Bose electromagnetic suspension - design and principle of operation

Since the times of Michael Faraday and James Maxwell, who laid the foundations for the theory and practical application of the electromagnetic field, scientists and designers have been tirelessly expanding the boundaries of application of the phenomenon of magnetic induction and superconductivity. Levitation, holding an object in the air without any visible support, opens up truly boundless practical possibilities.

But the effect of dielectric floating in a magnetic field until the early 80s was of more academic interest than practical. In 1982, construction began on the first magnetic levitation train. The M-Bahn magnetic plane hovered above the road, held in the air by a powerful magnetic field and was capable of reaching a speed of 501 km/h.

Electromagnetic suspension device

It consists of two components:

• Elastic components. Their task is to absorb shock loads in the vertical plane and transmit them further to the damping elements.
• Guides. They serve to absorb longitudinal and lateral impacts.
• Shock absorbers. They are a kind of damper that smoothes out all shocks from the suspension. On conventional suspensions it can be assembled with an elastic spring (the so-called MacPherson strut).

What is the difference between electromagnetic suspension and conventional suspension? The main factor is the electric motor.

It can act as a damping and elastic element at the same time. In the case of a classic suspension, each element is responsible for its own function - the levers move the wheel in the vertical direction, the shock absorber dampens vibrations, and the spring maintains the necessary ground clearance and elasticity of the chassis. Instead of a shock absorber, the electromagnetic suspension has the same electric motor controlled by a microcontroller. This design of the device allows the car to provide a high level of controllability, stability and comfort.

Front suspension and rear suspension of modern cars

As you can see, the front suspension and rear suspension may differ on different cars. If we discard old cars, today in the automotive industry the following schemes are used for passenger cars:

• fully independent suspension of all wheels;
• independent suspension at the front and semi-independent at the rear;

Note that the second option is used for budget and middle-class cars. As for cars with independent suspension and independent suspensions themselves, they can also be represented by the following options:

• MacPherson suspension;
• double wishbone suspension;
• trailing arm suspension;
• multi-link suspension;
• independent torsion bar suspension.

As a rule, trailing arm suspension is used for the rear suspension of a car. Other types of suspensions can be installed on both the front and rear axles. At the same time, on passenger cars with independent suspension, MacPherson strut suspension is most often installed on the front axle, and a multi-link suspension is installed on the rear axle.

We also note that SUVs and luxury cars can have air suspension (air suspension with pneumatic elastic elements). There is also a hydropneumatic suspension, which is also considered a separate option.

We also recommend reading the article about what the markings of disks mean and the decoding of their designations. From this article you will learn what parameters are encrypted in the car rim markings, as well as what to look for when deciphering the car rim markings when choosing them.

One way or another, the design of air and hydropneumatic suspension is still based on the types of well-known suspensions discussed above. The difference lies only in individual nodes and in the design of a number of elastic elements.

Finally, we note that cars can also be equipped with active suspension or adaptive suspension. As a rule, this is a set of available solutions. This suspension implements automatic adjustment of shock absorber stiffness; it is often possible to change the ground clearance, etc.

As a result, the car “adjusts” to specific conditions, allowing it to provide the necessary suspension stiffness and stability for driving at high speeds, as well as maximum comfort on bad roads. The solutions are quite expensive and technically complex. For this reason, active and adaptive suspension is installed only on high-class cars.

How does it work?

The operating principle of the electromagnetic suspension is based on the dependence of the magnetic and electric fields (that is, the principle of electromagnetism is used). The entire system is controlled by an on-board computer, which reads readings from the wheels every second and sends a corresponding signal to each one. Damping properties are provided by a small motor, which is located on each of the wheels of the car.

Experts say that the electromagnetic suspension device is much simpler than the classic one. After all, there are no working fluids, extra silent blocks or springs. However, installing an electromagnetic suspension is an expensive proposition. After all, the idea was not fully implemented and was practiced only at test sites.

