CN201133818Y - North finder - Google Patents

Abstract

The utility model relates to a north-finding device used in the field of orientation and location, in particular to an inertial north-finding device using accelerometers as inertial components, which is composed of a servosystem, a motor-driven rotary platform, an encoder, a measuring accelerometer, an additional accelerometer and a data acquiring and processing system; wherein, the encoder is arranged on a motor; the measuring accelerometer and the additional accelerometer are fixed on the rotary platform; the data acquiring and processing system can be connected with a serial port; the measuring axis (a<k1>) of the measuring accelerometer arranged on the edge of the rotary platform is vertical to the surface of the rotary platform; the measuring axis (a<k2>) of the additional accelerometer arranged at the center of the rotary platform is pointed to the measuring accelerometer along the radius vector of the rotary platform. The north-finding device of the utility model has a function of automatic levelling compensation. The levelling compensation includes the compensation of measuring errors caused by levelling errors and the elimination of interference noise generated by levelling errors. Consequently, the north-finding device of the utility model effectively increases measuring precision.

Description

North finder

technical field

The utility model relates to a north-seeking device applied in the field of orientation and positioning, in particular to an inertial north-seeking device using an accelerometer as an inertial device.

Background technique

Inertial north-seeking technology is an important part of the inertial technology field. It obtains north direction information by measuring or sensitive earth speed, so as to measure the true meridian position of any measuring point and realize the process of finding north. With the development of precise measurement technology, many methods for north-finding positioning have emerged, such as: inertial method, astronomical observation method, geodetic method, satellite positioning method, reference object method and other high-precision north-finding methods. However, under special conditions such as tunnels, underwater and other complex terrains and complex weather environments, astronomical observation methods, geodesy methods, satellite positioning methods and reference object methods are all subject to different degrees of conditional constraints, or the accuracy is low, or it cannot be implemented at all. . Only the inertial method can independently complete the north-finding task without being disturbed by natural conditions or the environment, and has the characteristics of long continuous working time and high precision. Therefore, the research on inertial north-finding method has its unique application value.

North-seeking devices have been widely used in many fields. In addition to their very important applications in aviation, aerospace, navigation and weapon guidance, they are also used in other civil projects such as tunnel construction, mining, geodetic survey, and resource survey. It is also increasingly showing broad application prospects in the field. The current north-seeking devices mainly use air-floating rate gyroscopes, dynamic tuning gyroscopes, ring laser gyroscopes, fiber optic gyroscopes, and electrostatic gyroscopes as inertial devices to complete the detection of the earth's velocity, and the cost is very high. With the further improvement of accelerometer manufacturing precision, the non-gyro inertial measurement unit appeared in the 1980s, because it abandoned the expensive gyro, so that the manufacturing cost was greatly reduced. Therefore, it is of great significance to carry out research on non-gyro north-seeking devices in both military and civilian fields.

However, since the non-gyro north-seeking system is based on the principle of Coriolis acceleration, through the dynamic modulation of the turntable, the northward component of the earth's rotation angular velocity and the tangential velocity at this point are combined to generate a Coriolis acceleration output as a sinusoidal signal. By detecting the sinusoidal signal The phase corresponding to the peak value of is the true north direction of the position on the earth. During the measurement process, when the rotation axis of the turntable is tilted at a certain angle, due to the influence of the vertical component of the earth’s velocity, what the system finds is no longer the direction of the northward component of the earth’s rotation, but the direction of the combined rate of the northward component and the vertical component. At present, it is proposed to install an additional accelerometer on the edge of the turntable where the measuring accelerometer is symmetrical, and the measurement axis of the additional accelerometer is parallel to the turntable surface and along the tangential direction of the turntable. The effect of the vertical component of the Earth's velocity is measured by an additional accelerometer when the rotary axis of the turntable is tilted at a certain angle.

However, according to theoretical analysis, due to the inclination of the turntable, there is a periodic acceleration in the vertical direction at the edge of the turntable, which will cause serious interference to the Coriolis acceleration signal to be extracted. Therefore, the size of the leveling error will seriously affect the measurement accuracy of the system, and even the realization of the function, and this part of the system must be filtered out.

Contents of the invention

The purpose of the utility model is to provide a north-seeking device with an improved structure in order to eliminate the influence of the leveling error on the measurement accuracy and filter out the interference caused by the leveling error to the system.

The north-seeking device of the utility model is composed of a servo system, a motor-driven turntable, an encoder set on the motor, a measurement accelerometer fixed on the turntable, an additional accelerometer, and a data acquisition and processing system connected through a serial port. , which is characterized in that the measuring accelerometer is arranged on the edge of the turntable, and its measuring axis a _k1 is perpendicular to the table surface, and the additional accelerometer is arranged at the center of the turntable, and its measuring axis a _k2 is along the vector radius of the turntable Point to measure the accelerometer.

The north-finding device of the utility model has the function of automatic leveling and compensation. The said leveling compensation includes the compensation for the measurement error caused by the leveling error and the elimination of the interference noise caused by the leveling error. Therefore, the measurement accuracy is effectively improved.

