Lift force and torque direct closed-loop control and fault-tolerant operation method and device for six-rotor aircraft

Abstract

The invention discloses a lift force and torque direct closed-loop control and fault-tolerant operation method and device for a six-rotor aircraft. By using the controller obtained by the invention, an optimal current instruction can be directly obtained from a lift instruction and a torque instruction, and a traditional cascaded rotating speed calculation module and a plurality of rotating speed controllers are uniformly replaced; the obtained control system can realize direct closed-loop control of the lift force and the torque, not only significantly improves the dynamic performance of the lift force and the torque, but also integrates the rotating speed resolving process using the aerodynamic parameters into the controller, and can eliminate the steady-state static error caused by mismatch of the aerodynamic parameters by means of an auxiliary disturbance observer. The steady-state control precision and the system robustness of the lift force and the torque are enhanced; and finally, for different fault modes, reconstructing a fault prediction model, a fault controller and a fault-tolerant operation control system suitable for different faults, so that excellent fault-tolerant operation of the multi-rotor aircraft in some fault modes is ensured, and the safety and reliability of operation of the multi-rotor aircraft are improved.

Description

Technical Field

[0001] The present invention belongs to the field of aircraft control, and in particular relates to a method and device for direct closed-loop control and fault-tolerant operation of lift and torque of a six-rotor aircraft. Background Art

[0002] Multirotor aircraft are widely used in agriculture, military, industry, commerce and other fields due to their small size, low cost, flexible operation and vertical take-off and landing. They perform tasks such as plant protection, irrigation, reconnaissance, rescue, mapping, logistics and have broad application prospects. Among them, hexarotor and octorotor aircraft can use the redundancy of actuators for fault-tolerant control and have stronger load-bearing capacity, which has attracted widespread attention. The research on their high dynamics and safe and reliable flight is of great value.

[0003] The traditional trajectory following control of multi-rotor aircraft includes two levels of control: upper-level flight control and lower-level motor control. The task of the upper-level flight control part is to adjust the position and attitude of the multi-rotor aircraft to achieve three-dimensional trajectory following; the flight controller outputs lift instructions and body roll moment instructions, pitch moment instructions, and yaw moment instructions. The lower-level motor control part provides power for the multi-rotor aircraft and is the actuator of the upper-level instructions. It generates the lift and roll moment, pitch moment, and yaw moment required by the upper level by controlling the speed of multiple permanent magnet synchronous motors respectively.

[0004] The flight control and motor control are connected through a speed solver module. The speed solver module solves the lift command, rolling moment command, pitch moment command and yaw moment command into speed commands for the four motors based on aerodynamics and quadrotor dynamics.

[0005] However, this traditional indirect control method of lift and rolling moment, pitch moment, and yaw moment cascade has the problems of poor dynamic performance, low robustness of aerodynamic parameters, and insufficient fault-tolerant operation capability. Summary of the invention

[0006] In order to solve the problems of poor system dynamic performance and low robustness of aerodynamic parameters caused by the existing cascade and indirect lift and roll moment, pitch moment, and yaw moment control methods, the present invention proposes a method and device for direct closed-loop control and fault-tolerant operation of lift and torque of a six-rotor aircraft. The present invention designs an explicit model-predicted direct lift and torque controller, constructs a linear robust prediction model of lift and torque of a six-rotor aircraft, and realizes high dynamic, high precision, strong robustness control of lift and torque and excellent fault-tolerant operation of multi-rotor aircraft.

[0007] The technical solution provided by the present invention is as follows:

[0008] In a first aspect, the present invention provides an explicit model predictive direct lift and torque controller, the controller being applicable to hexarotor and octorotor aircraft, the controller comprising:

[0009] A definition module is used to split the q-axis current of each motor into four components for independently controlling lift, rolling moment, pitching moment and yaw moment. According to the working principle of multi-rotor aircraft, the current components with the same effect are superimposed according to the action weights and defined as lift current and rolling moment current, pitching moment current and yaw moment current;

[0010] A prediction model module is used to construct a linear robust prediction model of the lift and torque of the six-rotor aircraft according to the defined lift current and rolling moment current, pitch moment current, and yaw moment current;

[0011] The value function and linear constraint module of lift and torque is used to obtain the value function and linear constraint of lift and torque by setting the weight coefficient of current increment and the constraint value of current;

[0012] The execution module is used to construct an explicit model predictive direct lift and torque controller based on a linear robust prediction model of lift and torque of a hexacopter, value functions of lift and torque, and linear constraints.

