机械外文翻译调直机的反馈方法

1、a closed loop feedback method for a manual barstraightenerrobert j. miklosovic, zhiqiang gaodepartment of electrical and computer engineeringcleveland state universitycleveland, ohio, usaabstractautomation of a unique manually controlled industrial bar straightener is proposed. a continuous-time clo

2、sed loop model is constructed in simulink for an event-driven process through the use of asynchronous timers. the system is simulated with linear and nonlinear pd controllers. a nonlinear filter,called the tracking differentiator, is introduced as an alternative to a linear approximate means of prov

3、iding accurate derivative feedback in the presence of noise. in both cases, the nonlinear techniques outperformed their linear counterparts while retaining tuning simplicity.i. backgroundprecision straightening of a cylindrical metal bar is largely based on the ability to precisely measure its geome

4、try. a few fundamental measurements and how each influences the tolerance specification on straightness should first be understood. methods for measuring roundness and straightness are covered to lay the groundwork for the problem formulation. the basic operation of the machine is outlined in sectio

5、n ii, and its fundamental limitations and need for automation are discussed. section iii addresses the task of closing the loop through block diagrams and the role of new hardware in the process. section iv contains descriptions of all of the blocks that are modeled in simulink. the linear and nonli

6、near controller designs are discussed in section v, the system is simulated in section vi, and concluding remarks are made in section vii.a. measuring roundnessroundness is a quantity derived from comparing the shape of a cross-sectional area at one distinct point along a cylinders length against a

7、circle. a round metal bar that is arbitrarily long with respect to its diameter has to be checked for roundness in many locations lengthwise and averaged to insure overall consistency. roundness is approximated by rotating the work piece one revolution in a vee block while measuring the surface with

8、 an indicator. taking the difference between the minimum and maximum indicator readings in this case is referred to as the total indicator reading (tir) 1.b. measuring straightnessstraightness is a quantity derived from comparing the axial centerline of a specific section of a cylinders length again

9、st a straight line. a simple method for approximating straightness is by rotating the bar one revolution between two vee blocks that are a fixed distance (d) apart, while measuring in the center with an indicator. the distance that the axial centerline of the part deviates from a theoretically strai

10、ght centerline directly below the indicator equals the extent to which the part is bowed, or warped, over length d. the maximum and minimum indicator readings (ix and in) are physically represented in fig.1. from this, tir is derived as:tir= ix in = (r + |bow|)-(r |bow|) =2*|bow| (1)deviations in ro

11、undness, outside diameter (od) size, and finish can adversely affect the measurement.figure 1. max. and min. indicator readings of a bowed partc. straighteningthe straightening process, which can be broken into steps, simply involves correcting any error while checking for straightness. first, the p

12、art is measured for straightness. then, it is rotated so that the bow is oriented 180 degrees away from the vee blocks with the maximum indicator reading facing upwards. finally, a counter-bending force replaces the indicator and straightens the work piece against the vee blocks.ii. machine operatio

13、nthe straightener to be automated uses a non-contact ultrasonic sensor in place of the indicator and rollers in place of the vee blocks in an effort to minimize contact wear. the part slowly spirals through the machine. the indicator reading becomes a continuous sinusoid at the sensors output, havin

14、g a peak-to-peak value equal to the tir each revolution. tir is sampled from the sensor output and calculated each revolution, making the sample period of one revolution the minimum time between consecutive bends (ysp). tir is the plant output (y) to be controlled. when the part is straightened, the

15、 machine stops rotation with the bow facing upwards, but the part continues to feed lengthwise while an air cylinder counterbends the part over a period of time. this bend time (bt) is the control variable (u). fig. 2 illustrates this operation.figure 2. the straightener to be automateda. process li

16、mitationsthere are aspects of the process that can limit the controllers performance and slow it down by extending ysp. each is observed and taken into consideration when producingan accurate simulation model:1. the ultrasonic sensor introduces rfi noise into its. the use of a feedback filter is ess

17、ential.2. a rough part surface finish adds distortion to the sensor output.3. an out-of-round part superimposes harmonics on the sensor output sinusoid, placing a bound on the minimum steady state error that is achievable.4. inconsistent material density produces false measurements. the measured foc

18、al length of atransducer is dependent on the density of the material that is being measured 2. the unit cannot measure accurately in the presence of a time-variant material density (i.e. hard spots). although unavoidable, it can be detected, since tir changes monotonically.5. an inconsistent od caus

