Small recoverable cold flow rocket attitude active control system and method

Abstract

The invention discloses a small cold flow rocket attitude active control system, which is based on a two-degree-of-freedom platform, and the two-degree-of-freedom platform is formed by nesting two groups of nozzle brackets and is arranged in a shell at the nozzle end of a small cold flow rocket. Wherein the large nozzle support is composed of a large nozzle support body and a large nozzle support body, and the large nozzle support body can rotate left and right relative to the nozzle end shell; the small nozzle support is placed in the large nozzle support and connected with the shaft in a matched mode through the bearing, so that the small nozzle support can rotate front and back relative to the large nozzle support. Through adjustment of the thrust direction, gradual correction of the rocket attitude can be achieved, attitude changes can be responded in real time through closed-loop control, rapid adjustment is conducted, and the stability and accuracy of rocket flight are improved.

Description

Technical Field

[0001] The present invention relates to the field of attitude control of small cold flow rockets, and in particular to an active attitude control system and method for a small recyclable cold flow rocket. Background Art

[0002] The research and design of small rockets is not only for application in scientific experiments or education popularization, but also an important direction for the development of modern rocket technology. It can not only reduce costs and environmental risks, but also improve the operability and safety of equipment, so that it can be more widely used in education, scientific research, business and other fields. In the future, with the further maturity and promotion of technology, low-cost, high-safety, small rocket technology will surely provide strong support for the development and popularization of modern science and technology. Reusable and reduced launch costs are the inevitable trend of the future development of liquid rockets, and the attitude control of rockets is an important development direction of reusable liquid rockets. Therefore, the attitude control of the rocket body is applied to small rockets to achieve vertical take-off and landing and attitude stability of small rockets, thereby helping small rockets to hover, promote the popularization of education for reusable rockets, reduce launch costs, and improve reliability.

[0003] The attitude adjustment of small rockets can be divided into passive control and active control. Passive control usually includes adjusting the center of gravity of the rocket, designing a reasonable fixed tail, etc., and the controlled control alone cannot achieve the design goal. At present, the active control of the attitude adjustment of small rockets is mainly achieved by controlling the swing of the tail or by adding four ducted fans at the tail of the rocket. The attitude of the rocket tail is controlled by a precise and powerful motor to achieve the overall adjustment of its attitude during the flight of the rocket. Although this structure is simple in design and low in production cost, it has limited control accuracy, low stability, and is more dependent on the aerodynamic environment. Considering the small overall size of the small rocket, its control response speed and adjustment ability may be poor; the overall attitude of the small rocket is adjusted by adding four ducted fans, that is, the attitude of the rocket during flight is controlled by controlling the wind force of the four ducted fans placed around the small rocket. Although it has high control accuracy and response speed, and the attitude control is more flexible and the stability of the mechanism is strong, the design of the ducted fan system is relatively complex, and the related control and power distribution systems also add extra weight, which increases the design cost of the small rocket.

[0004] Therefore, there is an urgent need in the art for a small-scale recoverable cold flow rocket attitude active control system and method with high control accuracy and response speed. Summary of the invention

[0005] In order to solve the above technical problems, the purpose of the present invention is to provide a small recyclable cold flow rocket attitude active control system and method. Ordinary small cold flow rockets do not have the function of active attitude adjustment, and in order to achieve the vertical take-off and landing and hovering of small cold flow rockets, and to complete the recovery and reuse of small cold flow rockets, active control of their attitude is essential. The overall attitude of the rocket can be adjusted by controlling the direction of the rocket's nozzle. Liquid rockets in the aerospace field usually use vector nozzles to control the direction of the nozzle to achieve fine-tuning of the rocket's attitude. However, small rockets are limited by volume and cannot be equipped with vector nozzles with complex mechanical structures and huge volumes.

[0006] In order to achieve the above object, the present invention adopts the following scheme.

[0007] The invention discloses an active attitude control system for a small cold flow rocket. The system is based on a two-degree-of-freedom platform. The two-degree-of-freedom platform is composed of two sets of nozzle brackets nested together and placed in a shell at the nozzle end of the small cold flow rocket.

[0008] Optionally, the system further includes: a posture control nozzle and a transmission mechanism; the posture control nozzle is tubular and connected to the transmission mechanism via a nozzle bracket.

[0009] Optionally, the nozzle bracket is combined with a posture control nozzle to control the two groups of nozzle brackets to swing at an angle of up to 20° along two orthogonal axes in the horizontal direction. By vector combination of the swing angles of the two groups of nozzle brackets, the posture control nozzle can swing with two degrees of freedom in the horizontal direction.

