Due to their advantages of compact size, high reduction ratio, large stiffness and high load capacity, RV reducers have been widely used in industrial robots. The dynamic characteristics of RV reducers in terms of vibratory response and dynamic transmission error have a significant influence on positioning accuracy and service life. However, the current dynamic studies on RV reducers are not extensive and require deeper study. To bridge this gap, a more effective and realistic lumped parameter dynamic model for RV reducers is developed, considering the tooth profile modification of cycloid gears and system errors. Firstly, for an efficient solution, the equivalent pressure angle and equivalent mesh stiffness of the cycloid–pin gear pair are introduced in the dynamic model based on the loaded tooth contact analysis. Secondly, the differential equations of the system are derived by analyzing the relative displacement relationships between each component, which are solved using the Runge–Kutta method. With this, the effects of errors such as machining errors, assembly errors and bearing clearances on the dynamic behaviors and transmission precision are investigated by comparison to quantify or qualify their influence. This research is helpful in characterizing the multi-tooth mesh and dynamic behavior, and revealing the underlying physics of the RV reducer.

Cycloid drives are widely used in various mechanical systems due to their high reduction ratio, compact size, and high efficiency. Tooth surface wear is a major problem that affects the reliability and durability of cycloid drives. However, compared to the research on the wear of involute gears, the prediction of tooth surface wear in cycloid drives is relatively limited and less extensive. To fill this gap, the theoretical wear model of the tooth surface of cycloid-pin gear pairs is proposed based on the Hertz contact theory and Archard’s formula, with consideration of tooth profile modifications. Firstly, the loaded tooth contact analysis model is established to determine the relative sliding velocity and tooth contact stress. Secondly, the calculation steps of single tooth surface wear are presented within one gear mesh cycle. With this, the effects of the tooth profile modifications, the operating conditions such as output torque, input speed, and the assembly eccentricity on the wear depth within one gear mesh cycle are investigated. This study gives a deeper understanding of the tooth surface wear mechanisms of cycloid drives and could be employed to assist gear design and to improve the wear resistance.

In the field of intelligent driving of freight trains, determining the track line ahead of the train is an important function in the autopilot technology of such trains. Combining the characteristics of freight railway tracks, we conduct an in-depth analysis of the shortcomings of object detection technology in extracting track lines and propose an improved Zhang–Suen (ZS) thinning theory for a railway track line recognition algorithm. Through image preprocessing and single pixel thinning steps, a continuous track line is obtained and then processed by a denoising algorithm to obtain a complete track line. Experimental results show that the track extracted by our method has good continuity and less noise. It can simultaneously perform track detection on straight roads, curves and turnouts, and is suitable for changing weather conditions such as sunny daytime, mild rainy daytime, cloudy daytime, night with lamp lighting and night without lamp lighting conditions.

Titanium alloy is a crucial structural material in the modern aerospace field due to its strong corrosion resistance and strength, low density, and reduced sensitivity to vibration load and impact load, as well as its ability to resist expansion in the case of cracks. However, during high-speed cutting of titanium alloy, it is prone to periodic saw-tooth chip formation, which can cause high-frequency fluctuations in the cutting force, aggravate the vibration of the machine tool system, and ultimately reduce the tool’s service life and the workpiece’s surface quality. In this study, we investigated the influence of the material constitutive law in modeling the Ti-6AL-4V saw-tooth chip formation and proposed a joint material constitutive law JC-TANH which was developed based on the Johnson–Cook constitutive law and the TANH constitutive law. It has two advantages of the two models (JC law and TANH law), which means that it can describe the dynamic properties accurately, the same as the JC model, not only under low strain but also under high strain. The most important thing is that it does not need to fit the JC curve at the early stage of strain changes. Additionally, we established a developed cutting model, which integrates the new material constitutive, and the improved SPH method to predict chip morphology, cutting and thrust forces which are collected by the force sensor; we also compared the data with experimental results. Experimental results show that this developed cutting model can better explain the shear localized saw-tooth chip formation and correctly estimate its morphology as well as the cutting forces.

Electrohydrodynamic-jet (E-jet) printing is an on-demand additive manufacturing method that allows various functional materials to be directly deposited on the target substrate. Many theoretical and experimental results indicate that E-jet has scale effect, and reducing the inner diameter of the nozzle can effectively improve printing resolution. Herein, a method for fabricating SU-8 polymer micro/nanoscale nozzle by oxygen plasma assisted room temperature bonding was proposed. It can prevent channel deformation and blockage caused by excessive bonding temperature. The surface modification parameters of silicon nano-mold were optimized, the influence of hot embossing parameters on the replication precision of nano patterns was investigated, the effect of UV lithography parameters on the micro and nanochannel was analyzed, the relationship between the oxygen plasma treatment parameters on the contact angle of SU-8 was revealed, the influence of bonding pressure on the morphology of the nanochannel was discussed, and the bonding principle at room temperature was deeply analyzed. This method can fabricate SU-8 polymer micro/nanoscale nozzle with low cost and high precision, and provide a new idea for the realization of room temperature bonding to manufacture SU-8 polymer nozzle.

In recent years, with the development of robot transmission technology, the market demand for high-performance actuators, which can be applied to lower limb exoskeleton assist robots, is increasing. These robots help achieve human–robot interaction through rigid and flexible coupling, and they can ensure the flexibility of the elderly or patients in daily walking and rehabilitation training. A novel actuator with a double-roller gear drive structure is proposed with high bearing capability and high transmission efficiency due to multi-tooth rolling contact with small tooth difference such that friction is greatly reduced in the transmission process compared to what occurs in involute planetary transmission. The bearing capacity of the tooth surface was analyzed by using the loaded contact analysis method. Finally, a prototype was manufactured with the 3D printer, and the maximum output torque of the developed actuator was tested with an experimental setup. The results show that this novel actuator, with its double-roller gear drive, has huge potential for use in the hip joint of an exoskeleton robot.