A method for controlling the attitude change of a tilt-rotor aircraft while hovering at a fixed point

Abstract

The present invention discloses a method for controlling the fixed-point hovering attitude change of a tiltrotor aircraft. The control technology method can realize the fixed-point hovering function without adjusting the pitch angle, solves the strong constraint of the attitude angle of conventional rotorcraft on the fixed-point hovering flight mode, realizes the complete decoupling of the attitude angle control of four tiltrotors from the fixed-point hovering control, liberates the control of the attitude angle degree of freedom of the four tiltrotor aircraft, and greatly expands the use scenarios of the four tiltrotor aircraft. The present invention has a clear control principle, a novel technical method, and an innovative flight attitude. It is in urgent need in both the civil and military fields and has important engineering practical value.

Description

Technical Field

[0001] The invention relates to a method for controlling a fixed-point hovering attitude change of a tiltrotor aircraft, and belongs to the technical field of aircraft flight control. Background Art

[0002] At present, with the expansion of tilt-rotor application scenarios, the landing of a four-tilt-rotor future dynamic platform is a common usage scenario. In order to ensure the safety of the four-tilt-rotor dynamic platform during landing, the fixed-point hovering attitude control technology will be a key technology that must be broken through. Therefore, in order to improve the safety of the four-tilt-rotor landing dynamic plane, a four-tilt-rotor aircraft fixed-point hovering attitude control method is proposed. The present invention is produced under this background. Summary of the invention

[0003] Purpose of the invention: The purpose of the present invention is to achieve the fixed-point hovering and attitude-changing capability of a four-tilt-rotor aircraft, to enable the four-tilt-rotor aircraft to have the ability to land at an "arbitrary" pitch angle, to expand the use scenarios of the four-tilt-rotor aircraft, to significantly reduce the risk of landing, and to improve the safety of aircraft landing.

[0004] Technical solution:

[0005] The present application discloses a method for controlling a fixed-point hovering attitude change of a tiltrotor aircraft, comprising the following steps:

[0006] Step 1, design the throttle collective pitch channel control law. The four-tilt rotor aircraft maintains the current flight altitude unchanged. In order to take into account the rapidity and anti-interference ability of the throttle channel control, the throttle collective pitch control channel adopts the control strategy of the altitude change rate with the phase leading the altitude by 90° in the inner loop, which increases the anti-interference ability of the system. At the same time, the throttle collective pitch feedforward value is designed to increase the rapidity of the system response and reduce the control pressure of the inner loop integral. The outer loop adopts the control strategy of the altitude error. The design results are as follows:

[0007]

[0008] Among them, δ T is the throttle collective distance control input, It is the altitude change rate signal measured by the GPS onboard the quad-tilt rotor aircraft. Altitude change rate command, H is the altitude signal measured by the airborne GPS, H g is the target hovering height. K H It is the control parameter of the throttle collective distance channel.

[0009] Step 2, design the control law for maintaining the attitude angle of the four-tilt rotor. The pitch angle of the four-tilt rotor body always tracks the pitch angle control command signal to achieve hovering at any pitch attitude within the pitch angle of [-45,45] of the four-tilt rotor. The control strategy is:

[0010]

[0011] θ g =θ cmd

[0012] Among them, U E is the virtual elevator control law solution, Q is the pitch rate measured by the onboard sensor, θ b is the pitch angle measured by the airborne sensor, θ g is the pitch angle control command, is the pitch angular acceleration signal, θ cmd is the pitch angle command signal, is the elevator control parameter.

[0013] Step 3, design the position keeping control law. In order to realize the fixed point keeping function, the forward speed and forward position control are introduced into the tilt channel to realize that the forward position of the four-tilt rotor aircraft remains unchanged. The specific control structure of forward position keeping is as follows:

[0014]

[0015] Among them, τ b is the tilt angle channel control input, u is the forward velocity of the aircraft, u g is the forward speed setting value, x is the forward position measured by GPS, and x g is the target value for the forward position of the aircraft, is the tilt channel control parameter;

[0016] The lateral position holding control structure is as follows:

[0017]

[0018] Among them U A is the virtual aileron rudder control law solution, P is the roll rate measured by the onboard sensor, φ b is the roll angle measured by the onboard sensor, φ g is the roll angle control command, is the roll angular acceleration signal, v is the lateral velocity of the aircraft, v g is the lateral velocity of the aircraft, y is the lateral position measured by GPS, and y g The target value for the lateral position of the aircraft; It is the control parameter of aileron and rudder channel.

