Virtual reality footwear locomotion system

Abstract

A footwear assembly for use in a virtual reality environment comprising a front platform portion having an upper surface adapted and configured for supporting and releasably retaining the forward part of a user's foot and a rear platform portion having an upper surface adapted and configured for supporting and releasably retaining a rear part of the user's foot, the front and rear platform portions being joined by a transverse hinge so that the platform portions can pivot relative to one another to accommodate flexing of the user's foot, each platform portion having mounted under a lower surface thereof at least one drive motor, each drive motor driving a continuous belt, and two continuous belts on each platform portion being arranged substantially in parallel, one located to each side of the platform portion, the drive motor or motors and continuous belts of the front platform portion being mounted to a front drive module and the drive motor or motors and continuous belts of the rear platform portion mounted to a rear drive module, the drive modules being mounted beneath their respective platform portions so each drive module may rotate in the horizontal plane relative to the platform portion it is mounted beneath.

Claims

1. A footwear assembly for use in a virtual reality environment comprising a front platform portion having an upper surface adapted and configured for supporting and releasably retaining the forward part of a user's foot and a rear platform portion having an upper surface adapted and configured for supporting and releasably retaining a rear part of the user's foot, the front and rear platform portions being joined by a transverse hinge so that the platform portions can pivot relative to one another in the longitudinal plane to accommodate flexing of the user's foot, in which each platform portion has mounted to a lower surface thereof at least one drive motor, each drive motor driving a continuous belt, and two continuous belts on each platform portion being arranged substantially in parallel, one located to each side of the platform portion, and in which the drive motor or motors and continuous belts of the front platform portion are mounted to a front drive module and the drive motor or motors and continuous belts of the rear platform portion are mounted to a rear drive module, the drive modules being mounted beneath their respective platform portions so each drive module may rotate in the horizontal plane relative to the platform portion it is mounted beneath.

2. The footwear assembly as claimed in claim 1, further comprising a front turn motor adapted to selectively rotate the front drive module relative to the front platform portion and a rear turn motor adapted to selectively rotate the rear drive module relative to the rear platform portion.

3. The footwear assembly as claimed in claim 1, in which the rotational movement of the drive modules is constrained to a maximum of 90? in either direction from the longitudinal plane.

4. The footwear assembly as claimed in claim 1, in which the turn motors are coupled to a position sensor.

5. The footwear assembly as claimed in claim 1, in which the turn motors are adapted to drive the two drive modules to rotate so that they remain aligned and parallel as they rotate.

6. The foot wear assembly as claimed in claim 1, in which at least one motor on each platform portion is located within a continuous belt.

7. The footwear assembly as claimed in claim 1, in which the continuous belts on each drive module are of different lengths.

8. The footwear assembly as claimed in claim 7, in which the shorter continuous track under the front platform portion is aligned longitudinally on the same side of the front platform portion as the longer continuous belts under the rear platform portion, and vice versa.

9. The footwear assembly as claimed in claim 1, in which each continuous belt extends between at least one drive wheel having axial ribs and at least one pulley wheel having axial ribs, in which an inner surface of each continuous belt has transverse ribs which are complementary to the ribs on the drive wheel and pulley wheel, and in which the inner surface of the continuous belt has a longitudinal rib extending longitudinally over substantially the entire inner surface of the belt.

10. The footwear assembly according to claim 9, in which circumferential channels are provided in the drive wheel and the pulley wheel, the longitudinal rib being located and configured so as to fit within these channels.

11. The footwear assembly according to claim 10, in which the or each drive wheel and/or the or each pulley wheel is formed of a pair of separate, axially-spaced ribbed wheels, the circumferential channels being provided by the axial spacing of the or each pair of wheels.

12. The footwear assembly as claimed in claim 10, in which the transverse size of the longitudinal rib is less than the axial size of the circumferential channels.

13. A system for use in a virtual reality environment comprising a pair of footwear assemblies as claimed in claim 1, each footwear assembly comprising a transmitter/receiver for transferring data between assemblies and/or between the assemblies and an external VR environment computer.

14. The system according to claim 13 which is adapted to calculate a correction vector representing the distance and direction between the actual coordinate of the centre of the user's body and the origin (starting position) coordinate at least once for every stride (or single step) made by each foot.