Advantages

Experts note a number of advantages of this suspension:

• Reliability. There are no unnecessary elements in the design - vibrations are damped by electromagnetic induction, without any springs or hydraulic shock absorbers.
• Safety. The Lexus LS, which was taken as a prototype, practically did not roll when cornering. Moreover, during heavy braking, the front airbags automatically leveled the body in a horizontal position. This eliminates the possibility of skidding and an emergency.
• Comfort. By using a smart computer, the machine could predict bumps in advance. Thus, the suspension travel was maximum, and the body remained in a horizontal position. The car did not sway in the pits and maintained its trajectory.
• Economical. At any time, the driver can switch the suspension to mechanical mode. Thus, when the electromagnet moves in reverse, electricity will be generated.

General information

What is the suspension in a car?
This is a kind of intermediate link between the body and its wheelbase. The chassis provides the connection between the axle and the frame, as well as with other components of the vehicle.

In the design of a car, the suspension plays a vital role, because it transmits torque from the wheelbase. As a result, the car elements transmit the required motion vector to the wheels.

As for the electromagnetic suspension, one of the characteristic features of its design, which distinguishes it from standard suspensions, is the fact that it may completely or partially lack torsion bars, springs and other attributes of a conventional chassis.

SKF

This suspension was developed in Sweden. It has a simple design and reliability. The system consists of two electromagnets. When the car is moving at speed, the control unit analyzes the readings from the wheel sensors and changes the fluidity of the damping component. This ensures a very smooth suspension ride. By the way, the SKF chassis also has springs in case the control unit stops sending signals to the electric motor. Also, coil springs help protect against body sagging when the car is parked for a long time.

Types of magnetic suspensions

Currently, there are three major world brands that produce magnetic suspensions:

• SKF;
• Delphi;
• Bose.

Let's look at each of them in more detail.

Magnetic suspension SKF

The electromagnetic suspension, created by a Swedish company, is presented in the form of a capsule. The capsule consists of two electromagnets. Based on data from all sensors collected by the on-board computer, the stiffness of the damping element is adjusted. This allows you to select the optimal vehicle driving mode.

SKF Magnetic Stand

The key task that was set before Swedish specialists when developing their version of the magnetic suspension was to achieve simplicity and reliability of the design.

In the event of a malfunction of the control system, the suspension continues to function due to the spring. The ability to switch from automatic to manual mode is the main advantage of the SKF suspension. In addition, the suspension device allows you to avoid the effect of sagging when parking the car for a long time.

Delphi suspension

Front and rear Delphi magnetic shock absorbers
In the Delphi version, the suspension is presented in the form of a monotube shock absorber filled with magnetic rheological fluid. The size of the magnetic particles in the composition does not exceed ten microns. A special coating added to the solution in a one to three ratio prevents particles from sticking together.

The shock absorber piston, controlled by an electronic unit, contains an electromagnet. When a control signal is applied, a magnetic field is formed and the particles take on an ordered structure. The viscosity of the liquid increases. The operating mode of the shock absorber changes - it becomes more rigid.

The main advantage of the suspension is its reaction speed, which does not exceed 1 m/s. In addition, if the control system malfunctions, the suspension will function using a hydraulic shock absorber. This ensures safety when driving.

Bose electromagnetic suspension

Magnetic suspension, developed by scientist Aram Bose (yes, the one who also produces premium music equipment), is one of the most popular and discussed. In his interpretation, the device is represented by a linear electric motor, which, depending on the mode of motion, works as an elastic or damping element.

A distinctive feature of this suspension is the speed of action due to the operation of the magnetic rod. The damping rod with permanent magnets installed on it performs reciprocating movements along the length of the stator winding located in the housing. The device smoothes out vibrations when driving on uneven sections of the road. This ensures increased driving efficiency.

Stands from Bose

The Bose suspension provides a wide range of different settings:

• during a bend, the driver can select the signal pattern of the on-board computer in such a way that the rear outer wheel will act as a reference wheel;
• When turning, the suspension will transfer the load to the front outer wheel.

This provides increased control over vehicle control, regardless of the type of road surface.

Another feature of the Bose suspension is the “electric generator” mode. When a car moves in a straight line, vibrations caused by road unevenness are converted into electrical energy. In this case, electricity is not dissipated in space, but is concentrated in batteries for further use.

Unfortunately, the full potential of the Bose suspension is not fully realized. The process is slowed down by software development.

"Delphi"

This chassis consists of monotube shock absorbers. Each of them is installed on its own wheel. The shock absorber is filled with a working substance with magnetic components and the electromagnet itself. The substance fills about 30 percent of the total volume of the shock absorber. Magnetic parts are up to 10 microns in size. To eliminate the risk of draining the magnetic substance, the design has a special coating. The piston head is an electromagnet. It is connected to the on-board computer, which sends signals after collecting data from the sensors.

