Direct closed-loop control of lift and moment and fault-tolerant operation method and device for a six-rotor aircraft

Abstract

The present invention discloses a method and device for direct closed-loop control of lift and moment and fault-tolerant operation of a six-rotor aircraft. The controller obtained by using the present invention can directly obtain the optimal current command from the lift command and the moment command, and uniformly replace the traditional cascaded speed calculation module and multiple speed controllers; the obtained control system can realize the direct closed-loop control of lift and moment, not only significantly improving the dynamic performance of lift and moment, but also integrating the speed calculation process using aerodynamic parameters into the controller, and can eliminate the steady-state static error caused by aerodynamic parameter mismatch with the help of an auxiliary disturbance observer, enhancing the steady-state control accuracy of lift and moment and the system robustness; finally, for different fault modes, fault prediction models, fault controllers and fault-tolerant operation control systems suitable for different faults are reconstructed to ensure the excellent fault-tolerant operation of the multi-rotor aircraft in some fault modes and improve the safety and reliability of the operation of the multi-rotor aircraft.

Description

Technical Field

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

[0002] Multi-rotor aircraft, with advantages such as small volume, low cost, flexible operation, and vertical takeoff and landing, are widely used in many fields such as agriculture, military, industry, and commerce to perform tasks such as plant protection, irrigation, reconnaissance, rescue, mapping, and logistics, and have broad application prospects. Among them, six-rotor and eight-rotor aircraft can utilize the redundancy of actuators for fault-tolerant control and have stronger load-bearing capabilities, which have received extensive attention, and the research on their high dynamics and safe and reliable flight has high value.

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

[0004] The flight control and motor control are connected through a speed calculation module. The speed calculation module calculates the lift command, roll moment command, pitch moment command, and yaw moment command into speed commands for four motors according to aerodynamics and the dynamics of a quad-rotor aircraft.

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

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

[0007] The technical solutions provided by the present invention are as follows:

[0008] In a first aspect, the present invention provides an explicit model predictive direct lift and moment controller, which is applicable to six-rotor and eight-rotor aircraft. The controller includes:

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

[0010] A prediction model module for constructing a linear robust prediction model of the lift and moment of the six-rotor aircraft based on the defined lift current, roll moment current, pitch moment current, and yaw moment current;

[0011] A value function and linear constraint module for lift and moment, which is used to obtain the value function and linear constraints of lift and moment by setting the weight coefficients of the current increment and the constraint values of the current;

[0012] An execution module for constructing an explicit model predictive direct lift and moment controller according to the linear robust prediction model of the lift and moment of the six-rotor aircraft and the value function and linear constraints of the lift and moment.

[0013] In an embodiment, the correspondence between the lift current, roll moment current, pitch moment current, and yaw moment current and the six-motor current is as follows:

[0014]

[0015] where, i qk (k = 1, 2, 3, 4, 5, 6) represents the q-axis current component of the k-th motor; i qU is the defined lift current, is the defined roll moment current, i qθ is the defined pitch moment current, i qψ is the defined yaw moment current; i qkf is defined as the component generating f in i qk (the subscripts k = 1, 2, 3, 4, 5, 6 respectively represent the k-th motor, and the subscripts f = U, θ, ψ respectively represent lift, roll moment, pitch moment, and yaw moment);

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

[0017]

[0018] where, s.t. is the mathematical symbol for satisfaction.

[0019] In one embodiment, the linear robust prediction model for constructing the lift and moment of the hexacopter includes:

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

[0021]

[0022] where 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 k-th discrete time and the (k + 1)-th discrete time respectively, and k is a natural number; Δi qU (k) is the control variable of the prediction model at the k-th discrete time. 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 nominal value of the rotor thrust coefficient K b ; k t0 is the nominal value of the motor torque constant k t ; J r0 is the nominal value of the motor rotor inertia J r ; Ω is the preset speed constant; is the observed value of the lift disturbance term d U in the prediction model, and the specific equation satisfied by d U is:

[0023]

[0024] where ω k is the mechanical angular velocity of the k-th motor; d ωk is the speed disturbance term of the k-th motor considering viscous friction and rotor inertia mismatch, etc.; B m is the viscous friction coefficient of the motor; T Lk is the load torque such as wind resistance of the k-th motor; ∑ is the summation symbol;

[0025] The linear robust prediction models for roll moment, pitch moment and yaw moment are:

[0026]

[0027] where f = U, θ, ψ represent the roll moment, pitch moment, and yaw moment respectively; the roll, pitch, and yaw moment proportionality constants 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 roll, pitch, and yaw moment disturbance terms are:

[0028]

[0029] where, is the roll moment disturbance term; d θ is the pitch 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 nominal value of the rotor anti-twist coefficient K d .