[0013] In one implementation, the corresponding relationship between the lift current, the rolling moment current, the pitching moment current, the yaw moment current and the six motor currents is:

[0014]

[0015] Among them, i qk (k=1, 2, 3, 4, 5, 6) represents the q-axis current component of the k-th motor; i qU is the lift current defined, is the defined rolling torque current, i qθ is the pitch moment current, i qψ is the defined yaw moment current; i qkf Defined as i qk The components of f are generated in (subscript k = 1, 2, 3, 4, 5, 6 represent the kth motor, subscript f = U, θ, ψ represent lift, rolling moment, pitching moment and yaw moment respectively);

[0016] The definition expressions of lift current, rolling moment current, pitch moment current and yaw moment current are:

[0017]

[0018] Among them, st is the mathematical symbol that satisfies.

[0019] In one embodiment, constructing a linear robust prediction model of lift and torque of a hexacopter includes:

[0020] The linear robust prediction model of lift is:

[0021]

[0022] Among them, x U is the state variable of the prediction model; Δi qU is the control variable of the prediction model; x U (k) and x U (k+1) are the state variables of the prediction model at the kth discrete moment and the k+1th discrete moment, respectively, k is a natural number; Δi qU (k) is the control variable of the prediction model at the kth discrete moment. U is the lift; U ref is the lift command value; T s is the control period; K U is the lift proportional constant, satisfying K U =2T s K b0 k t0 J r0 -1 Ω, where K b0 is the rotor thrust coefficient K b The nominal value of k t0 is the motor torque constant k t The nominal value, J r0 is the motor rotor inertia J r The nominal value of Ω is the preset speed constant; is the lift disturbance term d in the prediction model U The observed value, d U The specific equations satisfied are:

[0023]

[0024] Among them, ω k is the mechanical angular velocity of the kth motor; d ωk The speed disturbance terms of viscous friction and rotor inertia mismatch are considered for the kth motor; B m is the viscous friction coefficient of the motor; T Lk is the windage load torque of the kth motor; ∑ is the summation symbol;

[0025] The linear robust prediction model of rolling moment, pitching moment and yaw moment is:

[0026]

[0027] Where f = U, θ, ψ represent the rolling moment, pitching moment and yaw moment respectively; the proportional constants of rolling, pitching and yaw moments are K θ =2LK b0 k t0 J r0 -1 ΩT s , K ψ =2K d0 k t0 J r0 -1 ΩT s ; The specific equations satisfied by the rolling, pitching, and yaw moment disturbance terms are:

[0028]

[0029] in, is the rolling moment disturbance term; d θ is the pitching moment disturbance term; d ψ is the yaw moment disturbance term; L is the distance from the center of the six-rotor aircraft to the motor shaft; K d0 is the rotor anti-twist coefficient K d Nominal value.

[0030] In one embodiment, the lift and torque cost functions and linear constraints include:

[0031] The value function and linear constraints of lift are:

[0032]

[0033] Among them, J U is the lift value function; N p is the prediction time domain; q U and q i are the weight coefficients of lift and lift current increment respectively; I Umax is the constraint value of lift current;

[0034] The value functions and linear constraints of the rolling moment, pitching moment, and yaw moment are:

[0035]

[0036] Among them, J f is the moment value function; q f and q if are the weight coefficients of torque and torque current increment respectively; I fmax is the constraint value of torque current.

[0037] In one embodiment, the controller is further provided with an auxiliary disturbance observer for observing lift disturbance term, rolling moment disturbance term, pitch moment disturbance term and yaw moment disturbance term in real time, and feeding them forward to the explicit model prediction direct lift and torque controller.

[0038] In a second aspect, the present invention provides a method for direct closed-loop control and fault-tolerant operation of lift and torque of a six-rotor aircraft, the method comprising the following steps:

[0039] The above explicit model predicts direct lift and torque controller to achieve direct closed-loop control of lift and torque;

[0040] Based on the realization of direct closed-loop control of lift and torque, a fault prediction model, fault controller and fault-tolerant operation control are developed for the hexacopter according to its different failure modes.

[0041] In one embodiment, an explicit model predicts a direct lift and torque controller directly obtains the optimal lift current command, roll torque current command, pitch torque current command and yaw torque current command from the lift command, roll torque command, pitch torque command and yaw torque command to uniformly replace the traditional cascade speed solver module and multiple motor speed controllers to achieve direct closed-loop control of lift and torque.

