Coaxial negative torsion stiffness mechanism developed for compact gravity compensation
D.M. Mulder (TU Delft - Mechanical Engineering)
Jelle Rommers – Mentor (TU Delft - Mechatronic Systems Design)
J. L. Herder – Mentor (TU Delft - Precision and Microsystems Engineering)
T. Horeman – Graduation committee member (TU Delft - Medical Instruments & Bio-Inspired Technology)
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Abstract
The mechanism presented in this paper generates a partially negative stiffness characteristic, which is suitable for the balancing of a pendulum in a gravity field. The mechanism uses deformation in the axial direction of the base joint to store potential energy. The proposed design is located next to the base joint of the pendulum in an area rarely used by other balancing mechanisms. Utilising this space makes it an attractive alternative when space in the plane of motion is restricted. The mechanism consists of two linear springs and a non-linear transmission that form a compact system which can be manufactured out of tubes. The balancing curve that is generated by the mechanism has a theoretical maximum error of < 0:05% between ±22:5° around the horizontal position. The difference between the test results and the theory ranged from 0.4 % and 1.7 %. This gravity balancing mechanism is interesting when the mechanism should be located beside the base joint and or when low hysteresis and low error are required.