GB2523137A

GB2523137A - Acoustic tracking means

Info

Publication number: GB2523137A
Application number: GB1402572.0A
Authority: GB
Inventors: Charles Edmund King; Julian David Williams
Original assignee: Individual
Current assignee: Individual
Priority date: 2014-02-13
Filing date: 2014-02-13
Publication date: 2015-08-19
Also published as: WO2015121279A1; GB201402572D0

Abstract

A motion tracking system for a locomotion platform comprises a locomotion platform 10, in particular an omni-directional treadmill, at least one acoustic detection device 20, and means for interpreting the signal from the acoustic detection device to provide input to a virtual reality system. The omni-driectional treadmill comprises a bowl shaped upper surface used with special footwear 90 that generates sound when sliding on the upper surface. Preferably at least two acoustic detection devices, e.g. microphones, which are mounted on or close to the surface of the locomotion platform, are used. The surface of the locomotion platform may have an embossment pattern which varies such that different sounds are made as the footwear slides over it in different ways. In this way the location and direction of movement of the feet of a user can be interpreted. The system is preferably used with a head mounted display to provide a virtual reality environment.

Description

MOTION TRACKING MEANS FOR A LOCOMOTION PLATFORM

A motion tracking means for a locomotion platform is described that finds use in linking motion on a locomotion platform to visual software viewed by a user using locomotion platform.

Locomotion platforms provide a means of omni-direction movement exemplified by ambulation or S simulated walking e.g. using a reciprocating foot sliding motion) whilst maintaining the user in a fixed location that is within the bounds of the locomotion platform. The objective of the disclosed invention in our earlier patent U57470218B2 is to provide a locomotion platform. With reference to Figure 1 adapted from our earlier patent US7470218B2 there is provided a concave platform 10 for a user 15 to stand on. Platform 10 has surface 200 and together with user's footwear 90 comprise materials to reduce interface friction. Further objectives are that the user remains constrained to the platform 10 area and a user 15 may turn and walk in any horizontal direction.

Locomotion platforms or omni-directional treadmills find application in enhancing virtual world immersion where users are provided with typically large format screen displays or head mounted display providing visual immersion and locomotion platform enables "movement" in the imaged virtual world. Profound virtual reality immersion is brought about by visual content, sound and movement, the latter giving rise to proprioceptive and kinaesthetic familiarity and memories, giving rise to better immersion.

Ideally when a user moves their feet on a locomotion platform to "walk" or "run" in a virtual world presented to them by a screen or head mounted display, the visual scene should move and modify as expected as if the user was actually present in the virtual world scene. Indeed synchronisation between user movement in the real world and their first person view in a virtual world is essential for profound immersion. Lack of synchronisation is called latency and brings about a "break in presence" i.e. the user's mind is brought back to the present reality. Motion tracking and synchronisation of this motion between real and virtual worlds is essential for profound virtual reality immersion.

Motion tracking on locomotion platforms has taken a variety of different forms depending on the method of locomotion and accessibility of the user. For instance roller style treadmills can provide roller movement and so initiation, duration and stopping of movement by way of suitable sensors attached to the rollers and this information can be linked to visual software to provide synchronised movement in a virtual world. The VirtusphereTM, a large "hamster ball" on pairs of orthogonally mounted rollers enables a user inside the sphere to walk around using a wireless head mounted display with motion being captured from the rollers and synchronised with the visual scene presented to the user.

However roller locomotion platforms have not found wide success because of size, complexity and system inertia. No direct access to the user means wireless head tracking needs to be synchronised with roller movement and challenges with system inertia plus cost of wireless head tracking has limited uptake of this technology.

Alternative approaches use optical tracking particularly the use of time-of-flight or projected patterns to determine an object's position and motion such approaches may be termed remote sensing. Xbox Kinect'TM, Xbox OneTM and the Eye Toy'TM are examples of this technology. Optical tracking typically uses dual cameras and algorithms to determine position and movement of objects and successfully links virtual and real world motion. However this technology is costly and complex for end users and for many users requires too large an area e.g. of home or office for optimal use of the cameras. Optical remote sensing also requires visual access to the user to determine walking motion and this presents a problem to locomotion platforms which often have support structures which limit line of sight to users.

