United States Patent [19]
`Kamen et al.
`
`US005701965A
`[11] Patent Number:
`[45] Date of Patent:
`
`5,701,965
`Dec. 30, 1997
`
`[54] HUMAN TRANSPORTER
`
`FOREIGN PATENT DOCUMENTS
`
`[75] Inventors: Dean L. Kamen. Bedford; Robert R.
`Ambrogi. Manchester; Robert J.
`Duggan. Northwood; Richard K.
`Heinzmann. Francestown', Brian R.
`Key. Pelham; Andrzej Skoskiewicz.
`Manchester; Phyllis K. Kristal,
`Sunapee. all of NH.
`
`[73]
`
`Assignee: Deka Products Limited Partnership.
`Manchester. NH.
`
`[2 1]
`[22]
`
`Appl. No.: 250,693
`Filed:
`May 27, 1994
`
`Related US. Application Data
`
`[63]
`
`[51]
`[52]
`
`[5 8]
`
`Continuation-impart of Ser. No. 21,789, Feb. 24, 1993,
`abandoned.
`
`1m. (31.6 ................................................... .. B62D 61/12
`US. Cl. ........................... .. 180/71; ISO/6.5; 18018.2;
`180/21; 180/658; 180/907; 280/526; 364/176;
`364/463
`Field of Search ............................. .. ISO/7.1. 8.2, 8.3.
`18018.5. 8.6. 65.1. 65.8. 907. 118. 6.48.
`6.5. 6.54. 41, 21; 901/1; 364/176. 463.
`424.05. 424.06. 434; 280/52. 5.26. 5.28.
`5.32. 6.1. 205. DIG. 10
`
`[5 6]
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`849,270 4/1907 Schafer et a1.
`2,742,973
`4/1956 Johannesen
`3,260,324
`7/1966 Saurez
`3,399,742
`9/1968 Malick
`3,515,401
`6/1970 Gross
`
`.......... .. 28015.26
`. 280/DIG. 10 X
`180/10
`180/21
`280/526
`
`3,596,298
`
`8/1971 Durst, Jr. . . . . . . .
`
`. . . . . . . . . .. 5/81
`
`280/266
`1/1975 Douglas et a1. ..... ..
`3,860,264
`180/65 R
`3/1975 Hickman et al
`3,872,945
`180/907
`4/1976 Uddeu etal
`3,952,822
`272/703
`4/1977 Deutsch ....... ..
`4,018,440
`4,062,558 12/1977 Wasserman ........................... .. 280/205
`
`Fm“
`
`(List continued on next page.)
`
`OTHER PUBLICATIONS
`
`Vos. D. “Dynamics and Nonlinear Adaptive Control of An
`Autonomous Unicycle”. Massachusetts Institute of Technol
`ogy. (1989).
`Vos. D. “Nonlinear Control of An Autonomous Unicycle
`Robot: Practical Issues". Massachusetts Institute of Tech
`nology. (1992).
`(List continued on next page.)
`
`Primary Examiner-—Anne Marie Boehler
`Attorney Agent, or Firm-Bromberg 8: Sunstein LLP
`[57]
`ABSTRACT
`
`There is provided. in a preferred embodiment. a device for
`transporting a human subject over ground having a surface
`that may be irregular and may include stairs. This embodi
`ment has a support for supporting the subject. A ground
`contacting module. movably attached to the support. serves
`to suspend the subject in the support over the surface. The
`orientation of the ground-contacting module de?nes fore-aft
`and lateral planes intersecting one another at a vertical. The
`support and the ground-contacting module are components
`of an assembly. Amotorized drive. mounted to the assembly
`and coupled to the ground-contacting module. causes loco
`motion of the assembly and the subject therewith over the
`surface. Finally. the embodiment has a control loop, in
`which the motorized drive is included. for dynamically
`enhancing stability in the fore-aft plane by operation of the
`motorized drive in connection with the ground-contacting
`module. The ground contacting module may be realized as
`a pair of ground-contacting members. laterally disposed
`with respect to one another. The ground-contacting members
`may be wheels. Alternatively. each ground-contacting mem
`ber may include a cluster of wheels. In another embodiment.
`each ground-contacting member includes a pair of axially
`adjacent and rotatably mounted arcuate element pairs.
`
`(List continued on next page.)
`
`54 Claims, 34 Drawing Sheets
`
`Swagway_1009
`
`

