WO2009034317A2

WO2009034317A2 - Improvements relating to exercise bicycles

Info

Publication number: WO2009034317A2
Application number: PCT/GB2008/003066
Authority: WO
Inventors: Michael Joseph Patrick Rice
Original assignee: Trixter Plc
Priority date: 2007-09-10
Filing date: 2008-09-09
Publication date: 2009-03-19
Also published as: GB0717579D0; WO2009034317A3; GB2452569A

Abstract

A crank position sensor assembly for use in combination with an exercise bicycle having at least a frame and a crank that rotates relative to the frame about an axis. The sensor assembly comprises a set of magnetic elements fixed in position relative to the crank for rotation with the crank, and at least two sensing elements that sense the passing of the magnets. Alternatively it may comprise two pairs of light sources and receivers which detect the passing of teeth or spokes. A processor processes the output signals from the first and second sensing elements or receivers, the processor determining both the position of the crank and its direction of rotation from the outputs of the first and second sensing elements. A controller for a microprocessor based unit is also disclosed which causes images to be displayed on screen in response to inputs received from one or more sensors fitted to a stationary exercise bicycle of the kind in which the handlebars are free to tilt from side to side during use, the controller receiving a first signal from a crank position sensor which is indicative of the position of the crank of the bicycle within a single rotation and a second signal from a handlebar position sensor indicative of the angle of tilt of the handlebar. The controller produces an output signal whose value depends on the co-ordination of rotation of the crank with the tilt of the handlebars that is produced as the rider pedals whilst pulling on the handlebars.

Description

IMPROVEMENTS RELATING TO EXERCISE BICYCLES

FIELD OF THE INVENTION

This invention relates to improvements in exercise bicycles, which includes ordinary bicycles converted to function as stationary exercise bicycles. It more specifically relates to sensors for use with exercise bicycles. It also relates to a combination of an exercise bicycle, a microprocessor based unit and a display that forms an integrated exercise system.

BACKGROUND TO THE INVENTION

Keeping fit and active is becoming an increasingly important part of people's lifestyles. Some of the best forms of exercise for keeping fit include cycling, running and rowing as they make the exerciser work aerobically. This both works the major muscle groups and also strengthens the heart and lungs. The result is an increased level of physical well-being.

With increasing demands being placed on people's lives due to work and the family, it is often difficult to find the time to exercise regularly. Also, for much of the year in many countries it may be necessary to exercise in the dark outside of working hours. This can be unpleasant and dangerous.

Current medical reports state that the rapid rise, in childhood obesity has been mirrored by an explosion of sedentary leisure pursuits for children such as computers, video games, and television watching. Reports also indicate that increased general activity and play rather than competitive sport and structured exercise seem to be more effective. Parents, however, tend to be content with their children staying in the home playing computer games rather than being worried about their safety if playing outdoors.

As well as the pressures of work and family for adults the above points are as applicable to adults as to children. The level of fitness in the general population in today's Western world is far removed from that of our ancestors. One of the best healthy habits is a regular exercise programme.

To meet the demand for increased exercise in an insecure, busy and often unscheduled lifestyle, a wide range of exercise apparatus has been developed. The most popular of these are the exercise bicycle, the treadmill and the rowing machine. These apparatus allow the user to perform the same range of movements as they would in the corresponding sport but in the warmth, safety and comfort of their home or gymnasium.

In another arrangement, devices can be purchased that convert all forms of road bicycles (racing bikes, tourers, hybrids and mountain bikes and the like) into an exercise bicycle by arranging for the rear wheel to drive a load against a resisting force such as a turbine or magnetic brake whilst the bicycle is held stationary on a support.

For maximum benefit in the shortest space of time it is recommended that regular exercise consisting of twenty to thirty minutes at least three times very week is undertaken. As anyone who has regularly used an exercise bicycle or the like will know, these blocks of twenty minutes can be extremely tedious. Removing the interest provided by passing varied terrain in varied weather outdoors the act of cycling or rowing is quite repetitive and boring. As a direct consequence of this monotonous exercise it is therefore often difficult to maintain the required degree of motivation needed to complete regular exercise using the devices. This is especially the case amongst the younger age groups where modern alternative pastimes such as computer gaming are now more popular.

It is well known to provide a stationary bicycle upon which a person can pedal to simulate riding a bicycle. The rider sits on the bicycle, which is fixed in position and turns the pedals of the bicycle against a resistive load. The stationary bicycle needs at least a saddle, a handlebar and a bottom bracket which must be held in the correct spaced location. The support for these components usually comprises a metal frame with floor standing feet which supports the saddle upon which the user sits at a convenient height. The frame also supports the bottom bracket below the saddle, and a crank with pedals which are operated by the user's feet. The handlebar is supported in front of the saddle. To fit different people the positions of the saddle and the handlebar relative to one another and relative to the bottom bracket may be adjustable, but are usually set up so that the handlebar and the saddle are the same height above the floor as the handlebars and saddle of a normal bicycle.

