Horizontal actuator mechanism for the legs of a walking machine

A leg mechanism and horizontal actuator therefor comprising a frame member, first, second, third and fourth elongate links arranged in a pantograph mechanism, with one corner of the pantograph providing the main mounting point for the leg mechanism, a pair of crank arms connected to two of the links and extending approximately perpendicular to the ends thereof adjacent the main mounting point, and a drive member connected between the first and second crank arms for controlling the angle therebetween.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a horizontal actuator mechanism for the 
legs of a walking machine and, more particularly, to a horizontal actuator 
mechanism for a pantograph leg mechanism for a walking machine which 
insures uniform and accurate horizontal movement of the leg mechanism 
regardless of its position. 
2. Description of the Prior Art 
It has long been known that it would be advantageous to develop a machine 
that walks rather than one driven by wheels or treads because a machine 
with legs can operate in areas and on terrain where wheeled or treaded 
vehicles cannot go. Knowing this, numerous attempts have been made over 
the years to develop a walking machine. However, the problems in 
developing such a machine have been so formidable that to this time, no 
satisfactory machine exists. These problems include coordinating the 
movement of the various legs, teaching the machine how to sense its 
environment so that each foot lands properly, and teaching the machine 
balance so that it does not fall over. The simple fact of the matter is 
that while walking is second nature to people and animals, it is extremely 
complex for computers and robots. 
The computer, with its ability to process enormous amounts of data and 
actuate suitable commands, promises to make the control of the legs of a 
walking machine a manageable problem. As a result, a number of researchers 
around the world have been working on the development of various different 
types of walking machines. 
In copending application Ser. No. 476,629, filed concurrently herewith, 
entitled Walking Machine, and assigned to Odetics, Inc., the assignee of 
the present application, there is disclosed a walking machine including a 
body having six legs attached thereto, extending therearound, in uniform 
positions around the body. As discussed in such application, by arranging 
a walking machine with a body and six uniformly spaced legs, the machine 
has the ability to maneuver in areas that are as small as a human being 
can maneuver in. 
In copending application Ser. No. 476,583, filed concurrently herewith, 
entitled Vertical Actuator Mechanism for the Legs of a Walking Machine, 
and assigned to Odetics, Inc., the assignee of the present application, 
there is disclosed the basic details of a leg mechanism for a walking 
machine incorporating the concept of a pantograph which achieves isolation 
between the mechanisms which drive the machine foot horizontally and 
vertically. That application also teaches the broad concept of an actuator 
mechanism for driving the foot vertically. This vertical actuator 
mechanism maintains the vertical position of the foot as the foot is 
driven horizontally. That application does not, however, teach an actuator 
mechanism for driving the foot horizontally. 
In copending application Ser. No. 476,558, filed concurrently herewith, 
entitled Leg Mechanism for Walking Machine, and assigned to Odetics, Inc., 
the assignee of the present application, there is disclosed a foldable leg 
mechanism which will allow the legs of a walking machine to fold compactly 
against the machine body. That application discloses but does not claim a 
horizontal actuator mechanism for the leg mechanism which is the subject 
of the present invention. 
In copending application Ser. No. 476,583, long, swinging struts are used 
to drive the foot vertically while accommodating the horizontal motion of 
the vertical drive point. It is impractical to use the vertical drive 
point to achieve horizontal extension of the foot because such point moves 
up and down very large distances with the vertical motion. The overall 
system that the present invention is a part of accommodates the long 
struts of the vertical drive system rather efficiently. However, there is 
no room for long struts to accomplish a similar goal for the horizontal 
actuator mechanism. A simple and efficient system which does not rely on 
sliding actuators has been unknown heretofore. 
SUMMARY OF THE INVENTION 
According to the present invention, there is provided a horizontal actuator 
mechanism for the legs of a walking machine, including a plurality of 
links arranged in a pantograph mechanism, with one corner of the 
pantograph providing the main mounting point for each leg. Vertical 
actuation of the pantograph mechanism is accomplished by means of a pair 
of long, swinging struts connected between a drive nut and a point on the 
pantograph mechanism. The horizontal actuator mechanism is connected 
directly to two of the pantograph links, at the main mounting point of the 
pantograph mechanism, so as to eliminate the need for sliding mechanisms 
or long, swinging links. 
With such an arrangement, the problem arises that the leverage that each 
link has to effect motion of the foot of the leg mechanism horizontally 
varies from maximum leverage to zero leverage depending upon how far in or 
out the foot is and how far up and down the foot is. According to the 
present invention this problem is solved in that horizontal actuation is 
achieved by providing a pair of crank arms, one on each of the links 
connected to the main mounting point. One crank arm effects the angular 
position of one link and the other crank arm effects the angular position 
of the other link. A prime mover, such as a motor, simply provides a force 
between these two crank arms such that the leverage from the actuator to 
the crank arms is proportioned properly for whatever mechanical advantage 
the links individually have for moving the foot horizontally, for whatever 
position the leg is in. 
