U.S. patent application number 10/044590 was filed with the patent office on 2002-05-30 for personal mobility vehicles and methods.
Invention is credited to Ambrogi, Robert R., Amsbury, Burl, Duggan, Robert J., Field, J. Douglas, Heinzmann, Richard Kurt, Kamen, Dean L., Langenfeld, Christopher C..
Application Number | 20020063006 10/044590 |
Document ID | / |
Family ID | 23270273 |
Filed Date | 2002-05-30 |
United States Patent
Application |
20020063006 |
Kind Code |
A1 |
Kamen, Dean L. ; et
al. |
May 30, 2002 |
Personal mobility vehicles and methods
Abstract
A class of transportation vehicles for carrying an individual
over ground having a surface that may be irregular. Various
embodiments have a motorized drive, mounted to the
ground-contacting module that causes operation of the vehicle in an
operating position that is unstable with respect to tipping when
the motorized drive arrangement is not powered. Related methods are
provided.
Inventors: |
Kamen, Dean L.; (Bedford,
NH) ; Ambrogi, Robert R.; (Manchester, NH) ;
Duggan, Robert J.; (Strafford, NH) ; Field, J.
Douglas; (Bedford, NH) ; Heinzmann, Richard Kurt;
(Francestown, NH) ; Amsbury, Burl; (Boulder,
CO) ; Langenfeld, Christopher C.; (Nashua,
NH) |
Correspondence
Address: |
BROMBERG & SUNSTEIN LLP
125 SUMMER STREET
BOSTON
MA
02110-1618
US
|
Family ID: |
23270273 |
Appl. No.: |
10/044590 |
Filed: |
January 11, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10044590 |
Jan 11, 2002 |
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09635936 |
Aug 10, 2000 |
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09635936 |
Aug 10, 2000 |
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09325978 |
Jun 4, 1999 |
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Current U.S.
Class: |
180/171 ;
180/65.1 |
Current CPC
Class: |
B60L 2200/16 20130101;
B60L 2240/461 20130101; B60L 15/20 20130101; B60L 2200/14 20130101;
B60L 2240/20 20130101; A63C 17/08 20130101; Y02T 10/72 20130101;
B60L 2240/463 20130101; B60L 2250/22 20130101; B62D 51/002
20130101; B62D 61/00 20130101; B62K 1/00 20130101; B60L 2250/12
20130101; B60L 2200/22 20130101; B62D 57/00 20130101; B62K 11/007
20161101; Y02T 10/64 20130101; A63C 17/01 20130101; A63C 17/12
20130101; B60L 2220/46 20130101; B62D 51/02 20130101; B60L 2240/423
20130101; B62D 37/00 20130101 |
Class at
Publication: |
180/171 ;
180/65.1 |
International
Class: |
B60K 031/18 |
Claims
What is claimed is:
1. A vehicle for carrying a payload including a user, the vehicle
comprising: a. a ground-contacting module including two
substantially coaxial wheels; b. a platform supporting the user in
a standing position substantially astride both wheels; and c. a
motorized drive arrangement, coupled to the ground-contacting
module; the drive arrangement, ground-contacting module and payload
comprising a system; the motorized drive arrangement causing, when
powered, automatically balanced operation of the system.
2. A vehicle for carrying a payload including a user, the vehicle
comprising: a. a platform which supports the user; b. a
ground-contacting module, to which the platform is mounted, which
propels the user in desired motion over an underlying surface; c. a
proximity sensor for determining the presence of the user on the
device; and d. a safety switch, coupled to the proximity detector,
for inhibiting operation of the ground-contacting module unless the
proximity sensor has determined the presence of the user on the
device.
3. A device according to claim 2, wherein the proximity sensor is a
member, mechanically coupled to the safety switch, having an
operating position and a non-operating position, wherein the member
is in the non-operating position in the absence of the user from
the device and the member is moveable to the operating position
when the user is on the device.
4. A device according to claim 3, wherein the member includes a
plate, disposed on the device, for receiving a foot of the user,
and wherein placement of the foot on the plate causes it to move
into the operating position.
5. A device according to claim 2, wherein the proximity detector is
electronic.
6. A device according to claim 2, wherein the proximity detector
includes a semiconductor device.
7. A device according to claim 2, further comprising: d. a
motorized drive arrangement, coupled to the ground-contacting
module; the motorized drive arrangement causing, when powered,
automatically balanced and stationary operation of the device
unless the proximity sensor has determined the presence of the user
on the device.
8. A vehicle for carrying a payload including a user, the vehicle
comprising: a. a platform which supports the user; b. a
ground-contacting module, to which the platform is mounted, which
propels the user in desired motion over an underlying surface; c. a
motorized drive arrangement, coupled to the ground-contacting
module; the drive arrangement, ground-contacting module and payload
comprising a system being unstable with respect to tipping when the
motorized drive is not powered; the motorized drive arrangement
causing, when powered, automatically balanced operation of the
system wherein the motorized drive arrangement has a present power
output and a specified maximum power output and, in operation, has
balancing margin determined by the difference between the maximum
power output and the present power output of the drive arrangement;
d. a balancing margin monitor, coupled to the motorized drive
arrangement, for generating a signal characterizing the balancing
margin; and e. an alarm, coupled to the balancing margin monitor,
for receiving the signal characterizing the balancing margin and
for warning when the balancing margin falls below a specified
limit.
9. A device according to claim 8, wherein the alarm includes ripple
modulation of the power output of the motorized drive
arrangement.
10. A device according to claim 8, wherein the alarm is
audible.
11. A device for carrying a payload including a user, the device
comprising: a. a platform which supports the user in a standing
position, b. a ground-contacting module, mounted to the platform,
including at least one ground-contacting member and defining a
fore-aft plane; c. a motorized drive arrangement, coupled to the
ground-contacting module; the drive arrangement, ground-contacting
module and payload comprising a system being unstable with respect
to tipping when the motorized drive is not powered; the motorized
drive arrangement causing, when powered, automatically balanced
operation of the system in an operating position that is unstable
with respect to tipping in at least a fore-aft plane when the
motorized drive arrangement is not powered; d. a user-operated mode
control having first and second modes; e. a user input control that
receives an indication from the user of one of (i) a specified
pitch of the device under conditions of motion at uniform velocity
and (ii) steering command, depending on the mode of the mode
control.
12. A device for carrying a payload including a user, the device
comprising: a. a platform which supports the user in a standing
position, b. a ground-contacting module, mounted to the platform,
including a plurality of laterally disposed ground-contacting
members and defining a fore-aft plane; c. a motorized drive
arrangement, coupled to the ground-contacting module; the drive
arrangement, ground-contacting module and payload comprising a
system being unstable with respect to tipping when the motorized
drive is not powered; the motorized drive arrangement causing, when
powered, automatically balanced operation of the system in an
operating position that is unstable with respect to tipping in at
least a fore-aft plane when the motorized drive arrangement is not
powered; and d. a user drive mode selector that on indication from
the user causes the motorized drive to operate the
ground-contacting members at a uniform user-controllable speed so
as to permit a dismounted user to guide the vehicle running under
its own power.
13. A vehicle for carrying a user, the user being a standing
person, the vehicle comprising: a. a ground-contacting module which
supports a payload including the standing person, the
ground-contacting module contacting an underlying surface
substantially at a single region of contact; and b. a motorized
drive arrangement, coupled to the ground-contacting module; the
drive arrangement, ground-contacting module and payload comprising
a system being unstable with respect to tipping when the motorized
drive is not powered; the motorized drive arrangement causing, when
powered, automatically balanced operation of the system.
14. A vehicle in accordance with claim 13, the ground-contacting
module including a uniball.
15. A method of using a vehicle to carry a user, the user being a
standing person, the method comprising: a. standing on a platform
that supports a payload including a standing person, the platform
mounted to a ground-contacting module including two substantially
coaxial wheels; and b. operating a motorized drive arrangement,
coupled to the ground-contacting module; the drive arrangement,
ground-contacting module and payload comprising a system being
unstable with respect to tipping when the motorized drive is not
powered; the motorized drive arrangement causing, when powered,
automatically balanced operation of the system.