[0019] Step 4, design the tilt channel control law. In order to achieve the rapid decoupling control of the pitch angle control and tilt angle of the four-tilt rotor body and improve the rapidity of the system response, the pitch angle command signal in the pitch angle control channel is fed forward to the tilt channel, and its control strategy is:

[0020]

[0021] θ ref =θ cmd

[0022] where θ ref is the feedforward value instruction of the tilt channel, θ cmd It is the body axis pitch control command signal.

[0023] Beneficial effects:

[0024] A method for controlling the fixed-point hovering attitude change of a tiltrotor aircraft of the present invention adopts a closed-loop control method of the tilt angle deflection and the pitch angle, that is, the tilt angle deflection and the elevator pitch control are coordinated to achieve decoupling control of the longitudinal fuselage pitch angle movement and the rotor thrust plane. The method has a clear control principle, a novel solution idea, and excellent results, and has excellent engineering practical value. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the fixed-point hovering and attitude-changing flight process of a tilt-rotor aircraft;

[0026] Figure 2 Schematic diagram of the tilt angle channel control loop;

[0027] Figure 3 Schematic diagram of the throttle collective channel control circuit;

[0028] Figure 4 Schematic diagram of elevator channel control circuit;

[0029] Figure 5 Schematic diagram of the aileron channel control circuit. DETAILED DESCRIPTION

[0030] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be interpreted as limiting the present invention.

[0031] A method for controlling a tilt-rotor aircraft to hover at a fixed point and change its attitude is provided. The specific design steps are as follows:

[0032] Step 1, design the throttle collective pitch channel control law. The four-tilt rotor aircraft maintains the current flight altitude unchanged. In order to take into account the rapidity and anti-interference ability of the throttle channel control, the throttle collective pitch control channel adopts the control strategy of the altitude change rate with the phase leading the altitude by 90° in the inner loop, which increases the anti-interference ability of the system. At the same time, the throttle collective pitch feedforward value is designed to increase the rapidity of the system response and reduce the control pressure of the inner loop integral. The outer loop adopts the control strategy of the altitude error. The design results are as follows:

[0033]

[0034] Among them, δ T is the throttle collective distance control input, It is the altitude change rate signal measured by the GPS onboard the quad-tilt rotor aircraft. Altitude change rate command, H is the altitude signal measured by the airborne GPS, H g is the target hovering height. K H It is the control parameter of the throttle collective distance channel. K H =-0.15.

[0035] Step 2: Design the control law for maintaining the attitude angle of the four-tilt rotor. The pitch angle of the four-tilt rotor body always tracks the pitch angle control command signal to achieve the hovering of the four-tilt rotor at an "arbitrary" pitch angle. The control strategy is:

[0036]

[0037] θ g =θ cmd

[0038] Among them, U E is the virtual elevator control law solution, Q is the pitch rate measured by the onboard sensor, θ b is the pitch angle measured by the airborne sensor, θ g is the pitch angle control command, is the pitch angular acceleration signal, θ cmd is the pitch angle command signal, is the elevator control parameter.

[0039] Step 3, design the position keeping control law. In order to realize the fixed point keeping function, the forward speed and forward position control are introduced into the tilt channel to realize that the forward position of the four-tilt rotor aircraft remains unchanged. The specific control structure of forward position keeping is as follows:

[0040]

[0041] Among them, τ bis the tilt angle channel control input, u is the forward velocity of the aircraft, u g is the forward speed setting value, x is the forward position measured by GPS, and x g is the target value for the forward position of the aircraft, It is the control parameter of the tilt channel.

[0042] The lateral position holding control structure is as follows:

[0043]

[0044] Among them U A is the virtual aileron rudder control law solution, P is the roll rate measured by the onboard sensor, φ b is the roll angle measured by the onboard sensor, φ g is the roll angle control command, is the roll angular acceleration signal, v is the lateral velocity of the aircraft, v g is the lateral velocity of the aircraft, y is the lateral position measured by GPS, and y g The target value for the lateral position of the aircraft; It is the control parameter of aileron and rudder channel.

