A system for predicting the impact between a ball and a sports surface

An impact hammer was designed that incorporated an accelerometer to measure impact response and set of light-gates to measure impact velocity. This system was capable of consistent drop tests that provided the necessary data to characterise a range of normal impacts. A parametric study was carried out to assess the effect of variables including mass, contact velocity and impact hammer shape. The contact kinetic energy was found to be the control parameter in the loading phase of contact and allowed predictions of maximum force and displacement, independent of mass. The impact mass was found to be the control parameter for the unloading phase of contact, allowing predictions of the damping behaviour of the surface. Mass-spring-damper modelling was carried out for two different sports surfaces, an acrylic tennis court and an athletics track. To validate the model, normal impacts were carried out between a rigid ball and the athletics track, monitored using a high speed video camera. The model successfully predicted the coefficient of restitution and displacements for a range of impacts.