[0042] In one embodiment, the fault prediction model, fault controller and fault-tolerant operation control of the six-rotor aircraft according to different fault modes include:

[0043] When the No. 1 motor of the hexacopter fails:

[0044] First, the No. 1 motor and the symmetrical No. 4 motor are stopped at the same time, and the remaining No. 2, No. 3, No. 5 and No. 6 motors continue to work to achieve fault-tolerant operation;

[0045] This fault mode is recorded as g1. At this time, the corresponding relationship between the g1 lift current, g1 rolling moment current, g1 pitch moment current and g1 yaw moment current and the motor current involved in fault-tolerant operation is:

[0046]

[0047] Among them, i qk (k=2, 3, 5, 6) represents the q-axis current component of the k-th motor; i qUg1 is the defined g1 lift current, is defined as the g1 rolling torque current, i qθg1 is defined as the pitch moment current g1, i qψg1 is the defined g1 yaw moment current; i qkfDefined as i qk The components of f are generated in (subscript k = 2, 3, 5, 6 represent the kth motor, subscript f = U, θ, ψ represent lift, rolling moment, pitching moment and yaw moment respectively);

[0048] The g1 lift current, g1 rolling moment current, g1 pitch moment current, and g1 yaw moment current of the six-rotor aircraft are defined as:

[0049]

[0050] In the g1 fault mode, the working mode of the six-rotor aircraft and the collaborative mode of the multi-motor system change accordingly. The g1 fault prediction model of the six-rotor aircraft lift is constructed as follows:

[0051]

[0052] Among them, x Ug1 is the state variable of the g1 fault prediction model; x Ug1 (k) and x Ug1 (k+1) are the state variables of the g1 fault prediction model at the kth discrete moment and the k+1th discrete moment respectively; Δi qUg1 is the control variable of the g1 fault prediction model at the kth discrete moment; is the g1 fault lift disturbance term d in the g1 fault prediction model Ug1 The observed value, d Ug1 The specific equations satisfied are:

[0053]

[0054] Under the g1 fault mode, the explicit model predicts the direct lift and torque. The cost function and linear constraints used by the g1 fault controller are designed as:

[0055]

[0056] Among them, J Ug1 is the lift value function of g1 fault mode; I Ug1max is the constraint value of lift current in g1 fault mode;

[0057] The value functions and linear constraints of the rolling moment, pitching moment, and yaw moment are:

[0058]

[0059] Among them, J f g1 is the moment value function of g1 fault mode; I f g1maxis the constraint value of the torque current in the g1 fault mode.

[0060] In a third aspect, the present invention provides a lift and torque direct closed-loop control and fault-tolerant operation device for a six-rotor aircraft, the device comprising:

[0061] A lift and torque direct closed-loop control system for realizing lift and torque direct closed-loop control using the above-mentioned explicit model predictive direct lift and torque controller;

[0062] The fault prediction model, fault controller and fault-tolerant operation control system are used to perform fault prediction model, fault controller and fault-tolerant operation control on the six-rotor aircraft based on the realization of direct closed-loop control of lift and torque and according to different fault modes of the six-rotor aircraft.

[0063] In a fourth aspect, the present invention provides a six-rotor aircraft control system, the system comprising the above-mentioned lift and torque direct closed-loop control and fault-tolerant operation device of the six-rotor aircraft.

[0064] Beneficial effects of the present invention:

[0065] (1) By defining the lift current and torque current of a multi-rotor aircraft, a new structure of the lift and torque controller is proposed: Under the new control structure, the multi-motor system is regarded as a whole, and the lift and torque current following is taken as the new control target to achieve direct closed-loop control of lift and torque, thereby improving the dynamic response speed of lift and torque.

[0066] (2) A linear robust prediction model of lift and torque is constructed, and an explicit model prediction direct lift and torque controller is designed based on it. This controller can directly obtain the optimal lift current and torque current instructions from the lift and torque instructions, and uniformly replaces the traditional cascade speed solution module and multiple speed controllers. Since the speed solution process using aerodynamic parameters is integrated into the controller, it is possible to compensate for the mismatch of aerodynamic parameters with the help of an auxiliary disturbance observer, eliminating the steady-state deviation of lift and torque and improving the steady-state control accuracy of lift and torque.

