CN101709975B - Estimation and compensation method for unbalanced moment of aerial remote sensing inertially stabilized platform - Google Patents

Abstract

A method for estimating and compensating the unbalanced moment of an aerial remote sensing inertial stabilization platform. Estimate the unbalanced torque of the platform based on the real-time measured platform acceleration and torque motor current information, then calculate the torque motor current value required to offset the unbalanced torque, and compensate this current value to the current of the torque motor current loop As given, the torque motor outputs a resistance torque that is equal in size to the unbalanced torque and opposite in direction, suppresses the disturbance of the unbalanced torque of the stable platform, reduces the requirement for the torque stiffness of the stable platform, and improves the stability accuracy of the stable platform. The invention has the characteristics of strong stability and high precision, and is suitable for an aerial remote sensing inertial stabilization platform with unbalanced moment and tracking the local geographical level.

Description

A kind of unbalanced moment of aerial remote sensing inertially stabilized platform is estimated and compensation method

Technical field

The present invention relates to a kind of unbalanced moment of aerial remote sensing inertially stabilized platform estimates and compensation method; Can be used for of the compensation of the airborne remote sensing of various middle and high precision, be particularly suitable for the airborne remote sensing inertially stabilized platform that has mass unbalance and follow the tracks of local geographical level with the inertially stabilized platform unbalanced moments.

Background technology

The airborne remote sensing system maneuverability, real-time repeated measures property, remote sensing equipment convertibility, obtain high-definition remote sensing data capability, financial cost and stereopsis etc. a lot of aspect, all have a special advantages.Therefore, at western developed country, be used for city planning and base map and survey and draw about high resolution space data more than 65% and rely on the airborne remote sensing system to guarantee.The high resolving power earth observation is the important directions of airborne remote sensing system development, but because air turbulence and the influence of carrying the machine oneself factor, and carrying the machine body can't held stationary, causes the imaging load optical axis that is installed on the machine of carrying to rock, and image quality descends.The high resolving power airborne remote sensing platform that inertially stabilized platform is formed is the effective measures that address this problem.Inertially stabilized platform is used to isolate the angular motion of the machine of carrying, and follows the tracks of local geographical level, eliminates disturbance torque to the imaging load influence, makes the stable imaging of imaging load.Airborne remote sensing is a branch of spiral shell tenacious tracking device with inertially stabilized platform, and its 26S Proteasome Structure and Function and traditional airborne photoelectric hang the storehouse has similarity, hangs the storehouse but be different from traditional airborne photoelectric.Photoelectricity hangs the storehouse only needs to carry antenna, the first-class little load of guiding, thus photoelectricity to hang the storehouse generally lighter, load-bearing capacity is little; And airborne remote sensing need be carried the bigger science camera of quality with inertially stabilized platform, and for the science camera of many camera lenses, its quality can reach 100kg especially, and the weight of platform self requires generally to be no more than 40kg simultaneously.Therefore, it is big from anharmonic ratio that airborne remote sensing has a carrying with inertially stabilized platform, the demanding characteristics of lasting accuracy.

Lasting accuracy is one of the key technical indexes of inertially stabilized platform, has reflected the inhibition ability of stable platform to disturbance torque.The disturbance torque of platform mainly comprises unbalanced moments, moment of friction, and control system generally realizes the effective inhibition to various disturbance torques through FEEDBACK CONTROL.Control system can characterize with moment rigidity the inhibition ability of disturbance torque, and moment rigidity is big more, and control system is strong more to the inhibition ability of disturbance torque, and the lasting accuracy of platform is high more.Can improve moment rigidity through the open-loop gain that improves control system; Yet the increase that the open-loop gain of control system can not be unlimited; And the increase open-loop gain can cause the stability margin of system to descend; Strengthen the design difficulty of control system, so the moment rigidity of platform is a finite value, excessive disturbance torque can make platform can't satisfy the requirement of lasting accuracy.

Because factors such as mismachining tolerance; Generally all there is mass eccentricity in inertially stabilized platform; Conventional solution is to overcome mass eccentricity through increasing balancing weight, and unbalanced moments is limited within the very little amplitude, relies on FEEDBACK CONTROL promptly to satisfy the requirement of platform stable precision.Yet airborne remote sensing need be carried multiple load with inertially stabilized platform, and the centroid position of different loads is different, and barycenter can be moved in the course of the work, is difficult to overcome mass eccentricity through the mode of counterweight.Because platform bearer under the effect of acceleration of gravity and aircraft disturbing acceleration, produces bigger unbalanced moments than big, cause the lasting accuracy of platform to descend, can't satisfy the requirement of platform stable precision through the method that improves control system moment rigidity.