The present invention is applicable to all forms of exercise cycle, including specific exercise bicycles as well as converted road or mountain bicycles used with a turbotrainer or the like. It is known to provide a set of moving handlebars to an exercise to provide upper body training and to mimic the movement of the bars of a bicycle as the rider is standing up on the pedals. It is also known from that document to provide for different input devices which pass input signals to a microprocessor in turn to control the operation of a game displayed on a display screen. Basic sensors disclosed in that document include a handlebar position sensor, a wheel sensor, a reed switch that detects the a passing of a magnet fitted to the pedals that acts as a crank position sensor and a seat pressure sensor that indicates whether the rider is seated or standing.

It has been appreciated that a further range of enhanced sensors for use in combination with a microprocessor based game or training program would be desirable.

OBJECT QF THE INVENTION

According to a first aspect the invention provides a crank position sensor assembly for use in combination with an exercise bicycle having at least a frame and a crank that rotates relative to the frame about an axis, the sensor assembly comprising: a set of magnetic elements fixed in position relative to the crank for rotation with the crank, the magnetic elements being located at spaced positions around the axis of rotation of the crank; a first sensing element which is fixed relative to the frame of the bicycle in a position whereby rotation of the crank causes each of the magnets to move past the first sensing element in turn, each sensing element producing an output signal when a magnetic element is aligned with the sensing element; a second, index, magnetic element supported in a fixed position relative to the crank and which rotates with the crank, a second sensing element which is fixed relative to the frame of the bicycle in a position whereby rotation of the crank causes the second magnetic element to move past the second sensing element once per revolution of the crank, the second sensing element producing an output signal when the second magnetic element is aligned with the second sensing element and a processor which processes the or each output signal from the first sensing elements to produce an angular position signal indicative of the position of the crank, and in which the processor uses the output of the second sensing element to provide a datum point for the angular position signal, resetting the angular position signal if the postion indicated by that signal and the position indicated by the datum become misaligned.

The processor may provide an output signal which comprises a count, the count being incremented each time the first sensing element produces an output signal. This count will therefore increase as the crank is rotated. Assuming that the crank is always rotated in the same direction, as is usual when cycling, this count will indicate the angular position. The output of the second sensing element may be used to reset the count. This ensures that any inaccuracy is removed on each revolution. For example, if the crank rotated backwards slightly at some point before going on to complete a revolution the count may be corrupted. This reset datum corrects this corruption whenever the crank passes the datum position.

The sensing elements may comprise reed switches or Hall Effect sensors.

Preferably there are 3 or more magnetic elements, or multiples of 3 magnetic elements. They may be located at equally spaced circumferential locations around the crank.

The magnetic elements may be supported by a support element. The support element may comprise a disk located between the inner face of the crank and the frame. It may comprise a non ferrous material. For instance it may comprise a disk of plastic material.

Preferably, a pair of first sensing elements are provided which are located at spaced positions relative to the frame, both of which respond to movement of the first magnetic elements. As will be described later this can enable the direction of rotation of the crank to be determined by the processor. As well as giving crank rotation direction, it also enables the count (where used) to accurately count up and also down.

The second magnetic element may be combined with one of the first magnetic sensing elements as a single sensing element. This may, for instance, generate a stronger magnetic field or a different shaped magnetic field to the other first magnetic elements so that only this element causes the output of the second sensing element to change.

Whilst the invention has been described in terms of magnets that rotate past magnetic field sensors, the invention can be implemented without the use of magnets. The magnets can be thought of as modulating elements, their presence close to a sensor causing it to provide a first output and when moved away from the sensor causing to provide a different, second, output. The magnets could be replaced with teeth that pass across a light sensitive detector to alter the amount of light falling on the detector. Alternatively they may comprise metal teeth that distort a magnetic field as they pass between a magnet and a magnetic field sensor, such as a Hall Effect sensor. They may even comprise parts of a single track of resistive material which extends around a circumference of the crank and which is swept by a contact such that the overall resistance measured between the contact and one end of the track varies with crank position in the manner of a potentiometer. This is not preferred, however, as it relies on contact between moving parts which leads to wear and resistance to movement of the cranks.

Thus in an alternative, according to a second aspect the invention provides a crank position sensor assembly for use in combination with an exercise bicycle having at least a frame and a crank that rotates relative to the frame about an axis, the sensor assembly comprising: a modulating element fixed relative to a crank of the bicycle so that it rotates with the crank about its axis of rotation, the element carrying a track of modulating teeth or spokes and also an index spoke or tooth that is located at a predetermined position relative to the crank, a first transmitter means which transmits radiation which is located at one end of a transmission path, and a receiver means which is located at the other end of the transmission path and which produces, as the crank rotates, at least one first output signal that varies according to the amount of radiation emitted by the transmitter that is incident upon it as modulated by the track of teeth or spokes and a second output signal that varies accordning to the amount of radiation emitted by the transmitter that is incident upon it as modulated by the index spoke or tooth, both the transmitter means and receiver means being fixed relative to the frame of the bicycle, and a processor which processes the first and second output signals from the receiver means and determines the position of the crank therefrom.

The receiver means may comprise a first and a second receiver.