16. A method of using a vehicle to carry a payload including a
user, the method comprising: a. standing on a platform supporting
the user, the platform mounted to a ground-contacting module, which
propels the user in desired motion over an underlying surface; b.
using a proximity sensor to determine the presence of the user on
the device; and c. inhibiting operation of the ground-contacting
module unless the proximity sensor has determined the presence of
the user on the device.
17. A method according to claim 16, wherein the proximity sensor is
a member, having an operating position and a non-operating
position, wherein the member is in the non-operating position in
the absence of the user from the device and the member is moveable
to the operating position when the user is on the platform.
18. A method according to claim 17, wherein the member includes a
plate, disposed on the device, for receiving a foot of the user,
and wherein placement of the foot on the plate causes it to move
into the operating position.
19. A method according to claim 17, wherein the proximity detector
is electronic.
20. A method according to claim 17, wherein the proximity detector
includes a semiconductor device.
21. A method according to claim 17, further comprising: d.
operating a motorized drive arrangement, coupled to the
ground-contacting module; the motorized drive arrangement causing,
when powered, automatically balanced and stationary operation of
the device unless the proximity sensor has determined the presence
of the user on the device.
22. A method of using a vehicle to carry a payload including a
user, the method comprising: a. standing on a platform supporting
the user, the platform mounted to a ground-contacting module, which
propels the user in desired motion over an underlying surface; b.
operating a motorized drive arrangement, coupled to the
ground-contacting module; the drive arrangement, ground-contacting
module and payload comprising a system being unstable with respect
to tipping when the motorized drive is not powered; the motorized
drive arrangement causing, when powered, automatically balanced
operation of the system wherein the motorized drive arrangement has
a present power output and a specified maximum power output and, in
operation, has balancing margin determined by the difference
between the maximum power output and the present power output of
the drive arrangement; c. monitoring the balancing margin and
generating a signal characterizing the balancing margin; and d.
receiving the signal characterizing the balancing margin and
generating an alarm to warn when the balancing margin falls below a
specified limit.
23. A method according to claim 22, wherein the alarm includes
ripple modulation of the power output of the motorized drive
arrangement.
24. A method according to claim 22, wherein the alarm is
audible.
25. A method for carrying a payload including a user, the method
comprising: a. assuming a position on a platform which supports a
payload including the user, the platform being coupled to a
ground-contacting module, the module including at least one
ground-contacting member and defining a fore-aft plane; b.
operating a motorized drive arrangement, coupled to the
ground-contacting module; the drive arrangement, ground-contacting
module and payload comprising a system being unstable with respect
to tipping when the motorized drive is not powered; the motorized
drive arrangement causing, when powered, automatically balanced
operation of the system in an operating position that is unstable
with respect to tipping in at least a fore-aft plane when the
motorized drive arrangement is not powered; and c. operating a
user-operated mode control to select one of first and second modes;
d. providing via a user input control an indication of one of (i) a
specified pitch of the device under conditions of motion at uniform
velocity and (ii) steering command, depending on whether the first
mode or the second mode has been selected.
26. A method for carrying a payload including a user, the method
comprising: a. providing a device having i. a platform which
supports the user in a standing position, ii. a ground-contacting
module, mounted to the platform, including a plurality of laterally
disposed ground-contacting members and defining a fore-aft plane;
iii. a motorized drive arrangement, coupled to the
ground-contacting module; the drive arrangement, ground-contacting
module and payload comprising a system being unstable with respect
to tipping when the motorized drive is not powered; the motorized
drive arrangement causing, when powered, automatically balanced
operation of the system in an operating position that is unstable
with respect to tipping in at least a fore-aft plane when the
motorized drive arrangement is not powered; and b. causing the
motorized drive to operate the ground-contacting members at a
user-controllable speed so as to permit a dismounted user to guide
the vehicle running under its own power.
27. A method of using a vehicle to carry a user, the user being a
standing person, the method comprising: a. standing on a
ground-contacting module which supports a payload including a
person standing thereon, the ground-contacting module contacting an
underlying surface substantially at a single region of contact; and
b. operating a motorized drive arrangement, coupled to the
ground-contacting module; the drive arrangement, ground-contacting
module and payload comprising a system being unstable with respect
to tipping when the motorized drive is not powered; the motorized
drive arrangement causing, when powered, automatically balanced
operation of the system.
28. A method in accordance with claim 27, wherein the
ground-contacting module includes a uniball.
Description
[0001] The present application is a divisional application of
copending application Ser. No. 09/635,936, filed Aug. 10, 2000, now
allowed, which is a divisional application of application Ser. No.
09/325,978, filed Jun. 4, 1999, now issued as U.S. Pat. No.
6,302,230, which are all incorporated herein by reference.
TECHNICAL FIELD
[0002] The present invention pertains to vehicles and methods for
transporting individuals, and more particularly to balancing
vehicles and methods for transporting individuals over ground
having a surface that may be irregular.
BACKGROUND ART
[0003] A wide range of vehicles and methods are known for
transporting human subjects. Typically, such vehicles rely upon
static stability, being designed so as to be stable under all
foreseen conditions of placement of their ground-contacting
members. Thus, for example, the gravity vector acting on the center
of gravity of an automobile passes between the points of ground
contact of the automobile's wheels, the suspension keeping all
wheels on the ground at all times, and the automobile is thus
stable. Another example of a statically stable vehicle is the
stair-climbing vehicle described in U.S. Pat. No. 4,790,548
(Decelles et al.).
SUMMARY OF THE INVENTION
[0004] In one embodiment there is provided a vehicle for carrying a
user. In this case, the user is a standing person. The vehicle of
this embodiment includes:
[0005] a. a ground-contacting module which supports a payload
including the standing person, the ground-contacting module
contacting an underlying surface substantially at a single region
of contact; and
[0006] b. a motorized drive arrangement, coupled to the
ground-contacting module; the drive arrangement, ground-contacting
module and payload comprising a system; the motorized drive
arrangement causing, when powered, automatically balanced operation
of the system.
[0007] In a related embodiment, the ground-contacting module
includes a uniball.
[0008] In another embodiment, there is provide a vehicle for
carrying a payload including a user.
[0009] The vehicle of this embodiment includes:
[0010] a. a ground-contacting module including two substantially
coaxial wheels;
[0011] b. a platform supporting the user in a standing position
substantially astride both wheels; and
[0012] c. a motorized drive arrangement, coupled to the
ground-contacting module; the drive arrangement, ground-contacting
module and payload comprising a system; the motorized drive
arrangement causing, when powered, automatically balanced operation
of the system.
[0013] In another embodiment, there is provided a vehicle for
carrying a payload including a user, and the vehicle of this
embodiment includes:
[0014] a. a platform which supports the user;
[0015] b. a ground-contacting module, to which the platform is
mounted, which propels the user in desired motion over an
underlying surface;
[0016] c. a proximity sensor for determining the presence of the
user on the device; and
[0017] d. a safety switch, coupled to the proximity detector, for
inhibiting operation of the ground-contacting module unless the
proximity sensor has determined the presence of the user on the
device.
[0018] The proximity sensor may be a member, mechanically coupled
to the safety switch, having an operating position and a
non-operating position, wherein the member is in the non-operating
position in the absence of the user from the device and the member
is moveable to the operating position when the user is on the
device. The member may include a plate, disposed on the device, for
receiving a foot of the user, wherein placement of the foot on the
plate causes it to move into the operating position. Alternatively,
the proximity detector may be electronic and may include a
semiconductor device. In a further related embodiment, the device
may include a motorized drive arrangement, coupled to the
ground-contacting module; the motorized drive arrangement causing,
when powered, automatically balanced and stationary operation of
the device unless the proximity sensor has determined the presence
of the user on the device.
