Testing cars for handling and stability. Directional stability, rearrangement, corner entry

In this article from the “Car Safety Systems” series we will talk about the ESP active safety system . ESP - Electronic Stability Program - dynamic stabilization system or exchange rate stability system. Just like the ABS series discussed in the previous article, the ESP system does not serve to eliminate an accident, but to prevent it.

However, unlike the same anti-lock brake system, the dynamic stabilization system is not yet very widespread, and it is not yet possible to find it on relatively inexpensive foreign and especially domestic passenger cars.

I believe that this is a matter of time, and in 5 years ESP will become a generally accepted standard, and cars without this system will simply not be produced.

Now is the time to move on to a detailed examination of the system, but first I want to give an example of a situation in which esp could help avoid an accident.

The nature of ESP operation - what functions are controlled by the system?

Most modern cars in their advanced trim levels have this active safety feature. If previously buyers were confused by the presence of many abbreviations of three Latin letters, today each name arouses genuine interest in the driver. We are talking about such important safety.

But in the case of the exchange rate stability system, not every driver knows the nature of the operation of this module. When ESP is included in a car, the question arises, what are they? So, the ESP module is responsible for controlling the vehicle’s control during a skid, controlling the following machine functions:

steering, or rather, the inadmissibility of sudden jerks by the steering wheel when skidding;
distribution of braking forces to each wheel to the required extent;
reducing or increasing engine speed to obtain the desired control;
monitoring angular velocity and lateral acceleration to understand the onset of skidding.

Sensors for this function are located on virtually all vehicle controls, which leads to a quick response to any skid. As soon as the car begins to leave the driver's control, the ESP system assists and begins distributing the correct braking forces, adjusting the steering and performing other functions. It is almost always possible to avoid an uncontrolled skid.

Don’t think that cars with an ESP system can be driven recklessly on slippery roads, because the module will save you in any situation. ESP is far from magic; it is a technology that will not help to overturn the laws of physics. So if you enter a skid at a speed of 90 kilometers per hour, you will not feel the effect of the function.

Can the ESP system interfere with the driver?

In fact, for experienced drivers who like to drive at the limit (although usually race track racers, there are exceptions), the stability control can be a hindrance. It can interfere in a situation where, in order to pull the car out of a skid, you need to give a lot of gas, but the electronic system simply does not allow this to be done; according to the program, it does not supply a lot of fuel and reduces the torque that is so needed at this moment. For such drivers, most modern cars have a button to disable the ESP system, although sometimes there is no button, sometimes you need to carry out a number of actions to turn it off. There is also ESP, which does not respond instantly, but with a slight delay, thereby allowing the driver to have a little fun on the road. Of course, if you are not a racer or a not very experienced driver, then it is better not to turn off the stability control system; safety on the road comes first, as you understand. With the ESP system, you can feel confident on the road, where you turn the steering wheel, the car goes there, although it will have to do a lot of things for this, but do not forget that this system is not magic and it is impossible to deceive the laws of physics, so there is no need take another risk. By watching the video below, you can see how a car behaves with the ESP system turned on and off:

Avtochanel

Operating principle of electronic stabilization

While the car is moving, the exchange rate stability system operates constantly, regardless of the mode - during acceleration, braking and driving at a constant speed. By collecting data from a group of sensors and other assisting systems, the controller compares the resulting picture with a reference one stored in its own memory. Having detected deviations that threaten the safety of the car and passengers, the electronic unit intervenes in the control and tries to correct the situation.

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The ESP operation algorithm should be shown using the example of a car lateral drift in a left turn:

The fact of skidding is detected by the angular acceleration sensor (G-sensor) and transmits information to the controller.
The ECU receives additional data from wheel rotation and steering wheel position sensors.
Based on the totality of the received signals, the electronic unit “understands” the speed of the lateral displacement and its direction. As a result, the solenoid valves of the valve body are given a command to brake the left rear wheel with a certain force.
At the same time, a signal is sent to the main controller of the car to reduce the supply of the combustible mixture to the cylinders in order to reduce the transmission of torque to the drive axle.
The result: regardless of the driver's actions, the car slows down and straightens out when turning.

When ESP interacts with other electronic "assistants", the vehicle's directional stability can be ensured by additional means - temporary blocking of the free differential (center and cross-axle), activation of the traction control system and precise distribution of braking forces. In a car equipped with an electronically controlled automatic transmission (robot, CVT), ESP can switch to a lower speed or enter winter mode.

Note. If problems with directional stability arise under the control of adaptive cruise control, the latter will act synchronously with the other systems - steering the front wheels in the desired direction.

In fact, the active stabilization system relieves the car enthusiast from the need to learn extreme driving. When entering a turn, the driver simply turns the steering wheel, entrusting the rest of the actions to the ESP. But it should be remembered that the possibilities of electronics are not limitless and not all emergency situations can be prevented.

