Multi-frame photoelectric platform outer ring speed feedback method

Abstract

According to the multi-frame photoelectric platform outer ring speed feedback method provided by the invention, a method of adding a state observer on an outer ring is adopted, a Smith state observer is added in an outer ring control loop, and the speed information of an outer ring frame can be observed through calculation of the observer, so that a speed measuring machine is replaced, the system hardware complexity is reduced, and in the aspect of speed feedback, the speed feedback efficiency is improved. Compared with a speed measuring machine, the state observation method can reduce the phase lag of the feedback rate and improve the stability of the system.

Description

Technical Field

[0001] The present invention belongs to the field of automatic control, and mainly relates to an observation method for outer loop speed feedback information of a multi-frame photoelectric platform, and in particular to an outer loop frame speed feedback method of a multi-frame photoelectric platform without a speed measuring device. Background Art

[0002] An optoelectronic stabilized platform is a platform installed on a certain platform and used to detect, identify and track targets, and provide target images and relative motion information. It generally uses a rate gyroscope as an angular velocity sensitive element. Through speed closed-loop control, it isolates the angular disturbance caused by the projectile to the optoelectronic platform and ensures the stability of the aiming line in the inertial space.

[0003] The control loop of the traditional multi-frame optoelectronic stabilized platform servo system includes the inner azimuth / inner pitch stabilization control loop, the inner azimuth / inner pitch position control loop, the outer azimuth / outer pitch velocity control loop, the outer azimuth / outer pitch position control loop and the feedforward control loop. The stabilization control loop realizes the closed-loop speed stabilization control of the inner frame through gyro feedback; the velocity control loop realizes the closed-loop speed control of the outer frame by obtaining the velocity signal through the differential of the angle sensor; four angle sensors (one for each axis) are used for position measurement, and the servo control board is used to calculate the sighting line angle in real time and realize the closed-loop position control of each frame; the inner frame has a small load and is directly driven by a torque motor; the outer frame has a large load and is driven by a servo motor with a gear transmission mechanism.

[0004] By searching domestic and foreign patents and articles, we found that Lv Hongyu et al. of the North China Institute of Optoelectronic Technology published "Analysis of the Stabilization Principle of a Two-Axis Four-Frame Airborne Optoelectronic Platform", which uses the inner frame angular rate feedback to form a closed loop of the stabilization loop, which can improve the stability accuracy of the inner loop; Chinese patent CN111338391 "A Two-Axis Four-Frame Optoelectronic Turntable Control System" discloses a two-axis four-frame optoelectronic turntable control system with a similar idea, which uses the inner loop stabilization loop of angular rate gyro feedback to improve the stability accuracy of the platform. It can be seen that the existing effective methods for improving the stability accuracy of multi-frame stabilization systems are to add a control link to the inner loop or form a feedback loop in the inner loop, and the outer loop uses a servo motor as the actuator of the outer loop and a tachometer as the speed feedback device. The tachometer increases the complexity and cost of the system. In some applications, the tachometer cannot be used because the outer loop motor uses a DC motor, and the angle differential method is used to obtain the speed. However, the speed signal obtained in this way has large noise and serious phase lag.

[0005] Therefore, we urgently need to propose a new method. Without using a tachometer, we can use the characteristics of the Smith state observer to observe the system interference signal to obtain the observed position and observed speed of the system. This method can obtain an outer loop speed signal with low noise and small phase lag, which can meet the application of the two-axis four-frame system. Summary of the invention

[0006] In view of the problems of high hardware complexity and rate feedback lag in the existing methods, the present invention proposes a multi-frame optoelectronic platform outer-loop speed feedback method. On the basis of the basic position-speed loop control, the speed information output by the speed state observation module is used as the input of the outer-loop speed control loop. The state observation module utilizes the Smith state observer characteristics to obtain the observed position and observed speed of the system, that is, the position estimation information and the speed estimation information, by observing the system interference signal.

