Flight management computer frequency characteristic model construction method based on Simulink

Abstract

The invention discloses a method for constructing a frequency characteristic model of a flight management computer based on Simulink. The method comprises the following steps: step 1, constructing frequency characteristic models with different execution rates; 2, building an unmanned aerial vehicle flight management computer model by using Simulink; 3, combining the frequency characteristic model with the flight control computer model, and carrying out partitioning according to functions; and step 4, carrying out joint test on the FMU (Function Mock-up Unit) after packaging the physical model of the unmanned aerial vehicle and the frequency characteristic model of the flight management computer after partitioning. Comprehensive simulation of embedded system hardware (a flight management computer), embedded system software (a flight control law) and a flight dynamics system is achieved, feature attributes such as flight management computer program execution time, a thread cycle and a task scheduling sequence are considered in a virtual flight test, the confidence coefficient of flight simulation of the unmanned aerial vehicle is further increased, and the flight simulation efficiency of the unmanned aerial vehicle is improved. The method can be used for designing and optimizing flight control laws and flight management computer hardware systems.

Description

Technical Field

[0001] The invention relates to a modeling and simulation scheme for the frequency characteristics of a flight tube computer, and in particular to a method for constructing a frequency characteristics model of a flight tube computer based on Simulink. Background Art

[0002] The UAV flight control computer system is the brain of the UAV, responsible for processing various information and instructions during flight to ensure the stable flight and mission execution of the UAV. The navigation function of the UAV determines the precise position and altitude of the UAV through sensors, and plans the flight path of the UAV according to the mission requirements. The attitude control of the UAV adopts feedforward control FF (-D) and PI control. According to the target pitch angle and roll angle, the aileron, elevator, and rudder control values ​​are solved to achieve the UAV climbing, descending, turning and other actions. The UAV can always control the pitch angle and throttle based on the target altitude and speed, and realize the energy conversion of the UAV kinetic energy and potential energy through the coordinated control of the throttle and pitch angle. In addition, the UAV flight control computer also contains other embedded systems and fault detection sensors, etc. The execution rate of these systems also indirectly affects the operating efficiency of the flight control computer. Therefore, the execution frequency characteristics of these software and hardware should also be considered during the flight of the UAV. However, the simulation of the UAV flight control computer model in the field of flight control simulation does not involve the influence of the relevant frequency characteristic model on the simulation, resulting in its simulation results not being very close to reality. Therefore, adding the flight tube computer frequency characteristic model is of great significance to the development of UAVs. However, the application of the flight tube computer frequency characteristic model is still blank. Summary of the invention

[0003] In order to solve the above-mentioned problems, the present invention provides a method for constructing a frequency characteristic model of a flight tube computer based on Simulink. By introducing a small frame counter, an enable signal with different frequencies (80Hz, 40Hz and 20Hz) is realized, and the signal controls the execution of each functional module, thereby improving the confidence of the UAV simulation.

[0004] The present invention provides a method for constructing a flight tube computer frequency characteristic model based on Simulink, comprising the following steps:

[0005] Step 1: frequency enable signals of different rates are realized by introducing a small frame counter and input into the flight control computer, and then the execution of each functional module in the flight control computer is controlled by different frequency enable signals, wherein the enable signals include three frequencies of 80 Hz, 40 Hz and 20 Hz;

[0006] Step 2: Build a flight control computer model in the Simulink model. The flight control computer model includes a fixed-wing L1 navigation law model, a fixed-wing total energy controller model, and a fixed-wing attitude controller model to achieve control of the UAV's guidance, total energy, and attitude.

[0007] Step three, combining the flight tube computer model with the frequency characteristic model to form a flight tube computer frequency characteristic model, and dividing the flight tube computer frequency characteristic model according to function, the flight tube computer frequency characteristic model consists of five partitions, the first partition performs input processing, the second partition performs equipment monitoring and signal voting and monitoring, the third partition performs automatic guidance solution, the fourth partition performs three-axis attitude control, and the fifth partition performs output processing and emergency fault processing, wherein the fifth partition is an emergency fault processing module, the second partition is an equipment monitoring module, the third partition and the fourth partition are flight tube computer modules, the emergency fault processing module execution rate is 20Hz, the equipment monitoring module execution rate is 40Hz, and the execution rates of the remaining modules are all 80Hz;

[0008] Step 4: Encapsulate the UAV physical model into FMU, and conduct a joint simulation test on the FMU and flight tube computer frequency characteristic model in the UAV automatic landing scenario and the flight tube computer under delay conditions with different frequency characteristics. Compare the simulation results before adding the frequency characteristic model with the simulation results after adding it to check the impact of the frequency characteristic model on the UAV automatic landing scenario.