Summary of the invention

Technology of the present invention is dealt with problems and is: overcome conventional FEEDBACK CONTROL suppresses scarce capacity to the bigger unbalanced moments of amplitude defective; Provide a kind of unbalanced moment of aerial remote sensing inertially stabilized platform to estimate and compensation method, reduce requirement platform moment rigidity.

Technical solution of the present invention is: a kind of unbalanced moment of aerial remote sensing inertially stabilized platform estimates and compensation method that concrete steps are following:

(1) adopts the mems accelerometer be installed on the airborne remote sensing inertial platform to measure to be applied to sky on the platform framework to real time acceleration information, comprised gravity acceleration g and acceleration of motion a to real time acceleration information in said day;

(2) adopt Hall current sensor to measure the electric current I that is installed in the torque motor on the framework; Through low-pass filter the torque motor electric current I is carried out filtering, obtain average current

(3) according to the acceleration information and the torque motor average current that obtain in step (1) and the step (2) Estimate the unbalanced moments M of platform _Esti, $M_{\mathrm{Esti}}=K_T\·\tilde{I}\·\frac{g+a}{g},$ K wherein _TBe the torque motor moment coefficient;

(4) with the unbalanced moments M that obtains in the step (3) _EstiDivided by torque motor moment coefficient K _T, obtain being used to compensate the needed electric current I of unbalanced moments _Comp

(5) with the I that obtains in the step (4) _CompCompensate on torque motor electric current loop given;

(6) periodic repeating step (1)～(5).

The principle of invention is: inertially stabilized platform is followed the tracks of local level, and under stable situation, control system is through the effect of close-loop feedback, and the output of control moment motor equates with disturbance torque, opposing torque in the opposite direction.The torque and the proportional M of armature supply of torque motor output _m=K _TI can obtain

K _T·I＝M _eg+M _ea+M _f

①

In the formula, K _TBe torque motor moment coefficient, M _EgBe the unbalanced moments component of platform at acceleration of gravity effect underframe, M _EaBe the unbalanced moments component of platform at airplane motion disturbing acceleration effect underframe, M _fBe moment of friction.

Because air turbulence is a stochastic process, and its average is zero, all can be considered white noise so the unbalanced moments component of airplane motion disturbing acceleration effect underframe, moment of friction and counter electromotive force of motor disturb.So, can obtain the unbalanced moments component that framework only produces under the gravity acceleration g effect through the armature electric current is carried out the Butterworth LPF:

$K_T\·\tilde{I}=M_{\mathrm{eg}}=m\·g\·l_e$

In the formula, K _TBe the torque motor moment coefficient,

Be filtered armature electric current, M _EgBe the unbalanced moments component of platform at acceleration of gravity effect underframe, m is the framework quality, l _eMass eccentricity distance for framework.

Gravity acceleration g and airplane motion disturbing acceleration a can be obtained by accelerometer measures, and then the computing formula in the unbalanced moments of the acting in conjunction underframe of acceleration of gravity and airplane motion disturbing acceleration is:

M _esti＝m(g+a)l _e ③

2. can get the mass eccentricity distance by formula $l_e=\frac{K_T\·\tilde{I}}{m\·g},$ And the estimate equation that 3. the substitution formula obtains the framework unbalanced moments does

$M_{\mathrm{esti}}=K_T\&CenterDot;\tilde{I}\&CenterDot;\frac{g+\mathrm{<figure-callout\; id="4"\; label="a\; g"\; filenames="H2009102412429E00021.png"\; state="\{\{state\}\}">a</figure-callout>}}{g}$ ④

Estimate unbalanced moments M _EstiAfter, be M in the input end of torque motor electric current loop compensation size _Esti/ K _TThe given signal of electric current, electric current loop output and M _EstiEqual and opposite in direction, compensating torque in the opposite direction, thus realize effective inhibition that unbalanced moments is disturbed, improve the lasting accuracy of platform.

The present invention's advantage compared with prior art is: through the real-time unbalanced moments that estimates stable platform; Control compensation then feedovers in control system; Thereby good restraining the stable platform unbalanced moments disturb; Reduction improves the lasting accuracy and the stability margin of stable platform to the requirement of stable platform control system moment rigidity.

