Generator for an Exercise Machine

Abstract

A generator for use in an exercise machine with a rotating flywheel is described. The generator is configured to receive kinetic energy and convert the kinetic energy to electrical energy wherein the

Description

Field of the Disclosure The present disclosure relates generally to generators for use in exercise machines. The invention further relates to exercise machines comprising generators. Background Exercise machines can be used to mimic the experience of different forms of exercise for the user, for example rowing, skiing, and cycling. Through using an exercise machine, the user can convert physical movement into rotational kinetic energy. The rotational kinetic energy can be dissipated, for example by a fan in the exercise machine, and ultimately end up as heat within the room. The rotational kinetic energy can also be converted to electrical energy using a generator and therefore utilised in a more productive way. The resistance experienced by the user is determined by this flow of energy and can be managed by the power output of the generator. Aspects of the present disclosure seek to provide a generator for use in exercise machines that manages the resistance experienced by the user in a similar way to the original fan. Summary According to a first aspect of the present disclosure, there is provided a generator for use in an exercise machine with a rotating flywheel, the generator configured to receive kinetic energy and convert the kinetic energy to electrical energy, wherein the generator is an axial flux permanent magnet, AFPM, generator, comprising a control system and the control system comprises a useful power circuit and a dissipation power circuit, and the control system is configured to manage the flow of the electrical energy to the useful power circuit and / or the dissipation power circuit, when in use. In this way, there is provided a generator which directs energy to a useful output while maintaining the resistance provided by an exercise machine comprising the generator. In this way, an exercise machine comprising the generator can provide a similar user experience to an exercise machine of the prior art comprising a fan, by managing the resistance provided by the machine. The use of an energy dissipation power circuit in combination with a useful power circuit allows the generator to control the revolutions per minute (RPM) to power relationship, regardless of the activity of the useful power circuit. The level of resistance experienced by the user will increase as the RPM increases, but is not significantly impacted by the change in circuit control between the useful power circuit and the dissipation power circuit. The AFPM generator provides a high rotational moment of inertia, similar to that of the fans found in exercise machines. In this way, the AFPM generator provides the user with a similar experience when the generator is used in an exercise machine. The AFPM generator has an ironless core which ensures there is no cogging torque effect, and provides increased efficiency as no gears are needed. The AFPM generator is also low cost and has no wearing parts and so is a low maintenance generator. Preferably, the control system is configured to direct the generated energy to the dissipation power circuit once the useful power circuit has reached a maximum power threshold. In this way, the device is configured to maximise the useful output of the generator while maintaining the resistance experienced by the user. Preferably, the useful power circuit maximum power threshold is 400 W. In this way, the useful power circuit is designed to accommodate the maximum power a user can produce for a prolonged period. Preferably, the generator comprises a rotating component having a moment of rotational inertia matching that of a fan of an exercise machine. In this way, the generator can be retrofitted into current exercise machines in place of the fan. Preferably, the generator comprises a rotating component having a moment of rotational inertia in the range of 0.11-0.115 kg.m2. In this way, the moment of rotational inertia of the generator is similar to the moment of rotational inertia of the fan found in Concept2 exercise machines, although the use of this invention with other brands and or products is envisaged. Preferably, the moment of rotational inertia of the generator is similar to the moment of rotational inertia of the fan it replaces. More preferably, the moment of rotational inertia of the fan is identical to the moment of rotational inertia of the fan it replaces. Therefore, the generator can be retrofitted into current exercise machines in place of the fan. Preferably, the control system comprises a user input, wherein the user input is the drag factor, DF. In this way, the user can increase or decrease the resistance experienced and therefore increase or decrease the difficulty of an exercise machine comprising the generator. Preferably, the control system includes modifiable preset variable for maximum output current of the useful power circuit, lout max, maximum output voltage of the useful power circuit, Vout max, and minimum output voltage of the useful power circuit, Vout min; and