CN103453904B - A kind of redundancy configuration structure of Inertial Measurement Unit - Google Patents

Abstract

The invention discloses a kind of redundancy configuration structure of Inertial Measurement Unit, IMU1 is arranged on the side 1 of positive tetrahedron, bottom center and side 1 center superposition of IMU1 are installed, the X1 axle of IMU1 is parallel to BD limit, Y1 axle is perpendicular to BD limit, X1, Y1, Z1 axle of IMU1 is overlapped with the X, Y, Z axis of carrier coordinate system respectively, and IMU2, IMU3 are embedded on side 2, side 3 respectively, the bottom center of IMU2, IMU3 respectively with the center superposition of side 2, side 3; The Z1 axle of IMU1 is placed outwardly perpendicular to side 1, and the Z2 axle of IMU2, the Z3 axle of IMU3 are placed outwardly perpendicular to side 2, side 3 respectively; Make Y1, Y2, Y3 axle of IMU1, IMU2, IMU3 all point to tessarace perpendicular to base, so X1, X2, X3 axle is parallel to base, so far forms three IMU module oblique redundancy configuration structure.This method, while realizing the full attitude Navigation of MAUV, considerably improves the reliability of navigational system.

Description

A kind of redundancy configuration structure of Inertial Measurement Unit

Technical field

The present invention relates to miniature autonomous underwater robot inertial navigation field, a kind of redundancy configuration structure of Inertial Measurement Unit specifically.

Background technology

Miniature autonomous underwater robot (MicroAutonomousUnderwaterVehicle, be called for short " MAUV ") be a kind ofly having from taking power, the autonomous underwater vehicle that operates be carried out by designing program, because its cost, power consumption and power consumption requirements are very low, therefore in water, navigate mode adopts the mode of MEMS inertial navigation system, earth-magnetic navigation and Doppler log combination.MAUV and the water surface are not contacted directly, in operational process by acoustic communication system from the water surface receive simple instruction then change course, the degree of depth, collection data.MAUV can carry out a series of operations such as deep-sea search, observation, identification, sampling, salvaging, is that a kind of security is high, lightweight, size is little, cost low " intelligent robot ".

MEMS (micro electro mechanical system) (MEMS) inertial navigation system is by formations such as Inertial Measurement Unit (InertialMeasurementUnit is called for short " IMU ", comprises three axis MEMS gyro and accelerometer), navigational computer and power modules.When employing gyro redundant configuration mode just can realize full attitude Navigation, and precision and the reliability of navigational system can be improved.Be applied to traditional mechanical gyro and the optical gyroscope redundancy comparative maturity of aviation field, 4 gyros usually adopted and 6 gyro schemes.The seventies, Sperry was that NASA Marshall center have developed 6 gyro redundant systems, the sensitive axis of each SLIC-15 laser gyro in system becomes 64 ° of angles with adjacent gyro, each gyro can detect the motion around two axles, when all 6 gyros all normally work, it can improve the measuring accuracy of system, the fault of any 2 gyros can also be detected, and abandon its misdata.

From disclosed document, the gyro redundancy scheme that the SIRUTM of Northrop-Grumman company development adopts is the most successful, it is made up of 4 hemispherical reso nance gyroscopes (HRG) and 4 accelerometers, for attitude detection and the control of aerospacecraft, from 1996 so far, in space, successfully run 17 years, demonstrate feasibility and the reliability of this Redundancy Design.

By MEMS Accuracy, MEMS gyro redundancy application is seen in the little of report, and along with MEMS gyro precision constantly breaks through, and the continuous reduction of volume and cost, this provides very big convenience for gyro Redundancy Design.For adapting to the requirement of high precision, high reliability navigation, lot of domestic and foreign researcher proposes multiple gyro redundant configuration scheme, as positive tetrahedron, regular hexahedron, regular octahedron, regular dodecahedron, regular dodecahedron scheme etc.