How does the Delphi suspension work? The operating principle is based on the ordering of magnetic particles of matter. They line up in a certain order, due to which the viscosity of the entire liquid changes. This ensures the shock absorber moves when hitting a bump.

The main advantage of the Delphi suspension is its responsiveness. The system responds to a request from a computer 10 times faster than analogues with solenoid valves. Delphi is also characterized by low power consumption thanks to its 20-watt power. The suspension is universal and can be installed on different vehicle platforms. If the signal to the computer stops, the system will switch to hydraulic mode and work like a classic shock absorber.

Special shock absorbers

The highlight of the Mercedes-Benz S-Class is the unique ABC system

Active anti-roll bars “Dynamic Drive” practically prevent the BMW “seven” from rolling when cornering.

THE MAIN element of many adjustable suspensions is a special shock absorber, which, at the command of an electronic control system, can change its characteristics while the car is moving. Otherwise, such pendants are practically no different from ordinary ones. As a rule, adjustable shock absorbers have several fixed operating modes (for example, standard, sport and comfortable). They are selected by the driver using buttons in the car.

Moreover, adjustable shock absorbers are different. For example, the chassis of the Audi TT or Chevrolet Corvette ZR1 sports coupe uses Magnetic Ride technology. This shock absorber is filled with special oil with magnetic particles (the so-called magnetorheological fluid). In addition, an electromagnet is built into the piston. When the car is moving, the electronic control unit constantly receives information from various sensors about the operation of the suspension, wheel speed, and other parameters - and, depending on the mode selected by the driver, regulates the current in the electromagnet. A magnetic field is created around it, under the influence of which the particles in the oil line up in a certain order, increasing the viscosity of the liquid and, accordingly, the stiffness of the shock absorber. Thus, the suspension very quickly adapts to any road. Until recently, such shock absorbers could not boast of an affordable price, high reliability and stable operation, and therefore were quite rare. But, as current trends show, designers managed to solve these problems.

The adjustable shock absorbers of other systems are designed differently - “Four-C” (“Continuously Controlled Chassis Concept”), used on the Volvo S80; EDC (“Electronic Damper Control”), known from various BMW models, as well as PASM (“Porsche Active Suspension System”), which is equipped with many Porsche sports cars.

The stiffness of their shock absorbers is also regulated electronically, but it is controlled by a special solenoid valve, which shuts off the flow of oil from one shock absorber reservoir to another.

However, despite the fact that the control unit receives information from many sensors several hundred times a second and changes the chassis settings in accordance with their readings, the performance of such a system is almost an order of magnitude lower than that of a suspension with “magnetic” dampers. In addition, the stiffness of the shock absorber in such systems does not change smoothly, but in steps. In other words, the efficiency of such a chassis is not so high, so although it is widespread on modern cars, it is becoming increasingly rare.

By the way, BMW on its models, in addition to adjustable EDC shock absorbers, uses “Dynamic Drive” active anti-roll bars to combat body roll in corners. In the middle they have a powerful hydraulic motor built into them, which does not work during straight-line movement, and the stabilizer does not interfere with the operation of the suspension. The electronics determines the start of a turn based on the signal from the lateral acceleration sensors and gives a command to the hydraulic motor. The sharper the turn, the more the hydraulics twist the halves of the stabilizer, preventing body roll.

"Bose"

Developed in 1980 by American professor Amar Bose. It was he who made the calculations and determined the best parameters for the innovative automobile suspension. The Bowes Corporation has become a leader in the development of electromagnetic suspensions. During testing, the system showed the best results, which cannot be compared with competitors. Thus, a linear electric motor could work not only as an elastic element, but also as a damping element. Permanent magnets are fixed to the rod. They produce reciprocating movements along the entire length of the stator. This not only allows you to gently absorb bumps, but also improves vehicle control. It was the Bowes suspension that could be programmed so that the corresponding wheel was engaged at the time the maneuver was performed.

Also, this chassis could work as an electric generator. Thus, while the car was moving over uneven surfaces, all vibrations were converted into electricity. It was collected in batteries and could be used for further operation of the suspension.

