Three-rotor type air-ground amphibious robot and control method thereof

Abstract

The invention discloses a three-rotor type land-air amphibious robot and a control method thereof.The three-rotor type land-air amphibious robot comprises a robot body shell and a robot body, and the robot body shell and the robot body are connected through a fixing piece; the fuselage body comprises a bottom mounting plate, a three-axis rotor wing and a driven roller; the three-axis rotors are uniformly distributed on the bottom mounting plate in a Y shape; the three-axis rotor wing comprises a top rotor wing and left and right side rotor wings at the tail part; the top rotor wing is connected with a rotor wing rotating steering engine on the bottom mounting plate through a rotating rod; the rotors on the left side and the right side of the tail part are mounted on the bottom mounting plate through corresponding rotor motors; and the driven roller is mounted in the center of the bottom mounting plate and is fixed on a wheel shaft of the bottom mounting plate through a clamp spring. The lift force and the torque are changed by adjusting the rotating speed of each rotor motor, and the amphibious motion mode with the flight capacity and the ground motion capacity at the same time is achieved; a photoelectric encoder is installed on a driven roller to measure the rotation angle of the roller, and speed control in a ground movement mode is achieved.

Description

Technical Field

[0001] The present invention relates to an amphibious aircraft and its control method, and particularly to a three-rotor land-air amphibious robot and its control method. Background Art

[0002] With the rapid development of aircraft technology, aircraft are widely used in many fields such as logistics, agriculture, and exploration. However, there are still many technical problems in the application of existing multi-rotor aircraft in actual operation, especially in terms of stability, energy efficiency, and complex environment adaptability during ground movement and transition flight phases. The existing aircraft generally have the following technical problems:

[0003] 1) Insufficient stability of the aircraft in complex terrains: Existing multi-rotor aircraft often encounter problems such as stall and drift when flying in complex terrains (such as densely built urban areas, mountainous areas, forests, etc.), resulting in unstable flight trajectories and even difficult control. 2) Insufficient environmental adaptability of the aircraft: Existing multi-rotor aircraft perform poorly in different environments, especially under extreme weather conditions (such as strong winds, heavy rains, etc.), with poor flight stability and being easily affected by the external environment. 3) Low energy utilization efficiency of the aircraft: The flight mode of multi-rotor drones requires the rotors to work continuously to maintain stability and control direction, which makes its energy utilization efficiency lower than that of fixed-wing aircraft. When performing low-altitude hovering, slow movement, or precise positioning tasks, the energy consumption is even greater. Relying on powerful motors for flight leads to rapid battery consumption, affecting the feasibility of actual application scenarios. 4) Poor flexibility of the aircraft after landing: Existing multi-rotor amphibious aircraft usually cannot effectively adjust their postures after landing, especially in the case of no flat landing points. Without a flat ground, the aircraft may need to rely on parachutes, deceleration devices, or passive landing methods, often wasting time and reducing the overall efficiency of the aircraft. 5) Complexity of the aircraft control system: Existing multi-rotor amphibious aircraft usually require complex control systems to adjust the aircraft's posture, speed, and stability in real time. Especially in a multi-task environment where the aircraft needs to frequently switch between high-altitude flight and low-altitude taxiing, the existing control systems often cannot achieve smooth transitions, resulting in increased control difficulty of the aircraft. 6) Limitations of the aircraft structure: Currently, most of the aircraft on the market are of the four-rotor configuration, with low space utilization rate and large sizes; four-rotor aircraft usually require a large diagonal size to ensure the stable operation of the rotors, affecting their operation ability in narrow spaces; the structure is relatively symmetrical and difficult to be optimized into a more compact form, limiting its application in indoor, narrow spaces, or pipelines.

[0004] To solve the problems that occur in the above multi-rotor aircraft, many different types of amphibious robots have been designed in the market. Traditional amphibious robots often face problems such as low energy efficiency and slow response when switching from flight mode to ground mode. However, they can use less energy to glide on the ground, which can offset the energy consumption during the transition flight and improve the endurance of the aircraft. In low-altitude flight or ground tasks, amphibious robots can choose an appropriate mode to glide, cross complex obstacles, save energy and reduce energy efficiency losses.

[0005] Existing technical solutions mainly focus on the combination of amphibious aircraft or wheeled drive systems and flight technology, specifically including: 1) Amphibious robots with four-wheel chassis. Among existing amphibious robots, the design of using a four-wheel chassis is relatively common. These amphibious robots move on the ground through four wheels and use rotors for flight. The four-wheel chassis plays a role in supporting and stabilizing the aircraft, but its limitations are also very obvious. First, the turning radius of the four-wheel design is large, resulting in poor flexibility. Second, the four-wheel design requires a large floor area and structural complexity, increasing the weight and volume of the robot. The control system of such robots is relatively complex, and it is not as maneuverable as single-wheel or other ground gliding methods in narrow environments.

[0006] The hybrid air-ground dual-use concept aircraft Drivocopter adopts a design that combines multi-rotors and a wheeled chassis. However, their wheels are more used to stabilize the aircraft rather than assist in gliding and landing. Although this design improves the ground mobility of the robot, it still cannot achieve a smooth transition between the air flight mode, requiring suitable ground or air takeoff and landing conditions, which limits its use in complex situations.