Description of drawings

Fig. 1 is the structural representation of the utility model north-seeking device;

Figure 2 is a schematic diagram of the analysis of the influence of leveling errors on accuracy;

Figure 3 is a schematic diagram of interference analysis caused by leveling errors;

Fig. 4 is a schematic diagram of the working process of the north-seeking device of the present invention.

Detailed ways

Below in conjunction with the embodiment that accompanying drawing provides, the utility model is described in further detail.

Referring to Fig. 1, the turntable 3 driven by the servo system, the motor, the encoder arranged on the motor, the measurement accelerometer 1 and the additional accelerometer 2 fixed on the turntable 3, and the data acquisition and processing system connected through the serial port Composition, characterized in that the measuring accelerometer 1 is arranged on the edge of the turntable 3, the distance from the center of the turntable 3 is R, its measuring axis a _k1 is perpendicular to the table, and the additional accelerometer 2 is arranged on At the center o of the turntable 3 , its measuring axis a _k2 points to the measuring accelerometer 1 along the radial direction of the turntable 3 .

The working principle of the utility model north-finding device:

As shown in Figure 2, when the tilt of the turntable ε is a small angle, the azimuth error is:

——纬度角

- latitude angle

和ε是同一个数量级，所以必须进行调平补偿。安装在转台上的附加加速度计2输出信号经转台调制为：in middle latitudes

It is the same order of magnitude as ε, so leveling compensation must be performed. The output signal of the additional accelerometer 2 installed on the turntable is modulated by the turntable as:

a′＝a ₀ ′+gsinεsin(Ωt-ζ)+σ _g ′

In the formula: a ₀ ′ is the zero bias signal of the accelerometer, ε is the inclination angle of the turntable, σ _g ′ is the output signal noise of the accelerometer, and ζ is the azimuth compensation amount caused by the inclination angle.

In the figure, O is the center of the turntable, O′ is the installation center of the inclination angle accelerometer, A and B represent the projection of the initial Coriolis acceleration on R and its orthogonal direction, after filtering by the AC amplifier, the output model can be rewritten as :

a _g ＝gsinεsin(Ωt-ζ)+σ _g ′=CsinΩt-DcosΩt+σ _g ′

In the formula, C=gsinεcosζ, D=gsinεsinζ

C and D can be obtained through synchronous detection, and the estimation of ε and ζ can be obtained through least square processing

$\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; sin</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}\frac{\sqrt{{\mathrm{<span\; class="notranslate">\; C</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}}{\mathrm{<span\; class="notranslate">\; g</span>}}$

$\mathrm{<span\; class="notranslate">\; \&zeta;</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; tg</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}\frac{\mathrm{<span\; class="notranslate">\; D.</span>}}{\mathrm{<span\; class="notranslate">\; C</span>}}$

As shown in Figure 3, OCDE in the figure is the horizontal plane, and OABE is the turntable surface. The measuring accelerometer 1 is installed at point A. When the accelerometer 1 turns to point B, β=Ωt+λ, then

S=BD=EBsinα=Rsinβsinε

Namely: S＝Rsinεsin(Ωt+λ)

Then the acceleration caused by the leveling error measured by the accelerometer 1 at point A can be approximately expressed as:

a _z ＝S″＝-RΩ ² sinεsin(Ωt+λ)

The output signal of the additional accelerometer 2 modulated by the turntable 3 is:

a _o ＝rΩ ² +gsinεsin(Ωt+λ)

Where r is the eccentric radius from the turntable axis, rΩ ² is a constant value, which can be filtered out by the AC amplifier, and its output model can be rewritten as:

a _o ＝g sinεsin(Ωt+λ)

visible, $a_z=-\frac{{\mathrm{R\&Omega;}}^2}{g}{a}_o,$ Regardless of the inclination angle ε.

The disturbance caused by the leveling error which is sensitive to the measuring accelerometer 1 can be eliminated by means of the vector calculation.

It can be seen that by installing the additional accelerometer 2 in the center of the turntable 3 along the radial direction, the noise caused by the leveling error can be eliminated, and the measurement error caused by the leveling error can be corrected.

Referring to Figure 4, during the working process, the motor is driven by the servo system, and the motor drives the encoder, accelerometer 1, and accelerometer 2 to rotate around the axis at a constant speed, and the signals measured by accelerometer 1 and accelerometer 2 are obtained after proportional subtraction. For the Coriolis acceleration signal, combined with the output value of the encoder, the angle between the uncorrected encoder zero position and the north direction is calculated. After the signal output by the accelerometer 2 is processed separately, the measurement error value caused by the leveling error is calculated, and the error value is brought into the previously calculated angle between the zero position of the encoder and the north direction, which is the final measurement result of the north-seeking system .

Claims (1)

1. north finding device, by by servo-drive system, motor-driven turntable (3), be arranged on scrambler on the motor, be installed with measurement accelerometer (1) and coriolis acceleration meter (2) on turntable (3), reaching the data Collection ﹠ Processing System that connects by serial ports forms, it is characterized in that, described measurement accelerometer (1) is arranged on the edge of described turntable (3), its measurement axis a _K1Perpendicular to table top, described coriolis acceleration meter (2) is arranged on the center of turntable (3), its measurement axis a _K2Point to measurement accelerometer (1) along turntable (3) radius vector.

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