19、es vertical shifts in the sensor output. a differential tir measurement cancels these affects.6. a twisted part condition is detected when the angular position of the maximum indicator reading slowly moves with each revolution. this condition is created when the part is not straightened at the preci

20、se angular location and occurs because of the quantization affect of the digital readout used by the operator. the new controller will use a continuous signal and the part can be straightened 30 to 45 degrees ahead of the twist when encountered.b. the need for automationreplacement of the operator w

21、ith electronic hardware is beneficial in several ways. the cost of the electronics is much less than the ongoing hourly wage and schedule of an operator. the limitations associated with the digital readout are eliminated, which helps the machine to straighten faster with more precision. the process

22、can be drastically sped up to produce more. though the minimum sample time is one revolution, it does not need to be slow enough for human comprehension. a programmable logic controller (plc) can make several calculations and test the result against a set of rules many times faster than a human bein

23、g.c. research methodologythe focus is split between modeling and control design, since this is a new control problem. the process is manually controlled rather than being strictly manual in operation, meaning the machine needs only a new controller. there is no need for a complete mechanical overhau

24、l, so the best method of straightening is not researched. typical of a small company, time and money are limited. gao and huang 3 presented a new error-based control design framework including such innovations as a nonlinear tracking differentiator and a nonlinear proportional-integral-derivative (n

25、pid) control method. these methods prove to be powerful and simple to tune, which make them ideal for use in an industrial environment.iii. a closed loop solutionthe task of automation can begin once the process is well defined. a straightforward system block diagram is developed, and each block is

26、modeled in simulink. aspects of the hardware configuration are carefully considered.a. from open loop to closed loopthe open loop multi-input-multi-output (mimo) block diagram, in fig. 3, represents the manually controlled process. the operator calculates tir and monitors the angular position (h

27、8576; p) of the bow with each revolution. when y approaches a specified limit, the operator sets bt proportional to y and itsrate, and then pushes a button (bp) to straighten the part. the bend timer creates a pulse triggered by bp that counter-bends the part for bt minutes. this event forces the pa

28、rt to have a specific rate for a period of time. after the event, the part takes on a new rate and the process perpetuates. therefore, y is apiece-wise continuous function of time. the operators involvement in the process is represented as a block in fig. 4.figure 3. open loop block diagramfigure 4.

29、 operator blockrearranging the blocks and breaking each function down into smaller more-manageable blocks reduces the representation to a usable closed loop, single-input-singleoutput (siso) form. fig. 5 shows how a siso plant is obtained by combining the process with the task of sampling the tir, s

30、ince it can be consistently computed.figure 5. siso plant blockthe plant has a variable-width pulse as the input (u) and the sampled tir (y) as the output to be controlled. the incoming changing position of the work piece is modeled as an unknown rate disturbance (d). the closed loop siso block diag

31、ram is shown in fig. 6.figure 6. closed loop block diagramb. hardware configurationdepicted in fig. 7, an encoder and a plc are the only hardware needed for automation. the encoder feeds the angular position of the part back to the controller, and the plc handles all of closed loop functions outside

32、 of the process.figure 7. hardware configurationfig. 8 depicts the hardware layout for plant data acquisition during manual operation. the plc is also used to calibrate a strip chart recorder, shown in fig. 9, which simplifies calibration for the operator and removes room for error during data acqui

33、sition. using the plc for both data acquisition andcontrol keeps costs lower.figure 8. open loop data acquisition configurationfigure 9. chart recorder settings for a .006” tir signaliv. modelingsimulation modeling involves the construction of simulink blocks for each of the blocks in the siso diagr

34、am. three modular blocks are first designed to accommodate the presenceof an event-driven plant in a continuous-time environment where the control variable is an asynchronous pulse width. they are all based on creating asynchronous timers in simulinkby integrating a constant until it reaches a prese

35、t value, then shutting it off by feeding the input with a zero. equation (2) will reach a value of one in the time interval equal to the average of u(t) over it. the accuracy increases if the interval is very small or u(t) is a constant function. a suitable differenceequation is given in (3).a. trig

36、gered sample-and-hold (tsh) blockthe output and rate of the plant immediately after the part has been straightened are dependent on bt, and the previous y and y, all of which occur over different time intervals. the function of the tsh block is to sample a value at one point in time so that it can b

37、e used at another time. shown in fig. 10, the block basically samples the input for a small period of time on the rising edge of an enabling pulse, and then holds that value constant at the output until the block is re-enabled. in simulink, a constant value can be maintained for an arbitrary period

38、of time by building the output of an integrator to a desired value. a t-second timer is created by integrating 1/t until it equals one. it is used to control the small time interval in (4) which takes a time average of the input.figure 10. tsh simulink blockb. pulse blockthe bend timer must be able

39、to convert bt from a value into the timed pulse, u. the pulse block, illustrated in fig. 11, was designed for this purpose. by incorporating (2), it creates a pulse that has a magnitude equal to the sign of the input and a pulse width equal to the inputs absolute value.figure 11. pulse simulink bloc

40、kthe heart of the pulse block is the pulse subsystem block, shown in fig. 12. the reciprocal block generates a divide-byzero error whenever its input is zero. consequently, the reciprocal block needs to be isolated in a subsystem that is only enabled when supplied with a value that is larger than a

41、userdefined constant.v. control designthere are currently many different control structures available, the simplest of which is the pid controller design. for this reason, a pd controller is first applied to the closed loop model to verify its response and stability. it is used as a benchmark for ot

42、her controllers. next, a nonlinear pd (npd) control scheme is introduced. it retains the tuning ease of the pd controller while improving performance. last, a nonlinear filter, called the tracking differentiator (td), is introduced asan alternate means of providing an accurate derivative feedback to

43、 the controller in the presence of noise, thus improving performance.a. linear pid controlfor many reasons, pid control is still used in 90% of industrial applications 3. there are only three tuning parameters, each having direct physical significance to the error signal, not the model. this makes f

44、or easy tuning, without having to spend considerable resources on the construction of a linear model. linear models are often inaccurate and require re-tuning when the real-world plantsthey represent are nonlinear and time varying. a control structure that is error-based, and not model-based, is mor

45、e resilient to model uncertainties 3. the pid control law in (6) represents the direct physical meanings of the three parameters, where e is the error signal, kp is the proportional gain, ki is the integral gain, and kd is the derivative gain. k e k edt k= p + i _ + d (6)vi. simulationthe pd control

46、ler and the npd controller are simulated in simulink on the closed loop model. the significance of practical initial conditions and disturbances are considered. simulation results from the two cases are presented and discussed. next, the steady state error is compared under various noise and disturb

47、ance conditions. finally, a second order approximation and a td are implemented in the feedback loop and simulated with heavy feedback noise for both controllers.a. transient performancesimulating the system and individually adjusting plant parameters to emulate various real world conditions verifie

48、d the design. fig. 19 graphs the output and rate response for the pd controller. notice the control action occurs when the rate is at ±r2 (i.e. ±.001 in this case). the performance measures are defined as follows:1. the settling time (ts) is the time it takes for y to be within ±.001,

49、 since this is the general object ofstraightening.2. overshoot (os) is the maximum |y| after it has reached zero.3. steady state error (ess) is the maximum |y| in the steady state region.the linear and nonlinear pd controllers were tuned to achieve the same ts. the results of the transient responses

50、 of the two controllers for two widely different initial positions are tabulated in table i, to compare os and ess. all units are in thousandths except for settling time.4. the process can be modeled in discrete time and/or with different software. writing the entire plant and bend timer in c may si

51、mplify the simulation model. from this, a class of problems can be clearly studied.5. the process can be investigated and modeled as a finite state machine.调直机的反馈方法罗伯特·j·miklosovic，高志强电气工程和计算机系克利夫兰州立大学美国俄亥俄州克利夫兰手动控制独特自动化的建议。一个连续时间的闭环模型在simulink中构建事件驱动的过程中，通过使用异步定时器。该系统是模拟线性和非线性pd控制器。非线性滤波器

52、，称为跟踪微分，介绍了作为一个替代的存在噪音，提供准确的微分反馈线性近似手段。在这两种情况下，非线性技术优于线性，同时保留调整简单。一，背景主要是基于能够精确地测量其几何精度的圆柱形金属条调直。应先了解一些基本的测量和如何每个影响的直线度公差规范。圆度和直线度测量方法覆盖问题制定奠定了基础。本机的基本操作是在第二节，概述，并讨论了其基本的限制和对自动化的需要。第三节讨论通过框图的循环过程中的作用和新的硬件关闭任务。第四节包含所有的块，在simulink建模描述。在第五节讨论的线性和非线性控制器的设计，该系统是模拟在第六节，第七节总结。答：测量圆度圆度是从一个不同点，以及对一个圆圈一个圆柱体的长

