Recent Developments in Electro-Mechanical Machining
cam report windshield wiper mechanism
1. (Automobile windshield wiper mechanism: Single
wiper of new Mercedes)
Name:
COMPUTER-AIDED ANALYSIS OF MECHANICAL SYSTEMS
ME 729 – FALL 2014
Instructor: Dr. H.M Lankarani,
Location: Wichita
Date:
2. Abstract
This paper introduces the outline of car windshield wiper mechanism: Single wiper of new
Mercedes. The single wiper is unique in relation to the wiper that we generally see on autos,
trucks and so on. Single wiper is utilized by Mercedes Benz as a remarkable style. This was
initially proposed by Mercedes and they have exploit single connection wiper arm to increase
geometrical criteria which a substantial wipe territory is accomplished. It is utilized to clean the
superfluous components that make diversion the driver. The outline of wiper is verging on like
the prior wipers with a couple changes yet the way accomplished is of W shape. The wiper a
solitary wiper stretches out outward to get closer to the top corners, and pulls in at the closures
and center of the stroke, clearing out a to some degree 'W'- formed way. These wipers are
additionally productive as it doesn't leave any indication of dust or water or snow. We might
want outline the system in a couple programming's and we incorporate the outcome sets,
diagrams and so on for the model.
3. Table of contents:-
1. Introduction
a) Inside the Wipers
b) Motor and Gear Reduction
c) Linkage
d) Wiper blades
e) Pivot points.
2. Background
a) Wipers
b) Geometry
c) Alternatives
3. Procedure
A. Description of the project.
B. Assumptions.
C. Modeling techniques.
D. Method of solution.
4. Results and Discussion
A. Results.
B. Discussion of precisely what the results mean.
C. Applications.
D. Limitations.
5. Conclusions and Recommendations
4. 1. Introduction
A windshield wiper is a device used to remove rain and debris from a windscreen. Almost
all motor vehicles, including trains, water craft and some aircraft, are equipped with such wipers,
which are usually a legal requirement. Most automobiles use two synchronized radial type arms,
while many commercial vehicles use one or more pantograph arms. To note, Mercedes-Benz
pioneered a system called the "Monoblade" where in a single wiper extends outward to get closer
to the top corners, and pulls in at the ends and middle of the stroke, sweeping out a somewhat
'W'-shaped path.
.
The first windshield wipers were operated manually by moving a lever inside the car back and
forth. Today, most of us take our electric windshield wipers for granted. The wipers faithfully
keep the window clear, moving back and forth across the windshield countless times as they
sweep the water away. On their highest speed, they move impressively fast, sometimes shaking
the car from side to side. What kind of a mechanism can move the wiper arms so effectively and
so reliably? Windshield wipers are found on car windshields, some car headlights, and
airplanes and even on the space shuttle.
Inside the Wipers
The wipers combine two mechanical technologies to perform their task:
1. A combination electric motor and worm gear reduction provides power to the
wipers.
2. A neat linkage converts the rotational output of the motor into the back-and-forth
motion of the wipers.
5. Motor and Gear Reduction
It takes a lot of force to accelerate the wiper blades back and forth across the windshield so
quickly. In order to generate this type of force, a worm gear is used on the output of a small
electric motor. The worm gear reduction can multiply the torque of the motor by about 50 times,
while slowing the output speed of the electric motor by 50 times as well. The output of the gear
reduction operates a linkage that moves the wipers back and forth. Inside the motor/gear
assembly is an electronic circuit that senses when the wipers are in their down position. The
circuit maintains power to the wipers until they are parked at the bottom of the windshield, and
then cuts the power to the motor. This circuit also parks the wipers between wipes when they are
on their intermittent setting.
Linkage
A short cam is attached to the output shaft of the gear reduction. This cam spins around as the
wiper motor turns. The cam is connected to a long rod as the cam spins; it moves the rod back
and forth. The long rod is connected to a short rod that actuates the wiper blade on the driver's
side. Another long rod transmits the force from the driver-side to the passenger-side wiper blade.
