TECHNICAL FIELD
The present disclosure relates to the field of treadmills, and, more particularly, to an omnidirectional treadmill and related methods.
BACKGROUND
An “omnidirectional treadmill” is a device that allows a user to move infinitely on its surface in any direction without moving significantly relative to the surrounding environment, much like a traditional treadmill, except it must actively work to keep you in the center and has an added dimension of movement.
SUMMARY
Generally speaking, an omnidirectional treadmill comprises a treadmill deck assembly comprising a deck, and a first plurality of omniwheels coupled to a periphery of the deck, and a support assembly. The support assembly comprises a base, a second plurality of omniwheels coupled to a periphery of the base and to abut the first plurality of omniwheels, and a plurality of motors coupled to the second plurality of omniwheels. The omnidirectional treadmill comprises a tread surrounding the treadmill deck assembly and being between the first plurality of omniwheels and the second plurality of omniwheels. The first plurality of omniwheels and the second plurality of omniwheels are configured to pinch the tread. The omnidirectional treadmill also includes a controller coupled to the plurality of motors and configured to control movement of the plurality of motors to drive the tread.
Also, the omnidirectional treadmill may include a fabric management assembly coupled to the tread below the treadmill deck assembly. The fabric management assembly may comprise a plurality of rings adjacent to the tread, the plurality of rings having different diameters. The fabric management assembly may also comprise a tensioning device within the tread and configured to tension the tread against the plurality of rings. In particular, the tensioning device may comprise an annular weight.
The treadmill deck assembly may comprise a first plurality of bearing devices coupled to the periphery of the deck, and the support assembly may comprise a second plurality of bearing devices coupled to the periphery of the base. The tread may be between the first plurality of bearing devices and the second plurality of bearing devices. Each of the first plurality of bearing devices may comprise a first transfer bearing facing away from the deck. Each of the second plurality of bearing devices may comprise a set of second transfer bearings facing inwardly and being radially spaced from each other. Each respective first transfer bearing may sit onto and between the set of second transfer bearings.
Another aspect is directed to a method of making an omnidirectional treadmill. The method comprises providing a treadmill deck assembly comprising a deck, and a first plurality of omniwheels coupled to a periphery of the deck, and positioning a support assembly. The support assembly comprises a base, a second plurality of omniwheels coupled to a periphery of the base and to abut the first plurality of omniwheels, and a plurality of motors coupled to the second plurality of omniwheels. The method also includes positioning the treadmill deck assembly within a tread, the treadmill deck assembly being between the first plurality of omniwheels and the second plurality of omniwheels. The first plurality of omniwheels and the second plurality of omniwheels are configured to pinch the tread. The method may further comprise coupling a controller to the plurality of motors and configured to control movement of the plurality of motors to drive the tread.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side view of an omnidirectional treadmill, according to a third embodiment of the present disclosure.
FIG. 2 is a perspective view of the omnidirectional treadmill from FIG. 1.
FIG. 3 is a partial cross-sectional view of the omnidirectional treadmill from FIG. 1 along line 3-3.
FIG. 4 is a cross-sectional view of the omnidirectional treadmill from FIG. 1 along line 3-3.
FIG. 5 is a top plan view of the support assembly from the omnidirectional treadmill from FIG. 1.
FIG. 6 is a perspective view of the support assembly from the omnidirectional treadmill from FIG. 1.
FIG. 7 is a side view of the treadmill deck assembly being inserted into the tread from the omnidirectional treadmill from FIG. 1.
FIG. 8 is a side view of the first and second bearing devices from the omnidirectional treadmill from FIG. 1.
FIG. 9 is a top plan view of the second bearing device from the omnidirectional treadmill from FIG. 1.
FIG. 10 is a cutaway view of the transfer bearing from the omnidirectional treadmill from FIG. 1.
FIG. 11 is a perspective view of the omniwheel from the omnidirectional treadmill from FIG. 1.
