CN106950980B - A kind of small-sized fixed-wing unmanned plane guidance computer and method of guidance - Google Patents

Abstract

The invention discloses a kind of small-sized fixed-wing unmanned plane guidance computer and method of guidance, belong to UAV Flight Control technical field.Guidance computer of the invention is made of power panel and control signal-processing board: power panel includes power converting circuit module, analog reference voltage module；Controlling signal-processing board includes IO drive module, analog signal conditioner module, digital signal conditioning module and CPU module.Method of guidance of the invention can be compatible with Passing zenith tracing and spacing tracks two kinds of tracing modes, and Passing zenith tracing and spacing homing guidance method use unified form, only realize two kinds of homing guidance modes by sending the instruction of some variate-value.The present invention can both automatically switch the tracing mode of unmanned plane according to the change of ground movement speed, its tracing mode can also be artificially controlled according to telecommand, improve tracking efficiency and ensure safety when unmanned plane switches tracing mode.

Description

A small fixed-wing unmanned aerial vehicle guidance computer and guidance method

technical field

The invention discloses a guidance computer and a guidance method for a small fixed-wing unmanned aerial vehicle, belonging to the technical field of unmanned aerial vehicle flight control.

Background technique

UAV technology has achieved rapid development in the past few decades, and has a very wide range of application prospects in military and civilian fields. In these applications, tracking ground targets is the most basic but challenging task. At the same time, the motion control of UAV has become a key part of the target tracking system. Generally, tracking modes can be divided into two categories: overhead tracking and fixed-distance tracking. Overhead tracking is a tracking mode used by UAVs to periodically fly over targets. This tracking mode can closely track fast-moving ground targets, but there is a risk of being exposed. Fixed-distance tracking is a tracking mode in which the UAV keeps a certain distance from the ground target. The advantage of fixed-distance tracking is that the UAV can track the ground target without being detected by it. Suitable for tracking low-speed targets. In the past guidance method design, the guidance method design of these two tracking modes is generally separated and their stability is analyzed separately. If the combination of overhead tracking and fixed-distance tracking is used, it is of great practical significance to design a unified form of guidance method, which combines the advantages of the two tracking modes and overcomes the shortcomings of both.

Contents of the invention

In order to overcome the shortcomings of overhead tracking and fixed-distance tracking in the prior art and combine the advantages of both, the present invention provides a small-sized fixed-wing unmanned aerial vehicle guidance computer and guidance method. Under the framework, the two-dimensional kinematics model of the UAV and the ground target is established, and the vector change and position relationship in the overhead tracking and fixed-distance tracking modes are respectively analyzed, and a unified guidance method is designed, which satisfies the requirements of both tracking modes. Constraints such as the minimum turning radius, analysis of the stability of the two tracking modes in tracking stationary and moving targets, combined with semi-physical simulation results show that the UAV can switch between the two tracking modes to track ground targets.

The present invention adopts following technical scheme for solving its technical problem:

A small-sized fixed-wing unmanned aerial vehicle guidance computer comprises a power board and a control signal processing board, the power board includes a power conversion circuit module and an analog reference voltage module, and the control signal processing board includes an IO drive module and an analog signal conditioning module , a digital signal conditioning module and a CPU module; the power conversion circuit module outputs digital power to supply power to each module of the control signal processing board, and the analog signal conditioning module and the digital signal conditioning module perform information interaction with the CPU module through the IO driver module respectively.

This method is compatible with two tracking modes: overhead tracking and fixed-distance tracking, and includes the following steps:

(1) When the tracking target is a cooperative object, the position and course information of the UAV and the ground target can be obtained through the communication link between the UAV and the ground target; when the tracking target is a non-cooperative object, the information can be obtained through the target indication system Position and heading information of drones and ground targets;

(2) According to the position and motion state of the UAV and the ground target under the two-dimensional Frenet-Serret framework, define the value range and direction of each state quantity, and establish the two-dimensional kinematics model of the UAV and the tracking target;

(3) In the two-dimensional kinematics model established, the tracking mode of the UAV tracking the ground target is determined according to a variable value, and the variable relationship in the two tracking modes is analyzed respectively;

(4) Design a unified form of guidance method under two tracking modes, and analyze its stability.

