CN103453904A - Redundancy configuration structure of inertial measurement unit - Google Patents

Abstract

The invention discloses a redundancy configuration structure of an inertial measurement unit. According to the redundancy configuration structure of the inertial measurement unit, an IMU1 is installed on the lateral side 1 of a regular tetrahedron, the center of the bottom surface of the IMU1 coincides with the center of the lateral side 1, the X1 axis of the IMU1 is parallel to the side BD, the Y1 axis of the IMU1 is perpendicular to the side BD, the X1 axis, Y1 axis and Z1 axis of the IMU1 coincide with the X axis, Y axis and Z axis of a carrier coordinate system respectively, an IMU2 and an IMU3 are embedded in the lateral side 2 and in the lateral side 3 respectively, the center of the bottom surface of the IMU2 coincides with the center of the lateral side 2, the center of the bottom surface of the IMU3 coincides with the center of the lateral side 3, the Z1 axis of the IMU1 is arranged facing the outside and is perpendicular to the lateral side 1, the Z2 axis of the IMU2 and the Z3 axis of the IMU3 are arranged facing the outside and are perpendicular to the lateral 2 and the lateral side 3 respectively, the Y1 axis of the IMU1, the Y2 axis of the IMU2 and the Y3 axis of the IMU3 are all perpendicular to the bottom edges and point to the peaks of the regular tetrahedron, then the X1 axis, the X2 axis and the X3 axis are parallel to the bottom edges, and the redundancy configuration structure with the three IMU modules arranged in an oblique crossing mode is formed. According to the redundancy configuration structure of the inertial measurement unit, MAUV omni-posture navigation is achieved, and reliability of a navigation system is improved remarkably.

Description

A kind of redundant configuration structure of Inertial Measurement Unit

Technical field

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

Background technology

Miniature autonomous underwater robot (Micro Autonomous Underwater Vehicle, be called for short " MAUV ") be a kind of autonomous formula underwater vehicle of certainly taking power, being operated by designing program that has, because its cost, power consumption and power consumption requirement are very low, so the mode that in water, navigate mode adopts MEMS inertial navigation system, earth-magnetic navigation and Doppler log to combine.MAUV and the water surface are not contacted directly, in operational process by the acoustic communication system from the water surface receive that simple instruction changes course then, the degree of depth, collection data.MAUV can carry out a series of operations such as deep-sea search, observation, identification, sampling, salvaging, be a kind of safe, 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 (Inertial Measurement Unit, be called for short " IMU ", comprises 3 axis MEMS gyroscope and accelerometer), navigational computer and power modules.When adopting gyro redundant configuration mode just can realize full attitude Navigation, and can improve precision and the reliability of navigational system.Be applied to traditional mechanical gyro and the optical gyroscope redundancy comparative maturity of aviation field, 4 gyros and the 6 gyro schemes that usually adopt.The seventies, Sperry was that 6 gyro redundant systems have been developed at NASA Marshall center, in system, the sensitive axis of each SLIC-15 laser gyro becomes 64 ° of angles with adjacent gyro, each gyro can detect the motion around two axles, when all 6 gyros all work, it can improve the measuring accuracy of system, can also detect the fault of any 2 gyros, 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 consists of 4 hemispherical reso nance gyroscopes (HRG) and 4 accelerometers, attitude detection and control for aerospacecraft, from 1996 so far, successfully move 17 years in space, proved feasibility and the reliability of this Redundancy Design.

Be subject to MEMS device Accuracy, MEMS gyro redundancy application is seen in report seldom, along with the MEMS Gyro Precision constantly breaks through, and constantly the reducing of volume and cost, this provides very big convenience for the gyro Redundancy Design.For adapting to the requirement of high precision, high reliability navigation, lot of domestic and foreign researcher has proposed 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 mainly depends on the MEMS inertia system and measures.Inertial navigation is according to newton's principle of inertia, utilizes the rotational angular velocity of gyroscope survey carrier, and the line acceleration of motion of accelerometer measures carrier, obtain attitude of carrier, speed, positional information through integration, realizes the technological means of navigation purpose.Its independence is high, but navigation error accumulates in time, therefore every a period of time, needs MAUV to emerge to receive GPS or Big Dipper signal is revised inertial navigation system.Usually GPS or Beidou receiver are arranged on the MAUV head, makeover process needs MAUV to keep near vertical in the surface level state, now the angle of pitch approaches 90 °, course angle and roll angle can't be determined (unusual appearance), therefore need to take necessary innovative approach, thereby make MAUV can do the motor-driven of arbitrary form, comprise on continuous rolling, new line and diving or the dive of bowing.

Summary of the invention

The object of the present invention is to provide a kind of for the problem of unusual appearance occurs when the MAUV angle of pitch rolling and course for ± 90 ° time the in motion process, the redundant configuration structure of a kind of Inertial Measurement Unit proposed, this structure, when realizing the full attitude Navigation of MAUV, has improved the reliability of navigational system significantly.

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 redundant configuration structures, wherein IMU1 is arranged on the side 1 of positive tetrahedron, side 1 is face BCD, the bottom center of IMU1 and side 1 center superposition are installed, the X1 axle of IMU1 is parallel to the BD limit, the Y1 axle is perpendicular to the BD limit, X1, Y1, the Z1 axle of IMU1 are 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, the Y3 axle of IMU1, IMU2, IMU3 all perpendicular to base, point to tessarace, X1, X2, X3 axle are parallel to base so, so far form three IMU module oblique redundant configuration structures.