[0010] Optionally, the two groups of nozzle brackets include: a group of large nozzle brackets and a group of small nozzle brackets. For ease of assembly, the large nozzle brackets are provided in number. The connection between the two large nozzle brackets is provided with an outwardly extending threaded hole surface, which is connected by M4 bolts.

[0011] A small cold flow rocket attitude active control method, the method comprising:

[0012] S100, attitude modeling for small cold-flow rockets;

[0013] S200, establishing a three-dimensional coordinate system with the center of mass of the rocket as the origin, and obtaining a dynamic model of the rocket;

[0014] S300, performing kinematic modeling on the attitude of the rocket to obtain its kinematic model;

[0015] S400. Design an active attitude control algorithm for a small cold flow rocket, and correct the rocket attitude through an active attitude control system of the small cold flow rocket.

[0016] Optionally, in S100, the attitude of the small cold flow rocket is described by Euler angles, and the control target is the real-time data of Euler angles returned by the sensor, including: yaw angle, pitch angle, and roll angle.

[0017] Optionally, in S200, the thrust output by the rocket is decomposed into three different coordinate axes to obtain the components in each direction: Fx, Fy, and Fz; the dynamic model of the rocket is obtained as follows:

[0018]

[0019] Among them, during the flight of the rocket, only its swing around the x and y axes is considered, and its rotation around the z axis is ignored. Therefore, in the z-axis direction of the rocket, there are only gravity G and resistance , and thrust , when thrust If the force is greater than the sum of the drag and gravity, the rocket rises, otherwise it falls; if the two are equal, the rocket hovers.

[0020] Compared with the prior art, the present invention has the following beneficial technical effects: by adjusting the thrust direction, the rocket attitude can be gradually corrected, and the yaw angle and pitch angle errors can be gradually reduced; the attitude changes of the rocket are monitored in real time by the attitude sensor, and the new attitude parameters are fed back to the control system to update the error signal, complete the closed-loop control, and can respond to attitude changes in real time, make rapid adjustments, and improve the stability and accuracy of the rocket flight. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings illustrate exemplary embodiments of the present invention and together with the description serve to explain the principles of the present invention. These drawings are included to provide a further understanding of the present invention and are incorporated in and constitute a part of this specification.

[0022] Figure 1 It is a design diagram of an active attitude control system for a small cold flow rocket in one embodiment of the present invention;

[0023] Figure 2 This is a physical diagram of a small cold flow rocket attitude active control system in one embodiment of the present invention;

[0024] Figure 3 In one embodiment of the present invention, a small nozzle bracket of an active attitude control system of a small cold flow rocket;

[0025] Figure 4 In one embodiment of the present invention, a large nozzle bracket 1 of an active attitude control system for a small cold flow rocket;

[0026] Figure 5In one embodiment of the present invention, a large nozzle bracket 2 of an active attitude control system for a small cold flow rocket;

[0027] Figure 6 In one embodiment of the present invention, a transmission mechanism for an active attitude control system of a small cold flow rocket;

[0028] Figure 7 In one embodiment of the present invention, the transmission mechanism M2*20 spur gear;

[0029] Figure 8 In one embodiment of the present invention, the transmission mechanism M2*46 is an incomplete gear;

[0030] Fig. 9 is an example diagram of a steering gear key in one embodiment of the present invention;

[0031] Fig.10 This is an example diagram of an M2*43 incomplete gear integrated with a frame in one embodiment of the present invention;

[0032] Fig.11 In one embodiment of the present invention, an M2*17 spur gear;

[0033] Fig.12 In one embodiment of the present invention, a nozzle end housing and a bracket of a small cold flow rocket attitude active control system;

[0034] Fig.13 In one embodiment of the present invention, a small cold flow rocket attitude dynamics model;

[0035] Fig.14 It is an example of MicoAir743 flight control in one embodiment of the present invention;

[0036] Fig.15 This is an example of a 50KG high torque waterproof rudder in one embodiment of the present invention;

[0037] Fig.16 is a flow chart of a PID attitude control algorithm in one embodiment of the present invention;

[0038] Fig.17 It is an example of the swing angle of two nozzle brackets in one embodiment of the present invention;

[0039] Fig.18 is an example of the rotation angle of the two nozzle support planes in one embodiment of the present invention;

[0040] Fig.19 is the rotation angle vector sum of the two nozzle support planes in one embodiment of the present invention;