The position and course information of the UAV and the ground target in step (1) includes the UAV position [x _u , y _u ] ^T and the UAV heading angle ψ _u , the position of the ground target [x _t , y _t ] ^T and the ground target heading angle ψ _t .

The position and motion state of the UAV and the ground target described in step (2) under the two-dimensional Frenet-Serret framework, the two-dimensional kinematics model of the UAV tracking the ground target at a fixed distance is expressed as:

where r is the relative distance between the UAV and the ground target, v _u and v _t are the speeds of the UAV and the ground target respectively, is the heading angular velocity of the UAV, is the rate of change of the angle between the preset circle tangent and the line of sight under fixed-distance tracking, is the relative distance change rate between the UAV and the ground target; χ is the angle between the current UAV heading and the expected heading, and χ∈(-π,π] is positive counterclockwise, that is is the desired heading angle of the UAV; is the rate of change of χ angle; when the UAV is in the fixed-distance tracking mode and is outside the preset tracking circle, σ _d is the angle between the tangent of the preset circle and the line of sight, there is σ _d and r _d is the expected distance of the UAV hovering under fixed-distance tracking, given when the UAV is within the preset circle σ _m is the angle between the desired heading and the preset circle tangent direction.

The position and motion state of the UAV and the ground target described in step (2) under the two-dimensional Frenet-Serret framework, the two-dimensional kinematics model of the UAV tracking the ground target over the top is expressed as:

In step (3), one of the variable values that determines the tracking mode of the UAV tracking the ground target is r _d , that is, the expected distance for the UAV to track the ground target in fixed-distance circling. When r _d ≠ 0, the tracking mode is Fixed-distance tracking; when _rd = 0, the UAV tracking mode is overhead tracking.

Described in the step (4) to the guidance method of two kinds of tracking modes design unified form, propose following unmanned aerial vehicle tracking ground target guidance method:

Among them, the guidance gain is k ₁ >0 and k ₂ <1. Within a unit time Δt, d ₁ is the distance of the UAV moving in the desired heading; d ₂ is the distance of the ground target; is the line of sight angle σ, d _r is the relative distance r between the UAV and the ground target; is the sum of line-of-sight angles σ and σ _d , for derivative with respect to time, that is angular velocity; sign is a sign function.

In step (4), the stability analysis of the designed guidance method is carried out, and the Lyapunov function is selected as: Then the derivative of the Lyapunov function can be obtained Where _k2 is the guidance gain of the guidance method, χ is the angle between the current UAV heading and the desired heading, is the derivative of χ with respect to time t.

The present invention has the following beneficial effects:

(1) It avoids the shortcomings of independent design of the two tracking modes in the past, improves the design efficiency of the UAV guidance method, and makes the guidance method have a unified form.

(2) When the UAV tracks the moving target with variable speed on the ground, its own speed remains constant.

(3) It overcomes the limitation of fixed-distance tracking on the speed of the ground target, and the speed of the tracked target can be from static to the maximum cruising speed of the UAV.

(4) The tracking mode of the UAV can be automatically switched according to the change of the ground motion speed, or the tracking mode can be manually controlled according to the remote control command, which improves the tracking efficiency and ensures the safety of the UAV when switching the tracking mode.

Description of drawings

Fig. 1 is a block diagram of the hardware architecture of the semi-physical simulation system of the present invention.

Fig. 2 is a composition diagram of the guidance computer control signal processing board of the present invention.

Fig. 3 is a schematic diagram of tracking a moving target at a fixed distance in the present invention.

Fig. 4 is a schematic diagram of overhead tracking of a moving target in the present invention.

Fig. 5 is a schematic diagram of two modes of the UAV tracking a fixed target according to the present invention.

Fig. 6 is a schematic diagram of relative distances between two modes of the UAV tracking a fixed target according to the present invention.

Fig. 7 is a schematic diagram of two modes of the UAV tracking the trajectory of a uniform moving target in the present invention.

Fig. 8 is a schematic diagram of the relative distances of two modes of the UAV tracking a uniform moving target according to the present invention.

Fig. 9 is a schematic diagram of the moving speed profile of the Levy moving target of the present invention.

Fig. 10 is a schematic diagram of two modes of the UAV tracking the trajectory of a Levy (Levy) moving target according to the present invention.