Briefly, a leg mechanism and horizontal actuator therefor constructed in 
accordance with the teachings of the present invention comprises a frame 
member, a first elongate link, a first end of the first link being 
pivotally connected to the frame member, a second link, a first end of the 
second link being pivotally connected to a second end of the first link, 
the second end of the second link forming a foot, a third link, a first 
end of the third link being pivotally connected to the frame member and 
the first end of the first link, a fourth link, a first end of the fourth 
link being pivotally connected to the second end of the third link, the 
second end of the fourth link being pivotally connected to an intermediate 
point on the second link, a vertical actuator mechanism operatively 
connected to the fourth link, and a horizontal actuator mechanism 
including a first crank arm connected to the first link and extending 
approximately perpendicular to the first end thereof, a second crank arm 
connected to the third link and extending approximately perpendicular to 
the first end thereof, and drive means connected between the first and 
second crank arms for controlling the angle therebetween. 
According to the preferred embodiment of the present invention, the drive 
means comprises a motor, a jack screw driven by the motor, and a drive nut 
on the jack screw, and the horizontal actuator mechanism further comprises 
a fifth link connected between the first crank arm and the motor, a sixth 
link connected between the second crank arm and the drive nut, and a 
rocker arm connected between the motor and the frame member for limiting 
horizontal movement of the motor. 
OBJECTS, FEATURES AND ADVANTAGES 
It is, therefore, the object of the present invention to solve the problems 
associated with providing a horizontal actuator mechanism for the legs of 
a walking machine. It is a feature of the present invention to solve these 
problems by providing a horizontal actuator mechanism which applies its 
drive force between a pair of crank arms connected to leg links connected 
to the main mounting point of the leg mechanism. An advantage to be 
derived is a horizontal actuator mechanism in which the leverage from the 
actuator is proportioned properly for whatever mechanical advantage the 
links individually have for moving the foot horizontally, for whatever 
position the leg is in. Another advantage is a horizontal actuator 
mechanism for the legs of a walking machine including a lead screw wherein 
rotation of the lead screw is linearly proportional to the horizontal 
movement of the foot of the legs.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to the drawings and, more particularly, to FIGS. 1, 2, 3, 4 
and 7 thereof, there is shown a leg mechanism, generally designated 10, 
for a walking machine. Reference should be had to the beforementioned 
copending application Ser. No. 476,558 for a complete description of leg 
mechanism 10 and the manner in which it will allow the legs of a walking 
machine to fold compactly against a machine body. Reference should also be 
had to the beforementioned copending application Ser. No. 476,629 for a 
more complete description of the manner in which leg mechanism 10 may be 
combined with a plurality of additional and identical leg mechanisms and 
attached to a body for forming a complete walking machine. 
The construction of a complete walking machine is not directly relevant to 
the present invention, nor is the exact details of leg mechanism 10, the 
present invention being only directed to the actuator mechanism for 
controlling the horizontal position of the foot of a pantograph leg 
mechanism. However, the present invention will be described in its 
preferred embodiment, which is for use with the leg mechanism of 
application Ser. No. 476,558. Accordingly, a complete description of leg 
mechanism 10 will be provided. 
Leg mechanism 10 includes an elongate, upright leg frame 11 which is 
adapted to be connected to a walking machine body (not shown) in a manner 
(not shown) which will permit pivotal movement of leg frame 11. Leg frame 
11 has a pair of opposed, spaced, parallel sides 14 and 15. A pin 16 
extends between sides 14 and 15, at the lower end of leg frame 11. 
Leg mechanism 10 includes a plurality of elongate links arranged in a 
parallelogram to form a pantograph mechanism whereby forces applied at 
selected points on individual ones of the links can be transmitted to 
another link which forms the movable foot of the mechanism. More 
specifically, leg mechanism 10 includes a first elongate link 17 which may 
be viewed as forming the thigh of leg mechanism 10. Link 17 is a solid 
member having a dog leg, as shown at 18. Pin 16 extends through a first 
end of thigh 17 so as to pivotally connect thigh 17 to leg frame 11. 