DETAILED DESCRIPTION
The present disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which several embodiments of the invention are shown. This present disclosure may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present disclosure to those skilled in the art. Like numbers refer to like elements throughout, and base 100 reference numerals are used to indicate similar elements in alternative embodiments.
The present disclosure utilizes a device called an “omniwheel” depicted in FIG. 11. An omniwheel is a wheel with smaller wheels 332a-332f, 333a-333f around its circumference to allow for smooth movement in multiple directions on the edge of the wheel.
The present disclosure utilizes a device called a “ball transfer bearing” depicted in FIG. 10. A ball transfer bearing is an omnidirectional load-bearing spherical ball mounted inside a restraining fixture.
Generally speaking, an omnidirectional treadmill comprises a continuous sphere of fabric or a similarly thin material, called the “Tread”, which encloses a sturdy platform. This platform may have a plurality of inner omniwheels installed along its edge. A support assembly is located outside of the fabric and underneath the platform which may include a system of vertically aligned bearing devices, both inside and outside of the tread, used as a method to support the weight of the platform without inhibiting the movement of the tread. The support assembly includes a plurality of motors which drive omniwheels that are each vertically aligned underneath each of the inner omniwheels such that the tread is pinched between the two sets of omniwheels, allowing the motors to pull the tread around.
Additionally, the omnidirectional treadmill may include a fabric management assembly coupled to the tread below the treadmill deck assembly. The fabric management assembly may comprise a plurality of rings with varying diameters, which the tread is guided through, using the rings as a three-dimensional pulley system. The fabric management assembly may also comprise a tensioning device within the tread and configured to tension the tread against the plurality of rings. In particular, the tensioning device may comprise an annular weight.
Another aspect is directed to an electronic system which could detect forces applied to the tread in order to predict a user's movement. This detected information could be sent to speed controllers to control the motors such that the Tread moves to keep the user centered on the platform.
A simplified cross-sectional view of the omnidirectional treadmill 300 can be seen in FIG. 4 which will now be used to describe the present disclosure on a two-dimensional level with reference to the construction of a conventional treadmill. In FIG. 4, a treadmill belt 314 is wrapped around a treadmill platform 302 with a wheel attached at either end of the deck 303a, 303c. The treadmill belt is put through a pulley-like system with a heavy, round object 320 hanging in the belt, utilizing the weight of this object to pull the belt under tension. Instead of connecting a motor directly to the inner wheels that are attached to the treadmill platform, a separate set of wheels 307a, 307c are connected to motors and pressed up underneath the inner wheels 303a, 303c, pinching the treadmill belt 314 between the inner wheels and the motor driven ones. Now when the motor driven wheels spin 307a, 307c, the inner wheels 303a, 303c will be caused to spin, similarly to how gears spin each other, but with friction being used to couple the wheels instead of gear teeth. The spinning of the wheels will now cause the treadmill belt 314 to be pulled over the surface, thus allowing a user to walk on the belt and use this device as a treadmill.
That two-dimensional explanation would be an unnecessarily complicated design if this were a conventional treadmill, however, due to the added dimension of movement required by an omnidirectional treadmill, these design choices become necessary. To transform this two-dimensional design into the three-dimensional one that is the subject of this patent, the components will need to be swapped out for their three-dimensional counterparts, starting with the treadmill belt 314. The continuous circular strip of thin material that is used as a walkable moving surface on a conventional treadmill is replaced by a continuous sphere of thin material which will hereafter be referred to as the “tread” 314. Due to the tread now needing to completely enclose the treadmill platform 302 in order to be a continuous sphere, the rectangular treadmill platform can no longer be directly supported by the ground and is instead replaced with a completely disjointed circular or polygonal platform which will hereafter be referred to as the “treadmill deck” 302. The treadmill deck is supported indirectly through the through the tread 314 by a system of ball transfer bearings 322 (FIG. 10) which allow the tread 314 to pass freely through them while still providing support (FIGS. 8-9). The two-dimensional pulley-like system is replaced by a ring which may compose heavy bearing balls 320 that hang in the bottom of the tread, utilizing their weight to pull the tread under tension and through a series of smooth hoops (FIG. 1). This system will be henceforth referred to as the “fabric management system”. The last, and most important three-dimensional part is the replacement for the two-dimensional wheels, which is called the “omniwheel” 303,307, and is part of the motor control system.