[0009] Beneficial effects:

[0010] Based on the method of the present invention, a flight control computer frequency characteristic model is constructed, and the frequency characteristics of the embedded system hardware and the coupling characteristics of the flight control algorithm are fully considered in the UAV flight simulation, so that the modules of the flight control computer in the UAV flight simulation run in sequence, which is closer to the real situation and further increases the confidence of the UAV model.

[0011] The present invention realizes for the first time the joint simulation of embedded hardware frequency characteristic model, embedded system software model and flight dynamics model. In the virtual flight test, characteristic attributes such as flight control computer program execution time, thread cycle, task scheduling sequence, etc. are taken into account, which further improves the confidence of UAV flight simulation. It can be used for the design and optimization of flight control laws and flight control computer hardware systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 The present invention is a general flow chart of a method for constructing a flight tube computer frequency characteristic model based on Simulink;

[0013] Figure 2 This is a model decomposition diagram specifically related to the present invention;

[0014] FIG3 (a) is a schematic diagram of a frequency characteristic module of the present invention;

[0015] FIG3( b ) is a model diagram of a flight control computer partition module of the present invention;

[0016] Figure 4 This is the flight tube computer system model without adding the frequency characteristic model;

[0017] Figure 5 This is a comparison chart of the simulation results of the flight tube computer frequency characteristic model and the flight tube computer system model. DETAILED DESCRIPTION

[0018] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the protection scope of the present invention.

[0019] The invention provides a method for constructing a flight tube computer frequency characteristic model based on Simulink. Figure 1 The present invention provides a flowchart of a method for constructing a flight tube computer frequency characteristic model based on Simulink. It should be understood that the method may also include additional blocks not shown and / or may omit the blocks shown, and the scope of the present invention is not limited in this respect. Figure 1 As shown, the method comprises the following steps:

[0020] Step 1: Use the small frame counter model in Simulink to design the frequency characteristic model. Figure 2 As shown, the flight control computer frequency characteristic model includes a frequency characteristic model and a flight control computer model. First, different frequency characteristic models are built, and frequency enable signals of different rates (80Hz, 40Hz and 20Hz) are realized by introducing a small frame counter and input into the flight control computer, and then the execution of each functional module in the flight control computer is controlled by the enable signals of different frequencies.

[0021] Step 2: Use Simulink to build a UAV flight control computer model, which includes a fixed-wing L1 navigation law model, a fixed-wing total energy controller model, and a fixed-wing attitude controller model to achieve control of the UAV's guidance, total energy, and attitude.

[0022] Step 3: Combine the frequency characteristic model with the UAV flight control computer model to form a flight control computer frequency characteristic model, and partition the flight control computer frequency characteristic model according to the function. The first partition is input processing, the second partition is equipment monitoring and signal voting and monitoring, the third partition is automatic guidance solution (fixed-wing L1 navigation law model, fixed-wing total energy controller model), the fourth partition is three-axis attitude control (fixed-wing attitude controller model), and the fifth partition is output processing and emergency fault handling; the fifth partition is the emergency fault handling module, the second partition is the equipment monitoring module, and the third and fourth partitions are the flight control computer module. The flight control computer module uses the aircraft target position, current position, flight speed, angular velocity, and quaternion as input to solve the expected values ​​of the control surface angle, throttle and roll angular velocity. The frequency enable signal of the frequency characteristic model controls the operation of each module. Among them, the execution rate of the emergency fault handling module is 20Hz, the execution rate of the equipment monitoring module is 40Hz, and the execution rate of the remaining modules is 80Hz. When the flight control computer frequency characteristic model is running, the flight control computer module, equipment monitoring module, and emergency fault handling module are run in sequence according to the frequency characteristics. The entire flight control computer frequency characteristic model is partitioned by different execution rates to simulate the different functions of embedded computing hardware and the different frequency characteristics of the hardware. Under the enable signals of different frequencies, the functional modules in the four partitions run alternately to simulate the program execution process, thread cycle and other characteristic attributes of the actual flight control computer, further demonstrating the influence of the characteristics of embedded computing hardware in the simulation.