[0030] In one embodiment, the value functions and linear constraints of the lift and moments include:

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

[0032]

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

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

[0035]

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

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

[0038] Second, the present invention provides a method for direct closed-loop control of lift and moment and fault-tolerant operation of a six-rotor aircraft, and the method includes the following steps:

[0039] Using the above-mentioned explicit model predictive direct lift and moment controller to achieve direct closed-loop control of lift and moment;

[0040] Based on the realization of direct closed-loop control of lift and moment, for different fault modes of the six-rotor aircraft, a fault prediction model, a fault controller and a fault-tolerant operation control are carried out on the six-rotor aircraft.

[0041] In one embodiment, the explicit model predictive direct lift and moment controller directly obtains the optimal lift current command, roll moment current command, pitch moment current command and yaw moment current command from the lift command, roll moment command, pitch moment command and yaw moment command, so as to uniformly replace the traditional cascaded speed calculation module and multiple motor speed controllers to achieve direct closed-loop control of lift and moment.

[0042] In one embodiment, the carrying out of the fault prediction model, the fault controller and the fault-tolerant operation control on the six-rotor aircraft for different fault modes includes:

[0043] When the No. 1 motor of the six-rotor aircraft fails:

[0044] First, the No. 1 motor and the symmetrical No. 4 motor are stopped from working 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 denoted as g1. At this time, the corresponding relationships between the g1 lift current, g1 roll moment current, g1 pitch moment current, g1 yaw moment current and the motor currents participating in the fault-tolerant operation are:

[0046]

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

[0048] The lift current, roll moment current, pitch moment current and yaw moment current of the g1 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 cooperative mode of the multi-motor system change accordingly. The g1 fault prediction model of the lift of the six-rotor aircraft is constructed as:

[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 k-th discrete time and the (k + 1)-th discrete time respectively; Δi qUg1 is the control variable of the g1 fault prediction model at the k-th discrete time; is the observed value of the g1 fault lift disturbance term d Ug1 in the g1 fault prediction model. The specific equation satisfied by d Ug1 is:

[0053]

[0054] In the g1 fault mode, the value function and linear constraints used by the explicit model predictive direct lift and moment g1 fault controller are designed as:

[0055]

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

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

[0058]

[0059] Among them, J f g1 is the moment value function in the g1 fault mode; I f g1maxThe constraint value of the torque current for the g1 fault mode.

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

[0061] A lift and torque direct closed-loop control system, configured to use the explicit model predictive direct lift and torque controller as described above to implement lift and torque direct closed-loop control;

[0062] A fault prediction model, a fault controller and a fault-tolerant operation control system, configured to perform fault prediction model, fault controller and fault-tolerant operation control on the six-rotor aircraft for different fault modes of the six-rotor aircraft based on the implementation of lift and torque direct closed-loop control.

[0063] Fourthly, the present invention provides a six-rotor aircraft control system, and the system includes the lift and torque direct closed-loop control and fault-tolerant operation device of the six-rotor aircraft as described above.

[0064] Advantages 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 controllers is proposed: under the new control structure, the multi-motor system is regarded as a whole, with the lift and torque current tracking as the new control objective, to implement the direct closed-loop control of lift and torque, and improve the dynamic response speed of lift and torque.

[0066] (2) A linear robust prediction model of lift and torque is constructed, and based on this, an explicit model predictive direct lift and torque controller is designed. This controller can directly obtain the optimal lift current and torque current commands from the lift and torque commands, and uniformly replaces the traditional cascaded speed calculation module and multiple speed controllers. Since the speed calculation process using aerodynamic parameters is integrated into the controller, it becomes possible to compensate for the mismatch of aerodynamic parameters with the help of an auxiliary disturbance observer, eliminate the steady-state deviation of lift and torque, and improve 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, significantly enhancing the safety and reliability of the multi-rotor aircraft. Description of the Drawings

[0068] The accompanying drawings, as part of the present invention, are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention, but do not unduly limit the present invention. Obviously, the accompanying drawings in the following description are only some embodiments, and those of ordinary skill in the art can obtain other drawings based on these drawings without creative efforts.