Boat appearance when MAUV navigates by water under water depends on MEMS inertia system and measures.Inertial navigation is that utilize the rotational angular velocity of gyroscope survey carrier, the line acceleration of motion of accelerometer measures carrier, obtains attitude of carrier, speed, positional information through integration, realizes the technological means of navigation purpose according to newton's principle of inertia.Its independence is high, but navigation error accumulates in time, therefore needs MAUV to emerge to receive GPS or Big Dipper signal to revise inertial navigation system every a period of time.Usual GPS or Beidou receiver are arranged on MAUV head, makeover process needs MAUV to keep being approximately perpendicular to surface level state, now the angle of pitch is close to 90 °, course angle and roll angle cannot be determined (unusual appearance), therefore need to take necessary innovative approach, thus make MAUV can do the motor-driven of arbitrary form, comprise on continuous rolling, new line and diving or dive of bowing.

Summary of the invention

One is the object of the present invention is to provide to occur the problem of unusual appearance for rolling and course when the angle of pitch is ± 90 ° to MAUV in motion process, the redundancy configuration structure of a kind of Inertial Measurement Unit proposed, this structure, while realizing the full attitude Navigation of MAUV, considerably improves the reliability of navigational system.

The technical solution adopted for the present invention to solve the technical problems is:

Technical scheme of the present invention is: adopt three IMU module oblique redundancy configuration structure, wherein IMU1 is arranged on the side 1 of positive tetrahedron, side 1 is face BCD, bottom center and side 1 center superposition of IMU1 are installed, the X1 axle of IMU1 is parallel to BD limit, Y1 axle is perpendicular to BD limit, X1, Y1, Z1 axle of IMU1 is overlapped with the X, Y, Z axis of carrier coordinate system respectively, IMU2, IMU3 are embedded in respectively on side 2, side 3, side 2 is face ABC, side 3 is face ABD, the bottom center of IMU2, IMU3 respectively with the center superposition of side 2, side 3; The Z1 axle of IMU1 is placed outwardly perpendicular to side 1, and the Z2 axle of IMU2, the Z3 axle of IMU3 are placed outwardly perpendicular to side 2, side 3 respectively; Make Y1, Y2, Y3 axle of IMU1, IMU2, IMU3 all point to tessarace perpendicular to base, so X1, X2, X3 axle is parallel to base, so far forms three IMU module oblique redundancy configuration structure.

Three described IMU module oblique redundancy configuration structure, wherein 9 inertial sensor parts (gyro or accelerometer) are by G1, G2, G3, G4, G5, G6, G7, G8, G9 serial number.

Described IMU is MIMU (Micro Inertial Measurement Unit) (MIMU), is wherein integrated with three-axis gyroscope, three axis accelerometer and three axle magnetometers, and has completed demarcation and the error compensation in early stage; Said MIMU have employed the communication modes of Serial Peripheral Interface (SPI) (SerialPerpheralInterface is called for short SPI), be a kind of high speed, full duplex, synchronous communication bus, and SPI is with master-slave mode work.

Beneficial effect of the present invention is mainly manifested in: described Inertial Measurement Unit has: 1, adopt IMU redundancy scheme, avoid and adopt single gyro and single accelerometer to form redundant system, reduce the design difficulty of redundant system, reduce volume, and adopt the IMU of technology maturation on the market, reduce technical risk; 2, have employed three IMU module oblique redundancy configuration structure, be different from traditional orthogonal mounting means of three axles, each measurement axle has the measured value of multiple redundancy, avoid when MAUV comes back or bow (pitch angle close ± 90 °), course angle and roll angle cannot the problems of definite value, realize the full attitude Navigation of MAUV in water and resolve; 3, compared with the system that forms of system and single IMU of three IMU composition, reliability significantly increases.

Accompanying drawing explanation

There is unusual appearance schematic diagram in Fig. 1 course and rolling;

Fig. 2 tri-IMU module oblique redundant configuration schematic diagram;

The axial orientation figure of Fig. 3 ADIS16405;

Fig. 4 IMU Redundant system reliability contrast table;

Fig. 5 redundant digit-reliability curves figure.

