Boots – shoes – and leggings
Patent
1991-02-06
1996-05-14
Park, Collin W.
Boots, shoes, and leggings
180 791, 180140, 280 91, B62D 714, B62D 504
Patent
active
055174132
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention is directed to an active rear axle kinematics disclosed by German published application 36 24 457 and in corresponding U.S. Pat. No. 4,785,065 for a motor vehicle also steered at the rear wheels thereof, whereby the rear wheel steering angle or angles are set by an electronically controlled actuator according to rated values for the rear wheel steering angle or angles or, respectively, rated values which can be derived therefrom whereby these rated values, or respectively, the rear wheel steering angles are calculated at least from which can be derived therefrom,
2. Description of the Related Art
In the known rear axle kinematics, a differential equation is solved with a process computer for calculating the rear axle steering angle. Such digital equations can usually be solved by iterative methods on the basis of digital, i.e., non-analog methods. The problem thereby derives that the solution is solved with adequate precision only after a plurality of iteration steps--this plurality being still unknown at the beginning of the calculation. In situations wherein one must react quickly, this means that the computer no longer finds a result in time or, respectively, that one must count on imprecise solutions dependent on how many iteration steps were capable of being carried out.
In an automobile, this can lead to problems precisely in dangerous situations when abrupt steering is carried out. The iterative solution of a differential equation also requires a relatively high memory requirement for the process computer.
SUMMARY OF THE INVENTION
The object of the invention is as well as as a result hereof, to also be able to reduce the memory requirement of this process computer. This object is achieved by the a digital filter is provided for the purpose of determining the rated values for the rear axle steering angle or angles, the digital filter being dimensioned according to a difference equation, whereby the difference equation, in turn, corresponds to a differential equation for the steering kinematics while satisfying Shannon's sampling theorem.
Insofar as a process computer hitherto thereby works according to an iterative method, it can be reprogrammed such, as shall be shown later, with the z-transformation of the invention that it subsequently works only according to difference equations that correspond to the differential equations.
Fundamentally, the originally given differential equation can nonetheless be complicated, for example--as is often standard in differential equations--can also contain terms of a higher order and many parameters, for example in order to further improve the control ease or the reliability in extreme situations. The result can nonetheless be very quickly and precisely calculated with the invention. Thus, for example, the respective steering angle of the rear axle or, respectively, rear wheels can also be co-considered. Likewise, a complicated dependency--for example, speed dependency--of the as--steering factor and of the two constants, for example, the derivative action time constant and the delay time constant can be co-considered.
BRIEF DESCRIPTION OF THE DRAWINGS
The new functioning of the process computer becomes easier to understand when the mathematical foundations are discussed in conjunction with drawings, including:
FIG. 1 is a flow diagram showing a process of sampling time calculations according to the present invention; and
FIG. 2 is a flow diagram showing a process of initialization according to the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
With reference to FIG. 1, the process computer, for example, has the job of driving the actuator for the rear axle according to the following algorithm, i.e. according to a differential equation, on the basis of the position of the steering angle, of the steering angle speed and of the vehicle speed (see FIG. 1, the second block): (t)+TD.multidot..delta..sub.v (t)) block) whereby ".delta." shall be referred to below as "delta", ".de
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Park Collin W.
Siemens Aktiengesellschaft
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