Description of drawings

Fig. 1 is an implementation step synoptic diagram of the present invention;

Fig. 2 for airborne remote sensing with three inertially stabilized platform structural representations;

Fig. 3 is for using the roll frame and the pitching frame control system transport function block diagram of airborne remote sensing inertially stabilized platform of the present invention;

Fig. 4 is the mems accelerometer schematic diagram;

Fig. 5 is Hall current sensor and signal conditioning circuit thereof;

Fig. 6 is the ADC part schematic diagram of TMS320F28335;

Fig. 7 does not adopt the angular speed output of inertially stabilized platform of the present invention under the unbalanced moments effect when being MATLAB emulation;

Fig. 8 has adopted the angular speed output of inertially stabilized platform of the present invention under the unbalanced moments effect when being MATLAB emulation.

Embodiment

Inertially stabilized platform and POS (position, attitude measurement system) collaborative work can be regarded as an angle positional servosystem.POS is installed on the platform, resolves and export attitude information, and this attitude error angle can be regarded the feedback information of platform attitude as.As shown in Figure 2, the airborne remote sensing inertially stabilized platform is respectively roll frame, pitching frame and orientation frame from outside to inside, and the roll frame is around the rotation of X axle, and the pitching frame is around the rotation of Y axle, and the orientation frame rotates around the Z axle.Roll frame, pitching frame are followed the tracks of local geographical level, and the orientation frame is followed the tracks of and carried the machine course, and the control system of three frameworks is relatively independent.The present invention only is applied to roll frame and pitching frame, and the orientation frame is inapplicable.Remote sensing load and POS are installed on the orientation frame, and mems accelerometer is installed on the stable platform orientation frame, and its sensitive axes is perpendicular to local level.Among the figure, G _x, G _y, G _zFor being installed in the rate gyro on each framework, M _x, M _y, M _zBe three torque motors, M _xBe installed on the pedestal M _yBe installed on the roll frame M _zBe installed on the pitching frame K _x, K _y, K _zServo controller for each framework.Servo controller produces control signal to torque motor according to attitude and the positional information that fast frame corners rate information and POS provide, and torque motor output drive strength square rotates to offset disturbance torque and to drive framework, reaches purpose stable and that follow the tracks of.

Used airborne remote sensing inertially stabilized platform roll frame of the present invention, pitching frame control system transport function block diagram is as shown in Figure 3.Be respectively electric current loop, stable loop, tracking loop from inside to outside.Electric current loop is used to accelerate the torque motor torque responsing speed, suppresses the counter electromotive force of motor disturbance simultaneously; Stable loop is used to provide rate damping, improves the stability and the response speed to disturbing of system; Tracking loop is used to be adjusted to the accurate sensing of the picture load optical axis, follows the tracks of local geographical level and carries the machine course.Among the figure, θ _InFor framework is given with respect to the position, angle of local level, and θ _In=0, θ _OutBe the angle position output of framework with respect to local level; ω _InFor frame corners speed given; ω _OutBe the output of frame corners speed; I _InFor the torque motor electric current given; I _OutBe the output of torque motor electric current; K _TBe the torque motor moment coefficient; J is the framework rotator inertia that comprises load; M _eBe unbalanced moments; M _fBe moment of friction; K _eω is a motor reaction gesture, and wherein ω is a motor speed, K _eBe the counter electromotive force of motor coefficient;

Be current controller, wherein, K _eBe current controller scale-up factor, τ _cBe the current controller time constant, s complex operation operator; Be the transport function of pwm power driver element, wherein U is the motor-driven supply voltage, T _PwmBe the PWM cycle;

Be armature winding transport function, wherein T _eBe motor electromagnetic time constant, K _mBe the current of electric coefficient; Be rate controller, wherein K _cBe rate controller scale-up factor, τ _cBe the current controller time constant;

Be the transport function of rate gyro, wherein T _GBe the rate gyro time constant.Control system is adopted the digital servo control technology, and various algorithms are all realized with digital form in TMS320F28335 inside.

As shown in Figure 4, the present invention uses the acceleration of mems accelerometer MMA7261 sensitive platforms vertical, and the 0g output voltage of MMA7261 is 1.65V among the figure, and sensitivity is 480mV/g, and measurement range is-2.5g ~+2.5g.The ADCB5 pin that is input to the TMS320F28335 among Fig. 6 after MMAX7261 process dividing potential drop, the filtering carries out the A/D conversion.

