Note: Descriptions are shown in the official language in which they were submitted.
CA 02550748 2001-09-20
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BIPEDAL ROBOT
This is a divisional application of Canadian
Patent Application Serial No. 2,422,721'filed on September
20, 2001.
Technical field
The present invention related to a bipedal robot.
It should be understood that the expression "the invention"
and the like encompasses the subject matter of both the
parent and the divisional applications.
Background art:
Bipedal robots which have in recent years been
proposed for practical use by the present applicant and
others and which have been known in general are basically
human-shaped robots. Like human beings, they have two legs
extending from a hip at the lower end of an upper body
(torso), two arms extending from shoulders on the left and
right opposite sides of the upper body, and a head_maunted
on the upper end of the body and incorporating an imaging
device for robot vision.
Some of the robots of the above type are supplied
with electric power for operating the legs and arms from an
external source through a cable. However, those robots
have a limited range of movement, and the handling of the
cable is complex. Therefore, it is desirable for robots
themselves to carry an electric energy storage device such
as a battery or the like as a power supply for operating
them.
CA 02550748 2001-09-20
Electric energy storage devices such as a bat-
tery or the like which are mounted on robots as the power
supply for operating the robot need to have a relatively
large capacity for allowing the robot to move continuously
for a sufficient period of time, and hence are relatively
large in size and weight. Bipedal robots are essentially
more liable to lose attitude stability when subjected to
disturbance or the like than robots having many legs.
It has therefore been an important task to study
which location and what layout a large and heavy electric
energy storage device is to be mounted in on a bipedal ro-
bot, for achieving attitude stability when the robot walks
and works.
The present invention has been made in view of
the above background. It is an object of the present in-
vention to provide a bipedal robot having an electric ener-
gy storage device mounting structure which makes it pos-
sible to easily achieve attitude stability when the robot
walks and works.
Disclosure of the invention:
In order to achieve the above object, a bipedal
robot according to the present invention is available in
two aspects. According to the first aspect, a bipedal ro-
bot having an electric energy storage device for operating
the robot is characterized in that said electric energy
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storage device is mounted on an upper body of the robot
such that the electric energy storage device has a center-
of-gravity point present at a position upward of the cen-
ter-of-gravity point of the robot from which said electric
energy storage device is removed and which is in an up-
standing state.
It is customary to control the attitude stabili-
zatian of a bipedal robot based on an inverted pendulum-
type dynamic model as disclosed in Japanese laid-open pat-
ent publication No. 5-337849 or U.S. patent No. 5,459,659
by the present applicant. The attitude stabilization is
controlled by controlling a torque around ankles of the ro-
bot with the behavioral characteristics of perturbation of
the position of the upper body of the robot being simulated
by the behavioral characteristics of an inverted pendulum.
A robot under such attitude stabilization control can
achieve better robot attitude stability if the center of
gravity of the overall robot is in a higher position than
it is in a lower position (a vertical position closer to
the floor that is contacted by the feet of the robot).
According to the first aspect of the present in-
vention, as described above, the electric energy storage
device is mounted on the upper body of the robot such that
the electric energy storage device has a center-of-gravity
point present at a position upward of the center-of-gravity
point of the robot from which said electric energy storage
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device is removed and which is in an upstanding state.
Specifically, the upper body is the torso (body) of the ro-
bot from which the legs and arms extend.
With the above arrangement, the center of grav-
ity of the robot including the electric energy storage de-
vice is present in a higher vertical position on the robot,
thus increasing the stability of the attitude when the ro-
bot walks and works.
The first aspect of the present invention is op-
timum for a bipedal robot whose attitude stabilization is
controlled based on an inverted pendulum-type dynamic
model, as described above.
According to the second embodiment, a bipedal
robot having an electric energy storage device for operat-
ing the robot and arms extending from shoulders on an upper
body of the robot is characterized in that said electric
energy storage device is mounted on the upper body of the
robot such that the electric energy storage device has a
center-of-gravity point present at a position rearward, in
a forward and rearward direction of the robot, of the cen-
ter-of-gravity point of the robot from which said electric
energy storage device is removed and which is in an up-
standing state, and the shoulders on the upper body of the
robot, to which said arms are coupled, are disposed in a
position forward, in the forward and rearward direction of
the robot, of the center-of-gravity point of the robot from
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which said electric energy storage device is removed and
which is in the upstanding state.
