Stability control

Luminous indicator

The stability control is a computerized technology used in the active safety of the car that acts by individually braking the wheels in risky situations to avoid skidding, both oversteer and understeer. Stability control centralizes the functions of the ABS, EBD and traction control systems.

Stability control was developed by Bosch in 1995 in cooperation with Mercedes-Benz and was introduced to the market in the Mercedes-Benz S-Class under the trade name Elektronisches Stabilitätsprogramm (German &# 34;Electronic Stability Program", abbreviated ESP). ESP is called by other names, depending on the vehicle manufacturers it is mounted on, such as Vehicle Dynamic Control ('VDC', VDC).), Dynamic Stability Control ("dynamic stability control", DSC), Electronic Stability Control (" electronic stability control", ESC) and Vehicle Stability Control ("vehicle stability control", VSC), although its operation is the same.

History

In 1983, an electronic " slip control " four-wheel drive in the Toyota Crown. In 1987, Mercedes-Benz, BMW, and Toyota introduced their first traction control systems. Traction control works by applying braking and throttle to individual wheels to maintain traction under acceleration, but unlike ESC, it's not designed to assist with steering.

In 1990, Mitsubishi launched the "Mitshubishi Diamante" in Japan. It featured a new electronically controlled active crawl and traction control system. Named TCL when it first entered the market, the system evolved into Mitsubishi's modern Active Skid and Traction Control (ASTC) system. Developed to assist the driver in maintaining the intended line around a corner; an on-board computer monitored various vehicle operating parameters through various sensors. When too much throttle. It had been used when cornering, engine power and braking were automatically regulated to ensure the correct line through a curve and provide the right amount of traction under various road surface conditions. While conventional traction control systems at the time only featured a slip control function, Mitsubishi's TCL system had an active safety function, which improved course setting performance by automatically adjusting the tractive force (called "trace control"), which restricted the development of lateral excesses. acceleration when turning Although not a 'proper' modern stability control system, the follow-through control monitors steering angle, throttle position, and individual wheel speeds, though there's no yaw. The standard wheel slip control feature of the TCL system allowed for better traction on slippery surfaces or during cornering. In addition to the individual effect of the system, it also worked in conjunction with the Diamante's electronically controlled suspension and four-wheel steering to improve overall handling and performance.

BMW, in collaboration with Bosch and Continental, developed a system to reduce engine torque to prevent loss of control and applied it to most of the BMW model line for 1992, excluding the E30 and E36. This system could be ordered with the winter package, which came with a limited-slip differential, heated seats, and heated mirrors. From 1987 to 1992, Mercedes-Benz and Bosch jointly developed a system called Elektronisches Stabilitätsprogramm ("Electronic Stability Program", trademark ESP) to control side slip.

Concept

The system consists of an electronic control unit, a hydraulic unit and a set of sensors:

• steering angle sensor: is located in the direction and provides constant information about the movement of the steering wheel, i.e. the direction desired by the driver.
• wheel turning speed sensor: they are the same as the ABS and report on the behavior of the same (if they are blocked, if they skate...)
• Turn angle and cross-sectional acceleration sensor: provides information on vehicle displacements around its vertical axis and lateral movements and forces, i.e., what is the actual behavior of the vehicle and if it is starting to drag and deviate from the trajectory desired by the driver.

ESP is always active. A microcomputer controls the signals coming from the ESP sensors and checks them 25 times per second to verify that the direction the driver wants through the steering wheel corresponds to the actual direction in which the vehicle is moving. If the vehicle moves in a different direction, the ESP detects the critical situation and reacts immediately, independent of the driver. Use the braking sistem of the car to stabilize it. With these selective interventions of the brakes, the ESP generates the desired counterforce so that the vehicle can react according to the driver's manoeuvres. ESP not only initiates brake intervention, it can also reduce engine torque to reduce vehicle speed. In this way the car remains safe and stable, always within the limits of physics.