`
`5,701,965
`Page 2
`
`U S PATENT DCCUMENTS
`
`8/1978 Gabriel .................................... .. 180/21
`4,109,741
`9/1978 Haibeck
`280/793
`4,111,445
`4/1981 Fouchey, Jr
`230/5 26
`4,264,082
`43664527 5/1981 L‘mb“ --------- --
`130/8 3
`4,293,052 10/1981 Daswick et a].
`4,363,496 12/1982 Veneklasen
`135/67
`4,510,956
`4/1985 King ..... ..
`1110/65.]
`4,560,022 12/1985 Kassai
`..... .. 280/266
`4,657,272
`4/1987 Davmport ..
`.. 280/242 WC
`4,685,693
`8/1987 Vadjunec
`280/526
`4,709,772 12/1987 Brunet ...... ..
`280/11.l15
`4,740,001
`4/1988 Torleumke
`28011.13
`4,746,132
`5/1988 Eagan ...... ..
`272/703
`4,770,410
`9/1988 Brown
`280/221
`4,786,069 11/1988 Tang
`18018.1
`4,790,400 12/1988 Sheeter ..
`280/526
`4,790,548 12/1988 Decelles
`.... .. 280/526
`4,794,999
`1/1989 Hester
`180/907
`4,798,255
`1/1989 Wu .............. ..
`180/65 5
`4,802,542
`2/1989 Houston et a1. ..
`180/65 5
`4,809,804
`3/1989 Houston et a1. ..
`180/8.2
`4,834,200
`5/1989 Kajita ...... ..
`280/266
`4,863,182
`9/1989 Chem
`135/67
`4,867,188
`9/1989 Reid .... ..
`....... .. 135/67
`4,869,279
`9/1989 Hedges ..
`280/87021
`4,890,853
`l/1990 Olson .......... ..
`272/703
`4,953,851
`9/1990 Sherlock et a1. ..
`. 5/81 R
`4,985,947
`l/1991 Ethridge
`280/205
`5,002,295
`3/1991 Lin ...... ..
`280/221
`5,011,171
`4/1991 Cook
`ISO/8.6
`5,158,493 10/1992 Morgley
`180/8.l
`5,221,883
`6/1993 Takenaka et a]
`180/8.6
`5,241,875
`9/1993 Kochanneck
`280/DIG. 10
`5,248,007
`9/1993 Watkins
`280/205
`5,314,034
`5/1994 Chittal
`180/82
`5,350,033
`9/1994 Kraft
`5,366,036 11/1994 Perry ...................................... .. 180/6.5
`
`FOREIGN PATENT DOCUMENTS
`
`280/526
`4/1984 Japan
`59-73372
`0255580 12/1985 Japan ..................................... .. 180/86
`61-31685
`2/1986 Japan.
`0305082 1211988 Japan
`2-19m77 7/1990 Japan.
`2190277 7/1990 Japan ....................................... .. 901/1
`5-213240
`8/1993 Japan.
`
`1801209
`
`1213930 11/1970 United Kingdom ................ .. 280/526
`8605752 [0/1 986 MP0 ................................. .. 280/526
`W0 39/06117 7,1939 WIPO _
`
`OTHER PUBLICATIONS
`Koyanagi et al., “A Wheeled Inverse Pendulum Type Self
`Contained Mobile Robot and Its Posture Control and Vehicle
`Control”, The Society of Instrument and Control Engineers,
`Special issue of the 31st SICE Annual Conference. Japan
`(1992), pp. 13-16.
`Koyanagi et al, “A Wheeled Inverse Pendulum Type Self
`Contained Mobile Robot”, The Society of Instrument and
`Control Engineers, Special issue of the 31st SICE Annual
`Conference, Japan (1992), pp. 51-56.
`Koyanagi et al., “A Wheeled Inverse Pendulum Type Self
`Contained Mobile Robot and its Two Dimensional Trajec
`tory Control", Proceedings of the Second International
`Symposium on Measurement and Control in Robotics, Japan
`(1992), pp. 891-898.
`Watson Industries, Inc., Vertical Reference Manual
`ADS-C132-1A and ADS-C232-1A, (1992), pp. 3-4.
`News article “Amazing Wheelchair Goes Up and Down
`Stairs”.
`Schoonwinkel. A. “Design and Test of a Computer-Stabi
`lized Unicylce”, Stanford University (1988), UMI Disser
`tation Services.
`Osaka et al., “Stabilization of Unicyle”, Systems and Con
`trol, vol. 25. No. 3, Japan (1981). pp. 159-166 (Abstract
`only).
`Roy et al., “Five-Wheel Unicycle System". Medical 6:
`Biological Engineering dz Computing, vol. 23. N0. 6, United
`Kingdom (1985). pp. 593-596.
`Kawaji, 8., “Stabilization of Unicycle Using Spinning
`Motion”. Denki Gakkai Ronbushi, D, vol. 107. Issue 1.
`Japan (1987). pp. 21-28 (Abstract only).
`Schoonwiukel. A., “Design and Test of a Computer-Stabi
`lized Unicycle". Dissertation Abstracts International, vol.
`49/03-B, Stanford University (1988). pp. 890-1294
`(Abstract only).
`Vos et al., “Dynamics and Nonlinear Adaptive Control of an
`Autonomous Unicycle—Theory and Experiment". Ameri
`can Institute of Aeronautics and Astronautics, A90-26772
`10-39, Washington, DC. (1990). pp. 487-494 (Abstract
`only).
`
`Swagway_1009
`
`

