A novel method for the dynamic synthesis of cam mechanisms with an imposed driving force profile

Abstract

In the car industry, the ergonomic and haptic properties of controls are gaining high priority. The cam mechanisms of switches and knobs, such as those of car turn switches, are usually required to comply with a certain user force profile, according to human physical limitations and ergonomic requirements. In order to fine-tune the force input and the function performed by the mechanism, the cam profile is normally subjected to a detailed synthesis having as input the desired user force profile. Nevertheless, conventional cam synthesis and analysis methods do not provide an adequate tool for designing the cam profile based on the required driving effort. In this article, an energy-based method is proposed for designing a cam mechanism able to accurately replicate the desired profile of the driving effort. According to the proposed method, the cam profile is determined as a finite series of points and takes into consideration all contact forces between the cam and the follower, including friction. The method is non-linear, considering a combined Stribeck—Therfall friction model as well as the damping of the system. Numerical validation is provided considering the case of the cam mechanism of a conventional car turn switch.