The transmitter means may comprise a single radiation source or two radiation sources, and the receiver means may comprise two receivers, one detecting the presence of the index spoke or region and the other the location of the modulating element.

An additional receiver which also determines the location of the modulating element may be provided to form first and second transmitter/receiver pairs connected by respectively first and second transmission paths. Light along each path may be modulated differently by the modulating element as the crank is rotated, the processor determining both the position of the crank and its direction of rotation from the outputs of the two receivers.

The first element may comprise a spoked wheel arranged concentrically with the axis of rotation of the crank, the wheel having a plurality of opaque spokes separated by transmissive regions between the spokes, whereby as the crank rotates the spokes and transmissive regions alternately pass through the transmission path. By opaque and transmissive we use the terms in a relative sense- the opaque regions do not need to be totally opaque nor the transmissive regions totally transmissive. They just need to transmit light by different amounts so that the light incident on the detectors is noticeably modulated.

The transmitters and detectors may be located such that when a spoke is present in a transmission path no radiation reaches the respective detector and when a transmissive region is present radiation is free to pass to the respective detector associated with that path. This is a so called transmissive device. Alternately, the transmitted light may be reflected from a spoke to the detector and may miss the detector when it passes through a transmissive region.

The transmissive regions between spokes can comprise a circumferential track of slots or other shaped openings in a disk that forms the modulating element. For instance a series of holes or arcuate slots cut around a circular path may be provided. They may even comprise outwardly extending teeth provided around the perimeter of a disk for engagement with the drive chain of a bicycle. Indeed, many different variations are possible within the scope of the invention. The processing means may include a counter which may be set to a known start value when the crank is in a known position. For instance, it may be set to zero when one of the crank arms is at top dead centre.

The processing means may increment the counter each time a transition in the output of one of the receivers/sensing elements occurs. It may increment only when one type of transition occurs, e.g. from low to high, or high to low. As each spoke passes there will be two transitions- high to low and then low to high, which correspond to the edges of a spoke moving across the detector. The spacing between each depends on the angular widths of the spokes and transmissive regions or the number of magnets .

Alternatively, the processor may increment the counter after a sequence of transitions of one or both of the receivers has occurred either from high to low or vice versa.

From a prior knowledge of the angular spacing of the magnets or receivers (or more correctly the angular spacing of the region of the transmission paths that pass through/reflect from the sensing element) the angular position of the crank relative to its start position can be determined from the value of the count.

In a most preferred arrangement the relative angular spacing of the transmission paths and the width of the spokes/transmissive regions should be chosen such that the pattern of change of the output of both the light sensors enables the direction of rotation of the crank to be unambiguously determined by the processing unit. For example, it has been found that an unambiguous output can be obtained using the following formula: Spacing between detectors > d-D and < d,

where d is the spacing between the detectors and D is the angular width of a spoke or a transmission region (i.e. the spacing between edges of a spoke or a transmission region) . This technique should also work with the first aspect of the invention that uses magnetic elements by providing the correct location of the magnets and the sensors. The edge of the magnetic field from each magnet will be equivalent to the edge of the teeth or slots in an optical arrangement. Of course, by edge of the field we mean the point at which the magnetic field strength changes between levels which cause a transition in the sensing element output.

In this case, when a transition of the signal from one detector occurs, the value of the output of the other detector at that time will provide an indication of the direction of rotation of the crank. The processor may therefore employ simple logic to compare the states of the detector outputs immediately after a transition to determine the direction of rotation.

The processing means may include a timer, and may be adapted to start the timer when a transition in one or both output signals occurs and stop it when the next transition occurs. From this the speed of rotation of the crank can be determined by the processing means. The shorter the elapsed time between transitions, the faster the rotation speed.

The transmitter may comprise a light source, either of visible or infrared light or both. The first and second light sources may comprise light- emitting diodes for example. The receiver may comprise a light detector sensitive to light of the wavelength(s) emitted by the transmitter. A single light source may be provided which is split into two transmitters by passing light along two optical fibres or any other suitable arrangement of light guide.

According to a third aspect the invention provides a controller for a microprocessor based unit which causes images to be displayed on screen in response to inputs received from one or more sensors fitted to a stationary exercise bicycle of the kind in which the handlebars are free to tilt from side to side during use, the controller receiving a first signal from a crank position sensor which is indicative of the position of the crank of the bicycle within a single rotation and a second signal from a handlebar position sensor indicative of the angle of tilt of the handlebar ; and in which the controller produces an output signal whose value depends on the co-ordination of rotation of the crank with the tilt of the handlebars that is produced as the rider pedals whilst pulling on the handlebars.

When riding a bicycle the rider should pull up on one side of the handlebars at the same time as pushing down on the pedal on that side. As the pedal reaches the bottom of its stroke, the rider should then start to pull up on the other side of the handlebar and press down on the other pedal. This rhythmic motion ensures maximum power is transferred to the bicycle onto the road. It causes the bike, or at least the handlebars, to tilt from side to side in synchronisation with the pedalling. By providing an exercise bike with handlebars that are free to tilt, and monitoring the coordination of bar movement and pedals, feedback can be given which helps a novice rider to develop a correct technique.

