Computer Simulation of Cam System Dynamics and Sensitivity Studies

Abstract

<p>This thesis deals with the dynamics of can systems, and stems from the need to integrate the dynamic design with the quality of manufacture of the cam profile. The objective is to provide a better insight into the high-speed dynamic performance of the system, and generate more refined qualitative and quantitative information for the dynamic design and the manufacturing of cams. A simulation approach has been used, and a stochastic model has been proposed for the generation of the input signal, which comprises the desired life and the life error due to manufacturing errors in the cam profile. The stochastic model employs the techniques of random number generation and spline smoothing. The input signal is integrated with the seven degrees-of-freedom dynamic model considered for the common cam-follower system.</p> <p>A comprehensive study of the popular cam motions has been conducted to investigate their high-speed performance. In particular, the effects of cam profile manufacturing errors on the dynamic behaviour of the cam-follower system are examined. Sensitivity studies have been performed to investigate the effects of critical system parameters on the system behavior. The study has demonstrated that for semi-rigid follower cam systems, the combined effects of system flexibility and cam profile errors are significantly greater than that of flexibility alone, and that the effects of profile errors are dominating. The dynamic response is critically dependent on the waviness of the life error. It has been established that at high speeds, it is not the vibrational response, but the jump behaviour which determines the dynamic performance. The Modified-Sine, Simple Harmonic, and 3-4-5 Polynomial motions have been shown to exhibit superior high-speed performance to that of the popular Cycloidal and Modified-Trapezoidal motions. It has also been demonstrated that, for the flexible follower system, the dynamic effects of cam profile errors are small. This is probably the reason why previous investigators have neglected the affects of cam profile errors in their modelling. This thesis makes a significant contribution in the field of design of cam-follower systems and the manufacture of cams. A versatile, user-oriented software system - COSCAD has been developed which can be a very useful tool for the cam designer to search for the best cam motion, the system parameters, and the production quality of cams to achieve optimum dynamic performance. Using this program, the system behaviour can be predicted during the design development stage without setting up a complex experimental rig.</p>