Absolute value transmitter acting as a rotation transmitter...

Details Absolute value transmitter acting as a rotation transmitter... Absolute value transmitter acting as a rotation transmitter...

1999-10-20

2001-05-01

Cuchlinski, Jr., William A. (Department: 3661)

Data processing: generic control systems or specific application

Specific application, apparatus or process

Specific application of positional responsive control system

C700S254000, C700S255000, C700S275000, C700S260000, C700S261000, C341S002000, C341S013000, C341S015000, C318S587000, C701S024000, C701S224000

Reexamination Certificate

active

06226569

ABSTRACT:

The invention concerns a digital absolute value transmitter, specifically a rotation transmitter for registration of the steering angle of a motor vehicle.
Highly accurate registration of the steering angle gains ever growing importance in modern motor vehicles, whereby, for example the steering angle is needed in regard to active dynamic moving mechanisms for control or regulation of the moving gear state or moving gear behavior. In practically all instances, the highly accurate registration of the absolute value of the steering angle is needed. This, however, requires extremely accurate absolute value transmitters, with generally costly construction and correspondingly high expenditure.
Known digital absolute value transmitters (for example JP 4-1522 A) which are suitable as rotation transmitters for registration of the absolute rotation angle, have, as a rule, an encoding, which, by scanning each word, i.e. bits in one line, permits the determination of a value assigned to said word. It is, however, of disadvantage with respect to such digital absolute value transmitters that the words must have a relatively large width in order to ensure adequate resolution. In this context, a digital absolute position encoder or encoding method is known from DE 195 45 949 A1, in which the number of the required tracks for providing an absolute value transmitter is reduced by a single-step code; said benefit, however, is only obtained by utilization of several detectors per track. This means higher circuit-engineering expenditure.
That also applies with respect to absolute value transmitters which have only one single track, and which concurrently scan several bits of the track, whereby the digital words of a code are sequentially connected in the track (for example JP 08-122099 A; DE 40 22 503 C1; DE 195 18 664 C1).
The above specified absolute value transmitters permit immediate determination of absolute position in each position, but require high expenditure.
Relative value transmitters can be realized more simply and more cost-favorable, but in such case an initialization process is necessary before operating the system for calibration of the relative value transmitter. To that end, for example, the steering system or the steering wheel must be brought into a defined position, staring from which, a determination of the absolute values of the steering angle can be made via relative registration of the steering angle. Although it is, in fact, possible to also store the starting value (initialization value) for determination of the absolute value so that if the system loses tension, the value remains preserved, the problem rests in the fact that if the system is switched off, steering movements are no longer registered and, consequently, following activation of the system, an initialization process would have to be gone through.
In addition, absolute value transmitters are known which link incremental and absolute coding- or decoding methods (for example EP 0 530 176 A1; EP 0 545 701 A1). As a rule, one incremental code is used covering the entire to be registered range and one absolute code at one or several selection positions. The absolute positions are registered by means of a first detector as with conventional absolute value transmitters, whereby, however, only a small width for the digital words is required. Starting from the then known absolute position, it is then possible, by means of the incremental code, which is being scanned by another detector, to determine the respective absolute position when there is a relative movement of code and detector.
This type of absolute value transmitter also required a relatively high expenditure and can only register correctly the absolute position, after losing power, if the first absolute code had been reached. In motor vehicle technology this is not permissible for reasons of safety.
The invention is therefore based on the object to provide an absolute value transmitter, specifically a rotation transmitter for registration of the steering angle of a motor vehicle, which can be realized as simply as possible and cost-friendly and which ensures, at the same time, adequate operating safety, specifically after the system has lost power.
The invention solves this object with the characteristics of Patent claim
1
.
By the at least one-time determination of the absolute rotation angle by evaluation of a pre-determined number p of sequentially detected digital words (W
i
) there results the benefit of substantially lower required word width. For first-time determination of the absolute value, overtravel of p words is necessary, so that, to that end, the transmitter component must, initially, be moved by p-times the resolution. However, after first-time determination of the absolute value, the maximal resolution is then again reached, i.e. the absolute value can be exactly determined with each overtravel of a word (W
i
). All sequences (W
i
, W
i+1
, .W
i+p−1
) consisting of predetermined numbers (p) of sequential words (W
i
) of the encoding must be, to that end, uniquely defined, at least within a predetermined uniquely defined range of the encoding. Without complying with this requirement, a given p-measure cannot be assigned a defined absolute value. In contrast thereto, within each uniquely defined range, the digital words (W
i
) need not be uniquely defined.
In the preferred specific embodiment of the invention, at least one of the following conditions is complied with:
a) in each instance, two adjacent words, W
i
, W
i+1
have different values, i.e. W
i
is not equal to W
i+1
;
As a result of this, step recognition is made possible by the evaluation only of the signal generated by encoding, so that synchronized scanning can be relinquished;
b) the respective words W
i−1
and W
i+1
, adjacent to the word W
i
; have different values, in other words W
i−1
and W
i+1
are not equal; This permits recognition of change in the movement direction by evaluation of only the signal generated by the encoding; without said requirement it would not be possible, in case of a change in the direction of the movement, after prior registration of the words W
i−1
, W
i
, . . . , W
p−2,
W
p−1
to determine whether in case W
p−2
=W
p
the value W
p
was produced by a movement in the same direction or by a movement in the opposite direction; that applies at least if the evaluation unit realizes the p-measure in form of a first in—first out register, whereby each new word W
i
is always “inserted” in the register of the fixed length p from the same end and that, respectively, prior to the insertion, the last word is dropped, independent of whether prior to registration of said W
i
a change took place in the direction of movement.
c) no p-measure (W
i
, W
i+1, . . . ,
W
i+p−1
) may exist within at least one uniquely defined range of the encoding as mirror-image p-measure (W
i+p−1
, W
i+1
, W
i
) in other words (W
i
, W
i+1
, . . . , W
i+p−1
) is not equal to W
i+p−1−k
, . . . , W
i+1−k
, W
i−k
); Otherwise it could not be determined by evaluation alone from the signal generated by the encoding whether the respective p-measure was generated in overtravel from one or the other direction; Thus, recognition of the absolute movement direction is hereby facilitated.
This condition could only be dropped when in each instance recognition of the movement direction would be ensured by providing an additional device.
According to one specific embodiment of the invention, the evaluation unit can in each instance effect the determination of the absolute value by allocating the respective predetermined value to the actual p-measure.
The possibility, however, also exists, to effect said possibility of absolute value determination only once or at given intervals, or for certain reasons, and to determine future absolute values by incrementation or decrementation. Thus, only one evaluation is necessary for step recogniti

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