The handlebars may be free to tilt relative to the frame of the bicycle which may otherwise be fixed in position. Alternatively the whole bicycle frame supporting the handlebars may be free to tilt from side to side in use. Correct technique in this application is not only relevant to the maximal power technique, but is also important to the safe and natural movement of the human body when riding a stationary exercise bicycle to avoid lower back pain.

Where the complete frame and handlebars tilt together the handlebar sensor may comprise an inclinometer. This can also be used where the handlebars are free to tilt relative to the frame. However, in that case a simpler arrangement using a rotary potentiometer connected between the handlebar and the frame may be used.

The output signal may have a binary output that gives one value when the synchronisation indicates a poor rider technique, and a second value indicating good rider technique. By good technique we mean that the movement of the crank and bars is "in sync" and therefore optimal for efficient use of energy and safe movement whilst riding.

The device may also process the output of a seat sensor, such as a pressure sensor which indicates whether or not the rider is seated. This can be used to tell if the rider is seated or standing. Ideally a rider should only be moving the handlebars from side to side if standing out of the saddle. If the processor determines that the rider is in fact seated this may be indicated as poor technique even if the synchronisation between handlebar and crank position is good. Alternatively it is beneficial for people to move the bars and cranks "in synch" while seated when training them in the movement or when trying to maximise the upper body workout from moving the handlebars and therefore three key states can be monitored; poor technique, good technique seated or good technique standing. The user may be rewarded for good technique whilst seated and rewarded more for good technique whilst standing. The crank sensor may be a crank sensor in accordance with the first aspect of the invention or the second aspect of the invention. It is important that it is able to indicate where the pedals are positioned within a complete revolution, or at least indicate one known position which can be compared with the position of the handlebar at that point.

The microprocessor based unit and display may be provided within a housing that can be fixed to a portion of the bicycle such as the handlebars. This may be a common housing that also includes the processor that processes the signals from the sensors. The display may comprise one or more lights which are illuminated to show if the technique is good or illuminated differently (or switched off) if technique is poor. The light may comprise LEDS. The lights may be arranged to form a bar graph display. Alternatively, instead of lights they may comprise segments of an LCD display.

Alternatively, the microprocessor-based unit may be located remotely from the exercise bicycle. It may be a personal computer, or a games console such as the Play station 3 from Sony. The display may comprise a television or monitor.

As an alternative to a visual display, or in addition, an audible indication of good or poor technique may be provided using a sounder such as a loudspeaker.

According to a fourth aspect the invention provides a stationary exercise bicycle incorporating a crank position sensor which is capable of producing an output signal indicative of the position of the crank within a complete revolution. The sensor may be in accordance with the first, second and third aspects of the invention.

According to a fifth aspect the invention provides an exercise apparatus comprising a stationary exercise bicycle according to the fourth aspect, a display and a processor device which causes the display to provide an image of at least a part of a bicycle moving through a scene, in which the speed at which the bicycle appears to move through the scene is dependent upon the rate of rotation of the crank and is scaled up or down depending on the relative motion of the crank and handlebar.

The scaling may increase the speed of the movement of the bars and cranks correspond to good technique, and either decrease it or increase it by a reduced amount as the technique becomes poorer.

The processor may therefore receive the output signals from the crank sensor and handlebar position directly, as well as an output signal indicative of riding technique.

The processor may cause the handlebar of a bicycle to be displayed, and they may tilt in sync with the tilting of the handlebar of the stationary bicycle. Alternatively a complete bicycle and rider may be displayed which tilts and has cranks that rotate to match the motion of the exercise bicycle.

The processor may comprise a microprocessor connected to a memory which stores program instructions that, when executed by the processor, cause it to drive the display in the manner required by the invention. The processor may receive input signals from sensors at one or more ports, and send signals to the display from at least one video out port. There will now be described, by way of example only, one embodiment of the present invention with reference to and as illustrated in the accompanying drawings of which:

LIST OF FIGURES

Figure 1 is an overview of a stationary exercise bicycle fitted with a number of sensing devices connected to a processing unit with a display to provide feedback on performance to a rider;

Figure 2 is a front view of a handlebar assembly as fitted to the bicycle of Figure 1 ;

Figure 3 is a plot of a typical signal output from a handlebar sensor fitted to the handlebars of Figure 2;

Figure 4 is a detailed view of a first embodiment of a crank sensing assembly fitted to the bicycle of Figure 1 that falls within the scope of the first aspect of the invention;

Figure 5 is a view of a second embodiment of a crank sensing assembly fitted to a stationary exercise bicycle such as that shown in Figure 1 ; and

Figure 6 illustrates an embodiment of a combined exercise bicycle and processor/display according to a fifth aspect of the invention.

DESCRIPTION OF SPECIFIC EMBODIMENTS Figure 1 shows an exercise bicycle that is fitted with a number of features that form embodiments in accordance with different aspects of the present invention.