Leg mechanism 10 includes a second elongate link, generally designated 20, 
which forms the shin of leg mechanism 10. Link 20 is preferably made in 
two parts, an upper part 21 and a lower part 22, which are connected 
together in any suitable manner. Part 21 is a generally U-shaped member in 
that the upper portion thereof includes a pair of opposed, parallel sides 
23 and 24, and the lower portion is a solid member, as shown at 25. First 
ends of sides 23 and 24 and the second end of link 17 are pivotally 
connected to each other by means of a pin 26. Sides 23 and 24 are 
positioned on opposite sides of the second end of link 17, as shown most 
clearly in FIGS. 2 and 7. This permits positioning of link 17 between 
sides 23 and 24 of link 20. It should also be noted that the lower end of 
part 22 of link 20 forms the foot 27 of leg mechanism 10, which foot 27 
may conveniently be provided with a rubber cap 27'. 
Leg mechanism 10 includes a pair of third elongate links 28 and 29, first 
ends of links 28 and 29 being pivotally connected to frame member 11, 
preferably by means of pin 16. According to the preferred embodiment of 
the invention, link 17 is positioned between links 28 and 29. Links 28 and 
29 have a slight dog leg, as shown at 30 in FIG. 1. 
The fourth side of the parallelogram is formed by a pair of elongate links 
31 and 32, first ends of links 31 and 32 being pivotally connected to 
second ends of links 28 and 29, by means of a pin 33, with both of links 
28 and 29 positioned between links 31 and 32. Second ends of links 31 and 
32 are pivotally connected to an intermediate point on link 20, 
specifically part 21 of link 20, with part 21 of link 20 between links 31 
and 32. So as to permit link 17 to pass between sides 23 and 24 of link 
20, link 31 is connected to side 23 by a pin 34 and link 32 is connected 
to side 24 by a separate pin 35. 
It will be readily appreciated by those skilled in the art, from an 
inspection of FIG. 1, that the arrangement of the links just described 
forms a pantograph mechanism with the various links formed into a 
parallelogram, the corners of which are defined by the letters A, B, C and 
D. The parallel sides of the parallelogram are shown by dotted lines. 
Point B, defined by pin 16, is the fixed point on the pantograph whereas 
foot 27 is the ultimate movable member thereof. 
Vertical movement of foot 27 is controlled by a pair of actuator struts 36 
and 3, first ends of struts 36 and 37 being pivotally connected to an 
intermediate point E on links 31 and 32, with links 31 and 32 positioned 
between struts 36 and 37. A single pin 38 extends between struts 36 and 
37, through links 31 and 32. The second ends of struts 36 and 37 are 
connected to a leg actuator mechanism, generally designated 39, which is 
connected to leg frame 11. 
More specifically, leg actuator mechanism 39 includes a motor 40 connected 
by means of suitable gearing 41 to a lead screw 42 which is mounted for 
rotation in leg frame 11 by a pair of bearings 43 and 44. A drive nut 45 
is mounted on lead screw 42 so that drive nut 45 is driven vertically, 
either up or down, by rotation of lead screw 42. The second ends of struts 
36 and 37 are pivotally connected to drive nut 45 by means of pins 45A and 
45B, respectively. For a more complete description of the manner in which 
leg actuator mechanism 39 controls the vertical movement of foot 27, 
reference should be had to copending application Ser. No. 476,583. 
According to the present invention, leg mechanism 10 includes a leg 
actuator mechanism, generally designated 50, for driving foot 27 
horizontally. Leg actuator mechanism 50 includes a motor 51 which directly 
drives a lead screw 52. Motor 51 is pivotally mounted on one end of a 
U-shaped rocker arm 53 by means of a pair of pins 53A and 53B. The other 
end of rocker arm 53 is connected by means of a pin 54 between sides 14 
and 15 of leg frame 11. Riding on lead screw 52 is a drive nut 55. 
Link 17 incorporates a crank arm 56 made as an integral part therof, 
extending approximately perpendicular to the first end thereof, adjacent 
pin 16. Similarly, links 28 and 29 incorporate crank arms 58 and 59, 
respectively, made as integral parts thereof, extending approximately 
perpendicular to the first ends thereof, adjacent pin 16. A link 60 has a 
first end thereof made integral with drive nut 55 and a second end thereof 
connected to crank arms 58 and 59 by means of a pin 61. A link 62 has a 
first end thereof connected to one side of rocker arm 53 by means of a pin 
63 and a second end thereof connected to crank arm 56 by means of a pin 
64. 
As can be seen from a comparison of FIGS. 1, 5 and 6, which show multiple 
different positions of leg mechanism 10, it is impractical to connect leg 
actuator mechanism 50 to vertical drive point E because point E moves up 
and down by very large distances with the vertical motion of foot 27. 