[0019] In another embodiment, there is provided a vehicle for
carrying a payload including a user. The vehicle of this embodiment
includes:
[0020] a. a platform which supports the user;
[0021] b. a ground-contacting module, to which the platform is
mounted, which propels the user in desired motion over an
underlying surface;
[0022] c. a motorized drive arrangement, coupled to the
ground-contacting module; the drive arrangement, ground-contacting
module and payload comprising a system; the motorized drive
arrangement causing, when powered, automatically balanced operation
of the system wherein the motorized drive arrangement has a present
power output and a specified maximum power output and, in
operation, has balancing margin determined by the difference
between the maximum power output and the present power output of
the drive arrangement;
[0023] d. a balancing margin monitor, coupled to the motorized
drive arrangement, for generating a signal characterizing the
balancing margin; and
[0024] e. an alarm, coupled to the balancing margin monitor, for
receiving the signal characterizing the balancing margin and for
warning when the balancing margin falls below a specified
limit.
[0025] The alarm may include ripple modulation of the power output
of the motorized drive arrangement, and alternatively, or in
addition, may be audible.
[0026] In a still further embodiment there is provided a device for
carrying a user, and the device includes:
[0027] a. a platform which supports a payload including the
user,
[0028] b. a ground-contacting module, mounted to the platform,
including at least one ground-contacting member and defining a
fore-aft plane;
[0029] c. a motorized drive arrangement, coupled to the
ground-contacting module; the drive arrangement, ground-contacting
module and payload comprising a system; the motorized drive
arrangement causing, when powered, automatically balanced operation
of the system in an operating position that is unstable with
respect to tipping in at least a fore-aft plane when the motorized
drive arrangement is not powered; and
[0030] d. a user input control that receives an indication from the
user of a specified pitch of the device under conditions of motion
at uniform velocity.
[0031] The user input control may include a thumb-wheel disposed
upon a handle that is part of the device. A related embodiment
provides a device for carrying a payload including a user, and the
device includes:
[0032] a. a platform which supports the user in a standing
position,
[0033] b. a ground-contacting module, mounted to the platform,
including at least one ground-contacting member and defining a
fore-aft plane;
[0034] c. a motorized drive arrangement, coupled to the
ground-contacting module; the drive arrangement, ground-contacting
module and payload comprising a system; the motorized drive
arrangement causing, when powered, automatically balanced operation
of the system in an operating position that is unstable with
respect to tipping in at least a fore-aft plane when the motorized
drive arrangement is not powered;
[0035] d. a user-operated mode control having first and second
modes;
[0036] e. a user input control that receives an indication from the
user of one of (i) a specified pitch of the device under conditions
of motion at uniform velocity and (ii) steering command, depending
on the mode of the mode control.
[0037] In yet another embodiment there is provided a device for
carrying a payload including a user, and in this embodiment the
device includes:
[0038] a. a platform which supports the user in a standing
position,
[0039] b. a ground-contacting module, mounted to the platform,
including a plurality of laterally disposed ground-contacting
members and defining a fore-aft plane;
[0040] c. a motorized drive arrangement, coupled to the
ground-contacting module; the drive arrangement, ground-contacting
module and payload comprising a system; the motorized drive
arrangement causing, when powered, automatically balanced operation
of the system in an operating position that is unstable with
respect to tipping in at least a fore-aft plane when the motorized
drive arrangement is not powered; and
[0041] d. a user drive mode selector that on indication from the
user causes the motorized drive to operate the ground-contacting
members at a uniform user-controllable speed so as to permit a
dismounted user to guide the vehicle running under its own
power.
[0042] The invention provides methods corresponding to embodiments
of the general nature described above. In one embodiment, there is
provided a method of using a vehicle to carry a user and this
method includes:
[0043] a. standing on a ground-contacting module which supports a
payload including a person standing thereon, the ground-contacting
module contacting an underlying surface substantially at a single
region of contact; and
[0044] b. operating a motorized drive arrangement, coupled to the
ground-contacting module; the drive arrangement, ground-contacting
module and payload comprising a system; the motorized drive
arrangement causing, when powered, automatically balanced operation
of the system.
[0045] In a related embodiment, the ground-contacting module may
include a uniball.
[0046] In another embodiment, there is provided a method of using a
vehicle to carry a user, and in this embodiment, the method
includes:
[0047] a. standing on a platform that supports a payload including
a standing person, the platform mounted to a ground-contacting
module including two substantially coaxial wheels; and
[0048] b. operating a motorized drive arrangement, coupled to the
ground-contacting module; the drive arrangement, ground-contacting
module and payload comprising a system; the motorized drive
arrangement causing, when powered, automatically balanced operation
of the system.
[0049] In another embodiment, there is provided a method of using a
vehicle to carry a payload including a user, and the method of this
embodiment includes:
[0050] a. standing on a platform supporting the user, the platform
mounted to a ground-contacting module, which propels the user in
desired motion over an underlying surface;
[0051] b. using a proximity sensor to determine the presence of the
user on the device; and
[0052] c. inhibiting operation of the ground-contacting module
unless the proximity sensor has determined the presence of the user
on the device.
[0053] As in the corresponding device, discussed above, the
proximity sensor may be a member, mechanically coupled to the
safety switch, having an operating position and a non-operating
position, wherein the member is in the non-operating position in
the absence of the user from the device and the member is moveable
to the operating position when the user is on the device. The
member may include a plate, disposed on the device, for receiving a
foot of the user, wherein placement of the foot on the plate causes
it to move into the operating position. Alternatively, the
proximity detector may be electronic and may include a
semiconductor device. A further embodiment of the method includes
operating a motorized drive arrangement, coupled to the
ground-contacting module; the motorized drive arrangement causing,
when powered, automatically balanced and stationary operation of
the device unless the proximity sensor has determined the presence
of the user on the device.
[0054] Yet another emobodiment, provides a method of using a
vehicle to carry a payload including a user, and the method of this
embodiment includes:
[0055] a. standing on a platform supporting the user, the platform
mounted to a ground-contacting module, which propels the user in
desired motion over an underlying surface;
[0056] b. operating a motorized drive arrangement, coupled to the
ground-contacting module; the drive arrangement, ground-contacting
module and payload comprising a system; the motorized drive
arrangement causing, when powered, automatically balanced operation
of the system wherein the motorized drive arrangement has a present
power output and a specified maximum power output and, in
operation, has balancing margin determined by the difference
between the maximum power output and the present power output of
the drive arrangement;
[0057] c. monitoring the balancing margin and generating a signal
characterizing the balancing margin; and
[0058] d. receiving the signal characterizing the balancing margin
and generating an alarm to warn when the balancing margin falls
below a specified limit.
[0059] Alternatively, the balancing margin may be determined by the
difference between a specified maximum velocity of the vehicle and
the current velocity of the vehicle. The alarm may include ripple
modulation of the power output of the motorized drive arrangement,
and alternatively, or in addition, may be audible.
[0060] Another embodiment provides a method for carrying a user,
and the method includes:
[0061] a. assuming a position on a platform which supports a
payload including the user, the platform being coupled to a
ground-contacting module, the module including at least one
ground-contacting member and defining a fore-aft plane;
[0062] b. operating a motorized drive arrangement, coupled to the
ground-contacting module; the drive arrangement, ground-contacting
module and payload comprising a system; the motorized drive
arrangement causing, when powered, automatically balanced operation
of the system in an operating position that is unstable with
respect to tipping in at least a fore-aft plane when the motorized
drive arrangement is not powered; and
[0063] c. providing via a user input control an indication from the
user of a specified pitch of the device under conditions of motion
at uniform velocity.
[0064] The user input control may include a thumb-wheel disposed
upon a handle coupled to the platform.