In our earlier patent US7470218B2 the entirety of which is incorporated here by reference there are described other approaches to motion tracking as follows: In one mode of use, the user wears virtual reality visual display glasses and wears 3-dimensional tracking devices on or close to their feet. 3-dimensional tracking devices are typically used for motion capture. These devices output channels of information that corresponds to their X, V and Z position relative to a magnetic source. A computer program that samples the X, Y, and Z position at sufficient intervals can compute the user's speed and direction.

In another mode of use, the platform upper surface contains a plurality of pressure sensors. These are activated as the user's feet press upon them. By analysing the position and sequence of activated sensors, relative to time, the user's speed and direction is computed.

In the magnetic and pressure based motion tracking examples referenced above, though effective, these motion tracking solutions are complex and carry significant cost.

To address current problems of motion tracking on locomotion platforms i.e. complexity, associated cost, limited application and challenging implementation, the present invention seeks to provide a simple, low cost, generally applicable motion tracking solution based on audio tracking that may use audio hardware and software accessible on most computers. The present invention may be adventitiously used in combination with the teaching of US7470218 and is applicable to locomotion

of this general description as follows:

According to the present invention there is provided a motion tracking means for a locomotion platform comprising a locomotion platform, at least one acoustic detection device, footware worn by a user using said locomotion platform and at least one means of interpreting signal from said at least one acoustic detection device said interpretation influencing visual software driven by computer type hardware and imaged by at least one imaging device.

Preferably there is provided footware that generates sound when sliding on said locomotion platform.

Usefully footware is provided wherein footware interface surface differs between feet and generates different sound from each foot when sliding on said locomotion platform.

In one embodiment a locomotion platform is provided wherein at least one acoustic detection device is close to, attached mechanically, adhesively or moulded to a surface of said locomotion platform.

In a preferred embodiment there is a means of tracking motion wherein said locomotion platform is a single moulded piece and is substantially dish shaped.

In various formats there is provided a substantially dish shaped locomotion platform made from a polymer said polymer exemplified by the following engineering polymers: PTFEJ PET, ABS, HDPE, UHMWPE, PA6, PA66. Other polymers and polymer combinations are possible.

Usefully a substantially dish shaped locomotion is provided wherein said dish comprises one or more formed sections wherein forming is exemplified by thermoforming or injection moulding.

In one embodiment there is provided a motion tracking means wherein output from said at least one acoustic detection device provides motion control signal in accordance with those recognised by computer driven by 2D or 3D visual software to achieve locomotion displayed by said at least one imaging device.

Usefully at least one imaging device is provided wherein said imaging device is emitting or projection screen technology for one or more viewers or head mounted display for an individual viewer or both.

Preferably there is provided a motion tracking means wherein signal from said acoustic detection device is amplified and interpreted by computer microphone audio card and associated software.

Preferably a motion tracking means is provided wherein at least two acoustic detection devices are mounted on or close to a surface of said locomotion platform.

Advantageously there is provide a motion tracking means wherein at least one of said at least two acoustic detection devices is used for noise cancellation to remove sound generated by motion of footwear on said locomotion platform.

In another embodiment a motion tracking means is provided wherein said at least two acoustic detection devices provide signal data input to said computer driven 2D or 3D visual software providing locomotion and direction of motion translation between said locomotion platform and said visual software outputted to one or more screens.

Valuably the top surface of a dish shaped locomotion platform is provided with positive or negative embossments, embossed in the dish surface.

Preferably a dish shaped locomotion platform engages with footware wherein said footware produces sound patterns when sliding on said embossed patterns.

In another embodiment there is provide a motion tracking means comprising a dish shaped locomotion platform, footware and embossed patterns and at least one acoustic detection device wherein said embossed patterns are different in different regions of said dish producing different sound patterns when said footware slides across said different regions, said different sound patterns enabling feet location and direction to be interpreted by way of said means of interpreting signal from said at least one acoustic device said interpretation influencing visual software driven by a computer type hardware and imaged by at least one imaging device.

The invention will be further described with reference to the following drawings: Figure 1 is a perspective schematic diagram of a user on a locomotion platform Figure 2 is a block diagram of a motion tracking means.