Among the disadvantages, it is worth noting the high complexity of the system. For its high-quality operation you need special software. It is still under development.

Advantages and disadvantages

Electromagnetic suspension is a completely new word in the automotive industry. That is why comparison with standard suspensions is, to say the least, incorrect.

If we talk about its advantages, then for the driver they are more than obvious:

1. The softness of the car's chassis.
2. The control is carried out using an on-board computer, which in itself is not new. However, many drivers note that the automated system is more responsive, which improves control.
3. There is also a definite advantage in saving energy consumption.
4. Multifunctionality - it can work automatically and then switch to mechanical mode. Such multitasking can significantly increase the reliability of the vehicle’s chassis, as well as driving safety in general.

On our website you can read about air suspension, which also has many advantages, one of which is the ability to adjust the ride height.

If we talk about the disadvantages of this type of suspension, we can name one - the availability of software to control this system. But progress does not stand still, and work in this direction is in full swing. Therefore, we can expect mass production of this suspension part in the near future.

This is interesting: How to improve car handling, tips from experts

I would also like to note the fairly high cost of such a chassis. It has not yet been put into mass production, but we can already name an approximate price tag - about 250,000 rubles. In principle, for this money you can buy a pretty good used foreign car, but no one said that modern suspension is intended for economy-class cars.

This is a fairly new technology in the automotive field that will be used in expensive cars, so such a high cost is quite justified.

We can already say that the appearance of electromagnetic suspension has become a new milestone in improving the driving characteristics of a car. This system is currently intended for the front suspension, but technical capabilities allow us to significantly expand the possible implementation of this system in a car device.

Other areas of the electromagnetic system are also developing. In particular, some models act as an electric generator, which allows you to convert all the bumps in the road into full-fledged energy. In other words, a car drives along the road, and every bump or pothole on this surface is a source of electrical energy.

This seems fantastic, but now we can safely say that the future has arrived today.

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Why is electromagnetic suspension not widely used?

Many motorists want to install such a system on their car. But the problem is that the development has not been fully studied. Over the years of work, it was never possible to bring this suspension to life and launch large-scale mass production. Many people talk about high costs, which would significantly affect the overall pricing policy. Perhaps in the future such a system will still be practiced on cars.

After all, the Bose electromagnetic suspension and its analogues provide the best ride comfort when using induction force. There are no complex levers or silent blocks that need to be constantly changed and their condition monitored.

Design and types of car suspension.

A car suspension is a set of parts that provide an elastic connection between the body (frame) and the wheels of the car, reducing dynamic loads on the body and wheels, and damping their vibrations, as well as adjusting the position of the car body while driving. The suspension, being an intermediate link between the car body and the road, must be light and, along with high comfort, ensure maximum traffic safety and smoothness. This requires precise wheel kinematics, highly informative steering, as well as sound insulation of the body from hard rolling tires. In addition, it must be taken into account that the suspension transmits to the body the forces that arise when the wheel contacts the road, so it must be strong and reliable. The hinges used should be easy to turn and provide sound insulation of the body. The elastic elements (spring and shock absorber) must be simple and compact, and allow sufficient suspension travel.

The main requirements for the suspension are the following:

• the elastic characteristics of the suspension should ensure a high smooth ride and no impacts on the travel limiters, counteract roll when turning, “nods” (trim) when braking and accelerating the car;
• the kinematic diagram should create conditions for possible small changes in the track and wheel alignment angles, matching the kinematics of the wheels with the kinematics of the steering drive, eliminating vibrations of the steered wheels around the turning axis;
• optimal damping of vibrations of the body and wheels;
• reliable transmission of longitudinal and transverse forces and moments from the wheels to the body or frame;
• low weight of suspension elements and especially unsprung parts;
• sufficient strength and durability of suspension parts and especially elastic elements, which are among the most loaded parts of the suspension.