[0007] The present invention proposes a multi-frame optoelectronic platform outer loop speed feedback method, which is characterized by comprising the following steps:

[0008] Step 1: Calculate the error S between the actual position and the observed position e ;

[0009] Step 2: Calculate the system disturbance torque T d ;

[0010] Step 3: Calculate the motor torque T M ;

[0011] Step 4: Calculate the total system torque T l ;

[0012] Step 5: Calculate the observed velocity ω l , which is the estimated value of speed;

[0013] Step 6: Calculate the position estimate S l , update the observation position of the state observation module;

[0014] Step 7: Substitute the estimated velocity value ω calculated in step 5 l As the feedback input of the outer loop speed feedback loop, it participates in the outer loop speed control calculation and completes the outer loop speed stability control of the multi-frame platform system.

[0015] Furthermore, the error S between the actual position and the observed position in step 1 is e for:

[0016] S e =SS l

[0017] Where: S is the current actual position of the system after measuring gain, filtering and measuring noise through the angle sensor output; S l The current observation position is the last position output of the state observation module.

[0018] Furthermore, the system disturbance torque T in step 2 d for:

[0019] T d =S e K0

[0020] Where: K0 is the gain value of the observer.

[0021] Furthermore, in step 3, the motor torque T M for:

[0022] T M =i q ·K T

[0023] Where: i q is the output current; K T is the motor torque coefficient.

[0024] Furthermore, the total system torque T in step 4 is l is the torque of the motor torque and the disturbance torque acting on the gimbal, that is:

[0025] T l =T M +T d .

[0026] Furthermore, the observation speed ω is calculated in step 5 l The steps are:

[0027] The time domain relationship between torque and angular acceleration is:

[0028]

[0029] Where: J is the system moment of inertia; is the motor rotation angular acceleration;

[0030] Performing Laplace transform on both sides simultaneously can obtain the corresponding complex domain relationship:

[0031] Jsω l (s) = T l (s)

[0032] Where: l is the motor rotation angular velocity; s is a complex domain variable;

[0033] The actual system needs to be discretized, and the calculation formula for the observed speed after discretization is:

[0034]

[0035] Where: T is the sampling time; z is a discrete variable.

[0036] Furthermore, the position estimation value S is calculated in step 6 l The steps are:

[0037] The position in the time domain is obtained by integrating the velocity, which can be transformed into the complex domain as follows:

[0038] S l =ω l / s

[0039] The estimated position value s after discretization l for:

[0040]

[0041] Furthermore, all steps are executed cyclically according to the servo control cycle to complete the speed state observation.

[0042] The beneficial effects of the present invention are embodied in the following aspects:

[0043] 1. The present invention does not need to add a speed measuring device. When the system is powered on and initialized, the state observation module automatically runs periodically in the servo control computer. Based on the state observation and the calculation of the controller parameters, the speed feedback information can be obtained, thus saving the hardware cost.

[0044] 2. The present invention mainly focuses on multi-frame speed feedback, makes full use of the state observation theory, and designs a speed state observer. Compared with direct angle differentiation, it can effectively improve the state phase lag of speed information and reduce noise;

[0045] 3. The present invention is implemented by software, has a simple algorithm, is highly portable, and is suitable for various multi-frame photoelectric stabilization systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is the servo control schematic diagram of the traditional multi-frame optoelectronic system.

[0047] Figure 2 It is a control principle diagram of speed state observation to be realized by the present invention.

[0048] Figure 3 It is a flow chart of the speed state observation module of the present invention. DETAILED DESCRIPTION

[0049] The present invention adopts a method of adding a state observer to the outer loop. In the outer loop control loop, a Smith state observer is added. Through the calculation of the observer, the rate information of the outer loop framework can be observed, thereby replacing the tachometer and reducing the hardware complexity of the system. In terms of rate feedback, compared with the tachometer, the state observation method can reduce the phase lag of the feedback rate and improve the stability of the system.

