Perfect Static Balance With Normal Springs

Abstract

In biomechanical engineering, gravity balancers are often used in orthoses carrying the weight of paralyzed limbs. In these applications, simplicity is an insuperable demand. However, known gravity balancers do not combine simplicity with perfect balance. This paper describes several gravity equilibrators providing perfect static balance. As opposed to many known solutions, the proposed balancers incorporate normal off-the-shelf springs, rather than the zero-free-length springs (springs with a length equal to zero when not preloaded or loaded externally) usually employed. The conceptional synthesis is presented, dimensional design criteria are derived, and prototypes are shown. Based on the prototype’s working principle, an ankle prosthesis, which stabilizes the patient, will be developed.

Spatial Static Gravity Balancing With Ideal Springs

“…As is also the case for planar static balancing spring-to-spring mechanisms [1][2][3][4][8][9][10][11], it is seen that the conditions for the three-spring balancer shown in Fig. 3 (eq.…”

Optimum Synthesis and Design of a Hood Linkage for Static Balancing in One-Step

“…Such a sequential design approach is also taken by many others found in the literature: A reactionless parallel mechanism by Faoucault and Gosselin [9]; a spherical parallel mechanism by Chaker et al [10]; a laparoscopic manipulator by Ma et al [11]; an anthropomorphic finger by Demers and Gosselin [12]; a crank-rocker flapping-wing micro air-vehicle by McDonald and Agrawal [13]; a geared four-bar mechanism by Parlaktas et al [14]; a planar manipulator by Mermertas [15]; a four-bar mechanism by Jaiswal and Jawale [16]. Spring-assisted mechanisms [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] are further examples of a long list of articles wherein the respective mechanisms are first designed/synthesized (Step 1) before optimization is performed (Step 2). The challenge is to reduce this design process to a single step: Both the mechanism synthesis and the optimization of the same, are performed together.…”

Energy-free adjustment of gravity equilibrators by adjusting the spring stiffness

“…Their properties can also be emulated in a variety of ways, over a limited range of motions [15] or by making use of special constructions, such as a pulley-and-string mechanism, or by inverting a compression spring [1]. Perfectly equilibrated mechanisms with conventional springs also exist [16], but the use of zerofree-length springs significantly eases the calculations. When designing the actual practical embodiments of the conceptual mechanical design, constructions to emulate their properties can be considered.…”