In accordance with the developing trend of “safety, comfort and low-carbon” technology, the market for intelligent X-by-wire chassis is huge. A new requirement of the X-by-wire system, including the response, accuracy, energy consumption and fault-tolerance, is put forward. Based on the analysis of the structure and design flow of the brake-by-wire (BBW) system, this paper analyzes the research status and development trend of the control methods of braking force, coordination control strategies and fault-tolerant control of the BBW system. The application possibilities of direct-driving technology in the BBW system are analyzed. At present, the key points of research focus on considering the influence of the multi-field coupling effect in the design, observing and compensating various nonlinear factors, and having a higher requirement for fault-tolerant control. Finally, an intelligent direct-driving BBW system is proposed as a research direction, which takes high efficiency and energy saving as a foothold and aims at breakthroughs in dynamic response, control accuracy and fault-tolerant abilities.

Currently, the preparations of high-entropy alloy (HEA) coatings have developed into new methods such as thermal spraying, electrospark deposition technology, and magnetron sputtering. The microstructures and protective properties of HEA coatings prepared by different methods are bound to be different. Moreover, because HEAs have a wide range of composition systems, the difference in composition will inevitably lead to a change in process parameters and post-treatment methods, and then affect the microstructures and protective properties. This paper introduces the working mechanism of thermal spraying, electrospark deposition technology, and magnetron sputtering, compares the advantages and disadvantages of each method, and focuses on the influences of the compositions, process parameters, and post-treatment process on the microstructures and properties of the coating. Furthermore, this paper outlines the correlation between preparation methods, process parameters, microstructures, and properties, which will provide a reference for further development of the application of high-entropy alloy coatings. On this basis, the future development direction of HEA coatings is prospected.

A thermal model of bi-stable permanent magnet actuator (BPMA) was established and verified using multiphysics methodology. By treating the non-simplified energy consumption distribution as the heat source for temperature field calculation, the established thermal model adjusts the material properties by temperature and considers the interaction between motion and loss. The distribution and change of loss and temperature rising were quantitatively analyzed. Moreover, a design method for electrical parameter was proposed under thermal constraints based on quantitative analysis. The results showed that armature iron loss and coil copper loss accounted for 24.7% and 42.8% of the total loss, respectively, which could be regarded as the main components of heat source. The balance temperature of armature was the highest, followed by that of coil, cover, sleeve and PMs. The limiting temperature of the actuator was equal to PM's limiting temperature. Through electrical parameters optimization design, the prototype met the requirement of continuous working time under limiting temperature, with the response time decreased by 6.9%. In addition to being applied to BPMA, the proposed method can be used for analysis and design of a wide range of electromagnetic actuators.

The electromagnetic linear actuator is used as the core drive unit to achieve high precision and high response in the direct-drive actuation system. In order to improve the response performance and control accuracy of the linear drive unit, an improved sliding mode-active disturbance rejection control (ISM-ADRC) method was proposed. A motor model was established based on improved LuGre dynamic friction. The position loop adopts the improved integral traditional sliding mode control based on an extended state observer, and the current loop adopts PI control. The stability of the system is verified based on the Lyapunov theory. A nonlinear dilated state observer is used to effectively observe the electromagnetic linear actuator position and velocity information while estimating and compensating the internal and external uncertainty perturbations. At the same time, the saturation function sat(s) is used to replace the sign(s) and introduce the power function of the displacement error variable. The improved integral sliding mode control law further improves the response speed and control accuracy of the controller while reducing the jitter inherent in the conventional sliding mode. Simulation and experimental data show that the proposed improved sliding mode-active disturbance rejection control reduces the 8-mm step response time of the electromagnetic linear actuator by 21.9% and the steady-state error by less than 0.01 mm compared with the conventional sliding-mode control, while the system has 49.4% less adjustment time for abrupt load changes and is more robust to different loads and noise.