Attitude control method for parallel mechanism of gun

Abstract

The application discloses a posture control method of a parallel mechanism for a gun, and the posture control method can convert linear movement of two push rods into pitching movement and yawing movement of a gun platform through a two-degree-of-freedom parallel structure composed of servo push rods, Hooke joints, spherical hinges and a rack. The posture control method of the parallel mechanism for the gun can calculate the stroke length of the push rod from any given posture angle of the gun platform, that is, the aiming direction of the gun platform is controlled by controlling the length of the push rod.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of intelligentization of firearms, and particularly relates to a posture control method of a parallel mechanism for firearms. BACKGROUND

[0002] One application field of the intelligentization of firearms is a firearm posture automatic control technology. The posture of a firearm is mainly described by the pitching rotation and the yaw rotation of the firearm. A servo mechanism capable of realizing automatic control is loaded on the firearm, so that when a shooter aims and shoots, the automatic tracking process of a target can be realized, and the adverse effects of the shaking of the environment and the shooter holding the firearm on stable aiming can be eliminated. In addition, the automatic control structure can also be applied to a non-handheld unmanned combat platform to also realize the functions of automatic tracking of a target and elimination of platform shaking. The key to realizing stable aiming by using a servo mechanism lies in compact structure, light weight and precise control. The volume, weight, man-machine efficiency and reliability of the servo mechanism are required to be high. A traditional posture control structure is a series structure, and a control method is to independently control two pitching motors and a yaw motor to achieve the purpose of controlling the posture of the firearm. The problem of the structure lies in that the mechanism occupies a large volume, the mechanism has a large mass and poor mechanical performance, and the structure is slightly unsuitable for use in small handheld or small unmanned platforms. SUMMARY

[0003] The application aims to provide a posture control method of a parallel mechanism for firearms. The posture control of a firearm includes the control of two-degree-of-freedom rotation of the firearm, including the pitching rotation and the yaw rotation. The application proposes a principle method of the posture control of the firearm suitable for the two-degree-of-freedom parallel mechanism by deducing the relationship among the aiming direction vector of the firearm, the rotation Euler angle and the rotation matrix.

[0004] The technical scheme for realizing the object of the application is as follows.

[0005] A posture control method of a parallel mechanism for firearms is characterized in that a vertical Hooke joint and two spherical joints are arranged on a rack, a servo push rod is arranged on each of the two spherical joints, the servo push rod is connected with a firearm platform through a cross shaft Hooke joint, and the firearm platform is further connected with the vertical Hooke joint. The pitching angle and the yaw angle of the firearm platform are controlled by respectively controlling the elongation of the servo push rods, and the purpose of controlling the posture of the firearm is achieved, and the following conditions are met.

[0006]

[0007] The required EF length is calculated, and then the length of the push rod when the push rod is shortened to the shortest is subtracted, so that the required elongation of the servo push rod can be obtained.

[0008] In the formula, E is the center point of the spherical joint, the coordinates of E are x E , y E , and z E), F is the center point of the cross axis hooke joint, and its initial coordinates are EF is the length between the spherical hinge and the cross axis hooke joint; is the pitch angle, and ψ is the yaw angle.

[0009] Compared with the prior art, the significant advantages of the present application are:

[0010] The gun parallel mechanism of the present application provides a posture control method, which uses the description method of Euler angle, direction vector and rotation matrix to quickly and accurately determine the relationship between the weapon posture direction and the length of the servo push rod in the parallel mechanism, and provides a high-efficiency and stable method for the intelligent attack of the gun. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 is the overall structure diagram of the parallel mechanism.

[0012] Figure 2 is the definition diagram of the Cartesian coordinate system of the mechanism.

[0013] Figure 3 is the schematic diagram of the length control of the servo push rod.

[0014] Figure 4 is the schematic diagram of the vector representation of the gun aiming direction. DETAILED DESCRIPTION

[0015] The following is a further description of the control method proposed by the present application in combination with the drawings and the mechanism principle diagram.

[0016] The main components of the gun parallel mechanism include a rack 1, a vertical hooke joint 2, a gun platform 3, cross axis hooke joints 4 and 5, servo push rods 6 and 7, spherical hinges 8 and 9. The overall layout diagram of the mechanism is shown in the accompanying Figure 1 The connection relationship between each mechanism is as follows:

[0017] The vertical hooke joint 2 is connected with the rack 1, and the gun platform 3 is connected with the vertical hooke joint 2. The gun platform 3 can perform two-degree-of-freedom motion of pitch and yaw with the center of the vertical hooke joint 2 as the rotation axis. Meanwhile, the gun platform 3 is also connected with the two servo push rods 6 and 7 through the cross axis hooke joints 4 and 5, and the other end of the push rod is connected with the rack 1 through the spherical hinges 8 and 9. The relative distance between the outer shell of the push rod and the elongated end of the push rod changes, which drives the relative distance between the cross axis hooke joints 4 and 5 and the spherical hinges 8 and 9 to change. And through the degree of freedom restriction of the push rods 6 and 7, the cross axis hooke joints 4 and 5 and the spherical hinges 8 and 9 in the parallel structure, the conversion from the linear motion of the push rod to the two-degree-of-freedom rotation of the weapon platform is completed. According to the K-G formula, the degree of freedom of the entire mechanism is M, the total number of components is n, the number of kinematic pairs is g, and the degree of freedom of the i th kinematic pair is f iThe mechanism has two prismatic joints, three two-degree-of-freedom rotational joints, and two three-degree-of-freedom rotational joints. Therefore, the degrees of freedom of the mechanism can be expressed as:

[0018]

[0019] Based on the degree of freedom analysis, the linear motion of push rods 6 and 7 can be converted into the two-degree-of-freedom yaw and pitch motion requirements of the gun platform 3.

[0020] The weapon attitude control method is explained in detail below:

[0021] 1) Definition of the spatial coordinate system of the weapon's position and attitude

[0022] Assume that the firearm is initially placed horizontally in space. Establish a Cartesian coordinate system as follows: with the center of rotation of the vertical Hooke's hinge 2 as the origin, the aiming direction of the firearm barrel as the positive x-axis, the vertically upward direction perpendicular to the ground as the positive z-axis, and the direction perpendicular to the xOz plane as the y-axis. The definitions of the positive x, y, and z axes satisfy the rules of a right-handed coordinate system. The Cartesian coordinate system is attached. Figure 2 As shown.

[0023] 2) Conversion from Euler angles to rotation matrix

[0024] In this mechanism, the rotation center of the firearm platform 3 is the center point of the vertical Hooke's hinge, which is also the origin of the coordinate system. Due to the structural constraints of the vertical Hooke's hinge in the parallel mechanism, the moving body completes yaw motion around the z-axis, which is perpendicular to the ground; and then completes pitch motion around the y-axis, which is parallel to the ground. The pitch and yaw motions determine the firearm's attitude, and consequently, the aiming direction of the barrel axis. This invention proposes a method using Euler angles to describe the pitch and yaw rotations of the firearm platform, and a direction vector to describe the aiming direction of the firearm barrel.

[0025] The Euler angle method for representing rotation involves dividing rotation into a combination of three rotational motions: roll, pitch, and yaw. Yaw is defined as rotation about the z-axis, pitch as rotation about the y-axis, and roll as rotation about the x-axis. The angles of roll, pitch, and yaw are denoted by θ, φ, and yaw respectively. ψ represents the positive direction of the angle. The positive direction is defined using the right-hand rule: when the four fingers of the right hand are extended and rotated around the positive direction of the angle, the thumb points in the positive direction of the coordinate axis. Based on the above definition of Euler angles, the rotation matrices representing roll, pitch, and yaw are respectively...

[0026]

[0027] Rot x (θ) Rot z(ψ) represents the rotation matrices for roll, pitch, and yaw, respectively. If Euler angles are defined by external rotation, following the order of roll-pitch-yaw, the entire rotation matrix R can be expressed as a matrix multiplication.

[0028]

[0029] In this problem, the weapon platform does not roll, θ = 0. Therefore, matrix multiplication can be performed to obtain...

[0030]

[0031] Where I is a third-order identity matrix. This formula represents the expression, given a pitch angle of rotation... For both the yaw angle ψ and the rotation angle ψ, there is a corresponding rotation matrix R. This is the correspondence between Euler angles and rotation matrices.

[0032] 3) Correspondence between the aiming direction of the firearm and the rotation matrix

[0033] The direction of the gun barrel axis is represented by a direction vector. This direction vector is v = (α, β, γ). T This represents the direction of any barrel axis. Assume that at the initial position, this direction vector is v0 = (α0, β0, γ0). T Then after pitching Given the angle and yaw angle ψ, the direction vector becomes v = (α, β, γ). T Then there is

[0034]

[0035] In this problem, the initial weapon orientation is v0 = (1, 0, 0). T Then the pitch calculation starts from the initial position. Given the angle and yaw angle ψ, the direction of the weapon's attitude after rotation is...

[0036]

[0037] This direction vector is the direction in which the barrel axis points. (See attached image) Figure 3 As shown. Considering the above two equations, we can obtain the direction vector v = (α, β, γ) for any orientation of the gun platform. T Euler angles The relationship with ψ, that is

[0038]

[0039] This formula shows that for any given aiming direction of a firearm, there is one and only one definite elevation angle. This corresponds to the yaw angle ψ.