[0007] 2) The combination of rotors and ground wheels. Another existing technical solution is the design that combines rotors and ground wheels. Such amphibious robots generate lift through rotors in flight mode and use wheels for gliding in ground mode. A new type of hybrid air-ground quadrotor robot (Roller-Quadroto) combines the mobility of an aerial vehicle and the endurance of a ground vehicle, and realizes the switch between the ground and the air by adopting a unicycle drive system and rotor-assisted steering. However, the switching process between the ground and air modes of this design is relatively complex, and it has a large volume and poor stability.

[0008] Existing amphibious robots have the following disadvantages: 1) Poor endurance of amphibious robots: Existing amphibious robots show high mobility and flexibility in flight, but the flight mode of existing amphibious robots requires multiple rotors to work continuously to maintain stability and control direction, which makes its energy utilization rate lower than that of fixed-wing aircraft. When performing low-altitude hovering, slow movement or precise positioning tasks, the robot consumes more energy.

[0009] 2) The stability of the land-air amphibious robot is poor in complex terrains: In complex terrains, the stability and control difficulty of the land-air amphibious robot will increase significantly. Especially when the robot is in the low-altitude flight state and encounters wind speed changes or ground undulations, the existing robots are prone to unstable phenomena such as stall and drift, resulting in difficult control. The urban environment with dense high-rise buildings, complex mountainous areas, and open areas with strong winds are all complex terrains that are difficult for the robot to adapt to. In these environments, the robot not only needs to rely on an efficient control system but also needs to have a certain ground adaptation ability to ensure the smooth completion of the task.

[0010] 3) The efficiency of the land-air amphibious robot is low during the flight and ground mode switching: Currently, the land-air amphibious robots usually rely on the switching between the flight mode and the ground mode to adapt to different task requirements. In traditional land-air amphibious robots, the transition between the flight mode and the ground mode often requires a complex process, resulting in low energy efficiency and poor efficiency. For example, when switching from the flight mode to the ground gliding mode, the robot needs to first reduce the flight altitude, decelerate, and perform a series of adjustment operations. This process not only consumes a large amount of electric energy but also often causes task delays and increases the task execution time. In some cases, the robot may not be able to efficiently complete the conversion from flight to ground gliding, affecting the overall operation efficiency.

[0011] 4) High cost and complex structure: Most of the existing land-air amphibious robots adopt a four-wheel chassis or other complex structures, and the complexity of their structures and control systems is relatively high, resulting in high manufacturing and maintenance costs. Especially in the design that requires multiple-wheel support, the power coupling between the wheels and the rotors needs to be coordinated by a complex control system. This not only increases the hardware cost of the robot but also increases the difficulty of operation and maintenance. In addition, the existing designs often require the combination of multiple components, increasing the weight and volume of the overall structure and affecting the performance and stability of the robot.

[0012] 5) Unable to adapt to narrow spaces or extreme environments: Robots with a four-wheel or multi-wheel design have a large volume and turning radius, making them unable to adapt to narrow spaces, especially when performing tasks indoors or in crowded environments. Due to their bulky structures, such robots are often unable to move flexibly through urban streets, between buildings, or other dense spaces. This makes the robots of the existing technologies unable to effectively complete tasks in some specific tasks, such as building interior inspections and disaster area search and rescue. Summary of the Invention

[0013] The object of the present invention is to overcome the defects of the prior art and provide a three-rotor land-air amphibious robot and its control method, which is composed of a Y-shaped three-axis rotorcraft equipped with passive rollers. The Y-shaped layout of the three-axis rotorcraft is relatively compact, which can reduce the degree of mutual interference of the airflow between the rotors, improve the stability and flight performance of the aircraft, and realize the amphibious movement mode with both flight ability and ground movement ability by adjusting the rotation speed of each rotor motor to change the lift and torque.

[0014] On the one hand, the object of the present invention is achieved as follows: A three-rotor land-air amphibious robot, characterized in that it includes a fuselage shell and a fuselage body, and the fuselage shell is connected to the fuselage body through fixing parts; the fuselage body includes a bottom mounting plate, a three-axis rotor and passive rollers; the three-axis rotor is evenly distributed in a Y shape on the bottom mounting plate; the three-axis rotor includes a top rotor and left and right tail rotors, and the top rotor is connected to a rotor rotary servo on the bottom mounting plate through a rotating rod; the left and right tail rotors are installed on the bottom mounting plate through corresponding rotor motors; the passive rollers are installed at the center position of the bottom mounting plate, and the passive rollers are fixed on the axle of the bottom mounting plate through snap rings; support plates are installed at the three top corners of the bottom mounting plate through hinges.

[0015] Further, a battery installation location is provided at the bottom of the bottom mounting plate, and the battery installation location is located between the left and right tail rotors.

[0016] Further, electronic speed controllers for the left and right tail rotors are provided above the bottom mounting plate, and an electronic speed controller for the top rotor is provided at the bottom of the bottom mounting plate.

[0017] Further, an optical encoder is installed on the passive rollers.

