Gravity Compensation of Robotic Manipulators Using Cylindrical Halbach Arrays

Gravity compensation (sometimes referred to as static balancing) is achieved in a mechanism when the weight of its moving links does not produce any torque at the actuators for any configuration of the links. This condition yields many advantages such as a significant reduction of the torque needed at the actuators and easier control. Therefore, retrofitting an existing design to include gravity compensation can be greatly beneficial. However, current methods to achieve this goal are limited. The majority of them require the addition of auxiliary mechanisms that affect the performance of the robot. In the proposed concept, the concentric motion of Halbach cylinders is used for the first time to produce a joint torque that exactly compensates the torque produced by a gravitational load over a complete rotation of a revolute joint. The concept leads to a compact design that is easily integrated to an existing actuated joint. Using software to simulate the interaction between magnets, the active parameters are studied to approach optimal torque output. In order to demonstrate the viability of the proposed concept, a prototype is built and retrofitted to an existing manipulator.