In this Report, we describe the design and control of RHex, a power autonomous, untethered,
compliant-legged hexapod robot. RHex has only six actuators one motor located at each hip
achieving mechanical simplicity that promotes
Reliable and robust operation in real-world tasks.
Empirically stable and highly maneuverable locomotion arises from a very simple clock-driven,
open-loop tripod gait. The legs rotate full circle, thereby preventing the common problem of toe
stubbing in the protraction (swing) phase. An extensive suite of experimental results documents
the robot’s significant ‘intrinsic mobility’ the traversal of rugged, broken and obstacle ridden
ground without any terrain sensing or actively controlled adaptation.
RHex achieves fast and robust forward locomotion traveling at speeds up to one body length per
second and traversing height variations well exceeding its body clearance.
8
LIST OF TABLES
Table no. Table Description Page no.
1 Summary of Published 12
Performance Reports: Hexapedal Robots
9
LIST OF FIGURES
Figure no. Figure Description Page no.
1 Rigid body structure 25
2 Rigid body structure 26
3 Rigid body structure 27
4 Rigid body structure 28
5 Legs 29
6 Legs 30
7 Circuit Diagram 31
8 Circuit 32
9 Remote Control 33
10 Pin Diagram 34
11 Block Diagram 35
10
TABLE OF CONTENTS
Page no.
Acknowledgement I
Abstract II
List of Tables III
List of Figures IV Table of Content V
Chapter : 1 Introduction 11
Chapter : 2 Brief History of the work 16
Chapter : 3 R-HEX ROBOT
3.1 Detailed Description Of The Invention
3.1.1 Legs 19
3.1.2 Operation 22
3.2 Body Structure 25
3.3 Circuit Diagram 31
3,4 Receiver Parts 38
3.5 Transmitter Parts 39
Conclusion 40
References 41
11
CHAPTER 1
INTRODUCTION
In our project ,we report on a power autonomous legged vehicle, RHex easily traverses terrain
approaching the complexity and diversity of the natural landscape.
A robot is a mechanical or virtual agent, usually an electro-mechanical machine that is guided
by a computer program or electronic circuitry.
A robot can be defined as a programmable, self-controlled device consisting of electronic,
electrical, or mechanical units. More generally, it is a machine that functions in place of a living
agent. Robots are especially desirable for certain work functions because, unlike humans, they
never get tired.
The concept of robots is a very old one yet the actual word robot was invented in the 20th
century from the Czechoslovakian word robota or robotnik meaning slave, servant, or forced
labor. Robots don’t have to look or act like humans but they do need to be flexible so they can
perform different tasks.
Characteristics that make robots different from regular machinery are that robots usually function
by themselves, are sensitive to their environment, adapt to variations in the environment or to
errors in prior performance, are task oriented and often have the ability to try different methods
to accomplish a task.
RHex travels at speeds approaching one body length per second over height variations exceeding
its body clearance (see Extensions 1 and 2). Moreover, RHex does not make unrealistically high
demands of its limited energy supply (two 12V sealed lead-acid batteries in series, rated at
2.2Ah): at the time of this writing (Spring 2000), RHex achieves sustained locomotion at
maximum speed under power autonomous operation for more than fifteen minutes. The robot’s
design consists of a rigid body with six compliant legs; each possessing only one independently
actuated revolute degree of freedom. The attachment points of the legs as well as the joint
orientations are all fixed relative to the body. The use of spoke wheels (or even highly treaded
wheels) is of course an old idea.
Comparable morphologies such as rimless wheels or single spoke wheels have been previously
proposed for mobile platforms. Some compliant legged designs have been proposed for toys and
some rigid rimless wheeled designs have actually been commercialized by the toy industry.
However, the major difference between a single leg and a wheel with more than two spokes
arises from the far greater range of control over the ground reaction forces (GRF) that the former
affords relative to the latter. Wheels afford control primarily over the horizontal component of
the GRF (assuming flat ground) through friction, incurring an essentially uncontrolled
concomitant vertical component. In contrast, a leg, by admitting selection over the angle of
12
Name L(m)b M(kg)b V(m/s)b V/L
CW Robot
II [11]
0.5 1 0.083 0.16
Dante II [5] 3 770 0.017 0.006
Atillaa [4] 0.36 2.5 0.03 0.083
Genghisa [3] 0.39 1.8 0.038 0.097
ASVa [29] 5 3200 1.1 0.22
Boadicea
[6]
0.5 4.9 0.11 0.22
Sprawlita
[12]
0.17 0.27 0.42 2.5
RHexa 0.53 7 0.55 1.04
contact, yields a GRF whose direction as well as magnitude may be substantially controlled. As
soon as multiple spokes are added, the inter-spoke angle restricts the range of contact angles,
thereby diminishing control affordance. Our design preserves the possibility of achieving full
GRF range while adding the virtues of tuned compliance, heretofore associated only with
wheels.
The closest extant robots, one significant source of inspiration for the RHex design, are the
second author’s Scout class quadrupeds that also feature compliant legs, and reduce mechanical
Complexity by the restriction of one actuator per leg2. The central difference with respect to this
design is the possibility of re-circulating i.e., treating the singly actuated leg as a single spoke
‘rimless wheel’. A second key design influence whose careful consideration exceeds the scope
of this paper arises from biomechanics. R.J. Full’s video of a Blaberus cockroach racing
seemingly effortlessly over the rough surface illustrated in Figure 2, was shown at an
interdisciplinary meeting motivating and initiating the development of RHex. The present design
may be seen as instantiating the notion of a ‘ preflex ‘ implemented here in the clock driven
mechanically self stabilizing compliant sprawled posture mechanics that Full proposed3.The
notion of a ‘clock driven’ mechanism arises in our choice of an controller to derive appropriate
advantage of RHex’s mechanical design. At the time of this writing, RHex operates by tracking
(via local PD consol) at each hip joint a copy of the reference trajectory depicted in Figure 4 that
enforces an alternating tripod gait in an otherwise open loop manner. The two tripods are driven
in relative antiphase. The three legs of a tripod are driven simultaneously through a slow
‘retraction’ phase,
putatively corresponding to ground contact, followed by a fast ‘protraction’ phase designed to
recirculate the legs away from the the ground around the axle just in time to reach the next
‘retraction’ phase, putatively as the opposing tripod begins its ‘protraction’ by rotating away
from ground contact. No design we are aware of has heretofore incorporated this combination of
controller simplicity, leg compliance, limited actuation and overall morphology, and no
previously implemented legged vehicle has achieved the performance we now report.
TABLE I
Summary of Published Performance Reports: Hexapedal Robot
13
Table I modeled on, but extended from summarizes performance data for previous hex pedal
vehicles respecting which we are aware of documented performance, with citations to refereed
publications. It would be of considerable interest to compare across a broader range of machines.
Unfortunately, it is not straightforward to normalize against morphology. For example, ‘body
lengths per second’ is clearly not an appropriately normalized measure of bipedal speed. We
look forward to the eventual adoption of appropriately general performance metrics for legged
locomotion within the robotics research community. For the present, it seems most useful to
compare the design of RHex with some of its more closely related forebears. One of the better
documented, faster, power autonomous hexapods, the OSU adaptive suspension vehicle (ASV)
was designed to operate in the statically stable regime.