[0018] Further, the bottom mounting plate, the fuselage shell, the rotating rod and the support plate are made of carbon fiber composite materials, and the axle is made of aluminum alloy material.

[0019] On the other hand, the object of the present invention is achieved as follows: A control method for a three-rotor land-air amphibious robot, including the following steps:

[0020] 1) Establish dynamic models for two cases of flight state and ground movement state, and perform mode conversion by controlling the flight height of the amphibious robot;

[0021] 2) In the flight state, use the cascade PID control method, and adopt the method of combining two layers of PID of the inner and outer loops to control the output of the amphibious robot. The inner loop controls the three-axis torque and the increment of the Z-axis tension, and the outer loop controls the desired angle and height to ensure the stability of the fuselage attitude and the movement state;

[0022] 3) In the ground motion state, design an attitude controller. By changing the rotational speeds of the three rotors, the magnitude and direction of the lift generated by the rotors can be changed, and further the thrust direction of the fuselage on the passive rollers can be changed to achieve the movement of the amphibious robot on the ground;

[0023] 4) In the ground motion state, design a speed controller. By controlling the rotation angle of the passive rollers, the speed control of the amphibious robot in the ground mode can be achieved.

[0024] Furthermore, the specific steps of step 1) include: In the flight state, establish the earth coordinate system and the body coordinate system, and use the Newton-Euler method to establish the dynamic model to obtain the following dynamic equations:

[0025]

[0026] Among them, are the linear accelerations in each direction during flight, m is the mass of the robot, g is the acceleration due to gravity, J x , J y , J z are the moments of inertia of the body, φ, θ, ψ are the roll angle, pitch angle and yaw angle of the body in the flight state respectively, and μ is the tilting angle of the tail rotor; The expressions of U1, U2, U3, U4 are as follows:

[0027]

[0028] Among them, l1 and l3 are the distances from the first rotor and the third rotor to the center of gravity respectively, Ω i (i = 1, 2, 3) is the rotational speed of the i-th rotor, K T is the single-blade comprehensive thrust coefficient, K Q is the single-blade comprehensive torque coefficient;

[0029] In the ground motion state, establish the earth coordinate system and the moving coordinate system located at the center of mass, and use the Kane method to establish the roller dynamic model to obtain the following dynamic equations:

[0030]

[0031] Among them, R is the radius of the passive roller, J A and J C are the moments of inertia along the radial direction of the roller and along the p-axis direction respectively, are the roll angle, yaw angle of the body and the roller rotation angle in the ground motion state respectively, T is the torque acting on the roller axis along the n-axis direction of the body, f x is the component of the force of the roller axis on the roller along the n-axis direction of the body. Let β1 be the pitch angle of the frame, and the expressions of T and f x are as follows:

[0032]

[0033] The mutual conversion between the flight mode and the ground movement mode is achieved by controlling the flight altitude through the lift generated by the rotor, and the center of gravity height is z c , the roller radius is R. When the center of gravity height of the fuselage is equal to the product of the roller radius and the cosine value of the roll angle, that is, z c = Rcosθ1, when this limiting condition is met, the flight altitude is close to the wheel radius. At this time, the rotor speed is adjusted to reduce the lift generated by the rotor, and the pressure on the roller from the fuselage causes the roller to be subjected to the frictional force of the ground to roll, realizing the mode conversion.

[0034] Further, the specific content of step 2) includes: in the flight state, using the cascade PID control method, in the control system of the flight mode, the input is Θ d = [φ d , θ d , ψ d , z d , where φ d , θ d , ψ d are the expected attitude angles received from the remote controller respectively, and z d is the expected fuselage height. The actual quantities corresponding to φ d , θ d , ψ d and z d are Θ = [φ, θ, ψ, z] respectively. Differentiating Θ gives the velocity matrix where are the angular velocities of the three attitude angles respectively, is the velocity corresponding to the z-axis direction of the fuselage in the earth coordinate system;

[0035] Substitute the above angular quantities and height quantities into the controller for cascade PID calculation. The input of the outer loop is e(t) = Θ d - Θ(t), and the output is the expected velocity and angular velocity, denoted as The input of the inner loop is The output is the corresponding torque and force, denoted as:

[0036] a = [τ x , τ y , τ z , F z T

[0037] where τ x is the torque on the fuselage in the x-axis direction in the earth coordinate system, τ y is the torque on the fuselage in the y-axis direction in the earth coordinate system, τ z is the torque on the fuselage in the z-axis direction in the earth coordinate system, and F​z is the force acting on the body in the z-axis direction in the Earth coordinate system;

[0038] The input-output relationships of the PID controllers for the outer and inner loops are as follows:

[0039]

[0040] where, K p is the proportional gain of the PID controller, K I is the integral gain of the PID controller, K D is the derivative gain of the PID controller;

[0041] After the above calculations, the inner-loop PID controller obtains four outputs, and the relationships between these four outputs τ x , τ y , τ z , F z and the rotational speeds of each rotor and the tilt angle of the third rotor are as follows:

[0042]

[0043] The above equation is transformed into the following expression in matrix form:

[0044]

[0045] Briefly recorded as:

[0046] Δu δ = MΔu (8)

[0047] It means that the control output of the inner-loop PID controller is further transformed into Δu δ , and the physical meaning of Δu δ is the control increment that the three-rotor robot needs to change to reach the target state from the starting state. These control quantities respectively correspond to the three-axis torque increment and the z-axis tension increment; through the above formula derivation, the change amount Δu of the intermediate control variable is:

[0048] Δu = M -1 Δu δ

[0049] Based on the previously defined physical parameters, the initial control inputs u0 of the four motors are calculated, and u0 is set to the values of each input when the amphibious robot is hovering. The calculation process is as follows.

[0050] Initially, the torques in all directions are 0, and the expression of u δ is as follows:

[0051]

[0052] Solving equations (6) and (9) simultaneously gives the following results:

[0053] Ω 10 = Ω 20

[0054] θ0 = 0

[0055]

[0056] According to the above definitions and calculation results, the expression of u0 is as follows:

[0057]

[0058] where, Ω 10 , Ω 20 , Ω 30 are respectively the control quantities of the rotational speeds of the first rotor, the second rotor, and the third rotor input at the initial time;

[0059] Adding Δu and u0 gives the expression of the control signal u received by the motor controller:

[0060] u = u0 + Δu = [u1, u2, u3, u4] T (10)

[0061] where, u1, u2, u3, u4 are respectively the four components of the control signal u;

[0062] Solving equation (8) gives the rotational speeds Ω1, Ω2, Ω3 and the servo deflections μ as follows:

[0063]

[0064] According to the above control method and power distribution method, the control of the amphibious robot in the flight state is completed.

[0065] Furthermore, step 3) specifically includes: in the ground motion state, an attitude controller is designed, and the pitch angle, yaw angle, lift, and moment of the amphibious robot are determined as the performance indicators of system stability; the state variables and output vectors of the system are selected, and the state space is as shown in formula (12):

[0066]

[0067] θ k and ψ k are respectively the roll angle and yaw angle of the amphibious robot during ground motion; X k is the state vector of the system, Y k is the output vector of the system, A d is the system matrix, B d is the input matrix, E dLet U k-1 be the input control signal, which includes τ x be the moment acting on the body along the x-axis in the Earth coordinate system, τ y be the moment acting on the body along the y-axis in the Earth coordinate system, τ z be the moment acting on the body along the z-axis in the Earth coordinate system, f x be the force acting on the body along the x-axis in the Earth coordinate system, W k-1 be the feedforward vector, where are respectively f x , τ x , τ y , τ z the corresponding control feedforward quantities;

[0068] During ground movement, according to Euler's theorem, the relationship between the Euler angles in the above state space and the angular velocity measured by the flight control is shown in Equation (13), where is the pitch angle of the fuselage in the Cnmp coordinate system;

[0069]

[0070] From the above state space, it can be seen that the control objective of the attitude controller is the known reference attitude angle Θ d =[θ d , ψ d T , design the controller such that lim t→+∞ ||e Θ (t)|| = 0, where Θ d is the target roll angle and yaw angle, ω d is the ideal angular velocity;

[0071] In the attitude controller, the part based on model decomposition introduces Kane's equation as feedforward to cancel the influence of gravity and inertial forces; the part based on servo control adopts PD control to achieve rapid angle compensation; finally, the controller outputs the expected values of τ x and τ y to provide input for the next rotor power distribution.

[0072] Furthermore, step 4) specifically includes: designing a speed controller in the ground movement state, installing an optical encoder on the passive roller to measure the rotation angle of the roller, controlling the rotation angle of the passive roller to achieve the control of the speed of the amphibious robot in the ground mode, adopting the PD control method and introducing Kane's equation as feedforward, and the output of the entire system is the expected torque of the fuselage on the roller, and this torque is the expected value of τ z where φ​d For the target roll angle, design a controller such that lim t→+∞ ||e φ (t)|| = 0, Combining the moments output by attitude control and speed control, and performing power distribution on the rotors, the control of ground movement is completed.

[0073] The present invention adopts the above technical solutions. Compared with the prior art, the beneficial effects are as follows: 1) Improving the stability of the takeoff and landing of the amphibious robot: By adding a wheel design, the present invention enhances the ground support force of the robot, enabling the robot to achieve a smooth transition between ground and air flight; compared with traditional aircraft, the design of the present invention enables the robot to obtain stronger stability on the ground, reducing control problems caused by drift or stall.

[0074] 2) Enhancing the ground sliding ability of the robot: By adding a passive roller under the tri-rotor aircraft, the aircraft can slide on the ground; this design effectively solves the problem that existing aircraft cannot move effectively on the ground, especially in complex environments such as urban streets, mountainous areas or disaster areas. The present invention enables the robot to move on the ground without relying on the flight mode, improving the flexibility and adaptability of the task.

[0075] 3) Enhancing the efficiency of the robot: The design of the present invention enables the amphibious robot to replace part of the flight operation by passive ground sliding, thereby reducing the energy consumption of the aircraft. The robot can select a suitable mode for flight or ground sliding according to the task requirements. At the same time, after combining the ground movement mode, the robot can reduce the hovering time by sliding, further optimizing the energy utilization efficiency and increasing the endurance. The robot can efficiently complete the mode switching between flight and ground sliding, greatly improving the efficiency of task execution.