[0050] The present invention will be further described in detail below in conjunction with the accompanying drawings and preferred embodiments.

[0051] The preferred embodiment of the present invention is a two-axis four-frame optoelectronic stabilization platform system, which includes two sensors, a visible light sensor and an infrared sensor, which are mounted on a gimbal platform to form a sensor platform. The platform is driven by a servo control unit, which includes a speed stabilization loop and a position control loop. Figure 1 The control loop of the servo system includes an inner azimuth / inner pitch stabilization control loop, an inner azimuth / inner pitch position control loop, an outer azimuth / outer pitch speed measurement control loop, an outer azimuth / outer pitch position control loop and a feedforward control loop. The stabilization control loop realizes closed-loop speed stabilization control of the inner frame through gyro feedback; the speed measurement control loop obtains the speed signal through speed state observation to realize closed-loop speed control of the outer frame; four angle sensors (one for each axis) are used for position measurement, and the servo control board is used to calculate the sighting line angle in real time and realize closed-loop position control of each frame; the inner frame is directly driven by a torque motor; the outer frame is driven by a servo motor in combination with a gear transmission mechanism.

[0052] In this preferred embodiment, the operation cycle of the speed state observation module in the servo control software is T = 0.0005s, K T =0.375, J = 0.0012 Kg·m 2 , K0=500, read the above parameters from the storage area during system initialization, and then before executing the speed observation state module, first ensure that the angle sensor receives data normally, the motor drive is normal, and the position loop controller is initialized normally. After that, the speed state observation module will follow the attached Figure 3 The software flow shown implements control. In one servo control cycle, the specific steps are as follows:

[0053] Step 1: Calculate the error S between the actual position and the observed position e .

[0054] The current actual position of the system is the system position output by the angle sensor after measuring gain, filtering and measuring noise. The actual position is recorded as S. The current observed position is the last position output of the state observation module. The observed position is recorded as S. l , then the error S between the actual position and the observed position eIt is expressed as:

[0055] S e =SS l (1)

[0056] Step 2: Calculate the system disturbance torque T d .

[0057] The error S between the actual position and the observed position calculated in step 1 e And the Smith state observer principle, the disturbance of the system can be obtained. Specifically in this system, according to the state observer gain, the disturbance torque T of the system is estimated. d :

[0058] T d =S e ·K0 (2)

[0059] Where K0 is the gain value of the observer.

[0060] Step 3: Calculate the motor torque T M .

[0061] After simplifying the system model, it can be obtained that the motor torque is proportional to the output current and can be expressed as:

[0062] T M =i q ·K T (3)

[0063] Among them, i q is the output current, K T is the motor torque coefficient.

[0064] Step 4: Calculate the total system torque T l , that is, the torque exerted on the gimbal by the motor torque and the disturbance torque.

[0065] T l =T M +T d (4)

[0066] Step 5: Calculate the observed velocity ω l , which is the estimated value of speed.

[0067] The time domain relationship between torque and angular acceleration is:

[0068]

[0069] Where J is the system moment of inertia, is the motor angular acceleration.

[0070] Performing Laplace transform on both sides simultaneously can obtain the corresponding complex domain relationship:

[0071] Jsω l (s) = T l (s) (6)

[0072] Among them, ω l is the observed velocity, and s is a complex domain variable.

[0073] However, since Formula 6 is the transfer function relationship of a continuous system, the actual system needs to be discretized. The calculation formula for the observed speed after discretization is:

[0074]

[0075] Where T is the sampling time and z is the discrete variable.

[0076] Step 6: Calculate the position estimate s l , update the observation position of the state observation module.

[0077] The position in the time domain is obtained by integrating the velocity, which can be transformed into the complex domain as follows:

[0078] S l =ω l / s (8)

[0079] After discretization, calculate the position estimate s l for:

[0080]

[0081] Step 7: Substitute the estimated velocity value ω calculated in step 5 l As the feedback input of the outer loop speed feedback loop, it participates in the outer loop speed control calculation and completes the outer loop speed stability control of the multi-frame platform system.