[0041] Among them, 1: attitude control nozzle; 2: small nozzle bracket; 3: large nozzle bracket 2; 4: M4 bolts and nuts; 5: SKF619 / 9 bearing; 6: large nozzle bracket 1; 7: high-precision servo; 8: M2*17 spur gear; 9: servo key; 10: M5 bolts and nuts; 11: bearing seat; 12: nozzle end housing and bracket; 13: M2*46 incomplete gear; 14: M2*20 spur gear; 15: M3 cross screw; 16: SKF 61804 bearing. DETAILED DESCRIPTION

[0042] The following is combined with Figures 1 to 19 The present invention is further described in detail with reference to the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the relevant contents, rather than to limit the present invention. It is also necessary to explain that, for ease of description, only the parts related to the present invention are shown in the accompanying drawings.

[0043] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0044] Unless otherwise specified, the exemplary embodiments / embodiments shown will be understood as exemplary features that provide various details of some ways in which the technical concept of the present invention can be implemented in practice. Therefore, unless otherwise specified, the features of the various embodiments / embodiments can be combined, separated, interchanged and / or rearranged without departing from the technical concept of the present invention.

[0045] The use of cross-hatching and / or shading in the accompanying drawings is generally used to make the boundaries between adjacent components clear. As such, unless otherwise specified, the presence or absence of cross-hatching or shading does not convey or indicate any preference or requirement for the specific materials, material properties, dimensions, proportions, commonalities between the components shown, and / or any other characteristics, attributes, properties, etc. of the components. In addition, in the accompanying drawings, the sizes and relative sizes of the components may be exaggerated for clarity and / or descriptive purposes. When the exemplary embodiments can be implemented differently, the specific process sequence can be performed in a different order than described. For example, two successively described processes can be performed substantially simultaneously or in an order opposite to the described order. In addition, the same figure numbers represent the same components.

[0046] When a component is referred to as being "on" or "over," "connected to," or "coupled to" another component, the component may be directly on, directly connected to, or directly coupled to the other component, or intervening components may be present. However, when a component is referred to as being "directly on," "directly connected to," or "directly coupled to" another component, there are no intervening components. For this purpose, the term "connected" may refer to a physical connection, an electrical connection, etc., with or without intervening components.

[0047] For descriptive purposes, the present invention may use spatially relative terms such as "below", "beneath", "under", "lower", "above", "upper", "above", "higher", and "side (e.g., as in "sidewall")" to describe the relationship of one component to another (other) component as shown in the accompanying drawings. The spatially relative terms are intended to encompass different orientations of the device in use, operation, and / or manufacture in addition to the orientation depicted in the accompanying drawings. For example, if the device in the accompanying drawings is turned over, components described as "below" or "beneath" other components or features would then be positioned "above" the other components or features. Thus, the exemplary term "below" can encompass both the "above" and "below" orientations. Furthermore, the device may be otherwise oriented (e.g., rotated 90 degrees or at other orientations), and the spatially relative descriptors used herein should be interpreted accordingly.

[0048] The terms used here are for the purpose of describing specific embodiments, and are not intended to be restrictive. As used here, unless the context clearly indicates otherwise, the singular forms "one (kind, person)" and "said (the)" are also intended to include plural forms. In addition, when the terms "comprise" and / or "include" and their variations are used in this specification, it is explained that there are stated features, integral bodies, steps, operations, parts, assemblies and / or their groups, but it is not excluded that there are or add one or more other features, integral bodies, steps, operations, parts, assemblies and / or their groups. It should also be noted that, as used here, the terms "substantially", "approximately" and other similar terms are used as approximate terms and not as degree terms, so that they are used to explain the inherent deviations of the measured values, calculated values ​​and / or the values ​​provided that will be recognized by those of ordinary skill in the art.

[0049] In one embodiment, the present invention provides an active attitude control system for a small cold flow rocket. The system is based on a two-degree-of-freedom platform, which is composed of two sets of nested nozzle brackets and is placed in the nozzle end shell of the small cold flow rocket.

[0050] Optionally, the system further includes: a posture control nozzle and a transmission mechanism; the posture control nozzle is tubular and connected to the transmission mechanism via a nozzle bracket.

[0051] Optionally, the nozzle bracket is combined with a posture control nozzle to control the two groups of nozzle brackets to swing at an angle of up to 20° along two orthogonal axes in the horizontal direction. By vector combination of the swing angles of the two groups of nozzle brackets, the posture control nozzle can swing with two degrees of freedom in the horizontal direction.

