Design and testing of a coaxial linear magnetic spring with integral linear motor

The design and testing of a coaxial linear magnetic spring with integral linear motor is presented. The magnetic spring offers the potential of replacing mechanical springs in long life applications. The integral linear motor allows the spring to be tuned to the system and overcome any system damping. The spring/motor magnet material is sintered SmCo5. Static and dynamic results are presented. Static measurements are consistent with predictions based on finite element (FEM) analysis. The radial side loads from such a spring/motor agrees with analysis and approaches the theoretical minimum value. The nominal design stiffness is 25,000 N/m with a design stroke of 0.46 cm. Dynamic tests indicate an energy storage efficiency of 91-94% (Q = 70-100) at 25 Hz.