Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Vehicle subsystem or accessory control
Reexamination Certificate
1998-04-23
2002-01-08
Louis-Jacques, Jacques H. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Vehicle subsystem or accessory control
C701S039000, C280S005500, C280S005504, C280S005505, C280S005514
Reexamination Certificate
active
06338014
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is generally directed to vehicle suspension systems, and in particular, to a control method for controlling vehicle suspension systems. The present invention is described with respect to suspension systems developed by the applicant. It is however to be appreciated that the control method is also applicable for other vehicle suspension systems.
2. Description of the Background Art
The Applicant has developed a suspension system disclosed in Australian Patent Application No. 23664/92, details of which are incorporated herein by reference. This suspension system incorporates double acting rams for each vehicle wheel. The upper and lower chambers of each front wheel ram is respectively interconnected with the lower and upper chambers of the diagonally opposite rear wheel ram to provide a fluid circuit thereof. A corresponding fluid circuit is provided with the other front wheel ram and rear wheel ram. The two fluid circuits are interconnected by a load distribution unit which is arranged to maintain at least substantially equal pressure in the two fluid circuits.
In the Applicant's International Application No. PCT/AU94/00646, there is disclosed a control arrangement for the above described suspension system incorporating a control arrangement for maintaining the vehicle in a position at least substantially parallel to the plane of the ground upon which the vehicle is traversing, details of which are also incorporated herein by reference. The control arrangement includes sensor means adapted for generating a signal indicative of the extension of each wheel ram, and therefore the position of each of the wheels relative to the vehicle body. The control arrangement then determines the average height of the vehicle body at selected locations between respective pairs of orthogonally adjacent wheels. Adjustment means are provided to adjust the quantity of fluid in the fluid circuits communicating with the rams of the said orthogonally adjacent wheels to establish the preset datum height between the orthogonally adjacent wheels and the vehicle body at the said selected locations.
The wheel rams are described as being adjusted in orthogonal pairs to avoid disturbing the position of the load distribution unit as the fluid quantity in each circuit is adjusted in the above application. However, because of the interconnection between the wheel rams, adjustment of the average height between one orthogonal wheel pair can produce a change in the average height between other orthogonal wheel pairs which can result in the overshooting of the average height between the other orthogonal wheel pairs past the desired height. The control arrangement must therefore adjust the average height between each of the orthogonal wheel pairs over a number of steps in an iterative process to progressively minimise this height error until the required average height is reached between each pair. This means that the fluid must be pumped and released from each of the fluid circuits over a number of steps to bring the vehicle body to a position parallel to the plane of the ground.
The primary problem of such an iterative process is that a large amount of fluid must be cycled to and from the circuits with fluid being pumped into and removed from each fluid circuit over a number of cycles until the vehicle reaches it is final position. Therefore, much energy and time is wasted in this iterative process.
It is therefore advantageous to have a control method which allows for faster adjustment of the vehicle body position.
SUMMARY OF THE INVENTION
With this in mind, the present invention provides a method of controlling a vehicle suspension system for a vehicle body supported by a plurality of spaced apart support means arranged in at least generally diagonally opposite pairs, the vehicle suspension system.including adjustment means for adjusting the position of each of the support means relative to the vehicle body, sensor means adapted to generate a signal indicative of the position of each of the support means, and control means arranged to receive said signals, the method including determining the position of each support means, determining a diagonal average for each pair of diagonally opposite support means, the diagonal average being the average of the position of one support means and the position of the diagonally opposite support means, wherein the required position for each support means is a function of at least two said diagonal averages, the position of each support means being adjusted on the basis of the said at least two diagonal averages.
As the control method determines the required position of each wheel individually, this provides for a faster adjustment of the vehicle position.
The control method preferably includes determining the diagonal average of the front left and back right wheels of the vehicle, and the diagonal average of the front right and back left wheels of the vehicle. The control method may then determine the difference between the diagonal averages to provide the “total articulation” of the vehicle. The term “articulation” refers to the situation where the first pair of the diagonally opposite wheels moves together in a common direction and the position of the second pair of wheels remains unchanged or moves together in an opposing common direction to the first pair thereof such that there is relative displacement between each pair of diagonally opposite wheels. As well as providing an indication of the degree of articulation of the wheels of the vehicle, the determination of the total articulation of the vehicle also indicates the flatness of the terrain upon which the vehicle is supported. When the vehicle position is on a flat surface, then the respective diagonal averages would be the same showing that the vehicle is not in articulation. When the vehicle is resting on or travelling over an undulating surface, the respective diagonal averages can differ showing that the vehicle is in articulation.
A “height set point” may be selected, this height set point being the desired height of the vehicle. A single overall height set point may be selected. Alternatively, the height set point may consist of a front height set point and a back height set point to allow pitch attitude adjustment of the system. These height set points may be manually selected by the driver of the vehicle and/or may be automatically selected by the control means in dependence on predetermined conditions. The height set points of the vehicle may for example be adjusted as a function of the vehicle speed. The height set points may be lowered when the vehicle is above a predetermined speed. The vehicle will generally only be moving at high speeds when the vehicle is not in an off road location where a lower height set point is desired.
The control method may also take into account any difference in the roll stiffness between the front and back of a vehicle which will vary between different models of vehicles. The ratio of the roll stiffness of the front of the vehicle and the total roll stiffness of the vehicle is referred to as the “Roll Split” or “Roll Couple Distribution” of the vehicle which will be a constant value for that vehicle. When the roll stiffness of the front and rear of the vehicle is the same, the Roll Split constant would be 0.5.
The wheel positions may preferably be measured on the basis of a calibrated scale to take into account differences such as in the relative degree of extension between the front and rear wheels. Each wheel position may for example be measured on a scale between 0 and 1. A wheel position may be designated to be at 0 when the wheel is fully retracted, i.e at or near the bump stop, and may be designated to be at 1 when at or near full extension. The other wheels may be calibrated on the same scale taking into account possible different wheel travel positions. It is alternatively possible to measure the actual extension of the wheels for the determination.
The control method may therefore determi
Heslewood Ray
Heyring Christopher B.
Longman Michael
Kinetic Limited
Louis-Jacques Jacques H.
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