`
`US. Patent
`
`Dec. 30, 1997
`
`Sheet 1 of 34
`
`5,701,965
`
`FIG.1
`
`Swagway_1009
`
`

`
`US. Patent
`
`Dec. 30, 1997
`
`Sheet 2 of 34
`
`5,701,965
`
`FIG.2
`
`Swagway_1009
`
`

`
`US. Patent
`
`Dec. 30, 1997
`
`Sheet 3 of 34
`
`5,701,965
`
`./ /
`./ .1».
`/ r
`
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`
`Swagway_1009
`
`

`
`US. Patent
`
`Dec. 30, 1997
`
`Sheet 4 0f 34
`
`5,701,965
`
`W
`
`Swagway_1009
`
`

`
`US. Patent
`
`Dec. 30, 1997
`
`Sheet 5 0f 34
`
`5,701,965
`
`~ USER INTERFACE
`55'
`
`as?“ Pm" SENSOR
`
`WHEEL ROTATION
`SENSORS
`
`563
`
`~ ACTUATOR
`554
`HETGHT SENSORS
`
`3v SWNEL SENSOR
`56
`
`STAIR DTMENSION
`SENSORS
`
`566
`
`512
`
`CONTROL
`SYSTEMS
`
`FIG.5
`
`531
`
`532
`
`541
`
`542
`
`LEFT WHEEL
`MOTOR DRIVE
`
`RIGHT WHEEL
`MOTOR DRIVE
`
`LEFT
`ACTUATOR
`
`RIGHT
`ACTUATOR
`
`SWIVEL
`M TO DRTVE
`o R
`
`Swagway_1009
`
`

`
`US. Patent
`
`Dec. 30, 1997
`
`Sheet 6 0f 34
`
`5,701,965
`
`51?
`
`PLANT
`
`6
`
`Swagway_1009
`
`

`
`US. Patent
`
`Dec. 30, 1997
`
`Sheet 7 of 34
`
`5,701,965
`
`FORWARD
`1
`
`LEFT TURN
`
`RIGHT TURN
`
`_
`
`&
`REVERSE
`
`Swagway_1009
`
`

`
`US. Patent
`
`Dec. 30, 1997
`
`Sheet 8 of 34
`
`5,701,965
`
`71'\_ RETRACT
`BOTH
`
`72
`\' READ SENSOR
`To DETERMINE
`STAIR HETDNT
`
`as
`I
`REIURN
`TD
`NEUTRAL
`
`752
`
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`
`76
`
`78?
`
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`-' DETERNTNED
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`SWIVEL TIL
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`
`Swagway_1009
`
`

`
`US. Patent
`
`Dec. 30, 1997
`
`Sheet 9 of 34
`
`5,701,965
`
`m .oE N8
`
`Swagway_1009
`
`

`
`US. Patent
`
`Dec. 30,
`
`1997
`
`Sheet 10 of 34
`
`5,701,965
`
`Swagway_1009
`
`