[0065] Yet another embodiment provides a method for carrying a
payload including a user, and the method of this embodiment
includes:
[0066] a. assuming a position on a platform which supports a
payload including the user, the platform being coupled to a
ground-contacting module, the module including at least one
ground-contacting member and defining a fore-aft plane;
[0067] b. operating a motorized drive arrangement, coupled to the
ground-contacting module; the drive arrangement, ground-contacting
module and payload comprising a system; the motorized drive
arrangement causing, when powered, automatically balanced operation
of the system in an operating position that is unstable with
respect to tipping in at least a fore-aft plane when the motorized
drive arrangement is not powered; and
[0068] c. operating a user-operated mode control to select one of
first and second modes;
[0069] d. providing via a user input control an indication of one
of (i) a specified pitch of the device under conditions of motion
at uniform velocity and (ii) steering command, depending on whether
the first mode or the second mode has been selected.
[0070] Another embodiment provides a method for carrying a payload
including a user, and the embodiment includes:
[0071] a. providing a device having
[0072] i. a platform which supports the user in a standing
position,
[0073] ii. a ground-contacting module, mounted to the platform,
including a plurality of laterally disposed ground-contacting
members and defining a fore-aft plane;
[0074] iii. a motorized drive arrangement, coupled to the
ground-contacting module; the drive arrangement, ground-contacting
module and payload comprising a system; the motorized drive
arrangement causing, when powered, automatically balanced operation
of the system in an operating position that is unstable with
respect to tipping in at least a fore-aft plane when the motorized
drive arrangement is not powered; and
[0075] b. causing the motorized drive to operate the
ground-contacting members at a user-controllable speed so as to
permit a dismounted user to guide the vehicle running under its own
power.
BRIEF DESCRIPTION OF THE DRAWINGS
[0076] The invention will be more readily understood by reference
to the following description, taken with the accompanying drawings,
in which:
[0077] FIG. 1 is a side view of a personal vehicle lacking a stable
static position, in accordance with a preferred embodiment of the
present invention, for supporting or conveying a subject who
remains in a standing position thereon;
[0078] FIG. 2 is a perspective view of a further personal vehicle
lacking a stable static position, in accordance with an alternate
embodiment of the present invention;
[0079] FIG. 3 illustrates the control strategy for a simplified
version of FIG. 1 to achieve balance using wheel torque;
[0080] FIG. 4 illustrates diagrammatically the operation of
joystick control of the wheels of the embodiment of FIG. 1;
[0081] FIG. 5 is a block diagram showing generally the nature of
sensors, power and control with the embodiment of FIG. 1;
[0082] FIG. 6 is a block diagram providing detail of a driver
interface assembly;
[0083] FIG. 7 is a schematic of the wheel motor control during
balancing and normal locomotion, in accordance with an embodiment
of the present invention;
[0084] FIG. 8 shows a balancing vehicle with a single wheel central
to the support platform of the vehicle and an articulated handle in
accordance with an embodiment of the present invention;
[0085] FIG. 9 shows a balancing vehicle with a single wheel central
to the support platform of the vehicle and a handle in accordance
with an embodiment of the present invention;
[0086] FIG. 10 shows a balancing vehicle with two coaxial wheels
central to the support platform of the vehicle and an articulated
handle in accordance with an embodiment of the present
invention;
[0087] FIG. 11 shows a balancing vehicle with a single wheel
central to the support platform of the vehicle and no handle in
accordance with an embodiment of the present invention;
[0088] FIG. 12 shows an alternate embodiment of a balancing vehicle
with a single wheel central to the support platform of the vehicle
and no handle in accordance with an embodiment of the present
invention;
[0089] FIG. 13 shows a balancing vehicle with a single wheel
transversely mounted central to the support platform of the vehicle
and no handle in accordance with an embodiment of the present
invention;
[0090] FIG. 14 shows a balancing vehicle with a single wheel
transversely mounted central to the support platform of the vehicle
and a handle in accordance with an embodiment of the present
invention;
[0091] FIG. 15 shows a balancing vehicle with a uniball mounted
central to the support platform of the vehicle and a handle in
accordance with an embodiment of the present invention; and
[0092] FIG. 16 shows an illustrative diagram of an idealized
balancing vehicle with a rigid wheel in motion at a constant
velocity across a flat surface.
DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS
[0093] The subject matter of this application is related to that of
U.S. application Ser. No. 08/479,901, filed Jun. 7, 1995, now
issued as U.S. Pat. No. 5,975,225, which is a continuation in part
of U.S. application Ser. No. 08/384,705, filed Feb. 3, 1995, now
issued as U.S. Pat. No. 5,971,091, which is a continuation in part
of U.S. application Ser. No. 08/250,693, filed May 27, 1994, now
issued as U.S. Pat. No. 5,701,965, which in turn is a continuation
in part of U.S. application Ser. No. 08/021,789, filed Feb. 24,
1993, now abandoned. Each of these related applications is
incorporated herein by reference in its entirety.
[0094] An alternative to operation of a statically stable vehicle
is that dynamic stability may be maintained by action of the user,
as in the case of a bicycle or motorcycle or scooter, or, in
accordance with embodiments of the present invention, by a control
loop, as in the case of the human transporter described in U.S.
Pat. No. 5,701,965. The invention may be implemented in a wide
range of embodiments. A characteristic of many of these embodiments
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 or other
surface, such as a floor, over which a vehicle in accordance with
the invention is employed may be referred to generally herein as
the "ground." The ground-contacting members are typically
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 but is relatively stable with respect to a vertical
in the lateral plane.
[0095] Some embodiments of the invention invoke the concept of
primary wheels. The term "primary wheels," as used in this
description and in any appended claims, refers to a minimum set of
a vehicle's wheels on which the vehicle is capable of operating
stably. More generally, the term "primary ground-contacting
members" allows for a more general class of members, that includes
but is not limited to wheels. Hence, as used in this description
and in any appended claims, "primary ground-contacting members"
refers to a minimum set of a vehicle's ground-contacting members on
which the vehicle is capable of operating stably. Other
ground-contacting members may include, without limitation: arcuate
sections of a wheel, clusters of wheels, treads, etc.
[0096] In various embodiments of the invention, fore-aft stability
may be achieved by providing a control loop, in which one or more
motors are included, for operation of a motorized drive in
connection with the ground-contacting members. As described below,
a 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, when the vehicle is not
in locomotion, the center of mass of the vehicle above the region
of contact of the ground-contacting members with the ground,
regardless of disturbances and forces operative on the vehicle.
[0097] A ground-contacting member typically has a "point"
(actually, a region) of contact or tangency with the surface over
which the vehicle is traveling or standing. Due to the compliance
of the ground-contacting member, the "point" of contact is actually
an area, where the region of contact may also be referred to as a
contact patch. The weight of the vehicle is distributed over the
contact region, giving rise to a distribution of pressures over the
region, with the center of pressure displaced forward during
forward motion. The distribution of pressures is a function both of
the composition and structure of the wheel, the rotational velocity
of the wheel, the torque applied to the wheel, and thus of the
frictional forces acting on the wheel.
[0098] A force in the direction of motion is required to overcome
rolling friction (and other frictional forces, including air
resistance). Gravity may be used, in accordance with preferred
embodiments of the invention, to provide a torque about the point
of contact with the surface in a direction having a component in
the sense of desired motion. Referring to FIG. 16, to illustrate
these principles, a diagram is shown of the forces acting on a
vehicle that locomotes with constant velocity v on a single wheel
over a flat surface. The principles now discussed may readily be
generalized to operation on a sloped surface and to accommodate any
other external forces that might be present. Wheel 160 of radius
R.sub.w rotates with respect to chassis 162 about axle 164 and
contacts the underlying surface at point P. For purposes of
illustration only, it is assumed that wheel 160 contacts the
surface at a point.
[0099] The wheel is driven with respect to the vehicle by a torque
T (supplied by a motor, for example) which in turn creates a
reaction torque -T on the vehicle. Since the torque acts about the
axle 164, the reaction torque corresponds to a force F.sub.b acting
at the center of gravity (CG) of the system, including the vehicle
and payload, where F.sub.b=T/R.sub.CG, where R.sub.CG is the
distance between the axle and the CG of the system. The line 170
from the CG to point P is at an angle .theta..sub.s relative to the
vertical 172.
