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1. DESIGN OF ROCKER-BOGIE MECHANISM

2. ABSTRACT
 It is obvious that rovers are important vehicles of today’s solar system
exploration.
 Most of the rover designs have been developed for Mars and Moon surface in
order to understand the geological history of the soil and rocks
 Rocker-bogie suspension system, has a natural advantage with linear bogie motion
which protects the whole system from getting rollover during high speed
operations. This improvement increases the reliability of structure on field
operations and also enables the higher speed exploration with same obstacle height
capacity as rocker-bogie. The bogie suspension is a type of oscillating
mechanical suspension with multi-leaf springs which is used in agriculture to fit
tandem vehicles.

3. INTROUCTION
 The Rocker-Bogie system is the suspension arrangement used in the Mars
rovers (mechanical robot) introduced for the Mars Pathfinder and also used on the Mars
Exploration Rover (MER) and Mars Science Laboratory (MSL) missions. It is
currently NASA's favored design.
 The term “rocker” comes from the rocking aspect of the larger links on each side of the
suspension system. These rockers are connected to each other and the vehicle chassis
through a differential. Relative to the chassis, when one rocker goes up, the other goes
down. The chassis maintains the average pitch angle of both rockers.
 One end of a rocker is fitted with a drive wheel and the other end is pivoted to a bogie.

4.  The term “bogie” refers to the links that have a drive wheel at each end. Bogies were
commonly used as load wheels in the tracks of army tanks as idlers distributing the load
over the terrain. Bogies were also quite commonly used on the trailers of semi-trailer
trucks. Both applications now prefer trailing arm suspensions.
 The rocker-bogie design has no springs or stub axles for each wheel, allowing the rover to
climb over obstacles, such as rocks, that are up to twice the wheel's diameter in size while
keeping all six wheels on the ground. As with any suspension system, the tilt stability is
limited by the height of the center of gravity.

5. PROBLEM STATEMENT
 The rovers are only capable to move on terrain surface or avoid obstacles,
but it can be enhanced for stair climbing.
 The speed of rovers is comparatively slow which can be increased by
implementing the idea of separate motor for each wheel.
 If the inclination exceeds above 45 degree, the weight will not be in
balanced position.

6. Objective of the Mini Project
 The objective of the min project is to design a small, robust and highly
maneuverable rover robot.
 It will be designed for working on the different platformer like rough
terrain, smooth surfaces, over coming obstacles in its path and climbing
over the obstacles of certain height, choosing different predetermined
gaits and to have good stability, speed as well as payload capacity.

7. Scope of the Mini Project
 To work on different surfaces like rough terrain, dusty, smooth surfaces.
 Climbing predetermined stairs
 To achieve maximum distance in single charge along with high speed.
 Avoiding use of spring as suspensions to reduce the weight and cost

8. LITRATURE SURVEY
YEAR AUTHOR COUNTRY OBJECTIVE CONTRIBUTION DATA CONCLUSION/ Result
August
2018
B.BABU,
N.DHAYANIDHI,
S.DHAMOTHARAN
India. “Rocker Bogie mechanism
Geosurvey Rover” deals with the
important aspect of improving
the rover from its previous
designs. The Geosurvey rover has
to operate on rough and harsh
environments for which it was
designed but several factors
restrict its operational
capabilities, so the focus of our
research is to overcome
restrictions or to decrease it to
within an acceptable range for its
smooth performance..
Various tests were conducted to
determine how the improved
geosurvey rover would perform
against its predecessor designs
by use of Negative Moment vs.
Obstacle Height and their
responses were obtained and
their graphs were plotted and
comparisons were made.
problem associated
with current suspension
systems is slow speed of
motion which derails the rhythm
to absorb the shocks generated
by wheels which remain the
result of two factors. First, in
order to pass over obstacles the
vehicle must be geared down
significantly to allow for enough
torque to raise the mass of the
vehicle. Second, if the vehicle is
travelling at a high speed and
encounters an obstacle there will
be a large shock transmitted
through the chassis which could
damage the suspension or
topple down the entire vehicle
This work shows how rocker bogie
system works on different surfaces.
As per the different weight acting
on link determines torque applied
on it. By assuming accurate stair
dimensions, accurately
dimensioned rocker bogie can
climb the stair with great stability.
The design and manufactured
model can climb the angle up to
45˚. Also we tested for the Web
cam with AV recording mounted
on rocker bogie system and found
satisfactory performance of its
capabilities for providing image
and video data.

9. YEAR AUTHOR COUNTRY OBJECTIVE CONTRIBUTION DATA CONCLUSION/ Result
May. - Jun.
2015
Nitin Yadav,
BalRam
Bhardwaj,
Suresh
Bhardwaj
India. analysis of Rocker Bogie
Suspension System and
Access the possibility to
implement in Front
Loading Vehicles
the realized simulation, the
results has been generated and
analyzed which comparing the
disturbances in the ATV’s Centre
of Gravity position in each of
the two operating modes,
contrasting the response of
these two distinctive
configurations of the rocker-
bogie suspension against
upcoming obstacles that can be
present along the system
generated obstacles and
roadblocks.
A The main problem
associated with current
suspension systems installed
in heavy loading vehicles
rovers (including those with
active and semi active
suspension systems) is their
slow speed of motion which
derail the rhythm to absorb
the shocks generated by
wheels which remain the
result of two factors. First, in
order to pass over obstacles
the vehicle must be geared
down significantly to allow
for enough torque to raise
the mass of the vehicle.
Consequently, this reduces
overall speed which cannot
be tolerated in the case of
heavy loading vehicles.
Second, if the vehicle is
travelling at a high speed and
encounters an obstacle
Presented situation was faced
presenting two modes of
operation within same working
principle which is a rocker-
bogie system with a robust
obstacles traverse features and
another is an expanded support
hexagon achieved by rotating
the bogies of each side of the
vehicle. The proposed
modification increases in the
stability margin and proved
with valuable and profitable
contrasting the SSF metric with
the 3D model simulations done
in SOLIDWORKS