Fig. 11 is a schematic diagram of the relative distances of the tracking Levy (Levy) moving target in two modes of the drone of the present invention.

Fig. 12 is a schematic diagram of the trajectory of the UAV tracking the ground target under the semi-physical simulation system of the guidance method designed in the present invention.

Detailed ways

The invention will be described in further detail below in conjunction with the accompanying drawings.

1. Guidance computer design

The guidance computer is the core of the guidance system. The whole system consists of two boards, namely the power supply board and the control signal processing board. The whole system consists of two boards, namely the power board and the control signal processing board. The power board includes a power conversion circuit module and an analog reference voltage module. The control signal processing board includes an IO driver module, an analog signal conditioning module, a digital signal conditioning module and a CPU module. High reliability and low power consumption.

a. The module used for the guidance computer DC/DC (direct current-direct current) conversion used in the present invention is LT3972, and the 27V input voltage is converted into +5V output, and the digital circuit work is provided; the 27V input voltage is converted into 5.5V output, providing Servo power supply; convert 27V input voltage to 5V output to provide analog power. The maximum output current of LT3972 is 3A, and the working temperature is -45～+85℃.

b. The control signal processing board includes analog signal input and output, serial port, IO input and output, PWM (pulse width modulation) input and output and CPU module. Its module composition is shown in Fig. 2 . The CPU uses MPC565 to process, calculate and control the input and output information. Including 8-way 14bit DA output, 8-way 16bit AD input, 8-way isolated PWM input and 8-way PWM output. MR25H10 is Everspin's industrial-grade serial NVRAM (Non-Volatile Random Access Memory), with a capacity of 1Mb, running at a high speed of 40MHz, without write delay. MR25H10 allows unlimited erasing. The low-voltage protection circuit can automatically protect data when power is lost, and prevent data from being written when the voltage is outside the specified range. The AD7689 chip is used for analog signal sampling. AD7689 is an 8-channel, 16-bit, charge redistribution successive approximation register (SAR) analog-to-digital converter (ADC). It is powered by a single power supply VDD. AD7689 has a multi-channel, low-power data acquisition system. All components required, including: true 16-bit SAR ADC with no missing codes; 8-channel (AD7689) low-crosstalk multiplexer to configure inputs as single-ended, differential, or bipolar; Internal low-drift reference and buffer; temperature sensor; selectable single-pole filter; and sequencer useful when multiple channels are sampled sequentially.

The boot program of the guidance computer has two working modes: program loading mode and program running mode. When the 8-pin and 4-pin in the DB9 connector of the HyperTerminal host are connected, the program loading mode is run, otherwise the program running mode is run. When running the program loading mode, at first the executable program of the present invention is downloaded in the SRAM (static random access memory) of the mainboard through the XMODEM (asynchronous file transfer in serial port communication) protocol, and is saved in the FLASH on the mainboard simultaneously, and starts to execute user application. When running the user program operation mode, the boot program reads the executable program from the FLASH (flash memory) to the SRAM (static random access memory) of the motherboard, and starts to execute the user program. Operation steps: Insert the serial port connector used for user program loading into J1; write executable binary file program; open the WINDOWS hyperterminal, define the properties of the hyperterminal as 115200 bits per second, 8 data bits, parity check None and the stop bit is 1; the menu MENU appears after power-on, press the X key to select XMODEM; if the "§" symbol appears continuously on the hyperterminal, the main board is requesting the hyperterminal to send the user executable program; click the menu on the hyperterminal: Teleport -> Send File. Choose to use the XMODEM protocol, then click "Browse" to select the executable file of the program, and click Send; press R to execute the program directly.

2. Guidance method mathematical model construction

A UAV control system usually consists of a stabilization loop and a guidance loop. In the present invention, it is considered that the stabilization circuit has been designed and can respond well to the guidance instructions of the guidance circuit. Ideally, it is considered that the UAV performing the tracking task remains at a fixed height, so it can usually be simplified as a two-dimensional guidance problem, and in the present invention, the position, velocity and heading information of the UAV and the ground target are considered is known. The above information can be obtained through the communication link between the two when the tracking target is a cooperative object, and can be obtained through satellite and other investigative means when the tracking target is not a cooperative object. Note that [x _u , y _u ] ^T represents the position of the UAV, [x _t , y _t ] ^T represents the position of the ground target; v _u is the cruising speed of the UAV, and v _t is the speed of the ground target; ψ _u represents UAV heading angle and ψ _u ∈ (-π, π], ψ _t represents the ground target heading angle and ψ _t ∈ (-π, π], and their relationship is shown in Figure 3.