An omniwheel (FIG. 11) is a wheel with smaller wheels, called rollers, placed around its circumference in such a way as to allow them to rotate freely in a direction perpendicular to the main wheel. By replacing all other components with their three-dimensional counterparts, and by using omniwheels instead of traditional wheels, you can essentially have two pairs of motor driven 307a-307d and inner omniwheels 303a-303d each set up exactly like is shown in FIG. 4, but with each pair of motor driven and inner omniwheels being perpendicular to each other. This way, when one pair of motor driven omniwheels 307a, 307c pulls the tread towards itself, the rollers along the circumference of the other set of omniwheels 307b, 307d which are set up perpendicular to it will allow the tread 314 to smoothly glide between the motor driven 307b, 307d and inner omniwheels 303b, 303d of the second set without turning the motor shafts of the second set at all. This allows the two sets 307a, 307c & 307b, 307d to act completely independently of each other and allows them to both operate at the same time. If only one set of motors is operating, the tread will move directly in-line with that set of motors. If both sets of motors are operating at the exact same speed, the tread will move at an angle that is perfectly in-between the motors. If both sets of motors are operating at different speeds, the tread will move at an angle based on the summed vector of both motor sets' speed and direction. A massive advantage to having a motor in this configuration is that there can be a very small number of motors 310a-310d, and those motors can be as large as desired due to the relatively detached nature of their position. The small number of motors allows the cost of the treadmill to be kept reasonably low for consumers, and allows for the ability to have large motors, which lets the treadmill make quick changes in direction while still having a high top speed and high enough torque to move a human. Insufficient response time to changes in movement, as well as high costs are two of the main factors that have prevented any other omnidirectional treadmill 300 design from becoming viable for any practical use, even for the few that do work.
The design of the “tread” 314 will now be described in detail. The tread is made from a fabric or a similarly thin material which is manufactured into a spherical or spheroidal shape. The tread completely encompasses the treadmill deck such that a layer of fabric completely isolates the deck 302 from the rest of the treadmill assembly. The tread is held in tension by a fabric management system 316 so that it can be pulled around by the motor driven omniwheels 307a-307d without slacking in the tread causing issues similar to those encountered by trying to push a rope through two wheels. The tread 314 being in tension also ensures that the surface which the user walks on doesn't feel stretchy and makes sure that the surface only moves when the motors move. The tread can be manufactured in many ways, but it will behave more uniformly during operation the closer it is in shape to a perfect sphere and therefore be less likely to cause problems. The tread in FIG. 7 is sewn into the same shape as a soccer ball. It may seem like the fabric management system 316 could be circumvented by using an elastic material and simply having the tread be made small enough to where it naturally stretches over the treadmill deck to provide tension. Unfortunately, doing this causes the widest part of the tread, the maximum diameter, to be centered around the treadmill deck 302, which leaves an entire hemisphere of the tread that needs to be flattened. Unless you could stretch the tread around the deck with an absurd amount of force, this will become a problem and make the platform stretchier in the middle than it is towards the sides. For every doubling of the diameter of the tread, it becomes over 10× easier to flatten, so making the tread fit loosely over the treadmill deck makes it take much less force to have a suitable surface to walk on. Another interesting concept with the tread 314 is that it could be made from a composite material, such as having a top layer of fabric or rubber for the user to walk on, and a bottom layer of a very thin PTFE (Teflon) sheet. That would reduce friction caused from a user's weight and wouldn't affect how the treadmill feels to walk on.