As shown in Figure 5; The present invention uses Hall current sensor TBC25C04 to be connected in the motor circuit; TBC25C04 exports the current signal I_SENSE_M1 that is directly proportional with current of electric I with 1: 500 relation; Convert voltage signal (1.024+0.05I) V to through signal processing circuit, and be transported to TMS320F28335 and carry out the A/D conversion.

For the effect that proves that this is bright, carried out MATLAB emulation.Simulation parameter is made as: the amplitude of moment of friction is 0.3Nm, and the amplitude that back electromotive force disturbs is 1V, and the amplitude of airplane motion disturbing acceleration a is that 1g, frequency are 1Hz, the cutoff frequency ω of Butterworth low-pass filter _cBe 0.1Hz, the mass eccentricity of framework is apart from being 1cm, and the framework quality is 120Kg, and then under the airplane motion disturbing acceleration effect of acceleration of gravity and alternation, the expression formula of unbalanced moments is (11.76+11.76sin (1t)) Nm.Fig. 7 is the angular speed output of not using inertially stabilized platform of the present invention; Fig. 8 is the angular speed output of having used inertially stabilized platform of the present invention; After can finding out use the present invention, platform is increased dramatically to the inhibition ability of unbalanced moments, and platform can obtain higher lasting accuracy.

Practical implementation method of the present invention is following:

1, inertially stabilized platform powers on, and control system is started working;

2, use the mems accelerometer MMA7261 be installed on the platform to measure to be applied to comprise gravity acceleration g and acceleration of motion a on the platform framework the sky to real time acceleration; The transport function of mems accelerometer is that first order inertial loop

accelerometer signal modulate circuit degree of will speed up meter output signal carries out filtering, dividing potential drop, voltage range is moved in the A/D conversion input voltage range of 0 ~ 3V.A/D converts this voltage signal into digital quantity and sends digitial controller to, thereby obtains the platform sky to real time acceleration g+a.；

3, Hall current sensor TBC25C04 is connected in the respective frame torque motor circuit; The current signal that output is directly proportional with the electric current I of torque motor; After carrying out signal condition and A/D conversion, in digitial controller, use two rank Butterworth low-pass filters that the torque motor electric current I is carried out filtering and obtain average current

The transport function of the two rank Butterworth low-pass filters that use does

ω wherein _cBe cutoff frequency, ω _c=0.1;

4, according to the acceleration information g+a and the torque motor average current that obtain Calculate the unbalanced moments M of platform _Esti, computing formula does $M_{\mathrm{Esti}}=K_T\&CenterDot;\tilde{I}\&CenterDot;\frac{g+a}{g},$ K wherein _TBe the torque motor moment coefficient;

5, with the unbalanced moments M that obtains _EstiDivided by torque motor moment coefficient K _T, obtain being used to compensate the needed electric current I of unbalanced moments _Comp

6, with the offset current I that obtains _CompOutput I with stable loop _InAfter the addition as the given electric current loop that is input to of electric current loop, thereby electric current loop through the current drives motor of the corresponding size of closed-loop corrected output, the needed torque of motor output opposing unbalanced moments.

7, periodic repeating step 2 ~ 6 can estimate unbalanced moments after system's convergence is stable and also compensate automatically.

The content of not doing in the instructions of the present invention to describe in detail belongs to this area professional and technical personnel's known prior art.

Claims (1)

1. a unbalanced moment of aerial remote sensing inertially stabilized platform is estimated and compensation method, it is characterized in that step is following:

(1) adopt the mems accelerometer be installed on the airborne remote sensing inertial platform to measure to be applied to sky on the platform framework to real time acceleration information, said day to real time acceleration information comprise gravity acceleration g with day to acceleration of motion a;

(2) adopt Hall current sensor to measure the electric current I that is installed in the torque motor on the framework; Through low-pass filter the torque motor electric current I is carried out filtering, obtain average current

(3) according to the acceleration information and the torque motor average current that obtain in step (1) and the step (2)

Estimate the unbalanced moments M of platform _Esti, $M_{\mathrm{Esti}}=K_T\&CenterDot;\tilde{I}\&CenterDot;\frac{g+a}{g},$ K wherein _TBe the torque motor moment coefficient;

(4) with the unbalanced moments M that obtains in the step (3) _EstiDivided by torque motor moment coefficient K _T, obtain being used to compensate the needed electric current I of unbalanced moments _Comp

(5) with the I that obtains in the step (4) _CompCompensate on torque motor electric current loop given;

(6) periodic repeating step (1)～(5).

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