Patent Description:
<CIT> discloses an omnidirectional moving surface system with a tread for the user to walk and ball bearings for reducing friction on the tread movement.

An omnidirectional moving surface system according to the invention is defined in claim <NUM>.

The OmniPad is an omnidirectional treadmill that allows users to walk, jog, or run in any direction. When the OmniPad is coupled with computer-generated immersive environments users can maneuver their way on-foot through <NUM>-degree VR environments of infinite expanse and scope.

The OmniPad™ is an Omni-Directional locomotion Input device specifically intended for use in virtual reality immersive environments. The OmniPad™ is the primary component of the OmniPad Environment.

The OmniPad is made up of many parts and subassemblies. This document provides a general description of the operation and components of the OmniPad.

Tread: The tread will be fabricated using highly flexible and extremely durable rubber-like material like Silicone, EPDM or natural rubber which can be motivated by a person walking or running. The tread is manufactured in such a way that it is a single sphere like embodiment, which is then wrapped over the spindle, entirely encasing the spindle and bearings. This material is flexible enough to enable a <NUM>- degree change in direction around the spindle.

Spindle - Walking Platform: The Spindle will be approximately <NUM> thick and approximately <NUM>-<NUM> meters diameter. The Top Surface is designed to support the user during operation.

Edge Bearings: The edge bearings reduce the friction on the tread (bladder) as it rotates around the spindle. The bearings enable the free <NUM>-degree mobility of the bladder.

Bobbin: Referring to <FIG>. The bobbin assembly is the combination of the tread (bladder), spindle, edge bearings and lubrication as shown below. The bobbin assembly allows the user to be in the virtual environment and move as if they are in the natural world. This assembly is supported by the support bearing blocks.

Support Bearing Block: Referring to <FIG>. The bearing support system allows the bobbin assembly to move with little or no friction, as shown below. This system supports the bobbin during operation and translates the loads to base system.

Motor Drive System: Referring to <FIG>. The Motor drive system is used to assist the users' natural locomotion, and to relay the locomotion gestures to the virtual environments, which will update in real time, as shown below.

Tread Materials: The tread will be fabricated using highly flexible and extremely durable rubber-like material like Silicone, EPDM or natural rubber which can be motivated by a person walking or running. The tread is manufactured in such a way that it is a single sphere like embodiment, which is then wrapped over the spindle, entirely encasing the spindle and bearings. This material is flexible enough to enable a <NUM>- degree change in direction around the spindle. The tread will be manufactured in such a way that it is a continuous surface, which is then wrapped over the spindle to entirely encase the spindle and bearings.

Smart Adaptive Tread Material: The Smart Adaptive Tread Material will alter, in real time, the material's properties when a voltage, electrical field, current or magnetic field is applied. When the voltage, current or field is applied to a specific area of the surface just that area's material properties will change. For example, as the current or field is applied to the material the material will become more flexible or stiff in that localized area only. Referring to <FIG>. Area <NUM> = Walk area, drive area or support area, stiff area to limit slip or buckling in the material Area <NUM> = Flexible area.

Ferrous Tread Material: Bobbin Support Referring to <FIG> and <FIG>. Currently, magnetic bearings are commonly used in industrial applications such as turbomolecular pumps, or even mag-lev trains. The Ferrous tread material allows for the omnidirectional locomotion surface to be magnetically polarized, thereby, attracting or repelling magnetic or electromagnetic forces. This allows the tread to magnetically levitate the bobbin assembly. In <FIG> Area <NUM> = Magnetically polarized tread Area <NUM> = Mag-Lev bearing block.

Friction Reduction: Referring to <FIG>, another use for the ferrous tread material is to be suspend away from the spindle, therefore lowering the frictional forces. By using the magnetically repelling forces and the elasticity of the tread itself, the tread will separate from the spindle providing a small gap, thus lowering the friction between the spindle and the tread. In <FIG>, Area <NUM> = Negatively charged outer surface Area <NUM> = Positively charged inner tread surface; Area <NUM> = Positively charged outer spindle surface.

