Measuring and testing – Speed – velocity – or acceleration – Structural installation or mounting means
Patent
1994-07-25
1996-02-27
Raevis, R.
Measuring and testing
Speed, velocity, or acceleration
Structural installation or mounting means
G01P 326
Patent
active
054939089
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to sensors for sensing the position and/or the movements of a vehicle or a vehicle body.
In the last ten years or so, use has been made of so-called active suspension, which is a system radically improving the performance of the vehicle, especially its road-holding qualities, by altering the parameters controlling the movements of the vehicle suspension and represented by the stiffness of the suspension and the dampening effect produced by the dampers to reduce the risk of oscillations occurring in the suspension.
This suspension system has been rendered more sophisticated by the active supply of energy therein, e.g. in order to incline the vehicle for purposes of compensation in a "motorcycle-type fashion" in the bends. Similar ideas have been implemented for high-speed trains, where the carriage body is inclined inwards towards the center of a movement through a curve. Such inclination of the vehicle body substantially improves the road performance as well as the riding comfort of the driver and the passengers, manifesting itself not only as a potentiality of increased average cruising speed but also as a safer travelling function and improved braking properties of the vehicle.
From the theoretical, mathematical point of view, it has been held that the position of a vehicle is best determined with the aid of an inertial-navigation system with a so-called sky-hook, in which the position of the car in space can be determined. However, since such systems are extremely expensive as well as complicated to build, efforts have instead been made to measure the total movements of the car body to get an idea of the various movements that may arise, such as rocking, rolling, and vertical displacement of the center of gravity. When using this system, it is of extreme importance that these movements be determined with the utmost accuracy.
To this end, use is made of accelerometers, which are arranged at different points in the vehicle. In a simple acceleration system, the accelerometer is disposed at the center of mass of the vehicle. In more advanced systems, on the other hand, the accelerometers are disposed as peripherally as possible in the vehicle to give maximal deflection when the car body moves in certain patterns. In this context, the maximal forces of acceleration are in the order of 2 g. In terms of construction, it is not very difficult to build an accelerometer having a maximal output signal as early as 2 g. However, the demands of the car industry are much higher. Thus, they require that an accelerometer should be able to withstand a fall to a concrete floor from a height of 1 m. Accelerations of about 5000 g have been measured on such impacts, and it is regarded as difficult to build accelerometers withstanding an optional shock of 5000 g while maintaining their properties at .+-.2 g. Today's accelerometers are thus built with several protective casings, where the innermost casing encloses the accelerometer and its seals, and the outermost casing is made of, e.g. hard rubber or some other yielding material giving a certain deceleration distance, should the accelerometer be exposed to extreme shocks.
This problem is the more complicated as it is impossible to determine by visual inspection or a simple measuring operation whether an accelerometer has been damaged, e.g. during transport or when being mounted.
Another problem encountered in prior-art constructions concerns the positions of the accelerometers in the vehicle. Naturally, accelerometers can be arranged in, e.g. the luggage boot, but it is much more difficult to find a suitable place in the front of the vehicle. The engine compartment is regarded as one of the most difficult places for electrical equipment. This is so because one then has to take into consideration not only temperatures ranging up to 120.degree. C., but also the risk of chemical damage, e.g. from degreasing agents, oil, or water. In addition, the environment is extremely exacting also because of electrical conditions, since high voltages of up to 2
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Raevis R.
Solaris Nova Aktiebolag
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