In the present specification, the forward and
rearward direction of the robot means a direction perpen-
dicular to the direction (lateral direction) in which the
two legs of the robot are parallel to each other and the
vertical direction of the robot when the robot is in the
upstanding state.
According to the second aspect of the present
invention, since the shoulders on the upper body of the ro-
bot, to which the arms of the robot are coupled, are dis-
posed in a position near a frontal surface of the robot,
when the arms are extended forwardly of the robot, they can
grip an object in a relatively far position forward of the
robot. At this time, when the arms of the robot are ex-
tended forwardly, the center of gravity of the robot except
the electric energy storage device is displaced relatively
largely forwardly of the robot. However, the electric en-
ergy storage device which is a heavy object is positioned
rearwardly of the robot (on the rear surface thereof).
Consequently, the center of gravity of the overall robot
assembly including the electric energy storage device is
not displaced largely forwardly of the robot. As a result,
the stability of the attitude of the robot is achieved with
ease even when the robot works with the arms extended for-
wardly. According to the second aspect of the present in-
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vention, therefore, it is possible to achieve the stability
of the attitude of the robot with ease while the robot is
working with the arms at a relatively far position forward
of the robot.
According to the second aspect of the present
invention, as with the first aspect described above, the
electric energy storage device is preferably mounted on the
upper body of the robot such that the electric energy stor-
age device has a center-of-gravity point present at a posi-
tion upward of the center-of-gravity point of the robot
from which said electric energy storage device is removed
and which is in an upstanding state.
With the above arrangement, the stability of the
attitude can be increased when the robot walks and works.
In the second aspect of the present invention,
if said robot has an imaging device present upwardly of the
upper body of the robot and supported on an upper end of
the upper body of the robot, then said imaging device and
the upper body of the robot are preferably coupled to each
other by a joint disposed in a position forward, in the
forward and rearward direction of the robot, of the center-
of-gravity point of the robot from which said electric en-
ergy storage device is removed and which is in the upstand-
ing state.
With the above arrangement, since the imaging
device and the arms are present near the frontal surface of
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the robot, the imaging device and the arms, and the elec-
tric energy storage device on the rear surface of the robot
tend to be balanced in weight, making it possible to
achieve the stability of the attitude of the robot with
greater ease.
According to the first and second aspects of the
present invention, an electric energy storage device mount-
ing unit disposed on an upper body of the robot for mount-
ing said electric energy storage device therein preferably
has an opening defined in an upper end thereof when the ro-
bot is in the upstanding state, said electric energy stor-
age device being insertable into and removable from said
electric energy storage device mounting unit through said
opening.
With the above arrangement, if the robot is re-
latively small, then since the electric energy storage de-
vice can be inserted into and removed from the electric en-
ergy storage device mounting unit through the opening in
the upper end thereof, the electric energy storage device
can easily be removed and mounted for maintenance or the
like. Furthermore, inasmuch as the electric energy storage
device can be removed and mounted while the robot is squat-
ting down, it is possible to remove and mount the electric
energy storage device while keeping the robot in a stable
attitude. As the electric energy storage device mounting
unit has the ogening in its upper end, even when the robot
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works at various attitudes, the electric energy storage de-
vice is free of the danger of being dislodged from the
electric energy storage device mounting unit. Particularly
in the first aspect of the present invention in which the
electric energy storage device is mounted in a location on
an upper portion of the robot, the electric energy storage
device is liable to suffer damage if the electric energy
storage device falls off due to a failure of a lid over the
opening of the electric energy storage device mounting
unit. However, the above arrangement is effective to pre-
vent such a shortcoming from occurring.
The electric energy storage device mounting unit
has an electric reception terminal disposed on a lower end
thereof when the robot is in the upstanding state, for de-
tachable connection to an electric supply terminal of the
electric energy storage device as mounted in said electric
energy storage device mounting. unit.
With the above arrangement, when the electric
energy storage device is inserted into the electric energy
storage device mounting unit, the electric supply terminal
of the electric energy storage device is connected to the
electric reception terminal on the upper body of the robot,
and both the terminals remain reliably connected to each
other under the weight of the electric energy storage de-
vice.
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Brief description of the drawings:
FIG. 1 is a side elevational view of a bipedal
robot, in an upstanding state, according to an embodiment
of the present invention; and FIG. 2 is a side elevational
view of the bipedal robot shown in FIG. I which is in an
attitude for removing and mounting an electric energy stor-
age device.
