Design and realization of a small launch system with autonomous regulation and recognition guidance

A small launching system with autonomous regulation and recognition guidance is designed. Firstly, it ensures a solid and reliable transmission on the mechanical structure of the launcher and the small vehicle. Further, stepper motors and sensors are used to ensure precise control and effective feedback of the angle of the launcher. The small vehicle is equipped with the functions of guidance signal recognition and attitude adjustment, which have the advantages of strong real-time and high versatility. Finally, the practicality and accuracy of the designed launching system to a certain extent are verified through tests.


Introduction
Under the rapid development of modern science and technology, unmanned platforms are increasingly becoming the focus of various fields [1] .After reviewing the relevant literature, we find that domestic and foreign research on unmanned launch systems has certain shortcomings.Firstly, domestic and foreign research on launch systems tends to be large-scale, such as rocket launchers [2] in the aerospace field and missile launchers [3] in the military field.Secondly, the research on small launching systems tends to be militarized, such as the Stinger man-portable surface-to-air missile [4] , which is widely used by many countries.In addition, most of the currently studied small aircraft [5] carry their power source, complicate the structure of the vehicle to a certain extent, weaken the efficiency of civil use, and have a high cost.
Overall, current research on automatic launch systems is characterized by large-scale and military applications, while less research has been conducted on launch systems that combine miniaturization and service for civilian use, so this paper focuses on autonomous small-scale launch systems.It can be regarded as a microcosm of the large missile system, but its cost is greatly reduced, and its application range is wide, not only at the military level but also in the civilian aspects of many applications, such as forest firefighting [6] and material delivery.

Functional requirements analysis
To fully consider the needs of civilian use, the small launch system needs to meet the lightweight design conditions [7] and have a certain degree of launch accuracy in a close-range windless environment.Therefore, the relevant parameter requirements are reflected in Table 1.
Table 1.Requirement analysis and some parameters of the launch system.

Launch system design program
As shown in Figure 1, a small vehicle launch system is designed, which consists of a launching device and its mounted small vehicle.
Figure 1.Overall physical diagram of the launch system.During the design process of the launch system, some calculations were performed and the symbols used in the calculations are defined as shown in Table 2.
Table 2. Definition of relevant parameters for launch system design.
Parameter symbol Significance Units

Design of the launcher
Firstly, it is the mechanical design section of the launcher.The launch attitude angle adjustment design is shown in Figure 2. To ensure the accuracy and stability of the angle adjustment, we chose the combination of stepping motor and silk rod adjustment.For power solutions, we adopt the friction wheel with brushless DC motors, as shown in Figure 3.To reduce the speed fluctuation caused by the friction wheel stall in the acceleration process, we refer to the reasonable inner and outer diameter selection of friction wheels [8] , so we choose three sets of 72/48 mm friction wheels for transmission and acceleration.The ejection trigger mechanism is shown in Figure 4.The use of a centric crank-slider mechanism [9]   , which converts rotation into direct motion, enables the transfer of the small vehicle from the placement position to the acceleration orbit while maintaining attitude stability.For the mounting mechanism, the launcher mounts four small vehicles through the tube structure.To satisfy the intermittent motion condition and weaken the motor position control precision to some extent, we adopt the grooved wheel mechanism in the design process, as shown in Figure 5.  Secondly, it is the simulation calculation and sensor selection section of the launcher.To realize the closed-loop control of the launch angle adjustment of the launcher, we choose the sensor that can reflect the angle of the Yaw and Pitch axes of the launcher [10] .
The yaw axis angle feedback loop is realized by an angle encoder with a range of 360 degrees and an accuracy of 12 bits.Eqs. ( 1) and ( 2) show the results of the accuracy calculations.
The Pitch axis angle feedback loop is realized by means of a drawstring displacement sensor with a range of 1 m and an accuracy of 10 bits.Air resistance is neglected due to the short lag time and the simulated environment is static wind condition [11] .Eqs. ( 3), (4), and (5) reflect the effect on the drop point regarding the pitch axis angle.
Under the same conditions, considering the effect of the displacement sensor data on the angle of the Pitch axis, we can get Eqs.( 6) and (7).(2 The unit feedback accuracy near the Pitch axis angle of 35° and the launch initial velocity of 23 m/s can be deduced by the following equations.From Eqs. ( 5) and ( 7), we can get Eqs.( 8) and ( 9).
As verified in Figure 6, the linear correlation between the Pitch axis angle and the height of the launcher is better near the Pitch axis angle of 35° and the launching initial velocity of 23 m/s, so it is feasible to use the pull-wire displacement sensor instead of the angle sensor.Finally, it is the hardware construction and concrete realization section of the launcher.On this basis, combined with the mechanical structure [12] , we designed the hardware block diagram of the launcher as shown in Figure 7.