[0069] Figure 1 It is a schematic structural diagram of an explicit model predictive direct lift and moment controller provided in an embodiment of the present invention;

[0070] Figure 2 It is a flowchart of a direct closed-loop control and fault-tolerant operation method for the lift and moment of a six-rotor aircraft provided in an embodiment of the present invention;

[0071] Figure 3 It is a comparative effect diagram of the lift and moment control of a six-rotor aircraft when there is an aerodynamic parameter mismatch in the healthy mode provided in an embodiment;

[0072] Figure 4 It is an effect diagram of the lift, moment, and rotational speed control of a six-rotor aircraft in fault-tolerant operation in the fault mode of No. 1 motor provided in an embodiment.

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

[0074] To deepen the understanding of the present invention, the technical solutions of the present invention will be further introduced below in conjunction with the accompanying drawings and specific embodiments. The following embodiments are explanations of the present invention, and the present invention is not limited to the following embodiments.

[0075] An embodiment of the present invention provides an explicit model predictive direct lift and moment controller, which is applicable to six-rotor and eight-rotor aircraft. Referring to Figure 1 as shown, the controller includes:

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

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

[0078] A value function and linear constraint module for lift and moment, which is used to obtain the value function and linear constraints of lift and moment by setting the weight coefficient of current increment and the constraint value of current;

[0079] An execution module, which is used to construct an explicit model predictive direct lift and moment controller according to the linear robust prediction model of the lift and moment of a six-rotor aircraft, the value function of the lift and moment, and the linear constraints.

[0080] In the embodiment of the present application, the corresponding relationships between the lift current, the roll moment current, the pitch moment current, and the yaw moment current and the six-motor current are as follows:

[0081]

[0082] where, i qk (k = 1, 2, 3, 4, 5, 6) represents the q-axis current component of the k-th motor, and i qU is the defined lift current, is the defined roll moment current, i qθ is the defined pitch moment current, i qψ is the defined yaw moment current; i qkf is defined as the component generating f in i qk (the subscripts k = 1, 2, 3, 4, 5, 6 respectively represent the k-th motor, and the subscripts f = U, θ, ψ respectively represent lift, roll moment, pitch moment, and yaw moment).

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

[0084] Taking a six-rotor aircraft as an example, the defined expression formulas of its lift current, roll moment current, pitch moment current, and yaw moment current are:

[0085]

[0086]

[0087] where, s.t. is the mathematical symbol for satisfaction.

[0088] Furthermore, based on the defined new variables, a linear robust prediction model of the lift and moment of a multi-rotor 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] where 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 k-th discrete time and the (k + 1)-th discrete time respectively, and k is a natural number; Δi qU (k) is the control variable of the prediction model at the k-th discrete time. 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 nominal value of the rotor thrust coefficient K b ; k t0 is the nominal value of the motor torque constant k t ; J r0 is the nominal value of the motor rotor inertia J r ; Ω is the pre-set rotational speed constant; is the observed value of the lift disturbance term d U in the prediction model, and the specific equation satisfied by d U is:

[0092]

[0093] where ω k is the mechanical angular velocity of the k-th motor; d ωk is the rotational speed disturbance term of the k-th motor considering viscous friction and rotor inertia mismatch, etc.; B m is the viscous friction coefficient of the motor; T Lk is the load torque such as wind resistance of the k-th motor; ∑ is the summation symbol.

[0094] The linear robust prediction models of the roll moment, pitch moment, and yaw moment have the same structure:

[0095]

[0096] where f = U, θ and ψ represent the roll moment, pitch moment, and yaw moment respectively; the proportionality constants for the roll, pitch, 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 disturbance terms of the roll, pitch, and yaw moments are:

[0097]

[0098] where is the disturbance term of the roll moment; d θ is the disturbance term of the pitch moment; d ψ is the disturbance term of the yaw moment; L is the distance from the center of the hexacopter to the motor shaft; K d0 is the nominal value of the rotor anti-twist coefficient K d .

[0099] Furthermore, the value functions and linear constraints of the lift and moments include:

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

[0101]

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

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

[0104]

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

[0106] In an optional embodiment, the controller is further provided with an auxiliary disturbance observer for real-time observation of the lift disturbance term, roll moment disturbance term, pitch moment disturbance term, and yaw moment disturbance term, and feeding them forward to the explicit model predictive direct lift and moment controller.

[0107] Similarly, referring to the six-rotor aircraft, an octocopter constructs a linear robust prediction model for lift and moment applicable to the octocopter based on the defined new variables.

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

[0109] Step S100: Use the above-mentioned explicit model predictive direct lift and moment controller to achieve direct closed-loop control of lift and moment.