Described three IMU module oblique redundant configuration structures, wherein 9 inertial sensor parts (gyro or accelerometer) are pressed G1, G2, G3, G4, G5, G6, G7, G8, G9 serial number.

Described IMU is MIMU (Micro Inertial Measurement Unit) (MIMU), wherein integrated three-axis gyroscope, three axis accelerometer and three axle magnetometers, and completed demarcation and the error compensation in early stage; Said MIMU has adopted the communication modes of Serial Peripheral Interface (SPI) (Serial Perpheral Interface, be 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 the IMU redundancy scheme, avoided adopting 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, three IMU module oblique redundant configuration structures have been adopted, be different from three traditional axle quadrature mounting meanss, each measures the measured value that axle has a plurality of redundancies, avoided when MAUV comes back or bow (pitch angle approaches ± 90 °), course angle and roll angle can't definite value problem, realize that the full attitude Navigation of MAUV in water resolves; 3, the system that the system of three IMU compositions forms with single IMU is compared reliability significantly to be increased.

The accompanying drawing explanation

The unusual appearance schematic diagram appears in Fig. 1 course and rolling;

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

The axial orientation figure of Fig. 3 ADIS16405;

Fig. 4 IMU redundant system reliability contrast table;

Fig. 5 redundant digit-fiduciary level curve map.

Embodiment

Below embodiments of the invention are elaborated, the present embodiment is implemented take technical solution of the present invention under prerequisite, provided 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 every a period of time, need to emerge and receive GPS or Big Dipper signal is revised inertial navigation system.Usually GPS or Beidou receiver are arranged on the MAUV head, makeover process needs MAUV to keep near vertical in the surface level state, now the angle of pitch approaches 90 °, with reference to Fig. 1, (left figure is the normal phenomenon schematic diagram, right figure is the unusual appearance schematic diagram), course angle and roll angle can't be determined (unusual appearance), therefore need to take necessary innovative approach, thereby make MAUV can do the motor-driven of arbitrary form, comprise on continuous rolling, new line and diving or the dive of bowing.

With reference to Fig. 2, the MIMU installed on three datum clamp faces of positive tetrahedron is the ADIS16405 of U.S. ADI company, it is integrated three-axis gyroscope, three axis accelerometer and three axle magnetometers, the front ADIS16405 that dispatches from the factory has completed demarcation and the error compensation in early stage, uses simple, convenient.In addition, the communication modes of ADIS16405 adopts Serial Peripheral Interface (SPI) (Serial Perpheral Interface 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.And SPI, with master-slave mode work, has facilitated the data acquisition of many IMU.

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

The two IMU redundant configuration that are comprised of IMU1 and IMU2 of below take are launched research as example, and three IMU oblique redundant configuration similarly.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.Calculate by geometry, can obtain the relation between 6 inertial sensor part measured values and carrier actual value, write as the measurement equation as follows:

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

Carry out the data processing with least-squares estimation, if require to select the estimation of X

make following quadratic performance index

reach minimal value, so just claim this estimation

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

Usually, the reliability probability that works under rated condition and in the schedule time that is defined as system.It is generally acknowledged, the number of times that the inertial sensor part breaks down is a stochastic variable, and the probability that x fault just occurs in time interval t can be similar to Poisson distribution and be expressed as:

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

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 is illustrated in also nonevent probability of the interior primary fault of time t, is written as following form:

R(t)=e ^-λt

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

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

The fiduciary level R of the redundant system formed by n inertial sensor part so, _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 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, should consider the situation of any three capable not full ranks in H, and be removed.Suppose between three gyros (or accelerometer), to be independent of each other in IMU, for the redundant system consisted 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 the IMU number is many is better than the scheme that number is few.With the system of only having single IMU to form, compare, the system reliability of three IMU compositions significantly increases.

Claims (3)

1. the redundant configuration structure of an Inertial Measurement Unit, it is characterized in that: adopting three Inertial Measurement Units is IMU module oblique redundant configuration structure, wherein IMU1 is arranged on first side (1) of positive tetrahedron, the first side (1) is face BCD, the bottom center of IMU1 and the first side (1) center superposition are installed, the X1 axle of IMU1 is parallel to the BD limit, the Y1 axle is perpendicular to the BD limit, make the X1 of IMU1, Y1, the Z1 axle respectively with the X of carrier coordinate system, Y, Z axis overlaps, IMU2, IMU3 is embedded in respectively the second side (2), on the 3rd side (3), the second side (2) is face ABC, the 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, the Y3 axle of IMU1, IMU2, IMU3 all perpendicular to base, point to tessarace, make X1, X2, X3 axle be parallel to base, form three IMU module oblique redundant configuration structures.

2. the redundant 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 integrated three-axis gyroscope, three axis accelerometer and three axle magnetometers, and completed demarcation and the error compensation in early stage.

3. the redundant configuration structure of Inertial Measurement Unit as claimed in claim 2, it is characterized in that: described MIMU (Micro Inertial Measurement Unit) has adopted 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.

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