A Novel Large-Stroke Constant Force Mechanism

mechanism design

robotics

control

This work presents the design of a novel adjustable constant-force mechanism (CFM) using a geared Sarrus linkage and a linear spring. The uniqueness of this design is that it provides a constant force over a wide range of displacement and the constant-force level can be adjusted energy-freely by varying the spring position without a preload. In this work, the construction, geometric constraints, and constant-force design of the CFM are expressed. The desired parameters of the mechanism, with consideration of gear friction, are also determined. A numerical example is then given to illustrate the constant-force performance and the effect of gear friction. This paper also shows a prototype of a CFM and experimental studies on it. It was found that the CFM delivered a constant force of up to 20 N within a stroke of 140 mm, and the force error was less than 6%. Moreover, the CFM compensated for masses of 1 and 2 kg with a torque reduction of more than 90%.

Published

May 26, 2023

Featured in [1] and [2].

References

[1]

V. L. Nguyen, “A novel adjustable constant-force mechanism based on spring and gear transmission,” in New advances in mechanisms, transmissions and applications, 2023, pp. 382–391.

[2]

V. L. Nguyen, “Design of an adjustable constant-force mechanism using a geared sarrus linkage and spring,” Mechanism and Machine Theory, vol. 189, p. 105417, 2023, doi: https://doi.org/10.1016/j.mechmachtheory.2023.105417.