15. The system according to claim 14 which is adapted to utilise the correction vector and the actual heading of each VR footwear assembly to calculate a rotation angle of each drive module and to adjust the speed of the drive motors, to gradually return the user to the user's original starting position.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The invention will now be described by way of example and with reference to the accompanying figures, in which;

[0024] FIGS. 1(a) and 1(b) illustrate the operation of a VR environment locomotion system;

[0025] FIG. 2 is a perspective view of a first embodiment of a VR footwear assembly in accordance with the present invention;

[0026] FIGS. 3(a), 3(b) and 3(c) are bottom views of the footwear assembly of FIG. 2 in different states of rotational operation;

[0027] FIG. 4 is a bottom view of the footwear assembly of FIG. 2 with belts removed;

[0028] FIG. 5 is a side elevation schematic view illustrating how the footwear assembly flexes during walking;

[0029] FIGS. 6, 6b and 6c are perspective views of the front end of the footwear assembly of FIG. 2, with the front platform removed;

[0030] FIG. 7 is a perspective view of a drive belt;

[0031] FIGS. 8a and 8b are bottom views of a second embodiment of a VR footwear assembly in accordance with the invention, and

[0032] FIG. 9 is a bottom schematic view of an alternative arrangement of a drive module for alternative embodiments of VR footwear assemblies in accordance with the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] The present invention is concerned with products for Virtual Reality (VR) that aim to solve one of the biggest problems with current technology: that is natural and unrestricted Walking in VR. Generally, these products are known as VR locomotion systems. Current VR technology limits the user to the confines of a small clear area within their homes, usually a living-room or office. The user can take a few steps but will soon reach the boundary of their play area, this is often described as immersion breaking and is an annoyance to the user in what is otherwise a great experience. The challenge is to create a technological solution that can allow a user to walk normally, as well as stopping, turning etc, but prevent the user from physically moving outside a small area (?1.1?1.1 m). When combined with a VR headset, the user will experience change in speed and direction within a virtual environment. Some known VR locomotion systems only provide forwards/backwards movement; the present invention is capable of omni-directional movement and positional correction.

[0034] FIG. 1a shows in plan view how a VR locomotion system operates. A user starts with their feet in or attached to VR footwear assemblies A and B in the centre of the play area 2, inside a protective boundary provided by a safety barrier 4. No special floor type is required for the device to function correctly, although a protective floor mat may be recommended in certain circumstances. While the footwear assemblies are unpowered or in standby mode, the user can walk as normal; the VR footwear assemblies will not roll or move. When ready the user activates the VR footwear assemblies using an in-game menu stored in the VR environment external computer 40 (the menu is displayed on a screen inside the VR headset worn by the user (not shown) which is visible to the user), or via a switch on a handheld controller (not shown) operated by the user. The user then starts walking in a normal way, by lifting and placing one foot forward. If the user simply raises the foot and places it back down without covering a distance, no movement will occur. When the user moves position such as by walking, the actual movement is sensed; using sensors and motors, the user's speed is matched and the inverse movement is performed by the VR footwear assemblies with very low latency to avoid motion sickness. The user can gradually stop at any time when both feet are on the ground, or other conditions are met such as when the distance travelled has been matched by the VR footwear assemblies. The user can also command a safe stop by using a stop button in the in-game menu (usually always present in view), or a physical stop button on the user's handheld controller. Additionally or alternatively there could be a voice-operated stop/start feature.

[0035] After activating the system and after a period of movement by the user (several seconds or minutes, for example), the user may have stopped, changed direction and started walking again, or taken side steps. Over time, this will cause the user to drift away from the centre of the play area, as shown in FIG. 1b. The system must be capable of making corrections to the user's actual physical location, so as to return the user to the centre of the play area 2. As shown in FIG. 1b, the correction vector shown by the arrow AA is applied to return the footwear assemblies to their starting position. Depending on the heading/direction of the user, correctional movements may be lateral (side-ways), or adjustments to the forward walking speed (faster/slower), or a combination of these. Any lateral movements should be significantly slower than the forward/backwards movement of the user (which typically is up to 1.2 m/s), and the acceleration/deceleration should also be gradual; this is to avoid the user feeling the lateral compensatory movements, which may lead to a feeling of instability, and/or to motion sickness.