Goldberg Polyhedral Tread Material: Referring to <FIG>Another embodiment of the bladder is comprised of discrete segments. These segments typically take the shape of either hexagon or pentagon polyhedrons which are edge-connected to form a sphere.

Polygon segments used in any of the Goldberg polyhedral spheres will be made from a flexible material. The individual polyhedral elements need to stretch in any arbitrary direction a minimum of <NUM>% of its original dimension in any planar direction. Categories of materials that possibly fulfill this mission are thermoplastic rubbers, or stretchable fabric like elastane (Spandex).

The Goldberg construction uses hexagons and pentagons. There are other geometries available as well, such as parallelograms. These alternate constructions are not Goldberg polyhedra.

Referring to <FIG>, a further enhancement of the Goldberg segments is inclusion of a hole pattern. Inclusion of holes permits the structure to stretch with lower material stress for equal strain. These patterns are made from Hexagon and Pentagon Shapes like a soccer ball. Elastomers shapes stretch to fill the gaps. Spring hinge pins allow for bending on the hinge lines.

Multilayer Skin Tread: Referring to <FIG> and <FIG>, the Multilayer Skin Tread use thin layers of different tread materials, coating and textures to have specific properties on the different layers. The inner layer needs to be extremely low friction such as Teflon (PTFE) coating, as it is sliding on the spindle surfaces. The outer layer preferentially needs to have a higher friction, or needs to have traction so the user's foot surface and the motor drives will be able to move the tread surface in any direction. The inner and outer surfaces of each layer may or may not be bonded together. Working with layers multiple thin layers will create a stronger tread, and will also aid in the overall assembly of the entire bobbin unit.

Referring to <FIG>. In various embodiments, layers may or may not be bonded together, layers may or may not be of the same materials or material properties, and optionally inside layers do not have to be bonded or sealed (areas <NUM>-<NUM> below). Outside layers may be selected for friction with the feet or footwear of a user. Inside layers may be selected for reduced friction of motion of the tread surface against the supporting structures. Outside layers (e.g., layer <NUM>) may, therefore, have a greater coefficient of friction than inside layer <NUM>.

FRICTION REDUCTION SYSTEM: The surface between the Spindle and the Tread is a very high friction force area. To alleviate these frication forces, we have designed different alternative methods. Although the primary solution to high friction force is employment of a low friction layer such as Teflon™ (or PTFE), other solutions are available.

Air Bearing: Referring to <FIG>, the Air bearing spindle uses a similar concept to an air hockey table. An air hockey table uses small air jets to levitate a puck on the surface. The air bearing spindle has a porous spindle surface or uses air jets to separate the tread material from the spindle surface. This will minimize or eliminate the friction. The arrows in the image below represent the airflow applying a force to the tread/bladder. This driving force causes the tread to expand like a balloon away from the spindle, thus lowering the friction between the two elements.

Magnetic Levitation: By utilizing the magnetically polarized tread material and a permanent or electromagnet, the tread material can be levitated above the spindle surface minimizing or eliminating the tread-to-spindle contact, thereby reducing or eliminating the friction forces.

Referring to <FIG> and <FIG>. Area <NUM> = Magnetically Polarized Tread; Area <NUM> = Permanent or electromagnetic spindle; Area <NUM> = Inductive power supplied to spindle for electromagnetic spindle; Area <NUM> = Exterior surface of tread has an opposing magnetic charge to the inner surface. Area <NUM> = Interior surface of the tread is polarized differently than the spindle to create a separation of the tread from the spindle. This is to eliminate (or minimize) the friction between the spindle and the t read. Area <NUM> = The spindle magnet can be permanent or electromagnet. The electromagnet can be powered by an inductive power coil similar to wireless cell phone charging. Control of the electromagnet is done through wireless communication.

Dry & Wet Lubrications: Dry and wet lubricants are used to reduce the friction between the tread and the spindle. These lubricants are also used to dissipate some of the thermal energy created by the friction.