[0052] Optionally, the two groups of nozzle brackets include: a group of large nozzle brackets and a group of small nozzle brackets. For ease of assembly, the large nozzle brackets are provided in number. The connection between the two large nozzle brackets is provided with an outwardly extending threaded hole surface, which is connected by M4 bolts.

[0053] In one embodiment, the present invention provides a method for active attitude control of a small cold flow rocket, the method comprising:

[0054] S100, attitude modeling for small cold-flow rockets;

[0055] S200, establishing a three-dimensional coordinate system with the center of mass of the rocket as the origin, and obtaining a dynamic model of the rocket;

[0056] S300, kinematically modeling the attitude of the rocket to obtain its motion-dynamics model;

[0057] S400. Design an active attitude control algorithm for a small cold flow rocket, and correct the rocket attitude through an active attitude control system of the small cold flow rocket.

[0058] Optionally, in S100, the attitude of the small cold flow rocket is described by Euler angles, and the control target is the real-time data of Euler angles returned by the sensor, including: yaw angle, pitch angle, and roll angle.

[0059] Optionally, in S200, the thrust output by the rocket is decomposed into three different coordinate axes to obtain the components in each direction: Fx, Fy, and Fz; the dynamic model of the rocket is obtained as follows:

[0060]

[0061] Among them, during the flight of the rocket, only its swing around the x and y axes is considered, and its rotation around the z axis is ignored. Therefore, in the z-axis direction of the rocket, there are only gravity G and resistance , and thrust , when thrust If the force is greater than the sum of the drag and gravity, the rocket rises, otherwise it falls; if the two are equal, the rocket hovers.

[0062] In one embodiment, in order to solve the problems of low attitude control accuracy, slow response speed, weak system stability, low structural strength, etc. of small rockets, refer to Figure 1 The present invention is based on a small cold flow rocket and designs a special two-degree-of-freedom platform, which is composed of a large nozzle bracket and a small nozzle bracket nested together; wherein, the large nozzle bracket is composed of a large nozzle bracket 1 and a large nozzle bracket 2, which are placed in the nozzle end shell of the small cold flow rocket and are connected to the shaft through the cooperation of the bearing.

[0063] The large nozzle bracket can rotate left and right relative to the nozzle end housing; the small nozzle bracket is placed in the large nozzle bracket and connected to the shaft through the bearing, so that the small nozzle bracket can rotate forward and backward relative to the large nozzle bracket. Through this design, the small nozzle bracket can achieve two degrees of freedom movement relative to the nozzle end housing, front and back and left and right, thereby forming the two-degree-of-freedom platform.

[0064] The direction of the rocket nozzle is adjusted by controlling the two-degree-of-freedom platform. The specific process is as follows:

[0065] After receiving and processing the signal from the sensor, the main control board sends control instructions to the two servos; after receiving the signal, the servos control the servo shafts to move to the corresponding angles. The servo shafts are fixed with the gear on one side of the gear transmission mechanism through the servo key, and the gear on the other side is fixed to the frame;

[0066] During the manufacturing process, the gear and the frame are integrally formed by 3D printing, or fixed to the shaft by a built-in keyway. The shaft and the nozzle bracket are integrally formed by 3D printing, and the large nozzle bracket and the small nozzle bracket are driven to rotate through gear transmission to achieve the posture adjustment of the two-degree-of-freedom platform.

[0067] Optionally, the nozzle of the small cold flow rocket can be nested and constrained on the small nozzle bracket, and the direction can be adjusted synchronously with the movement of the small nozzle bracket. With the corresponding control algorithm, the control of the nozzle direction of the small cold flow rocket is realized, thereby completing the adjustment of the overall attitude of the small cold flow rocket.

[0068] In one embodiment, if Figure 1 and Figure 2 As shown, according to the hardware structure strength and accuracy requirements of a small cold flow rocket attitude active control system, the present invention provides a small cold flow rocket attitude active control system. In a small cold flow rocket attitude active control system, based on the two-degree-of-freedom platform, the system includes: an attitude control nozzle, a nozzle bracket, a shaft and bearings, a transmission mechanism, a servo, a nozzle end housing and a bracket.

[0069] Exemplarily, its overall dimensions are Π*92mm*92mm*122mm.

[0070] The attitude control nozzle adjusts the overall attitude of the small cold flow rocket by controlling the nozzle direction of the small cold flow rocket. A small liquid nozzle is used to release compressed gas to generate a reaction force to change the attitude by opening and closing the valve.

