Principles from origami art are applied in the design of mechanisms and robotics increasingly frequent. A large part of the application driven research of these origami-like mechanisms focuses on devices where the creases (hinge lines) are actuated and the facets are constructed as stiff elements. In this paper, a design tool is proposed in which hinge lines with torsional stiffness and flexible facets are used to design passive, instead of active mechanisms. The design tool is an extension of a model of a single vertex compliant facet origami mechanism (SV-COFOM) and is used to approximate a desired moment curve by optimizing the design variables of the mechanism. Three example designs are presented: a constant moment joint (CMJ), a gravity compensating joint (GCJ) and a zero moment joint (ZMJ). The CMJ design has been evaluated experimentally, resulting in a root-mean-squared error (RMSE) of 6.4 × 10 −2 N·m on a constant moment value of 0.39 N·m. This indicates that the design tool is suitable for a course estimation of the moment curve of the SV-COFOM in early stages of a design process.

A gravity equilibrator is a statically balanced system which is designed to counterbalance a mass such that any preferred position is eliminated and thereby the required operating effort to move the mass is greatly reduced. Current spring-to-mass gravity equilibrators are limited in their range of motion as a result of constructional limitations. An increment of the range of motion is desired to expand the field of applications. The goal of this paper is to present a compact one degree-of-freedom mechanical gravity equilibrator that can statically balance a rotating pendulum over an unlimited range of motion. Static balance over an unlimited range of motion is achieved by a coaxial gear train that uses noncircular gears. These gears convert the continuous rotation of the pendulum into a reciprocating rotation of the torsion bars. The pitch curves of the noncircular gears are specifically designed to balance a rotating pendulum. The gear train design and the method to calculate the parameters and the pitch curves of the noncircular gears are presented. A prototype is designed and built to validate that the presented method can balance a pendulum over an unlimited range of motion. Experimental results show a work reduction of 87% compared to an unbalanced pendulum and the hysteresis in the mechanism is 36%.

Recently, there has been an increased interest in origami art from a mechanism design perspective. The deployable nature and the planar fabrication method inherent to origami provide potential for space and cost-efficient mechanisms. In this paper, a novel type of origami mechanisms is proposed in which the compliance of the facets is used to incorporate the spring behavior: compliant facet origami mechanisms (COFOMs). A simple model that computes the moment characteristic of a single vertex COFOM has been proposed, using a semispatial version of the pseudo-rigid-body (PRB) theory to model bending of the facets. The PRB model has been evaluated numerically and experimentally, showing good performance. The PRB model is a potential starting point for a design tool which would provide an intuitive way of designing this type of mechanisms including their spring behavior, with very low computational cost.

Static balance can be applied to improve the energy efficiency of mechanisms. In the field of static balancing, there is a lack of knowledge and design methods that are capable of dealing with torsional stiffness. This paper presents a design approach for statically balanced mechanisms, with the focus on mechanisms with torsional stiffness. The approach is graphical in nature and is based on the requirement of constant potential energy. The first achievements of this approach are presented as two conceptual designs of different types of mechanisms. One of them is developed further into a prototype and tested. The prototype has a correlation coefficient of 0.96 and a normalized mean squared error of 0.12 with respect to the mechanical model of the conceptual design.