APPARATUS AND METHOD FOR MEASURING PEDALLING EFFICIENCY

Abstract: An apparatus for measuring the pedalling efficiency of a cyclist comprises a frame (2) having a set of rotatable pedals (6) attached thereto and at least one strain transducer (18) attached to said frame. An indicator means (21) is connected to said strain transducer (18) and is arranged to provide an indication of the cyclist's pedalling efficiency, said efficiency being dependent on the strain sensed in the frame.

Description: APPARATUS AND METHOD FOR MEASURING PEDALLING EFFICIENCY The present invention relates to an apparatus for, and a method of, measuring the pedalling efficiency of a cyclist. In particular, although not exclusively, the invention relates to a training aid for cyclists. A cyclist's pedalling technique is very important for efficient cycling, and in particular for speed and endurance. Even a very small improvement in the energy efficiency of a cyclist's action may make the difference between winning and losing, particularly at higher levels of competition. It has been observed that accomplished cyclists generally have a very smooth pedalling technique whereas the action of less proficient cyclists may be jerky and uncoordinated. It is generally believed that a smooth action is indicative of energy efficiency and cycling coaches have therefore tried to encourage such an action. US Patent No. 5,202,627 discloses a device for indicating the smoothness of a cyclist's pedalling technique. The device operates by measuring the instantaneous angular velocity of the pedals as they rotate, and displaying the results graphically on a screen. Because changes in the pedal velocity are related to variations in the pedalling force applied by the rider, the smoothness of a cyclist's pedalling technique can be assessed. The device does not, however, provide a direct indication of how energy efficient the cyclist's action is. It is an object of the present invention to provide a method of, and an apparatus for, measuring the energy efficiency of a cyclist's pedalling action. According to the present invention there is provided an apparatus for measuring the pedalling efficiency of a cyclist, the apparatus comprising a frame having a set of rotatable pedals attached thereto, at least one strain transducer attached to said frame and arranged to sense the strain generated in the frame during use , and an indicator means connected to said strain transducer and arranged to provide an indication of the cyclist's pedalling efficiency, said indication of efficiency being dependent on the strain sensed in the frame. The energy associated with a particular cycling action is dissipated two ways: the majority of the energy is transferred to the rear wheel of the bicycle causing forwards motion, and a small amount of energy is passed into the bicycle frame as strain energy and eventually dissipated in the form of heat. The present invention provides a method of measuring the energy efficiency of the cycling action by monitoring the amount of strain energy passed into the bicycle frame. This allows a cyclist to modify his or her cycling style for maximum efficiency. The pedalling efficiency of the cyclist may be determined from variations in the strain sensed in the frame. The indicated pedalling efficiency may be inversely dependent upon, and is preferably inversely proportional to, the peak-to-peak range of the strain measurements. The invention allows a cyclist to determine the smoothness of his or her pedalling technique. By monitoring the strain in the cycle frame it is possible to determine the direction of the forces applied to the pedals and the magnitudes of those forces. Ideally, the forces should be tangential to the circular path of the pedals and should not vary significantly in magnitude. The apparatus may include a processor means connected to said strain transducer and arranged to analyse the strain signals. Preferably, the processor means comprises a computer. Advantageously, the apparatus comprises a plurality of strain transducers arranged to sense the strain in different parts of the frame. The indicator means may include a visual indicator device and/or an audible indicator device. The apparatus may include means for measuring the pedalling speed, for example by measuring the angular velocity of the pedals. The indicator means may be arranged to indicate the uniformity of pedalling speed. The apparatus may include means for varying the resistance to pedalling. According to the present invention there is further provided a method of measuring the pedalling efficiency of a cyclist, the method comprising providing an apparatus including a frame having a set of rotatable pedals and at least one strain transducer attached thereto, sensing the strain generated in the frame during pedalling, determining from the strain sensed in the frame the pedalling efficiency of the cyclist and providing an indication of the pedalling efficiency. The strain generated in the frame may be sensed in a plurality of different parts of the frame. The pedalling efficiency may be indicated visually and/or aurally. Advantageously, the method further comprises measuring the pedalling speed and providing an indication of pedalling efficiency that is dependent also on the measured pedalling speed. The pedalling speed may be measured by sensing the angular velocity of the pedals. An indication of the uniformity of pedalling speed may be provided. The method may further comprise varying the resistance to pedalling during use. Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, of which: FIGURE 1 is a schematic side view of a bicycle adapted for measuring the pedalling efficiency of a cyclist; FIGURE 2 is a diagram illustrating the forces applied to a pedal of a bicycle; FIGURE 3 is a graph showing the predicted strain for two different cycling styles; and FIGURE 4 is a graph showing the output of the strain gauges, showing the test results for two different cycling styles. Figure 1 shows a conventional racing cycle 1 comprising a f ame 2 , front and rear wheels 3 , 4 , a pair of pedal cranks 5 and pedals 6 , a chain 7 , front and rear sprockets 8 , 9 , handle bars 10 and a saddle 11. The frame 2 consists of a crossbar 12, a down tube 13, a seat tube 14, and a pair of rear wheel forks, each consisting of a seat stay 15 and a chain stay 16. For the purpose of measuring the cyclist's energy efficiency, the bicycle 1 may be placed on a set of rollers 17a, 17b, 17c. Alternatively, all the components of the measuring apparatus may be