[0071] Reference Figure 1 The attitude control nozzle is tubular, about 43mm long, with a maximum outer diameter of 30mm and an inner diameter of 26mm, and a minimum outer diameter of 26mm and an inner diameter of 20mm; it is made of metal; it is installed at the end of the flexible nozzle and connected to the transmission mechanism through the nozzle bracket. The cylinder nozzle is directly connected to the flexible tube, and the outer diameter of the connection with the nozzle bracket is 30, and the surface is smooth to facilitate the cooperation with the nozzle bracket.

[0072] Reference Figures 3 to 5 , the nozzle bracket is used to transfer the control of the nozzle direction of a small cold flow rocket to the swing control of the nozzle bracket.

[0073] The nozzle bracket is combined with the nozzle to control the large and small nozzle brackets to swing at an angle of up to 20° along two orthogonal axes (i.e., X-axis and Y-axis) in the horizontal direction, such as Fig.17 The two-degree-of-freedom swing of the nozzle in the horizontal plane direction is achieved by combining the vectors of the swing angles of the two brackets, as shown in Fig.18 and Fig.19 As shown, is the swing angle of the large nozzle bracket, The swing angle of the large nozzle bracket is the swing angle of the small nozzle bracket. Among them, the highest swing angle is determined by comprehensively considering the hardware quality and the rocket adjustment capability requirements.

[0074] The nozzle bracket is generally square in shape. The overall size of the small nozzle bracket is about 40mm long (excluding the shaft), 40mm wide, 30mm high, and the internal pipe diameter is 30mm. The large nozzle bracket consists of two parts, large nozzle bracket 1 and large nozzle bracket 2. The overall size is about 76mm long (excluding the shaft), 68mm wide (excluding the gear and steering gear slot), 40mm high (excluding the gear and steering gear slot), the internal length is 60mm, and the width is 52mm.

[0075] The nozzle bracket is made of resin and is installed at a specific position of the large nozzle bracket and the shell by cooperating with the bearing.

[0076] The small nozzle bracket is placed inside the large nozzle bracket. The rotation margin of the small nozzle bracket is fully considered inside the large nozzle bracket, and for the convenience of assembly, the large nozzle bracket is divided into two parts. The connection is provided with an outwardly extending threaded hole surface, which is connected by M4 bolts; there are two through holes on the side of the large nozzle bracket for placing the bearings of the small nozzle bracket shaft; the two sub-parts of the large nozzle bracket are respectively designed with servo slots and gears for placing the servo and transmitting, ensuring that the servo is not subjected to stress and improving the compactness of the structure.

[0077] The bearing is used to ensure the relative rotation between the small nozzle bracket and the large nozzle bracket, and between the large nozzle bracket and the housing, and to transmit torque; the shaft is designed according to the selected bearing and is integrally formed with the nozzle bracket to ensure structural strength and improve structural compactness.

[0078] The shaft and bearing cooperate to transmit torque and ensure relative rotation. The shaft is cylindrical, and the shaft on the small nozzle bracket is about 19mm long, 9mm in outer diameter, and the key is 3mm*3mm*3mm; the shaft on the large nozzle bracket is about 43mm long and 20mm in outer diameter. The bearings are standard parts, two SKF 61804 bearings and two SKF 619 / 9 bearings.

[0079] The shaft is made of resin and metal, and the shaft and the nozzle bracket are integrally formed. The bearing is installed at the designed position of the housing and the bracket. The bearing is fixed by means of shaft shoulder positioning; the shaft on the small nozzle bracket has a smaller diameter. To ensure the structural strength, a hollow shaft is designed with a solid iron column inserted inside; a key is designed on one end of the shaft for connection with the gear.

[0080] Reference Figures 6 to 11 The transmission mechanism controls the rotation of the nozzle bracket by transmitting motion and torque through transmission mechanisms such as gear transmission.

[0081] Gear transmission is used as the transmission mechanism, and the incomplete gear and the gear and bracket are integrated to improve the compactness and strength of the structure. Since the servo is not directly connected to the shaft, the servo is not subjected to force, the overall transmission mechanism is small in size, the structural strength is high, the motion analysis is simple, and the control accuracy is high, but it also increases the difficulty of structural design and assembly.

[0082] A pair of standard involute spur gears connected to the small nozzle bracket: transmission ratio is 92:40, pressure angle is 20°, module is 2, number of teeth of small gear is 20, number of teeth of large gear is 46, tooth top height coefficient ha* =1, top clearance coefficient C*=0.25, tooth thickness is 6mm. A pair of standard involute spur gears connected to the large nozzle bracket: transmission ratio is 86:34, pressure angle is 20°, module is 2, number of teeth of small gear is 17, number of teeth of large gear is 43, tooth top height coefficient ha* =1, top clearance coefficient C*=0.25, tooth thickness is 6mm. Made of resin material, each pair of gears is installed on the steering gear shaft and the nozzle bracket shaft respectively.