[0076] 4) Reducing costs and simplifying the structure: Compared with the complex multi-wheel design of existing land-air amphibious robots, the present invention significantly simplifies the structure of the amphibious robot by adding only one passive roller to the tri-rotor aircraft. The power coupling between the wheel and the rotor is simpler, and the control system becomes more intuitive. This not only reduces the manufacturing cost of the land-air amphibious robot but also reduces the maintenance difficulty. The simplified structure makes the robot more reliable during task execution and reduces the failure probability caused by the complex structure.

[0077] 5) Improve the adaptability of the robot to narrow spaces and complex terrains: By adding wheel designs, the robot of the present invention can move more flexibly in narrow spaces. Compared with robots with traditional four-wheel or multi-wheel designs, the single-wheel design of the present invention makes the robot smaller in size and more maneuverable in narrow environments. The robot can more easily cross city streets and building gaps, adapting to more complex task scenarios, especially in tasks such as disaster area search and rescue and building interior inspections that require the ability to adapt to narrow spaces, where it has obvious advantages. In complex terrains, the robot can quickly switch between flight mode and ground sliding mode, avoiding instability problems during flight and improving the performance of the aircraft in changing environments. Description of the Drawings

[0078] Figure 1 Schematic diagram of the structure of the amphibious robot of the present invention.

[0079] Figure 2 Schematic diagram of the structure of the amphibious robot of the present invention with the fuselage shell removed.

[0080] Figure 3 Bottom view of the amphibious robot of the present invention with the fuselage shell removed.

[0081] Figure 4 Schematic diagram of the principle of the flight state of the present invention.

[0082] Figure 5 Schematic diagram of the selection of various components of the dynamic system of the present invention.

[0083] Figure 6 Overall architecture diagram of the electric control system of the present invention.

[0084] Figure 7 Coordinate system transformation and Euler angle definition in the flight state of the present invention.

[0085] Figure 8 Coordinate system transformation and Euler angle definition in the ground motion state of the present invention.

[0086] Figure 9 Schematic diagram of the controller in the flight state of the present invention.

[0087] Figure 10 Schematic diagram of the attitude controller in the ground motion state of the present invention.

[0088] Figure 11 Schematic diagram of the speed controller in the ground motion state of the present invention.

[0089] Among them, 1 is the fuselage shell, 2 is the bottom mounting plate, 3 is the passive roller, 4 is the first rotor, 5 is the second rotor, 6 is the third rotor, 7 is the rotating rod, 8 is the rotor rotating servo, 9 is the rotor motor, 10 is the support plate, 11 is the photoelectric encoder, 12 is the axle, 13 is the first electronic speed controller, 14 is the second electronic speed controller, 15 is the third electronic speed controller, and 16 is the battery installation location. Specific implementation method

[0090] Such as Figures 1-3 A three-rotor type amphibious robot as shown, including a fuselage outer shell 1 and a fuselage body. The fuselage outer shell 1 is connected to the fuselage body by screws; the fuselage body includes a bottom mounting plate 2, a three-axis rotor, and a passive roller 3; the three-axis rotor is evenly distributed in a Y shape on the bottom mounting plate 2, which can reduce the degree of mutual interference of the airflow between the rotors and improve the stability and flight performance of the aircraft; the three-axis rotor includes a top rotor and the left and right rotors at the tail. The top rotor is connected to the rotor rotating servo 8 on the bottom mounting plate 2 through a rotating rod 7; the left and right rotors at the tail are installed on the bottom mounting plate through corresponding rotor motors 9; the top rotor is connected to the rotor rotating servo 8 through a rotating rod 7 and can be tilted to balance the counter-torque of the top rotor itself.

[0091] Such as Figure 4 As shown, the three rotors are numbered respectively. The top rotor is the third rotor 6, and the left and right sides of the tail are the second rotor 5 and the first rotor 4 respectively; the first rotor 4 rotates clockwise, and the second rotor 5 rotates counterclockwise. When their rotation speeds are equal, the two rotors can cancel the counter-torque with each other. The third rotor 6 rotates counterclockwise. It is connected to the rotor rotating servo 8 through a rotating rod 7 and can deflect to the left by a certain angle. The lift generated by the rotor will generate a tensile force component on the y-axis of the body, thereby generating a torque on the z-axis to cancel the counter-torque generated by the top rotor together with the lift generated by the three rotors, so that the body does not generate yaw motion; ensuring that the amphibious robot can maintain a stable flight state in the air.

[0092] The passive roller 3 is installed at the center position of the bottom mounting plate 3. The passive roller 3 is fixed on the axle 12 of the bottom mounting plate 2 by a circlip; making the overall center of gravity of the robot roughly located at the center of the axle 12. A photoelectric encoder 11 is also installed on the passive roller 3 to measure the roller rotation angle for further control; the mode conversion is carried out by controlling the flight height of the amphibious robot. When the center of gravity height of the body is equal to the product of the roller radius and the cosine value of the roll angle, the flight height is close to the radius of the roller. At this time, the rotation speeds of each rotor are adjusted to change the lift distribution, and the conversion between the flight and ground movement modes of the robot can be realized. The conversion method is more convenient and has higher efficiency. In the ground movement mode, the three rotors change the magnitude and direction of the lift by adjusting the rotation speed of the rotor motor 9, and then change the thrust direction of the fuselage on the passive roller, so that the roller drives the whole to realize linear and deflection movements on the ground.