`
`US. Patent
`
`Dec. 30, 1997
`
`Sheet 11 of 34
`
`5,701,965
`
`~l'~--»94'1 a@ ‘TE 62
`
`I 101
`
`FIG14
`
`FIG.13
`
`Swagway_1009
`
`

`
`US. Patent
`
`Dec. 30, 1997
`
`Sheet 12 of 34
`
`5,701,965
`
`Swagway_1009
`
`

`
`US. Patent
`
`Dec. 30, 1997
`
`Sheet 13 0f 34
`
`5,701,965
`
`Swagway_1009
`
`

`
`US. Patent
`
`Dec. 30, 1997
`
`Sheet 14 of 34
`
`5,701,965
`
`Swagway_1009
`
`

`
`U.S. Patent
`
`Dec. 30, 1997
`
`Sheet 15 of 34
`
`5,701,965
`
`Swagway_1009
`
`Swagway_1009
`
`

`
`US. Patent
`
`Dec. 30, 1997
`
`Sheet 16 of 34
`
`5,701,965
`
`alll
`
`FIG. 24
`
`Swagway_1009
`
`

`
`US. Patent
`
`Dec. 30, 1997
`
`Sheet 17 of 34
`
`5,701,965
`
`252b
`2530
`
`‘[251 b
`
`2520
`zsmv
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`
`FIG. 26
`
`Swagway_1009
`
`

`
`US. Patent
`
`Dec. 30, 1997
`
`Sheet 18 0f 34
`
`5,701,965
`
`CENTRAL
`272 \_ MIOROOONTROLLER
`BOARO
`
`mm
`273\ INTERFACE
`ASSEMBLY
`
`279‘,
`
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`
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`
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`2770
`
`Swagway_1009
`
`

`
`U.S. Patent
`
`Dec. 30, 1997
`
`Sheet 19 of 34
`
`5,701,965
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`
`U.S. Patent
`
`Dec. 30, 1997
`
`Sheet 20 of 34
`
`5,701,965
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`
`U.S. Patent
`
`Dec. 30, 1997
`
`Sheet 21 of 34
`
`5,701,965
`
`GET TECHNICIANS INPUT
`IF ANY
`
`
`
`
`
`
`
`
`
`PERFORM TILT
`VELOCITY SIGNAL
`CALCULATIONS
`
`
`307
`
`303 I PERFORM ROLL I
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`vgmcm 51cm
`CALCULATIONS
`
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`CALCULATIONS
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`OUTPUT CONTROL
`SIGNALS
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`
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`
`
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`
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`
`MODIFY PROGRAM STATE
`BASED UPON NEW
`VARIABLE VALUES
`
`
`
`Ex" PROGRA“ ?
`
`309
`
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`
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`3042
`
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`AMPLIFIERS
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`swIIcIIEs & BUTTONS
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`
`THETA, XIII, Xc.
`
`306
`PERFORM WHEEL
`ETC.
`TORQUE SIGNAL
`CALCULATIONS
`UPDATE
`
`TECHN|CIAN'S
`DISPLAY
`
`301
`
`302
`
`303
`
`3011
`
`304
`
`Swagway_1009
`
`

`
`U.S. Patent
`
`Dec. 30, 1997
`
`Sheet 22 of 34
`
`5,701,965
`
`Swagway_1009
`
`Swagway_1009
`
`

`
`U.S. Patent
`
`Dec. 30, 1997
`
`Sheet 23 of 34
`
`5,701,965
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`
`U.S. Patent
`
`Dec. 30, 1997
`
`Sheet 24 of 34
`
`5,701,965
`
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`
`U.S. Patent
`
`Dec. 30, 1997
`
`Sheet 25 of 34
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`5,701,965
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`U.S. Patent
`
`Dec. 30, 1997
`
`Sheet 26 of 34
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`5,701,965
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`U.S. Patent
`
`Dec. 30, 1997
`
`Sheet 27 of 34
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`5,701,965
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`
`U.S. Patent
`
`Dec. 30, 1997
`
`Sheet 23 of 34
`
`5,701,965
`
`RUN/IDLE
`SWITCH PLACED
`IN IDLE POSITION.
`
`RUN/IDLE
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`Swagway_1009
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`U.S. Patent
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`Dec. 30, 1997
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`Sheet 29 of 34
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`Dec. 30, 1997
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`U.S. Patent
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`Dec. 30, 1997
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`U.S. Patent
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`Dec. 30, 1997
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`U.S. Patent
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`Dec. 30, 1997
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`U.S. Patent
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`Dec. 30, 1997
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`Sheet 34 of 34
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`Swagway_1009
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`Swagway_1009
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`

