How the lift assist system works
Content
Heavy city traffic and mountainous terrain require extreme vigilance on the part of the driver, especially on slopes. While experienced motorists should get away with ease, rolling back on a hill is a common cause of accidents. The solution to the problem was the lift assist system, which should provide insurance for beginners and lost vigilance drivers.
What is the lift assist system
Modern car manufacturers direct their maximum efforts to create safe transport by introducing various active safety systems into the design. One of them is the lift assist system. Its essence is to prevent the car from rolling down when the driver releases the brake pedal on an incline.
The main known solution is Hill-Start Assist Control (HAC or HSA). It maintains the pressure in the brake circuits after the driver has removed his foot from the pedal. This allows you to extend the life of the brake pads and secure the start on the rise.
The work of the system is reduced to the automatic determination of inclines and the use of the braking system. The driver no longer needs to apply the handbrake or worry about additional safety when driving uphill.
The main purpose and functions
The main purpose is to prevent the vehicle from rolling back on a slope after starting to move. Inexperienced drivers may forget to ride when going uphill, causing the car to roll downward, possibly causing an accident. If we talk about the functional features of HAC, it is worth highlighting the following:
- Determination of the angle of inclination of the car - if the indicator is more than 5%, the system starts to work automatically.
- Brake control - if the car stops and then starts moving, the system maintains pressure in the brakes to ensure a safe start.
- Engine RPM Control - When the torque reaches the desired level, the brakes release and the vehicle starts moving.
The system does an excellent job in normal conditions, and also helps the car on ice and off-road conditions. An additional advantage is the prevention of rolling back under gravity or on a steep slope.
Design features
No additional structural elements are required to integrate the solution into the vehicle. The operability is ensured by software and written logic of actions of the ABS or ESP unit. There are also no external differences in the car with HAS.
The lift assist function must function properly even when the vehicle is reversing upward.
Principle and logic of work
The system automatically determines the slope angle. If it exceeds 5%, an automatic algorithm of actions is launched. This works in such a way that after releasing the brake pedal, HAS maintains pressure in the system and prevents rollback. There are four main stages of work:
- the driver presses the pedal and builds up pressure in the system;
- holding pressure using commands from the electronics;
- gradual weakening of the brake pads;
- complete release of pressure and the beginning of movement.
The practical implementation of the system is similar to the operation of the ABS system. You can read more about this in our article. When the driver presses the brake pedal, the pressure builds up in the brake system and the wheel brakes are applied. The system locks the slope and automatically closes the intake and exhaust valves in the ABS valve body. Thus, the pressure in the brake circuits is maintained and if the driver takes his foot off the brake pedal, the car will remain stationary.
Depending on the manufacturer, the holding time of the vehicle on an incline may be limited (about 2 seconds).
When the driver presses the gas pedal, the system gradually begins to open the exhaust valves in the valve body. The pressure starts to decrease, but still helps prevent rolling down. When the engine reaches the correct torque, the valves open fully, the pressure is released, and the pads are completely released.
Similar developments from different manufacturers
Most of the world's companies are concerned about introducing new products into vehicles and increasing driving comfort. For this, all developments designed for the safety and convenience of drivers are taken into service. The pioneer in the creation of HAC was Toyota, which showed the world the possibility of starting on a slope without additional action. After that, the system began to appear at other manufacturers.
| HAC, Hill-Start Assist Control | Toyota |
| HHC, Hill Hold Control | Volkswagen |
| Hill Holder | fiat subaru |
| USS, Uphill Start Support | Nissan |
Although the systems have different names and the logic of work may differ slightly, the essence of the solution boils down to one thing. The use of lift assistance allows you to increase the speed of the vehicle without unnecessary action, without fear of the threat of a rollback.
