Magnetic force computation in permanent magnets using a local energy coordinate derivative method

Abstract—The definition of energy/coenergy in permanent mag- nets (PMs) is still in dispute when virtual work is used to compute magnetic forces using finite-element methods. There is also no cur- rent practical method for computing forces when PMs touch ob- jects. These problems are addressed in this paper in terms of a new definition of energy/coenergy in PMs and by using shell elements. The results are verified by analytical computations. Index Terms—Electromagnetic fields, electromagnetic forces, fi- nite-element method, permanent magnets, virtual work.