Papers by Keyword: Linear Encoder

Abstract: Thermal errors cause serious dimensional errors to a workpiece in precision machining. A feed drive system generates more heat through friction at contact areas, such as the Linear encoder and the guide, thereby causing thermal expansion which affects machining accuracy. Therefore, the thermal deformation of a Linear encoder is one of the most important objects to consider for high-accuracy machine tools. This paper analyzes the increase of the temperature and the thermal deformation of a Linear encoder feed drive system. During temperature variation is measured by using thermocouples , meanwhile, the thermal error of the guide is measured by a laser interferometer. A thermal error model is proposed in this study by using back propagation neural network (BPN). An experiment is carried out to verify the thermal error of the guide under different feed rates and environmental temperature.

Abstract: It is very important to control mechanical press slide height precisely when it works because it will lead to loss of stamping accuracy while the slide height error appears. The paper designed a novel controlling device based on linear encoder to adjust slide height dynamically. Equipped with high-precision linear encoder on the mechanical press slide, the height of slide measured by micro-controller real-timely, the device drives the controlling motor to adjust the position of slider if slide height error occurs.

Abstract: Linear encoder as an important displacement measurement device has been widely used in manufacturing industry. The accuracy of linear encoder is based on the precision of its scales. In this article, the manufacturing process of the scales based on photolithography process and etching process was discussed in order to explain the opening ratio variation. A mathematical model was derived to analyze the effects of opening ratio variation on the waveform of output signal. The result shows that the waveform of the signal is cut off in comparison with the ideal waveform, and the magnitude of the output signal is changed.

Abstract: The influence of quadrature phase shift caused by angular misalignment on the measurement accuracy of two moiré linear encoders is analyzed. A mathematical model of quadrature phase-shift error is derived. The model is employed to analyze the quadrature phase-shift error in lateral-moiré-fringe-based and Vernier-moiré-fringe-based linear encoders respectively, and comparisons are carried out. The results show the nonlinearity of the quadrature phase-shift error and the relative insensitivity of the Vernier-moiré-fringe-based linear encoders to the angular misalignment.

Abstract: In the paper there is shown the way of increasing the accuracy of the Digital System of Position Measurement with the method of extrapolation.

Abstract: In this paper, a novel piezoelectric actuator structure - 4-9-9-14 piezoelectric actuator is constructed, and it is made of piezoelectric buzzer to drive a piezoelectric actuated stage. The 4-9-9-14 piezoelectric actuator offers a better balanced capability of forward rotation and reverse rotation than the conventional edge-driving piezoelectric actuator. According to the rotational speed experiment, the CW/CCW ratio of the 4-9-9-14 piezoelectric actuator is probably 1:0.8. The movement of the pie-zoelectric actuated stage is read and analyzed by means of data acquisition card and LabVIEW software operating in conjunction with a linear encoder. In a natural environment, plenty of noise interferes with linear encoder signals and results in erroneous addition performed by a counter. Therefore, the LabVIEW program set forth the means of filtering and the method for retrieving a correct position signal.

Abstract: A form error characterization of a reflective-type scale grating, which is used in three-degree-of-freedom (3-DOF) encoders for position measurement of a planar motion stage, is presented. The scale grating has a micro-structured surface, the pitch of which is 1 µm in both X- and Y- direction. The periodic pattern on the scale grating generates diffracted beams when a laser beam incidents to the grating surface. The ±1st order diffracted beams from the grating contain information about the stage motions of not only X- or Y- directional in-plane displacement but also Z-directional out-of-plane displacement, and are therefore able to be utilized for multi-axis position detection. Accuracies of the position detection are mainly determined by a period deviation and a Z-directional out-of-flatness of the scale grating. The form error characterization of the grating is possible by using Fizeau interferometer, although the form error of a reference mirror in the Fizeau interferometer still remains as a measurement error in the form of the measured scale grating. In this paper, a new method was proposed to evaluate the form error characterization of the scale grating for the 3-DOF encoder, while eliminating the form error of the reference mirror in the Fizeau interferometer.

Abstract: A new low-cost displacement sensing approach is put forward. It employs physical multiplication by using multiple linear encoders and differential grating codestrips, and the differential phase configuration is mechanically guaranteed; furthermore, a flash signal processing circuit comprising time sequence generator, counter and D/A with no microprocessors involved is also developed. Theoretical analysis is presented, and a test system using Heds-9730 as the detecting unit is built, and then experiments on an electromagnetic actuator are carried out. The measured results agreed well with the original, and the results prove that the sensing approach can achieve high sampling rate, high resolution and cost saving, thus providing an effective displacement measuring means for cost-sensitive applications.

Abstract: In the paper there is shown the way of increasing the accuracy of the Digital System of Position Measurement with the method of extrapolation. There is also shown the modified algorithm of the program of Digital Position Reading Device.

Abstract: This paper presents an electronic subdviving method for linear encoder of high speed position detection. The method aims to enhance the resolution of position measurement and improve the precision of noncircular component cutting system. A 20-subdividing circuit based on resistor chain phase shift is researched and implemented, and some key technologies are discussed. The method is proved to be successful in raising the resolution and precision with a high speed response. The experiment result proves that electronic subdividing method is doable and effective to raise the resolution of the existing system.