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`This application is a continuation in part of U.S. appli-
`cation Ser. No. 08/021,789. filed Feb. 24. 1993. now
`abandoned. which is hereby incorporated herein by refer-
`ence.
`
`TECHNICAL FIELD
`
`The present invention pertains to devices and methods for
`transporting human subjects. including those experiencing
`physical handicaps or incapacitation. and more particularly
`to devices and methods for transporting human subjects over
`regions that may include stairs.
`BACKGROUND ART
`
`10
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`A wide range of devices and methods are known for
`transporting human subjects experiencing physical incapaci-
`tation. The design of these devices has generally required a
`compromise to address the physical incapacity of the users.
`Stability has been deemed essential, so relative ease of
`locomotion is generally compromised. It becomes difficult
`to provide a self-propelled user-guidable device for t:rans-
`porting a physically handicapped or other person up and
`down stairs while still permitting convenient locomotion
`along regions that do not include stairs. Devices that achieve
`the climbing of stairs tend to be complex. heavy. and diflicult
`for ordinary locomotion.
`SUMMARY OF THE INVENTION
`
`20
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`25
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`The invention provides, in a preferred embodiment. a
`device for transporting a human subject over ground having
`a surface that may be irregular and may include stairs. This
`embodiment has a support for supporting the subject. A
`ground-contacting module. movably attached to the support,
`serves to suspend the subject in the support over the surface.
`The orientation of the ground-contacting module defines
`fore-aft and lateral planes intersecting one another at a
`vertical. The support and the ground-contacting module are
`components of an assembly. A motorized drive. mounted to
`the assembly and coupled to the ground-contacting module,
`causes locomotion of the assembly and the subject therewith
`over the surface. Finally. the embodiment has a control loop.
`in which the motorized drive is included. for dynamically
`enhancing stability in the fore-aft plane by operation of the
`motorized drive in connection with the ground-contacting
`module.
`
`In a further embodiment, the ground contacting module is
`realized as a pair of ground-contacting members, laterally
`disposed with respect to one another. The ground-contacting
`members may be wheels. Alternatively. each ground-
`contacting member may include a cluster of wheels, each
`cluster being rotatably mounted on and motor—driven about
`a common laterally disposed central axis; each of the wheels
`in each cluster may be rotatably mounted about an axis
`parallel to the central axis so that the distance from the
`central axis through a diameter of each wheel is approxi-
`mately the same for each of the wheels in the cluster. The
`wheels are motor-driven independently of the cluster.
`In yet another embodiment. each ground-contacting mem-
`ber includes a pair of axially adjacent and rotatably mounted
`arcuate element pairs. The arcuate elements of each element
`pair are disposed transversely at opposing ends of a support
`strut that is rotatably mounted at its midpoint. Each support
`strut is motor-driven.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`The invention will be more readily understood by refer-
`ence to the following description. taken with the accompa-
`nying drawings, in which:
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`1
`HUMAN TRANSPORTER
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`5,701,965
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`FIG. 1 is a perspective view of a simplified embodiment
`of the present invention. showing a subject seated thereon;
`FIG. 2 another perspective view of the embodiment of
`FIG. 1, showing further details of the embodiment;
`FIG. 3 is a schematic view of the embodiment of FIG. 1.
`showing the swivel arrangement of this embodiment;
`FIG. 4 is a side elevation of the embodiment of FIG. 1 as
`used for climbing stairs;
`FIG. 5 is a block diagram showing generally the nature of
`power and control with the embodiment of FIG. 1;
`FIG. 6 illustrates the control strategy for a simplified
`version of FIG. 1 to achieve balance using wheel torque;
`FIG. 7 illustrates diagrammatically the operation of joy-
`stick control of the wheels of the embodiments of FIG. 1;
`FIG. 8 illustrates the procedures utilized by the embodi-
`ment of FIG. 1 to ascend and descend stairs;
`FIGS. 9-21 illustrate embodiments of the invention uti-
`lizing a pair of wheel clusters as the ground-contacting
