(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:

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.

Table of contents:-

1. Introductiona) Inside the Wipers

b) Motor and Gear Reductionc) Linkaged) Wiper bladese) Pivot points.

2. Backgrounda) Wipersb) Geometryc) Alternatives

3. ProcedureA. Description of the project.B. Assumptions.C. Modeling techniques.D. Method of solution.

4. Results and DiscussionA. Results.B. Discussion of precisely what the results mean.C. Applications.D. Limitations.

5. Conclusions and Recommendations

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. 

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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.

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.

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.

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 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.

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.

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.

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.)

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”.

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:

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

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.

By moving the blade in and out as it rotates, the wiper now covers most of the screen.

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.

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.

Simulation result is as above. That was the total end motion that we have got in our 1st trial.

Trial 2:-

We have made few changes to our earlier design, and the changes were makeable and the design output was almost as required.

We have changed the initial position and the revolute joints and the link are as same as previous. And the output is almost as desired.

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.

Trial3:-

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. Also to our new wiper mechanism we need the 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.

Now to the new wiper we have attached 2 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 obtained the required motion which is sliding, and also it extends initially and retracts later

as per the required motion. Bow, the result sets are as follows.

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.

Position diagram for the CAM is as above. It shows in X, Y, and magnitude. The results are of wave form, almost like a sine and cosine form. It is of sinusoidal function.

y = a sin (b x + c),

Velocity diagram for the CAM is as above. It shows in X, Y, and magnitude. The results are of a quadratic equation form.

Angular acceleration of CAM in z direction and magnitude.

Position diagram for wiper which have the translator motion. The above diagram shows in x,y,z direction.

We have observed the kinetic energy of the wiper, in order to know the energy observed for the system.

And is also used to observe the amount of work done.

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.

Path of the Point:-

Path of the point of wiper, the above graph shows the path of the point of wiper. There we can clearly see the extraction and retraction path of the wiper.

Path of point for CAM, we can see the path followed by the cam, we have given the motion to our cam and it rotates 3600 around the path with an RPM of approximately 250.

There we can see the circular motion.

The above figures shows the result sets i.e. the path followed by those parts. Every part follows a wave path. These are given I the x direction vs time.

The above graph shows the velocity of the driver of the wiper. Velocity has raise and fall. Raise and fall is due to the extraction and retraction of the motion. It goes positive when there is extension of the wiper. And it goes to the negative side when it retracts.

Graph for the part which moves to and fro. The link also has the translator joint. And there is the effect clearly visible in the graph.

Graph shows for the position of driver against x,y direction and magnitude. The graph is like a sine curve with negative and positive values. Below graph shows the angular velocity

The above shows the displacement forms and the velocity forces in x and y direction of the CAM.

The below shows the same, but for the driver.

Graph’s show the reaction force at the revolute joint of Cam and the driver. Below graph shows the reaction force of translate joint of the wiper.

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.

References:-

http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=6775395&url=http%3A%2F%2Fieeexplore.ieee.org%2Fiel7%2F6766337%2F6775377%2F06775395.pdf%3Farnumber%3D6775395http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=6775395&url=http%3A%2F%2Fieeexplore.ieee.org%2Fiel7%2F6766337%2F6775377%2F06775395.pdf%3Farnumber%3D6775395https://prezi.com/rx6forfhiwhr/windshield-wiper-mechanism/http://www.spannerhead.com/2012/11/28/technical-curiosities-mercedes-monoblade-wiper/