Embodiment

Elaborate to embodiments of the invention below, the present embodiment is implemented under premised on technical solution of the present invention, give detailed embodiment and concrete operating process, but protection scope of the present invention is not limited to following embodiment.

Because the navigation error of MAUV accumulates in time, therefore needing to emerge every a period of time receives GPS or Big Dipper signal and revises inertial navigation system.Usual GPS or Beidou receiver are arranged on MAUV head, makeover process needs MAUV to keep being approximately perpendicular to surface level state, now the angle of pitch is close to 90 °, with reference to Fig. 1, (left figure is normal phenomenon schematic diagram, right figure is unusual appearance schematic diagram), course angle and roll angle cannot be determined (unusual appearance), therefore need to take necessary innovative approach, thus make MAUV can do the motor-driven of arbitrary form, comprise on continuous rolling, new line and diving or dive of bowing.

With reference to Fig. 2, the MIMU that three datum clamp faces of positive tetrahedron are installed is the ADIS16405 of ADI company of the U.S., it is integrated with three-axis gyroscope, three axis accelerometer and three axle magnetometers, and before dispatching from the factory, ADIS16405 has completed demarcation and the error compensation in early stage, and it is simple, convenient to use.In addition, the communication modes of ADIS16405 adopts Serial Peripheral Interface (SPI) (SerialPerpheralInterface is called for short SPI), and it is a kind of high speed, full duplex, synchronous communication bus, only needs 4 lines, has saved the pin of chip, is simple and easy to use.Further, SPI, with master-slave mode work, facilitates the data acquisition of many IMU.

With reference to Fig. 3, describe the axial orientation figure (a of ADIS16405 _x, a _y, a _zrepresent that acceleration exports, g _x, g _y, g _zrepresent that gyro exports, m _x, m _y, m _zrepresent that magnetic field exports).After powering on, ADIS16405 sensing system can independently start, and then starts the inertia measurement data that output sampling rate is 819.2.After each sampling period, the Data import of sensor, in output register and DIO1 pulse, provides the data controlling signal that new, thus for drivetrain irrespective of size Interrupt Service Routine.In a typical system, primary processor is by SPI interface access data register.

Launch research for the two IMU redundant configuration be made up of IMU1 and IMU2 below, three IMU oblique redundant configuration are similar.If 6 inertial sensor part measured values are respectively z ₁, z ₂... z ₆, the true carrier component of coordinate axis (x, y, z) is ω x, ω y, ω z.Calculated by geometry, the relation between 6 inertial sensor part measured values and carrier actual value can be obtained, write as measurement equation as follows:

$Z=\mathrm{HX}=\left[\begin{array}{ccc}1& 0& 0\\ 0& 1& 0\\ 0& 0& 1\\ -0.5& -0.8660& 0\\ -0.2887& 0.1667& -0.9428\\ 0.8165& -0.4714& -0.3333\end{array}\right]\left[\begin{array}{c}{\mathrm{\ω}}_x\\ {\mathrm{\ω}}_y\\ {\mathrm{\ω}}_z\end{array}\right]$

Data processing is carried out, if require the estimation selecting X with least-squares estimation make following quadratic performance index reach minimal value, so just claim this to estimate for the least-squares estimation of X, through can be calculated:

$\hat{X}\left(Z\right)={\left(H^{T}H\right)}^{-1}{H}^{T}Z=\left[\begin{array}{cccccc}0.5& 0& 0& -0.25& -0.1443& 0.4082\\ 0& 0.5& 0& -0.433& 0.0833& -0.2357\\ 0& 0& 0.5& 0& -0.4714& -0.1667\end{array}\right]Z$

In MAUV operational process, the system measuring unit as a whole that two IMU is formed, 6 measured values obtained are transformed into the angular speed on body axis system through above formula and compare force information, when through the navigation calculation MAUV angle of pitch out close ± 90 ° time, now from IMU1 and IMU2 optional one, the information gathering single IMU carries out navigation calculation, but what now obtain is not real navigation information, should carry out being converted to actual navigation information according to the mechanical relation between IMU1 and IMU2, so far solving MAUV cannot the problem of definite value in singular point place course angle and roll angle.