53、度比较的横截面积形状的数量。一个圆形的金属条，其直径是任意长有纵向许多地方要检查圆，平均以确保整体一致性。圆度近似v型块在旋转工件革命的一个指标，同时测量表面。在这种情况下的最低和最高指示读数之间的差异被称为总读数（tir）1。b.测量直线度直线是比较一个圆柱体的长度对直线的一个特定部分的轴向中心线派生的数量。一个简单的方法是近似直线旋转酒吧之间，是一个固定的距离（四）除v型块革命，而在测量指标的中心。的一部分的轴向中心线偏离的指标低于直接从理论上直中心线的距离等于其中部分是鞠躬，或扭曲的程度，超过长度d。身体的最高和最低的指标读数（九中）代表图。外径（od值）的大小，圆度偏差，并完成产生不利

54、影响测量结果。一个弓形部分的指标读数在整顿过程中，它可以分解成步骤，只涉及纠正任何错误，同时检查直线。首先，部分的直线度测量。然后，它是旋转，以便弓是面向180度的v型块朝上最大的指标读数。最后，反弯曲力的替代指标，并拉直对v型块的工件。二、机器操作矫直机是自动化，在地方指标和地方努力的v型块辊使用一种非接触式超声波传感器，以尽量减少接触磨损。部分慢慢地通过机器螺旋。该指标读数在传感器的输出连续正弦波，有等于每个革命的tir的峰 - 峰值。公路运输从传感器输出进行采样，并计算出每个革命，做一个革命的样本期间连续弯（ysp）之间的最短时间。公路运输是厂输出（y）进行控制。部分拉直，当机器停止与弓

55、朝上旋转，但部分继续养活纵向气缸counterbends过了一段时间的一部分。这弯曲的时间（bt）是控制变量（美）。图2说明了这种操作。a.工艺限制有方面的过程中，可以限制控制器的性能和扩大永信药品减缓下来。每个观察和考虑生产精确的仿真模型：1、超声波传感器引入到其rfi噪声。反馈滤波器的使用是必不可少的。2、一个粗糙的零件表面光洁度增加了传感器输出的失真。3、一个地地道道的圆形部分叠加在传感器输出正弦波的谐波，放置一个最低的稳态误差是可以实现的约束。4、材料的密度不一致产生虚假的测量。一个测得的焦距传感器是依赖于正在测量2材料的密度。本机无法准确测量中存在的时间变材料的密度（即硬点）。虽然不

56、可避免的，它可以检测到，因为运输单调变化。5、不一致的外径导致传感器输出的垂直变化。一个差的tir测量抵消这些影响。6、一个扭曲的部分条件被检测到时最大的指标读数的角位置慢慢移动每个革命。这种情况下被创建时的精确角位置拉直的部分不发生由运营商所使用的数字读数，因为量化的影响。新的控制器将使用一个连续信号，并提前30至45度的扭转时遇到的一部分可以被拉直。b.自动化的必要性更换运营商与电子硬件在几个方面是有利的。电子产品的成本是远远高于目前的每小时工资和操作员的时间表。数字读数相关的限制被取消，这有助于机器更快更精确整顿。这个过程可以被大大加快生产更多。虽然最小的采样时间是一个革命，它不需要是缓

57、慢的，对人类的理解不够。可编程逻辑控制器（plc），可以使一些计算和一套规则，对测试结果比人类快很多倍。c.研究方法论分裂之间的建模和控制设计的重点，因为这是一个新的控制问题。手动控制的过程，而不是严格的操作手册，这意味着机，只需要一个新的控制器。有没有必要为一个完整的机械检修，所以最好的方法是不整顿研究。典型的一家小公司，有限的时间和金钱。高和黄3提出了一个新的基于错误控制设计框架，包括非线性跟踪微分器和非线性比例 - 积分 - 微分（非线性pid）控制方法等创新。这些方法被证明是强大的和简单的曲调，使它们在工业环境中使用的理想选择。第三。闭环解决方案一旦这个过程被很好地定义，自动化的任务就可以开始。开发一个简单的系统框图，每块在simulink建模。硬件配置方面慎重考虑。答：从开环到闭环开环多输入多输出（mimo）的框图，如图。 3，代表手动控制的过程。操作计算的tir和监控每个革命弓的角位置。当y接近指定的限制，操作员设置bt的比例为y然后按下一个按钮（bp）的整顿部分。弯曲定时器创建的bp触发脉冲，这一事件迫使一部分有一段时间的具体税率。活动结束后，部分需要一个新的速度和进程延续。因此，y“是一个分段连续函数的时间。在这个过程中运营商的参与，是块图作为代表。 图3、开