[0093] At three top corners of the bottom mounting plate 2, support plates 10 are installed through one-way damping hinges. The one-way damping hinges have the function of positioning at any angle, enabling the support plates 10 to stop at any position during rotation. The three support plates 10 can be folded downwards when necessary, adding three contact points to the body and maintaining a stable shutdown state.

[0094] At the bottom of the bottom mounting plate 2, there is a battery installation area 16, which is located between the left and right rotors at the tail (between the first rotor 4 and the second rotor 5); above the bottom mounting plate 2, there are electronic speed controllers for the left and right rotors of the tail fin, including electronic speed controller one 13 and electronic speed controller two 14; at the bottom of the bottom mounting plate 2, there is an electronic speed controller three 15 for the top rotor; this makes the center of gravity of the body located at the center of the axle, thereby reducing power consumption and improving energy utilization efficiency. At the same time, it is for more convenient wiring.

[0095] The bottom mounting plate 2, the fuselage shell 1, the rotating rod 7 and the support plates 10 are made of carbon fiber composite materials, and the axle 12 is made of aluminum alloy material. While ensuring that the whole has sufficient stiffness and strength, a lightweight design of the structure is carried out. The fuselage shell 1 adopts a streamlined design for aerodynamic optimization, allowing the airflow to flow more smoothly over the body, reducing airflow separation and turbulence, effectively reducing aerodynamic drags such as pressure drag and frictional drag during movement, improving lift efficiency, reducing energy consumption, and at the same time reducing airflow disturbance during flight and enhancing flight stability.

[0096] After completing the design of the fuselage shell and the fuselage body, further select and layout the power system. Except for the power system, the weight of the frame and the load is about 988 grams. The selected endurance time is 10 minutes and the flight altitude is 4m. According to the model of the power system for design, the propellers, rotor motors, electronic speed controllers and batteries can be selected. The specific parameters are as Figure 5 shown.

[0097] The electronic control system of the present invention uses an MCU (Micro Control Unit) as the control center, selects the STM32F427VIT chip as the main control of the hardware control platform, and communicates with the motor through pulse width modulation technology and serial bus. In addition, a variety of attitude sensors such as a three-axis gyroscope, an accelerometer and a magnetometer are built into the hardware system to measure the Euler angles of the body. At the same time, an optical encoder is externally connected to the roller to measure the rolling angle of the passive roller. The specific connection method of the hardware system is as Figure 6As shown, the battery powers the flight control, motors, and servos through an ammeter. The flight control contains various sensors that can measure the attitude and acceleration of the airframe. At the same time, an external optical encoder is connected to measure the roller rotation angle. The flight control is connected to the rotor motors through electronic speed controllers (ESCs). The MCU controls the motors and servos by outputting PWM waves, and the ESCs amplify the PWM waves. The user sends control commands to the robot through a remote controller to transmit and record operation data. The design of this hardware system not only ensures the real-time and accuracy of the robot's operation but also provides reliable data support for its application in complex environments.

[0098] A control method for a three-rotor amphibious robot, comprising the following steps:

[0099] 1) Establish dynamic models for two cases, namely the flight state and the ground movement state, and perform mode conversion by controlling the flight altitude of the amphibious robot;

[0100] As Figure 7 shown, the present invention defines the earth coordinate system and the body coordinate system in the flight mode. O e x e y e z e is the earth coordinate system, and O b x b y b z b is the body coordinate system, with the counterclockwise direction being positive. In the flight state, the pitch angle is the angle θ rotated around the y e axis, the roll angle is the angle φ rotated around the x e axis, and the yaw angle is the angle ψ rotated around the z e axis.

[0101] In the flight state, establish the earth coordinate system and the body coordinate system, and use the Newton-Euler method to establish a dynamic model to obtain the following dynamic equations:

[0102]

[0103] Among them, is the linear acceleration in each direction during flight, m is the mass of the robot, g is the acceleration due to gravity, J x , J y , J z are the moments of inertia of the body, φ, θ, ψ are the roll angle, pitch angle, and yaw angle of the body in the flight state respectively, and μ is the tilt angle of the tail rotor; The expressions of U1, U2, U3, U4 are as follows:

[0104]

[0105] Among them, l1, l3 are the distances from the first rotor and the third rotor to the center of gravity respectively, Ω i(i = 1, 2, 3) is the rotational speed of the i-th rotor, K T is the comprehensive pulling force coefficient of a single rotor blade, K Q is the comprehensive torque coefficient of a single rotor blade; U1, U2, U3, U4 have no specific physical meaning, in order to simplify the above formula;

