EP0779986A1

EP0779986A1 - Method of determining direction of movement, in particular rotational movement

Info

Publication number: EP0779986A1
Application number: EP96900583A
Authority: EP
Inventors: Joachim Mathes
Original assignee: ITT Automotive Europe GmbH; Alfred Teves GmbH
Current assignee: ITT Automotive Europe GmbH; Continental Teves AG and Co oHG
Priority date: 1995-01-19
Filing date: 1996-01-16
Publication date: 1997-06-25
Also published as: DE19501513A1; WO1996022538A1

Abstract

The invention concerns a method of determining direction of movement, in particular rotational movement of rotating parts such as a vehicle steering wheel. The object of the invention is to improve the accuracy of such a process using simple means. This is achieved by applying a method by which two directly measured signals and two other signals derived from the former of a first frequency are evaluated to derive at least two further signals (E, F; G, H) which are mutually phase shifted by 90° and have a frequency which is double the first frequency. In a further embodiment of the invention, a further signal (K, L) with a frequency four times that of the initial two signals (A, B) is derived from the two derived signals (E, F; G, H).

Description

Method for recognizing a direction of movement, in particular a direction of rotation

In the art, detection devices are often required, which are able to indicate the angle of rotation and the direction of rotation of an element performing a rotary movement. For example, it is important to recognize the steering angle forced by the rotary movement of a steering wheel if this is required for the operation of a power steering or a driving stability control.

In such detection devices, for example, the axis of the steering wheel can be provided with a slotted disc, which is illuminated by a transmitter directed at a receiver. The radiation to be measured can be, for example, magnetic radiation, optical radiation or another suitable radiation. In this case, preference is given to magnets which direct their field onto Hall sensors or else infrared transmit diodes which work together with corresponding receive diodes.

The aim is to achieve high measuring accuracy with the least possible material expenditure. On the one hand, it should be noted that, in addition to the emitted measuring radiation, interference radiation may also be present, which is particularly true when using infrared diodes with regard to the

ORIGINAL DOCUMENTS Vehicle cabin prevailing light is of great importance. At the same time, there is still a need to separate the changes in the measured light beam from the ambient lighting.

In order to achieve greater accuracy with regard to the illumination measurement, a larger number of transmitters and receivers can be used, on the one hand, or the measuring device is specially adjusted after assembly in the vehicle or at least after assembly of the measuring device.

From DE-OS 41 04 902 (internal file number A 13184) it is known instead of the phase relationship of the two

To compare radiation receivers directly with one another instead to compare the difference signal of these two receivers with the sum signal of these two receivers. In this application it was further demonstrated that the two last-mentioned signals have a phase angle of 90 ° to one another, regardless of the precise geometric position of the receivers, although considerable deviations in the amplitudes of these two signals can occur .

The present invention is therefore based on a method of the gate resulting from the preamble of claim 1. The object of the invention is to achieve a simple duplication of the frequency of the measured signals.

The object is achieved by the combination of features resulting from the characterizing part of claim 1. Due to the features specified there, it is at least possible or to generate two phase-shifted signals which have twice the frequency compared to the two measured signals (1st and 2nd signal) and which regularly have a phase shift of 90 ° to one another. In contrast, the phase shift from the first to the third and the second to the fourth signal is 45 ° in each case. If one further considers that the fifth and sixth signals (E, F and G, H) can be formed in phase reversed fashion, which can also happen according to the features listed in claim 1 in that the derived signal at If inequality has a positive value instead of equality, a total of four signals (E, F or G, H) can be derived, which have twice the frequency compared to the two measurement signals. If one wants to double the frequency again, then in a further development of the invention the combination of features according to claim 2 is recommended. Then the fifth and sixth signal (E, F or G, H; or their inversion) becomes a seventh signal K , L with a quadruple frequency compared to the measured signals A, B. Here too, the phase can be reversed by assigning the positive value of the seventh signal to the inequality instead of the equality of the fifth and sixth signals.