Now let's briefly look at suspension designs. In general, there are quite a lot of suspension options; they are classified by the type of guide vane (dependent and independent) and by the type of elastic elements (spring, torsion bar, spring, pneumatic, etc.) Each suspension has its own disadvantages and advantages. The dependent one (VAZ-2101) is simpler, cheaper, has a constant track, but at the same time the bridge beam has large unsprung masses, so this suspension cannot be called light. In addition, when the left and right wheels of the same axle move in opposite directions, their significant tilt is observed, which results in resonant vibrations of the wheels in the transverse plane (shimmy effect) - the car begins to shake or, as they say now, “sausage.” Independent suspension has many more advantages, which is why it is more common now. Its variants differ in the location of the wheel swing plane: longitudinal, transverse, diagonal on oblique arms. And by the number of levers: single-lever, multi-lever (almost all Japanese cars), spark plug. It is also necessary to separate the so-called into a separate class. semi-independent suspension. Its more correct name: suspension with a twisting beam (VAZ-2108).

The suspension can be dependent or independent.

Scheme of operation of the dependent wheel suspension of a car

Dependent suspension is an option in which the wheels of one car axle are connected to each other by a rigid beam. When one of the wheels hits an obstacle, the other one tilts at the same angle.

Scheme of operation of an independent car wheel suspension

Independent suspension is an option in which the wheels of one axle of the car are not rigidly connected to each other. When hitting an obstacle, one of the wheels can change its position without changing the position of the second wheel.

Let's take a closer look at the types of car front suspension.

MacPherson suspension , named after the engineer Earl MacPherson, who developed it in 1960, is a wheel suspension consisting of a single link, an anti-roll bar and a unit of spring element and telescopic shock absorber, called a swaying plug, due to the fact that it It is fixed in the upper part to the body using an elastic hinge and can swing when the wheel moves up and down. Kinematically, the design is less perfect than a suspension on two transverse or trailing arms. With a large suspension stroke, the camber (the angle of inclination of the wheel to the vertical plane) changes, and the greater the suspension stroke, since the end of the lever moves up and down in a circle and, as a result, the track width changes. But due to its manufacturability and low cost, this type of suspension has become very widespread in the modern automotive industry. The MacPherson type suspension was first used in 1965 on the Peugeot 204, a year later on Ford, and in 1969 on the Fiat 128. Real widespread use began in the early 70s. Almost all modern front-wheel drive cars are equipped with such a suspension. Due to some of its advantages, McPherson has won a place for itself in rear-wheel drive cars. Low manufacturing costs, small occupied space (a correspondingly large engine compartment and, as a result, the ability to accommodate a large engine), a significant height distance between the support units, which determines the occurrence of smaller forces at the points of connection to the body, the possibility of making large strokes , are perhaps the main advantages and the reason that most large-scale cars appearing in recent years have this type of suspension on the front axle. Its disadvantages include: slightly worse kinematic parameters than the double wishbone suspension, great difficulties associated with ensuring isolation from road noise and vibrations (to combat this, subframes with rubber cushions appeared), unfavorably long steering rods with an upper rack and pinion steering mechanism, less trim compensation (longitudinal roll) when braking.

Double wishbone suspension. In this design, there are two wishbones with rotating supports (silent blocks) on the frame, beam or body. The outer ends of the arms, in the case of the front suspension, are connected using ball joints to the steering knuckle. The greater the distance between the transverse arms, the less force acting in the arms and their supports, i.e., the less compliance of all parts and the more precise the suspension kinematics. It should also be noted that the upper arms can easily absorb the hard rolling of radial tires (which is only possible with this independent suspension design). Although the longitudinal forces caused by rolling resistance are only slightly less on the upper arm, the lower arm and its supports are designed to withstand clearly larger loads. The latter arise under the influence of lateral forces or during braking. The main advantage of a double wishbone suspension is its kinematic properties: the relative position of the levers can determine the height of both the roll center and the center of trim (longitudinal roll). In addition, due to the different lengths of the upper and lower arms, it is possible to influence the angular movements of the wheels during rebound and compression strokes, i.e., change the camber and, regardless of this, change the track. With shorter upper arms relative to the lower ones, the wheels tilt towards negative camber during the compression stroke, and towards positive camber during the rebound stroke. In this way, changes in camber caused by body roll can be counteracted. Also, by changing the angle of the swing plane of the upper lever relative to the lower one, you can achieve an anti-tilt effect.