[0100] The rolling friction, f, acting on the wheel at point P, is
proportional to the velocity v of the rim of the wheel, with the
proportionality expressed as f=.mu.v. For constant velocity to be
maintained, this force f must be exactly canceled. Consequently,
with gravity providing the force, the condition that must be
satisfied is:
f.sub.ccos.theta..sub.s=f, (Eqn. 1)
[0101] where f.sub.b is the component of the reaction force acting
transverse to axis 174 between the CG and point P. In order to
prevent the vehicle from falling, a stability condition must also
exist, namely that no net force acts on the CG in a direction
transverse to line 170, i.e., there is no net torque about the
point of contact P during motion at constant velocity (i.e., in an
inertial frame of reference where the point P is fixed). This
condition may be expressed as:
F.sub.gsin.theta..sub.s=f.sub.b, (Eqn. 2)
[0102] where F.sub.gsin.theta..sub.s is the "tipping" component of
gravity, and f.sub.b is the counter-tipping component of the
reactive force on the vehicle caused by wheel rotation
(f.sub.b=F.sub.bcos.gamma.)- , and where .gamma. is the angle shown
line 170 and line 174.
[0103] Eqns. 1 and 2 may be combined to yield
F.sub.gsin.theta..sub.scos.t- heta..sub.s=f=.mu.v, thus, in the
limit of small angles (where sin .theta..apprxeq..theta.),
.theta..sub.s.apprxeq.(.mu./F.sub.g)v, (Eqn. 3)
[0104] showing that increasing velocity requires increased lean to
overcome the effects of friction. Additionally, a control loop that
imposes stability on the system will respond to an increased lean
by increasing velocity of the system. While the preceding
discussion assumed constant velocity, additional lean beyond that
required to overcome the effects of friction will result in
acceleration since an additional forward-directed force acts on the
CG. Conversely, in order to achieve acceleration (or deceleration)
of the vehicle, additional leaning (forward or backward) must be
provided in a manner discussed in further detail below.
[0105] FIG. 1 shows a simplified embodiment of the invention. A
personal transporter is shown and designated generally by numeral
18. A subject 10 stands on a support platform 12 and holds a grip
14 on a handle 16 attached to the platform 12, so that the vehicle
18 of this embodiment may be operated in a manner analogous to a
scooter. A control loop may be provided so that leaning of the
subject results in the application of torque to wheel 20 about axle
22 thereby causing an acceleration of the vehicle. Vehicle 18,
however, is statically unstable, and, absent operation of the
control loop to maintain dynamic stability, subject 10 will no
longer be supported in a standing position and will fall from
platform 12. Different numbers of wheels or other ground-contacting
members may advantageously be used in various embodiments of the
invention as particularly suited to varying applications. Thus, as
described in greater detail below, the number of ground-contacting
members may be any number equal to, or greater than, one. For many
applications, the dimensions of platform 12, and indeed of the
entire ground-contacting module, designated generally by numeral 6,
are advantageously comparable to the dimensions of the footprint or
shoulder width of user 10. Thus transporter 18 may advantageously
be used as a mobile work platform or a recreational vehicle such as
a golf cart, or as a delivery vehicle.
[0106] Transporter 18 may be operated in a station-keeping mode,
wherein balance is maintained substantially at a specified
position. Additionally, transporter 18, which may be referred to
herein, without limitation, as a "vehicle," may also maintain a
fixed position and orientation when the user 10 is not on platform
12. This mode of operation, referred to as a "kickstand" mode,
prevents runaway of the vehicle and provides for the safety of the
user and other persons. A forceplate 8 or other sensor, disposed on
platform 12, detects the presence of a user on the vehicle.
[0107] Another embodiment of a balancing vehicle in accordance with
the present invention is shown in FIG. 2 and designated generally
by numeral 24. Personal vehicle 24 shares the characteristics of
vehicle 18 of FIG. 1, namely a support platform 12 for supporting
subject 10 and grip 14 on handle 16 attached to platform 12, so
that the vehicle 18 of this embodiment may also be operated in a
manner analogous to a scooter. FIG. 2 shows that while vehicle 24
may have clusters 26 each cluster having a plurality of wheels 28,
vehicle 24 remains statically unstable and, absent operation of a
control loop to maintain dynamic stability, subject 10 will no
longer be supported in a standing position and will fall from
platform 12. In the embodiment of FIG. 2, as in the embodiment of
FIG. 1, the primary ground-contacting members are a pair of wheels.
Supplemental ground-contacting members may be used in stair
climbing and descending or in traversing other obstacles. In one
mode of operation, for example, it is possible to rotate clusters
26 so that two wheels on each of the clusters are simultaneously in
contact with the ground. Stair climbing and flat-terrain locomotion
may both be achieved, however, with the vehicle supported on only a
single set of primary ground-contacting members.
[0108] Operation of the balancing transporter will be described
with reference to the set of coordinate axes shown in FIG. 1.
Gravity defines the vertical axis z, while the axis coincident with
the wheel axis 22 may be used to define a lateral axis y, and a
fore-aft axis x is defined by the forward direction of motion of
the vehicle. The plane defined by the vertical axis z and the
lateral axis y will sometimes be referred to as the "lateral
plane", and the plane defined by the fore-aft axis x and the
vertical axis z will sometimes be referred to as the "fore-aft
plane". Directions parallel to the axes x and y are called the
fore-aft and lateral directions respectively. It can be seen that
the vehicle, when relying on the pair of wheels 20 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 other embodiments of the
invention described below, the vehicle may also be unstable with
respect to yaw about the x axis.
[0109] The axes may also be defined with respect to platform 12 in
cases such as where the ground-contacting member is a uniball, as
described below with reference to FIG. 15.
[0110] A simplified control algorithm for achieving 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. 3. 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
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 governed by the following
simplified control equation:
T=K.sub.1(.theta.+.theta..sub.0)+K.sub.2{dot over
(.theta.)}+K.sub.3(x+x.s- ub.0)+K.sub.4{dot over (x)}, (Eqn. 4)
[0111] where:
[0112] T denotes a torque applied to a ground-contacting element
about its axis of rotation;
[0113] .theta. is a quantity corresponding to the lean of the
entire system about the ground contact, with .theta..sub.0
representing the magnitude of a system pitch offset, all as
discussed in detail below;
[0114] x identifies the fore-aft displacement along the surface
relative to a fiducial reference point, with x.sub.0 representing
the magnitude of a specified fiducial reference offset;
[0115] a dot over a character denotes a variable differentiated
with respect to time; and
[0116] a subscripted variable denotes a specified offset that may
be input into the system as described below; and
[0117] K.sub.1, K.sub.2, K.sub.3, and K.sub.4 are gain coefficients
that may be configured, either in design of the system or in
real-time, on the basis of a current operating mode and operating
conditions as well as preferences of a user. The gain coefficients
may be of a positive, negative, or zero magnitude, affecting
thereby the mode of operation of the vehicle, as discussed below.
The gains K.sub.1, K.sub.2, K.sub.3, and K.sub.4 are dependent upon
the physical parameters of the system and other effects such as
gravity. The simplified control algorithm of FIG. 3 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 surface due to
body motion of the subject or contact with other persons or
objects.
[0118] The effect of .theta..sub.0 in the above control equation
(Eqn. 4) is to produce a specified offset -.theta..sub.0 from the
non-pitched position where .theta.=0. Adjustment of .theta..sub.0
will adjust the vehicle's offset from a non-pitched position. As
discussed in further detail below, in various embodiments, pitch
offset may be adjusted by the user, for example, by means of a
thumb wheel 32, shown in FIG. 1. An adjustable pitch offset is
useful under a variety of circumstances. For example, when
operating the vehicle on an incline, it may be desirable for the
operator to stand erect with respect to gravity when the vehicle is
stationary or moving at a uniform rate. On an upward incline, a
forward torque on the wheels is required in order to keep the
wheels in place. This requires that the user push the handle
further forward, requiring that the user assume an awkward
position. Conversely, on a downward incline, the handle must be
drawn back in order to remain stationary. Under these
circumstances, .theta..sub.0 may advantageously be manually offset
to allow control with respect to a stationary pitch comfortable to
the user.