Ball Transfer Bearing: Referring to <FIG>, this is the most straightforward means of friction reduction around the edges as it transmits motion onto the rolling contact of a bearing. Balls, rollers or rollers+ balls around the outside accomplish this task. On the top surface, this may be accomplished by employing a bed of omni-rollers lined up to form a surface. Omni-rollers need to be sized small enough to form a surface with a large number of foot contact points, but large enough to employ bearings of reasonable size.

Referring to <FIG>: Area <NUM> = Edge ball bearing; Area <NUM> = Magnet embedded inside the edge bearing; Area <NUM> = Magnet embedded inside the ball transfer base unit; and Area <NUM> = recirculating bearings.

Referring to <FIG>: Area <NUM> = Edge ball bearing, which is similar to a ball transfer unit with smaller ball bearings behind the main ball in contact with bladder (t read) Area <NUM> = Bearing retainer (may not be required) Area <NUM> = Spindle.

Roller-ball-socket unit: Referring to <FIG>, motion along the OmniPad periphery varies continuously. Motion vectors combine both vertical and horizontal motion. It is the most straightforward way to provide a rotational surface for vertical motion. Horizonal motion along the sides will need to rely on low sliding friction or bearing supported rollers.

From the cross section of <FIG>, we see the repeating bearing unit that rings the active surface. In this embodiment, we see a center roller with a ball. Closer inspection shows the roller mounted on a central ball bearing, which will transmit vertical bladder forces with high efficiency. The ball is mounted in a cup, and the cup also mounted on a bearing.

When these units are stacked together around the periphery of the OmniPad, each ball fits into the socket of the next. Further, we see that each ball is held by two sockets, with each socket having its own bearing. The ball will rotate relatively freely, with some friction against the bearing cups because of the mounting angle. Separate segments permit varying vertical motion vectors to maximize the bearing supported motion, as opposed to friction-supported motion. This type of repeating unit is driven from the outside of the OmniPad.

Referring to <FIG>. To preserve a secure ball mount and avoid interference of the roller segments, the above design employs straight versus curved roller segments. This design can be driven internally or externally as before. Advantages: fewer parts, more driving surface (for internal drive) and potentially less bladder stress due to larger roller diameter.

In <FIG>: Area <NUM> = Roller surface; Area <NUM> = Ball bearing allowing for free movement between rollers Area <NUM> = Optional motor drive system; and Area <NUM> = Roller mounting bracket.

In <FIG>, Area <NUM> = Ball bearing; Area <NUM> = Outer ball roller cup Area <NUM> = Inner roller; Area <NUM> = Bearings; and Area <NUM> = Optional motor drive belt.

TREAD SUPPORT SYSTEM: Referring to <FIG>. The bearing support system allows the bobbin assembly to move with little or no friction. This system supports the bobbin during operation and translates the loads to base system.

Magnetically Levitated Spindle: Currently, magnetic bearings are commonly used in industrial applications such as turbomolecular pumps, or even mag-lev trains. The magnetically levitated bearing supports leverage on the technology that is used in other products to create a non-contacting bearing system that uses permanent magnet and/or electromagnets to magnetically levitate the bobbin assembly without any physical contact. Referring to <FIG>, and <FIG>, the magnetically levitated bearing supports eliminate any mechanical wear that the contact bearing create, and it eliminates friction. The OmniPad uses permanent magnets inside of the bobbin assembly, and electromagnets in the bearing block.

In <FIG>: Area <NUM> = Permanent magnet embedded into the spindle Area <NUM> = Permanent or electromagnet. In <FIG>: Area <NUM>= Magnetically polarized tread Area <NUM> = Mag-Lev bearing block.

Ball Transfer BearingBlock: Referring to <FIG>, and <FIG>, the ball bearing supports the bobbin assembly with a thrust bearing to allow for low friction to transfer the loads. The below images show how the ball bearing block interfaces with the bobbin assembly in vertical and axial loads. A minimum of <NUM> bearing blocks are required, while the images below show <NUM> bearing blocks. In these figures: Area <NUM> = Ball transfer units configured to support axial and radial loads. Motor drive can be integrated into the ball transfers.