Outline Operation of the VR Footwear Assemblies in the Locomotion System

[0036] As the user walks in the forward direction, when either of the VR footwear assemblies is lifted off the ground, the opposite VR footwear assembly performs the inverse movement. High torque Brushless DC (BLDC) Motors provide a low latency response rate and PID control ensures the desired speed is achieved rapidly as load changes. Both VR footwear assemblies communicate wirelessly using a radio link such as Bluetooth, Wi-Fi, or generic packet radio for digital transmission. This is configured to relay a constant stream of data between each VR footwear assembly and a central controller, which also connects to a computer 40 (see FIGS. 1a and 1b). Custom C++ Windows drivers interface with the SteamVR Input API, which allows the speed and direction data to be used in VR games and applications. Each VR footwear assembly takes measurements from a number of sensors, that allow for accurate and repeatable measurements of x & y distance moved on the play area surface 2 from the start position and of the angular direction of each foot. These sensors are designed to function regardless of whether the VR footwear assembly is on the floor or raised in the air while the user walks.

[0037] To provide compensatory movements in all directions, not just forwards/backwards, each VR footwear assembly has two motor drive modules (front and rear) which independently rotate 180?, or +90? to ?90? around a centre position. Rotating these drive modules allows lateral (sideways) movement to occur. The magnitude of the lateral movement depends on the angle at which the two drive modules are rotated, for example +/?90? would result in full sideways movement and zero forward movement, whereas +5? would result in substantial forwards/backwards movement while at the same time a small lateral movement. The resulting vector of distance and direction depends on the speed of drive motors and drive module angle, which is determined by a control system for walking and positional correction. This closed loop control system receives inputs from number of sensors, including but not limited to optical, magnetic, MEMSs accelerometers, magnetometers and gyroscopes. The control system outputs signals to control drive motors and turn motors, as well as speed and direction data which is sent to the VR environment computer.

[0038] In addition to the BLDC motors, there are also turn motors embedded within the central part of each drive module that provide the rotation through a set of gears. The turn motors may be stepper motors or geared DC motors (also known as servos). The geared attachment mechanism allows wires to pass through from the rotating drive module to the electronics housing in the middle section of each VR footwear assembly. There is also a position feedback sensor coupled to the rotation motors either directly or by a gear, which allows measurement and precise control of the rotation angle. The absolute rotation angle can be determined, allowing the centre position (0?) to be found and the correct position to be verified during operation.

[0039] Each VR footwear assembly tracks its own location on a two dimensional surface (environment floor) using optical sensors. No tracking sensor devices external to the VR footwear assemblies are required in order to track the position of the VR footwear assemblies. Sensors detect when each VR footwear is lifted off the surface, by means of optical sensors, acceleration sensors or mechanical contacts switches. The speed of each drive motor is measured using magnetic or optical based sensors attached or integrated into each motor. The surface tracking is based on a relative coordinate system, where the centre of the user's play area is the origin (e.g. 0,0) and may be determined by the starting position or otherwise configured by the VR environment computer. The user's actual position and direction (or heading) is determined from sensors on each VR footwear assembly and transmitted between each VR footwear assembly, and/or to an external processing device or VR environment computer.

[0040] The external processing device or VR environment computer calculates a correction vector at least once for every stride (or single step) made by each foot. This correction vector represents the distance and direction between the actual coordinate of the user's body centre and the origin (starting position) coordinate. The correction vector and the actual heading of each VR footwear assembly are used to calculate the rotation angle of each drive module and to adjust the speed of the drive motors (faster/slower than user's actual walking speed) in order to correct the user's position over time.

Embodiments of the Invention

[0041] FIG. 2 shows a schematic view of an embodiment of a footwear assembly 10 in accordance with this invention. It is sized and configured to receive a human foot, with a rear end 12 provided with a heel cup or guard 14, and a front end 16; the footwear assembly 10 has a flexible upper platform in two parts, a rear platform 18 towards the rear end 12 and a front platform 20 towards the front end 16. There is a transverse hinge 22 (shown more clearly in FIGS. 5 and 6), the arrangement being such that the rear platform 18 and heel guard 14 are adapted to receive the rear part of a human foot and the heel, respectively, while the front platform 20 is adapted to receive the front part of the foot, with the hinge 22 being located so that the footwear assembly can hinge at the ball of the foot, where the human foot typically flexes when walking. Brackets 24 are provided for straps or the like (not shown) to pass over the foot to hold the foot firmly in place on the platforms. The heel guard 14 may be adjustable relative to the rear end 12 so as to accommodate feet of different sizes. In use when a user is wearing the footwear assemblies and standing stationary, the two platforms 18, 20 are substantially horizontal.