mounted on the bicycle, so that the efficiency of the cyclist may be measured whilst the cyclist is cycling along a road or track. The measuring apparatus may also be mounted on a static cycling machine so that the efficiency of the cyclist can be measured under controlled conditions, for example in a laboratory or gymnasium. In that case, the frame 2 may take any suitable form and need not resemble a conventional bicycle frame. Mounted at various locations on the frame 2 are a set of strain transducers 18a, 18b, 18c. These transducers may be of any suitable type, for example of resistant or piezo type. Each strain transducer device 18a, 18b, 18c is connected to a strain-gauge bridge (not shown) , which converts the small amounts of distortion in the frame 2 during use into a millivolt electrical signal. These signals are carried on wires 19a, 19b, 19c to a processor device, for example a computer 20. The computer 20 is in turn connected to an indicator device 21, which may be a visual display device, for example a VDU screen, an LED display or a printer, or an audible signalling device, such as a piezoelectric sounder. The apparatus may also include means for measuring the speed of the cycle and the torque applied to the rear wheel. This may, for example, consists of a speed and force transducer 22 attached to one of the rollers 17c and connected to the computer 20 by a lead 23. Any number of strain transducers may be provided although, for some purposes, one may be sufficient. The transducers may also be located at various different positions on the frame 2. For a conventional cycle frame, however, the optimum positions include the chain stay 16, the down tube 13 and the seat tube 14. If it is desired to measure the pedalling efficiency of a cyclist whilst he or she is cycling along a road or track, the strain transducers may be connected to a device (not shown) for recording the strain measurements for later analysis. Alternatively, the strain measurements may be transmitted to a remote computer, for example by means of a radio link. It is also possible that a display device may be provided on the cycle, to provide the cyclist with an indication of his or her pedalling efficiency, for example during training. During use, the cyclist mounts the bicycle and the strain generated by the cyclist's action in the cycle frame 2 is measured by the strain transducers 18a, 18b, 18c. The millivolt output signals of the strain gauge bridges are received by the computer 20, which analyses those signals and generates an output signal that is fed to the indicator device 21, to indicate the pedalling efficiency of the cyclist. The efficiency of the cyclist's pedalling action is determined from the strain measurements, a highly efficient action being indicated when the variations in the strain are smallest, this being consistent with the smooth pedalling style. If the rider adopts a less smooth technique, greater variations in strain will be generated in the frame and a lower efficiency will be indicated. The efficiency of the cyclist's pedalling action may be indicated visually, for example by means of coloured lights, or audibly, by variations in the pitch or loudness of an audible signal. The computer 20 provides various signal-processing functions so that the indicator device 21 receives a signal that is proportional to the range of the signal received from the strain transducers. The computer may also perform other functions such as normalising the signal in relation to the average value of the signal received. Figure 2 illustrates diagrammatically the forces applied to a pedal of a bicycle. Modern racing cycles are equipped with special pedals to which the rider's foot can be attached by means of a special binding or fixing. This allows the rider to pull up on the pedals as well as push down. Accomplished riders can produce a smooth turning effect on the pedals by providing a pedal force whose direction is always nearly tangential to the circular path of the pedals. In Figure 2, the general pedal force applied to one of the pedals is indicated by the vector F. The tangential component F t of this pedal force produces a turning movement about the crank centre. The radial component F r does not contribute to the turning movement and only produces stress and strain in the frame. The most efficient pedalling style is one in which the proportion of the total energy expended that enters the bike frame is least. The pedalling efficiency monitor produces an output that is proportional to the amount of energy entering the frame, which allows the rider to monitor the efficiency of his or her pedalling style during a race or training. The rider can determine indirectly from the strain measurements how close he or she is to achieving a perfectly smooth style, i.e. one in which the forces applied to the pedals are always tangential and do not vary significantly in magnitude. Computer analysis of the stresses and strains generated in a typical racing bicycle during use has been carried out by the inventor and the results of the computer simulation are shown in Figure 3. Two pedalling styles were analysed in the computer model: firstly a perfectly smooth style and secondly a non-smooth style that provides the same amount of energy to the pedals. The analysis predicted a range of 15 microstrain for the smooth style and range of 140 microstrain for the non-smooth style. These predictions verify that the strains in a bicycle frame are very sensitive to pedalling style. The results of a test using a prototype version of the pedalling efficiency monitor are shown in Figure 4. This graph shows the strain results (plotted in millivolt bridge output) for a smooth style and a less smooth style overlaid for comparison. The results show distinct differences between the two pedalling styles. Various modifications of the invention are of course possible. For example, the pedalling efficiency monitor may be arranged to detect asymmetry in the cyclist's action: that is, whether one leg is providing more power or energy than the other leg. This would enable a cyclist to identify which leg is the main source of weakness, so that appropriate corrective training can be undertaken. The pedalling efficiency monitor may also be arranged to provide an indication of the power developed by the cyclist. This may be achieved by fitting the pedalling efficiency monitor to a bicycle and calibrating the monitor against a known power output. The cyclist would then be able to monitor his/her power output during training or a race.

