GB2319969A

GB2319969A - Golf swing measurement

Info

Publication number: GB2319969A
Application number: GB9625369A
Authority: GB
Inventors: Dennis Ian Robertson
Original assignee: Individual
Current assignee: Individual
Priority date: 1996-12-06
Filing date: 1996-12-06
Publication date: 1998-06-10
Also published as: GB9625369D0

Abstract

The path of a golfer's swing is plotted by recording the position of the club at short intervals of time, the positions are then stored in a memory and the storage array is used to derive numerical values of speed and forces acting on the club during the swing.

Description

GOLF DYNAMICS This invention relates to the dynamics that operate in the plane of a golf swing.

Golfer's usually wish to improve their game and often pay for guidance from professionals, books and journals. At present, such guidance is overwhelmingly non-numerical. This patent describes an invention whereby the linear and rotational forces that the golfer applies in the plane of the swing to his club can be calculated at short intervals of time throughout the swing. For a fee, numerical results are provided to the golfer in the form of graphs, histograms and tables that provide a detailed quantitative record of his/her swing. Golfers can learn from the record by following written explanations and by making comparisons with other golfers, of a range of abilities, from whom similar records can be made available.

According to the present invention, there is provided a means of recording the positions of a golf club (and, optionally, points located on the golfer) at short intervals of time throughout the plane of a swing by the golfer. The co-ordinates of these data are then stored in arrays and procedures employed to derive numerical values of the golf club's position, velocity and acceleration. The standard equations of motion of a moving body are then applied, with other mathematical procedures, for each interval of the swing, to estimate the linear and rotational forces in the plane of the swing which the golfer must be applying to the golf club. Further procedures are employed to present the information in forms that can be of value to golfers.

A specific embodiment of the invention will now be described by way of example: A video camera recorder (camcorder) was used to capture a moving image of the swing of a golfer. The camcorder shutter speed was set at 1/2000 of a second to minimise blur in the image.

The camcorder was mounted at right angles to the plane in which the golfer swings the club.

The images from the camcorder were recorded on a VHS tape cassette in a video cassette recorder (VCR). The VCR has a jog shuttle control.

The recorded tape was played through a TV. Transparent acetate overlay was placed across the TV screen and secured by adhesive tape.

The jog shuttle control on the VCR was used to step the frames from the recorded tape forward or backward as necessary to select individual frames from the start to the end of the swing. The positions in each frame of the head of the golf club and of the bottom of the grip, were recorded by marking points on the acetate.

After a full set of points of golf club positions was collected, the acetate was removed and laid on graph paper. All the points recorded on the acetate were translated into XY co ordinates and the data entered into a computer spreadsheet.

The time between pairs of points was known from the frame rate of the camcorder, enabling the velocities and accelerations of the club head and grip to be calculated in the spreadsheet.

Formula were derived for the purpose, based on co-ordinate transformations, geometrical relationships and similar mathematical tools.

The set of equations that apply to moving bodies were then used to estimate the linear and rotational forces which the golfer must be applying to the club - account is taken in these calculations of gravity and wind resistance. The weights of the head of the club, the shaft and the grip were measured to provide the values of mass used in these calculations.

The final step was to calculate and print out, from the spreadsheet, graphical displays of the club positions (head and hands) corresponding to the recorded frame positions. In addition, graphs of speeds and forces acting on the club head were produced.

Fig 1. shows an example of the information which was recorded from one swing - pairs of points represent the position of the head and grip of the club at successive short known intervals of time. These are the main data on which the key step of deriving forces is based.

The types of equipments used in the invention, as described in the above embodiment, could take different forms: The equipment used to capture images of the swings of golfers need not be a camcorder - any equipment that can record a succession of sharp images at known short intervals of time could be suitable. Conventional cameras using photographic emulsions could be suitable, with the use of a strobe light. Digital cameras may also have the required performance.

It is not necessary that the equipment used to capture the image need store it. For example, the images might be transferred directly into a computer, for subsequent analysis.

The manual transcription of data points could be replaced by use of an image tracking system that follows automatically the movement of the club from frame to frame and records appropriate co-ordinates for subsequent analysis.

Any pair of data points could be used that allow the positions of the club to be calculated at known intervals of time. Additional data points could be used to gain extra information (e.g. to record the positions of the golfer's head and/or hip).

The device used to record club positions need not be located perpendicular to the swing plane, provided corrections are applied to allow for apparent changes in the XY co ordinates.

Systems of co-ordinates other than XY could be used (e.g. radial).

The calculations of the moving body could be carried out by most types of spreadsheets, by special programming or other such methods. However, the laws that govern the motion of moving bodies must be used to derive forces.

The time intervals between records of the clubs position need not be regular but must be of known value.

Claims

1. The invention is to record numerical data which define the positions of a golf club at short intervals of time throughout the plane of one golf swing and then to perform calculations, using the standard equations that govern moving bodies, so that estimates can be made of the forces applied by the golfer to the golf club.

2. The invention in Claim 1 may be implemented by various equipments. The records of the positions of the golf club during the swing may be made by digital or analogue methods or on photographic film. Similarly, the calculations of velocities and accelerations could be made using manual methods, a computer spreadsheet or by writing a special computer program. The essential feature of the invention is the estimation of forces acting throughout the plane of the swing.