A Reconfigurable Halbach Cylinder for Gravity Compensation of Variable Rotational Payloads

Abstract Traditional counterweight- and spring-based gravity balancers typically require additional mechanical arrangements to facilitate variable-payload balancing. While magnet-based balancers offer compact and efficient solutions, most existing designs are limited to fixed payloads. This article presents a magnet-based gravity balancer, based on a reconfigurable Halbach cylinder, for rotational systems with variable payloads. The system integrates a central permanent magnet with a surrounding array of eight diametrically magnetized cylindrical magnets, whose orientations are controllable via a simple gear train to modulate the magnetic flux. The reconfigurable design supports a broad range of balancing modes through continuous magnetic-force modulation, ranging from fully off to maximum strength. The concept was validated through finite-element modeling, prototype fabrication, and experimental testing. Magnetic torques associated with balancing and reconfiguration were measured and compared with simulation results. Notably, experimental results show that the system enables nearly energy-free adjustment for payload adaptation when the payload arm is constrained in the horizontal position. This study demonstrates the feasibility of using reconfigurable Halbach arrays for variable-payload gravity compensation, offering a compact and adaptable solution for applications such as robotic manipulation, assistive devices, and precision mechanical systems.