A control allocation method for a tiltwing eVTOL

Abstract

This invention discloses a control allocation method for tilt-wing eVTOL aircraft, comprising the following steps: First, from the tail to the nose, assign wing numbers to the aircraft's wings; second, define the control variable and the controlled variable, and obtain the control efficiency matrix of the control variable based on the control variable and the controlled variable; then, set a reference value for the dynamic tilt angle related to airspeed, and define an objective function; finally, redistribute the control variable according to the tilt angle reference value and the objective function to complete the control of the aircraft's acceleration and angular acceleration. This tilt-wing eVTOL control allocation method is applicable to eVTOL aircraft that use rotor and dynamic tilt angle as control variables. It not only allows the dynamic tilt angle to change with airspeed but also enables it to participate in control allocation, taking into account the relationship between tilt angle and airspeed during transitions, thereby better realizing the allocation of angular acceleration and acceleration commands.

Description

Technical Field

[0001] This invention belongs to the field of multi-rotor control allocation, and specifically relates to a control allocation method for tilt-wing eVTOL. Background Technology

[0002] Current control allocation methods are mainly designed for multi-rotor aircraft, lacking specific control allocation methods for tilt-powered configurations, especially for aircraft that use the power tilt angle as the control variable.

[0003] Traditional tilt-powered eVTOL aircraft adjust the powered tilt angle according to airspeed during tilting, but do not participate in control allocation, resulting in low efficiency in allocating angular acceleration and acceleration commands. Summary of the Invention

[0004] Objective of the Invention: To overcome the above shortcomings, the objective of this invention is to provide a control allocation method for tilt-wing eVTOL aircraft. This control allocation is applicable to eVTOL aircraft that use rotor and powered tilt angle as control variables (even those without control surfaces typical of fixed-wing aircraft). It enables the powered tilt angle to participate in control allocation while also taking into account the relationship between tilt angle and airspeed during transitions.

[0005] Technical Solution: To achieve the above objectives, this invention provides a control allocation method for tilt-wing eVTOL, comprising the following steps: S1): Assigning wing numbers to the aircraft's wings from the tail to the nose; S2): Defining the control variable and the controlled variable, and obtaining the control efficiency matrix B of the control variable based on the control variable and the controlled variable. ce S3): Set a reference value for the dynamic tilt angle related to airspeed and define the objective function; S4): Redistribute the control variables according to the tilt angle reference value and the objective function to complete the control of the aircraft's acceleration and angular acceleration.

[0006] Furthermore, in S1, the wing numbers are set from the tail to the nose, with the left front wing designated as wing number 1, the right front wing as wing number 2, the left rear wing as wing number 3, and the right rear wing as wing number 4. Numbering the wings facilitates the definition of subsequent variables.

[0007] Furthermore, S2 defines the control variable, the controlled variable, and the control efficiency matrix of the control variable, including: S201): defining the control variable, which is u; S202): defining the controlled variable and obtaining the control instruction d to be assigned. c S203): Calculate the control efficiency matrix of the control variable. Control efficiency is systematically defined by defining the control variable and the controlled variable.

[0008] Furthermore, in S201, the control quantity u = [θ1 θ2 θ3 θ4 w1 w2 w3 w4], where θ1, θ2, θ3, and θ4 represent the tilt angles of wings 1 to 4, respectively, and w1, w2, and w3... w The numbers 4 represent the rotor speeds on wings 1 through 4, respectively. Different wings correspond to different tilt angles and rotor speeds, allowing for better control and distribution.

[0009] Furthermore, the specific operation of S202 includes: defining the controlled variable as forward acceleration A. x Vertical acceleration A z and roll, pitch, and yaw angular accelerations. The control command to be assigned is d c , The suffix 'c' indicates a command, which is the expectation of the current state calculated in real time by the flight control algorithm in the flight controller. Five controlled variables are set, allowing for control allocation from multiple perspectives.

[0010] Furthermore, the specific operation of step 203 includes: defining the control efficiency matrix of the control quantity as B. ce B ce The following equation must be satisfied:

[0011]

[0012] The control efficiency matrix is ​​B ce It can intuitively demonstrate its control efficiency and provide numerical reference for optimization.