6. Wiper Blades
Wiper blades are like squeegees. The arms of the wiper drag a thin rubber strip across the
windshield to clear away the water. When the blade is new, the rubber is clean and has no nicks
or cracks. It wipes the water away without leaving streaks. When the wiper blades age, nicks or
cracks form, road grime builds up on the edge and it doesn't make as tight a seal against the
window, so it leaves streaks. Sometimes you can get a little extra life out of your wiper blade by
wiping the edge with a cloth soaked in window cleaner until no more dirt comes off the blade.
Another key to streak-free operation is even pressure over the length of the rubber blades. Wiper
blades are designed to attach in a single point in the middle, but a series of arms branch out from
the middle like a tree, so the blade is actually connected in six to eight places.
If ice or snow forms on these arms, it can make the distribution of pressure uneven, causing
streaks under part of the blade. Some wiper manufacturers make a special winter blade with a
rubber boot covering the arm assembly to keep snow and ice out.
Pivot Points
Most cars have pretty much the same wiper design:
Two blades move together to clean the windshield.
One of the blades pivots from a point close to the driver's side of the car, and the other
blade pivots from near the middle of the windshield.
This is the Tandem System in the figure below.
This design clears most of the windshield that is in the driver's field of view.
7. 2. Background
There are a couple of other designs on some cars. Mercedes uses a single wiper arm that extends
and retracts as it sweeps across the window -- Single Arm (Controlled) in the figure below.
This design also provides good coverage, but is more complicated than the standard dual-wiper
systems. Some cars use wiper blades that are mounted on opposite sides of the windshield and
move in the opposite direction, and some vehicles have a single wiper mounted in the middle.
These systems don't provide as much coverage for the driver as the standard two-blade system.
Rain-sensing Wipers
In the past, automakers have tried to either eliminate the wipers or to control their speed
automatically. Some of the schemes involved detecting the vibrations caused by individual
raindrops hitting the windshield, applying special coatings that did not allow drops to form, or
even ultrasonically vibrating the windshield to break up the droplets so they don't need to be
wiped at all. But these systems were plagued by problems and either never made it to production
or was quickly axed because they annoyed more drivers than they pleased. However, a new type
of wiper system is starting to appear on cars that actually do a good job of detecting the amount
of water on the windshield and controlling the wipers. The sensor projects infrared light into the
windshield at a 45-degree angle. If the glass is dry, most of this light is reflected back into the
sensor by the front of the windshield. If water droplets are on the glass, they reflect the light in
different directions -- the wetter the glass, the less light makes it back into the sensor.
The electronics and software in the sensor turn on the wipers when the amount of light reflected
8. onto the sensor decreases to a preset level. The software sets the speed of the wipers based on
how fast the moisture builds up between wipes. It can operate the wipers at any speed. The
system adjusts the speed as often as necessary to match with the rate of moisture accumulation.
The TRW system, which is found on many General Motors cars, including all Cadillac models,
can also be overridden or turned off so the car can be washed.
Geometry
Most wipers are of the pivot (or radial) type: they are attached to a single arm, which in turn is
attached to the motor. These are commonly found on many cars, trucks, trains, boats, airplanes,
etc. Modern windscreen wipers usually move in parallel (Fig. below).
However, various Mercedes-Benz models and other cars such as the Volkswagen sharan employ
wipers configured to move in opposite directions (Fig below), which is mechanically more
complex but can avoid leaving a large unwiped corner of the windscreen in front of the front-seat
passenger. A cost benefit to the auto-maker occurs when wipers configured to move in opposite
directions do not need to be repositioned for cars exported to right hand drive countries such as
the UK and Japan.
9. Another wiper design (Fig. below) is pantograph-based, used on many commercial vehicles,
especially buses with large windscreens. Pantograph wipers feature two arms for each blade,
with the blade assembly itself supported on a horizontal bar connecting the two arms. One of the
arms is attached to the motor, while the other is on an idle pivot. The pantograph mechanism,
while being more complex, allows the blade to cover more of the windscreen on each wipe.
However, it also usually requires the wiper to be "parked" in the middle of the windscreen,
where it may partially obstruct the driver's view when not in use.