The deleterious consequences of design complexity have been observed in Dante II], a tethered
hexapod whose exposure to severe environmental conditions have apparently been the most
extreme of any robot yet documented in the archival literature. On a smaller scale, there have
been many platforms inspired by insect locomotion [3, 4, 6], all designed for statically stable
gaits. Their speeds were thus limited even though their design afforded greater kinematic
freedom over limb motions. A notable exception in the smaller scale is Sprawlita a tethered
hexapod which can achieve a very impressive 2.5 body lengths per second locomotion speed as a
result of its careful (compliant leg) design, and construction (off board pneumatic actuation and
small size).For most of these machines, rough terrain performance and obstacle crossing
capabilities are not carefully documented in the literature. There are only a few examples where
such capabilities are reported in detail , but even these are not suitable for assessing relative
performance due to differences in scale and the lack of a consistent set of experiments and
measures. Without more or less uniform standards of reporting, it becomes very difficult to test
the claim that the relative speed (we use body lengths per second), relative endurance (we use
specific resistance but also provide actual run-time data as well), relative mobility (we provide a
metric characterization of the various terrain features) of one design is superior to another. Thus,
beyond the specifics of design and performance, we believe that the paper makes a distinct
contribution to the robotics literature by establishing new standards of rigor in empirical
performance reporting for legged vehicles.
In summary, we believe this new design opens up a large range of new possibilities for control
of locomotion, while still meeting the constraints imposed by contemporary actuation and energy
storage technology on engineering autonomous robotic platforms. At the present time, we are
unable to provide a mathematically informed analysis of how and why RHex performs over the
range of reported behaviors. Instead, in this first archival paper, we present careful empirical
documentation of a narrow but very useful behavioral suite a base range of locomotion
capabilities at relatively high speeds over relatively challenging terrain and observe that no other
power autonomous legged design has ever before been demonstrated to exhibit a comparable
breadth of mobility behaviors.
14
RHex was the first legged machine to run over badly broken, unstable terrain, and the first
autonomous legged platform to run at speeds above one body length per second.
The original concept for RHex was introduced by Martin Buehler (then Director of the
Ambulatory Robotics Lab at McGill University, Canada ), inspired by observations about
cockroach running offered by Robert Full at the University of California, Berkeley. New sensorbased
behaviors arose from the addition to the team of Al Rizzi (then at the CMU Robotics
Institute). Philip Holmes at Princeton Unviersity and John Guckenheimer at Cornell University
maintained a participation in the RHex effort stemming from their original participation in the
Computational Neuromechanics project.
RHex is designed to be an all-terrain walking robot that can deal with curbs, stairs, puddles,
rubble, sinkholes, and other obstacles to accomplish rescue missions or carry out sensor surveys
in inhospitable areas. While the RHex has been around for over a decade, a modified version
called XRL (X-RHex-Light) is now being taught some new tricks by UPenn’s Professor Daniel
Koditschek.
robot that can go anywhere, even over terrain that might be broken and uneven. These latest
jumps greatly expand the range of what this machine is capable of, as it can now jump onto or
across obstacles that are bigger than it is.’
RHex is a power – and computation – autonomous hexapod robot with compliant legs and only
one actuator per leg. It is the first documented autonomous legged machine to have exhibited
general mobility (speeds at bodylengths per second) over general terrain (variations in level at
bodyheight scale).
RHex is presently capable of speeds exceeding five body lengths per second (2.7 m/s), negotiates
a wide variety of rugged terrains over thousands of bodylengths (3700 m distance on one set of
batteries), manages slopes exceeding 45 degrees, swims, and climbs stairs.
RHex arises from a multidisciplinary and multi-university DARPA funded effort in
Computational Neuromechanics that applies mathematical techniques from dynamical systems
theory to problems of animal locomotion, and, in turn, seeks inspiration from biology in
advancing the state of the art of robotic systems. The RHex project received $5 million over 5
years from the DARPA CBS/CBBS program in 1998, and an approximate additional $3 million
from other grants, such as National Science Foundation grants.
RHex acquired a large number of capabilities in its behavioral repertoire. In fact, it is the only
robot that is capable of performing such a wide variety of behaviors as a single, autonomous
15
robot. This performance is due to the significant amount of inspiration from the study of
biological systems, leading to a number of principles underlying RHex’s design.