wherein the control system is configured to carry out a calculation cycle, and wherein in a calculation cycle the control system measures the following variables: revolutions per minute, RPM; total current, Itotal; total voltage, Vtotal; output current, Iout; output voltage, Vout; and DF. Preferably, the control system is configured to maintain Perror to within 1% of Prequired; wherein Perror and Prequired are calculated using the following equations: Perror — Prequired — Pactual Pactual — Vtotal- Itotal Vtotal- 712 18. Rw Prequired = LOOKUPTABLE (RPM,DF) where Rw is the internal resistance of the generator, LOOKUP TABLE (RPM,DF) is stored in the control system, and DF is a drag factor that can be inputted by a user. In this way, the generator is able to emulate the fan currently used in exercise machines within 1%, and therefore provide a consistent experience and resistance level for the user. More preferably, the generator is configured to maintain the Perror to within 0.5% of Prequired. In this way, a more consistent feel and performance is maintained. Preferably, the DF is in the range of 70 to 250. Preferably the Rw is in the range of 0.00 to 10.00 when the generator operates at a temperature of 20 °C. Preferably, the control system is configured to control energy transfer to the dissipation and useful power circuits via metal-oxide-semiconductor field-effect transistors, MOSFETs. Preferably, the MOSFETs have a switching frequency of at least 20 kHz. Preferably, the useful power circuit will comprise a Buck Switched Mode Power Supply (SMPS) to provide a controlled Vout. Preferably, the controller is configured to monitor the temperature of the useful and dissipation power circuits. Preferably, the control system has two set temperature limits for the useful power circuit, a warning temperature and a shutdown temperature, wherein the control system is configured to reduce Iout max if the temperature of the useful power circuit is above the warning temperature; and wherein the control system is configured not to direct energy to the useful power circuit if the temperature of the useful power circuit is above the shutdown temperature. Preferably, the control system has two set temperature limits for the dissipation power circuit, a dissipation warning temperature and a dissipation shutdown temperature, wherein the control system is configured to reduce Prequired if the temperature of the dissipation power circuit is above the dissipation warning temperature; and wherein the control system is configured not to direct energy to the dissipation power circuit if the temperature of the dissipation power circuit is above the dissipation shutdown temperature. Preferably, the device is configured to operate to a voltage of up to 200 V DC. Preferably, the control system is configured to receive power from the generator. In this way, when the generator is used within an exercise machine, the control system is powered by the energy generated by the user of the exercise machine. Preferably, the control system comprises a USB input. Preferably, the control system is configured to be able to provide a list of variables to a device such as a laptop when said device is connected to the control system via the USB input. In some embodiments the control system may be configured to provide the information to a device via Bluetooth and / or Wi-Fi. Preferably, the control system is configured to receive information, such as an updated drag factor or system settings, and update the relevant variables. In this way, the pre-set variables may be modified. Examples of the pre-set variables include the type of load the useful power circuit is connected to, e.g. battery, portable power station, fixed load. Other examples of pre-set variables are the nominal Vout voltage, the Vout max, the Vout min, Iout Estimate, the DF, and the Rw. Preferably, the control system is configured to direct energy to the dissipation power circuit, and not the useful power circuit, when Vtotal is less than Voutmin. In this way, the generator does not direct energy to the useful power circuit until a minimum voltage is reached. Preferably, the control system is configured not to direct energy to the useful power circuit when Vout is greater than or equal to Vout max. In this way, the control system is configured to ensure Vout does not exceed Vout max. Preferably, the control system is configured to not direct energy to the useful power circuit if Iout is greater than or equal to Iout max. Preferably, the control system is configured to carry out the calculation cycle at least every millisecond. In this way, the generator is configured to quickly react to changes in order to maintain a more consistent experience for the user. In some embodiments, the useful power circuit is connected to a battery. In this way, the power generated by the user of an exercise machine comprising the generator can be utilised to charge a battery. In some embodiments, the battery has a voltage of 12 V. In some embodiments, the battery has a voltage of 24 V. Preferably, the control system is configured to direct energy to the useful power circuit when PERROR is greater than 0; and wherein the control system is configured to direct