[0106] Such as Figure 8 As shown, the earth coordinate system defined by the present invention in the ground movement mode and the moving coordinate system fixedly connected to the center of mass, Oxyz is the earth coordinate system, Cnmp is the moving coordinate system fixedly connected to the center of mass, but it is not fixedly connected to the rollers; the yaw angle is defined as the rotation angle ψ1 around the z-axis, counterclockwise is positive; the roll angle is defined as the rotation angle θ1 around the n-axis, clockwise is positive; the roller rotation angle is defined as the rotation angle counterclockwise is positive;

[0107] In the ground movement state, establish the earth coordinate system and the moving coordinate system located at the center of mass, and use Kane's method to establish the roller dynamics model, and obtain the following dynamic equations:

[0108]

[0109] Among them, R is the radius of the passive roller, J A and J C are the moments of inertia along the radial direction of the roller and along the p-axis direction respectively, are the roll angle, yaw angle and roller rotation angle of the fuselage in the ground movement state respectively, T is the torque acting on the roller shaft along the n-axis direction of the fuselage, f x is the component of the force of the roller shaft on the roller along the n-axis direction of the fuselage. Let β1 be the pitch angle of the frame, and the expressions of T and f x are as follows:

[0110]

[0111] In the flight state, during vertical takeoff and landing, control the rotational speeds of the first rotor and the second rotor to be the same, and the third rotor tilts by a certain angle to balance the anti-torque in the z b axis direction of its own body coordinate system. At the same time, the fuselage has a small roll angle in the earth coordinate system to balance the force in the y b direction brought by the tilt of the third rotor. The lift forces of the three rotors have equal magnitudes of the components in the z e direction. When the sum of the components of the lift forces of the three rotors in the z e direction is greater than the gravity, the robot rises vertically. Otherwise, it descends vertically. When it is equal to the gravity, it hovers. During pitch movement, on the basis of the hovering state, the rotational speeds of the first rotor and the second rotor are still equal, but the lift forces of the two in the z eThe magnitude of the component force in the direction is not equal to that of the third rotor. At the same time, adjust the inclination angle of the third rotor to prevent the body from spinning. During the roll motion, based on the hovering state, the rotational speeds of the first rotor and the second rotor are different, causing the lift forces on the left and right sides of the body along the x b axis to be unequal. At the same time, adjust the inclination angle of the third rotor to prevent the body from spinning. During the yaw motion, based on the hovering state, the states of the first rotor and the second rotor remain unchanged. Adjust the rotational speed and inclination angle of the third rotor, and at the same time ensure that the lift force in the z e direction remains unchanged.

[0112] The mutual conversion between the flight mode and the ground motion mode is achieved by changing the lift force generated by the rotor to control the flight height. Let the center of gravity height be z c , the roller radius be R. When the center of gravity height of the body is equal to the product of the roller radius and the cosine value of the roll angle, that is, when z c = Rcosθ1, which meets this limiting condition, the flight height is close to the wheel radius. At this time, adjust the rotor rotational speed to reduce the lift force generated by the rotor, so that the pressure on the roller by the frame and thus the frictional force from the ground make it roll to achieve mode conversion.

[0113] In the ground motion state, the motion state of the linear motion on the ground is similar to the pitch motion during flight. The rotational speeds of the first rotor and the second rotor are equal, but the lift forces they generate along the z b axis are not equal to that of the third rotor, causing the frame to generate a thrust in the x direction on the roller shaft; the ground yaw motion is similar to the yaw motion during flight. Similarly, ensure that the rotational speeds of the first rotor and the second rotor are equal, and change the inclination angle of the third rotor so that the torque in the z b axis direction of the body is not zero, so that the yaw torque on the roller is also not zero, and the yaw motion can be completed.

[0114] 2) In the flight state, use the cascade PID control method, which combines the inner and outer loops of two-layer PID to control the output of the amphibious robot. The inner loop controls the three-axis torque and the increment of the Z-axis tension, and the outer loop controls the desired angle and height to ensure the stability of the fuselage attitude and motion state;

[0115] In the flight state, use the cascade PID control method. In the control system of the flight mode, the input is Θ d = [φ d , θ d , ψ d , z d , where φ d , θ d , ψ d are the desired attitude angles received from the remote control respectively, z d is the desired body height, φ d , θ d , ψ d and z dThe actual quantities corresponding to these expected values are respectively Θ = [φ, θ, ψ, z]. Differentiating Θ gives the velocity matrix where are the angular velocities of the three attitude angles respectively, is the velocity corresponding to the z-axis direction of the body in the earth coordinate system;

[0116] Substitute the above angular quantities and altitude quantity into the controller and perform cascade PID calculation in the manner as Figure 9 shown. For the cascade PID controller in the flight mode designed by the present invention, the altitude control loop for controlling the altitude z is above, where z d is the expected altitude of the body, and the attitude control loop for controlling the three Euler angles is below, [φ d θ d ψ d T are the expected values of the respective Euler angles, f and τ are the force and moment output by the inner loop respectively, Δu is the increment of the rotational speed of each rotor and the servo deflection angle after control distribution, and u0 is the set initial state value;

[0117] The input of the outer loop is e(t) = Θ d - Θ(t) and the output is the expected velocity and angular velocity, denoted as The input of the inner loop is and the output is the corresponding moment and force, denoted as:

