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Small-modulus gears, which are essential for motion transmission in precision instruments, present a measurement challenge due to their minuscule gear gaps. A high-precision measurement method under the influence of positioning errors is proposed, enabling precise evaluation of the machining quality of small-modulus gears. Firstly, a compound measurement platform for small-modulus gears is developed. Using a 3D model of the measurement system, the mathematical relationships governing motion transmission between various components are analyzed. Secondly, the formation mechanism of gear positioning error is revealed and its important influence on measurement accuracy is discussed. An optimization method for spatial coordinate transformation matrices under positioning errors of gears is proposed. Thirdly, the study focuses on small-sized gears with a modulus of 0.1 mm and a six-level accuracy. Based on the aforementioned measurement system, the tooth profile measurement points are collected in the actual workpiece coordinate system. Then, gear error parameters are extracted based on the established models for tooth profile deviation and pitch deviation. Finally, the accuracy and effectiveness of the proposed measurement method are verified by comparing the measurement results of the P26 gear measuring center. [ABSTRACT FROM AUTHOR]

Contact stiffness and backlash in the harmonic drive significantly impact a robot's positioning accuracy and vibration characteristics. The height of the harmonic drive tooth pair is typically less than 1 mm, making the measurement and modeling of backlash and contact stiffness inherently complex. This paper proposes a contact stiffness and backlash model by establishing a correlation between fractal parameters and tooth contact load. To obtain the fractal roughness parameters of the real machined tooth surface, a combination of a noncontact optical profiler and the RMS method is employed. Subsequently, the study explores the influence of rough tooth surface and contact force fractal parameters on contact stiffness and gear backlash. The results demonstrate the substantial impact of surface topography parameters and contact force on contact stiffness and backlash. Specifically, an increase in the fractal dimension correlates with a reduction in gear backlash and contact stiffness. Conversely, the fractal roughness parameter exhibits the opposite effect. Notably, an increase in contact force enhances contact stiffness. [ABSTRACT FROM AUTHOR]

This paper provides a comprehensive exploration of the operational mechanism of an internal feedback hydrostatic turntable. It employs a self‐compensating gap restrictor mechanism, resulting in heightened load capacity and stiffness. In this paper, the concept of internal flow is innovatively introduced. Subsequently, the Reynolds equation is solved using the finite difference method. This methodology offers a more precise and efficient assessment of the load‐bearing performance of the oil pad within the turntable. Then this paper further investigates the influence of the internal flow coefficient and pressure ratio on oil pad performance, encompassing aspects like load capacity, stiffness, and flow rate. Ultimately, optimal parameters are selected to improve the structure of the gap restrictor, considering various operational scenarios. In conclusion, the method adopted in this study not only improves the calculation accuracy and efficiency but also improves the structure and performance of the oil pad. [ABSTRACT FROM AUTHOR]

The two main failure modes of harmonic reducers are wear and contact friction between the tooth profile of the circular spline (CS) and the flexible spline (FS). The sliding speed of the meshing point is a key factor affecting friction and wear processes of the CS and FS and should therefore be accurately determined. Herein, envelope theory is used to deduce the FS trajectory and the envelope track is divided into two segments according to whether or not the meshing point is outside the top circle of the CS. The velocity of the meshing point in the second meshing stage is essentially the vector sum of the FS velocity in three directions. When the CS is fixed, the relative sliding velocity is the instantaneous velocity of the FS along the tangential direction of the enveloped tooth profile. To verify the proposed model, the finite element method (FEM) and laser sensor experiments were performed and a relationship between the angle of rotation of the wave generator (WG) and the velocity of the FS was established. The results show that the sliding speed is sensitive to the radial displacement coefficient and has a linear relationship with the rotational speed of the WG. [ABSTRACT FROM AUTHOR]

Disassembly plays an important role in the production process. Screw automatic unfastening guided by a robot has been widely used in the fields of industrial manufacturing and maintenance. Different from the previous studies that have used a flexible effector and expensive sensors, this paper presents a novel unfastening strategy based on robot vision for a hexagonal screw with an arbitrary loose state. In a robotic system, an industrial camera and a servo unfastening tool are installed at a robotic end-effector. The main contributions of this work are as follows. A camera pose adjustment method is proposed to obtain high-quality images of a target screw. The hexagonal screw pose calculation method based on the geometric analysis is developed to complete the screw–tool engagement. The cooperated motion of a robot and an unfastening tool is planned for the screw unfastening action. The effectiveness of the proposed control strategy is verified by experiments, and the influence of the motion speed on the unfastening quality is analyzed using the torque data collected by the unfastening tool. The analysis results can provide a significant foundation for the motion parameter selection in the proposed strategy. [ABSTRACT FROM AUTHOR]