[0067] (3) The present invention provides a detailed construction method of a fault prediction model, a fault controller and a fault-tolerant control system applicable to fault-tolerant operation under different fault modes, which significantly enhances the safety and reliability of the multi-rotor aircraft. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] The accompanying drawings are part of the present invention and are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention, but do not constitute an improper limitation of the present invention. Obviously, the drawings described below are only some embodiments. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0069] Figure 1 A schematic diagram of the structure of an explicit model-predicted direct lift and torque controller provided by an embodiment of the present invention;

[0070] Figure 2 A flow chart of a method for direct closed-loop control and fault-tolerant operation of lift and torque of a six-rotor aircraft provided in one embodiment of the present invention;

[0071] Figure 3 A comparative effect diagram of lift and torque control of a six-rotor aircraft when aerodynamic parameters are mismatched in a healthy mode provided in an embodiment;

[0072] Figure 4 This is a diagram showing the effects of lift, torque and speed control for the fault-tolerant operation of a six-rotor aircraft in the No. 1 motor failure mode provided in an embodiment.

[0073] It should be noted that these drawings and textual descriptions are not intended to limit the conceptual scope of the present invention in any way, but are intended to illustrate the concept of the present invention for those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0074] In order to deepen the recognition and understanding of the present invention, the technical solution of the present invention is further introduced below in conjunction with the accompanying drawings and specific implementation methods. The following embodiments are explanations of the present invention and the present invention is not limited to the following embodiments.

[0075] The embodiment of the present invention provides an explicit model prediction direct lift and torque controller, which is suitable for six-rotor and eight-rotor aircraft, referring to Figure 1 As shown, the controller includes:

[0076] A definition module is used to split the q-axis current of each motor into four components for independently controlling lift, rolling moment, pitching moment and yaw moment. According to the working principle of multi-rotor aircraft, the current components with the same effect are superimposed according to the action weights and defined as lift current and rolling moment current, pitching moment current and yaw moment current;

[0077] A prediction model module is used to construct a linear robust prediction model of the lift and torque of the six-rotor aircraft according to the defined lift current and rolling moment current, pitch moment current, and yaw moment current;

[0078] The value function and linear constraint module of lift and torque is used to obtain the value function and linear constraint of lift and torque by setting the weight coefficient of current increment and the constraint value of current;

[0079] The execution module is used to construct an explicit model predictive direct lift and torque controller based on a linear robust prediction model of lift and torque of a hexacopter, value functions of lift and torque, and linear constraints.

[0080] In the embodiment of the present application, the corresponding relationship between the lift current, the rolling moment current, the pitching moment current and the yaw moment current and the six motor currents is:

[0081]

[0082] Among them, i qk (k=1, 2, 3, 4, 5, 6) represents the q-axis current component of the k-th motor, i qU is the lift current defined, is the defined rolling torque current, i qθ is the pitch moment current, i qψ is the defined yaw moment current; i qkf Defined as i qk The components of f are generated in (subscript k = 1, 2, 3, 4, 5, 6 represent the kth motor, subscript f = U, θ, ψ represent lift, rolling moment, pitching moment and yaw moment respectively).

[0083] Since the speed of each motor can be divided into four parts that generate lift, rolling moment, pitching moment and yaw moment separately; and the motor adjusts the speed by changing the q-axis current, the q-axis current of each motor can also be divided into several components that control lift, rolling moment, pitching moment and yaw moment separately; according to the working principle of multi-rotor aircraft, the current components with the same effect are superimposed according to the action weight, and defined as lift current and torque current. Define lift current and rolling moment current, pitching moment current, and yaw moment current.

[0084] Taking a six-rotor aircraft as an example, the definition expressions of its lift current and rolling moment current, pitch moment current, and yaw moment current are:

[0085]

[0086]

[0087] Among them, st is the mathematical symbol that satisfies.

[0088] Furthermore, based on the defined new variables, a linear robust prediction model of lift and torque of multirotor aircraft is constructed.

[0089] Taking the lift of a six-rotor aircraft as an example, the linear robust prediction model of lift is constructed as follows:

[0090]

[0091] Among them, x U is the state variable of the prediction model; Δi qU is the control variable of the prediction model; x U (k) and x U (k+1) are the state variables of the prediction model at the kth discrete moment and the k+1th discrete moment, respectively, k is a natural number; Δi qU (k) is the control variable of the prediction model at the kth discrete moment. U is the lift; U ref is the lift command value; T s is the control period; K U is the lift proportional constant, satisfying K U =2T s K b0 k t0 J r0 -1 Ω, where K b0 is the rotor thrust coefficient K b The nominal value of k t0 is the motor torque constant k t The nominal value, J r0 is the motor rotor inertia J r The nominal value of Ω is the preset speed constant; is the lift disturbance term d in the prediction model U The observed value, d U The specific equations satisfied are:

[0092]

[0093] Among them, ω k is the mechanical angular velocity of the kth motor; d ωk The speed disturbance terms of viscous friction and rotor inertia mismatch are considered for the kth motor; B m is the viscous friction coefficient of the motor; T Lk is the windage load torque of the kth motor; ∑ is the summation symbol.