In Figure 3, r is the relative distance between the UAV and the ground target, r≥0 and has an upper bound. The system dynamics model designed by the present invention can be described by (1) formula:

in, is the position change rate of the UAV in the x-axis direction; is the rate of change of the position of the UAV in the y-axis direction; is the heading rate of the UAV; v _u is the cruising speed of the UAV; u is the guidance input of the UAV.

In order to analyze the relative motion relationship between the UAV and the target, it can be seen from Figure 3 that the relative distance between the UAV and the ground target point is Wherein the definition of the direction angle in the present invention is based on the x-axis as a reference, and the counterclockwise is positive and the range is (-π, π].

The two-dimensional kinematics model of the UAV tracking the ground target can be written as follows:

Where χ is the current UAV heading angle ψ _u and the desired heading angle difference, that is is the rate of change of the difference; is the distance change rate. It can be seen from Figure 3 that when the UAV is in the fixed-range tracking mode and is located outside the preset tracking circle, there is σ _d and asin(x) is an arcsine function; where σ _d is the angle between the preset circle tangent and the line of sight under fixed-distance tracking; r _d is the expected distance of the UAV hovering under fixed-distance tracking. If the UAV is within the preset circle, given is the change rate of σ _d . σ _m is the angle between d ₁ and d _r , then the angle between v _u and the direction of the connecting line r is χ+σ _m -σ _d .

It can be seen from Fig. 4 that when the UAV enters the overhead tracking mode, the point P _s is the position where the UAV meets the target after the target passes through Δt, and the unit vectors corresponding to d ₁ , d ₂ and r are respectively and σ _m is the angle between r and d ₁ , then the angle between v _u and the direction of the connecting line r is χ+σ _m . According to the course and position relationship between the UAV and the ground target, the variable relationship is analyzed, and the two-dimensional kinematics model of the UAV tracking the ground target in the overhead tracking mode can be written as follows:

Comparing Equation (2) and Equation (3), it can be seen that when tracking over the top, that is, d _r coincides with r, r _d =0, then σ _d in Equation (2) =0, then the expression of Equation (2) It can be described as formula (3), so formula (2) can be used as a unified two-dimensional kinematics model for UAV fixed-distance tracking and overhead tracking ground targets.

3. Analysis of vector relationship in the model

Drones can fly in two ways, either clockwise or counterclockwise. For the convenience of analysis, the present invention defines fixed-distance tracking and overhead tracking to only take clockwise flight, and anti-clockwise can adopt the same method to be analyzed.

Assuming that the movement direction of the ground target remains unchanged within the sampling time Δt, that is Analyzing the motion relationship between the UAV and the target in Figure 3 shows that: so From Figure 3 so at the same time, but so

therefore so where σ is defined as the line of sight angle, For fixed-distance tracking, the preset circle tangent angle; Desired heading angle for the drone. is the supplementary angle of σ _m , is the rate of change of the supplementary angle; is the rate of change of the preset circle tangent angle; is the expected angular change rate of the UAV; σ ₁ is the angle formed by d ₁ and d ₂ , where For this angle change rate.

Analyzing Figure 3 by the unit vector and relationship between and are respectively the desired heading of the UAV, the target movement and the unit velocity vector in the tangent direction between the UAV and the preset circle. It can be seen Move it to the square Expand the formula to:

Divide both sides of the above formula by d ₁ ² , then Solve the equation to get Differentiate this equation to get:

by vector relation Available in is the derivative of the desired heading tangent vector to t; is the derivative of the current heading tangent vector to t; is the normal vector of the desired velocity; is the derivative of the desired heading angle with respect to t. Substituting formula (5) into this formula can get: because and which is in to be perpendicular to the normal vector of to be perpendicular to The normal vector of . Taking the modulo square on both sides of the formula can get Further can get: Shifting to the root of this formula has According to the above formula (4), we can also get Substitute the expression for cosσ ₁ into The expression has

That is:

Choose the Lyapunov function as: k ₂ is the guidance gain, then

make which is Set k ₂ <1, then therefore and The polarity is the same, the present invention only needs to Expand the analysis to get symbolic features.

