The focus of this paper is the development and modelling of a reverse-poppet valve train assembly, placing a major emphasis on the optimization routine used to develop a short-duration camshaft profile. A user-programmable script, known as the penalty function, was written to assign weighted numeric values to certain parameters associated with the valve lift profile and its derivatives. These design parameters include maximum acceleration, peak lift, area under the lift curve and minimization of jerk. Optimization tools built into Matlab were then used to generate a profile which minimizes the overall ‘penalty’ associated with each parameter as it deviates from a user-defined ideal.
A commercially available multi-body dynamics software package was used to evaluate the dynamic performance of the valve train incorporating the generated cam profile. A flexible-body spring element provided insight into spring surge and coil contact. Comparisons of the designed and simulated lift, velocity and acceleration profiles are given.