Operation

During normal driving, the ESC continuously monitors the steering and steering of the vehicle. Compares the predicted direction of the driver (determined by the angle measured at the steering wheel) with the actual direction of the vehicle (determined through the measured lateral acceleration, the rotation of the vehicle and the individual speeds of the wheels on the road).

ESC intervenes only when it detects a probable loss of steering control, such as when the vehicle is not going where the driver is driving. This can happen, for example, when skidding during evasive emergency turns, understeering or oversteering during poorly calculated turns on slippery roads or hydroplaning. During performance driving, ESC may intervene when not desired, because steering input may not always be indicative of the intended direction of travel (such as during controlled drift). The ESC estimates the direction of the skid and then applies the brakes to individual wheels asymmetrically to create torque around the vehicle's vertical axis, opposing the skid and bringing the vehicle back into alignment with the direction commanded by the driver. Additionally, the system may reduce engine power or operate the transmission to slow the vehicle.

ESC can work on any surface, from dry pavement to icy lakes. It reacts to and corrects skids much faster and more effectively than the typical human driver, often before the driver is aware of any stalls check imminent. This has raised some concern that ESC could allow drivers to become overconfident in the handling of their vehicle and/or in their own driving abilities. For this reason, ESC systems generally alert the driver when they intervene, so that the driver is aware that the vehicle's handling limits have been reached. Most activate a dash indicator light and/or alert tone; some intentionally allow the vehicle's corrected heading to deviate very slightly from the direction commanded by the driver, even if it is possible to match it more accurately.

All ESC manufacturers emphasize that the system is not a performance enhancement or replacement for safe driving practices, but rather a safety technology to help the driver recover from dangerous situations. ESC doesn't increase traction, so it doesn't allow for faster cornering (although it can facilitate more controlled cornering). More generally, ESC works within the limits of the vehicle's handling and available traction between the tires and the road. A reckless maneuver can still exceed these limits, resulting in loss of control. For example, during hydroplaning, the wheels that ESC would use to correct a skid may lose contact with the road surface, reducing its effectiveness.

Due to the fact that stability control can be incompatible with performance driving, many vehicles have a control override that allows the system to be fully or partially disabled. On simple systems, a single button may disable all features, while more complicated setups may have a multi-position switch or may never be fully disabled.

Stability control and safety (active)

Numerous organizations related to road safety, such as euroNCAP, as well as automobile clubs such as RACC, RACE or CEA advise the purchase of cars equipped with stability control, since it helps to avoid accidents due to leaving the road, among others, and could reduce the mortality rate on the roads by more than 20%.

ESP® reduces the number of skid accidents. Global studies conducted by car manufacturers, insurance companies and transport ministries have shown that the ESP® system prevents up to 80% of skid accidents. This is also reflected in the respective accident graphs. When it comes to safety systems that save lives, ESP® is second only to seat belts.

In June 2009, the European Union passed legislation making the use of ESP® mandatory for all vehicles in categories N1, N2, N3 and M1, M2, M3: passenger cars, light commercial vehicles, buses and vehicles medium and heavy industrial as of November 2014.

Name of the stability control according to manufacturers

The stability control can have many additional functions:

• Hill Hold Control or slope promotion control: it is a system that prevents the vehicle from turning back when it resumes on a slope.
• "BSW", brake disc drying.
• "Overboost", pressure compensation when the brake fluid is overheated.
• "Trailer Sway Mitigation", improves stability when a trailer is carried, avoiding the "scissors" effect.
• Load Adaptive Control (LAC), which allows you to know the position and volume of the load in a light industrial vehicle. This function prevents a possible spin for the loss of stability. It is also called Adaptive ESP for the Mercedes vehicle range. It is standard in the Mercedes-Benz Vito and Sprinter and the Volkswagen Crafter.

Electronic stability control (ESC) is the generic term recognized by the Automotive Society and other authorities, although each company establishes its own name: