Automobile stability control system

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Automobile stability control system [Copy link]

One of the most obvious trends in the automotive industry is that car manufacturers are constantly using new software systems to link the hardware systems of the car to create new features. With these recent cars, it can be said that even if a child racer is driving a car with a high-performance suspension system, he will still stand out from other competitors driving ordinary cars.
ABS Functionality
Suspension system performance can be improved by using information from the anti-lock braking system (ABS). As we know, the ABS system can measure the wheel speed and control the wheel cylinder pressure of each wheel independently. However, some necessary improvements to this basic system can make the electronically controlled suspension work more effectively.
The first generation of ABS wheel speed sensors consisted of magnets, coils, gears and a gear ring. This VR type (variable reluctance) sensor works by opening and closing the magnetic circuit caused by the gear teeth. The opening and closing of the magnetic circuit causes the magnetic eddy current to change and generate a pulsating voltage in the sensor coil. Due to the use of multiple tooth shapes and electronic waveform signals, the output of the sensor is a series of pulses. The number of pulses generated by the sensor per unit time divided by the number of pulses generated per wheel revolution gives the wheel speed.
A serious drawback of VR wheel speed sensors is that the voltage of their output pulses is directly related to the speed at which the tooth profile passes through the magnetic circuit, and therefore the wheel speed is also directly related to the speed at which the tooth profile passes through the magnetic circuit. More and more so-called "active" ABS sensors now use Hall elements or magnetic field-limited sensors that are powered by the vehicle's electrical system. The biggest advantage of active sensors is that they can provide accurate wheel speed signals even when the wheel speed is zero.
The control system software can determine the reason why the speed of one wheel may be different from that of the other wheels. For example, a severely underinflated wheel will have a smaller diameter than other properly inflated wheels. In this case, the control software can compare the speed signals of the four wheels without the system applying the brakes and easily determine the wheel that produces more pulses per revolution than the other three wheels. This strategy can also be used to identify wheels that have a tendency to lock under braking conditions.
Among the various forms of active ABS sensors, Continental-Teves has developed a sensor that is installed in the wheel bearing. The seal of this bearing is electromagnetically marked and can be used as a rotating pulse generator in addition to its normal sealing function. The sensor itself is clamped into the bearing and becomes part of the wheel bearing assembly, and the active sensor is much smaller than the VR sensor, so the sensor can be packaged as Continental-Teves does.
A newer system based on ABS is the traction control system (TCS). TCS detects when the vehicle's drive wheel is rotating faster than the other wheels and reduces the slip of the corresponding wheel by reducing the throttle opening (regardless of the driver's throttle movement) or selectively applying braking force to the drive wheel. Applying brakes to one drive wheel can transfer the vehicle's driving torque to the wheel on the other side, which is very similar to the working principle of a limited-slip differential.
Not long ago, the Society of Automotive Engineers (SAE) invited some automotive engineers to test some of these systems. To verify the function of the TCS system, they laid a large plastic panel on the ground and sprinkled it with water and detergent. When tested with a car without TCS, when the driver stepped on the accelerator pedal, the engine made a common roar and the high-speed sliding wheel also made a piercing scream.
There is no engine roar or tire squeal when the TCS is used. The computer detects the slipping wheel and sends information to the engine power management system, which reduces the engine power output, and then the ABS system kicks in to apply braking force to the drive wheels. Then both wheels are well attached and the car drives off the plastic panel. Of course, once the car is off the plastic panel, it will rocket forward, and the driver must take his foot off the accelerator in time.
To ensure the stability of the suspension system, more sensors and other components are needed than the TCS system. For example, sensors are needed to detect the forces that affect the driver's ability to maintain the correct driving lane. Such devices include sensors that detect the vehicle's yaw condition. The so-called yaw is this: Imagine that you put a pin through the top of a toy car in the middle. When you push the front or rear end of the toy car, it will rotate around the pin. Perhaps the term understeer/oversteer monitoring sensor is more appropriate. If your vehicle loses control and the rear of the vehicle skids, the yaw sensor will be the first to detect it.
Two other sensors are also required. One is the steering angle sensor, which is mounted on the steering column and consists of a coil that detects the direction the driver wants to steer the car. The other is the lateral acceleration sensor, which measures the force that pushes the vehicle in the wrong direction of driving.
The active part of the system includes a component called the active brake booster. This device has a solenoid valve that enables the computer to control the brakes to produce the appropriate braking force. The ABS system determines which wheel to apply the required braking force.
How Continental ESP Works
Continental-Teves developed the Electronic Stability Program (ESP) based on its Mk 20 ABS system. ESP can recognize critical driving situations such as panicked driver reactions and maintain vehicle stability by applying brakes to individual wheels and intervening in the engine control system. The software combines signals such as the desired steering angle, yaw angle, lateral force and wheel speed differences to quickly determine when the car loses control. Then, regardless of the driver's actions, whether braking or accelerating, ESP kicks in to stabilize the car.
When the system is in operation, the ABS and TCS control the slip of the wheels under braking and acceleration, so that both the front and rear of the car remain stable. The yaw control portion of the system then stabilizes the car relative to a vertical axis (like the pins on the toy car in the previous example). This process is done independently of the driver's actions by applying brake control to individual wheels or controlling the engine's instantaneous output torque.
To demonstrate the effectiveness of the ESP system, the Society of Automotive Engineers set up a series of traffic piers in the parking lot of the Pontiac Silverdome (home of the Detroit Lions football team) to form a test track. If you've ever raced a Solo II or slalom, you know how interesting the course is. The speeds are not that high, but there are a lot of tight turns, and if you accelerate the car too fast, you will wear out a lot of tires. To ensure that nothing unexpected happens, an instructor from the Skip Barber Racing School sits in the passenger seat and participates in the test.
After I had driven four or five laps in an expensive BMW, my instructor suggested that the lane there was very good for acceleration and asked if I would like to try it again. When I said yes, he reached over and turned off the ESP system. I had no idea it was on!
This time I drove about a third of the way around the track when my car skidded badly and crashed three times in the parking lot. Fortunately, the car was not damaged except for some serious scratches and wear on all four tires. What surprised me most was how well the ESP system worked for the entire race after it was installed on the car, and how it saved me from serious trouble, and I had no idea it was working during the initial drive. What surprised me the most was that they had me do this driving test in a $70,000 BMW!
There are many ESP systems available. You can be sure that as the cost of computers and software products decreases, the price of these systems will also decrease.
When you look at these stability control systems, they don't look much different than other parts, which is the cleverness of the car service providers. And it is even more important to note that although you have to pay close attention to the number of parts when you have your car serviced, because these systems vary by manufacturer, model and year, you can only point out that the change in software in a functional module or assembly may only be a difference in the number of parts. However, the car's diagnostic system will help you determine what is wrong and ensure that you replace the parts correctly so that the system can operate normally.