[0083] The large gear of each pair of gears is larger in size and therefore uses incomplete gears to avoid interfering with the movement of other components; the large gear located on the large nozzle bracket shaft is selected to be integrally formed with the large nozzle bracket to improve the compactness and strength of the structure; the corresponding keyway is designed inside the gear; the small gear is connected to the servo through a special servo key; the large nozzle brackets 1 and 2 are fixed with M5 bolts.

[0084] The servo controls the nozzle bracket by controlling the servo to rotate a certain angle and transmitting the motion through the transmission mechanism. The servo is mainly composed of the following parts: a steering wheel, a reduction gear set, a position feedback potentiometer 5k, a DC motor, a control circuit board, etc. The control circuit board receives the control signal (PWM signal) from the signal line to control the rotation of the motor. The motor drives a series of gear sets and transmits the signal to the output servo after deceleration. The output shaft of the servo is connected to the position feedback potentiometer. When the servo rotates, it drives the position feedback potentiometer. The potentiometer will output a voltage signal to the control circuit board for feedback. Then the control circuit board determines the rotation direction and speed of the motor according to the position, so as to achieve the target stop.

[0085] It is roughly square in shape, about 40 mm long, 20 mm wide and 40 mm high, made of plastic and metal, and installed in the servo slot designed on the large nozzle bracket and the shell.

[0086] Reference Fig.12 The nozzle end shell and bracket are mainly used to fix and install the internal components of the vector control mechanism, ensuring the beauty and simplicity of the cabin of the attitude control part of the small cold flow rocket. The internal components of the vector control mechanism are reasonably designed to support the internal components, ensure the overall structural strength, and meet its assembly requirements.

[0087] The nozzle end shell and the bracket are generally tubular, about 100mm long, 184mm outer diameter, and 180mm inner diameter. The resin material is used to ensure the installation of the internal components of the vector control mechanism during installation and connect with other cabins of the small cold flow rocket.

[0088] The bracket and the nozzle end shell are integrally formed; the bracket and the steering gear slot extend out of the shell; in order to meet the assembly requirements of the large nozzle bracket and ensure the compact structure of the entire cabin, the shell is slotted on its corresponding side so that a bearing seat is formed separately and is designed with M5 bolt assembly connection.

[0089] In one embodiment, according to the algorithm stability and response speed requirements of the attitude active control system of a small cold flow rocket, the present invention provides an attitude active control method of a small cold flow rocket, comprising:

[0090] 100. Carry out attitude modeling for a small cold flow rocket;

[0091] The attitude control of aircraft is a closed-loop control based on mathematical mechanism model and multi-sensor parameter fusion. Therefore, to achieve attitude control, the attitude modeling of the aircraft must be carried out first. Its attitude is described by Euler angles, and the control target is the real-time Euler angle data returned by the gyroscope sensor, including: yaw angle, pitch angle, and roll angle.

[0092] like Fig.13 As shown, the small cold flow rocket model consists of three parts: inertial navigation cabin (electronic components, guidance), power cabin (power storage, main structure), and vector mechanism (attitude control, power output).

[0093] S200, establishing a three-dimensional coordinate system with the center of mass of the rocket as the origin O; due to the rocket power loss, the center of mass is a dynamic point, where O1 is the thrust action point; obtaining the dynamic model of the rocket;

[0094] The thrust output by the rocket is decomposed into three different coordinate axes to obtain the components in each direction: Fx, Fy, Fz, where L represents the length of the lever arm. Since the center of mass of the rocket deviates from the origin of the coordinate system, and the thrust action point coincides with the origin of the coordinate system, the thrust generates an active torque on the entire ship, thereby achieving control of the attitude of the small rocket. The dynamic model of the rocket is obtained as follows:

[0095]

[0096] It should be noted that during the flight of the rocket, only its swing around the x and y axes is considered, while its rotation around the z axis is ignored. This is because the rotation of the rocket around its own axis can be regarded as a self-balancing effect starting from the angular momentum. Therefore, in the z-axis direction of the rocket, only gravity G and resistance , and thrust In, when the thrust If the force is greater than the sum of the drag and gravity, the rocket rises; otherwise, it falls; if the two are equal, the rocket hovers.

