Method of compensating periodic signals in sensor output

• US 6,542,842 B2
• Filed: 03/16/2001
• Issued: 04/01/2003
• Est. Priority Date: 03/17/2000
• Status: Expired due to Term

• Current Assignee: Harmonic Drive Systems Inc.
• Original Assignee: Harmonic Drive Systems Inc.
• Inventors: Horiuchi, Masashi, Godler, Ivan
• Primary Examiner(s): SHAH, KAMINI S
• Application Number:
  US09/809,164
• Publication Number:
  US 20010045824A1
• Time in Patent Office: 746 Days
• Field of Search: 702/104, 702/75, 735/040.3, 735/041.1, 735/10, 737/08
• US Class Current: 702/104
• CPC Class Codes: G01D 18/001 Calibrating encoders
• CPC Class Codes: G01D 5/2448 Correction of gain, threshold, offset or phase control
• CPC Class Codes: G01P 21/02 of speedometers
• CPC Class Codes: G01P 3/489 Digital circuits therefor

Abstract

A method of compensating periodic error signals in sensor output is provided. The method comprises obtaining a sum signal from sensing outputs of M sensor elements (where M is a positive integer), obtaining the amplitude and phase of N frequency components included in the sum signal, and calculating a sensing output gain adjustment coefficient for each sensor output. To ensure that a sum signal level obtained by summing a pre-adjustment output of each sensor element multiplied by the gain adjustment coefficient equals a sum signal level obtained by summing the unmodified outputs of the sensors, a gain adjustment coefficient is obtained for each sensor output by using a calculated scaling coefficient to perform pre-adjustment scaling of each gain adjustment coefficient. The adjustment gains thus obtained are used to adjust the gain of each sensor output.

Claims

1. A method of compensating periodic error signals in sensor output, comprising the steps of:

obtaining a sum signal from sensing outputs of M sensor elements (where M is a positive integer);

obtaining amplitude and phase of N frequency components included in the sum signal (where N is a positive integer);

taking a_ij as sensing output amplitude of the jth (j=1 to N) sensor element at the ith (i=1 to N) frequency component, ψ

_ij as phase angle and k_j as sensing output gain adjustment coefficient, obtaining adjustment coefficient kj for each sensor output by the simultaneous equation $\begin{array}{cc}{\left[\begin{array}{c}{a}_{\mathrm{ij}}<br><br>\cos <br><br>\text{\hspace{1em}<br><br>}<br><br>{\mathrm{\phi <br><br>}}_{\mathrm{ij}}\\ a_{\mathrm{ij}}<br><br>\sin <br><br>\text{\hspace{1em}<br><br>}<br><br>{\mathrm{\phi <br><br>}}_{\mathrm{ij}}\end{array}\right]}_{\left(2<br><br>N\times <br><br>M\right)}<br><br>{\left\{k_j\right\}}_{\left(M\right)}=0& \left(7\right)\end{array}$

ensuring that a sum signal level obtained by summing a pre-adjustment output of each sensor element multiplied by the gain adjustment coefficient k_j equals a sum signal level obtained by summing unmodified outputs of said sensors, by obtaining a gain adjustment coefficient k_j for each sensor output by using a scaling coefficient C obtained by $\begin{array}{cc}C=\frac{M}{\underset{j=1}{\overset{M}{\sum <br><br>}}<br><br>k_j}& \left(12\right)\end{array}$

to perform pre-adjustment scaling of each gain adjustment coefficient k_j, and

using each adjustment gain k_j thus obtained to adjust a gain of each sensor output.

2. The method according to claim 1, wherein in place of said simultaneous equation, N frequency components are removed or minimized by using a gain adjustment coefficient obtained for each sensor output by repeating for each sensor output a process comprising changing an output gain of one sensor in small increments while maintaining output gains of other sensors at a constant level.

3. A gain adjustment method for maximizing a specific frequency component in sensor output, comprising the steps of:

obtaining a sum signal from sensing outputs of M sensor elements;

calculating amplitude of specific frequency components from the sum signal;

obtaining sensor output gains at which the specific frequency components are maximized by repeating for each sensor output a process comprising changing the output gain of one sensor in small increments while maintaining output gains of other sensors at a constant level;

ensuring that a sum signal level obtained by summing the outputs of the sensor elements each multiplied by the calculated gain equals a sum signal level obtained by summing unmodified outputs of said sensors, by obtaining an adjustment gain for each sensor output by using scaling to adjust each calculated gain; and

using each adjustment gain thus obtained to adjust the gain of each sensor output signal to generate a sum signal in which said frequency components are maximized.

4. A gain adjustment method for maximizing a specific frequency component in sensor output, comprising the steps of:

obtaining a sum signal from sensing outputs of M sensor elements;

obtaining a peak-to-peak amplitude of the sum signal;

obtaining the sensor output gains that give a minimum peak-to-peak amplitude of the sum signal by repeating for each sensor output a process comprising changing the output gain of one sensor in small increments while maintaining the output gains of other sensors at a constant level;

ensuring that a sum signal level obtained by summing the outputs of the sensor elements each multiplied by the calculated gain equals a sum signal level obtained by summing unmodified outputs of said sensors, by obtaining an adjustment gain for each sensor output by using scaling to adjust each calculated gain; and

using each adjustment gain thus obtained to adjust a gain of each sensor output signal to generate a sensing signal in which there is minimum peak-to-peak amplitude of the sum signal of the sensor outputs.