Tubular PM machine with large force density and small force ripple for resonance operation

One main target in modern design of mobile working machines is the reduction of hydraulic oil in the on board actuator systems. This results in making the systems more environmentally friendly and leads to the idea of replacing the hydraulic actuators by electric actuators. Here this approach is presented by implementing electrical tubular linear actuators in a sickle bar, which is coupled with a mass-spring-system. To gain maximum energy efficiency the actuator is operated in resonance. By considering the limited construction space and the resonance operation, an electric machine with large force density and small force ripple is required. The requirement of large force density leads to the selection of a tubular machine fitted with permanent magnets in the moving part. It works with a 3-phase winding of maximum winding factor and the electromagnetic design results in a mover with flux-collecting effect. To fulfill the requirement of small force ripple over the whole operation range, the technique of axial skew (pole shift) is implemented and analyzed via simulation.