The design of the treadmill deck 302 will now be described in detail with reference to FIGS. 4 & 7-9. The treadmill deck is a platform capable of supporting the weight of the user, and has a hard, flat and smooth surface to minimize friction while in use. The treadmill deck can be in the shape of a regular polygon or a circle and has a multiplicity of omniwheels lining the edges 303a-303d. The treadmill deck is located inside of the tread 314 (FIG. 7); therefore, a circular treadmill deck is ideal for allowing for the most uniform and consistent behavior of the tread in operation. The omniwheels 303a-303d attached along the edges of the treadmill deck 302 are free rolling and distributed in a regular interval. To support the weight of the treadmill deck and to hold it stable, ball transfer bearings 322 are fixed to the underside of the deck at multiple points, with an accompanying set of ball transfer bearings located outside of the tread 314 and aligned underneath each inner one so that the ones fixed to the platform can be held in place and supported by the ones outside of the tread (FIGS. 8-9).
The “fabric management system” will now be described in detail with reference to FIGS. 1, 4, & 7. The fabric management system consists of a series of hoops 317a-317c with heavy bearing balls 320 using their weight to guide the “tread” 314 fabric through that system of rings. A simple alternative to the ring of bearing balls 320 could be to just use a single heavy and smooth ring, or to use the weight of the platform to push a ring into the bottom of the fabric to hold it in tension. This system has two purposes: To pull the tread in tension, and to minimize the vertical size of the omnidirectional treadmill assembly. Bearing balls 320 are inserted into the tread along with the treadmill deck (FIG. 7), with the weight of the bearing balls being used to pull the tread 302 under tension. This means that tension can be increased by increasing the weight of the balls. Technically, the treadmill could work just fine without any of the rings, however, there would need to be a lot of vertical space underneath the treadmill deck to allow the bearing balls to hang loose in the fabric. For that reason, a small ring 317a is added close to the bottom of the treadmill deck, and the bearing balls are put through that ring to lead the tread through it, choking the tread and causing a lot of its surface area to be spread out horizontally instead of vertically (FIG. 1). A second exterior ring 317c can be seen in FIG. 4 which is significantly larger than the ring used to choke the tread. The bearing balls are placed hanging around this larger ring, which spreads out the tread material horizontally even more than before, therefore allowing the treadmill to keep a low profile while still using the weighted ball method for tensioning the tread. A third ring 317b can be added to the inside of the tread (FIG. 4) to prevent the fabric from rubbing against itself around the large outer ring, thus reducing friction. The third ring 317b needs to be supported by the bottom of the treadmill deck 302, with its supports threaded through the smallest ring from within the tread.
The lateral force detection and motor control system will now be described in detail with reference to FIG. 3. The motor driven omniwheels 307a-307d are constantly friction locked to the tread, this means that the horizontal component of any force imparted on the surface of the treadmill by the user's legs when trying to move will cause the motor driven omniwheels 307a-307d to try to spin, therefore causing the shaft of the motor 310a-310d to try to spin. When the shaft of an electric motor is spun by an external force, it acts like a generator, inducing a voltage in the wires that are normally used to control the motor via external power. This effect is the same one that allows electric cars to regenerate battery when using their motors to slow down instead of the brakes. The induced voltage from the shaft spinning is proportional to the magnitude of the horizontal force applied to the tread and can be detected. The shaft of each electric motor 310a-310d is attached to an omniwheel 307a-307d, which means that any movement of the tread 314 in a direction perpendicular to the omniwheel will not cause the shaft of that motor to spin at all. This is extremely useful because if you know the magnitude of the induced voltage in the motors, and you know which motors are being spun, you can calculate the exact magnitude and direction of the force being applied laterally across the surface of the treadmill. This lateral force is the “equal and opposite reaction” force caused by a user trying to walk in any direction, which means that this data can be used to detect the user's intended movement and to control the omnidirectional treadmill accordingly to keep the user positioned in the center.