energy to the dissipation power circuit when: Vtotal is less than Vouymin, Vout is greater than or equal to Vout max, or Iout is greater than or equal to Iout max. In some embodiments, the useful power circuit is connected to a fixed load. In this way, the power generated by the user of an exercise machine comprising the generator can be utilised to power a fixed load. In some embodiments, the fixed load is a television screen, a computer and / or a lamp. Preferably, the fixed load is a television screen. Preferably, the control system is configured to direct energy to the dissipation power circuit when Perror is greater than 0, and to only direct energy to the useful power circuit when: Vtotal >VouTmin; Vout <Vout max; Prequired average >Vout NOMINAL x Iout EST x 1.1; and Vout <Vout NOMINAL; wherein Iout EST is the estimated current of the fixed load and Vout NOMINAL is the nominal output voltage of the fixed load. The Iout EST and the Vout NOMINAL are taken from a datasheet of the fixed load. In this way, the useful power circuit is only used when the user is generating more power than the fixed load. In this way, power is only directed to the useful power circuit when the user is generating enough energy to power the fixed load. For example, where the fixed load is a television screen, the control system only directs energy to the television screen through the useful power circuit when the user is generating enough energy to power the television screen. Preferably, the dissipation power circuit is connected to a resistor configured to dissipate the energy as heat. In this way, the energy directed to the dissipation power circuit is dissipated as heat. Preferably, the dissipation power circuit is connected to the resistor via a pulsewidth modulation, PWM, circuit. Preferably, the power limit of the dissipation power circuit is 1500 W. In this way, the dissipation power circuit is able to receive the maximum power a user of a rowing machine is able to generate for approximately 10 seconds. Preferably, the control system is mounted on a metal base plate. More preferably, the controller is mounted on an aluminium base plate. In this way, there is increased heat dissipation from the controller through the base plate and the risk of overheating is reduced. Preferably, all heat generating components are thermally connected to the base plate. In this way, heat dissipation from all heat generating components can be increased in order to reduce the risk of overheating. The components connected to the base plate must be thermally connected but electrically isolated. In this way, the base plate can act as a heat sink to reduce the temperature of the components without interfering with their functions. Preferably, the controller is located within a housing. In this way, the generator is protected from shock, vibration and moisture. In a second aspect of the invention, there is provided an exercise machine comprising the generator of any of the first aspect of the invention. All the advantages of the first aspect of the invention are envisaged to apply to the second aspect of the invention. Preferably, the exercise machine comprises a first and second LED, wherein the first LED is on when the useful power circuit is in use, and the second LED is on when the dissipation power circuit is in use. In this way, when the exercise machine is in use, the user can identify which of the circuits are being powered. Preferably, the exercise machine comprises a third LED, wherein the third LED is configured to indicate the status of the control system. For example, if the control system is over a preset temperature, the third LED will flash as a warning, and if the temperature reaches a higher preset temperature, the third LED is on solidly. In this way, the user is made aware of the temperature and status of the control system. The generator comprises at least one rotor and at least one stator. Preferably, the generator comprises at least two rotors and at least one stator. Preferably, the stator comprises a plurality of coils. More preferably, the stator comprises three coils. Still more preferably, the stator comprises six coils. Preferably, the plurality of coils are spaces evenly around the perimeter of the stator. Preferably, the stator comprises a plurality of coils where each coil is identical. Preferably at least one coil comprises copper wire. More preferably every coil comprises copper wire. Preferably, the copper wire has a cross section area in the range of 0.75 mm2 to 1.75 mm2 inclusive. More preferably, the copper wire has a cross section area in the range of 1.0 mm2 to 1.5 mm2 inclusive. Most preferably, the copper wire has a cross section area of 1.25 mm2. Preferably, the copper wire is polyester enamelled. Preferably, each coil comprises between 75 and 175 turns or wire inclusive. More preferably, each coil comprises between 100 and 150 turns of wire inclusive. Most preferably, each coil comprises 125 turns of wire. Preferably, the stator comprises a coil former. More preferably at least one coil is located in an aperture with the coil former. Still more preferably, the coil former comprises a plurality of apertures, each aperture comprising a separate coil. Most