Analysis of electromagnetic-thermal coupling braking properties of combined electromagnetic friction and shape memory alloy brake

Abstract

To address the problems of severe heat generation and poor stability of traditional electromagnetic friction brakes, combined electromagnetic friction and shape memory alloy braking method is proposed. This novel brake solves the traditional electric brake thermal decay problem based on the temperature sensing ability of shape memory alloy, which improves its working stability in a high-temperature environment. Based on Ampere's law of magnetic field, the relationship between current and electromagnetic force was established, and the equation of electromagnetic force braking torque was derived. Based on the thermodynamic model of a shape memory alloy, the relationship between the frictional torque of shape memory alloy and parameters such as temperature, squeezing pressure, and structure size was established. The magnetic and thermal fields of this brake were analyzed by the finite element method to obtain the magnetic field distribution and the magnitude of electromagnetic force at different currents and to derive the temperature distribution of the brake at different currents. The brake was analyzed by the shape memory alloy squeezing pressure test platform and the braking performance test platform. The results show that the electromagnetic torque grows non-linearly with temperature, and the squeezing force generated by the shape memory alloy spring increases with temperature. When the current is 0.7A, the braking torque generated by electromagnetism is 170.3N·m, while the maximum braking torque generated by the combination of electromagnetism and shape memory alloy is 212.6N·m, which is 20.4% higher than that of the traditional electromagnetic friction brake. This novel brake improves braking performance and ensures stable braking performance under temperature rise.

Analysis and experimentation of variable gap magnetorheological transmission device driven by electromagnetic force

“…Where, μ r is the relative permeability. In equation (3), the magnetic flux density B without characteristics of divergence and curl, the vectorial magnetic potential A is introduced, substituting equation (2) and equation (3) into equation (1) to obtain the equation for static magnetism in the presence of a free space magnetic field, which can be expressed as: (Gong et al, 2022)…”