[0110] Specifically, in this control method, the explicit model predictive direct lift and moment controller directly obtains the optimal

[0111] lift current command, roll moment current command, pitch moment current command, and yaw moment current command to uniformly replace the traditional cascaded speed calculation module and multiple motor speed controllers, and achieve direct closed-loop control of lift and moment.

[0112] It should be noted that since the control algorithm of the explicit model predictive direct lift and moment controller is an optimal control algorithm, the control law obtained through the explicit model predictive direct lift and moment controller is the optimal control law.

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

[0114] Step S200: Based on achieving direct closed-loop control of lift and moment, for different fault modes of the six-rotor aircraft, conduct fault prediction models, fault controllers, and fault-tolerant operation control for the six-rotor aircraft.

[0115] For different fault modes, conduct fault prediction models, fault controllers, and fault-tolerant operation control for the six-rotor aircraft, specifically including:

[0116] Taking the failure of the No. 1 motor of the six-rotor aircraft as an example, first, simultaneously stop the operation of the No. 1 motor and the symmetric No. 4 motor, and let the remaining No. 2, No. 3, No. 5, and No. 6 motors continue to operate to achieve fault-tolerant operation. Denote this fault mode as g1. At this time, the g1 lift current, g1 roll 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 the defined g1 roll moment current, i qθg1 is the defined g1 pitch moment current, i qψg1 is the defined g1 yaw moment current; i qkf is defined as the component generating f in i qk (the subscripts k = 2, 3, 5, 6 represent the kth motor respectively, and the subscripts f = U, θ, ψ represent lift, roll moment, pitch moment, and yaw moment respectively).

[0119] The corresponding relationships between the g1 lift current, g1 roll moment current, g1 pitch moment current, and g1 yaw moment current and the motor currents participating in fault-tolerant operation are:

[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 cooperative mode of the multi-motor system change accordingly. Based on this, construct the g1 fault prediction model of the lift of the six-rotor aircraft as:

[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 time and the (k + 1)th discrete time respectively; Δi qUg1 is the control variable of the g1 fault prediction model at the kth discrete time. is the observed value of the g1 fault lift disturbance term d Ug1 in the g1 fault prediction model, and the specific equation satisfied by d Ug1 is:

[0125]

[0126] In the g1 failure mode, the value function and linear constraints used by the explicit model predictive direct lift and moment g1 failure controller are designed as follows:

[0127]

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

[0129] The value functions and linear constraints for the roll moment, pitch moment, and yaw moment are as follows:

[0130]

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

[0132] Accordingly, in the direct closed-loop control of lift and moment in the g1 failure mode, its control method has the same control structure as in the normal mode, but a failure controller is used, and only the remaining motors that can still work normally are used to continue the fault-tolerant operation.

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

[0134] To verify the effectiveness and superiority of the direct closed-loop control and fault-tolerant operation method of lift and moment for a six-rotor aircraft of the present invention, experiments are carried out on a six-rotor aircraft test platform. First, a comparative experiment is carried out on the traditional method and the method proposed by the present invention under the condition of aerodynamic parameter mismatch in the healthy mode; then, the fault-tolerant operation effect of the method proposed by the present invention is tested in the g1 failure mode with the No. 1 motor failure to more intuitively compare and evaluate the control performance.

[0135] In a specific embodiment, from Figure 3 it can be seen that when the thrust coefficient of the aerodynamic parameter is mismatched, K b = 0.9K b0 , in the traditional method, steady-state deviations occur in the lift, roll moment, and pitch moment. The steady-state deviation of the lift is ΔU = U - U ref= -0.8 N; while under the method proposed in the present invention, static error-free following control of lift and moment can still be achieved, and the steady-state deviation of lift is ΔU = 0. This is because the proposed method adopts a new control structure, integrating the rotational speed calculation process into the controller, making it possible to compensate for the mismatch of aerodynamic parameters with the aid of an auxiliary disturbance observer. In addition to the steady-state deviation, the parameter robustness is enhanced. Furthermore, under the traditional method, the rise time t r and overshoot σ of lift are 0.14 s and 0.35 N respectively, while under the proposed method, the rise time t r and overshoot σ of lift are 0.13 s and 0.28 N respectively, indicating that the proposed method improves the dynamic performance of lift and moment of the hexacopter, with a faster response speed and a smaller overshoot.

