An angular encoder that can detect angular motion with ultrahigh accuracy is needed to enhance the precision for the angular motion axis of computer numerical control (CNC) machine tools. Although a self-calibration method based on mounting multiple detecting heads has been proposed, it is impractical because the number of detecting heads needed to calibrate higher-order terms of the error components corresponds to the order. This paper presents a new self-calibration method for an angular encoder that uses fewer detecting heads. The method was compared with existing methods via simulation to confirm its feasibility. A prototype angle encoder was produced with six detecting heads to calibrate error component terms up to the 30th order. The error curves of the six sensor heads of the prototype encoder system were used to achieve a motion detection accuracy of ±0.07 s.
Noise is one of major serious issues for planetary gear trains (PGTs). It is called noise hazard in serious cases such as cabin in a helicopter where the sound level reaches 100dB. In this paper, several precisions of planet gears are combined to investigate the influence of tooth precision on meshing noise of PGTs. The meshing noise of PGTs is generated by stiffness coefficient excitation and error excitation forces, but stiffness coefficient excitation is assume to be constant in this paper because slight error on the tooth surface doesn't effect on meshing stiffness. It was found that maintaining the same precision for all planet gears is the best; if one of the planet gears has a precision far from the others, the sound pressure level increases. The deviation for the maximum error among all meshing pairs, should be restricted to no more than 3μm in case of module one spur gear.
Recently, a longer life and advanced functions of artificial joints are required. To improve the fixation of the artificial joint, we propose a generation method of a model with a porous structure based on a triangular mesh on the surface layer. The three-dimensional model is parameterized using the ABF method, and equilateral triangles spread on the plane are projected onto the surface of the three-dimensional model. For models that can not be appropriately parameterized by the ABF method, we propose a method to improve the ABF method by adding a constraint condition using rotation symmetry of regular triangle texture.
3D laser scanners have recently been introduced for efficient as-built modeling in the heating, ventilating and air conditioning (HVAC) industry. Given their highly complex installation, when scanning the piping objects in HVAC systems using a terrestrial laser scanner (TLS), it is difficult to manually determine feasible scanner placement to capture the object areas required for renovation work at high accuracy and quality without occlusion. We propose an algorithm for a model-based optimum scan planning method for a TLS. This method uses a coarse 3D model generated by structure-from-motion, and finds optimal scanner placement that satisfies visibility, scan range, incident angle, and scan quality constraints. In this study, the optimal scanner placement problem is formulated as a 0-1 integer programming problem that is solved using the branch and bound method. In addition, a GPU significantly increases the speed of the precomputation of visibility constraints. In an evaluation, the proposed algorithm outperformed our previously proposed greedy method in terms of the number of scans and scan coverage ratio, and it shows performance equal to the greedy method in terms of modeling quality.
A desktop friction stir spot welding (FSSW) system was designed and developed for the micro joining application. This system consisted of a high-speed air spindle, a PC-controlled translation stage, and a force sensor-integrated sample holder. The probe-less tools with taper-shaped head were prepared for the joining experiment. The developed system enabled the lap joints between copper (thickness: 0.1 mm) and aluminum (0.2 mm) sheets. In optimum conditions, the well-stirred zone, which exhibited laminated structure of thin copper and aluminum layers was observed at the joint interface. In this area, the formation of intermetallic compound was not observed. In addition, the fluctuation of tool load in the penetrating operation was measured. The tool load exponentially increased as the tool penetration, and rapidly turned downward even though the tool was continuously penetrated. The turning point in tool load curve implied the material softening and plastic flow initiation. Therefore, the force curve measured during tool penetration will be used as an estimation criterion for the joint quality formed by FSSW.