preferably, the coil former comprises six apertures, each aperture comprising a separate coil. In this way, six separate coils are located within individual apertures within the coil former. Preferably, at least one coil is held within an aperture with an adhesive. Preferably, the adhesive comprises a water activated polyurethane formula. Preferably, the stator comprises a plurality of coils, and the coils are connected into pairs in a star configuration. More preferably, the stator comprises six coils connected into three pairs. Preferably, the stator is a three phase stator. Preferably, the rotor comprises at least one metal plate. More preferably, at least one plate comprises steel. Still more preferably, the rotor comprises two plates, each plate comprising steel. Preferably, where the rotor comprises two plates, there is an air gap between the plates. Preferably, the rotor comprises a spacer piece. As such, the spacer piece maintains the air gap between the plates. Preferably, the air gap between the plates is between 10 mm and 50 mm inclusive. More preferably the air gap between the plates is between 20 mm and 40 mm inclusive. Still more preferably, the airgap between the plates is 30 mm. Preferably, at least one plate comprises an aperture. More preferably, at least one plate comprises a plurality of apertures. Yet more preferably, the plate comprises eight apertures. Still more preferably, the apertures are equally spaced around the circumference of the plate. Most preferably, the rotor comprises two plates, each plate comprising a plurality of apertures equally spaced around the circumference of their respective plates. Preferably, the plate comprises eight apertures. Preferably, the rotor comprises a plurality of magnets, each magnet located within an aperture in the at least one plate. More preferably, each aperture within the plate houses a magnet. Preferably, at least one magnet is a ferrite magnet. More preferably each magnet is a ferrite magnet. Preferably at least one magnet is a neodymium magnet. More preferably, each magnet is a neodymium magnet. Preferably, at least one magnet has dimensions of 50 mm by 50 mm by 10 mm. Preferably, each magnet has dimensions of 50 mm by 50 mm by 10 mm. Preferably the magnets contained within the plurality of apertures in the at least one plate have alternating polarities. As such, around at least one plate, the magnets are oriented such that north then south poles are presented when one side of the plate is considered. In some embodiments, the exercise machine is a rowing machine. In some embodiments, the exercise machine is a cycling machine. In some embodiments, the exercise machine is a skiing machine. In some embodiments, the exercise machine is a stepper machine. Brief Description of the Drawings The disclosure will be further described with reference to examples depicted in the accompanying figures in which: Figure 1 is a diagram of a control system of a generator of the invention; Figure 2 is a schematic of a circuit of a generator of the invention, Figure 3 is a schematic of a stator for a generator in accordance with the present invention; and Figure 4 is a schematic of a rotor for a generator in accordance with the present invention. Detailed Description The following description presents particular examples and, together with the drawings, serves to explain principles of the disclosure. However, the scope of the invention is not intended to be limited to the precise details of the examples, since variations will be apparent to a skilled person and are deemed to be covered by the description. Terms for components used herein should be given a broad interpretation that also encompasses equivalent functions and features. In some cases, alternative terms for structural features may be provided but such terms are not intended to be exhaustive. The description herein refers to examples with particular combinations of features, however, it is envisaged that further combinations and cross-combinations of compatible features between embodiments will be possible. Indeed, isolated features may function independently as an invention from other features and not necessarily require implementation as a complete combination. Figure 1 is a diagram of a control system 100 of a generator of the invention. The control system 100 comprises a generator input 101, an output 102, a resistor 103, a drag factor input 104, a USB input 105, LED indicators 106, and fixing holes 107. Figure 2 is a schematic of a circuit of a generator of the invention. The schematic shows the MOSFETs S1 for the useful power circuit and S2 for the dissipation power circuit. The primary control input is RPM, derived from a 3-phase input voltage from the generator. Two of the phases are measured and a ‘zero-crossing’ point detection circuit that derives the frequency of the incoming voltage. This shall be converted into RPM by multiplying it by 15. The level of resistance will increase as the RPM increases which is equivalent to real world rowing, cycling, or skiing. The Line-to-Line voltage of the generator varies from 0 to 110 V AC RMS. This results in a 3-phase full wave rectified DC voltage of 0 to 150 V DC. The Open Circuit voltage of the generator