[0013] Furthermore, S3 sets a reference value for the dynamic tilt angle related to airspeed, and defines the objective function including: S301): setting the i-th dynamic tilt angle θ ip There is a linear relationship between the tilt velocity and the airspeed v, where i∈{1,2,3,4}; the tilt initiation velocity for the i-th dynamic tilt angle is defined as v. ib The tilting end speed is v ie The tilting start angle is θ ib The tilting end angle is θ ie The dynamic tilt angle θ is obtained. ip The relationship with airspeed v is as follows:

[0014]

[0015] The reference value of the corresponding control quantity at this time is u. p u p The expression is as follows:

[0016] u p =[θ 1p θ 2pθ 3p θ 4p w 1p w 2p w 3p w 4p ]

[0017] Among them, w 1p w 2p w 3p w 4p It can be set to trim speed commands at different speeds;

[0018] S302): Define the objective function J. Including airspeed in the control allocation is more realistic.

[0019] Furthermore, the specific operation of S302 includes: defining the objective function J, as follows:

[0020]

[0021] Among them, u p The reference value for the control variable u is indicated; the reference values ​​for the four tilt angles can be set to reasonable tilt angle values ​​related to airspeed; W u This represents the weight coefficient matrix for each channel, typically a diagonal matrix. The objective function is defined, transforming the abstract problem into a concrete mathematical solution for easier resolution.

[0022] Furthermore, the specific operation of S4 includes: obtaining a minimization problem based on the objective function J, and calculating an analytical solution; the minimization problem is as follows:

[0023]

[0024] subject to B Ce *u=d c

[0025] Where subject to represents the constraint condition, B ce Let d be the control efficiency matrix for the control quantity, where u is the control quantity and d is the control efficiency matrix. c Control commands to be assigned;

[0026] The analytical solution to the minimization problem is calculated as follows:

[0027]

[0028] in:

[0029]

[0030] in, W is the weight coefficient matrix for each channel. u The inverse matrix, Bce This is the control efficiency matrix for the control quantity. The control efficiency matrix B for the control quantity ce The transpose of the above formula must ensure that... It is full rank; the reference value of the control variable u can be obtained from the airspeed v. p Under the constraint of this reference value, the tilt angle participates in the control allocation as a control variable, ultimately realizing the control command d to be allocated. c The allocation of resources is optimized. By solving the minimization problem analytically, the iterative convergence problem and local optima that may occur in numerical methods are avoided, ensuring the accuracy and global optimality of the solution.

[0031] As can be seen from the above technical solution, the present invention has the following beneficial effects:

[0032] The purpose of this invention is to provide a control allocation method for tilt-wing eVTOL aircraft. This control allocation method is applicable to eVTOL aircraft that use rotor and powered tilt angle as control variables (even those without control surfaces of traditional fixed-wing aircraft). It not only allows the powered tilt angle to change with airspeed, but also enables it to participate in control allocation. It takes into account the relationship between tilt angle and airspeed during the transition process, thereby better realizing the allocation of angular acceleration and acceleration commands. Attached Figure Description

[0033] Figure 1 This is a flowchart of a control allocation method for tiltwing eVTOL as described in this invention;

[0034] Figure 2 This is a schematic diagram of a tilt-powered eVTOL aircraft, which is a control allocation method for tilt-wing eVTOL according to the present invention. Detailed Implementation

[0035] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0036] Example 1

[0037] In this embodiment, as Figure 1 This invention discloses a control allocation method for tilt-wing eVTOL, comprising the following steps: S1): Assigning wing numbers to the aircraft's wings from the tail to the nose; S2): Defining the control variable and the controlled variable, and obtaining the control efficiency matrix B of the control variable based on the control variable and the controlled variable. ceS3): Set a reference value for the dynamic tilt angle related to airspeed and define the objective function; S4): Redistribute the control variables according to the tilt angle reference value and the objective function to complete the control of the aircraft's acceleration and angular acceleration.