‘ The use of legs instead of wheels or tracks opens the way for a large number of behaviors
‘ Passive compliance in the legs overcomes limitations of underactuation and helps
simplify mechanical design, yielding robustness
‘ Sprawled posture, inspired from insects, results in passive stabilization of lateral motion
‘ Control is open-loop at the gait level, but closed loop at the task level. Stability comes as
a result of passive mechanics, not high-bandwidth active control
‘ Running on reasonably flat, natural terrain at speeds up to 6 body lengths per second (just
over 2.7 m/s)
‘ Climbing a wide range of stairs
‘ Climbing slopes up to 45 degrees
‘ Climbing slopes up to 45 degrees
‘ Traverse obstacles as high as 20 cm (about twice RHex’s leg clearance)
‘ Continuously run for 45 minutes, covering up to 3 miles with an efficient gait
‘ Successfully traverse badly broken terrain with large rocks and obstacles
‘ Walk and run upside down
‘ Flip itself over to recover nominal body orientation
‘ Leaping across ditches up to 30 cm wide
‘ Support remote control from up to 150m distance
robot that will be able to climb and jump, which could be used in goods transport or military
activity by using its new functions to cross dangerous or rough environments and terrain.
The RHex’s leg-like structure allows it to traverse obstacles in ways that wheels cannot.
Using its legs in different sequences, the RHex robot can jump and mount different objects such
as a wall, where it can launch itself and grasp the surface and then use its front legs to drag the
rest of its body over the object.
look at any machine that’s been built today, and almost any animal that you can imagine will
outperform that machine
16
CHAPTER 2
Brief History of the work
The RHex project arose from an earlier DARPA DSO effort initiated within the 1998
CBS/CBBS program called Computational Neuromechanics.
R-hex robot is invented for the spying purpose in the battle field and it can also be used as a
weapon. At the time of second world war German’s were using trained dogs to plant a bomb
under the enemy tanks, but somehow dogs were not a working as trainers wanted. Sometimes
dogs were planting the bombs of their own tanks.
For the same purpose this robot is invented and its is made like an insect with six legs so that in
battlefields It can’t get tracked down very easily, and it can easily go to the enemy location. Any
soldier can handle this robot from a far distance and this robot has a camera on board so the
soldier can have a live feed and it can run the robot as per requirement, it can be also used to
sneek out to the enemy base. So this is one try to make something which will work to collect the
information and as well as weapon without harming human lives.
The RHex project received $5 million over 5 years from the DARPA CBS/CBBS program in
1998, and an approximate additional $3 million from other grants, such as National Science
Foundation grants. The following Universities participated on the initial RHex project:
The University of Michigan, Ann Arbor, MI
McGill University, Montreal, Canada
Carnegie Mellon University, Pittsburgh, PA
University of California, Berkeley, CA
Princeton University, Princeton, NJ
Cornell University, Ithaca, NY
17
18
The RHex project aims to develop a six legged robot, capable of achieving a wide variety of
dynamically dextrous tasks, such as walking, running, leaping over obstacles, climbing stairs,
with a single autonomous platform. Our emphasis is on mechanical simplicity and the
exploration of control strategies designed to work with the natural dynamics of the robot.
Behaviors
‘ Basic alternating tripod gait.
o Walking forward and backward with differential turning
o Turning in place
o Walking upside down (no automatic detection)
RHex is primarily an all-terrain robot solution. BigDog and its contemporaries are impressive
enough, but their delicate stepping can be foiled by water, large obstacles, or uneven terrain. Not
RHex. With a simple yet versatile mode of travel, the robot can step, jump, or climb over just
about anything before it. The unit can be made to be totally amphibious, swimming while
completely submerged and still ready for anything once it hits the shore.
RHex can now launch itself over gaps that are larger than the robot itself, and the carbon fiber
shell can withstand the punishment of falling from even great heights.
Readings from each leg are used to change movement strategy on the fly.