will generally increase in proportion with the RPM of the generator. The frequency of the output voltage varies from 0 to 160 Hz and increases in proportion with the RPM of the generator. The internal impedance of each generator winding (Rw) is approximately 2.55 Ohms at 20°C. Additionally, the DF is a user input that is effectively a multiplier for the resistance, like going up-hill on a bike or using a larger oar on a rowing boat. The DF input is derived from a rotary variable resistor supplied on a flying lead as part of the control system. The rotary variable resistor is connected to the controller via a connector and is mountable on the outside of the fan cover though a drilled hole. The control system comprises two power circuits, the useful power circuit, and therefore Vout is controlled by a MOSFET 1 and a dissipation power circuit and therefore the power resistor Rl is controlled by MOSFET 2. The control system uses the two power circuits to maintain PowerERROR to within 1% of PowerREouiRED. The control system is configured to provide a useful power circuit with a slow response to the change in RPM input and a dissipation power circuit with a faster response to the RPM input. In this way, the useful power circuit receives a steady base load of power with the dissipation power circuit receiving the fluctuations caused by the variability of a user operating an exercise machine. The control system is mounted on an aluminium base plate to aid heat dissipation. The control system monitors the temperature of the circuits and is configured to respond if the temperature reaches a warning temperature or a shutdown temperature. The control system is configured to reduce Iout max to 15 Amps if the temperature of the useful power circuit is above the warning temperature and the control system is configured not to direct energy to the useful power circuit if the temperature of the useful power circuit is above the shutdown temperature. The control system is configured to reduce Prequired to 300 W if the temperature of the dissipation power circuit is above the dissipation warning temperature; and wherein the control system is configured not to direct energy to the dissipation power circuit if the temperature of the dissipation power circuit is above the dissipation shutdown temperature. The dissipation power circuit has a maximum average power capacity of 1500 W and is configured to operate with voltages of up to 200 V DC. The control system is configured to receive power from the generator therefore when the generator is used within an exercise machine, the control system is powered by the energy generated by the user of the exercise machine. The control system is configured to allow a user to select the load type from a battery, an MPPT, and fixed load. The control system is also configured to allow the user to modify the pre-set variables: Nominal Vout voltage, Vout max, Vout min, DF, Rw. Several embodiments of the example were tested with the useful power circuit: not functioning; connected to a fixed load, a 12 V lamp; connected to a MPPT inverter load, an Enphase IQ7-60-2-INT; connected to a MPPT battery charger load, a Goal Zero Yeti 200X; and connected to a battery, 24V LiFePO410Ahr. The prototype was tested across three distances at world record time: 500m -1 minute 10.5 seconds, 2,000m - 5 minutes 35.8 seconds, and 10,000m - 31 minutes 5.2 seconds. Turning to Figure 3, there is depicted a stator 200 for use in a generator according to the present invention. Here, the stator comprises six coils 210, each coil comprising 125 turns of 1.25 mm2 polyester enamelled copper wire. The coils 210 are spaced evenly and uniformly around the circumference of the stator 200. Here the coils are held in position in recesses within the coil former 220. Adhesive may be used to fix the coils 210 into position within the coil former 220. Additionally, a cover (not shown) may be used to further locate the coils within the coil former to provide the final stator 200. During assembly of the stator 200, the coils 210 are connected into pairs in a star configuration. Here, the star point is left floating. Turning to Figure 4, there is depicted two halves of a rotor 300 for use in a generator according to the present invention. The rotor comprises two steel plates 310, each of the steel plates comprising ferrite magnets 320 secured in recesses within the plates 310. As the ferrite magnets 320 are located within the recesses within the plates 310, this ensures the magnets 320 are positioned correctly within the plates 310 and the rotor 300 itself. In the presently described embodiment, each plate 310 comprises eight recesses for ferrite magnets 320. When the ferrite magnet 320 are placed into the plate 310, they are arranged in an alternating North-South arrangement as illustrated in Figure 4. After the magnets are positioned, the two plates 310 are combined to form the rotor 300. When the two plates 310 are combined to form the rotor 300, an air gap remains between the plates 310. During assembly, the air gap may be maintained by a spacer element (not shown). After assembly of the rotor 300 and the stator 200, the two are combined to form the generator of the present invention.

