Experimental validation of a constant-force mechanism and analysis of its performance with a calibrated multibody model

Abstract

The potential applications of constant-force mechanisms (CFMs) have increased in recent years with the development of new designs. This paper focuses on the experimental evaluation and the mathematical modelling of a CFM. The mechanism is based on the use of cams, rollers and springs, which allows for a large stroke and user-adjustable force value. The evaluation and validation of the mechanism is carried out by performing a series of tests examining the constancy of the input force, and where the influence of friction forces and the manufacturing process on the performance of the mechanism is revealed. A multibody model of the constant- force mechanism is developed and calibrated with the help of the experimental results. This model is based on the assumption of rolling without sliding between the cam and the roller, what makes the multibody model to include velocity constraints. The calibration of the model pursues the development of a mathematical tool to study the performance of the mechanism in conditions that are different from those of the experiments presented. The CFM model is used to perform a sensitivity analysis of some important design parameters of the mechanis