Additional Interaction Tools

How ESP works in general has already been described in detail. However, in some cases, directional stability of a vehicle with ESP can also be achieved through other, additional means - blocking free differentials, precise distribution of braking force, and turning on the anti-slip function. Moreover, in cars with electronically controlled automatic transmissions, the dynamic stabilization system is capable of independently activating the winter driving mode or turning on a reduced speed.

Finally, if the problem of directional stability occurs on a car with adaptive cruise control, it must also act synchronously with other electronic assistants. In practice, this means that the cruise control steers the front wheels in a direction that helps straighten the car.

In fact, the driver of the ESP system in the car (what it is, how it works and what components it has is absolutely not necessary to know) provides the opportunity not to learn extreme driving. He simply turns the steering wheel when entering a turn or overtaking another car, and all other actions that prevent skidding are performed by the stability control system. And yet, the possibilities of this electronic assistant are far from limitless - both an experienced car owner and even more so a novice should remember this!

How the stability control system works

As a result of comparing the driver’s actions and vehicle movement parameters, the system determines the occurrence of an emergency situation. If the actual driving parameters differ from the standard ones, the ESP system considers the situation to be out of control and makes adjustments to the operation of the vehicle.

The stability control system can stabilize the vehicle's movement in the following ways:

braking of one or more wheels;
changing engine torque;
changing the angle of rotation of the front wheels (if the car has an active steering system
management);
changing the degree of damping of the shock absorbers (if adaptive suspension is installed)

In the event of understeer, ESP prevents the vehicle from drifting out of the corner by applying brakes to the inside rear wheel and altering engine torque.

In the event of oversteer, the system prevents the vehicle from skidding in a corner by braking the front outer wheel and changing engine torque.

To brake the wheels, the appropriate active safety systems are activated.

The ESP system changes engine torque in one of the following ways:

by changing the throttle position;
missed fuel injection;
skipping ignition pulses;
changing the ignition timing;
canceling the gear shift in the automatic transmission;
redistribution of torque between axles (if all-wheel drive is used).

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Such a system, which combines stability control, steering and suspension, is called an integrated vehicle dynamics control system.

Device and main components

The exchange rate stability system is a collection of simpler systems: ABS (prevents brake locking), EBD (distributes braking forces), EDS (electronically locks the differential), TCS (prevents wheel slip).

Components of the exchange rate stability system: 1 – hydraulic unit with ECU; 2 – wheel speed sensors; 3 – steering angle sensor; 4 – linear and angular acceleration sensor; 5 – electronic engine control unit

The dynamic stabilization system includes a set of sensors, an electronic control unit (ECU) and an actuator - a hydraulic unit.

Sensors monitor certain vehicle movement parameters and transmit them to the control unit. Using sensors, ESC evaluates the actions of the person behind the wheel, as well as the driving parameters of the car.

To evaluate the actions of a person behind the wheel, the stability control system uses brake pressure and steering angle sensors, as well as a brake light switch. Vehicle movement parameters are monitored by sensors of pressure in the brake system, wheel speed, angular velocity of the vehicle, longitudinal and lateral acceleration.

Based on the data received from the sensors, the control unit generates control signals for the actuators of the systems that are part of the ESC. Commands from the ECU receive:

How the ESP system works

The ESP system is constantly in operation when the car is started, regardless of what is happening: acceleration, deceleration or coasting. ESP is directly connected to the ABS anti-lock braking system, traction control and engine control unit; without them it simply cannot function. The ESP system has its own electronic unit; it constantly reads signals from a large number of different sensors and processes them, all the time - up to several dozen times per second, and this unit makes decisions at lightning speed, in less than a second. Additional data comes to the unit from sensors: ABS, steering wheel and pressure in the brake system. And the most necessary, most necessary and important information comes only from 2 special sensors: angular velocity relative to the vertical axis and lateral acceleration (usually called the G-sensor). These 2 main sensors monitor the lateral slip of the car on the vertical axis, then evaluate its significance and send a signal to the ESP electronic unit. The exchange rate stabilization system knows at any time what speed the car is, how many degrees the steering wheel is turned, what speed the engine is, whether it is skidding or not, in general, it controls the car completely.

