Shape Optimization of Slider-crank Mechanism

Abstract: – In this paper, a two stage optimization technique is presented for optimum design of planar slider-crank mechanism. The slider-crank mechanism needs to be dynamically balanced to reduce vibrations and noise in the engine and to improve the vehicle performance. For dynamic balancing, minimization of the shaking force and the shaking moment is achieved by finding optimum mass distribution of crank and connecting rod using the equimomental system of point-masses in the first stage of the optimization. In the second stage, their shapes are synthesized systematically by closed parametric curve, i.e., cubic B-spline curve corresponding to the optimum inertial parameters found in the first stage. The multi-objective optimization problem to minimize both the shaking force and the shaking moment is solved using recently developed evolutionary optimization algorithms–“Teaching-learning-based optimization algorithm (TLBO)”. The computational performance of TLBO is compared with another evolutionary optimization algorithm (genetic algorithm).

Keywords: Dynamic balancing, Equimomental system, Link shape, Optimization, Slider-crank mechanism, Teaching learning-based optimization algorithm

I. INTRODUCTION

Slider-crank mechanism consisting of crankshaft, connecting rod and piston is the fundamental mechanism used for vehicle engines. The shaking force and shaking moment in the mechanism are defined as the resultant inertial forces and moments of the moving links [1] and need to be eliminated to dynamically balance the mechanism. For an unbalanced mechanism, these forces and moments are transmitted to the frame which worsen the dynamic performance of vehicle engine and generate vibrations, wear and noise. It leads to expensive repairs and replacement of crankshaft and connecting rod and their reverse effects on the other parts such as cylinder block and piston.Few review papers discuss the methods to reduce the shaking force and shaking moment based on different approaches [2-4]. To achieve full force balance in the mechanism, the total mass center of moving links is made stationary either by adding counterweights [5] or by mass redistribution [6, 7].

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