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Reducing the flexspline (FS) deformation is important for decreasing the alternating stress, flare angle in the axial direction, spatial deformation of teeth, and tube length. However, it may increase the probability of insufficient engagement depth and nonexistent conjugate tooth profiles. In this study, a mathematical model of the harmonic drive (HD) with a new tooth profile is proposed to reduce the FS deformation while satisfying the engagement depth and existence of a conjugated tooth profile. First, the generation mechanism of the new tooth profile is discussed in detail and the connection method of the circular arc tooth profile and transition tooth profile in the FS were presented. Then, two key parameters of the model, the translation distance and offset distance were studied to design the ideal tooth profile. Finally, a tooth root chamfer method was proposed to achieve smooth operation of the HD. Additionally, owing to the lack of a wear assessment of the new tooth profile, a sliding coefficient calculation model was presented. To verify the feasibility of the models, a prototype with a radial deformation coefficient of 0.8 was designed, processed, and tested. The experimental results were consistent with the theoretical analyzes.

A harmonic reducer (HR) is widely used because of high precision, small size, light weight and a series of advantages. However, the disadvantage is that its transmission ratio is generally not less than 60. According to a market research study, more than 60% of the reducers have the transmission ratio of less than 60. This implies that the large transmission ratio restricts the HR from applications in the market demanding a small transmission ratio (20–60). In this study, a method is presented for designing the HR with the small transmission ratio as low as 20. First, by clarifying the principle of reducing the transmission ratio of the HR, a design model of two-wave HR tooth profile is deduced in detail, and a four-tooth difference HR is designed. Aiming at solving the problem that diminishing the radial deformation coefficient leads to the reduction of the engagement depth and the increase of the pressure angle of the tooth profile, a wave generator with a new profile is proposed. Then an optimization model based on the circular spline tooth profile to envelope the flexspline tooth profile is developed for achieving the twice-conjugated engagement. Based on manufacturing considerations, the theoretical tooth profile is fitted by involute based on a given numerical approximation method. Third, a finite element analysis is carried out to investigate the stress characteristics of small transmission ratio HR. Finally, a prototype with a transmission ratio of 20 is trial-produced and tested, which shows that the design methods can be applied for the small transmission ratio HR.

Kinematic error is an important indicator for evaluating the performance of harmonic drive gears. Previous methods for calculating the kinematic error only considered a single meshing tooth, the effect of other meshing teeth was compensated by the error homogenization coefficient. Because of the complex contact state of harmonic drive gears, the results of these methods are always inconsistent with experimental results. This paper proposes a mathematical model considering all meshing teeth to predict the pure kinematic error of harmonic drive gears. First, the contact points on each meshing tooth are determined, and the contact states of the flexspline and circular spline teeth are investigated. Then, the contact forces on the meshing teeth are obtained, and the pure kinematic error is calculated based on the relationship between the torque caused by the contact force on the left and the right tooth profiles. Finally, the mathematical model is validated by simulation and experimental methods. The study in this paper can not only be used to accurately predict the pure kinematic error but also is valuable in the selective assembly of higher precision harmonic drive gears.

In contact dispensing process including the extruding, stretching, and liquid-bridge breakup, the initial distance d n − s i n i between the needle tip and the substrate has great influence on the dispensed adhesive volume. Herein, the effect of d n − s i n i on the dispensing process in nano-liter level is studied for high-viscosity adhesive. Complete contact dispensing process is simulated using computational fluid dynamic technique. Moreover, the experimental platform including heating device, dispenser, and imaging unit etc. is built up to investigate the dispensing process. According to the results, with the increase of d n − s i n i , the variation of extruded adhesive volume can be divided into three regimes that are respectively dominated by different factors. As d n − s i n i is in the range of 45–75 μm, due to the spatial flow resistance decreasing, the extruded volume sharply increases. Then, when d n − s i n i is in the range of 75–115 μm, owing to the contact area sa-s between the extruded adhesive and the substrate continuing to decrease, the increase of extruded volume becomes slow. Once d n − s i n i reaches 115 μm, comparing to the decrease of sa-s, the contribution of spatial flow resistance can be neglected, thus the extruded volume will decrease until sa-s approaches to zero. Additionally, the following transfer process based on the liquid-bridge breakup is studied too. The variation of absolute transferred volume is consistent with that of the extruded volume. However, since sa-s continuously decreases with the increasing of d n − s i n i , the transfer ratio gradually decreases. The presented results can improve the precise contact dispensing process and other related techniques.

By converting the alignment issue of multiple span rotary shafts into a non-connected shaft alignment issue, we present a precision alignment strategy for multiple span shafts, and a laser-based method for measuring misalignment of non-connected shafts is proposed. The quadrant photodiode detector was calibrated at different rotation angles to obtain the sensitivity coefficient. According to the calibration results, the experiment scheme of the method was optimized. Then measurement experiments were carried out and the error source, the measurement uncertainty of the results were analyzed. Finally, the misalignment was also measured by a coordinate measuring machine, and the comparison results show that the relative error of the two methods is less than 5%. Therefore, the proposed method can be applied to align multiple span shafts accurately. Furthermore, this method can also be used for non-connected shaft position determinations such as wheel alignment inspections, alignment of machine spindle and center shaft, and others.

Harmonic-drive transmission finds many applications in industry, especially in manufacturing of industrial robots. As the key devices of an industrial robot, the harmonic drive reducers determine the robot’s performance, which includes the positioning accuracy, loading capacity, life time, etc. To satisfy the need of manufacturing high performance harmonic drive devices, development of competent measurement system is of great importance. An automatic measurement system with high-precision and multifunction is under development. The system consists of the power module, loading module, torque and rotation measuring module. The measurement and operation principle were explained. The factors affecting the accuracy of the measurement system were analysed. The control system was designed to realize the automatic loading and acquisition of torque and rotation data. The principle and measurement software of the control system were also introduced. Finally, a harmonic reducer with the gear ratio 120 was measured to verify the feasibility of the measurement system.

The functional information model of the technical system based on the component unit model is the basis of the analysis of computer aided function. Through the introduction of graph theory knowledge, establishing technical system function directed graph's adjacency matrix and reachable matrix. The establishment of technical system of multilevel advanced directed graphs can directly determine the technology system of internal parallel chain. Using the ENV model to analyze the causal relationship between the adverse effects in the chain, and to find the key adverse effect of solve the problem.