When alarm signals come from sensors to the ESP control unit , it immediately compares the behavior of the car at the moment with its program, and if suddenly the data diverges, the electronic unit understands that this is an extreme situation and begins to correct it. To return the car to the correct trajectory, ESP begins to brake one or two, three, four wheels; the system determines which wheel or wheels need to be braked independently, depending on the current situation. The wheel braking itself occurs using the ABS hydraulic modulator, which builds up pressure in the brake system. The system can also reduce torque by supplying less fuel using the engine control unit. Let's consider the situation, let's say you are taking a turn at high speed and, as a result of the slippery road surface, the car begins to skid, what begins to happen at this moment? At this moment, a command is sent to the engine control unit that it is necessary to reduce the fuel supply to reduce the torque, said and done, the torque has been reduced, but it happens that this is not enough to stabilize the car, and this is where the wheels are braked using ABS . The principle of operation of the ESP system, as you can see, is quite simple and understandable. Also, if the car has an electronically controlled automatic transmission, the ESP system can shift gears down or even turn on the so-called “winter” mode, if, of course, the gearbox has one. The picture below shows how a car will behave on a slippery surface with and without the ESP system during a sudden detour of any obstacle on the road during a turn. In this situation, the obstacle was road work and you can say that this rarely happens, maybe this is true, but there are other similar situations, for example, a moose will run out onto the road or a car will suddenly drive out, so you need to be prepared for anything.

A situation in which ESP could have prevented an accident

So, I suggest you watch the video in which a car gets into a skid on a dry road and provokes an accident:

As you already understood when watching the video, the culprit of the accident is the car that got into a skid. Although in fact, almost all participants in the incident violate traffic rules.

The ESP system allows you to avoid precisely such skids, for example, those that occur when a wheel or several wheels of a car hit the side of the road.

Among the many new developments with mysterious names in the form of abbreviations, the ESP stability control system is of great importance and is one of the important additions to your car. With the help of many sensors and instant response to the start of a skid, this module will not allow the driver to lose control.

If you're wondering whether it's worth paying extra for this active safety feature, be sure to consider having it in your car. Such additions do not require additional costs, maintenance or other processes. They will only always serve for the benefit of your safety.

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How does the system work?

This abbreviation stands for Electronic Stability Program, which translated into Russian means “electronic stabilization system.” It should be noted that this function is not available for budget cars, but is installed optionally in cars of the mid-price category. Only expensive cars are equipped with ESP as standard, and later you will understand why.

The main element of the circuit is a separate electronic control unit (also known as a controller, ECU), which interacts with the following sensors:

front wheel rotation meter;
the same for the rear wheels;
steering wheel position detector;
dynamic lateral load sensor (another common name is G-sensor, angular acceleration meter).

Anyone who has ever understood the principle of operation of the anti-lock braking system (ABS) will probably see familiar parts in the list above - wheel rotation meters that transmit information to the ABS controller.

The ESP electronic unit also controls the hydraulic cylinder valves of the front and rear brakes, plus it is connected to the main “brains” of the car, which controls the supply of fuel to the engine cylinders. In a car with a similar set of electronics, a separate controller for the anti-lock braking system is simply not needed, since ABS is part of the ESP and receives commands from the main ECU.

To maintain directional stability of a passenger car, ESP must interact with other electronic driver “assistants”:

system that prevents slipping of the drive wheels (ASR);
automatic differential locking devices (EDS);
a system that distributes braking forces depending on driving conditions (EBD).

Reference. In premium cars, ESP is closely linked with another “assistant” - adaptive cruise control, which can completely control the car’s movement on the highway and in urban conditions.

It is not difficult to guess that in budget cars the above-mentioned electronic “stuffing” is absent, but in cars of the mid-price category, manufacturers install anti-lock wheels and a couple of other systems (depending on the brand and equipment of the vehicle). This is why ESP is not available for every new car.

ESP device

The main component of the system is the electronic unit (controller) of the ECU, which receives signals from the angular acceleration meter (G-sensor) and numerous sensors installed on all wheels and in the steering unit.

Experienced car owners will probably notice that this list contains components of the ABS system. This means that ESP is highly correlated with it. In addition, the ECU controls the valves of the brake hydraulic cylinders, and it interacts with the vehicle’s on-board computer, which controls the fuel supply. That is, the anti-lock braking system is part of the dynamic stabilization system, receives commands from the main ECU, and therefore does not need a separate controller - it is already in the ESP.

But that's not all. In any case, the vehicle's stability control system also interacts with other electronic assistants - ASR, EDS and EBD. We won’t go into their functionality, but just note that in premium-segment cars, the ESP system is closely connected with adaptive cruise control, which is responsible for driving not only on the highway, but also in the city.

Application

In Canada, the USA and the countries of the European Union, since 2011, stability control systems have been mandatory installed on all passenger cars. Note that system names vary depending on the manufacturer. The abbreviation ESC is used on Kia, Hyundai, Honda cars; ESP (Electronic Stability Program) - on many cars in Europe and the USA; VSC (Vehicle Stability Control) on Toyota cars; DSC (Dynamic Stability Control) system on Land Rover, BMW, Jaguar cars.

The dynamic stabilization system is an excellent assistant on the road, especially for inexperienced drivers. Do not forget that the possibilities of electronics are also not limitless. The system in many cases significantly reduces the likelihood of an accident, but the driver should never let down his guard.