A new method for separating straightness, yawing and rolling errors of a linear slide

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A new method for separating straightness, yawing and rolling errors of a linear slide


Author: Zhu, Ming
Title: A new method for separating straightness, yawing and rolling errors of a linear slide
Degree: M.Sc.
Year: 2010
Subject: Hong Kong Polytechnic University -- Dissertations
Translational motion -- Measurement
Translational motion -- Mathematical models.
Multisensor data fusion -- Mathematical models.
Department: Dept. of Mechanical Engineering
Pages: xiv, 142 leaves : col. ill. ; 30 cm.
InnoPac Record: http://library.polyu.edu.hk/record=b2356848
URI: http://theses.lib.polyu.edu.hk/handle/200/5679
Abstract: A new method based on Fourier series for the separation of straightness motion error, yawing motion error and rolling motion error of a moving machine slide is proposed in this study. The motion of a cutting tool on a lathe may be affected by one or more kinds of dynamic motion error, which is one of the key factors in products' quality deterioration. The method is able to separate straightness, yawing and rolling motion errors by using eight displacement sensors positioned on a vertical stage in two lines parallel to the target profile. Five sensors are installed in the lower row and the other three are in the upper row. All the sensors sample the distance data between the stage and the profile in one designated period of time when the profile is moving in one direction. The displacement signals are fused to eliminate the effect of motion errors. The profiles faced by two rows of sensors are represented by Fourier series and obtained by solving the sensor equations using the sampled data. In this way, different error components can be separately obtained from the sensor outputs. The working principle and measurement procedure are described in the study. The applicability of the method is evaluated by computer simulation. The accuracy of the method is evaluated by comparing the calculated signals with the input signals. The results show that the maximum error in the estimation of profile f₁is 2.91x10-6 mm and the maximum discrepancy of rolling error between input values and obtained values is 9.34x10-5 deg in ideal measuring condition. Simulation confirms that the new method can separate the straightness motion error, yawing error, rolling error as well as the machine profiles f₁and f₂with good accuracy. The effects of sensor gain error, sensor placement error and sensor reading noise on the measurement accuracy are also investigated. The results show that the discrepancies between input and calculated values for all linear errors are less than 0.5 μm and the maximum variations of all angular errors are smaller than 0.0015 deg. It proves that accuracy of the method meets the system requirement. Experiments are carried out to validate the method and good repeatability is found.

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