[0097] In fact, the dynamic model here is about the modeling of the rocket's own coordinate system. In actual flight, for the rocket's ballistic flight process, the dynamic model needs to re-project the various forces in flight to the rocket's own coordinate system. Its modeling method is consistent with this dynamic model. The dynamic modeling here is mainly used to show the attitude control of the vector mechanism to adjust the rocket's attitude.

[0098] S300, performing kinematic modeling on the attitude of the rocket to obtain its kinematic-dynamic model;

[0099] According to the existing theory, the attitude of the rocket is described by the Euler angle, and the attitude angle is defined as the rotation angle around each axis when the machine system rotates according to ZYX and is parallel to the inertial system. According to the rotation relationship, the attitude angle ( ) and the three coordinate displacements (x, y, z) kinematic model:

[0100]

[0101] , Represent the yaw angle and pitch angle respectively.

[0102] According to Newton's second law, the relationship between the attitude angle and the acceleration of the three coordinate axes is obtained, that is, the motion-dynamic model of the rocket. If the attitude is in the preset value under ideal conditions, that is When the acceleration of the x-axis and y-axis is always 0, the acceleration of the z-axis is equal to the acceleration of gravity, reaching mechanical equilibrium and the rocket hovers.

[0103]

[0104] Dynamic model for rocket, where It is in an out-of-control state and is not always 0. Therefore, the acceleration on the z-axis is in a free fluctuation range. Therefore, it is necessary to consider the thrust correction to control the z-axis direction.

[0105] S400, such as Fig.16 As shown, an active attitude control algorithm for a small cold flow rocket is designed to obtain the angle error coefficient, which is used to correct the rocket attitude.

[0106] The small cold flow rocket attitude active control algorithm adopts PID algorithm to form closed-loop control as a whole, which can realize offline control; the PID attitude control algorithm includes:

[0107] S401, obtaining the current attitude parameters of the rocket in real time through an attitude sensor (such as a gyroscope), including: yaw angle (yaw) and pitch angle (pitch); comparing the current attitude parameters with preset target attitude parameters, and generating corresponding error signals, i.e., yaw angle errors;

[0108] For example, a highly centralized UAV flight control chip is selected, which integrates MCU, drive circuit and attitude-related sensors (accelerometer, gyroscope), and can process input and output data at high speed; a servo with fast response and high-precision mechanical transmission output is selected as the device for driving the vector mechanism, such as Fig.14 , Fig.15 shown.

[0109] During the attitude control process, it is first necessary to determine whether the current yaw angle error is within the allowable range; if it does not exceed the preset allowable error range, the system considers the current attitude to be stable and no adjustment is required, and continues with attitude detection; if any error exceeds the allowable range, thrust adjustment is required to correct the rocket's attitude.

[0110] S402: Proportional amplification, differential gain and integral gain calculation are performed on the error signal by using a PID algorithm.

[0111] The yaw angle error is proportionally amplified, differential gain and integral gain are calculated respectively. According to the PID calculation formula, the proportional amplification (P) part is used to directly amplify the error signal, the differential gain (D) part is used to calculate the error change rate, and the integral gain (I) part is used to accumulate the error. Through the comprehensive calculation of these three parts, a more accurate control signal can be obtained.

[0112] Scale up:

[0113] Integral gain:

[0114] Differential gain:

[0115] Pyaw and Ppitch are the proportional gain outputs in the yaw and pitch directions, respectively, KP: proportional gain coefficient; eyaw and epich: errors in the yaw and pitch directions, respectively; Iyaw and Ipitch: integral gain outputs in the yaw and pitch directions, respectively, KI: integral gain coefficient; Dyaw and Dpitch: differential gain outputs in the yaw and pitch directions, respectively, KD: differential gain coefficient.

[0116] S403, synthesize the calculation results of the proportional, differential and integral parts to obtain the final angle error coefficient, where: and are the angular error coefficients in the yaw and pitch directions, respectively.

[0117]

[0118] S404. Correct the thrust of the rocket on each axis according to the angle error coefficient to correct the rocket attitude.

[0119] is the total thrust of the rocket, and the thrust is divided by the angle error coefficient Decomposed into components in different axis directions, namely components on the x, y and z axes. According to the angle error coefficient, the thrust components of each axis will change with the adjustment of the attitude.

[0120]

[0121] Among them, the role of the rocket thrust vector mechanism requires the direction of its steering gear rotation angle and its action time. The direction is given by the thrust adjustment coefficient, and the action time is determined by the update time of the PID algorithm. The faster the PID algorithm outputs, that is, the shorter the integral time, the shorter the thrust direction adjustment time, and the more sensitive the attitude adjustment. The integral or differential variable dt in the PID algorithm determines the accuracy of the control output.