The bicycle 1 comprises a frame 2 of aluminium construction having two base support legs 3, 4 that carry four feet (two feet 3a and 4a being visible in the figure) . The legs 3, 4 support the frame 2 securely in an upright position. At the front of the frame 2 is a pair of spaced lugs that carry an axle 5 of a relatively heavy flywheel 6. At the top front, above the flywheel 6, the frame has a tube that receives a handlebar assembly 100. Further back towards the rear the frame 2 has a seat tube that receives a seat post 7. The seat post in turn supports a saddle 8. Both the saddle 8 and the handlebar assembly 100 can be raised relative to the frame to suit different sized riders.

C

In the centre of the frame 2, below the saddle and about 30cm in front is a bottom bracket shell that provides a rigid mounting for a bottom bracket cartridge that includes a crank axle 9. A crankset 10, as is known in the art, is attached to the crank axle and supports pedals 10a, and a chain 11 or belt runs between the crankset and a gear sprocket carried by the flywheel 6. The gear sprocket in this embodiment is connected to the wheel through a freewheel cassette so that if the rider stops pedalling suddenly the front wheel can continue to turn.

In use the rider sits on the saddle 8 and turns the pedals 10a with their feet that in turn makes the flywheel 6 spin. A brake mechanism (not shown) is also provided which acts on the flywheel and provides some resistance to the turning of the flywheel 6. By increasing the amount of resistance applied by the brake the amount of effort needed to turn the wheel increase, making the rider work harder to maintain a given cadence (pedal revolutions per minute) . Loosening the brake reduces the amount of resistance and makes pedalling easier for that same given cadence.

As shown in perspective in Figure 2 of the accompanying drawings the handlebar assembly 100 comprises a base portion or support 101 which is held securely in the frame of the bicycle. The stem has an upper portion 110 which can rotate relative to a lower portion clamped to the bicycle.

Extending forward from the upper portion of stem 110a is a metal bar 102 which is provided with two upstanding lugs 103, 104 along each edge adjacent the stem. The lugs are spanned by a pivot bolt 105 which supports one end of a second upper, metal bar 106. The second metal bar 106 also extends from the stem 101 in a direction away from the pivot 105 and overlays the first bar. A compression spring (not shown) separates the two bars but allows the second bar 106 to be pivoted about the pivot 105 against the force of the spring. This allows for squeezing the bars down. A further compression spring (not shown) resists the bars being pulled up. Damping may be provided against each movement also.

A bracket 107 is secured to the lower stem portion bib, and two springs 108a, 108b connect the lower bar 102 to the bracket. This controls rotation of the upper second bar 106 relative to the bicycle, simulating turning and providing for resistance and return to a central position. A damper may also be provided (not shown).

The end of the second (upper) bar 106 terminates with a forked section 109 which carries two bearings that support the ends of an axle 110a. The axle supports a trapezoidal linkage assembly. The whole assembly can be tilted forwards or pulled backwards about an axis defined by the axle. A potentiometer (not shown) measures the position of the linkage relative to the upper bar 106 as it is moved about the axis or the axle. The linkage assembly comprises two horizontal lower bars 110, 111 which are spaced apart horizontally either side of the upwardly extending portion of the second bar. The lower bars define the lower edge of a trapezoid and are fixed to the axle or a plate extending therefrom.

Two links 112,113 of the trapezoid extend upwards from a respective pivot point at the end of the horizontal bars. The links 112, 113 are not quite vertical but instead lean out slightly and connect at their uppermost ends to the ends of upper horizontal bars 114a and 114b.

Two upper bars 114a and 114b are supported by the top of the links 112, 113. The links carry a clamp 115 which can be secured rigidly to a handlebar (not shown) which can be gripped by a user. In use, the handlebar can be tilted to the left or right along restrained path defined by the geometry of the trapezoidal linkage.

The two links 11 , 113 are aligned so that a vector extending from one link 112 crosses a vector extended from the other link 113 at a point directly below the handlebars which would correspond to the contact patch of a tyre of the cycle with the road.

To control the movement of the handlebar a central stop 116 is provided which is located centrally on one of the upper bars 114a and extends across towards the other bar 114b. Two control rods 109a, 109b are pivotally attached at a lower end to a point along one of the lower bars and extend up along opposite sides of the stop 116a. A coil spring assembly 117 connects the two control rods to bias them together onto the stop. In the illustration the coil spring assembly comprises two coil springs which are arranged in parallel and are connected at their ends to two pins which contact the outside of the control rods, in practice being inserted through the control rods. In the normal position of the handlebar the rods pass and touch opposing sides of the stop and are held generally in contact with the stop by the spring.

As the handlebar is moved to the left away from the central position the stop pushes one of the control rods to the left. The other is prevented from moving left by a second stop 116b on the lower bars. Thus, the movement of the handlebar stretches the spring assembly which provides resistance. The exact opposite occurs when the handlebar is moved to the right. Damping may also be provided.

The bicycle 1 is fitted with several sensors 200,300, 400 and 500 and a display /processing unit 600. These can be seen schematically in Figure 1, which primarily serves to show the approximate location of the sensors. All of the sensors produce an output signal which is fed through wires (although the signals could easily be transmitted wirelessly) to the processor device/display unit 600. In Figure 1 this unit is fitted to the handlebars whereas it could be remote from the exercise bicycle. For instance, it could be a display screen mounted on a stand, desk or wall in front of the exercise bicycle.

