Patent Application
20120322621
1. Field of the Invention
The present invention is directed generally to exercise devices, and more particularly to devices that measure power output of users operating bike trainers.
2. Description of the Related Art
Bike trainers (or “bicycle trainers”) have been used by bicycling enthusiasts to support their bicycles for stationary riding. Rather than ride in cold, hot, or rainy weather, a cyclist may use the trainer to ride indoors and obtain an aerobic, cardiovascular workout. Bike trainers also obviate the need for purchasing a separate stationary bicycle for persons who want to occasionally workout while, for example, reading or watching television.
A typical bike trainer has a frame onto which a user mounts a bicycle. The rear wheel of the bicycle contacts a roller or like mechanism connected to a resistance unit. Resistance to the rotation of the rear wheel may be adjustable. In addition, it would be desirable for a resistance unit to provide increased resistance as the rotation of the wheel is increased, so that more energy is required to pedal the bicycle and the rider receives a greater workout.
Training using a power measurement device (“power meter”) is becoming increasingly popular. In general, a power meter is a device on a bicycle or bicycle trainer that allows measuring of the power output of the rider. Power meters may include a computer (e.g., mounted on a handlebar) that displays information about the power output generated by the rider such as instantaneous, maximum, and average power. Power meters provide an objective measurement of real output that allows training progress to be tracked very simply—something that is more difficult when using, for example, a heart rate monitor alone. Power meters provide feedback to the rider about their performance and measure their actual output. Therefore, an athlete performing “interval” training (e.g., alternating intervals of high-intensity training and low-intensity training) using a power meter can instantly see that they are producing 250 watts, for example, instead of waiting for a heart rate to climb to a certain point. Additionally, while an athlete who is not rested or not feeling entirely well may train at their normal heart rate, they are unlikely to be producing their normal power—a heart rate monitor will not reveal this, but a power meter will. Since power meters are used by athletes to provide feedback while training, it is desirable for power meters to provide accurate and consistent measurements.
The present invention is directed to systems and methods for measuring power output of a cyclist using a bike trainer that may be operated by a user for stationary riding when coupled to a conventional bicycle. The systems disclosed herein account for environmental conditions that affect the power measurements so that more accurate measurements can be provided, thereby improving the training experience of cyclists. Initially, with reference to
Advantageously, the bike trainer 10 includes features described below that simulate the “feel” of riding a moving bicycle by providing resistance and inertia similar to that of a bicycle when operated on a flat paved road surface. The bike trainer 10 also includes features that permit simple coupling and decoupling to the bicycle 100, which allows users to easily use the bike trainer 10 without requiring a time consuming setup process. As an example, users may wish to use the bike trainer 10 when weather conditions are not conducive to riding outdoors, or when locations to ride a bicycle are otherwise undesirable or unavailable. Further, the bike trainer 10 is configured to support a user of the bike trainer in a fashion such that the user is sturdily supported without having to worry about losing his or her balance.
To use the bike trainer 10, a user first removes the rear wheel of the bicycle 100, secures the rear dropouts 106 of the bicycle to the bike trainer 10, tightens the axle clamp adjustment 22, and aligns a chain 104 of the bicycle with one of the sprockets of the cassette 26. In operation, the cassette 26 works with a rear derailleur 108 of the bicycle 100 to provide multiple gear ratios for a user of the bike trainer 10. As can be appreciated the freehub 32 includes a conventional freewheel mechanism that allows a user of the bike trainer 10 to stop pedaling whilst the first pulley 12 is still in motion, which simulates the feel of “coasting” on a moving bicycle. That is, the freewheel mechanism includes a first portion engaged with the first pulley 12 and a second portion engaged with the cassette 26, such that the freewheel mechanism is operative to disengage the first portion from the second portion when the first portion rotates faster than the second portion as would be the situation if the bicycle 100 was moving in a forward direction.