Best mode for carrying out the invention:
An embodiment of the present invention will be
described below with reference to FIGS. 1 and 2.
As shown in FIG. 1, a bipedal robot according to
the present embodiment is a human-shaped robot having an
upper body 1 (torso), legs 2, arms 3, and a head 4. Since
FIG. 1 is a side elevational view of the robot in an up-
standing state, only one leg 2 and only one arm 3 are shown
in FIG. 1. However, the robot actually has a pair of left
and right legs 2 and a pair of-left and right arms 3 like a
human being. The leg 2 and the arm 3 which are illustrated
are a right leg and a right arm, respectively, as viewed in
the forward direction of the robot.
The upper body 1 of the robot has a main body 5
to which the legs 2 and the arms 3 are coupled and which
supports the head 4, a first auxiliary body 7 serving as an
electric energy storage device mounting unit for mounting
an electric energy storage device 6 as a power supply for
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operating the robot, and a second auxiliary body 9 for
mounting a control unit 8 (an electric circuit unit having
a microcomputer, etc, hereinafter referred to as ECU 8) for
controlling the operation of the robot.
According to the present embodiment, the elec-
tric energy storage device 6 comprises a rechargeable sec-
ondary battery such as a lithium ion battery or the like.
However, the electric energy storage device 6 may comprise
a large-capacity capacitance such as an electric double-
layer capacitor.
Shoulders 10 are provided on respective left and
right sides of an upper portion of the main body 5. The
arms 3 extend from shoulder joint mechanisms (not shown)
placed in the shoulders 10. Each of the arms 3 has an el-
bow joint 12 and a wrist joint 13 disposed between a hand
11 and the shoulder 10 and arranged successively from the
shoulder 10.
The main body 5 has a hip 14 at its lower end.
The legs 2 extend downwardly from a pair of left and right
hip joints 15, respectively, coupled to a parallel link
mechanism (not shown) placed in the hip 14. Each of the
legs 2 has a knee joint 17 and an ankle joint 18 disposed
between a foot 16 and the hip joint 15 and arranged succes-
sively from the hip joint 15.
The first auxiliary body 7 is shaped as a casing
mounted on a rear surface of the upper portion of the main
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body 5. The first auxiliary body 7 has a support member 19
disposed therein and fixed to the rear surface of the upper
portion of the main body 5 for mounting the electric energy
storage device 6 thereon. The electric energy storage de-
vice 6 is placed and supported on the support member 19.
As shown in FIG. 2, the first auxiliary body 7
has an opening 21 defined in an upper end thereof and ope-
nable and closable by an opening/closing lid 20. When the
opening/closing lid 20 is opened as indicated by the imagi-
nary lines in FIG. 2, the electric energy storage device 6
can be inserted into and removed from the first auxiliary
body 7 through the opening 21. An electric reception ter-
minal 23 in the form of a connector is disposed on the low-
er end (which is positioned immediately below the electric
energy storage device 6 when the robot is in the upstanding
state) of the support member 19 which supports the electric
energy storage device 6. The electric reception terminal
23 fits with an electric supply terminal 22 (which outputs
the electric energy from the electric energy storage device
6) in the form of a connector disposed on a lower surface
of the electric energy storage device 6. The electric re-
ception terminal 23 distributes and supplies the electric
energy from the electric energy storage device 6 to elec-
tric motors (not shown) associated with the joints of the
robot and the ECU 8, etc. When the electric energy storage
device 6 is inserted into the first auxiliary body 7
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through the opening 21 and supported on the support member
19, the electric reception terminal 23 fits with the elec-
tric supply terminal 22 of the electric energy storage de-
vice 6 and is electrically connected thereto.
when the opening/closing lid 20 closes the open-
ing 21 (as indicated by the solid lines in FIG. 2), the
opening/closing lid 20 is locked in the closed position by
a lock mechanism (not shown). An electric motor 24 is
mounted in the first auxiliary body 7 for unlocking the
opening/closing lid 20 from the locked state.
As shown in FIG. 1, the second auxiliary body 9
is disposed directly below the first auxiliary body 7 and
is,shaped as a casing mounted on a lower portion of the
main body 5. The second auxiliary body 9 houses therein a
support member 25 fixed to a rear surface of the lower por-
tion of the main body 5 and supporting the ECU 8 thereon.
