The ESP system is based on sensing elements (sensors) and actuators of a conventional anti-lock brake system (ABS), as well as on the elements of the engine control system.
The main functions of the general system of exchange rate stability are as follows.
- Function of stabilization of the car on the trajectory of movement (ESP) is the highest priority in terms of impact on the car compared to other functions of the overall system. The ESP system ensures the stabilization of the vehicle on the trajectory when cornering and the stabilization of the rectilinear movement of the vehicle in the presence of course deviations.
- normal ABS function (Antitock Brake System), which is designed to prevent the wheels from locking during the braking process of the car. In this case, during braking, the speed sensors of all wheels measure and compare the intensity of wheel deceleration. The system weakens the braking force in that branch of the hydraulic brake system, which corresponds to the wheel with the most intense deceleration.
- ASR traction control function (Acceleration Slip Regulation) drives the drive wheels. If there is an accelerated rotation of one of the driving wheels during acceleration, the system brakes this wheel by applying precisely calculated pressure to the brake cylinder,
- Traction control function ETS (Electronic Traction System).
- Forced idle control function (engine braking) on the slippery road MSR (Engine Braking Regulation). Regulation is carried out by means of the engine management system (CDI) by reducing the braking torque transmitted from the engine to the drive wheels. This subsystem prevents the drive wheels from slipping when the accelerator pedal is released.
- EBV Electronic Brakeforce Distribution (Electronic brake force distribution). By performing this function, the system distributes the braking force between the front and rear wheels. The operation of the system is similar to that of ABS. At the same time, in EBV mode, the system reacts to changes in wheel speed earlier than in ABS mode. The need for such a function is dictated by the different intensity of deceleration of the front and rear wheels with insufficient vehicle loading.
- BAS emergency brake boost function (Brake Assist system). With intensive (sharp) pressing the brake pedal, which the system evaluates as the desire of the driver to brake as soon as possible, BAS increases the pressure in the brake cylinders (with simultaneous control of the braking process by the ABS system).
The principle of operation of the ESP system
Example A
Car understeer in a left turn.
In this case, the front wheels take out beyond the required trajectory to the outer side of the turn.
Correction of the trajectory is made by precisely calculated braking of the rear left wheel.
Example B
Vehicle oversteer in a left turn.
Pulling the rear wheels to the outside of the turn.
Correction of the trajectory is made by precisely calculated braking of the front right wheel.
Scheme for correcting the trajectory of the car when cornering:
a. Desired direction of travel
b. Wheel to which corrective braking force is applied
c. Torque applied to the vehicle as a result of corrective braking
d. Front wheel slip due to centrifugal force
e. Skidding of the rear wheels under the action of centrifugal force
Systems interaction
The ESP function is the highest priority function among those listed due to the fact that its action is the most universal. This is expressed in the fact that in order to stabilize the car on the trajectory, the system in ESP mode uses sensors and actuators of all the listed systems (ABS, ASR, MSR and EBV).
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