[0038] Example 2

[0039] Based on Example 1, this embodiment discloses a control allocation method for tilt-wing eVTOL, assuming that the controlled tilt-powered eVTOL aircraft has only controllable power tilt angle and rotor, such as... Figure 2 The tilt angles of its four wings are controllable, and the thrust of its ten rotors is controllable (either rotational speed or collective pitch is controllable; in this embodiment, rotational speed is the control variable). The tilt angle is 90 degrees when the wings are perpendicular to the ground and 0 degrees when they are parallel to the ground. There is also a constraint: in rotor mode, the wing tilt angle is close to vertical (90 degrees) to ensure that the rotor thrust is as perpendicular to the horizontal plane as possible, thus providing greater vertical thrust to counteract gravity and less horizontal thrust. In fixed-wing mode, the wing tilt angle is close to horizontal (0 degrees). This is because in fixed-wing mode, the rotor thrust is mainly used to counteract horizontal drag, while the lift to counteract gravity is mainly provided by the wings. In the intermediate state between the two modes, the wing tilt angle gradually changes. This tilt angle affects the distribution of rotor power in the horizontal and vertical directions, and the lift generated by the wings and the overall drag of the aircraft are related to airspeed. Therefore, this tilt angle needs to be varied in conjunction with airspeed. A smaller tilt angle is needed when airspeed is high, and a larger tilt angle is needed when airspeed is low, in order to ensure overall aircraft trim. In S1, the wing numbers are set as follows: left front wing is wing number 1, right front wing is wing number 2, left rear wing is wing number 3, and right rear wing is wing number 4, viewed from the tail towards the nose.

[0040] In this embodiment, as Figure 1 and Figure 2 The S2 definition of the control variable, the controlled variable, and the control efficiency matrix of the control variable includes: S201): defining the control variable, wherein the control variable is u; S202): defining the controlled variable and obtaining the control instruction d to be assigned. c S203): Calculate the control efficiency matrix of the control quantity.

[0041] In this embodiment, as Figure 1 and Figure 2 In S201, the control quantity u = [θ1 θ2 θ3 θ4 w1 w2 w3 w4], where θ1, θ2, θ3, and θ4 represent the tilt angles of wings 1 to 4, and w1, w2, w3, and w4 represent the rotor speeds of wings 1 to 4, respectively.

[0042] In this embodiment, as Figure 1 and Figure 2 The specific operation of S202 includes: defining the controlled variable as forward acceleration A. x Vertical acceleration A z and roll, pitch, and yaw angular accelerations. The control command to be assigned is d c , The suffix 'c' indicates a command, which is the expectation of the current state calculated in real time by the flight control algorithm in the flight controller.

[0043] In this embodiment, as Figure 1 and Figure 2 The specific operation of S203 includes: setting the control efficiency matrix of the control quantity as B. ce It satisfies the following equation:

[0044]

[0045] In this embodiment, as Figure 1 and Figure 2 Since the dynamic tilt angle command serves as both a control variable and is related to airspeed, the control allocation algorithm can set a dynamic tilt angle reference value related to airspeed, and then redistribute the control variable based on this tilt angle reference value. Step S3 sets an airspeed-related dynamic tilt angle reference value and defines the objective function, including:

[0046] S301): Set the i-th dynamic tilt angle θ ip There is a linear relationship between the tilt velocity and the airspeed v, where i∈{1,2,3,4}; the tilt initiation velocity for the i-th dynamic tilt angle is defined as v. ib The tilting end speed is v ie The tilting start angle is θ ib The tilting end angle is θ ie The dynamic tilt angle θ is obtained. ip The relationship with airspeed v is as follows:

[0047]

[0048] The reference value of the corresponding control quantity at this time is u. p u p The expression is as follows:

[0049] u p =[θ 1p θ 2p θ 3p θ 4p w 1p w 2p w3p w 4p ]

[0050] Among them, w 1p w 2p w 3p w 4p It can be set to trim speed commands at different speeds;

[0051] It should be noted that the i-th dynamic tilt angle θ is set. ip A linear relationship with airspeed v is only the preferred option; the i-th dynamic tilt angle θ ip A curve showing the relationship between airspeed v and tilting speed is required, and this curve must fall within the tilting corridor.

[0052] S302): Define the objective function J.

[0053] In this embodiment, as Figure 1 and Figure 2 The specific operation of S302 includes: defining the objective function J, as follows:

[0054]

[0055] Among them, u p The reference value for the control variable u is indicated; the reference values ​​for the four tilt angles can be set to reasonable tilt angle values ​​related to airspeed; W u The matrix represents the weighting coefficients for each channel. In this embodiment, there are 8 control channels, corresponding to 4 tilt angles and 4 rotor speeds. Therefore, the weighting coefficient matrix is ​​an 8x8 matrix. Furthermore, it is assumed that the influence of each channel is uncoupled, so W... u It is a diagonal matrix; these weighting coefficients need to be obtained through debugging and tuning based on engineering experience and analysis of the controlled object.