Usually, reliability be defined as system under prescribed conditions with the probability of normal work in the schedule time.It is generally acknowledged, the number of times that inertial sensor part breaks down is a stochastic variable, the probability that x fault just occur in time interval t can be similar to Poisson distribution represent for:

$P\left(x\right)=\frac{{\left(\mathrm{\λt}\right)}^x{e}^{-\mathrm{\λt}}}{x!}$

In formula, λ is failure rate; λ t is the mean failure rate number of times occurred in time t.

The fiduciary level of system, it represents primary fault also nonevent probability in time t, is written as following form:

R(t)=e ^-λt

Therefore, the mean free error time of system can be expressed as:

$T_{\mathrm{MTBF}}={\∫}_0^{\∞}R\left(t\right)\mathrm{dt}=\frac{1}{\mathrm{\λ}}$

So, the fiduciary level R of the redundant system be made up of n inertial sensor part _n(t) be:

$R_n\left(t\right)=\underset{i=3}{\overset{n}{\mathrm{\Σ}}}{C}_n^i{\left[R\left(t\right)\right]}^i{[1-R\left(t\right)]}^{n-i}$

The then mean free error time T of this system _{(MTBF) n}for:

$T_{\left(\mathrm{MTBF}\right)n}={\∫}_0^n{R}_n\left(t\right)\mathrm{dt}$

With reference to Fig. 4, for above-mentioned configuration mode, the situation of any three capable not full ranks in H should be considered, and removed.Suppose to be independent of each other between three gyros (or accelerometer) in IMU, for the redundant system be made up of IMU, IMU quantity is more, and system reliability is inevitable to be improved thereupon.

With reference to Fig. 5, from the angle of system reliability, the scheme that IMU number is many is better than the few scheme of number.Compare with the system only having single IMU to form, the system reliability of three IMU compositions significantly increases.

Claims (3)

1. the redundancy configuration structure of an Inertial Measurement Unit, it is characterized in that: adopt three Inertial Measurement Units and IMU module oblique redundancy configuration structure, wherein IMU1 is arranged on first side (1) of positive tetrahedron, first side (1) is face BCD, bottom center and the first side (1) center superposition of IMU1 are installed, the X1 axle of IMU1 is parallel to BD limit, Y1 axle is perpendicular to BD limit, make the X1 of IMU1, Y1, Z1 axle respectively with the X of carrier coordinate system, Y, Z axis overlaps, IMU2, IMU3 is embedded in the second side (2) respectively, on 3rd side (3), second side (2) is face ABC, 3rd side (3) is face ABD, IMU2, the bottom center of IMU3 respectively with the second side (2), the center superposition of the 3rd side (3), the Z1 axle of IMU1 is placed outwardly perpendicular to the first side (1), and the Z2 axle of IMU2, the Z3 axle of IMU3 are placed outwardly perpendicular to the second side (2), the 3rd side (3) respectively, make Y1, Y2, Y3 axle of IMU1, IMU2, IMU3 all point to tessarace perpendicular to base, namely Y1 axle reverse extending line points to summit C, and Y2, Y3 axle all points to summit A, make X1, X2, X3 axle be parallel to base BD, BC and BD respectively, form three IMU module oblique redundancy configuration structure.

2. the redundancy configuration structure of Inertial Measurement Unit as claimed in claim 1, it is characterized in that: described Inertial Measurement Unit is MIMU (Micro Inertial Measurement Unit), wherein be integrated with three-axis gyroscope, three axis accelerometer and three axle magnetometers, and complete demarcation and the error compensation in early stage.

3. the redundancy configuration structure of Inertial Measurement Unit as claimed in claim 2, it is characterized in that: described MIMU (Micro Inertial Measurement Unit) have employed the communication modes of Serial Peripheral Interface (SPI), be a kind of high speed full duplex, synchronous communication bus, and SPI is with master-slave mode work.