RU2790548C1 - Method for correction of the gyro vertical by the angle of attack - Google Patents

Abstract

FIELD: measuring technology.

SUBSTANCE: invention relates to measuring technology and can be used for sea, air and land objects. The method for correction of the gyro vertical by the angle of attack is that based on the signals coming from the angular velocity sensors and corresponding to the angular velocities of the object, as well as the signals of the current values of roll and pitch, these signals are integrated and converted, additionally using signals equal to the calculated angle of attack, which is determined by an indirect method for calculation according to the equations of flight dynamics, including normal overload, as well as flight parameters coming from the air signal system. At the same time, the flight parameters include the parameters of the velocity head, horizontal and vertical airspeed, wing area and weight of the aircraft, lift coefficient. And the angles of roll and pitch are determined through the calculated angle of attack, using angular velocities taking into account the assigned threshold of rotation intensity, according to which the time constant of the integrators switches from a small to a large value when the threshold of rotation intensity is exceeded.

EFFECT: providing the aircraft with roll and pitch angles in standby mode with the required accuracy and reducing the power requirements of the backup onboard computer.

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Description

The invention relates to measuring technology and can be used for marine, air and ground objects. The objective of the invention is to reduce the requirements for the computing power of the on-board computer of the backup gyro-vertical by creating a method for continuous correction according to the estimated angle of attack of the aircraft.

In a strapdown gyro-vertical, the roll and pitch angles are calculated from information from the angular velocity sensors.

The main disadvantage of strapdown systems is the accumulation of errors, so much attention is paid to the accuracy of the gyroscopes used. This disadvantage is eliminated by correcting the orientation according to the readings of the accelerometers, which eliminate the accumulation of errors. At the same time, gyroscopes reduce the influence of aircraft dynamics on accuracy. This method of correction is called pendulum. The attractiveness of pendulum correction lies in its simplicity, as well as in the elimination of the need to take into account the shape of the Earth, its angular velocity and the location of the aircraft. The disadvantage is the difficulty of separating the gravitational components from the accelerations measured by accelerometers in flight.

A known Method for correcting a strapdown inertial navigation system is described in patent RU 2564380, IPC G01C 21/06, published on September 27, 2015, Bulletin No. 27, adopted by us as a prototype.

In a known method, based on the signals coming from the accelerometers included in the INS, the module of absolute acceleration acting on the object on which the INS is installed is determined, the signals corresponding to the angular velocity of the object are used and the signal corresponding to the earth's speed is evaluated, these signals are combined and of the converted signals corresponding to linear accelerations taking into account the flight parameters of the object, and the adaptive assessment of the roll and pitch is carried out using the Kalman filter, in which the gain varies depending on the current values of the overload modules and linear velocity, as well as angular velocities.

The disadvantage of the known method lies in the fact that when maneuvering the aircraft, this method has insufficient accuracy. This can lead to significant errors as a result of the constant maneuvering of highly maneuverable aircraft. For recursive estimation of roll and pitch angles using the Kalman filter, a sufficiently powerful backup onboard computer is required.

The purpose of the claimed invention is to provide the aircraft with roll and pitch angles in standby mode with the required accuracy and to reduce the power requirements of the standby onboard computer.

This goal is achieved due to the fact that in the method for correcting the gyro-vertical by the angle of attack, in which, based on the signals coming from the angular velocity sensors and corresponding to the angular velocities of the object, as well as the signals of the current roll and pitch values, these signals are combined and converted, additionally use signals equal to the value of the calculated angle of attack, which is determined by an indirect calculation method according to the flight dynamics equations, including normal overload, as well as flight parameters coming from the air signal system (ACS) - dynamic head parameters, horizontal and vertical air speeds, wing area and the weight of the aircraft, the lift coefficient, - in this case, the roll and pitch angles are determined through the calculated angle of attack, using the angular velocities, taking into account the assigned rotation intensity threshold, according to which the time constant of the integrators switches from a small to a large value when the threshold is exceeded rotation intensity.

The essence of the invention is illustrated by drawings, where in Fig. 1 shows a block diagram of the roll channel correction, FIG. 2 shows a block diagram of the pitch channel correction. To analyze the accuracy of the operation of the schemes, the processes of the movement of a light aircraft obtained by simulating a flight on a flight simulator were used (Fig. 3-9). In FIG. 3 shows ground speed; in fig. 4 - absolute height; figure 5 - angle of attack; in fig. 6: 1 - angular velocity wx, 2 - angular velocity wy, 3 - angular velocity wz; in fig. 7: 1 - pitch, 2 - roll; in fig. 8: 1 - pitch, 2 - evaluation when combining the inertial course-vertical (IKV) and SVS schemes: in Fig. 9: 1 - roll, 2 - assessment when combining the SCR and SHS schemes.

The essence of the method is described below.

The well-known dynamic Euler equations are used to determine the roll and pitch angles (IKV scheme):

where ω _z and ω _x are the angular velocities along the associated axes of the aircraft, γ and ϑ are the current values of the roll and pitch angles.