In some embodiments, an adapter (not shown) may be provided to allow various custom or “off the shelf” cassettes to be coupled to the pulley hub 32 and over the freewheel mechanism so that they may be used with the bike trainer 10. Manufacturers of cassettes that may be used with the bike trainer 10 include but are not limited to Shimano, Campagnolo, SRAM, and the like. Further, some embodiments may include “spacers” positionable on the axle 23 and secured by the axle clamp 24 and the axle clamp adjustment 22 to accommodate bicycles having differing spacing between their rear dropouts, such as road bicycles and mountain bicycles. As can be appreciated, the spacers may be also rest freely on the axle 23, may be threaded onto the axle 23, or may otherwise be positioned thereon.
As may best be viewed in
As best viewed in
The bike trainer 10 is supported by a center support member 58, a laterally extending right support member 56 and a laterally extending left support member 60, which are removably coupled to the frame 40. In the embodiment shown, the left support member 60 and the right support member 56 are integrally formed as a single piece, but this is not a requirement. The support members 56, 58, and 60 also include a total of four pads 62 to provide a stable interface between the bike trainer 10 and a supporting surface (e.g., a floor). One of the pads 62 is positioned near each forward end of each of the support members 56, 58, and 60, and one pad is positioned near the rearward intersection of the left support member 60 and the right support member 56. The height of each of the pads 62 relative to the support members 56, 58, and 60 may be adjustable so that the bike trainer 10 may be sturdily supported by an uneven surface without rocking. As can be appreciated, this configuration provides substantial support to the bike trainer 10 and bicycle 100 when a user is operating the bike trainer 10, such that the user remains stable on the bicycle 100 without rocking during use. It should also be appreciated that the number of pads 62 may be varied as well (e.g., three pads, six pads, or the like).
The support members 56, 58, and 60 are coupled to a lower portion 42 of the frame 40 using one or more fasteners such as screws (not shown). As illustrated, when coupled together, the lower portion 42 of the frame 40 and a lower shell 46 form a hollow interior region sized to receive rearward portions of the support members 56, 58, and 60. One or more fasteners, such as screws, may be used to secure the support members 56, 58, and 60 to the lower shell 46 and to the lower portion 42 of the frame 40. Advantageously, by permitting the support member 56, 58, and 60 to be selectively removed from the remainder of the bike trainer 10, the bike trainer 10 may be relocated and/or shipped more efficiently.
In operation, the fan 80 acts as a flywheel to provide resistance as well as inertia to the bike trainer 10. As the fan 80 rotates at a higher speed, the air resistance provided by a plurality of radially extending fan blades 84 provides relatively more resistance to a user of the bike trainer 10. Further, the fan 80 has a suitable weight such that it has a relatively high moment of inertia, thereby storing a large amount of rotational energy. To further increase the inertia provided by the fan 80 as it rotates, a significant portion of the weight of the fan is disposed at its periphery. This is achieved by an outer band 85 that extends circumferentially around the distal ends of each of the fan blades 84. This inertia provided by the fan 80 allows the bike trainer 10 to provide a feel of “coasting” for a user, such that the energy produced by pedaling is not immediately lost after the user stops pedaling. As can be appreciated, this feature of the present disclosure provides a user with a riding experience that is similar to a moving bicycle.
To provide a suitable amount of inertia, the fan 80 may be formed from ductile iron, steel, or any other material or materials having a relatively high toughness and density. Additionally, the fan 80 may have a weight of about 5 to 25 pounds (e.g., 15 pounds). The moment of inertia of the fan 80 about its spinning axis may be about 220 to 260 pound square inches (lb*in2). Further, as shown best in
As best shown in
Additionally, a fan housing 82 may be provided to enclose the fan 80. The fan housing includes a right fan grill 86 and a left fan grill 87. As shown in
The bike trainer 10 shown and described herein permits a user to simulate the feel and ride of his or her own bicycle, thereby providing a quality workout when riding a bicycle in a conventional manner is undesirable (e.g., poor weather, limited space, or the like). As discussed above, the bike trainer 10 provides a these features by creating a suitable amount of resistance to allow users to get an effective workout, and by providing a freewheel and flywheel mechanism to preserve the rotational energy generated by a user by pedaling a bicycle coupled to the bike trainer 10. Further, by providing a substantial support structure, a user of the bike trainer 10 is sturdily supported on his or her bicycle during use.