[0040] 4) Conversion from rotation matrix to push rod length

[0041] In this system, the rotation of the gun platform to a certain position is controlled by the length of the servo push rod. Therefore, in the actual solution, we want to infer the push rod extension length through the rotation angle to achieve the purpose of controlling the arbitrary attitude of the gun.

[0042] Consider the hinges at both ends of the push rod, which are cross-axis hooke joints 4, 5 and ball joints 8, 9. Since their centers of rotation are fixed relative to the positions of the two ends of the push rod, we only need to consider the spatial position changes of the center points of the cross-axis hooke joints and ball joints during the movement. The change in the distance between the center points of the cross-axis hooke joints and ball joints reflects the extension and contraction of the servo push rod. Since the two push rods are symmetrically arranged in the mechanism, the method of analyzing the relationship between the extension amount and the rotation angle of the two push rods is the same.

[0043] Take one of the push rods as the analysis object. Let the center points of the cross-axis hooke joints and ball joints at both ends of this push rod be E and F, respectively. E is the center point of the ball joint fixed to the rack, and its spatial position remains unchanged during rotation. F is the center point of the cross-axis hooke joint fixed to the gun platform, and its spatial position changes with rotation. As shown in the accompanying Figure 4 Assume that in the Cartesian coordinate system described above, the coordinates of the fixed point E are E(x E , y E , z E ), and the coordinates of the moving point F change with rotation as F(x F , y F , z F ). The initial coordinates of F are Then the relationship between the length EF and the rotation angle between the two hinges is as follows

[0044]

[0045]

[0046] That is

[0047]

[0048] In the formula, the coordinates of point E are E(x E , y E , z E ), the initial coordinates of point F are , and the pitch angle and the yaw angle ψ are known values. Calculate the required EF length, then subtract the length of EF when the push rod is retracted to the shortest length, and you can obtain the required extension amount of this servo push rod. The analysis method for the other push rod is the same and will not be repeated.

Claims

1. A posture control method of a parallel mechanism for a gun, characterized by, By setting a vertical hooke joint and two ball joints on the rack, a servo push rod is arranged on each ball joint, the servo push rod is connected with the gun platform through a cross shaft hooke joint, and the gun platform is also connected with the vertical hooke joint; the elongation of the servo push rod is controlled to control the pitch angle and the yaw angle of the gun platform, so that the purpose of controlling the gun posture is achieved, and the following purposes are met: Calculate the required EF length, then subtract the EF length when the push rod is shortened to the shortest, and the required elongation of the servo push rod can be obtained; where E is the center point of the spherical hinge with coordinates E(x E ,y E ,z E ), F is the center point of the cross-axis hinge with initial coordinates EF is the length between the spherical hinge and the cross-axis hinge; is the pitch angle, and ψ is the yaw angle.

2. The attitude control method of a parallel link mechanism for a gun according to claim 1, characterized in that, The EF length calculation process is as follows: Step 1, define the spatial coordinate system of the gun position and posture: Taking the rotation center of the vertical hooke joint as the origin, taking the aiming direction of the gun barrel as the positive direction of x axis, taking the vertical upward direction perpendicular to the earth as the positive direction of z axis, and taking the direction perpendicular to the xOz plane as the y axis direction, a right-handed Cartesian coordinate system is established; Step 2, describe the gun platform pitch rotation and yaw rotation by using Euler angles, and describe the aiming direction of the gun barrel by using a direction vector, so as to obtain the corresponding relationship between Euler angles and rotation matrix; Step 3, according to the corresponding relationship between Euler angles and rotation matrix, the corresponding relationship between the gun aiming direction and the pitch angle and the yaw angle is obtained; Step 4, conversion from rotation matrix to push rod length: According to the relationship between the length EF and the rotation angle between the cross-axis Hooke joint and the ball joint, the EF length and the pitch angle are calculated The relationship of the yaw angle ψ.

3. The attitude control method of a parallel link mechanism for a gun according to claim 2, characterized in that, The corresponding relationship between the gun aiming direction and the pitch angle and the yaw angle satisfies: Define the direction vector v = (α, β, γ) T Indicates the direction of any barrel axis.

4. The attitude control method of a parallel link mechanism for a gun according to claim 2, characterized in that, The rotation matrices of roll, pitch and yaw rotation are respectively The whole rotation matrix R is: θ is the roll angle.

5. The attitude control method of a parallel link mechanism for a gun according to claim 4, characterized in that, When the roll angle θ = 0, the whole rotation matrix R is: Wherein I is a three-order unit matrix.

Images