The head 4 has an imaging device (camera) 26 for
robot vision housed in an outer shell 4a (casing), the
imaging device 26 having its visual field directed for-
wardly: The imaging device 26 is coupled by a joint 29 to
a speed reducer 28 which is mounted on an attachment 27
erected from a front portion of the upper end of the main
body 5. The imaging device 26 is swingable about the axis
of rotation of the speed reducer 28 in unison with rotation
of the speed reducer 28. The speed reducer 28 is mounted
on the attachment 27 such that the axis of rotation thereof
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is directed laterally (the direction normal to the sheet of
FIG. 1). As indicated by the arrow Y in FIG. 1, the imag-
ing device 26 is swingable to vertically move its visual
field. The rotational drive force of the electric motor 30
is transmitted through a belt or the like to the imaging
device 28, thus swinging the imaging device 26 as described
above.
Although not shown, the bipedal robot according
to the present embodiment also has, in addition to the
above structural details, electric motors for actuating the
joints of the legs 2 and the arms 3, sensors for detecting
angular displacements of the electric motors (angular dis-
placements of the joints), sensors for detecting loads and
moments acting on the feet 16 of the legs 2 and the hands
11 of the arms 3, and sensors for detecting an angle of in-
clination and an angular velocity of inclination of the up-
per body 1.
The ECU 8 controls the electric motors based on
information obtained from the sensors (including the imag-
ing device 26) and a predetermined program thereby to con-
trol operation of the robot (i.e., to control the walking
of the robot through operation of the legs 2, and to con-
trol the working of the robot through operation of the arms
3). In the present embodiment, the ECU 8 controls opera-
tion of the joints of the legs 2 based on an inverted pen-
dulum-type dynamic model as disclosed in Japanese laid-open
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patent publication No. 5-337849 or U.S. patent No.
5,459,659, for thereby controlling attitude stabilization
when the robot walks and works.
With the bipedal robot of the above structure
according to the present embodiment, when the electric en-
ergy storage device 6 is removed (detached) and the robot
is in the upstanding state as shown in FIG. 1, the robot
has its center of gravity present at a point A shown in
FIG. 1 (substantially at the center of the main body 5)
(the point A will hereinafter be referred to as reference
center-of-gravity point A), for example. The upstanding
state referred to above is a state in which the left and
right legs 2 are parallel to each other in the lateral di-
rection, the legs 2 and the upper body 1 are extended ver-
tically and erected, and the left and right arms 3 are ex-
tended vertically downwardly.
When the electric energy storage device 6 is
mounted on the robot and supported on the support member 19
in the first auxiliary body 7, the electric energy storage
device 6 has its own center of gravity (positioned substan-
tially at the center of the electric energy storage device
6) present at a point B shown in FIG. 1 (the point B will
hereinafter be referred to as electric energy storage de-
vice center-of-gravity point Bj. The electric energy stor-
age device center-of-gravity point B is present upwardly of
the reference center-of-gravity point A (see the arrow P in
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FIG. 1), and rearwardly of the reference center-of-gravity
paint A (see the arrow Q in FIG. 1). Stated otherwise,
with the robot according to the present embodiment, the
first auxiliary body 7 and the support member 19 are dis-
posed such that the electric energy storage device center-
of-gravity point B is in the above positional relationship
to the reference center-of-gravity point A.
According to the present embodiment, further-
more, the shoulders 10 are mounted on the main body 5 such
that their center C is present forwardly of the reference
center-of-gravity point A (see the arrow R in FIG. 1). The
imaging device 26 is supported on the attachment 27 erected
from the upper end of the main body 5 forwardly of the ref-
erence center-of-gravity point A, and disposed in a posi-
tion near a foremost surface of the robot forwardly of the
reference center-of-gravity point A (see the arrow S in
FIG. 1).
With the bipedal robot according to the present
embodiment, since the electric energy storage device cen-
ter-of-gravity point B of the electric energy storage de-
vice 6 which is a heavy object is present upwardly of the
reference center-of-gravity point A as described above, the
overall robot assembly with the electric energy storage de-
vice 6 mounted thereon has its center of gravity present in
a high position close to the upper end of the overall robot
assembly (a position higher.than the reference center-of-
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gravity point A). Therefore; the behavioral characteris-
tics of the robot attitude are well in conformity with the
behavioral characteristics of an inverted pendulum. As a
result, by controlling attitude stabilization of the robot
based on an inverted pendulum-type dynamic model, the atti-
tude stabilization of the robot can be controlled appropri-
ately for achieving good attitude stability of the robot.