Omni Wheel: Referring to <FIG>. Omni wheels of the standard (shown) or the Mecanum wheel type are used to support and stabilize the spindle assembly. No fewer than three points of contact are required for full stability, though six are depicted. Support nodes require wheel pairs: one for bottom and one for top. Either or both of these wheels may be powered to control surface movement.

As with other drive mechanisms, the surface velocity vector at the contact point of the roller is what determines roller drive velocity. Omni-wheels have the unique feature of driving only in the plane of the wheel, orthogonal to the drive axis. All other motion is passed through the rollers. Drive velocity at a given point is accomplished by revolving and driving only the motion vector that the roller can address.

Referring to <FIG>, the system is supported at <NUM> degrees above and below the center line by <NUM> to <NUM> pairs of support wheels. These support wheels can be used in tandem to drive tread.

SPINDLE: The spindle provides the rigid surface for the user to operate on while providing a support structure for the edge bearings. The Spindle will be approximately <NUM> thick and approximately <NUM>-<NUM> meters diameter. The Top Surface is designed to support the user during operation.

The difficulties in assembling the bobbin assembly in real world manufacturing has lead us to investigate solutions for this problem. To understand this more, we are inserting a disc (the Spindle) into a Tread (or Bladder), while stretching the bladder to very high loads in order to eliminate any wrinkling or bunching, and to evenly distribute the forces throughout.

Solid or Segmented Spindle: Referring to <FIG>, the segmented spindle takes a rigid solid spindle and breaks it into pieces that can be assembled inside the bladder. Once assembled, the spindle is then expanded (either manually or automatically) to the proper size and shape. In some embodiments, an otherwise solid spindle is broken into smaller pieces to assist in assembling the spindle into the bladder. Optional a ratcheting device to expand the spindle once assembled inside the bladder.

Inflatable Spindle: The inflatable spindle (See <FIG> Area <NUM>) allows for the spindle to be inserted into a small opening in the Bladder during the assembly process. The spindle is then filled with a media (Gas or liquid) to rigidize the spindle such that the loads (bearings and user's weight) are properly supported and managed. One of the major factors in this material is the low coefficient of friction.

DRIVE SYSTEM: Driving the Omni-Directional Treadmill can be accomplished via internal or external motors. The drive system is essential to overcome the high frictional forces that the tread experiences. These motors are typically controlled by circuits responsive to sensors that detect motion of a user standing on the treadmill. The circuits configured to keep the user centered on the treadmill as the user moves on various directions by walking or running, etc..

Internal Drive: Referring to <FIG>. This repeating unit places a drive sprocket central to the roller and runs the drive belt internally. We see a recurring theme of separate sections. As before, the balls are mounted in sockets that are themselves free to rotate. A further variation, not shown, would be to connect all four central roller segments into one, and to put the bearing under the ball cup as seen in the previous design. The variation would drive more of the edge surface but would have more vertical friction shear.

Referring to <FIG>: Area <NUM> = Roller surface; Area <NUM> = Ball bearing allowing for free movement between rollers; Area <NUM> = Motor drive system and Area <NUM> = Roller mounting bracket. Referring to Figure 20B: Area <NUM> = Ball bearing; Area <NUM> = Outer ball roller cup Area <NUM> = Inner roller; Area <NUM> = Bearings; and Area <NUM> = Motor drive belt.

Omni Wheel: <FIG> illustrate six external omni wheels driving a surface. Omni-rollers on the bottom are connected to servo motors. Each omni roller drives only the motion vector tangent to the contact point. Motion transverse to the contact point passes through because of the roller construction. Omni-rollers on top typically serve to constrain the OmniPad fully in 3D-space. Further, upper rollers can be used to increase the contact force of the drive rollers. In theory, only three drive rollers are needed to address all top surface motion vectors.

