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.

Automated mechanical transmission has many advantages such as simple structure, high mechanical efficiency, and low cost. But the poor gearshift performance restricts the massive application of the automated mechanical transmission, and it can be improved through innovation of structure and control. To reduce the requirement of shift force and improve the shift performance, a new direct-drive electromagnetic gearshift system which consists of servo synchronizer and 2-degree-of-freedom electromagnetic actuator is adopted. The specific structure and working principle of the gearshift system including servo synchronizer are described, and the equation of force-amplifying ratio is deduced. Due to the complexity of the gearshift system and uncertainties of the gearshift process, active disturbance rejection control method is designed. The active disturbance rejection controller can eliminate the nonlinearity of the 2-degree-of-freedom actuator. The extended state observer can estimate and compensate the uncertainties, parameter variations, and external disturbances. Simulations are carried out, and the result comparison with proportional–integral–derivative controller indicates the superiority of the active disturbance rejection control method. Test bench and control system are developed to verify the performance of the newly designed system and control method. The experimental results show that, when the gearshift system is equipped with servo synchronizer, the driving force and the maximum volatility of driving force can be reduced by 35% and 5%, respectively, and the impact generated by active disturbance rejection control method is reduced by 36% compared with proportional–integral–derivative method. The new gearshift system achieves a better gearshift performance. Combined with the newly designed control strategy, the direct-drive electromagnetic gearshift system provides a new solution for automated mechanical transmission applications.