[0122] The attitude active control system was tested, and the test results are shown in Table 1. By swinging the gyroscope to simulate the attitude deviation of the rocket, the attitude active control system can adjust the two-degree-of-freedom platform to produce a designed angle of deflection, and the test error does not exceed ±0.5°, which meets the design requirements.

[0123] Table 1 Test results of the active attitude control system (when installed, the design angle will be adjusted according to the size of the rocket)

[0124]

[0125] In summary, the method of the present invention adopts the PID algorithm to achieve the following technical effects.

[0126] 1. Attitude correction: By adjusting the thrust direction, the rocket attitude can be gradually corrected, and the yaw and pitch angle errors are gradually reduced. The attitude sensor monitors the rocket's attitude changes in real time, and feeds back the new attitude parameters to the control system to update the error signal and complete closed-loop control.

[0127] 2. Closed-loop control: The entire process is a closed-loop control system that ensures that the rocket's attitude always remains within the preset target range through continuous detection, calculation, adjustment and feedback. The advantage of a closed-loop control system is that it can respond to attitude changes in real time, make rapid adjustments, and improve the stability and accuracy of the rocket's flight.

[0128] In summary, the rocket attitude control system and method of the present invention obtains the current attitude parameters in real time through the attitude sensor, compares it with the target attitude, and generates an error signal. The error signal is proportionally amplified, the differential gain and the integral gain are calculated through the PID algorithm, the thrust direction adjustment coefficient is synthesized, and the thrust direction is input to the thrust direction action mechanism for thrust direction adjustment, and finally the rocket attitude is corrected. The whole process forms a closed-loop control system to ensure that the rocket maintains a stable attitude during flight and improve the safety and reliability of flight.

[0129] In the description of this specification, the description with reference to the terms "one embodiment / method", "some embodiments / methods", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment / method or example are included in at least one embodiment / method or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment / method or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments / methods or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments / methods or examples described in this specification and the features of the different embodiments / methods or examples, unless they are contradictory.

[0130] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0131] It should be understood by those skilled in the art that the above embodiments are only for the purpose of clearly illustrating the present invention, and are not intended to limit the scope of the present invention. For those skilled in the art, other changes or modifications may be made based on the above disclosure, and these changes or modifications are still within the scope of the present invention.

Claims

1. A small cold flow rocket attitude active control system, characterized in that: The system is based on a two-degree-of-freedom platform, which is composed of two sets of nozzle brackets nested and placed in the nozzle end shell of a small cold flow rocket.

2. The system according to claim 1, characterized in that Preferably, the system further comprises: a posture control nozzle and a transmission mechanism; the posture control nozzle is tubular and connected to the transmission mechanism via a nozzle bracket.

3. The system according to claim 2, characterized in that The nozzle bracket is combined with the attitude control nozzle to control the two groups of nozzle brackets to swing at an angle of up to 20° along two orthogonal axes in the horizontal direction. Through the vector combination of the swing angles of the two groups of nozzle brackets, the attitude control nozzle can swing with two degrees of freedom in the horizontal direction.

4. The system according to claim 1, characterized in that The two groups of nozzle brackets include: a group of large nozzle brackets and a group of small nozzle brackets.

5. A method for active attitude control of a small cold flow rocket, characterized in that: The method comprises: S100, attitude modeling for small cold-flow rockets; S200, establishing a three-dimensional coordinate system with the center of mass of the rocket as the origin, and obtaining a dynamic model of the rocket; S300, performing kinematic modeling on the attitude of the rocket to obtain its kinematic model; S400. Design an active attitude control algorithm for a small cold flow rocket, obtain the angle error coefficient, and correct the rocket attitude through the active attitude control system of the small cold flow rocket.

6. The method according to claim 5, characterized in that In S100, the attitude of the small cold flow rocket is described by Euler angles, and the control target is the real-time Euler angle data returned by the sensor, including: yaw angle, pitch angle, and roll angle.

7. The method according to claim 5, characterized in that In S200, the thrust output by the rocket is decomposed into three different coordinate axes to obtain the components in each direction: Fx, Fy, and Fz; the dynamic model of the rocket is obtained as follows: , Among them, during the flight of the rocket, in the z-axis direction of the rocket, only gravity ,resistance , and thrust , when thrust If the force is greater than the sum of the drag and gravity, the rocket rises, otherwise it falls; if the two are equal, the rocket hovers.

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