Figure 3 is a schematic drawing of locomotion platform footware S Figure 3a is a schematic diagram of a low friction footware disc Figure 4 is a schematic drawing of a locomotion platform with attached acoustic detection devices Figure 5a is a schematic drawing of negative embossments Figure Sb is a schematic drawing of positive embossments Figure 6 is a schematic drawing of multiple different region embossed locomotion platform

Detailed Description

A locomotion platform 10 is shown schematically in Figure 1 wherein a user 15 slides their feet in more or less of a reciprocating action wearing footware 90 in contact with a top surface 200 of a locomotion platform 10 to which acoustic sensors 20 have been attached. Acoustic sensors 20 are preferably attached to bottom surface 230 of the locomotion platform 10 or indeed the side 210, so long as the position of acoustic sensor enables pick-up of vibrations generated by motion of the user's 15 feet and footware 90 and does not interfere with the sliding action of the user's footware 90. In a preferred embodiment and with reference to Figure 4, acoustic detection devices 20 are mounted on the bottom surface 230 of locomotion platform 10, said platform forming a cavity 3 when in use on a floor or base 28.

With reference to Figure 2, there is provided a motion tracking means 5 for a locomotion platform comprising a locomotion platform 10, at least one acoustic detection device 20, footware 90 worn by a user 15 using said locomotion platform 10 and at least one means 35 of interpreting signal from said at least one acoustic detection device 20, said means 35 of interpreting signal providing influence of visual software driven by computer type hardware 40 and imaged by at least one imaging device 60, 80.

With reference to Figures 1 and 3 concerning a means of motion tracking) for which the present invention is primarily concerned, there is provided footware 90 worn by a user 15 that generates sound or vibrations when sliding on said locomotion platform 10. Sound may be generated by any interaction of surfaces 440, 200 and all such surfaces are included so long as they also function to reduce friction between said interacting surfaces. Exemplar surfaces are ceramic and polymer where for convenience ceramic is likely to be associated with footware 90 and polymer with that of locomotion platform 10, though the reverse combination is included: Examples of possible surface combinations include: polymer! polymer, metal! polymer, glass! polymer. A useful combination is alumina discs 460 and high density polyethylene for locomotion platform 10. Though a disc 460 is shown in Figure 3 and 3a, this is for illustration purposes only and any shape may be used so long as interaction surface 440 exhibits low friction (coefficient of friction <02) with locomotion platform surface 200.

With reference to Figure 4 there is provided a locomotion platform 10 wherein said at least one acoustic detection device 20a,b,cd,e is close to, attached mechanically, adhesively or moulded to surface 200, 230, 215, 210 of said locomotion platform 10. With reference to polymer that substantially forms the locomotion platform 10, there is preference in using a polymer of elasticity modulus between SOOMPa to 3GPa so as to minimise harsh noise and yet transport sound generated by interacting surfaces 440 and e.g. 200 to acoustic detection device 20. Vibrations caused by motion of footware 90 on a polymer locomotion platform 10 travels faster than in air and preferably acoustic detection devices 20 are attached to the locomotion platform 10 so as to receive said vibrations; attachment means for acoustic detection devices 20 may include mechanical, adhesive, or moulding or any suitable attachment means to provide effective sound communication between locomotion platform 10 and acoustic detector 20. In one embodiment acoustic detection devices 20d may be placed on the floor 28 under said locomotion platform 10 and in another acoustic detection devices 20a, 20e may be placed inside 215 or outside 210 of said platform 10.

Of particular value to motion tracking S using acoustic detection devices 20 with locomotion platform 10 is a cavity 3 formed by locomotion platform 10 when in contact with floor 28. In such instance acoustic detection devices 20 are shielded from extraneous sound when attached on inside of cavity 3. Furthermore piezo-electric acoustic detection devices exhibit low signal to noise ratio which is valuable when using time delay estimation algorithms to provide direction information.

Again with reference to Figures 2 and 4 there is provided a means of tracking motion S (the primary aim of the present invention) which is dependent on placement of acoustic detection devices 20 on or near the locomotion platform 10 and a preferred shape for said platform 10 is substantially "Dish" shaped and preferably the locomotion platform lOis made from a single moulded piece.