10. METHODOLOGY
 As per the research it is find that the rocker bogie system reduces the motion by half
compared to other suspension systems because each of the bogie's six wheels has an
independent mechanism for motion and in which the two front and two rear wheels have
individual steering systems which allow the vehicle to turn in place as 0 degree turning
ratio.
 Every wheel also has thick cleats which provides grip for climbing in soft sand and
scrambling over rocks with ease. In order to overcome vertical obstacle faces, the front
wheels are forced against the obstacle by the center and rear wheels which generate
maximum required torque.
 The rotation of the front wheel then lifts the front of the vehicle up and over the obstacle
and obstacle overtaken. Those wheels which remain in the middle, is then pressed against
the obstacle by the rear wheels and pulled against the obstacle by the front till the time it
is lifted up and over.
 At last, the rear wheel is pulled over the obstacle by the front two wheels due to applying
pull force. During each wheel's traversal of the obstacle, forward progress of the vehicle
is slowed or completely halted which finally maintain vehicles center of gravity.

11. Sojourner examining the rock named “Yogi” (Courtesy of
NASA/JPL-Caltech)
Rocky terrain on the rim of crater Bonneville

12. NASA - JPL Sojourner Rover (Courtesy of
NASA/JPL-Caltech)
Inflatable Rover (Courtesy of
NASA/JPL-Caltech)
Rocky 7 Rover (Courtesy of NASA/JPL-
Caltech)
Sample Return Rover - (SRR) (Courtesy of NASA/JPL-Caltech)
Micro5 rover with suspension named
Pegasus
Illustration of Mars Exploration
Rover (Courtesy of NASA/JPL-
Caltech)

13. WORKING PRINCIPLE
 The rocker-bogie design consisting of no springs and stub axles in each wheel which
allows the chassis to climb over any obstacles, such as rocks, ditches, sand, etc. that are up
to double the wheel's diameter in size while keeping all wheels on the ground maximum
time.
 As compared to any suspension system, the tilt stability is limited by the height of the
center of gravity and the proposed system has the same. Systems employing springs tend
to tip more easily as the loaded side yields during obstacle course. Dependent upon the
center of overall weight, any vehicle developed on the basis of Rocker bogie suspension
can withstand a tilt of at least 50 degrees in any direction without overturning which is the
biggest advantage for any heavy loading vehicle. The system is designed to be
implemented in low speed working vehicles such as heavy trucks, Bulldozers which works
at slow speed of around 10 centimeters per second (3.9 in/s) so as to minimize dynamic
shocks and consequential damage to the vehicle when surmounting sizable obstacles.

14. ROCKER GEOMETRY
Kinematic diagram of Rocker-Bogie suspension
LBS kinematic diagram
Articulated Suspension System

15. Action Plan
 Studding Literature survey for broad understanding of Rockers bogie.
 Finding Problem, objectives, advantages, disadvantages and application of
the project.
 Determining Design Parameters to achieve the objectives.
 Calculating the actual dimensions of the parts.
 Forming a 3D model in solid works software.
 Documentation

16. ADVANTAGES
 Its main advantage is that vehicles can travel across particularly rough terrain,
thanks to the wide oscillation movements which adapt to the roughness of the
ground.
 With 6 wheels ,it allows the rovers to overcome larger obstacles with better tilt
stability.
 This mechanism allows climbing obstacles twice the size of wheel diameter.
 Does not employ springs and stub axles.
 Equal distribution of load on all wheels.
 Independent movement of rocker on either sides of the bogie.
 The front and back wheels have individual drives for climbing, enabling the rover
to traverse obstacle without slip.
 The design is simple and reliable.

17. DIADVANTAGES
 It is highly unstable at high speeds. At high speeds it experiences head on collision
of wheels with obstacles. This would cause an impulsive force to act on front
wheels. This impulse may damage the bogie.
 The impulsive collisions also decrease the climbing capability of the system. They
decrease the grip of wheels on ground hence the tractive force of ground reduces.

18. APPLICATION
 Automobile industry
 Army tankers.
 Material handling system.
 Agriculture equipment manufacture.

19. REFERENCES
 B.Vilcox, T.Nguyen, Sojourner on Mars and Lessons Learned for Future Planetary
Rovers, ICES, 1997
 Design analysis of Rocker Bogie Suspension System and Access the possibility to
implement in Front Loading Vehicles Nitin Yadav , BalRam Bhardwaj, Suresh
Bhardwaj IOSR Journal of Mechanical
 National Aeronautics and Space Administration (NASA) Mars Exploration Rover
Landings Press Kit (January 2004)
 P.E.Sandin, Robot Mechanisms and Mechanical Devices Illustrated (McGraw Hill
– New York – 2003)
 J.C.Dixon, Tires, Suspension and Handling Second Edition, Society of
Automotive Engineers (Arnold – London – 1996)