As shown in
As shown in
As shown in
The communications interface 212 may be any suitable wired or wireless communications interface. In the illustrated embodiment, the communications interface 212 is a wireless interface. The communications interface 212 may enable the controller 204 to communicate with a variety of input and output devices, including the velocity sensor 250. Further, the controller 204 may be operative to connect to or “pair” with one or several other devices or user interfaces simultaneously using any suitable communications technologies.
In some embodiments, the power console unit 200 is operative to save workout data in one or more file formats (e.g., date/time-stamped comma separated values (CSV) files, or other file types). This saved data may be transferred or downloaded to another computer (e.g., a portable computer, a watch, or the like) in a variety of ways, both wired and wireless. For example, in some embodiments workout data may be downloaded to a computer or other device via USB or by a suitable wireless protocol (e.g., ANT+, or other wireless protocols). Further, in some embodiments, the power console unit 200 may also allow users to review workout data and to upload customized training workouts or programs to the console unit.
As shown in
As shown in
The velocity sensor 250 also includes a controller 254 operative to control the operation of the velocity sensor. The controller 254 may be operatively coupled to the switch 258 and a wired or wireless communications interface 262. Like the controller 204, the controller 254 may include one or more processor cores, one or more types of memory, and input/output peripherals. The controller 254 may be application specific or a generally available controller. In general, the controller 254 is operative to receive signals from the switch 258, to determine an instantaneous angular velocity (ωp) of the first pulley 12 (or the angular velocity (ωf) of the fan 80) based on the signals received from the switch, and to send angular velocity measurements to the power console unit 200 wirelessly via the communications interface 262.
The communications interface 262 may be any suitable wired or wireless communications interface. In the illustrated embodiment, the communications interface 262 is a wireless communications interface. The communications interface 262 may enable the controller 254 of the velocity sensor 250 to communicate with a variety of input and output devices, including the power console unit 200. Further, the controller 254 may be operative to connect to or “pair” with one or more other devices or user interfaces simultaneously using any suitable communications technologies.
In operation, the power console unit 200 is configured to receive the angular velocity measurements from the velocity sensor 250 and to calculate the instantaneous output power by inserting the angular velocity measurements into a power equation. The output power may be continuously displayed on the display 208A shown in
The total output power (PTOTAL) of the bike trainer 10 can be represented as the sum of the power due to the resistance of the fan 80 (PR) and the power due to the kinetic energy of the fan (PKE). That is:
P
TOTAL
=P
R
+P
KE (Equation 1)
The power due to the resistance of the fan 80 (PR) comprises a base equation:
P
R
=Aω
f
3
+Bω
f
2
+Cω
f (Equation 2)
where the coefficients A, B, and C are numerical values that may be derived through empirical testing, and Wf is the angular velocity of the fan 80 in radians per second (rad/sec). Thus, the instantaneous PR is a function of the coefficients A, B, and C, and the angular velocity ωf of the fan 80. As discussed above, the angular velocity of the fan 80 is provided to the power console unit 200 by the velocity sensor 250.
