Design of a Nonlinear Stiffness Unit Cell Aided Magnetic Gravity Compensator

Abstract

A novel nonlinear stiffness unit cell aided magnetic gravity compensator is proposed for the purpose of isolating low-frequency vibrations. A negative stiffness magnet setup is combined with a compliant unit cell with tailored nonlinear force-displacement characteristics. This combination offers a large range of motion featuring low stiffness, a high force density, and passive stability, creating a large vertical displacement passive magnetic gravity compensator (LVDPMGC). The passive stability of the system eliminates the need for active stabilization, reducing costs and complexity. An adjustable load-bearing capacity can be obtained by changing the number of unit cells, increasing scalability compared to conventional magnetic gravity compensators (MGC's) which have a fixed load-bearing capacity. The stiffness characteristics of the unit cell and magnet setup are analysed with FEM, showing which parameters influence system performance. Parameters are iteratively adjusted after which a prototype is manufactured and tested. The experimental results show that the unit cell can effectively stabilize the magnet setup while increasing the low stiffness range of motion, force density, and scalability compared to conventional MGC's.