Perhaps the most impressive aspect of RHex at this point is how it can adjust its movement based
on the situation. Force sensors let feedback from the legs dictate the specifics of motion ‘
running on concrete is best achieved with forceful footfalls, but moving over pebbles or grass
requires a softer approach. By adjusting the basic style of movement to everything from the
contours to the materials of the ground, it can attack all-terrain problems like no other robot
before it.
19
Models Avialable
‘ RHex 0.8 – New 4-bar legs, electronics redesign
‘ RHex 0.9 – New half-circle legs
‘ SHelly – Included a waterproof fiber glass shell
‘ RHex 1.1 – Included a Firewire video camera for real time image processing
‘ RHex 1.1 – with Leg sensors – Included legs equipped with strain gauges and
independent wireless communication devices.
‘ Rugged RHex- Waterproof aluminum shell, larger motors and larger battery. Developed
by Mecheligent for military purposes.
‘ Aqua 1.0 – Waterproof aluminum shell, legs replaced by hybrid leg/fin for swimming.
Developed at McGill University
‘ Aqua 2.0 – Redesigned aluminum shell, increased depth rating, smaller displacement
‘ EduBot – Educational version developed at the University of Pennsylvania
Comparisions
Claimed Patent model
‘ High price
‘ Advanced microcontroller
‘ Complex programming
‘ Metal body
‘ Heavy weight
‘ More battery consumption
‘ High torque motors
Our model
‘ Low price
‘ 8051 microcontroller
‘ Easy programming
‘ Light weight
‘ Less battery consumption
‘ Low torque motors
20
CHAPTER 3
R-HEX ROBOT
3.1 Detailed Description Of The Invention
3.1.1 legs
Although the invention is illustrated and described herein with reference to specific
embodiments, the invention is not intended to be limited to the details shown. Rather, various
modifications may be made in the details within the scope and range of equivalents of the claims
and without departing from the invention.
Animals, unlike most current robotic systems, are able to adjust the physical properties of their
limbs as well as their control parameters to help them adapt to changing conditions in their
environment. One of the challenges in the field of robotic legged locomotion is to develop active,
programmable mechanisms to endow robotic structures with the kind of adaptability and
robustness found in biological systems.
One approach for improving robotic leg locomotion involves incorporating tunable mechanical
leg stiffness. The hypothesis behind this approach is that tuned resonant running leads to energy
efficient and stable locomotion. Matching the leg stiffness to the leg swing frequency can
minimize the amount of motor work that must be inserted during each stance phase. Such
tunable leg stiffness can be used to improve robot speed and stability.
Tuning of leg stiffness can be beneficial in a hex pedal robot, such as the one shown in FIG. 1,
which serves as an exemplary platform for the leg design according to aspects of the present
invention. Additional details regarding an example of such a hex pedal robot are described in
U.S. Pat. No. 6,481,513 (Single Actuator per Leg Robotic Hexopod), the contents of which are
incorporated herein by reference in their entirety.
Legs that can individually adjust their stiffness can be especially beneficial for multi-legged
runners. Functional specialization in the front, middle, and rear legs of hexapedal runners can
contribute to their stability, and running quadrupeds may respond faster to perturbations in
ground height if leg stiffness is increased. Additionally, run-time alteration of the passive
compliance of individual pairs of legs may allow a robot to more successfully adapt to changes
in the running environment.
There are several methods for mechanically adjusting leg stiffness. In one design for a bipedal
system, the Biped with Mechanically Adjusted Series Compliance (BiMASC) uses an
antagonistic set-up of two non-linear fiberglass springs to store and return energy. A complex
system of cables and two motors adjusts the set point and pretension on the fiberglass springs.
This device demonstrates variable stiffness, but there is some inefficiency at storing and
returning energy during hopping that may be attributed to the fact that in an antagonistic spring
arrangement only one spring actually compresses to store energy while the other relaxes to
21
transfer energy into the compressing spring. Furthermore, the internal forces generated by
antagonistic spring arrangements may increase the frictional losses of the system.