[0119] The size of K.sub.3 will determine the extent to which the
vehicle will seek to return to a given location. With a non-zero
K.sub.3, the effect of x.sub.0 is to produce a specified offset
-x.sub.0 from the fiducial reference by which x is measured. When
K.sub.3 is zero, the vehicle has no bias to return to a given
location. The consequence of this is that if the vehicle is caused
to lean in a forward direction, the vehicle will move in a forward
direction, thereby maintaining balance. Such a configuration is
discussed further below.
[0120] The term "lean" is often used with respect to a system
balanced on a single point of a perfectly rigid member. In that
case, the point (or line) of contact between the member and the
underlying surface has zero theoretical width. In that case,
furthermore, lean may refer to a quantity that expresses the
orientation with respect to the vertical (i.e., an imaginary line
passing through the center of the earth) of a line from the center
of gravity (CG) of the system through the theoretical line of
ground contact of the wheel. While recognizing, as discussed above,
that an actual ground-contacting member is not perfectly rigid, the
term "lean" is used herein in the common sense of a theoretical
limit of a rigid ground-contacting member. The term "system" refers
to all mass caused to move due to motion of the ground-contacting
elements with respect to the surface over which the vehicle is
moving.
[0121] "Stability" as used in this description and in any appended
claims refers to the mechanical condition of an operating position
with respect to which the system will naturally return if the
system is perturbed away from the operating position in any
respect.
[0122] In order to accommodate two wheels instead of the one-wheel
system illustrated for simplicity in FIG. 3, separate motors may be
provided for left and right wheels of the vehicle and 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. 7. Additionally, tracking both the
left wheel motion and the right wheel motion permits adjustments to
be made to prevent unwanted turning of the vehicle and to account
for performance variations between the two drive motors.
[0123] In cases where gain K.sub.3 is zero, a user control input
such as a joystick may be used to adjust the torques of each motor.
The joystick has axes indicated in FIG. 4. In operation of this
embodiment, forward motion of the joystick is used to cause forward
motion of the vehicle, and reverse motion of the joystick causes
backward motion of the vehicle. A left turn similarly is
accomplished by leftward motion of the joystick. For a right turn,
the joystick is moved to the right. The configuration used here
permits the vehicle to turn in place when the joystick is moved to
the left or to the right, by causing rotation of left and right
motors, and hence left and right wheels, at equal rates in opposite
senses of rotation. With respect to forward and reverse motion an
alternative to the joystick is simply leaning forward or backward
(in a case where K.sub.3 is zero), since the pitch sensor
(measuring .theta.) would identify a pitch change that the system
would respond to, leading to forward or reverse motion, depending
on the direction of lean. Alternatively, control strategies based
on fuzzy logic can be implemented.
[0124] It can be seen that the approach of adjusting motor torques
when in the balance 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 vehicle (in this case constituting the entire
vehicle) relative to the ground.
[0125] In the block diagram of FIG. 5 it can be seen that a control
system 51 is used to control the motor drives and actuators of the
embodiment of FIGS. 1-3 to achieve locomotion and balance. These
include motor drives 531 and 532 for left and right wheels
respectively. If clusters are present as in the embodiment of FIG.
2, actuators 541 and 542 for left and right clusters respectively.
The control system has data inputs including user interface 561,
pitch sensor 562 for sensing fore-aft pitch, and wheel rotation
sensors 563, and pitch rate sensor 564. Pitch rate and pitch may be
derived through the use of gyroscopes or inclinometers, for
example, alone or in combination.
[0126] A grip 14 (shown in FIG. 1) may be conveniently provided
with a thumb wheel 32 (shown in FIG. 1) or thumb-operated joystick
for directional control, although other methods of control may also
be used. Thumb wheel 32 may serve multiple control purposes as will
now be described.
[0127] In accordance with other embodiments of the invention,
handle 16 and grip 14 may be absent altogether, and the platform 12
may be equipped with sensors, such as forceplate 8, for example, to
detect leaning of the subject. Indeed, as described in connection
with FIG. 5 and as further described below, the pitch of the
vehicle is sensed and may be used to govern operation of the
control loop, so that if the subject leans forward, the vehicle
will move forward to maintain a desired velocity or to provide
desired acceleration. Accordingly, a forward lean of the subject
will cause the vehicle to pitch forward and produce forward
movement; a backward lean will cause the vehicle to pitch backward
and produce backward movement. Appropriate force transducers may be
provided to sense leftward and rightward leaning and related
controls provided to cause left and right turning as a result of
the sensed leaning.
[0128] Leaning may also be detected using proximity sensors.
Additionally, operation of the vehicle may be governed on the basis
of the orientation of the user with respect to the platform.
[0129] In a further embodiment, the vehicle may be equipped with a
foot- (or force-) actuated switch sensitive to the presence of a
user on the vehicle. Thus, for example, the vehicle may be powered
automatically upon ascent of a user onto the platform. Conversely,
when the user alights from the vehicle, power can be removed and
the vehicle disabled. Alternatively, the vehicle may be programmed
to enter a dynamic "kickstand" mode in which the vehicle remains
balanced in place when the user alights. Thus, the vehicle is ready
for the user to resume travel by reboarding the vehicle.
Furthermore, the vehicle is thus safely parked while not actively
operated by a user aboard the vehicle.
[0130] FIG. 6 is a block diagram providing detail of a driver
interface assembly 273. A peripheral microcomputer board 291
receives an input from joystick 292 as well as from inclinometer
293 or another tilt-determining arrangement. The inclinometer
provides information signals as to pitch and pitch rate. (The term
"inclinometer" as used in this context throughout this description
and in the accompanying claims means any device providing an output
indicative of pitch or pitch rate, regardless of the arrangement
used to achieve the output; if only one of the pitch and pitch rate
variables is provided as an output, the other variable can be
obtained by suitable differentiation or integration with respect to
time.) To permit controlled banking into turns by the vehicle
(thereby to increase stability while turning) it is also feasible
to utilize a second inclinometer to provide information as to roll
and roll rate or, alternatively, the resultant of system weight and
centrifugal force. Other inputs 294 may also be desirably provided
as an input to the peripheral micro controller board 291. Such
other inputs may include signals gated by switches (knobs and
buttons) for platform adjustment and for determining the mode of
operation. The peripheral micro controller board 291 also has
inputs for receiving signals from the battery stack 271 as to
battery voltage, battery current, and battery temperature. The
peripheral micro controller board 291 is in communication over bus
279 with a central micro controller board that may be used to
control the wheel motors as described below in connection with FIG.
7.
[0131] FIG. 7 is a block diagram showing control algorithms,
suitable for use in conjunction with the control assemblies of FIG.
6 to provide stability for a vehicle according to the embodiment of
FIGS. 1-2 and other embodiments in which the vehicle and payload
are balanced on two ground-contacting members, both during
locomotion and in a fixed position. The following conventions are
used in connection with the description below:
[0132] 1. Variables defined in world coordinates are named using a
single subscript in capital letters. World coordinates are
coordinates fixed to the earth (inertial).
[0133] 2. A non-subscripted r identifies a wheel radius.
[0134] 3. Lower case subscripts are used to indicate other
attributes, e.g., right/left, etc.: r=right; 1=left; ref=reference;
f=finish; s=start.
[0135] 4. All angles are positive in the clockwise direction, where
positive travel is in the positive x direction.
[0136] 5. A dot over a variable indicates differentiation in time,
e.g., {dot over (.theta.)}.