A simplified block diagram of the lateral force detection system can be seen in FIG. 3. The primary purpose of this system is to detect the force applied to the moving surface of the treadmill 314 (tread) when the user tries to move, and to have the tread move accordingly to keep the user centered. The voltage at the terminals of the electric motor 310a is monitored by a voltmeter, this information is then sent to a processor 315, where the expected voltage at the motor terminals is compared to the actual reading seen by the voltmeter. Any major discrepancy between the expected and actual voltages can be attributed to forces caused by the user. Using the difference between the expected and actual voltage at the motor terminals of each motor driven omniwheel, the force and intended direction of any user movement can be extrapolated. Using this data, the processor can direct the electronic speed controller of each motor to cause the tread to move in such a way as to keep the user of the treadmill centered on the treadmill deck despite their attempt to move.
The lateral force detection system allows for extremely low latency detection of a user's intended movement, getting as close as possible to reading their mind without actually doing it. When paired with quick, high torque motors, the lateral force detection system enables the omnidirectional treadmill to keep up with a user who is running and quickly changing directions.
All of the aforementioned elements that make up the present disclosure come together to make a reasonably cheap, and uniquely effective omnidirectional treadmill, intended to be sold at a large scale to consumers for many purposes, including for use with Virtual Reality or as a physical therapy device.
Referring now to FIGS. 1-7, another embodiment of an omnidirectional treadmill 300 is now described. The omnidirectional treadmill 300 includes a treadmill deck assembly 301 comprising a deck 302, a first plurality of omniwheels 303a-303b coupled to a periphery of the deck, and a first plurality of bearing devices 304 coupled to the periphery of the deck.
Here, the deck 302 is illustratively square-shaped, but in other embodiments, the deck may take on other polygonal shapes. Although only two of the first plurality of omniwheels 303a-303b are depicted, there are at least four in the first plurality of omniwheels 303a-303b, illustratively equally spaced at the four corners of the deck 302 (i.e., radially spaced at) 90°.
The omnidirectional treadmill 300 includes a support assembly 305. The support assembly 305 comprises a base 306, a second plurality of omniwheels 307a-307d coupled to a periphery of the base and to abut the first plurality of omniwheels 303a-303b, a plurality of motors 310a-310d coupled to the second plurality of omniwheels, and a second plurality of bearing devices 311a-311d coupled to the periphery of the base. As perhaps best seen in FIG. 5, the base 306 is illustratively circle-shaped.
The support assembly 305 illustratively comprises a plurality or vertical arms 312a-312d extending upward from the base 306 and respectively carrying the second plurality of bearing devices 311a-311d, and a plurality of platforms 313a-313d on the from the base 306 carrying the plurality of motors 310a-310d and the second plurality of omniwheels 307a-307d.
The omnidirectional treadmill 300 comprises a tread 314 surrounding the treadmill deck assembly 301 and being between the first plurality of omniwheels 303a-303b and the second plurality of omniwheels 307a-307d. As perhaps best seen in FIG. 7, the tread 314 comprises a polygonal sphere. In other embodiments, the tread 314 may comprise other spheroid shapes.
As perhaps best seen in FIG. 3, the first plurality of omniwheels 303a-303b and the second plurality of omniwheels 307a-307b are configured to pinch the tread 314 and drive it a direction parallel to the rotational axis. The omnidirectional treadmill 300 also includes a controller 315 coupled to the plurality of motors 310a-310d and configured to control movement of the plurality of motors to drive the tread 314. In the illustrated embodiment, the controller 315 illustratively comprises a processing unit 318a, a voltmeter 318b coupled to the processing unit, and an electronic speed controller 318c coupled to the processing unit.
Referring to FIG. 4, the omnidirectional treadmill 300 illustratively comprises a fabric management assembly 316 coupled to the tread 314 below the treadmill deck assembly 301. The fabric management assembly 316 comprises a plurality of rings 317a-317c of different diameter and being adjacent to the tread 314. In particular, the first ring 317a is outside the tread 314, and the second ring 317b has a larger diameter than the first ring and is within the tread. The third ring 317c has a diameter smaller than the second ring 317b, but larger than the first ring 317a and is outside the tread 314. As will be appreciated, the plurality of rings 317a-317c is used to elongate the path of travel of the tread 314 without increasing the vertical depth of the fabric management assembly 316.
