机械外文翻译--调直机的反馈方法
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1、 A Closed Loop Feedback Method for a Manual Bar Straightener Robert J. Miklosovic, Zhiqiang Gao Department of Electrical and Computer Engineering Cleveland State University Cleveland, Ohio, USA Abstract Automation of a unique manually controlled industrial bar straightener is proposed. A continuous-
2、time closed 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
3、 of providing accurate derivative feedback in the presence of noise. In both cases, the nonlinear techniques outperformed their linear counterparts while retaining tuning simplicity. I. BACKGROUND Precision straightening of a cylindrical metal bar is largely based on the ability to precisely measure
4、 its geometry. 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
5、 in Section 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
6、 and nonlinear controller designs are discussed in Section V, the system is simulated in Section VI, and concluding remarks are made in Section VII. A. Measuring Roundness Roundness is a quantity derived from comparing the shape of a cross-sectional area at one distinct point along a cylinders lengt
7、h against a 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
8、surface with 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 Straightness Straightness is a quantity derived from comparing the axial centerline of a specific section of a cylinder
9、s length against 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 theor
10、etically straight 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)
11、 Deviations in roundness, outside diameter (OD) size, and finish can adversely affect the measurement. Figure 1. Max. and min. indicator readings of a bowed part C. Straightening The straightening process, which can be broken into steps, simply involves correcting any error while checking for straig
12、htness. First, the part 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.
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