`members;
`FIGS. 9-10 show use of a two-wheel cluster design in
`various positions;
`FIGS. 11-21 show use of a tlrree—wheel cluster design in
`various positions and configurations;
`FIGS. 22-24 illustrate an embodiment wherein each
`ground-contacting member is realized as a plurality of
`axially adjacent and rotatably mounted arcuate element
`groups;
`FIGS. 25-26 provide mechanical detail of a three-wheel
`cluster design for use in the embodiment of FIGS. 18-20;
`FIG. 27 is a block diagra.m showing communication
`among the control assemblies used in the embodiment of
`FIGS. 18-20;
`FIG. 28 is a block diagram showing the structure of a
`generic control assembly of the type used in the embodiment
`of FIG. 27;
`FIG. 29 is a block diagram providing detail of the driver
`interface assembly 273 of FIG. 27;
`FIG. 30 is a logical flow diagram followed by the central
`microcontroller board 272 of FIG. 27 in the course of one
`control cycle;
`FIG. 31 illustrates variables defining the dimensions of
`the cluster design of FIGS. 11-26 and of a hypothetical stair
`with respect to which the cluster design will be used for
`ascent or descent;
`FIG. 32 illustrates angle variables pertinent to defining
`orientation of the cluster in relation to the device and to the
`world;
`FIG. 33 is a schematic of the wheel motor control during
`balancing and normal locomotion;
`FIG. 34 is a schematic of the cluster control arrangement
`during balancing and normal locomotion;
`FIG. 35 is a schematic, relating to FIG. 33. showing the
`arrangement by which the state variables indicating wheel
`position are determined so as to compensate for the effects
`of cluster rotation;
`FIGS. 36-38 illustrate the control arrangement for stair-
`climbing and obstacle traversal achieved by the cluster
`design of FIGS. 11-26 in accordance with a first embodi-
`ment permitting climbing;
`FIG. 36 is a schematic for the control arrangement for the
`cluster motors in the first embodiment permitting climbing.
`here employing a lean mode;
`FIG. 37 is a schematic for the control arrangement for the
`wheel motors in the first embodiment permitting climbing;
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`5,701,965
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`FIG. 38 is a block diagram of the state of the device,
`utilizing the first embodiment permitting climbing. for mov-
`ing among idle, lean. and balance modes;
`FIGS. 39A—B. 40A—B. 41A—B. and 42A—C illustrate
`stair-clirnbing achieved by the cluster design of FIGS. 11-26
`in accordance a second embodiment permitting climbing;
`FIGS. 39A and 39B illustrate orientation of the cluster in
`the sequence of starting stair climbing in accordance with
`the second climbing embodiment;
`FIGS. 40A and 40B illustrate orientation of the cluster in
`the sequence of resetting the angle origins in this embodi-
`ment;
`FIGS. 41A and 41B illustrate orientation of the cluster in
`the sequence of transferring weight in this embodiment;
`FIGS. 42A. 42B. and 42C illustrate orientation of the
`cluster in the sequence of climbing in this embodiment;
`FIG. 43 is a schematic for the control arrangement for the
`wheel and cluster motors during the start sequence of FIGS.
`39A and 39B;
`
`FIG. 44 is a schematic for the control arrangement for the
`wheel motors during the weight transfer sequence of FIGS.
`41A and 41B; and
`FIG. 45 is a schematic for the control arrangement during
`the climb sequence of FIGS. 42A. 42B. and 42C.
`DETAILED DESCRIPTION OF SPECIFIC
`EMBODIMENTS
`
`The invention may he implemented in a wide range of
`embodiments. A characteristic of many of these embodi-
`ments is the use of a pair of laterally disposed ground-
`contacting members to suspend the subject over the surface
`with respect to which the subject is being transported. The
`ground-contacting members are motor-driven.
`In many
`embodiments.
`the configuration in which the subject
`is
`suspended during locomotion lacks inherent stability at least
`a portion of the time with respect to a vertical in the fore-aft
`plane hut is relatively stable with respect to a vertical in the
`lateral plane. Fore-aft stability is achieved by providing a
`control loop, in which the motor is included. for operation of
`the motor in connection with the ground-contacting mem-
`bers. As described below, the pair of ground-contacting
`members may. for example. be a pair of wheels or a pair of
`wheel clusters. In the case of wheel clusters. each cluster
`may include a plurality of wheels. Each ground-contacting
`member. however, may instead be a plurality (typically a
`pair) of axially-adjacent. radially supported and rotatably
`mounted arcuate elements.
`In these embodiments,
`the
`ground-contacting members are driven by the motorized