Let y(χ)=χ-k ₂ ·atanχ, then therefore y(χ) increases monotonously within the definition domain, and when χ=0, y(0)=χ−k ₂ ·atanχ| _χ=0 =0. Therefore, χ has the same polarity as χ-k ₂ ·atanχ.

4. Guidance method design

According to the conclusion of the analysis in the above-mentioned section 3, the present invention proposes as follows (7) the guidance method based on the overhead of relative distance/line-of-sight angular rate and fixed-distance tracking ground target:

The expressions of the variables in the guidance method are summarized as follows

In formula (7), σ is defined as the line-of-sight angle, and χ is the current UAV heading angle ψ _u and the expected heading angle The difference of , ψ _t represents the heading angle of the ground target. v _u is the cruising speed of the UAV, and v _t is the speed of the ground target. d ₁ and d ₂ are the moving distances of UAV, tangent point p _t and point p _s in unit time Δt respectively, and d _r is the moving distance of UAV and tangent point p _t in unit time Δt. σ _m is the angle between d ₁ and d _r . _k1 and _k2 are the guidance gains of the guidance method.

As shown in Figure 3, σ _d is the angle between the preset circle tangent and the line of sight under fixed-distance tracking. There is no such direction angle during overhead tracking, and the definition of this angle is given in the following formula (9). σ ₂ is the angle between d _r and d ₂ , the expression is shown in the above formula (8). d ₂ is the moving distance of the target within the sampling time, and d ₂ =v _t within the sampling time.

The direction angle σ _d can be summarized as follows:

Overhead tracking: σ _d ＝0

Fixed distance tracking:

In order to unify the forms of the two guidance methods, the direction angle is defined in the guidance method As shown in Figure 4, this direction angle is the line-of-sight angle during overhead tracking, and as shown in Figure 3, it is the sum of line-of-sight angles σ and _σd during fixed-distance tracking. Summarized as follows:

Overhead tracking:

Fixed distance tracking:

4.1 Kinematics analysis under stationary target

When the target is in a static state, it can be considered as a special case of the above-mentioned motion situation, that is, the target point is fixed and cannot form a triangle relationship as shown in Figure 3 and 4. Therefore, when v _t = 0 in the expression (2), we have d ₂ =0, d ₁ and d _r coincide, σ _m =0. The guidance method shown in formula (7) can be simplified as:

At the same time, the relative relationship between the UAV and the ground target can be obtained, and the variable relationship can be analyzed. The two-dimensional kinematics model (2) can be simplified as:

From the first item of formula (12), we can get, Divided into three situations:

(Ⅰ) r≥r _d

According to formula (11), at this time Divided into two situations:

a.χ≥0 means χ-k ₂ ·atanχ≥0

It can be seen but

when

when also have

b. χ<0 means χ-k ₂ ·atanχ<0

It can be seen but

when

when

(II) r<r _d and

According to formula (11), it can be seen that According to formula (9), it can be seen that but Formula (13) is rewritten as:

but

(Ⅲ)r<r _d and

but

because So χ∈[0,π]. but

a.

Because cosχ＞0, χ-k ₂ ·atanχ≥0, k ₁ >0, then

b.

It can be seen from formula (12), but And because cosχ≤0, then therefore

In summary, when the UAV tracks a stationary target at a fixed distance which is

When the UAV tracks the stationary target overhead, it can be seen from formula (9) that σ _d =0. When case (I) r≥r _d or case (III) (r<r _d and ), the proof process is similar to that of fixed-distance tracking, and similarly we can get When case (II), ie r<r _d and When , formula (13) can be rewritten as:

Depend on but which is

In summary, when the UAV tracks a stationary target overhead, it can also be proved that

Reanalysis below Several situations:

When r≥r _d , if and only if χ=0 When tracking at a fixed distance, (0,r _d ) is the only equilibrium point of the system. It is obviously impossible to maintain χ=0 in overhead tracking; when r<r _d and , since r<r _d cannot be maintained all the time, so It is also impossible to maintain; when r<r _d and , if and only if χ=0 When the UAV tracks the target overhead, χ=0 has Therefore, it is also impossible to maintain The UAV tracks the target at a fixed distance, χ=0 has So χ=0 cannot be maintained, and it cannot be maintained forever In summary, it can be concluded that the UAV is stable in both tracking modes when tracking a stationary target.