Drive Wheel: Referring to <FIG> A simple drive system can drive the tread from a series of motors mounted under the bobbin assembly. See isometric view in <FIG>. These motors are mounted on a rotary table to allow for motion in any direction. The images below show a motor system with <NUM> motors that are synchronized to move the tread while minimizing the adverse effects on the top user surface. In <FIG>, Drive system with a simple motor and wheel on a rotating table: Area <NUM> = Motor and encoder for main drive wheel; Area <NUM> = Motor and encoder for table rotation; Area <NUM> = Main Drive wheel, used to move the tread around the spindle Area <NUM> = Rotating Table; and Area <NUM> = Motor Base.

Ball Transfer Drive System: Referring to <FIG>, the Ball Transfer Drive System uses <NUM> motors to drive a ball supported by bearings underneath. This allows the motors to drive the ball in any direction. This motor drive system can be placed into the Ball Transfer Bearing Blocks, or as a stand-alone motor system in the center of the bobbin assembly.

CONTROL SYSTEM: Referring to <FIG>, the control system design controls the speed and direction of the tread surface. It ensures that the user has a safe and entertaining experience while using the omnidirectional moving surface. The control system utilizes user motion feedback, through cameras, force feedback through the safety harness and feedback from the drive motor system. These different feedback systems provide validation and confirmation of the user and operation of the OmniPad system.

Motion Feedback: Referring to <FIG>, using Cameras pointed at the user or other sensors, the OmniPad control system can determine the position, direction and speed of the user. As the user changes any or all of the above locomotion characteristics, the motion feedback system responds to and can predictively adjust the OmniPad tread surface accordingly. The Motion feedback system can also identify where the users body parts are located providing additional feedback into the virtual environment. By recognizing the users' body position and velocity, the motion feedback system calculates where the user next step will be placed and the center of mass. This functionality will assist in the overall effectiveness of the immersive experience.

Motor Feedback: By monitoring the motors' direction (forward or reverse), velocity (via motor encoder or steps) and angle of attack (rotational direction relative to ground) we can control the actual position and motion of the tread. By monitoring the motor current and encoder position the system can monitor any system faults on the tread (i.e., the tread not moving, when we expect it to be moving).

User Force Feedback: Sensors on the user harness, footwear, and/or on the treadmill provide accelerations, directional and angular forces that the user generates while operating the OmniPad. These accelerations and forces are processed and converted into responses by the OmniPad tread to change direction or increase or decrease the speed while the tread is moving.

Walking or running on flat ground is adequate, but there are also inclines and declines in the real world that can be replicated by the OmniPad system. Being able to simulate walking up, down or across hills; or even to have the ability to simulate moving across different types of surfaces like gravel, sand, or mud will greatly enhance the virtual experience.

Tilting Robotic Platform: Referring to <FIG>, by using a combination of linear actuators and sensors (load cells, position indicators) the locomotion surface can be actuated in order to change the tilt or pitch of the tread surface. By implementing the Tilting Robotic, or Stewart Platform the OmniPad can simulate to the user moving up, down or across slopes in the virtual environment.

Varying Surface Emulation: Referring to <FIG>, when the user is immersed in the virtual world, with visual, audio and locomotion, the OmniPad Control System can make small adjustments to the angle and elevation of the tread surface to simulate a wide variety of surfaces, such as gravel, sand or mud.

The OmniPad control system along with the immersive VR environment manipulates the users' sensory perception to give the feel of walking or running on different surface types and densities. The combination of the linear position indicators, and the load cells allows the control system to calculate the position of each of the user's feet. Thus, defining the accurate and subtle changes required to simulate the varying surface types.

Claim 1:
An omnidirectional moving surface system comprising:
a first plurality of ball bearings;
a spindle for positioning the ball bearings such that the ball bearings form a ring around the spindle;
a bladder for enveloping the plurality of ball bearings; and
a plurality of omni-wheels affixed intermittently around the bladder to support the bladder.