[0056] In this embodiment, as Figure 1 and Figure 2 The specific operation of S4 includes: obtaining a minimization problem based on the objective function J, and calculating an analytical solution; the minimization problem is as follows:

[0057]

[0058] Subject to B Ce *u=d c

[0059] Where subject to represents the constraint condition, B ce Let d be the control efficiency matrix for the control quantity, where u is the control quantity and d is the control efficiency matrix. c Control commands to be assigned;

[0060] The analytical solution to the minimization problem is calculated as follows:

[0061]

[0062] in:

[0063]

[0064] in, W is the weight coefficient matrix for each channel. u The inverse matrix, B ce This is the control efficiency matrix for the control quantity. The control efficiency matrix B for the control quantity ce The transpose of the above formula must ensure that... It is full rank; the reference value of the control variable u can be obtained from the airspeed v. p Under the constraint of this reference value, the tilt angle participates in the control allocation as a control variable, ultimately realizing the control command d to be allocated. c The allocation.

[0065] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements can be made without departing from the principle of the present invention, and these improvements should also be considered within the scope of protection of the present invention.

Claims

1. A control allocation method for tiltwing eVTOL, characterized in that: Includes the following steps: S1): Assign wing numbers to the aircraft's wings when viewed from the tail to the nose. S2): Define the control variable and the controlled variable, and obtain the control efficiency matrix B of the control variable based on the control variable and the controlled variable. ce ,include: S201): Define the control quantity, which is u = [θ1 θ2 θ3 θ4 w1 w2 w3 w4], where θ1, θ2, θ3, θ4 represent the dynamic tilt angles of wings 1 to 4 respectively, and w1, w2, w3, w4 represent the rotor speeds of wings 1 to 4 respectively. S202): Define the controlled variable and obtain the control instruction d to be assigned. c This includes: defining the controlled variable as the forward acceleration A. x Vertical acceleration A z and roll, pitch, and yaw angular accelerations. Receive control instructions to be assigned Wherein, the suffix 'c' indicates a command, that is, the expectation of the current state calculated in real time by the flight control algorithm in the flight controller; S203): Calculate the control efficiency matrix of the control quantity, including: Let B be the control efficiency matrix of the control quantity. ce The following equation must be satisfied: S3): Set a reference value for the dynamic tilt angle related to airspeed, and define the objective function, including: S301): Set the i-th dynamic tilt angle θ ip There is a linear relationship between the tilt velocity and the airspeed v, where i∈{1,2,3,4}; the tilt initiation velocity for the i-th dynamic tilt angle is defined as v. ib The tilting end speed is v ie The tilting start angle is θ ib The tilting end angle is θ ie The dynamic tilt angle θ is obtained. ip The relationship with airspeed v is as follows: The reference value of the corresponding control quantity at this time is u. p u p The expression is as follows: you p =[θ 1p i 2p i 3p i 4p w 1p w 2p w 3p w 4p ] Among them, w 1p w 2p w 3p w 4p It can be set to trim speed commands at different speeds; S302): Define the objective function J; S4): Based on the dynamic tilt angle reference value and the objective function, the control variables are redistributed to complete the control of the aircraft's acceleration and angular acceleration.

2. The control allocation method for tiltwing eVTOL according to claim 1, characterized in that: In S1, the wing numbers are set as follows: when viewed from the tail to the nose, the left front wing is set as wing number 1, the right front wing as wing number 2, the left rear wing as wing number 3, and the right rear wing as wing number 4.

3. The control allocation method for tiltwing eVTOL according to claim 2, characterized in that: The specific operations of S302 include: Define the objective function J as follows: Among them, u p The reference value for the control variable u is indicated; the reference values ​​for the four dynamic tilt angles can be set to reasonable values ​​for the dynamic tilt angles related to airspeed; W u The weight coefficient matrix for each channel is a diagonal matrix.

4. The control allocation method for tiltwing eVTOL according to claim 3, characterized in that: The specific operations of S4 include: The minimization problem is derived based on the objective function J, and the analytical solution is calculated. The minimization problem is as follows: subject to B ce *u=d c Where subject to represents the constraint condition; The analytical solution to the minimization problem is calculated as follows: in: in, W is the weight coefficient matrix for each channel. u The inverse matrix, The control efficiency matrix B for the control quantity ce The transpose of the above formula must ensure that... It is full rank; the reference value of the control variable u can be obtained from the airspeed v. p Under the constraint of this reference value, the dynamic tilt angle participates in the control allocation as a control variable, ultimately realizing the control command d to be allocated. c The allocation.

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