4.2 Kinematics analysis under moving target

(Ⅰ) r≥r _d

According to formula (7) we know

a.χ≥0 means χ-k ₂ ·atanχ≥0

From formula (6), we get, but

b. χ<0 means χ-k ₂ ·atanχ<0

From formula (6), we get, but

(II) r<r _d and

According to formula (4), Since r<r _d , according to formula (9), we know therefore At the same time will Substitute into formula (2) to get:

(Ⅲ)r<r _d and

According to formula (11),

a.χ≥0 means χ-k ₂ ·atanχ≥0

By formula (6) get

but So

b. χ<0 means χ-k ₂ ·atanχ<0

By formula (6) get

but So

When the UAV tracks the target overhead, then σ _d =0. When r≥r _d or (r<r _d and ), the proof is similar to the above proof process, and can also be obtained When r<r _d and Since σ _d =0 during overhead tracking, the two-dimensional kinematics model can be written as:

According to formula (4), but

Therefore, when the drone tracks a moving target at a fixed distance,

When the UAV tracks the moving target, the closed-loop system shown in formula (2) is a non-autonomous system. Similar to the case of tracking stationary targets, considering got world, It is consistent and continuous with respect to t, so the UAV is stable in both tracking modes when tracking a moving target.

5. Guidance method verification

In order to verify the effectiveness of the guidance method design method proposed by the present invention, in this section, at first create the Simulink simulation environment by Matlab tool, write the S function of the guidance method of the present invention, to static, uniform linear motion and the ground of doing variable speed Levy trajectory motion The target is simulated and verified separately and the guidance gain is improved. Finally, a real-time simulation flight verification is carried out for a six-degree-of-freedom mathematical model of a certain type of UAV.

At the beginning of the simulation, the position, heading and other parameters of the ground target and the initial point of the UAV are set as:

λ ground target position (0,0), heading 30°

λUAV position (0, -2000), heading 30°

λUAV cruise speed: 40m/s

λMaximum roll angle of UAV: 30°

λ ground target speed range: 0--30m/s

The guidance method parameters are respectively set as k ₁ =1.0, k ₂ =0.2.

5.1 Tracking stationary ground targets

Figure 5 shows the UAV overhead and fixed-distance tracking ground stationary target trajectory. It can be seen from Figure 5 that the first half is overhead tracking, and the second half is fixed-distance tracking. Figure 6 shows the relative distance of the UAV tracking the target, reflecting the smooth switching process and good stability.

5.2 Tracking ground target moving in a straight line with uniform velocity

It can be seen from Figure 7 and Figure 8 that the target 1700s before the simulation is moving in a straight line at a uniform speed, and the UAV switches between two tracking modes to track it. In the later stage, the target stationary UAV performs overhead tracking. The simulation results show that the UAV has good tracking performance whether it is tracking a fixed distance or overhead tracking a linear moving ground target.

5.3 Tracking Levy moving target

When simulating the complex motion state of the ground target, the Levy motion model can be used, and the speed of the ground target also changes in a large range. Figure 9 and Figure 10 show the velocity profile and tracking trajectory of the ground target movement respectively.

The process of tracking the Levy moving target is divided into automatic tracking based on speed and tracking based on instructions. Figure 11 shows the relative distance of the two modes of the UAV tracking the Levy moving target. 3000s before the simulation, the UAV switches the tracking mode according to the speed of the tracked ground target. When the speed of the ground moving target is less than 1/3 of the speed of the UAV, the fixed-distance tracking mode is used, otherwise the overhead tracking mode is used; simulation In the next 3000s, the UAV receives instructions to track, in the first 1500s, the UAV receives overhead tracking instructions, and in the last 1500s, it receives fixed-distance tracking instructions.

It can be seen from Figure 10 and Figure 11 that UAV can successfully track complex Levy moving ground targets. Even if it is to track a target in a complex motion state, the guidance method designed in this paper can successfully track the target in real time, whether it is based on the speed change of the ground target or according to the command to switch the tracking guidance method mode, and the target can be successfully tracked in real time, and the transition of the transition A good stability has been realized in the process.