Preferably a substantially dish shaped locomotion platform 10 is made from a polymer exemplified by: PTFE, PET, ABS, HDPE, UHMWPE, PA6, PA66 though other polymers or combinations, alloys are possible. More preferably a dish shaped locomotion platform 10 is made in a single piece by any polymer forming technology exemplified by thermoforming, vacuum moulding and injection moulding. Other forming approaches are possible. A locomotion platform 10 may also be formed in more than one section and joined together for use.

With reference to Figure 2 and 4, there is preferably a single piece, convex dish shaped locomotion platform 10 used in association with acoustic detection devices 20, low friction footware 90, signal interpretation unit 35 and associated software that interacts with visual software and so synchronises motion on locomotion platform 10 with visual software imaged on screens 60, 80.

Less preferred is a multi-piece locomotion platform 10 in which there is more than one joining facet.

Returning to Figure 2 there is provided a motion tracking means 5 wherein output from at least one acoustic detection device 20 provides motion control signal in accordance with those recognised by computer 40 driven by 2D or 3D visual software to achieve locomotion displayed by at least one imaging device 60, 80.

S

Preferably an imaging device 80 is a Head-Mounted Display. However a user of a locomotion platform 10 of the present invention may advantageously stand in front of a computer visual display and "walk" in the locomotion platform 10 and acoustic detection devices 20 of the present invention translate movement of feet on the locomotion platform 10 by way of computer linked S audio hardware 35 into motion on the visual display 60. Alternatively an imaging device 60 may be a front or back projection screen.

There is provided as a primary aim of the present invention a motion tracking means 5 wherein a signal from acoustic detection devices 20 is amplified and interpreted by computer microphone audio card 35 and associated software, which audio cards are frequently capable of stereo signal analysis.

Acoustic detection devices 20 may be passive microphones exemplified by piezoelectric, electrostrictive and magnetostrictive technology or active microphones exemplified by condenser / capacitor technology.

Advantageously) with reference to Figure 1 and Figure 2, at least two acoustic detection devices 20, 22 are mounted on or close to a surface of said locomotion platform 10. Close mechanical connection between acoustic detection devices 20, 22 and locomotion platform 10 achieves a good acoustic link and acoustic detection devices 20, 22 effectively pick up footware 90 motion of the user walking on locomotion platform 10.

With reference to Figure 1 and 7 the action of moving footware 90 over surface 200 of locomotion platform 10 generates noise and with reference to Figure 2, such noise when detected by acoustic detection devices 20, 22 may be advantageously used to control motion in computer driven visual software. Advantageously in one embodiment at least one acoustic detection device 20, 22 is used for noise cancellation to remove sound experienced by user 15 generated by motion of footwear 90 on a locomotion platform 10.

Alternatively and advantageously a motion tracking means 5 is provided wherein at least two acoustic detection devices 20, 22 provide signal data input to computer driven 20 or 3D visual software providing locomotion and direction of motion translation between a locomotion platform and visual software outputted to one or more visual display screens 80, 60.

As may be imagined the use of acoustic detection device 20 in Figure 2, for noise cancellation may be used in parallel with another acoustic detection device 22 to provide locomotion and direction of motion information to control computer driven software for translation between real and virtual worlds. Advantageously noise cancellation, locomotion and direction of motion may be simultaneously achieved by use of a suitable number of acoustic detection devices 20, 22.

Valuably to assist determining motion and direction of motion of a user's 15 footware 90 when traversing the top surface 200 of a locomotion platform 10, the top surface 200 may be embossed with embossments 232, 234 shown schematically in Figure 5a and Figure Sb. Embossments may be positive 234 or negative 232 and may be of any shape. In one particular embodiment a pinseal emboss pattern is used. Advantageously the sliding of footware 90 over embossments 235 produces sound patterns that may be used to determine motion and direction of motion once detected by acoustic detection devices 20, 22 the outputs of which are interpreted by audio card hardware 35 and computer software (not shown).

