Low Jerk Cam Lift Curve

Abstract

In Chap. 2 the derivation and integration of a simple acceleration curve, was described with the warning that it should not be used in practice. This chapter gives a smoother but analytically more complex acceleration curve, which gives the designer considerable flexibility. The four parts in the previous example has been expanded to fourteen. These parts are alternately straight lines and fifth order polynomials. The straight lines define the slope and the coordinates at the end of each part, and the first derivative of the slope is zero at the ends of the polynomial parts. Each part or interval is integrated twice to obtain the velocity and lift . Again on the nose of the cam the valve lift is known as it is specified by the designer and the velocity is zero. This again permits the solution of two equations in two unknowns. The other side of the cam is designed separately and then mirrored. To ensure a smooth transition on the nose the negative acceleration on the nose is also specified by the designer. This chapter is very repetitive in a sense, and the algebra is protracted and may be hard to follow in places. Although this acceleration curve may seem to be unnecessarily complex, in the writer’s experience this sort of curve is needed to produce a good design.