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

[0137] In one embodiment, a device for direct closed-loop control of lift and moment and fault-tolerant operation of a hexacopter is proposed. The device includes:

[0138] A direct closed-loop control system for lift and moment, which is used to achieve direct closed-loop control of lift and moment by using the explicit model predictive direct lift and moment controller described above;

[0139] A fault prediction model, a fault controller, and a fault-tolerant operation control system, which are used to perform fault prediction model, fault controller, and fault-tolerant operation control on the hexacopter for different fault modes of the hexacopter based on achieving direct closed-loop control of lift and moment.

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

[0141] In one embodiment, a control system for a hexacopter is proposed, and the system includes the device for direct closed-loop control of lift and moment and fault-tolerant operation of the hexacopter.

[0142] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, 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, it should be considered as the scope recorded in this specification.

Claims

1. An explicit model predictive direct lift and moment controller, characterized in that, The controller is applicable to a six-rotor aircraft, and the controller includes: A definition module for splitting the q-axis current of each motor into four components that separately control lift, roll moment, pitch moment, and yaw moment. According to the working principle of a multi-rotor aircraft, the current components with the same effect are superimposed according to the action weights and defined as lift current, roll moment current, pitch moment current, and yaw moment current; A prediction model module for constructing a linear robust prediction model of the lift and moments of the six-rotor aircraft based on the defined lift current, roll moment current, pitch moment current, and yaw moment current; A value function and linear constraint module for lift and moments for obtaining the value function and linear constraints of lift and moments by setting the weight coefficient of the current increment and the constraint value of the current; An execution module for constructing an explicit model predictive direct lift and moment controller according to the linear robust prediction model of the lift and moments of the six-rotor aircraft and the value function and linear constraints of lift and moments.

2. The explicit model predictive direct lift and moment controller according to claim 1, wherein: The correspondence between the lift current, roll moment current, pitch moment current, and yaw moment current and the six-motor current is: Among them, i qk represents the q-axis current component of the kth motor, where k takes values 1, 2, 3, 4, 5, 6; i qU is the defined lift current, is the defined roll moment current, i qθ is the defined pitch moment current, i qψ is the defined yaw moment current; i qkf is defined as the component that generates f in i qk The subscript k = 1, 2, 3, 4, 5, 6 represents the kth motor respectively, and the subscripts f = U, θ, ψ represent lift, roll moment, pitch moment, and yaw moment respectively; The definition expressions of the lift current, roll moment current, pitch moment current, and yaw moment current are: Wherein, s.t. is the mathematical symbol for satisfaction.

3. The explicit model predictive direct lift and moment controller according to claim 1, characterized in that: The constructing of the linear robust prediction model of the lift and moments of the 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 k-th discrete time and the (k + 1)-th discrete time respectively, where k is a natural number; Δi qU (k) is the control variable of the prediction model at the k-th discrete time, i qU is the defined lift current, U is the lift; U ref is the lift command value; T s is the control period; K U is the lift proportionality constant, satisfying K U = 2T s K b0 k t0 J r0 -1 Ω, where K b0 is the nominal value of the rotor thrust coefficient K b of the rotor, k t0 is the nominal value of the motor torque constant k t of the motor, J r0 is the nominal value of the motor rotor inertia J r of the motor, and Ω is the pre-set speed constant; is the observed value of the lift disturbance term d U in the prediction model, and the specific equation that d U satisfies is: where, i qk represents the q-axis current component of the k-th motor, k = 1, 2, 3, 4, 5, 6; ω k is the mechanical angular velocity of the k-th motor; d ωk is the rotational speed disturbance term of the k-th motor considering viscous friction and rotor inertia mismatch; B m is the viscous friction coefficient of the motor; T Lk is the wind resistance load torque of the k-th motor; ∑ is the summation symbol; The linear robust prediction models of roll moment, pitch moment, and yaw moment have the same form: where f takes θ, ψ represent the roll moment, pitch moment, and yaw moment respectively, and the roll, pitch, and yaw moment proportionality constants 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 roll, pitch, and yaw moment disturbance terms are: Among them, is the rolling moment disturbance term; d θ is the pitch 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 nominal value of the rotor anti-twist coefficient K d ; is the defined rolling moment current, i qθ is the defined pitch moment current, i qψ is the defined yaw moment current.