The fabric management assembly 316 illustratively comprises a tensioning device 320 within the tread 314 and configured to tension the tread against the plurality of rings 317a-317c. In particular, the tensioning device 320 comprises an annular weight, for example, the illustrated ring of ball bearings (FIG. 7). In other embodiments, the tensioning device 320 may comprise a large gauge ring. The tensioning device 320 provides a downward pressure on the tread 314, which maintains a taut and flat surface on the deck 302.
Referring now additionally to FIGS. 8-10, the tread 314 travels between the first plurality of bearing devices 304 and the second plurality of bearing devices 311a-311d. Each of the first plurality of bearing devices 304 comprises a first transfer bearing 321 facing away from the deck 302. In particular, the transfer bearing 321 faces substantially orthogonal (i.e., ±15° from 90°) to the deck 302. Although only one of the first plurality of bearing devices 304 is shown for drawing clarity, the other three of the first plurality of bearing devices 304 are aligned with the second plurality of bearing devices 311a-311d.
Each of the second plurality of bearing devices 311a-311d comprises a set of second transfer bearings 322a-322c facing inwardly and being radially spaced from each other. Each respective first transfer bearing 321 sits onto and between the set of second transfer bearings 322a-322c. In the illustrated embodiment, the set of second transfer bearings 322a-322c are arranged in a triangular pattern, and are radially spaced apart 120°. The respective first transfer bearing 321 sits centrally within the set of second transfer bearings 322a-322c to tightly control the tread 314.
Each of the first transfer bearings 321 and the second transfer bearings 322a-322c comprises a housing 323, a threaded shank 324 coupled to the housing, a first ball bearing 325 being centrally located and aligned with the threaded shank, second ball bearings 326a-326d between the housing and the first ball bearing, and third ball bearings 327a-327n annularly surrounding the first ball bearing.
Referring now additionally to FIG. 11, each of the first plurality of omniwheels 303a-303b and the second plurality of omniwheels 307a-307d comprises a housing 330 defining an axial passageway 331. As will be appreciated, the omniwheel 303a-303b, 307a-307d rotates about the axial passageway 331. The omniwheel 303a-303b, 307a-307d illustratively comprises first plurality of outer wheels 332a-332f carried on the periphery of the housing 330, and a second plurality of outer wheels 333a-333f (smaller than the first outer wheels) interdigitated within the first plurality of outer wheels. Each of the first plurality of outer wheels 332a-332f and the second plurality of outer wheels 333a-333f rotate in radial direction that is orthogonal to the rotation about the axial passageway 331.
Another aspect is directed to a method of making an omnidirectional treadmill 300. The method comprises providing a treadmill deck assembly 301 comprising a deck 302, and a first plurality of omniwheels 303a-303b coupled to a periphery of the deck, and positioning a support assembly 305. The support assembly 305 comprises a base 306, a second plurality of omniwheels 307a-307d coupled to a periphery of the base and to abut the first plurality of omniwheels 303a-303b, and a plurality of motors 310a-310d coupled to the second plurality of omniwheels.
As perhaps best seen in FIG. 7, the method also includes positioning the treadmill deck assembly 301 within a tread 314, the treadmill deck assembly being between the first plurality of omniwheels 303a-303b and the second plurality of omniwheels 307a-307d. In the illustrated embodiment, the tread 314 has a closable opening 334 for access. The first plurality of omniwheels 303a-303b and the second plurality of omniwheels 307a-307d are configured to pinch the tread 314. The method may further comprise coupling a controller 315 to the plurality of motors 310a-310d and configured to control movement of the plurality of motors to drive the tread 314.
As will be appreciated, the features from the omnidirectional treadmill 100 and the omnidirectional treadmill 300 may be combined.
Many modifications and other embodiments of the present disclosure will come to the mind of one skilled in the art having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is understood that the present disclosure is not to be limited to the specific embodiments disclosed, and that modifications and embodiments are intended to be included within the scope of the appended claims.
Patent Application
20240165459
