D-H parameter method is employed to conduct forward kinematic analysis of the dexterous hand in this article, in order to obtain the mechanical performance of the SMA biomimetic flexible dexterous hand for object grasping. The D-H parameters of the dexterous hand are determined, and the position expression of the fingertip relative to the base coordinate is obtained through theoretical calculations. Furthermore, inverse kinematic theoretical analysis of the biomimetic dexterous hand is conducted to obtain the joint angle parameters of each finger. A forward kinematic simulation model of the biomimetic dexterous hand is established, and the relationship between finger joint angles and fingertip position curves is obtained through simulation. The simulation results are compared with the theoretical analysis results to validate the correctness of the kinematic analysis of the dexterous hand, providing insights for its optimized design.
In order to meet high quality measurement requirements with less cost and lesser time consumption, the sampling strategy has to be planned before the measuring device is already available. In this paper, a common 3D geometric measuring system based on laser scanning technique is presented. An measurement cost model is established by consider of several cost sources in 3D geometric measurement process. In terms of view angle of laser scanner, an optimal inspection strategy planning is developed on a circular feature too. Finally, a series of experiments on typical circular of workpieces are performed based on coordinate measuring system equipped with a laser line scanner. In case of desired measurement accuracy for the measured feature, the minimum inspection cost can be obtained by the iterative optimization algorithm, thus generating a reliable and an efficient sampling path planning. Those results are most promising for on-machine applications in optimal inspection strategy of 3D geometric of workpiece.
Nowadays, in industrial area, many mechanical part manufactures are applying 3D optical scanner in their production shop to do part online inspection, or in their coordinate measurement laboratory to obtain crucial part dimensions. The high demands of the 3D optical scanner make it necessary for researchers to create convenient and stable device for calibrating this kind of contact-less measurement instrument. In a former study, we introduced a plate with standard spheres as a calibration device, which showed a good test result when applied on a 3D optical scanner. However, we decide to do more research on related area. The first purpose of this paper is to present an improved calibration device based on our former study and daily work experience. The new device has a wider test range with less spheres, and it’s structure is more portable, stable and more convenient to provide spatial positions. Results showed that the new device performed well in data stability and is quite easy to practice. The second purpose of this work is to study related influence factors on the 3D optical scanner calibration process. We investigated factors such as temperature, points cloud density, reflection patch density and numbers of images stitching. The results showed that those factors should be limited in proper conditions to ensure an acceptable calibration of 3D optical scanner.
Nowadays, with 3D topographic features increasingly complicated and complex, scanning probe microscopes have widely been used of nano-scale dimensional measurement in the semiconductor manufacturing and space industry, which can create three-dimensional data over almost all solids in a wide range of ambient. Although scanning probe microscopes readily achieve nanometer level resolution images of measured surfaces, there are several aspects of their behavior that can cause them to yield large measurement errors. In this paper, according to possible traceability pathways for calibration of lateral axes and z axis, both pitch and step height measurements are respectively performed and axis error self-correction model is proposed. The influence of thermal stability on drift error is also discussed. Experimental results show that our method will be helpful for a fast performance evaluation test for scanning probe microscope.
A calibration device for the optical scanner is presented in this paper for the situation that lacking of a convenient calibration method for the optical scanner in domestic industry practice. The device utilized the spherical center distance of fixed balls as standard dimensions. It can provide various dimensions in different orientations and magnitudes since it has nine fixed standard balls in different positions. When we run an actual measurement process on this device with an optical scanner, the indication error of the scanner can be obtained conveniently. The device is simple in structure and easy to operate, it can produce multiple dates in one single measurement process simultaneously, which can evaluate the performance of the optical scanner comprehensively.
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