Multi-link suspensions. Multi-link suspensions are somewhat reminiscent of the previous type and have all its positive qualities. These suspensions are more complex and more expensive than those previously discussed, but provide a smoother ride and better vehicle handling. A large number of elements - silent blocks and ball joints - absorb shocks well when hitting obstacles sharply. All elements are mounted on the subframe through powerful silent blocks, which increases the noise insulation of the car from the wheels. Since this type of suspension became too bulky, the arms began to be made of aluminum alloys, which ensures one of the most important requirements - lightness. But at the same time, the durability of the parts immediately suffered. Such suspensions are now used on cars such as Audi, VW, Mercedes, Honda Accord, etc., that is, on business class cars. The use of multi-link independent suspension, which is mainly used on luxury cars, gives the suspension stable contact of the wheels with any surface on the road and precise control of the vehicle when changing direction. Gas two-way shock absorbers, lateral stability links, the use of two springs of different stiffness in one strut - all this creates a level of comfort in the car. Therefore, for the manufacture of elements of multi-link suspensions, expensive aluminum alloys, and sometimes even composite materials, are increasingly being used. The main disadvantage of the modern scheme is complexity and, accordingly, price. Until recently, it was used only on expensive cars. Now it “holds” the rear wheels of even some golf cars. In search of the eternal compromise between controllability and comfort, many copies have been broken. And if you look at the evolution of suspensions at least over the last couple of decades, it is obvious that development is not even progressing, but jumping. But this medal also has a flip side. Controllability and comfort, unknown to our ancestors, are paid for by the complexity and cost of structures. Are modern suspensions with complex architecture and sophisticated electronic additives so much better and more expensive than simpler and more common (for now!) circuits? Perhaps both engineers and marketers should ask this question more often.

Torsion bar suspension. Many modern SUVs use this type of suspension. Again, this is essentially a suspension on two wishbones, but instead of a spring, it uses a torsion bar - an elastic metal rod that works to twist. It plays the same role as springs, springs or rubber blocks. But unlike them, it only works on twisting (the French word torsion means twisting). This type of suspension became known as a rod suspension (aka torsion bar!). Engineer Ferdinand Porsche Sr. filed several patents for rod suspension in the late 20s and early 30s. He used it in 1934 on Auto-Union racing cars, and in 1940 it was already installed on Volkswagen production vehicles, both military and civilian. In 1935, the rod wheel suspension in its optimal version found widespread use on the Citroen Traction Avant. Porsche saw in the torsion bar its main advantage - compactness, and hence low weight. These qualities are especially valuable for vehicles with a very dense layout and strict weight restrictions - racing cars, SUVs, army wheeled vehicles. Examples of this are Ferrari F2001, Toyota Landcruiser, MAZ 547 rocket carrier. Andre Lefebvre, creator of Citroen TA, saw another advantage in the torsion bar. Its rod is quite long, the longer, the softer the suspension, and therefore. One end of the torsion bar, running along the car, is attached to the suspension arm, and the other is fixed in one of the cross members of the frame or supporting body. Thus, all loads from road shocks are transferred to the strongest point of the car, and they are distributed over the frame or body in the most advantageous way. For the first mass model with a monocoque body, this was important. Due to the widespread use of MacPherson-type front wheel suspension, fewer and fewer companies began to use torsion bar suspension. One of the reasons for abandoning torsion bars was the delicate manufacturing technology. However, for all-wheel drive SUVs with a frame and minibuses, the torsion bar suspension turned out to be ideal. On Toyota Prado, Isuzu Trooper, Ford Expedition, Chevrolet Blazer and others, long longitudinal torsion bars are used, attached to the axis of the lower, and on VW T4, the upper arm of the front suspension and tied at the other end to the frame cross member.

1. Suspension arm 2. Hydraulic cylinder piston 3. Hydraulic cylinder body 4. “Sphere” 5. LHM oil 6. Compressed nitrogen Schematic diagram of hydropneumatic suspension