A first sensor 200 is connected to the bicycle 1 in such a way as to detect revolution of the flywheel of the bicycle. This comprises a magnet fitted to the wheel and a Hall Effect (or Reed switch) sensor fitted to the frame such that the magnet passes close to it as the wheel rotates. The output will be a pulsed signal with each pulse occurring as the magnet passes. The rate of the pulses indicates the wheel speed.

A second sensor 300 is connected to the handlebars which measures their position relative to a central rest position. The output of the sensor indicates whether the handlebar is tilted to the right, to the left or is in the centre. It may comprise a simple rotary potentiometer that is turned as the handlebars are tilted. It may have a digital output that varies from 0 to 256, with 0 representing a leftmost position, 128 a centre position and 256 a far right position. A typical output signal from the sensor is shown in the graph of Figure 3 of the accompanying drawings. The graph plots position against time. As can be seen the bars are not moved initially and then swings from side to side for a time, indicating that the rider is likely to be stood up out of the seat. It then returns to the centre for an extended period.

In addition to the handlebars and the sensor, the bicycle is fitted with a first embodiment of a crank sensor 500 in accordance with the first aspect of the invention. This comprises a device that has a moving part 510 that is fitted to the chainset and a fixed part 520 that is fixed to the frame near the bottom bracket. This is shown in more detail in Figure 4 of the accompanying drawings.

The rotating part 510 comprises a metal disc, typically of steel or aluminium that is fixed with its central axis aligned with the axis of rotation of the crank axle. It may in fact be the disc that carries teeth on its outer edge that engage the chain, but could be separate. The disc 510 has an annular track of alternating spokes 511 and transmissive regions 512. The width of the spokes is constant around the disc, as is the width of the transmissive regions (all when measured in a circumferential direction around an arc) . In this example a spoke has a width D. The transmissive regions are formed by cutting, milling or stamping openings into the disc during manufacture or in a mould.

The fixed portion 520 comprise an inverted U-shaped bracket secured to the frame by a clip 521 extending at right angles from the uppermost base of the bracket. The two downwardly extending arms 522,523 (which extend down from the base) of the bracket are arranged so that a circumference of the sensing disc passes between the arms and in particular so that the spokes and transmissive regions of the disc pass between the arms.

One of the arms carries two light emitting diodes 525,526 that are spaced apart by a distance d which is greater than the thickness of a spoke. One diode can be seen in Figure 4(b) , the other being hidden behind it. The other arm carries two light sensitive detectors that are responsive to the wavelength of light emitted by the light emitting diodes. The spacing between the detectors matches the spacing between the light emitting diodes. The arms 522,523 are aligned so that two pairs of diode/detector are formed which face each other across the gap between the arms that contains the sensing disc.

As the disc 510 rotates through one complete rotation of the crankset, the output of each detector 530,540 will vary many times (depending on the number of spokes) between a high level in which it receives light through a transmissive region of the disc and a low level in which the light is blocked by a spoke. Each time it varies a counter is incremented, the count value giving a measure of crank position.

An index spoke 550 or hole which differs from all the others is also provided although a separate hole that is provided at a different radial position to all the others, working with its own dedicated sensor, could be used. The passing of this spoke or hole is used as a datum to reset the counter to an initial value, typically zero, whenever a complete revolution has been made by the disc 510. The processor detects the passing of the index spoke by looking at the output of the two detectors 530,540. Where a separate index hole or spoke is provided a third detector may be provided which detects the passing of this index spoke or hole. Because the width of the spokes and transmissive regions and the spacing between the detectors has been carefully chosen it is possible to determine the direction in which the crank is being rotated. This can be achieved if the spacing between the detectors is anywhere between slightly more than the distance between opposing edges of a spoke, and slightly less than the sum of the widths of one spoke and one transmission region.

The output of the two detectors is passed through cables to a processing device that combines the two signals to determine the direction of rotation and a dead reckoned position measurement. The processor performs this function by counting transitions in the output of one of the detectors to give a measure of position relative to a start count, and by looking at the output state of one detector at the time that the other changes state to determine the direction of rotation. For example consider the case where the disc shown in Figure 4(c) starts to rotate clockwise. After a time the detector 540 will be covered by the spoke 511 and thus its output will undergo a transition. The processor checks the output of the other detector 530 and sees that it is high (light reaches it through the region 512) . This indicates that the disc 510 is moving clockwise.

On the other hand, consider that it starts to rotate anticlockwise from the position shown in Figure 4(c) , i.e. from right to left across the page. In this case, the detector 540 will again undergo a transition from high to low, but due to a different spoke passing over it from the right. The processor, of course, cannot tell which spoke is passing simply by looking at the output of sensor 540. However, at the time of the transition the other detector 530 will read low as it is covered by a spoke. This indicates that the disc 510 has rotated anti-clockwise.

The processor is arranged therefore to check for a transition of one sensor (always the same one) from high to low (or each time it goes from low to high) and at the time of transition look at the output from the other sensor to indicate the direction of rotation.

