Robert Cottey's scientific contributions

An analysis of the vibration characteristics of a tennis racket system; frame, string-bed plus damper has been conducted. The influence of how the frequency spectrum is altered by the application of string dampers was investigated. Several experimental setups were used to determine how the vibration profile changed by varying the positioning and weight of the string damper. The vibration characteristics of the string-bed were initially evaluated by comparing vibration responses between frame-excited to string-excited frequency responses. Results show the effect that different damper configurations have on the amplitude and frequency of the vibration modes. The results indicate that string dampers must be tuned to provide optimised damping conditions for individual tennis racket configurations. In conclusion, this work has demonstrated that the damper has effects on the frequency response that go beyond a simple noise reduction or as an aesthetically pleasing addition to the racket. KeywordsString damper-string-bed-racket-vibration

We succeeded in obtaining PSP (Pressure-Sensitive Paint) measurements for a rugby ball. It was found that the seam of the ball is the trigger for initiating low pressure. Therefore, a slower spinning ball fluctuates during flight because of the asymmetrical pressure distribution on the sides of the ball. Based on the results from PSP measurements, multi-objective optimization of the fluctuating punted kick was carried out, and then the trade-offs between the objective functions and the control variables could be visualized using Self-Organizing Maps. It was found that the higher the spin rate at launch the greater the number of fluctuations; however, the hang time becomes shorter.

The aim of this research was to determine what effect an active damping tennis racket technology had on players suffering with symptoms of tennis elbow. The study was conducted to verify findings of previous research, which concluded that the symptoms of tennis elbow had been dramatically reduced by playing with a Head rackets containing the Head Chip system™ (Kotze et al. 2003). A similar study over an extended period was completed to further substantiate these findings and to test the improved generation of ‘Chip’ rackets. This study used two versions of the Head Protector Oversize tennis rackets; both containing piezo ceramic fibres integrated with the electronic Chip system™, but only half with the chip “active”, thus providing a control. The subjects were male and female experienced tennis players diagnosed with either acute or chronic tennis elbow. They were given unspecified rackets to facilitate a blind study, and the subjects’ elbow condition was medically assessed and recorded over an extended period of time. Results of the study indicated that for the players who were initially diagnosed with acute tennis elbow, a large improvement in their condition was recorded for those using the active rackets, whilst the players with the control rackets showed little improvement in their condition. Similar results were found for the players diagnosed with chronic tennis elbow although to a lesser extent; those using rackets with active chips showed an overall improvement, whilst the players with the control rackets again showed little sign of improvement. The results of the study have shown that an active damping technology, when applied to a tennis racket, can reduce the symptoms of both acute and chronic tennis elbow.