Claims: CLAIMS 1. An apparatus for measuring the pedalling efficiency of a cyclist, the apparatus comprising a frame having a set of rotatable pedals attached thereto, at least one strain transducer attached to said frame and arranged to sense the strain generated in the frame during use, and an indicator means connected to said strain transducer and arranged to provide an indication of the cyclist's pedalling efficiency, said indication of efficiency being dependent on the strain sensed in the frame. 2. An apparatus according to claim 1, said apparatus including a processor means connected to said strain transducer and arranged to analyse strain signals received therefrom. 3. An apparatus according to claim 2 , wherein said processor means comprises a computer. 4. An apparatus according to any one of the preceding claims, wherein said apparatus comprises a plurality of strain transducers arranged to sense the strain in different parts of the frame. 5. An apparatus according to ' any one of the preceding claims, wherein said indicator means includes a visual indicator device. 6. An apparatus according to any one of claims 1 to 4 , wherein said indicator means includes an audible indicator device. 7. An apparatus according to any one of the preceding claims , said apparatus including means for measuring the pedalling speed. 8. An apparatus according to claim 7, wherein said means for measuring the pedalling speed comprises means for measuring the instantaneous angular velocity of the pedals. 9. An apparatus according to claim 7 or claim 8, wherein said indicator means is arranged to indicate the uniformity of pedalling speed. 10. An apparatus according to any one of claims 7 to 9 , wherein said indicator means is arranged to indicate the direction of the forces applied to the pedals. 11. An apparatus according to any one of claims 7 to 10, wherein said indicator means is arranged to indicate the magnitude of the forces applied to the pedals. 12. An apparatus according to any one of the preceding claims , said apparatus including means for varying the resistance to pedalling. 13. A method of measuring the pedalling efficiency of a cyclist, the method comprising providing an apparatus comprising a frame having a set of rotatable pedals and at least one strain transducer attached thereto, sensing the strain generated in the frame during pedalling, determining from the strain sensed in the frame the pedalling efficiency of the cyclist and providing an indication of the pedalling efficiency. 14. A method according to claim 13, in which the pedalling efficiency of the cyclist is determined from variations in the strain sensed in the frame. 15. A method according to claim 14, in which the indicated pedalling efficiency is inversely dependent on the range of the strain measurements. 16. A method according to claim 14, in which the indicated pedalling efficiency is inversely proportional to the range of the strain measurements . 17. A method according to any one of claims 13 to 16, in which the strain generated in the frame is sensed in a plurality of different parts of the frame. 18. A method according to any one of claims 13 to 17, in which the pedalling efficiency is indicated visually. 19. A method according to any one of claims 13 to 17, in which the pedalling efficiency is indicated aurally. 20. A method according to any one of claims 13 to 19, said method further comprising measuring the pedalling speed and providing an indication of pedalling efficiency that is dependent also on the measured pedalling speed. 21. A method according to claim 20, in which the pedalling speed is measured by sensing the angular velocity of the pedals. 22. A method according to claim 20 or claim 21, said method further comprising providing an indication of the uniformity of pedalling speed. 23. A method according to any one of claims 20 to 22, said method further comprising providing an indication of the direction of the forces applied to the pedals. 24. A method according to any one of claims 20 to 23, said method further comprising providing an indication of the magnitude of the forces applied to the pedals. 25. A method according to any one of claims 13 to 23, said method further comprising varying the resistance to pedalling during use. 26. An apparatus for measuring the pedalling efficiency of a cyclist, the apparatus being substantially as described herein with reference to, and as illustrated by, the accompanying drawings. 27. A method of measuring the pedalling efficiency of a cyclist, the method being substantially as described herein with reference to, and as illustrated by, the accompanying drawings .

Inventors: JOHNSON ROBERT PHILIP, JOHNSON, ROBERT, PHILIP
Applicants: JOHNSON ROBERT PHILIP, TICKFORD CONSULTANCY LIMITED, JOHNSON, ROBERT, PHILIP
Application year: 1998
Main classification: G01L3
IPC codes: A63B24, A63B69, G01L1