Tunable stiffness can also be achieved using antagonistic pneumatic actuators such as McKibben
actuators and pleated pneumatic artificial muscle. Although stiffness control has been achieved
through pneumatic actuation, the power requirements for pneumatics can make it difficult to
implement on any autonomous dynamic legged locomotion system.
Another approach, perhaps better suited for implementation on small robots, is the method of
structure-controlled stiffness where a mechanical change in the device alters the stiffness of a
spring element. For example, a passive spring element may be constructed from several layers of
flexible sheets. The mechanical impedance of the passive element is adjusted by controlling the
connectivity of the layers through an external stimulus such as a vacuum. In another example,
the mechanical impedance of robot finger joints is adjusted by changing the effective length of a
leaf spring. Also, a tunable helical spring concept in which stiffness is adjusted by controlling the
number of active coils can be utilized.
Alternatively, leg stiffness can be adjusted by sliding an element along the length of ‘C-shaped’
compliant legs. The portion of the leg covered by the element is assumed to be rigid, while the
remaining exposed portion is considered to be compliant. The overall stiffness can be varied by
as much as 90%.
Maintaining consistent tip trajectory for the continuous range of stiffness settings can be
beneficial in a tunable leg. Specifically, the deflection path of the leg spring may respond
differently to applied loads depending on the stiffness setting. Such configurations can make it
difficult to determine whether a tunable leg performed better or worse due to the change in
stiffness or to the altered deformation behavior.
Increasing the stiffness of the leg spring with a rigid slider may also shift the center of mass.
Making a slider rigid can require a more massive structure to resist deformation during the stance
phase. Adjusting the rigid slider position to increase leg stiffness can cause the leg moment of
inertia to shift away from the axis of rotation. This can significantly increase the loads on the
motor due to leg acceleration changes during each stride.
Passive compliant C-shaped legs can enable the robot to navigate rough terrain by allowing
compliant ground contact anywhere along the length of the leg. A leg design with a rigid slider
can, however, effectively limit the leg length that is capable of absorbing impacts. Legs are
generally stiffer at higher speeds where the potential for damage from collisions is greatest.
According to embodiments of this invention, a variable stiffness leg design can improve upon the
rigid slider configuration, improve the efficiency of the leg, and incorporate an actuation system
to enable autonomous stiffness adjustment. It can provide a small, light, and robust limb that can
22
be employed on a robot to empirically test the proposed advantages of variable compliance limbs
in running. In particular, the effect of changing stiffness can reduce the impact of other factors,
such as leg length, damping, or deflection path.
RHex (short for "robot hexapod" and pronounced "Rex") is actually more than a decade old.
On robots, legs are more effective than wheels when it comes to rough terrain. But it can be
complicated to teach the human-like legs on walking robots how to respond to unpredictable
conditions. RHex’s simple, one-jointed legs are better suited to getting around obstacles in
creative ways.
RHex platforms all include six legs, each with a single rotary actuator at the hip. Legs are
designed from compliant materials to produce energetic running gaits. The leg modules are
controlled from a central computer, which takes user commands or sensor feedback to decide
how the legs should move.
RHex climbs in rock fields, mud, sand, vegetation, railroad tracks, telephone poles and up slopes
and stairways.
Why a Legged Robot?
Legs have an advantage over wheels in terms of rough terrain. But there is a drawback with the
articulated legs usually found on walking robots; they require complex, specialized instructions
for each moving part. To get the most mobility out of RHex’s simple, one-jointed legs, Penn
researchers are essentially teaching the robot Parkour.
Taking inspiration from human free-runners, the team is showing the robot how to manipulate its
body in creative ways to get around all sorts of obstacles.
23
3.1.2 Operation:
Locomotion of robotic device is controlled by computing system as it drives each
compliant leg via power drive system. As described above, compliant legs are
arranged such that three are disposed on opposing sides of rigid body, thereby
forming the left and right tripod pattern. Specifically, the left tripod includes the
left front leg, the left rear leg, and the right middle leg. Similarly, the right tripod
includes the right front leg, the right rear leg, and the left middle leg. Therefore, the
left and right tripods each form a sturdy, reliable sprawling base support. During
locomotion, the left tripod is synchronized and is 180?? out of phase with the right
tripod’therefore producing an alternating tripod gait (see FIG. 2).