[0094] The rolling moment, pitching moment and yaw moment have the same linear robust prediction model structure:

[0095]

[0096] Where f = U, θ, ψ represent the rolling moment, pitching moment and yaw moment respectively; the proportional constants of rolling, pitching and yaw moments are K θ =2LK b0 k t0 J r0 -1 ΩT s , K ψ =2K d0 k t0 J r0 -1 ΩT s ; The specific equations satisfied by the rolling, pitching, and yaw moment disturbance terms are:

[0097]

[0098] in, is the rolling moment disturbance term; d θ is the pitching moment disturbance term; d ψ is the yaw moment disturbance term; L is the distance from the center of the six-rotor aircraft to the motor shaft; K d0 is the rotor anti-twist coefficient K d Nominal value.

[0099] Furthermore, the value functions and linear constraints for lift and torque include:

[0100] The value function and linear constraints of lift are:

[0101]

[0102] Among them, J U is the lift value function; N p is the prediction time domain; q U and q i are the weight coefficients of lift and lift current increment respectively; I Umax is the constraint value of lift current.

[0103] The value functions and linear constraints of the rolling moment, pitching moment, and yaw moment are:

[0104]

[0105] Among them, J f is the moment value function; q f and q if are the weight coefficients of torque and torque current increment respectively; I fmax is the constraint value of torque current.

[0106] In an optional embodiment, the controller is also provided with an auxiliary disturbance observer for observing the lift disturbance term, the rolling moment disturbance term, the pitch moment disturbance term and the yaw moment disturbance term in real time, and feeding them forward to the explicit model prediction direct lift and torque controller.

[0107] Similarly, the octorotor aircraft refers to the hexacopter aircraft and constructs a linear robust prediction model of lift and torque suitable for the octorotor aircraft based on the defined new variables.

[0108] In one embodiment, a method for direct closed-loop control and fault-tolerant operation of lift and torque of a six-rotor aircraft is proposed, referring to Figure 2 As shown, the steps of this method are as follows:

[0109] Step S100: Using the above explicit model to predict the direct lift and torque controller to achieve direct closed-loop control of lift and torque.

[0110] Specifically, in this control method, the explicit model predicts the direct lift and torque controller directly from the lift command, the rolling torque command, the pitching torque command and the yaw torque command to obtain the optimal

[0111] The lift current command, the rolling torque current command, the pitch torque current command and the yaw torque current command are used to uniformly replace the traditional cascade speed solving module and multiple motor speed controllers to realize direct closed-loop control of lift and torque.

[0112] It should be noted that, because the control algorithm of the explicit model predicting direct lift and torque controller is an optimal control algorithm, the control law obtained by the explicit model predicting direct lift and torque controller is the optimal control law.

[0113] Optionally, an auxiliary disturbance observer is set to observe the lift disturbance term, the rolling moment disturbance term, the pitch moment disturbance term and the yaw moment disturbance term in real time, and feed it forward to the explicit model prediction direct lift and torque controller. The subsequent control of multiple motor currents is the same as the traditional control method.

[0114] Step S200: Based on the realization of direct closed-loop control of lift and torque, a fault prediction model, a fault controller and fault-tolerant operation control are performed on the six-rotor aircraft according to different failure modes of the six-rotor aircraft.

[0115] According to different failure modes, the six-rotor aircraft is subjected to fault prediction model, fault controller and fault-tolerant operation control, including:

[0116] Taking the failure of motor 1 of a six-rotor aircraft as an example, first, motor 1 and the symmetrical motor 4 are stopped at the same time, and the remaining motors 2, 3, 5 and 6 continue to work to achieve fault-tolerant operation. This failure mode is recorded as g1. At this time, the g1 lift current and g1 rolling moment current, g1 pitch moment current, and g1 yaw moment current of the six-rotor aircraft are defined as:

[0117]

[0118] Among them, i qUg1 is the defined g1 lift current, is defined as the g1 rolling torque current, i qθg1 is defined as the pitch moment current g1, i qψg1 is the defined g1 yaw moment current; i qkf Defined as i qk The components of f are generated in (subscript k = 2, 3, 5, 6 represent the kth motor, subscript f = U, θ, ψ represent lift, rolling moment, pitching moment and yaw moment respectively).

