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- 저자 : Alan Myers (검색결과 2 건)
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Xiaomei Chen,Andrew Longstaff,Simon Parkinson,Alan Myers 한국정밀공학회 2014 International Journal of Precision Engineering and Vol. No.
This paper presents an evaluation method for the rapid and automatic detection of position errors of arrays of small holes on complex-curved and freeform surfaces that can satisfy the special demands of the aviation and automobile industries. The evaluation is based on the dual-sensor autofocusing method. The dual-sensor unit is the combination of a tactile probe and an optical vision sensor. The tactile probe detects the focal position for the optical vision sensor by probing the distance between the objective lens of the microscope and the location of each small hole. The optical vision sensor focuses to this position for capturing the image of the artifact under inspection. As a case study, a pattern of φ 0.5 mm small holes centripetally drilled with equal-angular distribution on the circumference of an elliptical cylinder shell is investigated. The autofocusing errors caused by the radius of the tactile probe and the position errors of the small holes are evaluated mathematically. Subsequently, a standalone dual-sensor autofocusing unit is built and integrated into a user-controllable 3D coordinate test rig. It is used to autofocus and capture the images of small holes. The centroid positions and deviations of the holes are automatically and rapidly detected from the captured images.
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Analysis of Discrete Time Schemes for Milling Forces Control under Fractional Order Holds
Luis Rubio,Manuel de la Sen,Andrew Peter Longstaff,Alan Myers 한국정밀공학회 2013 International Journal of Precision Engineering and Vol. No.
In this paper, discrete time model reference control schemes for practical milling using different discretization of the continuous-time plant are presented. First, a basic controller scheme is addressed where a fractional order hold with pre-fixed value of the gain is used. Secondly, a multi-model scheme, which outputs different discretization in parallel with the continuous-time milling system transfer function under a fractional order hold (FROH) of correcting β ∈ [−1, 1], is dealt with. Then, an intelligent design framework is designed as a supervisory scheme with two hierarchical levels in order to find the most appropriate value for the gain β. For choosing the value of β, a tracking performance index is designed. It evaluates each pre-defined discretization of the continuous time milling transfer function and the scheme chooses the one with the smallest value of the index in order to generate the real control input to the plant. Two different methods of adjusting this value are presented and discussed. The first one selects a β-value among a fixed pre-defined set of possible values, while the second one the value of β is updated by adding or subtracting a small quantity.
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