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

The definition of energy/coenergy in permanent magnets (PMs) is still in dispute when virtual work is used to compute magnetic forces using finite-element methods. There is also no current practical method for computing forces when PMs touch objects. 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.