Data processing: measuring – calibrating – or testing – Calibration or correction system – Signal frequency or phase correction
Reexamination Certificate
2001-11-20
2003-12-09
Bui, Bryan (Department: 2863)
Data processing: measuring, calibrating, or testing
Calibration or correction system
Signal frequency or phase correction
C702S085000, C702S107000
Reexamination Certificate
active
06662131
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The invention relates to a method and a device for conditioning a periodic analog signal to predetermined positive and negative desired peak values.
2. Description of the Related Art
In position measurements, and in particular measuring distances, rotational speeds or angles of rotation, use is made of incremental measurement systems using sensors. Sensors provide two alternating periodic electrical signals being phase-displaced by 90° relative to each other. Signals of this type are also called orthogonal. The sensor usually senses a material measured, e.g. a marked code disk or a code ruler. The generated signals are in most cases of sinusoidal shape, but may also be triangular or trapezoidal in shape. For the sake of simplification, reference will be made in the following to sine and cosine signals. The amplitudes of sinusoidal signals in sensors or other devices vary, are age-dependent, depend on operating frequency, temperature, and supply voltage, and are subject to the influence of the material measured. These influences may lead to fluctuations in signal deviation, including fluctuations of signal amplitude. However, fluctuations in signal offset are also possible. Finally, signal phase deviations may also occur, in particular due to geometric or mechanical shift or changes in the sensor in connection with the scanned material measure.
In order to achieve synchronization in such incremental measurement systems, a synchronization signal is also provided in many cases which, due to its asymmetrical, periodic signal shape, enables a synchronization of the alternating signals to the material measure and thus a unique definition of a coordinate system.
Faulty electrical signals considerably limit the performance of such measurement systems and lead to errors in the detected distances, rotational speeds or angles of rotation.
A method for correcting the aforementioned fluctuations of amplitude is known from patent DE 38 43 108. The known method includes checking whether the positive and negative peak values of the sine and cosine signals have their peaks within a certain window. If this is not the case, the signal is corrected thereafter by suitable amplifications or by suitable additions. The type of correction is selected according to whether the signal is greater or less than the window, or to which correction was performed in the previous half-wave. Therefore, signal deviations from the window may require many periods for necessary conditioning. This may have an adverse effect on the first calibration upon power-on or even make necessary signal conditioning virtually impossible.
Patent EP 0,489,936 proposes a further improvement to the method described in patent DE 38 43 108, which reduces the circuitry overhead.
Patent application DE 197 12 622 describes an arrangement and a method for correcting erroneous signals in incremental measurement devices. For signal conditioning, a microprocessor is employed, which determines correcting factors in a closed loop in order to achieve higher precision.
The document “Die neue Dimension in der Weg- and Winkelmesstechnik”, R. Burgschat, F & M, Feintechnik, Microtechnik, Microelektronik, Volume 10, 1996, discloses the use of digital potentiometers in an application specific integrated circuit (ASIC) for signal correction.
It is known from patent application DE 42 42 145 to correct a phase deviation of sinusoidal signals by summing and subtracting both signals to obtain further sinusoidal signals which no longer exhibit the statistic phase deviation, but have an exact phase shift of 900.
Based upon the foregoing, there is a need for a technique which simply and effectively conditions periodic signals within a relatively short period of time.
SUMMARY OF THE INVENTION
Embodiments of the present invention overcome shortcomings in prior techniques and satisfy a significant need for conditioning a periodic analog signal to obtain predetermined positive and negative desired peak values, and allowing a correction to be obtained within few signal periods without utilization of a microprocessor.
According to exemplary embodiments of the present invention, the difference between the actual peak value of the periodic analog signal and a predetermined, desired peak value is stepwise reduced and compensated by repeated adjustment of the analog signal using modifying steps within a part of the period of the analog signal, with each modifying step including one multiplicative and one additive correcting step.
Upon detection of an actual peak value of the signal, the difference to the predetermined, desired peak value is no longer compensated stepwise over several periods by performing an adjusting step every half period of the analog signal, as seen in prior techniques. Rather, a multiplicity of adjusting steps are performed. Each adjusting step includes two correcting steps, namely one multiplicative correcting step, which increases or decreases the signal amplitude, and an additive correcting step, which adds a positive or a negative constant or offset to the signal, thus changing the signal level. Both correcting steps are carried out substantially simultaneously. This procedure offers the advantage of rapid signal conditioning.
Thus, with each adjusting step, the signal is changed in two respects. On the one hand, the signal is subjected to a multiplicative correction, on the other hand, to an additive correction. Both corrections are always performed in one single adjusting step. In general, the multiplicative and/or additive correcting steps are freely selectable, but may be fixed. The incremental procedure allows four different adjusting steps: an increasing, multiplicative correcting step in combination with an additive correcting step in a positive direction; an increasing multiplicative correcting step in combination with an additive correcting step in a negative direction; a reducing multiplicative correcting step in combination with an additive correcting step in a positive direction; and a reducing multiplicative correcting step in combination with an additive correcting step in a negative direction. The type of increasing step actually used conveniently depends on the position of the current actual peak value of the signal to be corrected relative to the predetermined desired peak value, and on the part of the period in which the actual peak value was detected. A change of the signal and a comparison of the actual peak value with the desired peak value are effected until no further conditioning is needed or an abort criterion is reached. The conditioning signal converges particularly fast towards the predetermined target values by selecting multiplicative and additive correcting steps according to the following table.
Actual peak value
compared to
Modifying stop
Part of the
predetermined
Multiplicative
Additive
period
values
correcting step
correcting step
positive
greater than desired
+1
−1
peak value
positive
less than desired
−1
+1
peak value
negative
greater than desired
−1
+1
peak value
negative
less than desired
+1
−1
peak value
In this table, a positive
egative part of the period is understood to be a part of the period during which the signal is greater/less than zero. The figures “−1” and “+1” in the column of the multiplicative and the additive correcting step respectively indicate whether the step is an increasing or a decreasing multiplicative step, or an additive correcting step in a positive or a negative direction.
Exemplary embodiments of the present invention are particularly easy to carry out if the frequency at which the stepwise modification is carried out is sufficiently high relative to the bandwidth of the signal to be corrected, because it may then be assumed that the signal value used for comparison with the desired peak value remains essentially unchanged when the modifications are performed.
If this requirement cannot be fulfilled, e.g. because rapidly changing signals are to be conditioned, the actual p
Franz Heinz-Günther
Freitag Hans-Joachim
Schmidt Andreas
Bui Bryan
Jenkins & Gilchrist, P.C.
Optolab Licensing GmbH
LandOfFree
Method and device for conditioning a periodic analog signal does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and device for conditioning a periodic analog signal, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and device for conditioning a periodic analog signal will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3144052