[0023] Step 4: Encapsulate the UAV physical model into FMU (Function Mock-up Unit), and conduct joint simulation tests on the FMU and flight control computer frequency characteristic models in the UAV automatic landing scenario and the flight control computer under delay conditions with different frequency characteristics. Compare the simulation results before and after the frequency characteristic model is added to check the impact of the frequency characteristic model on the UAV automatic landing scenario. In this step, the UAV physical model is introduced, including the six-degree-of-freedom model, aerodynamic model, hydraulic model, engine model sensor, servo actuation model, etc. By jointly simulating the UAV physical model and the embedded hardware frequency characteristic model, a UAV flight simulation closer to the real situation is simulated, showing the impact of the frequency characteristic model on the UAV simulation, and further improving the confidence of the flight control computer frequency characteristic model.

[0024] In summary, Simulink is used as a model development platform and simulation analysis platform to implement the method of constructing the frequency characteristic model of the flight tube computer based on Simulink. Simulink is used to convert mathematical models such as control algorithms and frequency characteristics into Simulink models of corresponding components.

[0025] FIG3 (a) is a schematic diagram of the frequency characteristic module of the present invention. As shown in FIG3 (a), specifically, the design of the frequency characteristic model using the small frame counter model in Simulink in step 1 includes: according to the delay module, addition module, constant module, remainder module, and data type conversion module in Simulink, the frequency enable signal with a frequency of 80Hz, 40Hz, and 20Hz is realized, and finally the signal is converted into a Boolean value. More specifically, it includes: using the delay module (Unit Delay), addition module (Sum), and constant module (Constant) in the Simulink basic module to count once in each calculation step (0.0125s) and output the result. Because the calculation step is 0.0125s, the output result frequency is 80Hz, and the remainder module (Mod) is used to perform remainder calculation on the output signal of the small frame counter respectively, so that the output signal is modulo the constant value 2 of the constant module (Constant) and output, and the output signal frequency is 40Hz, and the constant value 4 of the constant module is modulo and output, and the output signal frequency is 20Hz. The three signals constitute the small frame counter. The three frequency signals are converted into Boolean values ​​through the Data Type Conversion module, and finally three frequency enable signals with frequencies of 80 Hz, 40 Hz, and 20 Hz are obtained.

[0026] Specifically, the use of Simulink in step 2 to build a UAV flight control computer model includes: applying the adder, multiplier, integrator, and transfer function modules in Simulink to build a flight control computer model, and more specifically, including: using Simulink basic modules to implement the flight control computer control algorithm, and the Simulink basic modules include integration, gain, multiplication, merging, function and other modules. The flight control computer control algorithm includes: the L1 navigation rate model calculates the expected value of the roll angle and roll angular velocity of the UAV based on the quaternion, the flight speed in the body coordinate system, and the current position and target position of the aircraft in the geodetic coordinate system and outputs it. The fixed-wing total energy controller model calculates the expected value of the pitch angle and the throttle size of the UAV based on the quaternion, the flight speed in the body coordinate system, the current position and target position of the aircraft in the geodetic coordinate system, the target height, and the target speed. The fixed-wing attitude controller model calculates the UAV rudder angle based on the expected value of the roll angle, the expected value of the pitch angle, the three-axis angular velocity, and the flight speed in the body coordinate system.

[0027] Specifically, the frequency characteristic model is combined with the UAV flight control computer model in step 3 to form the flight control computer frequency characteristic model, and the partitioning is performed according to the function, including: the frequency enable signal in step 1 and the flight control computer control algorithm in step 2 are used to form the flight control computer frequency characteristic model, and the flight control computer frequency characteristic model is partitioned according to different functions, as shown in Figure 3 (b), the first partition is input processing, and the input signal of the UAV flight control computer module is controlled by the 80Hz frequency enable signal. The second partition performs equipment monitoring and signal voting and monitoring, and the input signals of different modules in the flight control computer frequency characteristic model are controlled by the 80Hz, 40Hz, and 20Hz frequency enable signals, the 80Hz frequency enable signal controls the flight control computer module input, the 40Hz frequency enable signal controls the equipment monitoring module input, and the 20Hz frequency enable signal controls the emergency fault handling module input. The third partition performs automatic guidance solution, including the L1 navigation rate model and the fixed-wing total energy controller model. The operation of the L1 navigation rate model and the fixed-wing total energy controller model is controlled by 80Hz, 40Hz, and 20Hz frequency enable signals. When the 80Hz frequency enable signal is 1, the automatic guidance solution is performed, and when other frequency enable signals are 1, it stops. The fourth partition performs three-axis attitude control, including the fixed-wing attitude controller model. The operation of the fixed-wing attitude controller model is controlled by 80Hz, 40Hz, and 20Hz frequency enable signals. When the 80Hz frequency enable signal is 1, the attitude control solution is performed, and when other frequency signals are 1, it stops. The fifth partition performs output processing and emergency fault processing. The output of the flight control computer frequency characteristic model is controlled by 80Hz, 40Hz, and 20Hz frequency enable signals. When the 80Hz frequency enable signal is 1, the data such as the rudder angle calculated by the UAV flight control computer is output. When the 40Hz frequency enable signal is 1, the device monitoring signal result is output. When the 20Hz frequency enable signal is 1, the fault handling module result is output.