Claims

1. A generator for use in an exercise machine with a rotating flywheel, the generator configured to receive kinetic energy and convert the kinetic energy to electrical energy,wherein the generator is an axial flux permanent magnet, AFPM, generator comprising a control system and the control system comprises a useful power circuit and a dissipation power circuit; andthe control system is configured to manage the flow of the electrical energy to the useful power circuit and / or the dissipation power circuit when in use.

2. The generator of claim 1, wherein the control system is configured to direct the generated energy to the dissipation power circuit once the useful power circuit has reached a maximum power threshold.

3. The generator of claim 2, wherein the maximum power threshold is 400 W.

4. The generator of any of the preceding claims, wherein the generator comprises a rotating component having a moment of rotational inertia in the range of 0.110 -0.115 kg.m2.

5. The generator of any of the preceding claims, wherein the control system comprises an user input, wherein the user input is the drag factor, DF.

6. The generator of claim 5, wherein the control system includes modifiable preset variable for maximum output current of the useful power circuit, louymax, maximum output voltage of the useful power circuit, Vout max, and minimum output voltage of the useful power circuit, Vout min; and wherein the control system is configured to carry out a calculation cycle, and wherein in a calculation cycle the control system measures the following variables: revolutions per minute, RPM, total current, Itotal, total voltage, Vtotal, output current, Iout, output voltage, Vout, andDF.

7. The generator of claim 6, wherein the control system is configured to maintain Perror to within 1% of Prequired; wherein Perror and Prequired are calculated using the following equations:Perror — Prequired PactualPrequired = LOOKUPTABLE (RPM,DF)where Rw is the internal resistance of the generator, and LOOKUP TABLE (RPM.DF) is stored in the control system.

8. The generator of claim 7, wherein the control system is configured to maintain Perror to within 1% Of Prequired-9. The generator of claim 6, claim 7 or claim 8, wherein the control system is configured to direct energy to the dissipation power circuit and not the useful power circuit when Vtotal is less than Vout min.

10. The generator of claims 6 to 9, wherein the control system is configured not to direct energy to the useful power circuit when Vout is greater than or equal to Vout max.

11. The generator of any of claims 6 to 10, wherein the control system is configured to carry out the calculation cycle at least every millisecond.

12. The generator of any of claims 6 to 11, wherein the useful power circuit is connected to a battery.

13. The generator of claim 12, wherein the control system is configured to direct energy to the useful power circuit when Perror is greater than 0; andwherein the control system is configured to direct energy to the dissipation powercircuit when:Vtotal is less than Vout min,Vout is greater than or equal to Vout max, orIout is greater than or equal to Iout max.

14. The generator of any of claims 6 to 11 of any preceding claim, wherein the useful power circuit is connected to a fixed load.

15. The generator of claim 14, wherein the control system is configured to direct energy to the dissipation power circuit when Perror is greater than 0, and to only direct energy to the useful power circuit when:Vtotal >Voutmin;Vout <Vout max;Preouired average >Vout NOMINAL x Iout EST x 1.1; andVout <Vout NOMINAL;wherein Iout EST is the estimated current of the fixed load and Vout NOMINAL is the nominal output voltage of the fixed load.

16. The generator of any preceding claim, wherein the dissipation power circuit is connected to a resistor configured to dissipate the energy as heat.

17. The generator of any preceding claim, wherein the dissipation power circuit is connected to the resistor via a pulse-width modulation, PWM, circuit.

18. The generator of any preceding claim, wherein the power limit of the dissipation power circuit is 1500 W.

19. An exercise machine with a rotating flywheel comprising the generator of any of the preceding claims.

20. The exercise machine of claim 19, wherein the exercise machine is a rowing machine.

21. The exercise machine of claim 19, wherein the exercise machine is a cycling machine.

22. The exercise machine of claim 19, wherein the exercise machine is a skiing machine.

23. The exercise machine of claim 19, wherein the exercise machine is a stepper machine.16

Images