[0082] The above steps are executed cyclically according to the servo control cycle to complete the speed state observation.

[0083] When the outer ring motor rotates at 20 Hz and 0.5°, this method is used to obtain the outer ring speed signal with a phase error of less than 8° and a noise mean square error of less than 0.1° / s. The traditional method using position differentiation has a phase error of more than 15° and a noise mean square error of less than 0.8° / s. The speed signal obtained by the tachometer method has a phase error of more than 8° and a noise mean square error of less than 0.2° / s. Therefore, without adding hardware, this method is superior to the traditional method in both phase lag and measurement noise.

[0084] Finally, it should be noted that the features mentioned and / or shown in the above description of the exemplary embodiments of the present invention may be combined in the same or similar manner into one or more other embodiments, combined with the features in other embodiments or substituted for the corresponding features in other implementations. The technical solutions obtained by these combinations or substitutions shall also be deemed to be included in the protection scope of the present invention.

Claims

1. A multi-frame optoelectronic platform outer loop speed feedback method, characterized in that: The following steps are involved: Step 1: Calculate the error S between the actual position and the observed position e ; Step 2: Calculate the system disturbance torque T d ; Step 3: Calculate the motor torque T M ; Step 4: Calculate the total system torque T l ; Step 5: Calculate the observed velocity ω l , which is the estimated value of speed; Step 6: Calculate the position estimate S l , update the observation position of the state observation module; Step 7: Substitute the estimated velocity value ω calculated in step 5 l As the feedback input of the outer loop speed feedback loop, it participates in the outer loop speed control calculation and completes the outer loop speed stability control of the multi-frame platform system.

2. A multi-frame optoelectronic platform outer loop speed feedback method as claimed in claim 1, characterized in that: The error S between the actual position and the observed position in step 1 e for: S e =S-S l Where: S is the current actual position of the system after measuring gain, filtering and measuring noise through the angle sensor output; S l The current observation position is the last position output of the state observation module.

3. A multi-frame optoelectronic platform outer loop speed feedback method as claimed in claim 1, characterized in that: In step 2, the system disturbance torque T d for: T d =S e ·K0 Where: K0 is the gain value of the observer.

4. The method for outer loop speed feedback of a multi-frame optoelectronic platform according to claim 1, characterized in that: In step 3, the motor torque T M for: T M =i q ·K T Where: i q is the output current; K T is the motor torque coefficient.

5. The method for outer loop speed feedback of a multi-frame optoelectronic platform according to claim 1, characterized in that: The total system torque T in step 4 l is the torque of the motor torque and the disturbance torque acting on the gimbal, that is: T l =T M +T d 。 6. The method for outer loop speed feedback of a multi-frame optoelectronic platform according to claim 1, characterized in that: The observation speed ω is calculated in step 5 l The steps are: The time domain relationship between torque and angular acceleration is: Where: J is the system moment of inertia; is the motor rotation angular acceleration; Performing Laplace transform on both sides simultaneously can obtain the corresponding complex domain relationship: Jsω l (s)=T l (s) Where: l is the motor rotation angular velocity; s is a complex domain variable; The actual system needs to be discretized, and the calculation formula for the observed speed after discretization is: Where: T is the sampling time; z is a discrete variable.

7. The method for outer loop speed feedback of a multi-frame optoelectronic platform according to claim 1, characterized in that: In step 6, the position estimate value S is calculated. l The steps are: The position in the time domain is obtained by integrating the velocity, which can be transformed into the complex domain as follows: S l =ω l / s The estimated position value s after discretization l for:

8. The method for outer loop speed feedback of a multi-frame optoelectronic platform according to claim 1, characterized in that: All steps are executed in a servo control cycle to complete the speed state observation.

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