Furthermore, the center C of the shoulders 10 is
positioned forwardly of the reference center-of-gravity
point A, so that that the shoulders 10 are positioned near
the frontal surface of the robot. When the arms 3 are ex-
tended forwardly, the hands of the arms 3 reach a rela-
tively far position forward of the robot, and can grip an
object in such a far position.
Since the imaging device 26 is positioned near
the foremost surface of the robot, the visual field of the
imaging device 26 can cover a vertically wide range simply
vertically swinging the imaging device 26 only without the
need for a mechanism for vertically swinging the head 4 of
the robot. In particular, the imaging device 26 can image
its feet and a surrounding area when the robot walks up and
down a stair or the like.
Because the shoulders 10 and the imaging device
26 are positioned forwardly of the reference center-of-
gravity point A near the frontal surface of the robot, when
both the arms 3 are extended forwardly, the center of grav-
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ity of the robot except the electric energy storage device
6 is displaced relatively largely forwardly of the robot.
However, the electric energy storage device 6 is positioned
rearwardly of the reference center-of-gravity point A and
mounted on the rear surface of the robot, opposite to the
shoulders 10 and the imaging device 26. Consequently, even
when both the arms 3 are extended forwardly, the center of
gravity of the overall robot assembly including the elec-
tric energy storage device 6 is not particularly displaced
forwardly of the robot. Thus, the center of gravity of the
overall robot assembly including the electric energy stor-
age device 6 has its position changing relatively small
forwardly and rearwardly between the state in which both
the arms 3 are hanging downwardly and the state in which
they are extended forwardly. As a result, the stability of
the attitude of the robot when the robot works with the
arms 3 is achieved with ease.
With the robot according to the present embodi-
ment, for maintenance of the electric energy storage device
6 (e. g., for charging or replacing the electric energy
storage device 6), the electric energy storage device 6 is
removed and mounted as follows:
When the ECU 8 is given a command for mainte-
nance of the electric energy storage device 6 from an ex-
ternal source, the ECU 8 controls the robot to take an at-
titude state as shown in FIG. 2. In this attitude state,
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the feet 16 and the knee joints 17 of the legs 2 are held
in contact with the floor, and the hands 11 of the arms 3
are also held in contact with the floor. (This attitude
state is similar to the attitude of a human being in which
the knees and hands are put down on the floor for a bow.)
The robot is controlled to take this attitude state for the
purpose of reliably achieving the stability of the attitude
of the robot.
When the ECU 8 confirms that the robot has taken
the attitude state as shown in FIG. 2 based on output sig-
nals from the sensors (not shown) which detects angular
displacements of the electric motors (not shown) for ac-
tuating the joints of the legs 2 and the arms 3, the ECU 8
energizes the electric motor 24 on the first auxiliary body
7 to unlock the opening/closing lid 20 from the closed po-
sition.
At this time, the ECU 8 also switches from the
power supply for itself and the electric motors to a backup
electric energy storage device (not shown) which is mounted
on the robot as a power supply for temporary operation.
Since the backup electric energy storage device is used to
carry out temporary operation of the robot, it may be of a
relatively small capacity and is smaller in size and weight
than the electric energy storage device 6.
Then, the operator or the like opens the open-
ing/closing lid 20, and removes or mounts the electric en-
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ergy storage device 6 through the opening 21 in the first
auxiliary body 7 (i.e., inserts the electric energy storage
device 6 into or removes the electric energy storage device
6 from the first auxiliary body 7).
According to the present embodiment, therefore,
after controlling the robot to take the attitude state for
reliably achieving the stability of the attitude of the ro-
bot, the electric energy storage device 6 can easily be re-
moved and mounted through the upper portion of the first
auxiliary body 7.
When the electric energy storage device 6 is in-
serted into the first auxiliary body 7, the electric supply
terminal 22 of the electric energy storage device 6 fits
with the electric reception terminal 23 of the support mem-
ber 19 under the weight of the electric energy storage de-
vice 6. Therefore, the terminals 22, 23 can reliably be
electrically connected to each other.
Industrial applicability:
The bipedal robot according to the present in-
vention is useful as a robot which carries an electric en-
ergy storage device for operating the robot and~which moves
on two legs and performs various works with two arms, like
a human being.