`drive in the control loop in such a way as to maintain the
`center of mass of the device above the point of contact of the
`ground-contacting members with the ground, regardless of
`disturbances and forces operative on the device.
`In FIG. 1 is shown a simplified embodiment of the
`invention in which the principal ground-contacting members
`are a pair of wheels and in which supplemental ground-
`contacting members are used in stair climbing and descend-
`ing. (As will be shown below, stair climbing and descent and
`flat-terrain locomotion may both be achieved with a single
`set of ground-contacting members. when such members are
`the wheel clusters or the arcuate elements referred to above.)
`The embodiment shown in FIG. 1 includes a support
`arrangement 12. embodied here as a chair. on which a
`subject 13 may be seated. The device is provided with a pair
`of wheels 11 disposed laterally with respect to one another.
`The wheels help to define a series of axes including the
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`vertical axis Z-Z. a lateral axis Y—Y parallel to the axis of
`the wheels. and a fore-aft axis X-X perpendicular to the
`wheel axis. The plane defined by the vertical axis Z-Z and
`the lateral axis Y-Y will sometimes be referred to as the
`“lateral plane". and the plane defined by the fore-aft axis
`X-X and the vertical axis Z-Z will sometimes be referred to
`as the “fore-aft plane”. Directions parallel to the axes X-X
`and Y-Y are called the fore-aft and lateral directions respec-
`tively. It can be seen that the device. when relying on the pair
`of wheels 11 for contacting the ground,
`is inherently
`unstable with respect to a vertical in the fore-aft direction,
`but is relatively stable with respect to a vertical in the lateral
`direction.
`In FIG. 2 it can be seen that in addition to wheels 11, the
`device is provided with a pair of laterally disposed feet 21
`capable of being extended in the vertical direction by
`controllable amounts, and a footrest 22. The footrests are
`here provided with sensors for determining the height of
`objects such as stairs over which they may be disposed. The
`feet 21 are disposed on a pair of corresponding extendable
`legs 23. In a preferred embodiment. the device is stable in
`the fore-aft direction as well as the lateral direction when
`both feet are in contact with the ground, but lateral stability
`may be sacrificed when one foot is in contact with the
`ground.
`In FIG. 3 is shown an arrangement of the embodiment of
`of FIGS. 1 and 2 permitting swivel of the chair 12 with
`respect to the suspension system.
`including feet 21 and
`related legs 23. The swivel operates in a plane mat is
`approximately horizontal. The swivel arrangement. in com-
`binadon with the ability to extend and retract each leg,
`permits motion of the device up and down stairs in a manner
`analogous to human locomotion on stairs. Each leg 23. when
`serving as the weight-bearing leg. permits rotation of the
`remainder of the device about the leg’s vertical axis in the
`course of a swivel. In achieving the swivel. the chair pivots
`about a vertical axis disposed centrally between the legs 23
`to maintain the chair's forward-facing direction.
`Additionally. the non-weight-bearing leg 23 is rotated about
`its vertical axis in the course of a swivel to maintain its
`related foot 21 in a forward-facing direction.
`It can be seen that the embodiment described in FIGS. 1-3
`sacrifices inherent fore-aft stability in order to achieve
`relative mobility. For generally gradual surface changes, the
`balance mode involves providing fore-aft stability to an
`otherwise inherently unstable system For more irregular
`surfaces. such as stairs, this embodiment has a separate “step
`mode" used for climbing or descending stairs. Stability may
`be regained in climbing or descending stairs, for example,
`by using a hand to grab an ordinary handrail 41. as shown
`in FIG. 4, or even contacting an available wall near t:he
`stairs.
`
`In addition. a variety of strategies may be used to reduce
`the risk of injury arising from a fall. In one arrangement. in
`the event that a fall is determined to be about to occur, the
`device may enter a squat mode in which it controllably and
`quickly lowers the center of mass of the combination of
`device and human subject. A lowering of the center of mass
`may be achieved, for example. by hinging or separating the
`suspension system in such a manner as to cause the height
`of the chair from the surface to be reduced. A squat mode
`could also have the beneficial eifects of dissipating energy
`before imparting it to the subject. placing the subject in a
`position so as to reduce the subject’s vulnerability, and
`putting the subject in a position that is lower so as to reduce
