整套丰富的集成外设包括一条高速模/数转换器,几个串口 和多重PWM的发电机组。几个优化图书馆可供c28x平台,包括一套C语言周边头文件, 以及优化数学图书馆支持32位定点功能。 结合高性能DSP核心,集成丰富的周边集 以及丰富的图书馆优化控制算法使得c28x极佳的数字控制应用。