4. The explicit model predictive direct lift and moment controller according to claim 3, characterized in that: The value function and linear constraints of the lift and moments include: The value function and linear constraints of lift are: Among them, J U is the lift value function; N p is the prediction horizon; 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, U ref is the lift command value, and U is the lift; The value function and linear constraints of roll moment, pitch moment, and yaw moment are: Among them, J f is the torque 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 moment controller according to claim 1, wherein: The controller is further provided with an auxiliary disturbance observer for observing in real time the lift disturbance term, roll moment disturbance term, pitch moment disturbance term, and yaw moment disturbance term and feeding them forward into the explicit model predictive direct lift and moment controller.

6. A direct closed-loop control and fault-tolerant operation method for the lift and moment of a six-rotor aircraft, characterized in that: The method includes the following steps: Using the explicit model predictive direct lift and moment controller according to any one of claims 1-4 to achieve direct closed-loop control of lift and moments; On the basis of achieving direct closed-loop control of lift and moments, for different fault modes of the six-rotor aircraft, performing a fault prediction model, a fault controller, and fault-tolerant operation control on the six-rotor aircraft.

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

8. The direct closed-loop control and fault-tolerant operation method for the lift and moment of a six-rotor aircraft according to claim 7, characterized in that: Performing a fault prediction model, a fault controller, and fault-tolerant operation control on the six-rotor aircraft for different fault modes, including: When the No. 1 motor of the six-rotor aircraft fails: First, stop the No. 1 motor and the symmetric No. 4 motor from working simultaneously, and let the remaining No. 2, No. 3, No. 5, and No. 6 motors continue to work to achieve fault-tolerant operation; Record this fault mode as g1. At this time, the corresponding relationships between the g1 lift current, g1 roll moment current, g1 pitch moment current, and g1 yaw moment current and the motor currents participating in fault-tolerant operation are as follows: where, i q2 represents the q-axis current component of the second motor, i q3 represents the q-axis current component of the third motor, i q5 represents the q-axis current component of the fifth motor, i q6 represents the q-axis current component of the sixth motor; i qkf is defined as the component that generates f in i qk The subscript k = 2, 3, 5, 6 respectively represents the k-th motor, and the subscripts f = U, θ, ψ respectively represent lift, rolling moment, pitching moment, and yaw moment; The g1 lift current, g1 roll moment current, g1 pitch moment current, and g1 yaw moment current of the six-rotor aircraft are defined as: where i qUg1 is the defined g1 lift current, is the defined g1 roll moment current, i qθg1 is the defined g1 pitch moment current, i qψg1 is the defined g1 yaw moment current; In the g1 fault mode, the working mode of the six-rotor aircraft and the cooperative mode of the multi-motor system change correspondingly. Construct the g1 fault prediction model of the lift of the six-rotor aircraft as: Among them, U is the lift force; 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 k-th discrete time and the (k + 1)-th discrete time respectively; U ref is the lift command value; T s is the control period; K U is the lift proportional constant, Δi qUg1 is the control variable of the g1 fault prediction model; is the observed value of the g1 fault lift disturbance term d Ug1 in the g1 fault prediction model, and the specific equation satisfied by d Ug1 is: where k t0 is the nominal value of the motor torque constant k t , ω k is the mechanical angular velocity of the k-th motor, d ωk is the rotational speed disturbance term of the k-th motor considering viscous friction and rotor inertia mismatch, J r0 is the nominal value of the motor rotor inertia J r , K b0 is the nominal value of the rotor thrust coefficient K b , i qk represents the q-axis current component of the k-th motor, k = 2, 3, 5, 6; i qU is the defined lift current; In the g1 fault mode, the cost function and linear constraints used by the explicit model predictive direct lift and moment g1 fault controller are designed as: Among them, J Ug1 is the lift value function of the g1 fault mode; I Ug1max is the constraint value of the lift current of the g1 fault mode; N p is the prediction time domain, q U and q i are the weight coefficients of the lift and the lift current increment respectively; The cost function and linear constraints of the roll moment, pitch moment, and yaw moment are: Among them, q f and q if are the weight coefficients of the torque and the increment of torque current respectively; J fg1 is the torque value function of the g1 fault mode; I fg1max is the constraint value of the torque current of the g1 fault mode.

9. A lift and moment direct closed-loop control and fault-tolerant operation device for a six-rotor aircraft, characterized in that, The device includes: A lift and moment direct closed-loop control system for realizing direct closed-loop control of lift and moment by using the explicit model predictive direct lift and moment controller according to any one of claims 1-4; A fault prediction model, a fault controller, and a fault-tolerant operation control system for performing fault prediction model, fault controller, and fault-tolerant operation control on the six-rotor aircraft for different fault modes of the six-rotor aircraft on the basis of realizing direct closed-loop control of lift and moment.

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

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