The coefficients A and B of Equation 2 account for aerodynamic effects of the air moving over and around the radially extending blades 84 of the fan 80 (see
The power due to the kinetic energy (PKE) of the fan 80 is equal to the change of kinetic energy over a period of time. The power due to kinetic energy (PKE) may be represented by the following equation:
P
KE
=KE
f
−KE
fp (Equation 3)
where KEf is the present measurement of the kinetic energy of the fan 80, and KEfp is the kinetic energy of the fan 80 measured one second before the present measurement (“previous measurement”). Since kinetic energy is equal to one half of the mass moment of inertia (J) times the angular velocity (ωf) squared, the power of the fan 80 due to kinetic energy may be determined by the following equation:
P
KE=(1/2)*J*ωf2−(1/2)*J*ωfp2 (Equation 4)
which may be reduced to:
P
KE=(1/2)*J*(ωf2−ωfp2) (Equation 5)
In Equations 4 and 5, J is the mass moment of inertia of the fan 80, in kg-m2, which is based on the geometry of the fan. The variable Wf is the angular velocity of the fan 80, in rad/sec, at the present time (or latest measurement), and the variable ωfp is the angular velocity of the fan at the previous second. Thus, given the angular velocity measurements of the fan 80 each second, the energy (in Watts) required to maintain the fan at that angular velocity may be calculated.
By inserting Equations 2 and 5 into Equation 1, the following equation for the total output power of a user operating the bike trainer 10 is obtained:
P
TOTAL
=Aω
f
3
+Bω
f
2
+Cω
f+(1/2)*J*(ωf2−ωfp2) (Equation 6)
From Equation 6, it is seen that the total output power is dependent on the angular velocity as provided by the velocity sensor 250, and the coefficients A, B, and C.
The equation for the power due to resistance of the fan 80 (Equation 2) accounts for the power required to turn the fan through the air at a specific set of atmospheric conditions. However, as the air conditions change, the power required to turn the fan changes. To account for these changes in air conditions, the power console unit 200 is operative to automatically modify one or more of the coefficients A, B, and C in the output power equation (Equation 6) to provide a more accurate power equation.
As discussed above, the coefficients A and B account for the aerodynamic effects of the air moving over and around the blades 84 of the fan 80. These constants vary as air temperature, humidity, altitude and/or atmospheric pressure change. To compensate for these variables, the power console unit 200 includes the temperature sensor 216, the humidity sensor 220, and the atmospheric pressure sensor 224 (in some embodiments) coupled to the controller 204 (see
The sensors 216, 220, and 224 may be operative to measure changing atmospheric conditions and to provide these measurements to the controller 204 of the power console unit 200 so that the power equation may be automatically adjusted. In this regard, the accuracy of the power console unit 200 is improved by accounting for various types of atmospheric conditions.
As discussed above, the coefficient C in the power equation accounts for the mechanical drag of the bike trainer 10 due to belt/pulley friction and bearing friction. In general, the coefficient C may vary for each bike trainer 10 so it may be determined for each bike trainer during the manufacturing or installation process. Typically, the coefficient C will not change or will change slowly over time so it may not need to be measured and updated as often as the coefficients A and B. To determine an appropriate value for the coefficient C, a “spin-down” test is performed for each bike trainer 10 at low speeds (e.g., less than about 20 kilometers per hour, or the like). The spin down test comprises measuring the time required for the fan 80 of the bike trainer 10 to decelerate between two fixed low speed fan velocities. Based on the result of this test, an appropriate value for the coefficient C may be determined and stored in a memory of the controller 204 of the power console unit 200.
In some embodiments, the atmospheric pressure may be measured using a spin-down test at relatively high fan velocities (e.g., 40 to 45 kph, or the like). Once the atmospheric pressure has been determined using such a high-velocity spin-down test, one or both of the coefficients A and B may be adjusted appropriately dependent on the determined atmospheric pressure.
The process 300 continues with step 312 wherein information relating to the environmental or operating conditions is received. As discussed above, this information may be provided from a variety of sources at a variety of times. For example, the mechanical drag of a particular bike trainer may be determined during the manufacturing process using the aforementioned low-speed spin-down test so that the coefficient C may be determined and stored. The temperature, humidity, altitude and/or atmospheric pressure may be measured periodically during use using the sensors 216, 220, and 224 (see
Once the power console unit 200 has received information relating to the environmental and operating conditions, the power equation (Equation 6) may be generated or modified by determining the coefficients A, B, and C using the empirically derived relationships between the coefficients and operating conditions, step 316. As can be appreciated, the coefficients of the power equation may be automatically adjusted periodically (e.g., once per second, once per day, or the like) as the operating conditions are changed or updated by the sensors 216, 220, and 224 or input by the user. Further, each of the coefficients may be adjusted independently of the others.