6. Semi-physical simulation verification

At present, the control simulation of UAV mainly includes semi-physical simulation and full digital simulation. Compared with digital simulation, semi-physical simulation introduces some real objects in the system into the simulation circuit, which simulates the scene situation more realistically, and has practical application significance for the designed guidance method.

According to the requirements of simulation verification, build the semi-physical simulation hardware platform shown in Figure 1. The platform mainly includes: guidance computer, UAV data link simulation system and simulation computer. Among them, the guidance computer is the center of the system, and the simulation computer can exchange information with the guidance computer. The sending of the remote control instruction and the receiving of telemetry can be completed, and the flight track of the tracking target based on the guidance method of the present invention can be displayed in the track display software.

6.1 Hardware equipment:

lambda guidance computer

Lambda simulation computer

Lambda test cable

λMoxa serial card

λPC

6.2 Digital link simulation system:

Lambda Remote Control Software

Lambda measurement and control software

λ track display software

(1) The guidance computer is the core of the whole simulation system, and the whole system board is composed of two boards, namely the power board and the control signal processing board. The power board includes a power conversion circuit module and an analog reference voltage module. The control signal processing board includes an IO driver module, an analog signal conditioning module, a digital signal conditioning module and a CPU module. High reliability and low power consumption. The program downloaded by the guidance computer of the present invention is not only guidance information, but also includes inner loop control information.

(2) The UAV data link simulation system includes a remote control telemetry simulation computer and a track display computer. Two computers (PC) communicate through the UDP protocol, and the two computers are connected by a router. The remote control telemetry computer is connected with the guidance computer through the serial port and exchanges information.

(3) The simulation computer is an important part of the system, and Advantech IPC610 industrial computer is used. Calculate the mathematical model of UAV flight characteristics in real time, transplant the model established by digital simulation and download it, simulate the entire tracking process of the aircraft and simulate the actual UAV flight. The calculated flight track, attitude and other information are sent to the guidance computer through the serial port.

6.3 The semi-physical simulation process of the present invention is as follows:

(1) Fig. 1 is the composition of the simulation system of the present invention, shown respectively is the flight path display software interface and the remote control telemetry software interface and the guidance computer, the simulation computer.

(2) The boot program of the guidance computer has two working modes: program loading mode and program running mode. When the 8-pin and 4-pin in the DB9 connector of the HyperTerminal host are connected, the program loading mode is run, otherwise the program running mode is run. When running the program loading mode, at first the executable program of the present invention is downloaded in the SRAM (static random access memory) of the main board through the XMODEM (asynchronous file transfer in serial port communication) protocol, and is saved in the FLASH (flash memory) on the main board simultaneously , to start executing the user application. When running the user program operation mode, the boot program reads the executable program from the FLASH (flash memory) to the SRAM (static random access memory) of the motherboard, and starts to execute the user program. Operation steps: Insert the serial port connector used for user program loading into J1; write executable binary file program; open the WINDOWS hyperterminal, define the properties of the hyperterminal as 115200 bits per second, 8 data bits, parity check None and the stop bit is 1; the menu MENU appears after power-on, press the X key to select XMODEM; if the "§" symbol appears continuously on the hyperterminal, the main board is requesting the hyperterminal to send the user executable program; click the menu on the hyperterminal: Teleport -> Send File. Choose to use the XMODEM protocol, then click "Browse" to select the executable file of the program, and click Send; press R to execute the program directly.

(3) Set up the UDP anchor address and port configuration files of the remote control telemetry software and track display software. Use the TCP/UDP test tool to ensure that the two computers can directly communicate normally. The simulation computer performs physical simulation and sends the result to the guidance computer through the serial port. Furthermore, the guidance computer sends the data to the remote control telemetering computer through the serial port. The remote control telemetry computer sends the simulated data to the track display computer through the UDP protocol and displays the UAV tracking flight track on the display device. At the same time, the data is sent to the simulation computer through the guidance computer.

(4) Fig. 12 is the track of the UAV tracking the ground target in the semi-physical simulation system according to the guidance method designed in the present invention. It can be seen that the UAV shows good performance when tracking the complex moving target on the ground.