A simple single-blade setup with a center pivot (Above Fig.) is commonly used on rear
windshields, as well as on the front of some cars. Mercedes-Benz pioneered a system (Fig.
below) called the "Monoblade", based on cantilevers, in which a single arm extends outward to
reach the top corners of the windscreen, and pulls in at the ends and middle of the stroke,
sweeping out a somewhat "M"-shaped path. This way, a single blade is able to cover more of the
windscreen, displacing any residual streaks away from the center of the windscreen.
10. Some larger cars in the late '70s and early '80s, especially LH Driver American cars, had a
pantograph wiper on the driver's side, with a conventional pivot on the passenger side.
Asymmetric wiper arrangements are usually configured to clear more windscreen area on the
driver's side, and so are mostly mirrored for left and right-hand-drive vehicles.
For example compare the following two figures.
One exception is found on Renault Clios and 2nd generation Twingos, where the wipers always
sweep towards the left. On right-hand-drive models, a linkage allows the right-hand wiper to
move outwards towards the corner of the windscreen and clear more area.
11. Some other types of windshield wipers are:
E. Windscreen washer
F. Hidden wipers
G. Rain-sensing wipers
H. Headlight wipers
I. Rear wipers
Bladeless alternatives:-
A common alternative design used on ships, called a clear view screen, avoids the use of
rubber wiper blades. A round portion of the windshield has two layers, the outer one of which is
spun at high speed to shed water.
US military wheeled vehicles,
jeepneys , some school buses and
utility vehicles, hummer
H1 and HUMVEE.
(Obsolete design, found on some older fire
Trucks and utility vehicles; same design on
Single windscreen for Jeep wrangler.)
12. 3. Procedure:-
Description:-
Be it snow or rain, mud or even debris, the windshield of a Mercedes Benz needs to be clear so
that the driver have the full visibility in avoiding the bumps, potholes, or even accidents waiting
to happen. It needs a device to wipe these eyesores not only to clean but to protect form harm, as
well. The windscreen wiper does this job. It cleans out unnecessary elements that pose as
distractions to the focused driving vision of a Merc owner. The assembly consists of: the arm
pivoting at one end, the motor that powers the assembly and the blade that attaches to the arm.
The blade is swung back and forth over the glass, pushing water and other elements from its
surface. Generally, the speed is being controlled with several continuous speeds and often one or
more "intermittent" settings. Most automobiles use two synchronized radial type arms, while
many commercial vehicles use one or more pantograph arms. The Mercedes wiper blades work
like squeegees as the arms drag a thin rubber strip across the windshield to sweep out water.
With a new set of Mercedes wiper blades, it is efficient as it leaves no sign of leftover with every
swing across the windshield. But time will wear it off, with nicks and cracks and road grime
building on its edge that doesn't make a tight seal. This leaves room for streaks. You can get an
extra mileage by wiping the edge with a cloth soaked in window cleaner until no more dirt
comes off the blade. Another key to streak-free operation is even pressure over the length of the
rubber blades. Wiper blades are designed to attach in a single point in the middle, but a series of
arms branch out from the middle like a tree, so the blade is actually connected in six to eight
places. If ice or snow forms on these arms, it can make the distribution of pressure uneven,
causing streaks under part of the blade. Some wiper manufacturers make a special winter blade
with a rubber boot covering the arm assembly to keep snow and ice out. But if the damage is
already severe, have Mercedes wiper blades replaced through auto parts stores and dealerships
around. Or log online to auto parts sites for a quicker and more comprehensive hunt for that
custom-fit wiper blade for the Mercedes. By considering all the above facts, we decided to
sketch the normal wiper and then we thought to attach the other links, in order to get the motion
of Mercedes Benz Initially we have designed the project in “Mechdesigner”.
13. Assumptions:-
To obtain the required motion we have initially planned to design 4 bar mechanism. After we
have designed the 4 bar mechanism we have observed the following.
We planned on starting with the cam at the bottom and then a link2 and link3. When we have
designed this 4 bar mechanism we observed that it rotates about 900 approximately. But we need
a motion which is more than that, so we thought to move for a better idea other than this. In fact,
it is very difficult to get a 4bar mechanism to rotate on output link by 1600. It will quickly jam
with only a little wear. We gave a second thought and we have planned for a 6 bar mechanism.