As the user operates the bike trainer 10, the velocity sensor 250 will periodically (e.g., once per second) send measurements indicative of the angular velocity (ωf) of the fan 80 to the power console unit 200, step 320. In some embodiments, the velocity sensor 250 may send measurements of the angular velocity (ωp) of the first pulley 12 rather than of the fan 80. In this case, the power console unit 200 may convert the angular velocity ωp to ωf using the known fixed gear ratio (e.g., 8:1) between the first pulley 12 and the fan 80.
The power console unit 200 may then periodically calculate the instantaneous power output of the bike trainer 10 as the user operates the bike trainer by solving the power equation (Equation 6) using the received angular velocity measurements, step 324. In step 328, the calculated output power may be continuously displayed on the display 208A (see
Exemplary coefficient equations for the bike trainer 10 are provided below. A suitable coefficient equation for the coefficient A may be:
A=((0.348444*P)−H*(0.00252*T−0.020582))/(273.15+T)/1.2*0.00715 (Equation 7)
where P is air pressure, and is related to altitude by the following equation:
P=1026.8−(Altitude in meters)/8 millibars (Equation 8)
(i.e., an air pressure drop of 1 millibar for every 8 meters gain in altitude). H is relative humidity expressed as a decimal (e.g., 0.0 being 0% relative humidity and 1.0 being 100% relative humidity), and T is the temperature in degrees Celsius. The division by 1.2 in Equation 7 is provided to normalize the air density to conditions present on testing day and has units of kg/m3.
A suitable coefficient equation for the coefficient B may be:
((0.0026*T+0.9487)*(−0.0322)) (Equation 9)
As discussed above, the coefficient C is dependent upon the mechanical drag of a particular bike trainer 10, and may be determined using a spin-down test at low speeds. A suitable coefficient equation for the C coefficient may be:
(3.2349*CSD) (Equation 10)
where CSD is a spin-down correction determined by the following equation:
C
SD=(ΔVflywheel/ΔT)/3.343 (Equation 11)
where ΔVflywheel the change of angular velocity of the flywheel in rad/sec and ΔT is the time in seconds for ΔVflywheel to be approximately 71 rad/sec. The 3.343 multiplier is used to normalize Equation 11 to the particular bike trainer 10 that was tested.
As discussed above, embodiments of the present invention utilize a power output equation that models the power due to the resistance of the fan 80 as well as the power due to kinetic energy of the fan. Further, by modifying the power equation periodically to account for environmental and operating conditions, the power console unit 200 is operative to provide a user with very accurate power output measurements. This can be advantageous for users, especially elite athletes, that desire to measure their training level and progress precisely.
The foregoing described embodiments depict different components contained within, or connected with, different other components. It is to be understood that such depicted architectures are merely exemplary, and that in fact many other architectures can be implemented which achieve the same functionality. In a conceptual sense, any arrangement of components to achieve the same functionality is effectively “associated” such that the desired functionality is achieved. Hence, any two components herein combined to achieve a particular functionality can be seen as “associated with” each other such that the desired functionality is achieved, irrespective of architectures or intermedial components. Likewise, any two components so associated can also be viewed as being “operably connected”, or “operably coupled”, to each other to achieve the desired functionality.
While particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that, based upon the teachings herein, changes and modifications may be made without departing from this invention and its broader aspects and, therefore, the appended claims are to encompass within their scope all such changes and modifications as are within the true spirit and scope of this invention.
Furthermore, it is to be understood that the invention is solely defined by the appended claims. It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.).
It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations).
Accordingly, the invention is not limited except as by the appended claims.