The above is only the preferred implementation mode of the present invention. It should be pointed out that for those of ordinary skill in the art, some improvements can be made without departing from the principle of the present invention, and these improvements should also be regarded as the present invention. protection scope of the invention.

Claims (3)

1. a kind of guidance method of small-sized fixed-wing unmanned aerial vehicle guidance computer, the guidance computer that this guidance method adopts comprises power supply board and control signal processing board, and described power supply board comprises power conversion circuit module and analog reference voltage module, and described control The signal processing board includes an IO drive module, an analog signal conditioning module, a digital signal conditioning module, and a CPU module; the power conversion circuit module outputs digital power to supply power to each module of the control signal processing board, and the analog signal conditioning module and the digital signal conditioning module pass through the IO The driver module exchanges information with the CPU module; It is characterized in that the guidance method is compatible with two tracking modes: overhead tracking and fixed-distance tracking, and includes the following steps: (1) When the tracking target is a cooperative object, the position and course information of the UAV and the ground target can be obtained through the communication link between the UAV and the ground target; when the tracking target is a non-cooperative object, the information can be obtained through the target indication system The position and heading information of the UAV and the ground target; the position and heading information of the UAV and the ground target include the position [x _u , y _u ] ^T of the UAV, the heading angle ψ _u of the UAV, and the ground target The position [x _t ,y _t ] ^T and the heading angle of the ground target ψ _t ; (2) According to the position and motion state of the UAV and the ground target under the two-dimensional Frenet-Serret framework, define the value range and direction of each state quantity, and establish the two-dimensional kinematic model of the UAV and the ground target; The two-dimensional kinematics model of the UAV tracking the ground target at a fixed distance is expressed as: where r is the relative distance between the UAV and the ground target, v _u and v _t are the speeds of the UAV and the ground target respectively, is the heading angular velocity of the UAV, is the rate of change of the angle between the preset circle tangent and the line of sight under fixed-distance tracking, is the relative distance change rate between the UAV and the ground target; χ is the angle between the current UAV heading and the expected heading, and χ∈(-π,π] is positive counterclockwise, that is is the desired heading angle of the UAV; is the rate of change of χ angle; when the UAV is in the fixed-distance tracking mode and is outside the preset tracking circle, σ _d is the angle between the tangent of the preset circle and the line of sight, there is σ _d and r _d is the expected distance of the UAV hovering under fixed-distance tracking, given when the UAV is within the preset circle σ _m is the angle between the desired heading and the preset circle tangent direction; (3) In the two-dimensional kinematics model established, the tracking mode of the UAV tracking the ground target is determined according to a variable value, and the variable relationship in the two tracking modes is analyzed respectively; it is determined that the UAV tracking the ground target A variable value of the tracking mode is r _d , that is, the expected distance for the UAV to track the ground target at a fixed distance. When r _d ≠ 0, the UAV tracking mode is fixed-distance tracking; when r _d = 0, Then the UAV tracking mode is overhead tracking; (4) Design a unified form of guidance method under two tracking modes, and analyze its stability; propose the following guidance method for UAV tracking ground targets: Among them, the guidance gain is k ₁ >0 and k ₂ <1. Within a unit time Δt, d ₁ is the distance of the UAV moving in the desired heading; d ₂ is the distance of the ground target; is the line of sight angle σ, d _r is the relative distance r between the UAV and the ground target; is the sum of line-of-sight angles σ and σ _d , for derivative with respect to time, that is The angular velocity; sign is a sign function. 2. the guidance method of a kind of small-sized fixed-wing unmanned aerial vehicle guidance computer according to claim 1, is characterized in that: the unmanned aerial vehicle described in the step (2) and ground target under two-dimensional Frenet-Serret framework Position and motion state, the two-dimensional kinematics model of the UAV tracking the ground target over the top is expressed as: 3. the guidance method of a kind of small-sized fixed-wing unmanned aerial vehicle guidance computer according to claim 2, it is characterized in that: in step (4), the guidance method of design is carried out stability analysis, by choosing Lyapunov function as: Then the derivative of the Lyapunov function can be obtained Where _k2 is the guidance gain of the guidance method, χ is the angle between the current UAV heading and the desired heading, is the derivative of χ with respect to time t.