Our design for 6 bar mechanism is as follows:
14. Modeling techniques
To the previous 4 bar mechanism we have extended the link to the right and to that extended link
we have attached another link. The new design is as above. When we have designed that we
observed that the mechanism has a motion about 1600. So we have concluded that this 6 bar
mechanism will serve our purpose. So further, we have planned to extend this 6 bar mechanism
by making a link of wiper. Once we have attached the wiper, we observed that the design we
have done is perfectly suitable for a normal wiper which rotates about 1600.
From the above figure we can clearly observe that the wiper traces a simple arc. So now in order
to obtain the Mercedes Benz wiper mechanism we does not need the arc but more to this, and
also the problem with the above is as follows
15. As said earlier, the wiper only traces simple arc, and it leaves the important part of the wind
shield wet. In the above figure, we can clearly observe that the wiper leaves the 2 most important
paths at the end of the glass. It is important in the driver’s side of the glass to get wiped. So the
new Mercedes solves this problem and also we need a w shape. Now, the motion needs to extract
and retract as it rotates across the wind shield. The wiper must extend to the corners, and then
retract to avoid extending beyond the top and sides. The problem statement is as in the following
figure.
So for the extended and retraction motion we should have a mechanism which covers the area of
the shield as follows.
16. By moving the blade in and out as it rotates, the wiper now covers most of the screen.
17. So we have planned for a simple crank mechanism for obtaining the final motion. The crank
slider is as follows
In the above figure we can observe the simple crank mechanism attached to the previously
design of the wiper. In the above figure, wiper is the slider. And also, we have observed that the
crank rotates about 4 X faster than the wiper to give the desired wiper motion. Now, the crank
must rotate twice while the wiper blade rotates almost half.
18. We have kept the same design in ADAMS 2012, and the results are as follows:-
As we do not have the dimensions we went on trial and error initially, but later we were
able to find out the path of the wiper.
We almost had 35-40 trials and finally we were able to trace path.
We are including some of our trials. They are as follows:
Trial 1:-
In the above design, we followed the same procedure as we did in the mech design, we
started with the cam followed by the driver and the output link.
And we have attached the wiper to the out link and we have 6 bar mechanism as shown in
the above figure.
And we have 7 revolute joints.
And we have given the motion to the cam at the bottom.
Initially we gave 100 rpm, but we have observed that it does not give the no of rotations that
we require for the required wiper motion.
And also due to some unknown reasons the 1600 required motion by wiper is unable to
achieve.
In the next few trials we tried to decrease the CAM length and increase the driver.
19. Simulation result is as above.
That was the total end motion that we have got in our 1st trial.
Trial 2:-
We have made fewchangestoour earlierdesign,andthe changeswere makeable andthe design
outputwas almostas required.
We have changedthe initial positionandthe revolutejointsandthe linkare as same as previous.
Andthe outputis almostas desired.
20. The output for the trial 2 is as above and we have got the required motion.
Now we are able to obtain the normal wiper mechanism and since we have able to get the
required motion, now in our next trial we have tried for our Mercedes Benz motion.
22. To our earlier wiper design we have attached a link to the wiper of almost the equal length of the
wiper.
But the new wiper attached is set at a certain distance to the previous wiper joint.
Alsoto our newwipermechanismwe needthe newly attached wiper to slide to and fro, in order to
get the extraction retraction of the wiper which is very important for the wind shield wiper
mechanism of Mercedes Benz.
Nowto the newwiperwe have attached2 links and one link at the end of previous wiper and other
one to the end of new wiper.
Also, to the new wiper we have given a translate motion.
Also, we have changed the cam motion that we have given earlier.
The new motion we have kept suited perfectly and it is about 250RPM.
We have obtainedthe requiredmotionwhichissliding,andalsoitextendsinitially and retracts later
as per the required motion.
Bow, the result sets are as follows.
23. 4. Results:-
The above graph shows the power consumption of motion 1.
Motor and the motion required is given to the CAM.
From the above we can clearly state that during extension the consumption is more and
during the retraction it is less.
Also, we can state that retraction motion is very much like the quick worth return
mechanism.
24. Positiondiagramforthe CAMisas above.
It showsinX, Y, and magnitude.
The resultsare of wave form,almostlike asine andcosine form.