While leg mechanism 10 has room for long struts 36 and 37 for leg drive 
means 39, there is no room for corresponding struts to accomplish a 
similar goal for the horizontal movement of foot 27. Therefore, in order 
to avoid sliding actuators to accommodate the vertical motion of point E, 
horizontal motion of foot 27 is provided by directly actuating links 17 
and 28/29 at the main mounting point B of pantograph leg mechanism 10. 
The problem that arises by having leg drive means 50 actuate links 17 and 
28/29 directly at mounting point B is that the leverage that link 17 has 
to effect motion of foot 27 horizontally and the leverage that links 28/29 
have to effect motion of foot 27 horizontally varies from maximum leverage 
to zero leverage depending upon how far in or out foot 27 is and how far 
up and down foot 27 is. According to the present invention, this problem 
is solved by splitting the actuation force between links 17 and 28/29. 
When motor 51 rotates jack screw 52, it simply forces a change in distance 
between motor 51 and drive nut 55 thereby, through links 60 and 62, 
changing the angle between crank arms 56 and 58/59. The angles of crank 
arms 56 and 58/59 are proportioned properly for whatever mechanical 
advantage links 17 and 28/29 have for moving foot 27 horizontally, for 
whatever the position of leg mechanism 10 is. 
The potential problem which is solved by the present invention can be seen 
from a comparison of FIGS. 1, 5 and 6. It is seen that when links 17 and 
28/29 are both approximately vertical, both crank arms 56 and 58/59 are in 
position to have force applied thereto by drive motor 51. On the other 
hand, when link 17 approaches the horizontal position, as shown in FIG. 1, 
a point is reached where pin 64 is in line with pins 16 and 63 so that a 
force applied thereto is ineffective in moving leg mechanism 10. 
Similarly, as links 28 and 29 approach the horizontal position as shown, 
for example, in FIG. 5, a position is reached where pin 61 is aligned with 
drive nut 55 and pin 16 so that a force applied to crank arms 58 and 59 is 
ineffective in moving foot 27. For the entire operating range of foot 27, 
it will always be the case that one or the other of crank arms 56 and 
58/59 will be effective in moving foot 27 when the other is not. At some 
locations, both crank arms will have nearly equal effectiveness. In any 
event, leg actuator mechanism 50 is arranged so as to automatically divide 
the motion of motor 51 in proportion to the link angles to accommodate 
whichever one has effective motion available. 
It should be noted that the upper end of jack screw 52 (motor 51) is 
connected by means of rocker arm 53 and link 62 to crank arm 56 so that 
motor 51 can push or pull against crank arm 56 mounted on link 17. The 
upper end of link 62 could just as easily be connected directly to motor 
51, but is connected to rocker arm 53 as a matter of convenience. 
It should also be noted that motor 51 is floating relative to leg frame 11, 
in the sense that it is not rigidly connected thereto. Rocker arm 53 
permits motor 51 to change its position as leg actuator mechanism 39 moves 
foot 27 vertically, independently of horizontal movement of foot 27. 
Rocker arm 53 is necessary to restrain horizontal movement of motor 51 so 
that all of the motion of drive nut 55 will be confined to tension and 
extension of links 17 and 28/29. 
In other words, lead screw 52 and drive nut 55 are intended to apply 
vertical forces to cranks 56 and 58/59, which cranks are at angles of 
approximately 90.degree. to links 17 and 28/29, which is what converts 
that vertical motion to horizontal motion of foot 27. In order to jack 
screws 52 to effectively apply such forces, it must be confined to move 
only in the vertical direction. The attachment point to crank arms 58 and 
59 effects the confinement at the lower end of jack screw 52. Rocker arm 
53 effects the confinement at the upper end of jack screw 52. 
Another advantage results from the arrangement of leg actuator mechanism 50 
just described. More specifically, the various components can be arranged 
and proportioned so that a given rotation of lead screw 52 will effect a 
proportional horizontal movement of foot 27, regardless of the extension 
position of foot 27 and regardless of the vertical position of foot 27. 
That is, by making the angular rotation of lead screw 52 linearly 
proportional to the horizontal movement of foot 27, a potentiometer can be 
mounted to sense the rotation of lead screw 52, the output of such 
potentiometer not only indicating the angular rotation of jack screw 52 
but also indicating the horizontal position of foot 27. Such potentiometer 
output signal can be fed back to a computer controlling leg mechanism 10 
so that the computer will always know what the horizontal position of foot 
27 is, regardless of its vertical position. 
While the invention has been described with respect to the preferred 
physical embodiment constructed in accordance therewith, it will be 
apparent to those skilled in the art that various modifications and 
improvements may be made without departing from the scope and spirit of 
the invention. Accordingly, it is to be understood that the invention is 
not to be limited by the specific illustrative embodiment, but only by the 
scope of the appended claims.