More particularly, as seen in FIG. 3, the target trajectory of the left and right
tripods, represented as a dashed line and a solid line, respectively, is a periodic
function of time according to four variables: tc, ts, ??s, and ??o. In a single cycle,
both tripods, and consequently each compliant leg , go through a slow swing phase
??s, generally while in contact with the ground, and a fast swing phase 2”?s,
generally while not in contact with the ground. The period of a complete rotation
of a single compliant leg is tc, while the duration of such slow swing movement is
ts. Similarly, the leg sweep angle for slow leg swing is ??s and the leg angle offset is
??o. Accordingly, tc and ts represent the duty factor of each tripod. As seen in FIG.
3, there is a duration of time when all six legs are in contact with the ground, td.
This duration is determined by the duty factor of both tripods. Finally, the
??o parameter offsets the motion profile with respect to the vertical. It is important
to note that although both profiles are monotonically increasing in time, these
profiles may be reversed to enable backward locomotion.
In order to turn robotic device in place, compliant legs on opposing sides of robotic
device operate in opposite directions. That is, three compliant legs on one side of
robotic device change direction. The turning direction of robotic device depends
upon the rotational direction of the left and right tripod sets. However, each set of
tripods is still synchronized internally in order to maintain at least three compliant
legs in contact with the ground at any one time to maintain stability. Similar to the
control of the forward or backward locomotion speed, the rate of turning depends
on the choice of the particular motion parameters, mainly tc and ??s.
24
Dynamic locomotion with compliant legs permits not only higher speeds and the
potential for drastically improved mobility compared to statically stable machines,
but at the same time permits these improvements with greatly simplified leg
mechanics.
Prior art legged hexapods required the use of complex legs having at least three
actuated degrees of freedom. These actuated degrees of freedom each required an
individual actuator which contributed greatly to the mechanical complexity, unit
weight, and cost of the robotic device. However, according to the principles of the
present invention, a simplified legged hexapod is provided that requires only a
single actuated revolute degree of freedom, thereby eliminating the need for the
additional actuators. Minimizing energy losses in body movement is achieved
through the use of compliant legs that permit the absorption of a portion of the
ground reaction forces by the compliant legs.
When robotic device turns upside-down, robotic device continues operation after
the ??o parameter is changed by 180??. This can be accomplished automatically via
sensors or accomplished manually via input from the operator (i.e. remote control).
The description of the invention is merely exemplary in nature and, thus, variations
that do not depart from the gist of the invention are intended to be within the scope
of the invention. Such variations are not to be regarded as a departure from the
spirit and scope of the invention.
25
3.2 body structure:
Fig 1 : Rigid body
26
Fig 2: Rigid body structure
27
28
Fig 3 : Rigid body structure
29
Fig 4 : Rigid body structure
Fig 5: legs
30
Fig 6: legs
31
3.3. CIRCUIT DIAGRAM :
Fig 7 : Circuit Diagram
32
Fig 8 : Circuit Diagram
33
Fig 9 : Remote Control
34
Fig. 10 : Pin Dia. Of Microcontroller
35
Fig. 11 : Block Dia. Of Microcontroller
36
PROGRAM
Void loop{}{
Int tback=300;
Int tTurn=200;
Digital Write(EN 12,HIGH);
Digital Write(EN34,HIGH);
Digital Write(EN56,HIGH);
If(Digital Read(L)**O,Digital Read(R)==1;
{
Digital Write(a1,Low);
Digital Write(a2,High);
Digital Write(a3,Low);
Digital Write(a4,High);
Digital Write(a5,Low);
Digital Write(a6,High);
Delay(tback);
Digital Write(a1,High);
Digital Write(a2,Low);
Digital Write(a3,Low);
Digital Write(a4,High);
Digital Write(a5,High);
Digital Write(a6,Low);
37
Delay(tBack)
Digital Write(a1,Low);
Digital Write(a2,High);
Digital Write(a3,High);
Digital Write(a4,Low);
Digital Write(a5,Low);
Digital Write(a6,High);
Delay(tTurn);
}
38
3.4.RECEIVER PARTS :
RESISTORS:-
R3- – – – – – -1K??
