April 2020

54 n MACHINE VISION April 2020 www.drivesncontrols.com Cameras help golfers to choose the best clubs A German manufacturer of customised golf clubs has found a novel use for machine vision cameras: analysing golfers’swings to determine the most appropriate clubs for them. Classic Club Repair, based near Nuremberg, is using the cameras to evaluate ball flights and thus to produce a set of clubs that are ideally matched to the player’s swing. Swinging a golf club might appear easy. However, it requires a high level of precision, physical control and coordination and is among the most technically challenging motion sequences in sport. A ball lying just above the ground has to be hit accurately with a club head measuring just 10 x 5cm. The golfer must hit the ball with the face of the club at precisely the right angle, while taking into account factors such as the ground conditions, distances, wind strength and gradients. Selecting the right club is crucial to the perfect golf swing and ideally it should be tailored to the player’s individual measurements and requirements. If, for example, the club is too long, it becomes difficult to control. If it is too short, the player has to stoop, and achieving the correct shoulder turn from such a stance is challenging. Clubs sold in golf stores tend to come in standard sizes. These may suit players who match the standard measurements, but most people don't fit the norm and could benefit from custom-made clubs. This is where the camera-based fitting service comes into play. The first step is for Classic Club Repair’s owner, Dietmar Erhardt, to measure his customers. The ideal club length is determined by a combination of factors including body height, and distance from hand to floor. Erhardt analyses his customer’s body movements using a MotionBlitz EoSens mini1 high-speed camera fromMikrotron. On average, a golf stroke is executed in just 0.8–1.5 seconds. When wielded by an experienced player, the club head can reach speeds of up to 200km/h. At these speeds, details of the swing cannot be picked up by the naked eye. The camera provides Erhardt with detailed slow-motion recordings. He also uses Doppler radar systems to determine parameters such as departure angles, spin rates, club head and ball speeds, flight lengths, landing angles and pitch lengths. The player receives a video analysing their swing, and two weeks later their customised clubs are ready. Among other things, the recordings help to choose the best shaft material. For example, the faster the club head moves, the more the shaft is likely to bend out of shape. For players with a fast, powerful swing, a less flexible shaft is therefore better. This gives them increased control over the stroke. For older players or beginners with a slower, weaker swing, a shaft made from a more supple material is preferable. With a shaft made from graphite, for example, the weight shifts to the club head and the total weight is reduced, improving acceleration. Over the past 30 years, Classic Club Repair has measured more than 20,000 golfers and customised clubs for them. As well as performing the tests in his shop, Erhardt also has a mobile fitting lab, complete with the high-speed cameras, that he takes to golf clubs and sporting events. n A German company is using machine vision cameras to analyse golfers in action and thus to design customised golf clubs tailored to their particular characteristics and style. Dietmar Erhardt analyses frames from slow-motion machine vision video recordings to determine the best golf club for each golfer