OPTIMUM SYNTHESIS OF PATH GENERATING ADJUSTABLE MECHANISMS WITH IMPROVED SLOPE CONTINUITY OF THE CONTROL PARAMETER

Adjustable mechanisms have been studied in literature for path and function generation. In this paper, a path generating four-bar mechanism with an alternate single parameter adjustment is proposed and optimally synthesized, using the method of Differential Evolution. Two new approaches are developed, aimed at improving the slope continuity characteristic of the control parameter. Optimum synthesis results are obtained using the proposed approaches. The results show that the proposed approaches lead to improved slope continuity characteristics of the control parameter.

The Novel Adjustable Mechanisms for Exact Multi-Path Generation

A design method of the novel adjustable mechanisms is presented for exact multi-path generation. A novel adjustable mechanism with minimal structure error corresponding to required exact paths and with a rotational input link and a linear input link is proposed also. The derivations of instantaneous displacement of the linear input link corresponding to angular displacement of the rotational input link are proposed as well. The required exact paths can be generated by varying the instantaneous displacement of linear input link while rotational input link rotates with a constant angular speed in a cycle. The design procedure of this proposed method is presented either. The examples are provided to verify the feasibility and effectiveness of this proposed method.

Analytical Synthesis of Adjustable Dyads and Triads for Designing Adjustable Mechanisms

The paper presents generalized analytical methods for designing adjustable mechanisms based on synthesis of adjustable dyads and triads. The synthesis methods presented here are extensions of the well-known Burmester precison point theory. The adjustable dyad (and traid) synthesis method enables one to design mechanisms for multiple sets of precision points (multiple tasks). Two or more adjustable dyads (or triads) assembled together to form four-bar or geared five bar mechanisms that meet the requirements of multiple tasks. The method generates all adjustable -dyad and -triad solutions for given sets of precision points. Synthesis formulations and the solution spaces are described in detail. Design examples illustrating the synthesis methods are also presented.

Generalized Synthesis of Adjustable Mechanisms

Conventional mechanisms (cams, gears, and linkage-based that are typically single degree of freedom) are being increasingly replaced by multi-degree of freedom multi-actuators integrated with logic controllers. This new trend in sophistication although provides greatly enhanced flexibility, there are many instances where the flexibility needs are exaggerated and the associated complexity is unnecessary. On the other hand, the conventional mechanisms cannot fulfill multi-task requirements due to lack methods to design-in flexibility. Adjustable mechanisms or “programmable” mechanisms provide a cost-effective middle ground between hard automation and overly flexible expensive robots; especially for tasks that demand only limited flexibility. This paper presents a generalized synthesis procedure for designing adjustable robotic mechanisms for path generation. The goal is to develop a methodology to synthesize a single mechanism that can trace a given set of three-dimensional trajectories by simply adjusting one of the mechanism parameters; say the length of a particular link. The synthesis procedure presented in this paper entails coupler curve classification and pattern recognition techniques, eleven precision-point (Burmester theory) synthesis of geared five-bar mechanisms, multi-objective optimization and statistical analysis.