Hydropneumatic suspension. The first suspension with variable ground clearance for a passenger car was created by the French company Citroen. The elastic element in the shock absorbers was compressed nitrogen, and the force element (forming and transmitting pressure in the system) was liquid. Therefore, this suspension is called hydropneumatic. The hydraulic pump forces fluid from the reservoir into spheres fixed next to the shock absorber. Inside each sphere, liquid and gas are separated by a membrane. Thus, the required pressure is maintained in the shock absorbers, and the roll of the car is constantly compensated. In addition, a valve built into the hydraulic system allows you to regulate the amount of fluid circulating in the circuits, and therefore increase or decrease the ground clearance. In 1954, this scheme was first used on the top-of-the-line Citroen 15-6. And already in October 1955, the new Citroen DS caused a real sensation at the 42nd Paris Motor Show. At that time it was a miracle machine. Its hydropneumatic suspension ensured constant ground clearance regardless of the number of passengers and luggage and a stunningly smooth ride. This car could tilt forward and backward, and even hang out any wheel without a jack! And finally, the driver of the Citroen DS could, at his own discretion, stepwise change the ground clearance. This not only increased the stability and active safety of the car on the highway (the center of gravity was lowered, the air flow under the bottom, which creates lift, was reduced), but also made it easier to drive off-road, which is important for France, which is full of country roads. Subsequently, this suspension scheme was used on most Citroen cars and was constantly being improved. The company's latest development, the Hydroactive III suspension, is electronically controlled using sensors, a computer and actuators. As a result, the ground clearance of the Citroen C5 model is not only maintained, but also automatically adjusted depending on the speed, quality of the road surface and driving style. The range of changes in ground clearance reaches 20-30 cm. Citroen made hydropneumatic suspension its strong point, using it before others. However, the English British Leyland Motor Corp. once installed a similar Hydrolastic suspension on its small cars. , and Lotus developed hydropneumatics for the Scorpion reconnaissance tank. Our airborne combat vehicle (BMD) with hydropneumatic independent suspension for all rollers has been produced by the Volgograd Tractor Plant since 1968. The car had to lie on its belly in order to better hide in the area and make it easier to load onto the plane. Many companies have been studying the possibilities of using purely air suspension in passenger cars. For example, in the 60s, Daimler-Benz (Mercedes Benz 600 and Lincoln equipped production models with it. And the first SUV equipped with wheel suspension on air bags that replaced springs was the Range Rover LSE in 1992. Much research in this area was carried out in 70s Volkswagen and Audi together with the company Fichtel und Sachs.

Now let's look at some types of car rear suspension.

Pendant "De Dion". The de Dion rear suspension, invented over a hundred years ago, is still used today. One of the disadvantages of the dependent suspension of the drive wheels is the large unsprung mass, which negatively affects indicators such as vehicle comfort, its stability and controllability. In cases where, for financial or design reasons, engineers refuse independent suspension, the old de Dion system comes to the rescue. In it, the main gear housing is fixed to the frame cross member or to the body, and the wheels are driven by axle shafts on hinges. In this case, the wheels are connected by a curved beam. The suspension remains dependent, but by mounting the massive final drive separately from the axle, the unsprung mass is significantly reduced. The list of cars using the de Dion type rear drive axle is quite extensive, and it includes not only such well-known models as the 1975 Volvo 345 and the 1985 Alfa Romeo 75, but also 2000 models: Aston Martin V8 Vantage, Honda HR- V 4x4 and a number of others. The pendant got its name from Count Albert de Dion, Marquis le Val. In 1883, the De Dion enterprise appeared. Bouton. Trepardoux. The Count played the role of a financier, Button a technologist and assembler, and Trepard represented the design bureau in a single person. On March 20, 1893, the de Dion rear axle was patented. Neither the count, nor Bouton, nor Trepard had any idea about unsprung masses; their intuition pushed them to create this unit. The fact is that in the first designs of De Dion-Buton tricycles and quadricycles, the engine was mounted on the rear axle. And driving on cobblestone streets shook the engine so much that parts literally fell off while driving. They decided to protect the knot from shaking and a bridge appeared, or, as they say today, a de Dion-type suspension. In an effort to rid the dependent rear axle of excess weight, engineers constantly improved the design. Now such a suspension can be either dependent or independent! For example, in the Mercedes R-Class, engineers combined the advantages of different schemes - the main gear housing was mounted on a subframe, wheels suspended on five levers drive swinging axle shafts, and pneumatic struts play the role of elastic elements - an original compilation!

Dependent suspension. From the very beginning of the automotive industry, dependent suspension has survived to this day. But it is becoming history - axles that rigidly connect the wheels are now used only on classic SUVs such as Nissan Patrol, Jeep or UAZ. Even less common on passenger cars, for example, Volgas and classic Zhigulis, but these cars were developed about half a century ago. The disadvantages of the design are obvious - the movement of one wheel is transferred to the other, resulting in resonant vibrations of the wheels in the transverse plane (shimmy effect), which harms both comfort and controllability. There is only one way out - you need to “untie” the right and left sides.