With reference to Figure 2, there is provided a motion tracking means 5 for a locomotion platform comprising a locomotion platform 10, at least one acoustic detection device 20, footware 90 worn by a user 15 using said locomotion platform 10 and at least one means 35 of interpreting signal from said at least one acoustic detection device 20, said interpretation influencing visual software driven by computer type hardware 40 and imaged by at least one imaging device 60, 80. Additionally and advantageously and with reference to Figure Sa and Figure 5b, there is provided in the surface of locomotion platform 10, embossed patterns 235 and with reference to Figure 6 embossments 232 and 234 differ from each other in different regions of locomotion platform 10 thereby producing different sound patterns when footware 90 slides across different regions. Difference in sound patterns enable feet location and direction to be interpreted by means 35 of interpreting signal from at least one acoustic device 20, 22, interpretation influencing visual software driven by a computer type hardware 40 and imaged by at least one imaging device 80, 60.

While various embodiments of the invention have been described the description is intended to be exemplary rather than limiting and it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible that are within the scope of the invention.

Accordingly the invention is not to be restricted except in the light of the attached claims supported

by the description herein.

Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

What we claim is: 1. A motion tracking means (5) for a locomotion platform (10) comprising a locomotion platform (10), at least one acoustic detection device (20), footware (90) worn by a user (15) using said locomotion platform (10) and at least one means (35) of interpreting signal from said at least one acoustic detection device (20), said interpretation influencing visual software driven by computer type hardware (40) and imaged by at least one imaging device (60, 80).
2. Footware (90) as claimed in claim 1 that generates sound when sliding on said locomotion platform (10).
3. Footware (90) as claimed in claim 2 wherein footware interface surface 440 differs between feet and generates different sound from each foot when sliding on said locomotion platform (10).
4. A locomotion platform (10) as claimed in claim 1 wherein said at least one acoustic detection device (20) is close to, attached mechanically to, adhesively attached or moulded to a surface of said locomotion platform (10).
5. A means of tracking motion (5) as claimed in claim 1 wherein said locomotion platform (10) is a single moulded piece and is substantially dish shaped (12).
6. A substantially dish shaped locomotion platform (10) as claimed in claim S made from a polymer exemplified by: PTFE, PET) ABS, HOPE, UHMWPE, PAG, PA66.
7. A dish as claimed in claim 6 wherein said dish comprises one or more formed sections wherein forming is exemplified by thermoforming or injection moulding
8. A motion tracking means (5) as claimed in claim 1 wherein output from said at least one acoustic detection device (20) provides motion control signal in accordance with those recognised by computer (40) driven by 2D or 3D visual software to achieve locomotion displayed by said at least one imaging device (60, 80).
9. At least one imaging device (60, 80) as claimed in claim 8 wherein said imaging device is emitting or projection screen technology (60) for one or more viewers, head mounted display (80) for an individual viewer or both.
10. A motion tracking means (5) as claimed in claim 8 wherein signal from said acoustic detection device (20) is amplified and interpreted by computer microphone audio card (35) and associated software.
11. A motion tracking means (5) as claimed in claim 1 wherein at least two acoustic detection devices (20, 22) are mounted on or close to a surface of said locomotion platform (10).
12. A motion tracking means (5) as claimed in claim 10 wherein at least one of said at least two acoustic detection devices (20, 22) is used for noise cancellation to remove sound generated by motion of footwear (90) on said locomotion platform (10)
13. A motion tracking means (5) as claimed in claim 10 wherein said at least two acoustic detection devices (20, 22) provide signal data input to said computer driven 2D or 3D visual software providing locomotion and direction of motion translation between said locomotion platform (10) and said visual software outputted to one or more screens (80, 60).
14. Top surface (200) of dish shaped locomotion platform (10) as claimed in claim 6 wherein positive (234) or negative (232) embossments (200) are embossed in dish surface (200).
15. A dish shaped locomotion platform (10) as claimed in claim 13 and footware (90) as claimed in claims 2 or 3 wherein said footware (90) produces sound patterns when sliding on said embossed patterns (200)
16. A motion tracking means (5) as claimed in claim 14 comprising a dish shaped locomotion platform (10), footware (90) and embossment patterns (232, 234) and at least one acoustic detection device (20) wherein said embossment patterns are different in different regions of said dish (10) producing different sound patterns when said footware (90) slides across said different regions, said different sound patterns enabling feet location and direction to be interpreted by way of said means (35) of interpreting signal from said at least one acoustic device (20, 22) said interpretation influencing visual software driven by a computer type hardware (40) and imaged by at least one imaging device (80, 60).