[0137] FIG. 7 shows the control arrangement for the motors of the
right and left wheels. The arrangement has inputs of .theta., {dot
over (.theta.)}, r{dot over (.theta.)}.sub.wl (linear velocity of
the left wheel relative to the world coordinate system) and
r.sub.wr (linear velocity of the right wheel), in addition to
directional inputs 3300 determined by joystick position along X and
Y axes of a reference coordinate system. Inputs .theta., , and
error signals x and {dot over (x)} (described below), subject to
gains K.sub.1, K.sub.2, K.sub.3, and K.sub.4 respectively, become
inputs to summer 3319, which produces the basic balancing torque
command for the wheels, in the general manner described above in
connection with FIG. 3 above. The output of summer 3319 is combined
with the output of yaw PID loop 3316 (described below) in summer
3320, then divided in divider 3322 and limited in saturation
limiter 3324, to produce the left wheel torque command. Similarly,
the output of summer 3319 is combined with the output of PID loop
3316 in summer 3321, then divided in divider 3323 and limited in
saturation limiter 3325, to produce the right wheel torque
command.
[0138] In FIG. 7, a directional input along the X axis moves the
reference coordinate system along its X axis relative to the world
coordinate system (which represents the traveled surface), at a
velocity proportional to the displacement of the joystick. A
directional input along the Y axis rotates the reference coordinate
system about its Z axis at an angular velocity proportional to the
displacement of the joystick. It will be appreciated that motion of
the joystick in the positive X direction is here interpreted to
mean forward motion; motion of the joystick in the negative X
direction means reverse motion. Similarly, motion of the joystick
in the positive Y direction means leftward turning,
counter-clockwise as viewed from above; motion of the joystick in
the negative Y direction means rightward turning clockwise as
viewed from above. Hence the directional inputs Y and X are given
deadband via deadband blocks 3301 and 3302 respectively, to widen
the neutral position of the joystick, then subject to gains K11 and
K10, then rate-limited by limiters 3303 and 3304 respectively,
which limit the angular and linear accelerations respectively of
the reference coordinate system. The sum of these outputs achieved
through summer 3305 becomes the reference velocity X.sub.rref
whereas the difference of these outputs achieved through summer
3306 becomes the reference velocity {dot over (x)}.sub.1ref. These
reference velocities are subtracted in summers 3308 and 3307 from
compensated linear velocity input signals r.sub.wl and r.sub.wr for
left and right wheels to obtain velocity error signals {dot over
(x)}.sub.1 and {dot over (x)}.sub.r for left and right wheels
within the reference coordinate system. In turn the average of
these signals, determined via summer 3317 and divider 3318,
produces a linear velocity error signal . Displacement error signal
x is derived by integrating r.sub.wl and r.sub.wr in integrators
3310 and 3309, limiting the results in saturation limiters 3312 and
3311, and then averaging their outputs via summer 3313 and divider
3315. The difference between these displacements, determined via
summer 3314, produces the yaw error signal .psi..
[0139] The yaw error signal .psi. is run through a standard
proportional-plus-integral-plus-derivative (PID) control loop 3316,
the output of which is combined with the output of the basic
balancing torque command of summer 3319, to produce the individual
wheel torque commands, which cause the wheels to maintain fore-aft
stability and also cause the vehicle to align itself with the axes
of, and follow the origin of, the reference coordinate system as
directed by directional input 3300.
[0140] Let us now consider how this control causes the vehicle to
start. The the directional input 3300 (which may be a joystick)
which will provide a positive x for forward motion. The signal is
divided and summed in summers 3308 and 3307, and subtracted from
the right and left wheel velocity {dot over (x)}.sub.R and {dot
over (x)}.sub.L providing a negative correction; this correction
leads ultimately to a negative torque contribution at summer 3319,
causing the wheels to move backward, so as to create a torque due
to gravity that causes the vehicle to lean forward. This forward
lean leads to changing .theta. and {dot over (.theta.)}, which
leads to positive corrections in summer 3319, causing the vehicle
to move forward. Thus, moving the joystick forward or backward will
cause the vehicle to lean forward or backward, as the case may be,
and to move in the direction of the lean. This is a property of the
control of FIG. 7. An equivalent result can be achieved by leaning,
where K.sub.3 is zero.
[0141] Anytime acceleration of the vehicle is desired, it is
necessary to establish system lean. For example, to achieve forward
acceleration of the vehicle, there must be forward system lean; the
center of gravity of the system (vehicle and payload) must be
placed forward of the center of the pressure distribution of the
contact region where the wheels contact the ground. The more the
lean, the more the acceleration. Thus, furthermore, it can be seen
that leaning, in conjunction with gravity and friction, determines
acceleration (positive or negative) of the system. In this manner,
if the vehicle is moving forward, pitching the system back will
achieve braking. Because the vehicle must overcome friction, there
must even be some system lean when the vehicle is moving at
constant velocity over level ground. In other words, looking at the
torque on the vehicle caused by gravity and the torque caused by
all other external forces, the torque applied by the motorized
drive is adjusted so that the net torque from all these sources
produces a desired acceleration.
[0142] In a further embodiment, any of the foregoing embodiments of
a vehicle in accordance with the present invention may be provided
with speed limiting to maintain balance and control, which may
otherwise be lost if the wheels (arcuate elements, or other
ground-contacting members) were permitted to reach the maximum
speed of which they are currently capable of being driven.
[0143] Speed limiting is accomplished by pitching the vehicle back
in the direction opposite from the current direction of travel,
which causes the vehicle to slow down. (As discussed above, the
extent and direction of system lean determine the vehicle's
acceleration.) In this embodiment, the vehicle is pitched back by
adding a pitch modification to the inclinometer pitch value. Speed
limiting occurs whenever the vehicle velocity of the vehicle
exceeds a threshold that is the determined speed limit of the
vehicle. The pitch modification is determined by looking at the
difference between the vehicle velocity and the determined speed
limit, integrated over time.
[0144] Alternatively, the balancing margin between a specified
maximum power output and the current power output of the motors may
be monitored. In response to the balancing margin falling below a
specified limit, an alarm may be generated to warn the user to
reduce the speed of the vehicle. The alarm may be audible, visual,
or, alternatively the alarm may be tactile or may be provided by
modulation of the motor drives, providing a `rumbling` ride that is
readily perceived by the user.
[0145] The automatic pitch modification sequence, in response to a
detected speed at a specified speed limit, is maintained until the
vehicle slows to the desired dropout speed (some speed slightly
below the speed limit), and then the pitch angle is smoothly
returned to its original value.
[0146] One method for determining the speed limit of the vehicle is
to monitor the battery voltage, which is then used to estimate the
maximum velocity the vehicle is currently capable of maintaining.
Another method is to measure the voltages of the battery and the
motor and to monitor the difference between the two; the difference
provides an estimate of the amount of velocity margin (or
`balancing margin`) currently available to the vehicle.
[0147] Leaning of the user may additionally be limited, in
accordance with a further embodiment of the invention, by a
physical constraint such as a vertical member coupled to the
platform, thus preventing leaning, in any specified direction,
beyond the physical constraint.
[0148] The pitch offset, allowing modification of .theta..sub.0, as
discussed above in reference to Equation 4, may be adjusted by the
user by means of thumb-wheel 32 (shown in FIG. 1). Additionally, a
secondary control 34 (shown in FIG. 1) may be provided, in
accordance with embodiments of the invention, for changing the
control architecture or function of the thumb-wheel. Thus,
thumb-wheel 32 can also be put into a mode that operates to drive
both wheels in the same direction. This allows a personal mobility
vehicle such as vehicle 18 to be used as sort of a powered handcart
that the user trails behind her or pushes ahead of her. This is
especially useful when such a personal transporter has to be
carried up stairs because the motors 531 and 534 (shown in FIG. 5)
are used to lift the vehicle to the next riser so that the user
does not have to use as much force as would otherwise be required.
This mode of operation of the vehicle is referred to as "drive
mode." Additionally, upon designation by the secondary selector 34,
thumb wheel 32 may be used by the user for purposes of steering the
vehicle.
[0149] The present invention may also be implemented in a number of
further embodiments. We have found that a vehicle in accordance
with the invention may act suitably as a prosthetic device for
persons who have an impairment, caused by disease (such as
Parkinson's Disease or ear disorders) or defect, in their ability
to maintain balance or to achieve locomotion.