[0028] Specifically, step 4 is to check the simulation results of the flight tube computer frequency characteristic model. Figure 4 The figure shows the flight tube computer model without frequency characteristics. By comparing the simulation results of the flight tube computer without the frequency characteristic model, the influence of the frequency characteristic model on the flight tube computer is verified. The final simulation result comparison chart is shown in Figure 5As shown, the solid line curve is the result without the frequency characteristic model, the dotted line curve is the result with the frequency characteristic model added, the horizontal axis of the curve is time (unit: second), and the vertical axis of the curve is the altitude of the drone (unit: meter). It can be seen from the figure that after adding the frequency characteristic model, the overshoot of the flight altitude result of the drone is larger and the time to enter the steady state is longer. After adding the frequency characteristic model, the drone has a control delay effect, which makes the flight tube computer of the drone need a longer calculation time to control the flight stability of the drone. The present invention ultimately makes the flight tube computer simulation closer to the actual operation of the equipment and improves the confidence of the flight tube computer simulation.

[0029] Although the above describes the illustrative specific embodiments of the present invention to facilitate those skilled in the art to understand the present invention, and it should be clear that the present invention is not limited to the scope of the specific embodiments, for those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations using the concept of the present invention are protected.

Claims

1. A method for constructing a flight tube computer frequency characteristic model based on Simulink, characterized in that: The steps include: Step 1: frequency enable signals of different rates are realized by introducing a small frame counter and input into the flight control computer, and then the execution of each functional module in the flight control computer is controlled by different frequency enable signals, wherein the frequency enable signals include three frequencies of 80 Hz, 40 Hz and 20 Hz; Step 2: Build a flight control computer model in the Simulink model. The flight control computer model includes a fixed-wing L1 navigation law model, a fixed-wing total energy controller model, and a fixed-wing attitude controller model to achieve control of the UAV's guidance, total energy, and attitude. Step three, combining the flight tube computer model with the frequency characteristic model to form a flight tube computer frequency characteristic model, and dividing the flight tube computer frequency characteristic model according to function, the flight tube computer frequency characteristic model consists of five partitions, the first partition performs input processing, the second partition performs equipment monitoring and signal voting and monitoring, the third partition performs automatic guidance solution, the fourth partition performs three-axis attitude control, and the fifth partition performs output processing and emergency fault processing, wherein the fifth partition is an emergency fault processing module, the second partition is an equipment monitoring module, the third partition and the fourth partition are flight tube computer modules, the emergency fault processing module execution rate is 20Hz, the equipment monitoring module execution rate is 40Hz, and the execution rates of the remaining modules are all 80Hz; Step 4: Encapsulate the UAV physical model into FMU, and conduct a joint simulation test on the FMU and flight tube computer frequency characteristic model in the UAV automatic landing scenario and the flight tube computer under delay conditions with different frequency characteristics. Compare the simulation results before adding the frequency characteristic model with the simulation results after adding it to check the impact of the frequency characteristic model on the UAV automatic landing scenario.

2. The method for constructing a flight tube computer frequency characteristic model based on Simulink according to claim 1, characterized in that: Step one includes: realizing output signals with frequencies of 80 Hz, 40 Hz, and 20 Hz according to a delay module, an addition module, a constant value module, a remainder module, and a data type conversion module in Simulink, and finally converting the signal into a Boolean value.

3. The method for constructing a flight tube computer frequency characteristic model based on Simulink according to claim 1, characterized in that: Step 2 includes: using adders, multipliers, integrators, and transfer functions in Simulink to construct a flight tube computer model.

4. The method for constructing a flight tube computer frequency characteristic model based on Simulink according to claim 1, characterized in that: Step three includes: controlling the input of each module in the flight tube computer frequency characteristic model through frequency enable signals of 80Hz, 40Hz, and 20Hz, wherein the flight tube computer module relies on the aircraft target position, current position, flight speed, angular velocity, and quaternion in the input data to calculate the expected values ​​of the control surface angle, throttle, and roll angular velocity.

5. The method for constructing a flight tube computer frequency characteristic model based on Simulink according to claim 1, characterized in that: In step 4, the UAV physical model includes a six-degree-of-freedom model, an aerodynamic model, a hydraulic model, an engine model sensor, and a servo actuation model.

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