[0045] Step 4, design the tilt channel control law. In order to achieve the rapid decoupling control of the pitch angle control and tilt angle of the four-tilt rotor body and improve the rapidity of the system response, the pitch angle command signal in the pitch angle control channel is fed forward to the tilt channel, and its control strategy is:

[0046]

[0047] θ ref =θ cmd

[0048] where θ ref is the feedforward value instruction of the tilt channel, θ cmd It is the body axis pitch control command signal.

[0049] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for controlling a fixed-point hovering attitude change of a tilt-rotor aircraft, characterized in that: The control method comprises the following steps: Step 1: In the inertial coordinate system, according to the altitude and altitude change rate signals measured by the GPS sensor, an online feedback strategy is used to design the throttle collective pitch channel control law, and the control input of the collective pitch control channel is obtained to enable the quad-tilt rotor aircraft to hover at any flight altitude during the attitude change process; Step 2, according to the angular rate and attitude angle signals measured by the airborne sensor, an online feedback control strategy is used to design a pitch angle maintenance control law of the four-tilt rotor elevator channel, and a pitch angle control instruction is generated, where the pitch angle control instruction is an expected value of a fixed-point attitude change; Step 3, designing a position keeping control law according to the position coordinate signal measured by the GPS sensor, obtaining the input of the aileron rudder control channel and the input of the tilt angle control channel, respectively realizing that the lateral position and the forward position of the quad-tilt rotor aircraft remain unchanged during the attitude change process, so that the aircraft is always directly above the predetermined position, achieving the purpose of aircraft fixing; Step 4, on the basis of completing the design of the forward position keeping control law of the tilt channel, the pitch angle control command selected in the step 2 is fed forward to the tilt angle control channel, so that the elevator control channel and the tilt angle control channel are coordinated online, eliminating the coupling of the position due to the pitch angle adjustment of the aircraft body, and achieving the purpose of fixed-point hovering attitude change; The online feedback strategy of the throttle collective distance channel includes a combination of inner loop control and outer loop control. The inner loop adopts a control strategy of the altitude change rate with a phase leading altitude of 90°; the outer loop adopts a control strategy of altitude error. The control strategy of the outer loop is as follows: Among them, δ T is the throttle collective distance control input, It is the altitude change rate signal measured by the GPS onboard the quad-tilt rotor aircraft. Altitude change rate command, H is the altitude signal measured by the airborne GPS, H g is the target hovering height, K H is the throttle collective distance channel control parameter, which is less than zero, and the specific value is related to the control object; The pitch angle holding control law is: i g =θ cmd Among them, U E is the virtual elevator control law solution, Q is the pitch rate measured by the onboard sensor, θ b is the pitch angle measured by the airborne sensor, θ g is the pitch angle control command, is the pitch angular acceleration signal, θ cmd is the pitch angle command signal, is the elevator control parameter.

2. A method for controlling a tiltrotor aircraft to hover at a fixed point according to claim 1, characterized in that: The control structure of the control law is as follows: Among them, τ b is the tilt angle channel control input, u is the forward velocity of the aircraft, u g is the forward speed setting value, x is the forward position measured by GPS, and x g is the target value for the forward position of the aircraft, is the tilt channel control parameter; The lateral position holding control structure is as follows: Among them U A is the virtual aileron rudder control law solution, P is the roll rate measured by the onboard sensor, φ b is the roll angle measured by the onboard sensor, φ g is the roll angle control command, is the roll angular acceleration signal, v is the lateral velocity of the aircraft, v g is the lateral velocity of the aircraft, y is the lateral position measured by GPS, and y g The target value for the lateral position of the aircraft; It is the control parameter of aileron and rudder channel.

3. The method for controlling the fixed-point hovering and attitude change of a tilt-rotor aircraft according to claim 1, characterized in that: The pitch angle control command signal in the pitch angle control channel is fed forward to the tilt channel, and its control strategy is: i ref =θ g where θ ref is the feedforward value instruction of the tilt channel, θ g Select the control command signal for the body axis pitch.

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