Design of the small aircraft
Firstly, it is the mechanical design section of the small aircraft.
To meet the functional requirements, this small aircraft needs to have a good aerodynamic shape based on the battery and control board.In terms of the wing design, under static wind conditions with a pressure of 101.325 kPa and a temperature of 20°C, the Reynolds number is small, and the air resistance is dominated by viscous forces [13] .Most of the conventional airfoils do not perform well at low Reynolds numbers, so the flat airfoils are directly adopted.
For the controllable small aircraft, the center of gravity is slightly closer to the center of the aircraft for good maneuverability and to embed the control board and camera assembly.The structural design is shown in detail in Figure 8.The mechanical aircraft is placed on its static stability, with its center of gravity at about the first 1/3 of the whole, and the aerodynamic focus position is relatively far back.The magnitude of the vorticity reflects the aerodynamic focal position of the aircraft to some extent, which can be seen in Figure 9.  Secondly, it is the hardware construction and concrete realization section of the small aircraft.For the controllable aircraft, we choose OpenMV as the core control board, which is also STM32 kernel in nature.The sensors are an IMU expansion board and camera module, and IMU is used for attitude data acquisition and the camera module is used for guidance signal capture.In this case, the attitude self-stabilization adjustment of IMU data is used as the inner-loop control, and the attitude change of the image guidance signal is used as the outer-loop control to realize the control of the rudder surface by generating PWM signals through the serial PID algorithm [14] .The structure is shown in Figure 10.Finally, it is the software and algorithm section of the small aircraft.The software algorithm of the controllable aircraft is divided into two parts: the attitude control part and the target recognition part.In the attitude control part, we use OpenMV's IMU expansion board to obtain the attitude data, get the Roll and Pitch axis angles of the dart through the Kalman filtering algorithm, and then control the servo through the main control to achieve the effect of maintaining the attitude.Due to the short lag time, we use a linearized model for fitting.For target recognition, we use the OpenMV platform, which identifies the target by finding the color blocks and communicates with the main control board to control the flight trajectory.Recognizing the target can be achieved by significantly reducing the exposure time to achieve better recognition results.We refer to the typical application for OpenMV [15] to optimize and improve the visual recognition guidance algorithm, which is shown in Table 3.

Algorithm 1:
We initialize camera center coordinates (x 0 , y 0 ); 2: We read half of the maximum range of pixel points in the field of view (x m , y m ); 3: While True do; 4: If pixel points where the field of view has no guidance signal, then:

Physical testing and analysis
The controllable vehicle was mixed with the mechanical vehicle for testing, and a green guidance light was used to visually guide the controllable vehicle during the combined test.After more than 2, 000 tests, the range of launch landing points was obtained, as shown in the Table 4.

Conclusions
This paper proposes the design and realization of a small launch system with autonomous regulation and recognition guidance.The launching device adopts the joint design of inter-device communication and human-computer communication at the hardware level, and the small aircraft is equipped with a certain degree of intelligent regulation and recognition capability.After theoretical calculations, the practicality of the proposed method is verified through experiments in a simulated environment, and the designed launch system has the advantages of low cost, high control accuracy, and strong portability.
Distance of the simulated target 50 m Circular probability error of the vehicle's landing point 0

aFFF
The long side of the projection of the launcher on the ground m  The pitch axis angle of the launcher ° x Pitch axis unit feedback accuracy of the launcher m yaw Theoretical feedback accuracy of yaw axis angle sensor ° pitch Theoretical feedback accuracy of pitch axis displacement sensor m

Figure 2 .
Figure 2. Schematic diagram of the launch attitude angle adjustment scheme.

Figure 3 .
Figure 3. Schematic diagram of friction wheel power scheme.

Figure 4 .
Figure 4. Schematic diagram of the ejection trigger mechanism.

Figure 5 .
Figure 5. Schematic diagram of the mounting mechanism.

Figure 6 .
Figure 6.Effect of speed and angle or height of launcher on launch distance.Finally, it is the hardware construction and concrete realization section of the launcher.On this basis, combined with the mechanical structure[12] , we designed the hardware block diagram of the launcher as shown in Figure7.

Figure 7 .
Figure 7. Block diagram of the launcher hardware.

Figure 8 .
Figure 8.The internal and external structure of the controllable aircraft.

Figure 9 .
Figure 9. Vortex cloud maps for different angles of approach of the mechanical aircraft.

Figure 10 .
Figure 10.Block diagram of controllable vehicle hardware.

Table 4 .
Test results of launch drops.the simulation environment and accuracy requirements mentioned in 2 reveals that the requirements have been better met.