[0042] Beneath the flexible platforms 18, 20 is a rigid chassis 26, which bends at the transverse hinge 22 and to which are mounted two independently rotatable drive modules, a rear drive module 28 and a front drive module 30. Each drive module 28, 30 has a rigid drive frame 28a (see FIG. 3a), 30a, a drive frame cover 28b, 30b, and on its lower surface two drive belts, described below in relation to FIG. 3. FIG. 2 shows the front and rear drive modules 30, 28 both rotated to the right (relative to the front end 16) by the same amount (however it should be appreciated that the directions and amounts of rotation could differ for some applications or to compensate for some kinds of movement.

[0043] Referring now to FIGS. 3a, 3b and 3c, these all show the underside of the footwear assembly with the drive modules in different rotational positions, but all show the same main elements. Each drive frame has two continuous drive belts, one long one 32a and one shorter one 32b aligned substantially parallel to one another on each drive module; each belt extends in a continuous fashion around a drive wheel 36 and a pulley wheel 38 (shown in FIGS. 4 and 5), the drive wheels 36 being driven by a motor 34 coaxially aligned therewith so as to allow the drive belts to provide movement in a similar manner to a tank track or caterpillar track. The shorter drive belt 32b permits the drive motor 34 for that belt to be nested inside the longer drive belt 32a, making for a more compact arrangement in all three planes, allowing the height of the footwear assembly to be minimised. The drive wheels 36 are preferably located towards the centre of the footwear assembly 10; this places the pulley wheels 38 at the extreme front and rear ends of the footwear assembly, and is preferred because the pulley wheels are designed to handle a greater load (the maximum load on the drive wheels is limited by the maximum radial load on the motor shaft; the pulley wheels can handle a greater load due to multiple larger bearings with higher load ratings). Any impact suffered by the footwear assembly through walking is most likely to occur at the front and rear ends, and if damaged by such an impact the pulley wheels 38 are replaceable at less cost than are the drive wheels 36 and particularly the drive motors therefor. In FIG. 3a the front and rear drive modules 30, 28 are aligned longitudinally with the footwear assembly, in FIG. 3b they are both turned at an angle in one direction to the same extent, and in FIG. 3c they are both turned in the same direction to a maximum of 90?, which allows the footwear assemblies to compensate for a sidestepping movement. The drive modules need only rotate through 90? to be able to compensate for a range of 360? of movement by a user's foot, because the drive belts can be driven in reverse. The drive belts 32a, 32b on each drive module are normally driven in the same direction, but just as is well-known in tank tracks they can additionally or alternatively be driven at different speeds or in different directions so as to permit a turning motion.

[0044] The drive frames 28a, 30a support the motors 34, drive wheels 36 and pulley wheels 38 and, when combined with the drive module cover 30b provide a strong and rigid support for the wheels on each side. The frames and chassis also provide channels for routing wires and cables, and space (mainly in the centre of the chassis, between the two drive frames) for locating electronics, sensors, and receiver/transmitters for communicating with an external VR computer 40 (shown in FIG. 1a). The footwear assembly is powered by a rechargeable battery pack 42 (shown in FIG. 2) mounted behind the heel cup 14.

[0045] Turning to FIG. 4, this shows the footwear assembly from the underside, with the drive belts removed. The drive wheels 36 and pulley wheels 38 are transversely splined to engage with transverse ribs 64 formed on the interior of each belt (see the exemplary belt 32a shown in FIG. 7) and ensure minimum slippage when the belts are driven; there is also a circumferential channel 44 formed in each wheel, and these are aligned longitudinally with respect to the footwear assembly. The function of these channels 44 is to engage with and retain a rib 46 (see FIGS. 5 and 7) formed on the internal surface of each belt, so as to prevent the belts from slipping transversely off the wheels during turning.