It isof sinusoidal function.
y = a sin (b x + c),
Velocitydiagramforthe CAMis as above.
It showsinX, Y, and magnitude.
The resultsare of a quadraticequationform.
25. Angularaccelerationof CAMinz directionandmagnitude.
Positiondiagramforwiperwhichhave the translatormotion.
The above diagramshowsin x,y,zdirection.
26. We have observedthe kineticenergyof the wiper,inordertoknow the energyobservedforthe
system.
Andis alsousedto observe the amountof workdone.
Delta potential is a potential well mathematically described by the Dirac delta
function - generalized.
Qualitatively, it corresponds to a potential which is zero everywhere, except at a single
point, where it takes an infinite value.
This can be used to simulate situations where a particle is free to move in two regions of
space with a barrier between the two regions.
For example, an electron can move almost freely in a conducting material, but if two
conducting surfaces are put close together, the interface between them acts as a
barrier for the electron that can be approximated by a delta potential.
The delta potential well is a limiting case of the finite potential well, which is
obtained if one maintains the product of the width of the well and the potential
constant while decreasing the well's width and increasing the potential.
27. Path of the Point:-
Path of the pointof wiper,the above graphshowsthe pathof the pointof wiper.
There we can clearlysee the extractionandretractionpathof the wiper.
Path of pointforCAM, we can see the pathfollowedbythe cam, we have giventhe motion
to our cam and itrotates 3600
aroundthe path withan RPMof approximately250.
There we can see the circular motion.
28. The above figuresshowsthe resultsets i.e. the pathfollowedbythose parts.
Everypart followsawave path.
These are givenI the x directionvstime.
29. The above graph showsthe velocityof the driverof the wiper.
Velocityhasraise andfall.
Raise andfall isdue tothe extractionandretractionof the motion.
It goespositive whenthere isextensionof the wiper.
Andit goesto the negative side whenitretracts.
Graph for the part whichmovestoand fro.
The linkalsohas the translatorjoint.
Andthere isthe effectclearlyvisible inthe graph.
30. Graph showsfor the positionof driveragainstx,ydirectionandmagnitude.
The graph is like asine curve withnegative andpositive values.
Belowgraphshowsthe angularvelocity
31. The above showsthe displacementformsandthe velocityforcesinx andy directionof the
CAM.
The belowshowsthe same,butforthe driver.
32. Graph’s showthe reactionforce at the revolute jointof Camandthe driver.
Belowgraphshowsthe reactionforce of translate jointof the wiper.
33. Applications:-
1. It is an existing model on Mercedes Benz.
2. It can be used for all the vehicles like car, truck etc.
3. It can be used more effectively with the help of gears.
4. It can be used in all weather’s with a proper blade or rubber for the wiper.
Limitations:-
1. In heavy rains it may cause certain distraction to the driver as it plays in front of the
driver for a while because it needs to reach the corner, so it causes certain detraction.
2. The existing model has lots of complaints regarding the blades, so definitely there are
limitations for the blades.
3. In heavy snow times the wiper get stuck and no motion is achieved (from the web
resources).
5. Conclusions and recommendations:-
Windshield wiper is exceptionally fascinating point and it's incredible to outline for such an
extraordinary component. However in the event that we begin with no measurement it will be a
major issue in settling the configuration. The Cam length and the driver length assumes a
noteworthy part in the starting 6 bar system. Once an ordinary wiper instrument is accomplished
you need to work for the complete 1600 unrest of wiper, which again will be an errand.
Additionally the movement to be given is essential, we have offered that to the Cam as when
given on others we didn't get the fancied results and we need to deal with diverse movements.
We have utilized the make an interpretation of joint to the connection on the wiper and we are
effectively in later stages, yet at first we confronted issue in picking up the position of single arm
furthermore revolute joints assume a noteworthy part in the configuration. A disgraceful area of
revolute joint prompts no snippet of the slider and though no revolute joint leads in dropping of
the connections.
Effective motion can likewise be acquired by executing different thoughts. We might want to
work in future and we would attempt the sliding movement with the assistance of apparatuses.
Riggings give much smooth minute when contrasted with decipher joint. Generally worm gear
must fill the need. So we wish to work and enhance this task in future.