[0119] The corresponding relationship between the g1 lift current, g1 roll moment current, g1 pitch moment current and g1 yaw moment current and the motor current involved in fault-tolerant operation is:

[0120]

[0121] Among them, i qk (k=2, 3, 5, 6) represents the q-axis current component of the kth motor.

[0122] Under the g1 fault mode, the working mode of the six-rotor aircraft and the collaborative mode of the multi-motor system change accordingly. Based on this, the g1 fault prediction model of the six-rotor aircraft lift is constructed as follows:

[0123]

[0124] Among them, x Ug1 is the state variable of the g1 fault prediction model; x Ug1 (k) and x Ug1 (k+1) are the state variables of the g1 fault prediction model at the kth discrete moment and the k+1th discrete moment respectively; Δi qUg1 is the control variable of the g1 fault prediction model at the kth discrete moment. is the g1 fault lift disturbance term d in the g1 fault prediction model Ug1 The observed value, d Ug1 The specific equations satisfied are:

[0125]

[0126] Under the g1 fault mode, the explicit model predicts the direct lift and torque. The cost function and linear constraints used by the g1 fault controller are designed as:

[0127]

[0128] Among them, J Ug1 is the lift value function of g1 fault mode; I Ug1max is the constraint value of lift current for g1 fault mode.

[0129] The value functions and linear constraints of the rolling moment, pitching moment, and yaw moment are:

[0130]

[0131] Among them, J f g1 is the moment value function of g1 fault mode; I f g1max is the constraint value of the torque current in the g1 fault mode.

[0132] Based on this, the control method of lift and torque in the direct closed-loop control under the g1 fault mode is the same as the control structure under the normal mode, but a fault controller is used, and only the remaining motors that can work normally are used to continue to complete the fault-tolerant operation.

[0133] For a detailed description of the explicit model prediction direct lift and torque controller, please refer to the description of the same or similar parts above, which will not be repeated here.

[0134] In order to verify the effectiveness and superiority of the lift and torque direct closed-loop control and fault-tolerant operation method of a six-rotor aircraft in the present invention, experiments were carried out on a six-rotor aircraft test platform. First, a comparative experiment was conducted between the traditional method and the method proposed in the present invention under the condition of aerodynamic parameter mismatch in the healthy mode; then, the fault-tolerant operation effect of the method proposed in the present invention was tested in the g1 fault mode of motor No. 1 failure, so as to compare and evaluate the control performance more intuitively.

[0135] In a specific embodiment, Figure 3 It can be seen that when the aerodynamic parameter thrust coefficient mismatches K b =0.9K b0 Under the traditional method, the lift, rolling moment and pitching moment all have steady-state deviations. The steady-state deviation of lift is ΔU = UU ref=-0.8N; however, under the method proposed in the present invention, the lift and torque can still be controlled without static error, and the lift steady-state deviation is ΔU = 0. This is because the proposed method adopts a new control structure, which integrates the speed solution process into the controller, making it possible to compensate for the aerodynamic parameter mismatch with the help of the auxiliary disturbance observer, in addition to the steady-state deviation, and enhancing the parameter robustness. In addition, under the traditional method, the lift rise time t r and overshoot σ are 0.14s and 0.35N respectively, while under the proposed method, the rise time t r and overshoot σ are 0.13s and 0.28N respectively, indicating that the proposed method improves the dynamic performance of lift and torque of the hexacopter with faster response speed and smaller overshoot.

[0136] Depend on Figure 4 It can be seen that when motor No. 1 fails, the method proposed in the present invention can achieve excellent fault-tolerant operation of the hexacopter, and the remaining motors No. 2, 3, 5, and 6 can cooperate to generate the desired lift and torque, significantly increasing the safety margin of the hexacopter flight.

[0137] In one embodiment, a lift and torque direct closed-loop control and fault-tolerant operation device for a six-rotor aircraft is proposed, the device comprising:

[0138] A lift and torque direct closed-loop control system for realizing lift and torque direct closed-loop control using the above-mentioned explicit model predictive direct lift and torque controller;

[0139] The fault prediction model, fault controller and fault-tolerant operation control system are used to perform fault prediction model, fault controller and fault-tolerant operation control on the six-rotor aircraft based on the realization of direct closed-loop control of lift and torque and according to different fault modes of the six-rotor aircraft.