It is thus shown that, with little effort, for example, with a corresponding arrangement of gates, signals derived from the two measured signals can be formed at two or four times the frequency, which results in increased measuring accuracy when measuring the angle of rotation or the Angular velocity can be reached. An embodiment of the invention is explained below with reference to the drawing. It shows:

1 The formation of the rectangular curves on which the exemplary embodiment is based.

2 shows the formation of the measured signals and those derived from the measured signals.

Fig. 1 shows a measured sine signal S, which is provided with an off-set (OS) due to the ambient lighting. Of course, the measured signal does not necessarily have to be sinusoidal and can also have a sinusoidal or trapezoidal shape. The value MW measured over time T is thus composed of a threshold SW and a curve shape S placed thereon. The mean value ME forms the mean value of the measured value MW. By means of suitable trigger circuits, a rectangular curve RK can be formed, the edges of which lie laterally where the sinus curve S intersects the mean value MI. Instead of the curves S actually measured and shifted relative to their mean value, the derived rectangular curves RK are described for the sake of simplicity. However, the method can also be applied directly to the measured curves S, insofar as they are related to their mean value MW.

2 shows two rectangular curves A and B, which are offset by approximately 90 ° from one another, which are referred to below as first signal A and thus signal B. A third signal C and a fourth signal D are reached from the first signal and the second signal by forming signals A and B as well as by forming signals A and B as differences. The formation of these third and four- th signals is described in DE-OS 41 04 902.

It is now important for the invention to recognize that a fifth signal E and a sixth signal F can be derived from the two measured signals A and B but also from the two derived signals C and D. The procedure is to assign a fixed positive or negative amplitude value to the equality or inequality of these two signals. The fifth signal E is formed, for example, by always having a negative value when the first and second signals have the same (positive or negative) sign with respect to their mean value. If the signs are not equal, the signal E is assigned a positive value and if the two signals A and B are equal, the signal E is assigned a negative value.

Of course, the sign of the signal derived from both signals A and B can also be reversed by assigning a positive value to the same sign of the two derived signals A and B and a negative value to the opposite sign. The signal G is then reached. The signal F is formed from the two derived signals C and D in accordance with the rules applicable to E. The signal H forms a correspondence to the signal G.

As can be seen from FIG. 2, a seventh signal K can also be formed, which has twice the frequency compared to signals E or F or four times the frequency compared to signals A to D. The circuit for this is arranged, for example, such that if the signs of the signals E and F are equal, the sign of the signal of K is negative and if the signs of inequality are the signs of Signal from K is positive. Of course, one can also select the opposite sign with respect to this further derived seventh signal and thus come to the signal L.

Claims

claims

1. Method for recognizing a direction of movement, in particular a direction of rotation, using two signals which are phase-shifted by 90 ° (1st signal A, 2nd signal B), which are derived from two receivers arranged offset in the direction of movement of a signal source, two of them Further phase-shifted signals (third signal C, fourth signal D) are formed from the two phase-shifted signals (1st signal A, 2nd signal B) of the receiver by adding the two first signals together or subtracting them from one another are characterized in that a fifth and / or a sixth signal (E or F or G or H) which are phase-shifted from one another by approximately 90 ° and have twice the frequency compared to the first to fourth signals, are formed in that the first signal (A) with the second signal (B) or preferably the third signal (C) with the 4th signal (D) for inequality (or equality) with respect to an average t is compared, the derived fifth or sixth signal (E, G or F, H) in the event of inequality (or Equality) assumes a positive value in relation to its mean value and in the case of equality (or inequality) assumes a negative value in relation to its mean value.

2. The method according to claim 1, characterized in that a seventh signal (K, L) with four times the frequency compared to the measured first and second signals (A, B) da¬ by the fifth and sixth signal (E, F and . G, H) is deduced that there is a positive value compared to a mean in the case of equality (or inequality) of the fifth and sixth signals (E, F or G, H).