[0150] A control loop, as employed in accordance with an embodiment
of the present invention, may advantageously be used for
ameliorating the symptoms of balance-impairing diseases. A
traditional approach to treatment of Parkinson's Disease is the
administration of drugs such as levodopa to alleviate symptoms of
progressive tremor, bradykinesia and rigidity, however, in most
patients the disease is incompletely controlled. D. Calne, "Drug
Therapy: Treatment of Parkinson's Disease," New England J.
Medicine, vol. 329, pp. 1021-2, (1993). Additionally, prolonged use
of antiparkinsonian drugs leads to progressively adverse reactions
to the drugs. Id.
[0151] A person suffering from Parkinson's disease is neither a
passive nor cooperative load, but rather, since the person suffers
from impaired powers of voluntary movement, the person has
difficulty controlling his or her own balance, whether on a
platform or on the ground. The tremors of such a person cause
additional forces on the platform or vehicle upon which the person
is seated or standing, not necessarily oriented in a
balance-restoring direction.
[0152] The prosthetic device achieved by the vehicle functions as
an extension of the person's own balance system and locomotion
system, since the vehicle has a feedback loop that takes into
account changes in the vehicle's center of gravity attributable to
motion of the person relative to the vehicle. Providing a vehicle
to such a handicapped person is thus a method of fitting a
prosthesis that permits locomotion and balance control when these
would otherwise be unavailable. We have observed a dramatic
restoration of balance and locomotion control to a person suffering
from Parkinson's Disease who utilized a vehicle in accordance with
embodiments of the present invention. Surprisingly, the effect on a
Parkinson's patient who is using the vehicle is to substantially
reduce tremors. Apparently, the inclusion of the Parkinson's
patient in the feedback loop of the combined vehicle-passenger
system creates an environment permitting alleviation of symptoms
experienced by a Parkinson's patient.
[0153] In addition to the embodiments of FIGS. 1-2, many other
configurations of the personal mobility vehicles that are the
subject of the present invention may be provided. The personal
mobility vehicle may alternatively be provided with other
configurations of ground-contacting members, some of which are now
described.
[0154] The width of the ground-contacting members may
advantageously be increased, in accordance with certain alternate
embodiments of the invention, for traversing thin ice or other
terrain where pressure of the vehicle exerted on the ground may
pose a danger.
[0155] Referring to FIG. 8, an alternate embodiment of the
invention is shown in which ground contact is provided by a single
wheel 44. A characteristic common to many of the embodiments of the
present invention is the platform 12 on which subject 10 stands to
operate the vehicle. Handle 16 is provided in certain embodiments
of the invention, as is grip 18 on handle 16 for subject 12 to
grip. In one embodiment of the invention, shown in FIG. 8, handle
16 is rigidly attached to platform 12, in this case, without
limitation, via cowling 40. In an alternate embodiment of the
invention, shown in FIG. 9, handle 16 may be articulated at pivot
46 with respect to a base 48 fixed to platform 12. Articulation of
handle 16 at pivot 46 makes it easy for subject 10 to shift his
weight forward or aft while maintaining one or both hands on grip
14. Platform 12 locomotes with respect to the ground by motion of
at least one wheel 20, or other ground-contacting element. As with
respect to earlier described embodiments, other ground-contacting
elements such as arcuate members and clusters of wheels are
described in the prior applications incorporated herein by
reference, and the term "wheel" is used herein to refer to any such
ground-contacting element without limitation.
[0156] The single wheel 44 of unicycle embodiments of FIGS. 8 and 9
may be supplemented, as shown in FIG. 10, by a nearby wheel
providing a pair of adjacent and coaxial wheels 20. It can be seen
that the vehicle of FIG. 10, like vehicles of various other
embodiments disclosed in this description, when relying on wheels
20 for contacting the ground, is inherently unstable in the
fore-aft direction with respect to a vertical z. While the vehicle
of FIG. 10 is relatively stable in the lateral direction, vehicles
of some other embodiments are unstable in both lateral and fore-aft
directions. The motion of vehicle 18 may be controlled by subject
10 shifting his weight, and thus the center of mass (CG) of the
loaded vehicle, in accordance with teachings described above.
[0157] Also, as described above, in addition to the direct effect,
of subject leaning, on the variables governing the torque applied
to a motor for directing the vehicle, or as an alternate control
strategy, user input may be separately incorporated into the
control loop in a manner equivalent to variation of one or more of
the input variables. Thus, for example, the user may provide an
input, by means of a user interface of any sort, the input being
treated by the control system equivalently to a change, for
example, in vehicle tilt. Such an interface may include, for
example, a thumbwheel or a joystick mounted on the grip 14.
[0158] Referring again to FIG. 10, steering of vehicle 18 may be
provided by user 10 shifting his weight laterally (in the Y-Y
direction) with respect to wheels 20. The change in position of
user 10 relative to the platform 12, and/or the consequential
lateral shift of the CG of the combination of user 10 and vehicle
18 may be sensed using any strategy. One example is the use of one
or more forceplates disposed on the upper surface of platform 14 to
sense differential pressure exerted by a first leg 52 of user 10
with respect to a second leg 54 of the user. Alternatively, a seat
(not shown) may be provided on platform 12 for supporting user 10,
and one or more forceplates mounted on the seat may sense a shift
in the weight of the user and thus generate a signal for
controlling the velocity vector of the vehicle in response to user
leaning. As an alternate example, a tilt of platform 12 relative to
the axis (Y-Y) of rotation of wheel 20 may be sensed using an
inclinometer, or one or more gyroscopes. Corrections may be applied
to the measured tilt of differential pressure to account for
irregularities in the surface being traversed by vehicle 18, as
determined by the measured tilt, with respect to a plane
perpendicular to gravity, of the axis (Y-Y) of rotation of wheel
20. In accordance with yet further alternate embodiments of the
invention, a force sensor may be provided within handle 16 or a
rotation sensor may be provided at pivot 46, either stratagem for
sensing leaning by the user and applying the sensed leaning as a
user input in the control loop for governing vehicle operation.
[0159] In accordance with other embodiments of the present
invention, leaning by user 12 may be used solely for governing
fore-aft motion of vehicle 10, or, alternatively, leaning may be
used solely for governing steering of the vehicle, or, for both
functions.
[0160] A front perspective view of an alternate embodiment of the
invention is shown in FIG. 11 where vehicle 10 has a single wheel
24 and user 12 stands, during normal operation of the vehicle, on
platform 14 astride wheel 24. An embodiment is shown wherein handle
16 is rigidly attached to platform 14, in this case, via cowling
40.
[0161] FIG. 11 shows an embodiment of the invention wherein a
vehicle 50 is controlled by leaning, as described above with
respect to other embodiments, and no handle is provided, such that
the entire support of user 10 is by standing on platform 12. Within
the scope of the present invention, as described herein and as
claimed in any appended claims, user 10 may be supported on
platform 12 by standing with feet positioned along axis 56 of
rotation of wheel 44, as shown in FIG. 11, or, alternatively, with
feet positioned astride axis 52 of rotation of wheel 44, as shown
in FIG. 12 and FIG. 13. A handle 16 may also be provided in the
case of a configuration of the invention in which wheel 44 is
mounted transversely to the direction faced by user 10, with handle
16 coupled to platform 12 via cowling 40, as shown in FIG. 14.
[0162] FIG. 15 shows an embodiment of a vehicle wherein the
ground-contacting element is a uniball 151. Such a ball may be
separately driven in the x and y directions and the vehicle
stabilized in one or both of these directions in the manner
described above.
[0163] In addition to the personal mobility vehicles described and
claimed above, in accordance with alternate embodiments of the
invention, scaled down versions of any of the embodiments
heretofore described may be employed for recreational or
educational purposes, whether or not human subjects are conveyed
thereupon. Such toy versions may travel over various terrains while
maintaining balance in the fore-aft plane.
[0164] The described embodiments of the invention are intended to
be merely exemplary and numerous variations and modifications will
be apparent to those skilled in the art. All such variations and
modifications are intended to be within the scope of the present
invention as defined in the appended claims.
* * * * *