TENTH INTERNATIONAL CONGRESS ON SOUND AND VIBRATION , ICSV 10 DESIGN AND ANALYSIS OF A PARALLEL MECHANISM FOR THE GOLF INDUSTRY
Previous work done in the study of golf club dynamics professes dissatisfaction with robotic testing used to evaluate and compare golf equipment. The main complaint is that the club dynamics measured during a robot swing do not correlate with the same data in a human swing. This paper presents the design and analysis of an alternative to the current robotic testing systems. The viability of a parallel kinematic (two-arm) concept as a robotic testing machine for golf clubs and balls is demonstrated. Human biometric data was used as the basis for determining link geometry as well as motion planning for the swing. Models, simulations, and correlations with human test data were used for validating the design. A demonstration prototype was built to show the interactions and motions of the various components.
The dynamics of a golf club
Generating the appropriate model of a dynamic system is strongly dependent on the boundary conditions assumed for the model. In the case of golf clubs, conventional wisdom has been to assume a clamped boundary condition at the grip, the rational being that the hands hold the club firmly. This research presents evidence that suggests a more appropriate boundary condition for the modeling of golf clubs would be a free condition or a pinned boundary appropriately located on the grip. Experimental modal results and finite element results are presented to support these conclusions. A steel shafted club and a graphite shafted club were tested.
Joint center longitudinal positions computed from a selected subset of Chandler's data
Mathematical models of the human body are indispensable tools for studying the biomechanics of human movement. The geometrical centers of the 12 main joints (shoulders, elbows, wrists, hips, knees ankles), modeled as simple mechanical joints, are widely used as reference points for building mathematical models of the human body. These reference points, typically defined as "joint centers", are assumed to maintain a fixed 3D position relative to both the segments forming the joint, throughout the range of joint motion. No single point in a human joint perfectly meets this assumption, and no simple method is available for locating the points that are closest to meet it. Researchers often have recourse to subjective methods, based on their knowledge of anatomy. Objective estimates are easily attainable if the positions of a few bony landmarks can be measured on the subject, and the longitudinal distances of the joint centers from these landmarks are known. A subset of the anthropometric measurements performed by Chandler et al. (NTIS No. AD 710-622, 1975) on six cadavers was critically selected and utilized to compute the percent longitudinal distances of the 12 main joint centers from neighboring bony landmarks, relative to the lengths of the respective proximal and/or distal segments. Three-dimensional positions are attainable as well, by assuming joint centers lay on the respective segment longitudinal axes. The use of a method for accurately locating joint centers is recommended, particularly when they are used as reference points for defining a personalized geometrical model of a subject's body.