A novel planetary thread roller bearing (PTRB) was proposed in this paper based on Herz theory combined with multiple principles (e.g. equivalent steel ball, multi-point meshing and power dividing). A significant improvement in load-carrying capacity, comparing the current bearing, was achieved and thus providing a new option for the advanced equipment with high thrust-to-weight ratio requirement. The newly proposed PTRB exhibited a 83 % increase in dynamic axial load rating while a comparable static axial load rating comparing with the thrust ball bearing with a comparable size. In addition, the relationship between friction torque and bearing rotating speed, contact point number and axial load was discussed. It was found that, given a proper installation space, increasing the thread roller number could not only significantly improve the axial load rating of PTRB, but also reduce the friction torque. Furthermore, the working efficiency of the new PTRB was constantly higher than 97 %. A self-degradation operation was achieved by the system when some thread rollers were stuck, which improved the system fault tolerance. Finally, friction torque tests were performed on the self-developed test instrument. The results showed a good agreement with the theoretical analysis.

In order to measure the friction torque of planetary thread roller bearings, a friction torque testing machine was developed based on the principle of transfer method. The test of dynamic friction torque and starting friction torque under axial and radial continuously adjustable large load conditions is realized. The test machine has good stability, and the test data are accurate and reliable, providing data support for in-depth understanding of the friction performance of planetary thread roller bearings.

With technological advances and industrial upgrading, high-performance equipment has put higher demands on the performance of electro-mechanical actuators. With a view to making electro-mechanical actuators more reliable and integrated, firstly, an integrated electro-mechanical actuator module (IEMM) with multiple structural forms was proposed in this paper, and a comparative analysis was performed on the characteristics of different transmission schemes. Then, the feasibility of manufacturing the IEMM’s main bearing components using Carbon Fiber Reinforced Polymer (CFRP) with higher specific stiffness, specific modulus and specific strength was demonstrated by finite element simulation (FEA) software, in a bid to further reduce the weight of the IEMM. Next, a parameter estimation model, a heating power calculation model, and a thermal resistance calculation model were built, so that there is no need to rebuild the whole system model under different demand indexes. On this basis, a multi-objective optimization design model was built with light weight, low power loss, and high level of integration as optimization aims to achieve better comprehensive performance in the early design phase of the IEMM system. However, IEMM’s higher level of integration and its shell made of CFRP with a thermal conductivity of less than 5 W/m°C posed a challenge to the heat dissipation of the motor stator. Therefore, a thermal network model needs to be created in AMESim to evaluate the temperature of IEMM’s parts and components under different working conditions. Finally, the process of IEMM performance optimization design was described and improved, and performance optimization design was conducted by taking one of IEMM’s transmission schemes as an example.

Robots are known as "the Pearl at the top of the crown of manufacturing." As the most common kind of robot, the multi-degree-of-freedom manipulator has its reliability, lightweight, integration, and modularization, which are the focus of researchers. Based on the background of injecting water into the EMU train, this paper uses the water feeding manipulator (WFM) to completely replace the manual operation and researches the key technology of the redundant manipulator system. At the component level, a new type of planetary thread roller bearing (PTRB) is used as the main bearing component of the manipulators’ joint. For joint, two integrated joint modules (IJM) are developed based on PTRB to be an option for IJM with a high power-weight ratio and high reliability. Finally, for the system, according to the fault-tolerant performance requirements of the task point, the redundant manipulator system architecture is proposed, the mechanical body is set as the redundant structure, the driver and controller are dynamically reconstructed, and the control algorithm and fault diagnosis are fault-tolerant. The failure rate is 3.257×10-8/h, laying the foundation for the realization of a fully automatic and intelligent train water supply.

Bearings, as integral parts and components in machinery and equipment, play a critical role in system performance. In this paper, the theoretical models of basic axial load rating, basic radial load rating, and friction torque for the planetary thread roller bearing (PTRB) were derived. Then, a detailed comparison was made between the performance indexes of a PTRB prototype and common high-quality bearing products to demonstrate the advantages of PTRB in volume, bearing capacity, and use method. Next, the effects of different structural parameters on the performance indexes of PTRB were analyzed. On this basis, a multi-objective optimization design was carried out on PTRB under axial load and radial load separately with basic load rating and friction torque as optimization objects to obtain PTRB with superior comprehensive performance. Designers could, in consideration of their specific needs and optimized design results, select the structural parameters of PTRB. Furthermore, a dedicated performance test system was researched and developed, which verified the good static bearing capacity and impact resistance of the PTRB prototype. Within the range of dynamic load rating, the test data were slightly larger than the simulation data for the friction torque, manifesting a relatively high degree of precision of the theoretical model.