The bicycle is also fitted with a rider position sensor 400 which detects the position of the rider on the bicycle. In particular it determines whether the rider is seated or standing and optionally whether they are sitting tall with arms stretched away from the handlebars or crouched down low with chest dropped towards the handlebars.

A processor unit, shown fitted to the handlebars in Figure 1, drives a display which is mounted to the front of the housing of the processor where it is clearly visible to the rider. The display shows the wheel speed, the pedal cadence and the elapsed time since the rider started to use the bicycle.

In addition, the processor analyses the signals output from the handlebar sensor and the cadence sensor to determine whether the rider is using a correct technique when using the equipment.

Specifically, if the rider is standing out of the saddle then they should swing the bars in a predefined temporal relationship with the movement of the pedals. As the rider pulls the right hand side of the bar up, the right hand pedal should be pushed down from the top to the bottom of its stroke. The left hand side of the bars should then be pulled up as the left pedal is pressed down, and so on.

To determine if they are in the correct co-ordination, the position of the bars is compared with the position of the cranks. This could be done at fixed points in the cycle, e.g. whenever the bars are at their extremes of position or whenever the crank sensor output changes. Alternatively, it may be done by sampling the bar position and crank position at regular time intervals (say every 0.1 seconds) and comparing the two using a look up table. If the values are correct, or within an acceptable range, then an indication that the technique is good is issued. If not, a warning tone or image can be displayed or a message announced.

Varying degrees of warning tone or image can be displayed relative to the perfection in timing of the co-ordination.

As an alternative to the processor unit a personal computer 800 may be provided which receives the signals from the sensor devices 200,300,400,500 fitted to the exercise bicycle. This is shown in Figure 6 of the accompanying drawings, where the computer is located on the floor some distance from the bicycle. The computer includes a display driver and is connected to a display 900 upon which images can be presented as generated by the computer.

The computer 800 can run a game or training program in which the images on the display screen 900 are modified according to the output of the sensors. The processing of the signals to determine riding form could be performed by the personal computer removing the need for the handlebar mounted unit shown in Figure 1.

In the example shown, a virtual rider 910 on a bicycle is displayed on the screen moving through a virtual scene 920 such as a mountain bike trail.

The scene may be represented as a 3D image or as a 2.5D image. The speed at which the displayed rider 910 appears to move through the scent

920 is controlled by the processor 800 in response to the output from the various sensors 200-600. In particular, if a rider is using good technique with the bars and cranks moving in the correct sync then the virtual rider

910may be made to appear to cycle faster through the scene 920. Various modifications are envisaged within the scope of the present invention. For example, as shown in Figure 5 of the accompanying drawings a crank position sensing assembly 1000 can be constructed using a set of magnets 1010 mounted at circumferentially spaced locations around a disk and a set of reed switches or Hall Effect switches 1020, 1030 fixed relative to the frame. As the magnets 1010 pass the switches they cause them to close, producing an output pulse which ends as the magnets pass. An index magnet 1040 and corresponding sensor 1030 can be provided, whilst a pair of spaced switches in line with the magnets allows the direction of rotation to be determined.

In a further modification, only one sensing element may be provided to generate the count signal, and another to provide the index which resets the count, or is otherwise used to check that the count is correct. This loses the ability to determine direction of rotation but is easier to construct and since most pedalling is performed in one direction may prove adequate for many applications.

Claims

1. A crank position sensor assembly for use in combination with an exercise bicycle having at least a frame and a crank that rotates relative to the frame about an axis, the sensor assembly comprising: a set of magnetic elements fixed in position relative to the crank for rotation with the crank, the magnetic elements being located at spaced positions around the axis of rotation of the crank; a first sensing element which is fixed relative to the frame of the bicycle in a position whereby rotation of the crank causes each of the magnets to move past the first sensing element in turn, the first sensing element producing an output signal when a magnetic element is aligned with the sensing element; a second sensing element which is fixed relative to the frame of the bicycle in a position whereby rotation of the crank causes each of the magnets to move past the second sensing element in turn, the second sensing element producing an output signal when a magnetic element is aligned with the second sensing element; and a processor which processes the output signals from the first and second sensing elements, the processor determining both the position of the crank and its direction of rotation from the outputs of the first and second sensing elements.

2. A crank position sensor assembly according to claim 1 in which the relative angular spacing of the sensing elements and the spacing between the magnetic elements is such that the direction of rotation of the crank can be unambiguously determined by the processing unit from the pattern of change of the output of both the sensing elements by arranging the assembly such that when a transition of the output signal from one element occurs, the value of the output of the other detector at that time will provide an indication of the direction of rotation of the crank.

3. A crank position sensor assembly according to claim 1 or 2 in which the spacing between the first and second sensing elements is between slightly more than the distance between opposing edges of a magnetic element, and slightly less than the sum of the widths of N elements and N spaces between adjacent magnetic elements where N is an integer value.

