ELECTRONIC LEVEL CONTROL SYSTEMS
An Electronic Level Control System (ELCS) uses suspension dampers equipped with external inflatable air bags to control the height of the corners of the vehicle. The dampers may be either passive or controlled, and may be either struts or shock absorbers. A motor-driven air compressor provides high-pressure air to inflate the air bags, which act to elevate the height of that particular corner. When the air is let out in a controlled deflation, the vehicle returns to the desired trim height. Sensors are used to measure and compare the actual height of the vehicle to the desired height. The sensors send signals to an Electronic Control Unit (ECU), which automatically controls the activity of the air compressor and the inflation/deflation of the air bags.
ELCS has been used in the automotive industry for several decades. It is an adaptation and integration of basic technologies, which have been used for multiple purposes: “air lift” struts and shock absorbers, air compressors, height sensors and ECUs. What is innovative is the way in which an ELCS can be used to accomplish multiple objectives.
ELCS can be used to accomplish multiple objectives. Historically, the original purpose was to compensate for the significant mass conditions under which a passenger vehicle must operate. Varying numbers of passengers and varying loads of luggage and other carried objects can change the sprung mass of the vehicle significantly. If there is only a driver, a conventional vehicle trim height (i.e., without ECLS) would tend to have the rear of the vehicle in a high position. If the vehicle is fully loaded with the maximum number of passengers and carried objects, the rear will be low compared to an ideal trim height. That adversely affects the vehicle’s ride & handling characteristics. An ELCS can adjust to the desired trim height regardless of the load. A second benefit is that headlamp aiming, which is subject to regulatory approval in many countries, is made much easier because an ELCS keeps the vehicle at the desired trim height. A third benefit, which is emerging as perhaps the most important, is the improvement in fuel economy which ELCS can provide. An ELCS can be used to automatically lower the front of a vehicle once it reaches a certain speed. When this capability is integrated with exterior vehicle design (e.g., air dams and design elements aimed at creating laminar underbody airflow) a noticeable improvement in fuel economy can be achieved. At lower speeds, the ELCS returns the front of the vehicle to a normal trim level.