[0046] One of the objectives of the VR footwear assembly design is to support the weight of a person (i.e. about 100 kg), this is the load that each VR footwear assembly is designed to handle. This weight is distributed across a total of eight Pulleys, where each pair of wheel pulleys (forward and rear) is designed to cope with the largest dynamic loads. The four motors generate a high torque relative to their size, which is transferred through four independent belts. The speed of each motor is regulated using a feedback signal and a PID control loop. There are a number of advantages to this design, compared to a design with one or two motors: the compact arrangement of four motors allows the device to have a low profile (?45 mm from ground excluding the heel cup 14 and battery pack 42). Such a low profile and even mass distribution within the device, together with the large surface contact area provided by the belts, results in a stable platform to walk-on, with high surface traction.

[0047] FIG. 5 shows the chassis 26 of the footwear assembly schematically from the side, omitting the flexible platforms 18, 20, and it can be seen that the chassis 26 is hinged at 22 to allow the chassis 26 to bend along with the user's foot (not shown). The range of movement R of the hinge 22 is limited by end-stops to prevent rotation beyond set limits, with the hinging range being between 0? and about 45? maximum.

[0048] FIG. 6a shows the front end of the footwear assembly with the front flexible platform 20 removed and the front chassis 54 shown as transparent so the rotational drive arrangement for the front drive module 30 can be seen (that for the rear drive module 28 is essentially the same). FIG. 6b shows the same view as FIG. 6a, but here the front chassis 54 is opaque; FIG. 6c is again the same view, but with the front chassis removed. The drive module 30 rotates using a simple arrangement of spur gears. A larger, central gear 50 is attached to the lower surface of the front chassis 54 (not shown in FIG. 6b or 6c) and a smaller gear 52 connects to the turn motor (not shown, within the drive module cover 30b) mounted within the front drive frame 30a. A third gear 56 which may be offset from the centre, connects to a rotational sensor (not shown); the rotational sensor may be a potentiometer (variable resistor), however other sensor types such as magnetic or optical sensors would also work in this application. A potentiometer has the advantage of being low cost. Various types of gears could be used in this application; spur, helical, herringbone and/or bevel. There is a channel 66 through the front chassis 54 and the central gear 50 that allows wires to pass through. The front drive frame 30a and the front chassis 54 are held together by a central bolt (not shown). The weight (load) of the user is transferred through a central support ring 58 and an outer support ring 60, which is fixed to the drive module cover 30b. Grub screws or pins 62 extend through a channel in the front chassis 54 to provide physical end stops to rotation of the drive module 30 at +90? and ?90?.

[0049] FIGS. 8a and 8b are views similar to those of FIGS. 3a and 4, respectively, of a second embodiment of a footwear assembly 10 in accordance with the invention. This embodiment is similar in many ways to the first embodiment, but it has different belt and drive arrangements which will now be described (it should be understood that other aspects of the design and operation of the second embodiment are the same as in the first embodiment, some of which are referenced by a similar but hyphenated reference numeral in the drawings). As can be seen in FIG. 8a, there are four belts 32 on each assembly 10, two on each drive module as in the first embodiment, but in this embodiment the belts on each drive module are of equal length. Unlike the first embodiment, in this embodiment the motor does not drive a wheel which engages with the belt, but instead has an indirect drive arrangement. Each belt 32 has transverse ribs on its interior surface, as in FIG. 7, and runs between a first pulley wheel 38 and a second pulley wheel 38a, both of which are transversely splined to engage with the ribs on the inside of the belt 32. The second pulley wheel 38a for each belt has a central cylindrical portion 54 of smaller diameter than the remainder of the wheel, and this central portion is also transversely splined. The second pulley wheel 38a is driven by way of a motor 34 driving a primary drive belt 56 which is sufficiently narrow to fit within the smaller diameter portion, and has transverse ribs on its interior surface which are sized and configured to engage with the splined central portion 54 of the pulley wheel 38a, and also with a transversely-splined drive wheel 58 which is directly driven by the motor 34. The motor and the drive wheel share an axle (not shown) which extends transversely through the associated drive frame 28a or 30a so that the drive wheel 38 is located within the belt 32 on one side of the drive frame and the motor 34 is located within the belt on the other side of the drive frame (note that the belt 56 is shown only partially in FIG. 8b, so that the splines on the drive wheel 58 and on the central portion 54 of pulley wheel 38a are not obscured).

[0050] The rear drive module 28 (which could equally be a front drive module) shown schematically from beneath with both continuous drive belts and one drive wheel removed for clarity has a single drive motor 34 which, as with the embodiments described above, drives one splined drive wheel 36 to drive the continuous belts (not shown) via a transversely-splined drive wheel 58 and a toothed primary drive belt 56. The illustrated drive wheel 36 is fixed to one end of a shaft 66 extending transversely across the drive module 28 and which is rotatably supported by bearings (not shown) within the drive assembly 28a and/or the drive frame cover 28b. The other drive wheel (not shown for clarity) is fixed to the other end of the shaft 66, so that as the motor 34 drives the belt 56 and the drive wheel 36, the drive wheel on the other side of the drive module is driven in unison so that both continuous drive belts are driven together.

[0051] The footwear assembly described above is normally one of a pair for each user and has the following features and characteristics: [0052] It operates wirelessly, is compact and easily stored [0053] It allows a natural walking experience and stable movement without requiring a harnesses [0054] It can accommodate a fast walk: at least 1.2 m/s, and fully omni-directional with side-stepping (strafing) [0055] It has built-in 2D surface tracking and positional correction [0056] It can keep users within a small play area, approximately 1.1?1.1 m for example. [0057] There can be angular motion sensing for body direction. [0058] SteamVR integration (OpenVR/OpenXR) and possible support for Oculus Quest. [0059] It is lightweight, at about 1.2 kg per shoe, and it is comfortable and of ergonomic design [0060] Each footwear assembly can allow approximately 2 hours use with built-in battery, more with an optional waist mounted battery [0061] It employs high performance long lasting Brushless DC motors.

[0062] Each VR footwear assembly can be configured to be worn either directly on a user's foot, where a cushioned sole is attached to the upper surface of the platform, or alternatively the footwear device may be strapped to a person that is wearing normal shoes, in which case the cushioned sole may be removed by the user and shoes placed directly onto the platform, and held in place using a system if straps. The cushioned sole is designed to provide comfort as well as keeping the user's foot in the correct position, additionally multiple straps hold the foot onto the device.

[0063] It will of course be understood that many variations may be made to the above-described embodiments without departing from the scope of the present invention. For example, the heel cap and/or platforms may incorporate means to adjust for different foot sizes, so that the assemblies can be easily adapted for use by other users. The platforms are shown as flat but they could be moulded to accept lower surface of the foot, to provide a more comfortable fit. The battery pack may be located in a different location than as shown, for example it may be located under the heel support and re-configured as a flattened battery pack; the same applies to the electronics/sensor/transmitter receiver elements, these may also move from the central chassis location, such as by being located behind the heel cup, packaged as a small box. Whilst the footwear assembly has been described in connection with VR equipment, this is not essential; the VR footwear assembly could be used without AR/VR equipment, for example rehabilitation in Health Care, where this type of locomotion system is used by patients regaining the ability to walk. The upper platforms 18, 20 which are intended for a foot, may be swapped/exchanged for different platforms designed to accommodate a shoe with fixings and straps as appropriate. The heel cup 14 may be mounted to the rear end 12 by way of a slide arrangement or the like so that the position of the heel cup on the rear end can be adjusted in a forward or rearward direction; this allows the footwear assembly to fit and be used by persons having smaller or bigger feet. The pulley and/or drive wheels may be adjustably mounted so as to place the continuous belts under tension, and the directly driven drive wheel may be similarly adjustable to tension the primary drive belt. The outer surface of each belt is shown in the drawings as smooth, but there may be a tread pattern (such as simple transverse ribs, or a more complicated configuration) provided to improve traction. The drive modules in a footwear assembly may be any combination of any of the different drive modules shown in FIGS. 4, 8a and 8b and 9. For example, a VR footwear assembly may comprise a front drive module with one drive motor and a rear drive module with two drive motors, or vice versa, and the drive module with the two drive motors may have equal or unequal length drive belts; alternatively, the drive modules in a footwear assembly may all be of the same type.

[0064] Where different variations or alternative arrangements are described above, it should be understood that embodiments of the invention may incorporate such variations and/or alternatives in any suitable combination.