4. A crank position sensor assembly which further includes a second, index, magnetic element supported in a fixed position relative to the crank and which rotates with the crank, a further sensing element which is fixed relative to the frame of the bicycle in a position whereby rotation of the crank causes the index magnetic element to move past the further sensing element once per revolution of the crank, the further sensing element producing an output signal when the second magnetic element is aligned with the further sensing element and in which the processor uses the output of the further sensing element to provide a datum point for the angular position signal, resetting the angular position signal if the position indicated by that signal and the position indicated by the datum become misaligned.

5. The assembly of claim 1 in which the processor provides an output signal which comprises a count, the count being incremented each time the first sensing element produces an output signal and in which the output of the second sensing element is used to reset the count.

6. The assembly of any preceding claim in which the sensing elements comprise reed switches or Hall Effect sensors.

7. The assembly of any preceding claim in which three or more magnetic elements are provided.

8. The assembly of any preceding claim in which the second magnetic element is combined with one of the first magnetic sensing elements as a single sensing element.

9. The assembly of claim 8 in which the combined element generates a stronger magnetic field or a different shaped magnetic field to the other

•,• first magnetic elements so that only this element causes the output of the second sensing element to change.

10. A crank position sensor assembly for use in combination with an exercise bicycle having at least a frame and a crank that rotates relative to the frame about an axis, the sensor assembly comprising: a modulating element fixed relative to a crank of the bicycle so that it rotates with the crank about its axis of rotation, the element carrying a track of modulating teeth or spokes and also an index spoke or tooth that is located at a predetermined position relative to the crank, a first transmitter means which transmits radiation which is located at one end of a first transmission path and second transmitter means which transmits radiation which is located at one end of a second transmission path , a first receiver means which is located at the other end of the first transmission path and which produces, as the crank rotates, at least one first output signal that varies according to the amount of radiation emitted by the transmitter that is incident upon it as modulated by the track of teeth or spokes and a second output signal that varies accordning to the amount of radiation emitted by the transmitter that is incident upon it as modulated by the index spoke or tooth, a second receiver means which is located at the other end of the first transmission path and which produces, as the crank rotates, at least one first output signal that varies according to the amount of radiation emitted by the transmitter that is incident upon it as modulated by the track of teeth or spokes, the light transmitted on the second path being modulated differently to the light transmitted on the first path, both the transmitter means and receiver means being fixed relative to the frame of the bicycle, and a processor which processes the first and second output signals from the first and second receiver means and determines the position of the crank therefrom and in which the angular spacing of the transmission paths and the width of the spokes/transmissive regions is chosen such that the processor can determine the direction of rotation of the crank from the pattern of change of the output of both the receiver means.

11. A crank position sensor assembly of claim 10 in which the relative angular spacing of the transmission paths and the configuration of the teeth is chosen such that the pattern of change of the output of both the light sensors enables the direction of rotation of the crank to be unambiguously determined by the processing unit by arranging the assembly such that when a transition of the output signal from one element occurs, the value of the output of the other detector at that time will provide an indication of the direction of rotation of the crank.

12. A crank position sensor assembly according to claim 10 or claim 11 in which the spacing between detectors is between slightly more than the distance between opposing edges of a spoke, and slightly less than the sum of the widths of N modulating teeth or spokes and N transmission regions between adjacent modulating teeth or spokes where N is an integer value.

13. The assembly of claim 10,11 or 12 in which the receiver means comprises a first and a second receiver.

14. The assembly of any one of claims 10 in which the modulating element comprises a spoked wheel arranged concentrically with the axis of rotation of the crank, the wheel having a plurality of opaque spokes separated by transmissive regions between the spokes, whereby as the crank rotates the spokes and transmissive regions alternately pass through the transmission paths.

15. The assembly of any one of claims 10 to 14 in which the processing means includes a counter which is set to a known start value when the crank is in a known position and in which the processing means increments the counter each time a transition in the output of one of the receivers/sensing elements occurs.

16. The assembly of any one of claims 10 to 15 in which the transmitter comprises a light source, either of visible or infrared light or both and the receiver (s) comprise light detectors sensitive to light of the wavelength(s) emitted by the transmitter.

17. A controller for a microprocessor based unit which causes images to be displayed on screen in response to inputs received from one or more sensors fitted to a stationary exercise bicycle of the kind in which the handlebars are free to tilt from side to side during use, the controller receiving a first signal from a crank position sensor which is indicative of the position of the crank of the bicycle within a single rotation and a second signal from a handlebar position sensor indicative of the angle of tilt of the handlebar ; and in which the controller produces an output signal whose value depends on the co-ordination of rotation of the crank with the tilt of the handlebars that is produced as the rider pedals whilst pulling on the handlebars.

18. The controller of claim 17 which also processes the output of a seat sensor, such as a pressure sensor which indicates whether or not the rider is seated to determine whether the rider is seated or standing.

19. An exercise apparatus comprising a stationary exercise bicycle a controller according to claim 17 or 18, a display and a processor device which causes the display to provide an image of at least a part of a bicycle moving through a scene, in which the speed at which the bicycle appears to move through the scene is dependent upon the rate of rotation of the crank and is scaled up or down depending on the relative motion of the crank and handlebar.