Hydropneumatic suspension. The rear hydropneumatic suspension is similar to the front.

Dubonnet pendant. A very original variety of independent schemes is the Dubonnet suspension. The suspension arm is attached to the wheel on one side, and the other goes into an oil-filled cylinder, which is nicknamed the “pig” for its unusual shape. There is a spring inside, into the cup of which the lever rests. By the way, oil not only lubricates the lever bearings, but also serves as a shock-absorbing fluid. Thus, the “piglet” is both an elastic and shock-absorbing element. But the Dubonnet suspension, which was very difficult to manufacture and repair, was used only in the 1930s of the last century on some American models, Opel Kadett, and from him it was inherited on the Moskvich 400.

Multi-link suspension. In the early 1980s, Mercedes Benz engineers began to use five separate levers instead of a pair of double ones. Two of them hold the wheel, and three more give it the required position in the horizontal and vertical planes. The multi-link design, compared to the simpler one with double wishbones, is a boon for the layout of components and assemblies. In addition, by playing with the size and shape of the levers, you can set the required suspension characteristics much more accurately. And thanks to the so-called elastokinematics, the suspension has a steering effect when cornering. This is what, for example, Ford Focus and Mazda 3 do. Intricate architecture, a large number of levers and hinges increase the weight of the structure. The rear multi-link suspension of the Ford Focus is very compact. And its thruster effect is a serious contribution to safety...

The active multi-link suspension was developed by Continental. The place of one of the BMW rear suspension arms was taken by an electric motor with traction (red arrow). At the command of the computer, it turns the wheel a little, essentially making the rear axle steerable. It is assumed that the new product (in a couple of years they promise to install it on production cars) will work with a stabilization system and active steering. It's hard to imagine what else will be automated in a car...

Usually, when assessing a car’s suspension, attention is paid to such consumer properties as comfort, controllability and stability (for some the first is more important, for others the second). Most people absolutely don’t care what type of suspension is on their cars, how many levers there are, and even more so, it doesn’t matter which axis the body’s roll center is located along. And it is right. This is the lot of engineers - choosing the type of suspension, selecting its geometric parameters and technical characteristics of its individual elements. During development, the car goes through a huge number of calculations, tests and tests. Therefore, in principle, the suspension of a standard car has acceptable consumer characteristics and meets the requirements of most consumers. It is no secret that comfort and controllability are properties that are often directly opposite, and depend on the stiffness of the suspension (a constant problem with our 8s and 9s - the suspensions hold the road well - they are as stiff as stools). These qualities can only be combined in complex, automatically adjustable suspensions of expensive cars. Many drivers who prefer an active driving style understand that the suspension of a standard, middle-class car cannot realize all their ambitions. And then the “struggle” for controllability begins. To the best of their means and strength, everyone follows their own path. First of all, most people start with shock absorbers, believing standard products to be the culprits of all their troubles, replacing them, for example, with gas ones. Some people install additional or stiffer anti-roll bars and front strut extensions. Some people replace rubber bushings and silent blocks in the suspension with stiffer ones (in common parlance - sports ones). Naturally, not forgetting about the springs, they are selected, trimmed, etc. All this bears fruit. Each specific case is different. Of course it all works, it’s hard to argue with that. But the combination of certain elements sometimes leads to “fatal” results.

Despite all this, many do not fully understand “what they are doing.” Many motorists install spacers on the front (killing the CV joints) and on the rear pillars, as a result of which it is impossible to set the wheel alignment angles (especially the longitudinal inclination - Caster). For example, not everyone knows that you can lower a car and practically not lose the energy intensity of the suspension, even if its rigidity is acceptable. Springs with progressive characteristics (different pitches of coils) can help us here. It is important to remember that the most important parameter when choosing springs is the combination of angular stiffness of the front and rear suspensions. Most standard cars are set to understeer for safety reasons. Neutral handling is considered ideal, but its disadvantage is that a car running at the limit of tire traction can present even an experienced driver with an unpleasant surprise in the form of an unexpected fall of the front or rear wheels. In other words, there is no unambiguity in controllability.