Dynamic error correcting apparatus for inertial navigation

• US 5,410,487 A
• Filed: 02/22/1993
• Issued: 04/25/1995
• Est. Priority Date: 02/28/1992
• Status: Expired due to Term

• Current Assignee: Japan Aviation Electronics Industry Limited
• Original Assignee: Japan Aviation Electronics Industry Limited
• Inventors: Hirose, Yoshio, Okayama, Hiroshi, Ito, Satoshi, Kobayashi, Masao
• Primary Examiner(s): Teska, Kevin J.
• Assistant Examiner(s): Wieland, Susan
• Application Number:
  US08/020,840
• Time in Patent Office: 792 Days
• Field of Search: 364/443, 364/453, 364/454, 364/459, 364/571, 73/178 R
• US Class Current: 701/220
• CPC Class Codes: G01C 21/188 for accumulated errors, e.g. by coupling inertial systems with absolute positioning systems
• CPC Class Codes: G01C 25/005 initial alignment, calibration or starting-up of inertial devices

Abstract

A counting section includes: a first gyro pulse counter which counts gyro pulses from each of X-, Y-, Z- and S-axis gyroscopes during each counting period after being reset immediately before the start of the counting period and outputs the count value as a first gyro pulse count value at fixed time intervals; and a second gyro pulse counter which is reset at said fixed time intervals, counts the gyro pulses and outputs the count value as a second gyro pulse count value. A dynamic error calculating section includes: gyro multipliers/subtractors whereby, for each combination of two different main axes, a mutual product difference of the gyro pulse count values for the two axes is calculated as a main-axis system gyro pulse error and, for each combination of one of the X, Y and Z axes and the S axis, a mutual product difference of the gyro pulse count values for the S axis and each of the X, Y and Z axes is calculated as an auxiliary-axis system gyro error; and a gyro error integrating section whereby each of the X-axis, Y-axis and Z-axis system gyro errors and the auxiliary-axis system gyro error, provided at the fixed time intervals, are accumulated within each calculation period to obtain a gyro error integrated value. A strap-down calculating processor uses the gyro error integrated values from the gyro error integrating section to calculate the correctional quantity of a coning error for each system wherein one of the X, Y and Z axes is replaced with the S axis.

Claims

1. A dynamic error correcting apparatus for an inertial navigation system having inertia sensors provided on at least four axes, respectively, each of said inertia sensors for said four axes including a gyroscope, said apparatus comprising:

a counting section including first gyro pulse counting means which counts gyro pulses from said gyroscope of each axis during each of a plurality of predetermined calculation periods after being reset immediately before the start of said calculation period and outputs, at fixed time intervals, the count value as a first gyro pulse count value, and a second gyro pulse counting means which is reset at fixed time intervals, counts said gyro pulses and outputs the count value as a second gyro pulse count value;

a dynamic error calculating section including gyro multiplying/subtracting means whereby if three predetermined ones of said at least four axes are used as main axes and one of the remaining axes is used as an auxiliary axis, a difference between the product of said first gyro pulse count value for one main axis in all combinations of two different main axes selected from said remaining main axes and said second gyro pulse count value for the other main axis and the product of said first gyro pulse count value for said other main axis and said second gyro pulse count value for said one main axis is calculated as a main axis system gyro pulse error and a difference between the product of said first gyro pulse count value for said auxiliary axis in each combination of said auxiliary axis and one of said main axes and said second gyro pulse count value for said one of said main axes and the product of said first gyro pulse count value for said one of said main axes and said second gyro pulse count value for said auxiliary axis is calculated as an auxiliary-axis system gyro, and gyro error integrating means whereby said main-axis system gyro error and said auxiliary-axis system gyro error, obtained at said fixed time intervals, are accumulated within said each calculation period to obtain a gyro error integrated value; and

a strap-down calculation processor which is supplied with said count values from said counting section and said dynamic error values from said dynamic error calculating section and calculates inertia information of an inertial object on the basis of said count values and said dynamic error values, said strap-down calculating processor being used in common to said inertia sensors of said at least four axes;

said strap-down calculating processor being operative to use said gyro error integrated values from said gyro error integrating means to calculate a correctional quantity of a coning error in each system in which one of said main axes is replaced by said auxiliary axis.

2. The dynamic error correcting apparatus of claim 1,

wherein said inertia sensor of each axis includes an accelerometer;

wherein said counting section includes acceleration pulse counting means which is reset for each axis at said fixed time intervals, counts acceleration pulses from said accelerometer and outputs the count value as an acceleration pulse count value;

wherein said dynamic error correcting section includes;

acceleration error multiplying/subtracting means whereby a difference between the product of said first gyro pulse count value for said one main axis in all combinations of two different main axes selected from said main axes and said acceleration pulse count value for said other main axis and the product of said first gyro pulse count value for said other main axis and said acceleration pulse count value for said one main axis is calculated as a main-axis system acceleration error, and a difference between the product of said first gyro pulse count value for said auxiliary axis in each combination of said auxiliary axis and one of said main axes and said acceleration pulse count value for said main axis and the product of said first gyro pulse count value for said main axis and said acceleration pulse count value for said auxiliary axis is calculated as an auxiliary-axis system acceleration error; and

acceleration error integrating means whereby said main-axis acceleration error and said auxiliary-axis acceleration error, obtained at said fixed time intervals, are accumulated within said each calculation period to obtain an acceleration error integrated value; and

wherein said strap-down calculating processor uses said acceleration error integrated value from said acceleration error integrating means to calculate the correctional quantity of a sculling error in each system wherein one of said main axes is replaced with said auxiliary axis.