R4- – – – – – -10K??
CAPACITORS:-
C1- – – – – – -10??F/25V
C2, C4- – – – – -33PF
C3, C5- – – – – -100 ??F/25V
SEMICONDUCTOR:-
U2- – – – – – -L293D
U7- – – – – – -L7805
U7A- – – – – – -74LS14
M1- – – – – – -89c251
D1, D3, D5, D7 – – – -1N4148 DIODE
MISC.:-
Y1 – – – – – -11.0592MHZ CRISTAL
L1, L2 – – – – -RED LED
SW1-SW4 – – – – -PUSH ON SWITCH
PB2 – – – – – -2 PIN CONNECTOR
433 MHZ RF MODULE
39
3.5 TRANSMITTER PARTS:
RESISTORS:-
R1 – – – – – -8.2K??
R3, – – – – -1K??
RN1- – – – – -10K??
CAPACITORS:-
C3- – – – – – -10??F/25V
C1, C2- – – – – -33PF
SEMICONDUCTOR:-
U1- – – – – – -AT89C2051
U3- – – – – – -L7805
MISC.:-
X1 – – – – – -11.0592MHZ CRISTAL
L1, L2 – – – – -RED LED
SW1-SW2 – – – – -PUSH ON SWITCH
433 MHZ RF MODULE TX
ICS SOCKET
40
CONCLUSION
Nimble, robust locomotion over general terrain remains the sole province of animals,
notwithstanding our functional prototype, RHex, nor the generally increased recent interest in
legged robots. RHex, endowed with only a rudimentary
Controller uses what might be termed the engineering equivalent of ‘preflexes’ to negotiate
relatively badly broken terrain at relatively high speeds performance beyond that heretofore
reported for autonomous legged vehicles in the archival literature.
We are convinced that further systematic application of certain operational principles exhibited
by animals will achieve significant increases in RHex performance, and inform the evolution of
the underlying mechanical design of future prototypes as well. To conclude the paper, we
provide a brief sketch of these principles and how they may be applied. Accumulating evidence
in the biomechanics literature suggests that agile locomotion is organized in nature by recourse
to a controlled bouncing gait wherein the ‘payload’, the mass center, behaves mechanically as
though it were riding on a pogo stick.
While Raibert’s running machines were literally embodied pogo sticks, more utilitarian robotic
devices such as RHex must actively anchor such templates within their alien morphology if the
animals’ capabilities are ever to be successfully engineered. We have previously shown how to
anchor a pogo stick Template in the more related morphology of a four degree of freedom
monopod. The extension of this technique to the far more distant hexapod morphology surely
begins with the adoption of an alternating tripod gait, but its exact details remain an open
question, and the ‘minimalist’ RHex design (only six actuators for a six degree of freedom
payload!) will likely entail additional compromises in its implementation. Moreover, the only
well understood pogo stick is the Spring Loaded Inverted Pendulum, a two degree of freedom
sagittal plane template that ignores body attitude and all lateral degrees of freedom.
Recent evidence of a horizontal pogo stick in sprawled posture animal running and subsequent
analysis of a proposed lateral leg spring template to represent it advance the prospects for
developing a spatial pogo stick template in the near future. Much more effort remains before a
functionally biomimetic six degree of freedom ‘payload’ controller is available, but we believe
that the present understanding of the sagittal plane can already be used to significantly increase
RHex’s forward speed, and, as well, to endow our present prototype with an aerial phase.
41
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