[0140] The following is an embodiment of the lift and torque direct closed-loop control and fault-tolerant operation device of the six-rotor aircraft of the present invention, which can be used to execute the lift and torque direct closed-loop control and fault-tolerant operation method embodiment of the six-rotor aircraft of the present invention. For details not disclosed in the lift and torque direct closed-loop control and fault-tolerant operation device embodiment of the six-rotor aircraft of the present invention, please refer to the lift and torque direct closed-loop control and fault-tolerant operation method embodiment of the six-rotor aircraft of the present invention.

[0141] In one embodiment, a hexacopter control system is provided, the system including a lift and torque direct closed-loop control and fault-tolerant operation device for the hexacopter.

[0142] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

Claims

1. An explicit model predictive direct lift and torque controller, characterized in that: The controller is suitable for six-rotor and eight-rotor aircraft, and the controller includes: A definition module is used to split the q-axis current of each motor into four components for independently controlling lift, rolling moment, pitching moment and yaw moment. According to the working principle of multi-rotor aircraft, the current components with the same effect are superimposed according to the action weights and defined as lift current and rolling moment current, pitching moment current and yaw moment current; A prediction model module is used to construct a linear robust prediction model of the lift and torque of the six-rotor aircraft according to the defined lift current and rolling moment current, pitch moment current, and yaw moment current; The value function and linear constraint module of lift and torque is used to obtain the value function and linear constraint of lift and torque by setting the weight coefficient of current increment and the constraint value of current; The execution module is used to construct an explicit model predictive direct lift and torque controller based on a linear robust prediction model of lift and torque of a hexacopter, value functions of lift and torque, and linear constraints.

2. The explicit model predictive direct lift and torque controller according to claim 1, characterized in that: The corresponding relationship between the lift current, rolling moment current, pitch moment current and yaw moment current and the six motor currents is: Among them, i qk (k=1, 2, 3, 4, 5, 6) represents the q-axis current component of the k-th motor; i qU is the lift current defined, is the defined rolling torque current, i qθ is the pitch moment current, i qψ is the defined yaw moment current; i qkf Defined as i qk The components of f are generated in (subscript k = 1, 2, 3, 4, 5, 6 represent the kth motor, subscript f = U, θ, ψ represent lift, rolling moment, pitching moment and yaw moment respectively); The definition expressions of lift current, rolling moment current, pitch moment current and yaw moment current are: Among them, st is the mathematical symbol that satisfies.

3. The explicit model predictive direct lift and torque controller according to claim 1, characterized in that: The method for constructing a linear robust prediction model of lift and torque of a six-rotor aircraft includes: The linear robust prediction model of lift is: Among them, x U is the state variable of the prediction model; Δi qU is the control variable of the prediction model; x U (k) and x U (k+1) are the state variables of the prediction model at the kth discrete moment and the k+1th discrete moment, respectively, k is a natural number; Δi qU (k) is the control variable of the prediction model at the kth discrete moment, U is the lift; U ref is the lift command value; T s is the control period; K U is the lift proportional constant, satisfying K U =2T s K b0 k t0 J r0 -1 Ω, where K b0 is the rotor thrust coefficient K b The nominal value of k t0 is the motor torque constant k t The nominal value, J r0 is the motor rotor inertia J r The nominal value of Ω is the preset speed constant; is the lift disturbance term d in the prediction model U The observed value, d U The specific equations satisfied are: Among them, ω k is the mechanical angular velocity of the kth motor; d ωk The speed disturbance terms of viscous friction and rotor inertia mismatch are considered for the kth motor; B m is the viscous friction coefficient of the motor; T Lk is the windage load torque of the kth motor; ∑ is the summation symbol; The linear robust prediction model of rolling moment, pitching moment and yaw moment is: Where f = U, θ, ψ represent the rolling moment, pitching moment and yaw moment respectively; the proportional constants of rolling, pitching and yaw moments are K θ =2LK b0 k t0 J r0 -1 ΩT s , K ψ =2K d0 k t0 J r0 -1 ΩT s ; The specific equations satisfied by the rolling, pitching, and yaw moment disturbance terms are: in, is the rolling moment disturbance term; d θ is the pitching moment disturbance term; d ψ is the yaw moment disturbance term; L is the distance from the center of the six-rotor aircraft to the motor shaft; K d0 is the rotor anti-twist coefficient K d Nominal value.

4. The explicit model predictive direct lift and torque controller according to claim 1, characterized in that: The lift and torque value functions and linear constraints include: The value function and linear constraints of lift are: Among them, J U is the lift value function; N p is the prediction time domain; q U and q i are the weight coefficients of lift and lift current increment respectively; I Umax is the constraint value of lift current; The value functions and linear constraints of the rolling moment, pitching moment, and yaw moment are: Among them, J f is the moment value function; q f and q if are the weight coefficients of torque and torque current increment respectively; I fmax is the constraint value of torque current.

