Research On Performance And Control Strategy Of A Nested Two-rotor Permanent Magnet Retarder

Permanent magnet retarder,as an auxiliary braking device to ensure the stability of braking efficiency of medium and large trucks,provides effective braking torque in long distance downhill and continuous acceleration and deceleration roads that require long braking conditions.In the market share,due to the large volume,chassis installation height limit and other factors,only loaded on some large buses,in addition,the output range of braking torque is greatly affected by speed fluctuations,torque converter control is not accurate,and the temperature rise during work greatly affects the braking performance.In view of the above problems,the structure optimization,braking torque output characteristics and braking control strategy of traditional permanent magnet retarder are studied in this paper.Firstly,the working principle of permanent magnet retarder is studied.Aiming at the problems of large volume of traditional permanent magnet retarder and small torque control range,a nested two-rotor permanent magnet retarder structure is proposed.The theory of electromagnetic field in eddy current region of retarder was analyzed,and the calculation formula of braking torque based on the analysis of equivalent magnetic circuit method was derived.Halbach array permanent magnet was selected to enhance the magnetic field of working side,and then the overall basic structure was determined according to the transmission scheme.Parametric scanning optimization design and intelligent optimization algorithm were used to optimize the components and determine the final parameters.Compared with traditional structure,the axial length is reduced by nearly 24% and the radial size by about30%.The magnetic field simulation software ANSYS Electronics Desktop was used to simulate the magnetic field,including static magnetic field distribution,transient magnetic field change curve and braking torque output characteristics,to further verify the rationality of the structure design.The output eddy current loss calculation results were linked in Workbench,and the bidirectional magnetic thermal coupling simulation was carried out to study the heating state of retarder at different speeds,and the temperature distribution cloud diagram of eddy current ring was analyzed.Three braking control schemes and strategies are proposed according to different actual road conditions of vehicles.In Simulink,constant speed control planning strategy is output based on fuzzy algorithm,control strategy model is established to verify the effectiveness of the strategy,and theoretical curve of braking speed control is output,which has certain reference value for the study of nonlinear control of permanent magnet retarder.The precise axial feed of stator can be controlled by mechanical transmission.Compared with previous products,the volume of the embedded double-rotor permanent magnet retarder designed in this paper is greatly reduced,and it can provide the required braking torque stably.It is suitable for the installation of small and medium-sized passengers and trucks,and has great market value and application prospect.