These angles can be used to steer the aircraft either directly or after adjusting for the angle of attack. The angle of attack is obtained from the SHS, in which it is determined from the known relations from the aircraft dynamics equations in accordance with the formulas

С _ua =Y _a /(q S);

Y _a \u003d n _ya ⋅ mg,

where C _ya is the lift coefficient,

Y _a - lifting force.

Using the ratio C _ya =f(α), you can get the angle of attack (α). Here C _ya is the current lift coefficient, α is the angle of attack.

It is necessary to write this function into the memory of the on-board computer. This function is known from the results of aerodynamic blowdowns for a particular aircraft. Otherwise, it is calculated from the design parameters of the aircraft. Having the characteristic α=f ^1- (C _ya ), you can calculate the angle of attack.

To determine the roll and pitch angles through airspeed and angle of attack, we use the known expressions from the aircraft flight dynamics (SHS scheme):

The SHS scheme for determining the roll and pitch angles can be used both independently and when combined with the IKV scheme. To analyze the accuracy of the operation of the schemes, both separately and when they were combined, the processes of the movement of a light aircraft obtained by modeling and simulating a flight on a flight simulator were used (Fig. 3-9). All presented processes are coordinated with each other and correspond to the flight of an aircraft along a certain given route.

When modeling, the measurement errors of the sensors were simulated as constant and random.

The time constant T in the IKV schemes was taken equal to 15 s. The parameters obtained with the help of flight simulation on the flight simulator are shown in Fig. 3-7.

Combination of IKV and SHS schemes.

The method of integration was considered, in which the resulting estimates were taken as weighted averages of the estimates of the SCR and SHS schemes.

при |ϑ_ikv-ϑ_cvc|<p_ϑ,

for |ϑ _ikv -ϑ _cvc |<p _ϑ ,

при |ϑ_ikv-ϑ_cvc|ϑ≥p_ϑ,

for |ϑ _ikv -ϑ _cvc |ϑ≥p _ϑ ,

_aikv1 +a _cvc1 =1, _aikv2 +a _cvc2 =1,

при |γ_ikv-γ_cvc|<р_γ,

for |γ _ikv -γ _cvc |<р _γ ,

при |γ_ikv-γ_cvc|≥p_γ,

for |γ _ikv -γ _cvc |≥p _γ ,

b _ikv1 +b _cvc1 =1 b _ikv2 +b _cvc2 =1

Here: a _ikv1 , a _ikv2 , a _cvc1 , a _cvc2 , b _ikv1 , b _ikv2 , b _cvc1 , b _cvc2 - weight coefficients, p _ϑ , p _γ - threshold values of mismatch modulus between estimates of IKV and SHS schemes.

Thresholds and weighting coefficients are assigned in such a way as to give more confidence to the SHS scheme and correct its readings if the estimation outliers are too large, exceeding the dynamic errors of the SCR scheme.

The time constant T of aperiodic links, which play the role of approximate integrators of the Euler equations, is changed depending on the intensity of rotation of the aircraft. The indicator of the intensity of rotation adopted the module of the angular velocity of the aircraft, passed through a low-frequency filter (LPF) of the second order, which is denoted by |ω| _f . LPF time constant 0.5 s.

The rotation intensity threshold Por|ω| _f . The time constant of the integrators switches from a small to a large value when the rotation intensity threshold is exceeded:

T=T _min at _f |ω| _f < Por|ω| _f ,

T=T _max at |ω| _f ≥ Por|ω| _f ,

T _min =30, T _max =500

In FIG. Figures 8 and 9 show the pitch and roll estimates when combining the IKV and SHS schemes.

SHS and IKV schemes provide acceptable accuracy of pitch and roll estimation under the following conditions:

- sufficiently accurate measurement of the angle of attack;

- small influence of wind on the difference between air and ground speeds. 90 degree pitch angle estimates are not supported.

According to the simulation data on the flight simulator and with the specified sensor errors, the integration of the IKV schemes with the SHS schemes provides the standard deviation of errors up to the level of 0.8 degrees, while the roll and pitch estimates are shifted by about 0.5 degrees.

The technical result of using the invention is to reduce the requirements for computing power of the backup gyro-vertical computer and obtain angle values that meet the accuracy requirements for the backup system for determining roll and pitch angles.

Claims (1)

A method for correcting the vertical gyro by the angle of attack, in which, based on the signals coming from the angular velocity sensors and corresponding to the angular velocities of the object, as well as the signals of the current values of roll and pitch, these signals are complexed and converted, additionally using signals equal to the calculated angle of attack, which are determined by an indirect method of calculation according to the flight dynamics equations, including normal overload, as well as flight parameters coming from the air signal system (ASS), - dynamic head parameters, horizontal and vertical air speeds, wing area and weight of the aircraft, lift coefficient, while roll and pitch angles are determined through the calculated angle of attack, using angular velocities, taking into account the assigned rotation intensity threshold, according to which the time constant of the integrators switches from a small to a large value when the rotation intensity threshold is exceeded.

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