5. The explicit model predictive direct lift and torque controller according to claim 1, characterized in that: The controller is also provided with an auxiliary disturbance observer for observing lift disturbance term, rolling moment disturbance term, pitch moment disturbance term and yaw moment disturbance term in real time, and feeding them forward to the explicit model prediction direct lift and moment controller.

6. A method for direct closed-loop control and fault-tolerant operation of lift and torque of a six-rotor aircraft, characterized in that: The method comprises the following steps: Using the explicit model prediction direct lift and torque controller as described in any one of claims 1 to 4 to achieve direct closed-loop control of lift and torque; Based on the realization of direct closed-loop control of lift and torque, a fault prediction model, fault controller and fault-tolerant operation control are developed for the hexacopter according to its different failure modes.

7. The method for direct closed-loop control and fault-tolerant operation of lift and torque of a six-rotor aircraft according to claim 6, characterized in that: The explicit model predicts the direct lift and torque controller, which directly obtains the optimal lift current command, rolling moment current command, pitch moment current command and yaw moment current command from the lift command, rolling moment command, pitch moment current command and yaw moment command to uniformly replace the traditional cascade speed solver module and multiple motor speed controllers to achieve direct closed-loop control of lift and torque.

8. The lift and torque direct closed-loop control and fault-tolerant operation method of a six-rotor aircraft according to claim 1, characterized in that: The method of performing a fault prediction model, a fault controller and a fault-tolerant operation control on the six-rotor aircraft according to different fault modes includes: When the No. 1 motor of the hexacopter fails: First, the No. 1 motor and the symmetrical No. 4 motor are stopped at the same time, and the remaining No. 2, No. 3, No. 5 and No. 6 motors continue to work to achieve fault-tolerant operation; This fault mode is recorded as g1. At this time, the corresponding relationship between the g1 lift current, g1 rolling moment current, g1 pitch moment current and g1 yaw moment current and the motor current involved in fault-tolerant operation is: Among them, i qk (k=2, 3, 5, 6) represents the q-axis current component of the k-th motor; i qUg1 is the defined g1 lift current, is defined as the g1 rolling torque current, i qθg1 is defined as the pitch moment current g1, i qψg1 is the defined g1 yaw moment current; i qkf Defined as i qk The components of f are generated in (subscript k = 2, 3, 5, 6 represent the kth motor, subscript f = U, θ, ψ represent lift, rolling moment, pitching moment and yaw moment respectively); The g1 lift current, g1 rolling moment current, g1 pitch moment current, and g1 yaw moment current of the six-rotor aircraft are defined as: In the g1 fault mode, the working mode of the six-rotor aircraft and the collaborative mode of the multi-motor system change accordingly. The g1 fault prediction model of the six-rotor aircraft lift is constructed as follows: Among them, x Ug1 is the state variable of the g1 fault prediction model; x Ug1 (k) and x Ug1 (k+1) are the state variables of the g1 fault prediction model at the kth discrete moment and the k+1th discrete moment respectively; Δi qUg1 is the control variable of the g1 fault prediction model at the kth discrete moment; is the g1 fault lift disturbance term d in the g1 fault prediction model Ug1 The observed value, d Ug1 The specific equations satisfied are: Under the g1 fault mode, the explicit model predicts the direct lift and torque. The cost function and linear constraints used by the g1 fault controller are designed as: Among them, J Ug1 is the lift value function of g1 fault mode; I Ug1max is the constraint value of lift current in g1 fault mode; The value functions and linear constraints of the rolling moment, pitching moment, and yaw moment are: Among them, J fg1 is the moment value function of g1 fault mode; I fg1max is the constraint value of the torque current in the g1 fault mode.

9. A lift and torque direct closed-loop control and fault-tolerant operation device for a six-rotor aircraft, characterized in that: The device comprises: A lift and torque direct closed-loop control system for realizing lift and torque direct closed-loop control using an explicit model predictive direct lift and torque controller as claimed in any one of claims 1 to 4; The fault prediction model, fault controller and fault-tolerant operation control system are used to perform fault prediction model, fault controller and fault-tolerant operation control on the six-rotor aircraft based on the realization of direct closed-loop control of lift and torque, and for different fault modes of the six-rotor aircraft.

10. A six-rotor aircraft control system, characterized in that: The system includes the lift and torque direct closed-loop control and fault-tolerant operation device of the six-rotor aircraft as described in claim 9.

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