`the energy transferred to the person in case of impact.
`In the block diagam of FIG. 5 it can be seen that a control
`system 51 is used to control the motor drives and actuators
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`of the embodiment of FIGS. 1-4 to achieve locomotion and
`balance. These include motor drives 531 and 532 for left and
`right wheels respectively. actuators 541 and 542 for left and
`right legs respectively, and swivel motor drive 55. The
`control system has data inputs including user interface 561.
`pitch sensor 562 for sensing fore-aft pitch, wheel rotation
`sensors 563. actuator height sensor 564, swivel sensor 565,
`and stair dimension sensor 566.
`
`A simplified control algorithm for acieving balance in the
`embodiment of the invention according to FIG. 1 when the
`wheels are active for locomotion is shown in the block
`diagram of FIG. 6. The plant 61 is equivalent
`to the
`equations of motion of a system with a ground contacting
`module driven by a single motor. before the control loop is
`applied. T identifies the wheel
`torque. The character 8
`identifies the fore—aft inclination (the pitch angle of the
`device with respect to gravity. i.e.. the vertical). X identifies
`the fore-aft displacement along the sm'face relative to the
`reference point. and the dot over a character denotes a
`variable diflerentiated with respect to time. The remaining
`portion of the figure is the control used to achieve balance.
`The boxes 62 and 63 indicate differentiation. To achieve
`dynamic control to insure stability of the system. and to keep
`the system in the neighborhood of a reference point on the
`surface. the wheel torque T in this embodiment is set to
`satisfy the following equation:
`r=K,e+K.e+K,X+K.x
`
`The gains K1. K2. K3, and K4 are dependent upon the
`physical parameters of the system and other effects such as
`gravity. The simplified control algorithm of FIG. 6 maintains
`balance and also proximity to the reference point on the
`surface in the presence of disturbances such as changes to
`the system’s center of mass with respect to the reference
`point on the sm'face due to body motion of the subject or
`contact with other persons or objects.
`In order to accommodate two wheels instead of the
`one-wheel system illustrated in FIG. 6, the torque desired
`from the left motor and the torque desired from the right
`motor can be calculated separately in the general manner
`described below in connection with FIG. 33. Additionally.
`tracking both the left wheel motion and the right wheel
`motion permits adjustments to be made to prevent unwanted
`turning of the device and to account for performance varia-
`tions between the two drive motors.
`A manual interface such as a joystick is used to adjust the
`torques of each motor. The joystick has axes indicated in
`FIG. 7. In operation of this embodiment. forward motions of
`the joystick is used to cause forward motion of the device,
`and reverse motion of the joystick causes backward motion
`of the device. A left turn similarly is accomplished by
`leftward motion of the joystick. For a right turn. thejoystick
`is moved to the right. The configuration used here permits
`the device to turn in place when the joystick is moved to the
`left or to the right. With respect to forward and reverse
`motion an alternative to the joystick is simply leaning
`forward or backward. since the pitch sensor (measuring 6)
`would identify a pitch change that the system would try to
`compensate for,
`leading to forward or reverse motion.
`depending on the direction of lean. Alternatively. control
`strategies based on fuzzy logic can be implemented.
`It can be seen that the approach of adjusting motor torques
`when in the wheel mode permits fore-aft stability to be
`achieved without
`the necessity of additional stabilizing
`wheels or struts (although such aids to stability may also be
`provided). In other words. stability is achieved dynamically.
`by motion of the components of the device (in this case
`constituting the entire device) relative to the ground.
`
`6
`
`Stair-Climbing with Legs
`FIG. 8 shows one manner of stair climbing and stair
`descending with the embodiment of FIG. 1. In confronting
`a stair, initially both legs are retracted (shown in block 71).
`and then the height of the first step is measured (block 72).
`A determination is made whether stair ascent or descent is to
`occur (73). (At this point. it is helpful. to achieve stability.
`for the subject to hold an available handrail.)
`Thereafter. in the first stage of stair ascent (shown in block
`74). a first leg is extended until the second leg clears the step
`(75). The device then swivels until the second leg is over the
`step it has just cleared (78). (In implementing this stage. it
`is possible to use