[0118] a = [τ x , τ y , τ z , F z T

[0119] where, τ x is the moment of the body in the earth coordinate system along the x-axis direction, τ y is the moment of the body in the earth coordinate system along the y-axis direction, τ z is the moment of the body in the earth coordinate system along the z-axis direction, F z is the force of the body in the earth coordinate system along the z-axis direction;

[0120] The input-output relationships of the PID controllers of the outer loop and the inner loop are as follows:

[0121]

[0122] where, K p is the proportional gain of the PID controller, K I is the integral gain of the PID controller, K D is the derivative gain of the PID controller;

[0123] ​​After the above calculations, the inner-loop PID controller obtains four outputs, which are the four outputs τ x , τ y , τ z , F z The relationships with the rotational speeds of each rotor and the tilt angle of the third rotor are as follows:

[0124]

[0125] The above formula is transformed into an expression in the following matrix form:

[0126]

[0127] Briefly recorded as:

[0128] Δu δ = MΔu (8)

[0129] The meaning is that the control output of the inner-loop PID controller is further transformed into Δu δ , Δu δ The physical meaning of Δu is the control increment that the three-rotor robot needs to change to reach the target state from the starting state. These control quantities respectively correspond to the three-axis torque increment and the z-axis tension increment; through the above formula derivation, the change amount Δu of the intermediate control variable is:

[0130] Δu = M -1 Δu δ

[0131] Based on the previously defined physical parameters, the initial control inputs u0 of the four motors are calculated. u0 is set to the values of each input when the amphibious robot is hovering. The calculation process is as follows.

[0132] Initially, the torques in all directions are 0, and the expression of u δ is as follows:

[0133]

[0134] By simultaneously solving Equation (6) and Equation (9), the results are as follows:

[0135] Ω 10 = Ω 20

[0136] θ0 = 0

[0137]

[0138] According to the above definitions and calculation results, the expression of u0 is as follows:

[0139]

[0140] Among them, Ω 10, Ω 20 , Ω 30 are respectively the control quantities of the rotational speeds of the first rotor, the second rotor, and the third rotor input initially.

[0141] Adding Δu and u0 gives the expression of the control signal u received by the controller of the motor:

[0142] u = u0 + Δu = [u1, u2, u3, u4] T (10)

[0143] where u1, u2, u3, u4 are respectively the four components of the control signal u.

[0144] The rotational speeds Ω1, Ω2, Ω3 and the servo deflections μ are solved from Equation (8) as follows:

[0145]

[0146] According to the above control method and power distribution method, the control of the amphibious robot in the flight state is completed.

[0147] 3) In the ground motion state, design an attitude controller. By changing the rotational speeds of the three rotors, the magnitude and direction of the lift generated by the rotors are changed, and then the direction of the thrust of the fuselage on the passive rollers is changed to realize the movement of the amphibious robot on the ground;

[0148] In the ground motion state, an attitude controller is designed. The pitch angle, yaw angle, lift, and torque of the amphibious robot are determined as the performance indicators of system stability; select the state variables and output vector of the system. The state space is shown in Equation (12):

[0149]

[0150] θ k and ψ k are respectively the roll angle and yaw angle of the amphibious robot during ground motion; X k is the state vector of the system, Y k is the output vector of the system, A d is the system matrix, B d is the input matrix, E d is, U k-1 is the input control signal, which includes τ x is the torque acting on the fuselage in the x-axis direction in the Earth coordinate system, τ y is the torque acting on the fuselage in the y-axis direction in the Earth coordinate system, τ z is the torque acting on the fuselage in the z-axis direction in the Earth coordinate system, f x is the force acting on the fuselage in the x-axis direction in the Earth coordinate system, W k-1is the feedforward vector, where are f respectively x , τ x , τ y , τ z corresponding control feedforward quantities;

[0151] During the ground movement, the relationship between the Euler angles in the above state space and the angular velocity measured by the flight control is obtained by Euler's theorem as shown in Equation (13), where is the pitch angle of the airframe in the Cnmp coordinate system;

[0152]

[0153] It can be seen from the above state space that the control objective of the attitude controller is the known reference attitude angle Θ d =[θ d , ψ d T , design the controller such that lim t→+∞ ||e Θ (t)|| = 0, where Θ d is the target roll angle and yaw angle, ω d is the ideal angular velocity;

[0154] Therefore, based on the above equations, design the attitude controller for the ground mode of the tri-rotor UAV as Figure 10 shown. The attitude control block diagram designed in the present invention adopts PD control and introduces Kane's equation as feedforward. θ1 and ψ1 are the roll angle and yaw angle defined in the ground mode respectively, and θ 1d and ψ 1d are their ideal values respectively, are the proportional and differential parameters of the PD control respectively, and the corresponding input τ x , τ y The expressions are as follows:

[0155]

[0156] In the attitude controller, Kane's equation is introduced as feedforward in the part based on model decomposition to offset the influence of gravity and inertial forces; PD control is adopted in the part based on servo control to achieve fast compensation of angles; finally, the controller outputs the expected values of τ x and τ y to provide input for the next rotor power distribution.

[0157] 4) In the ground movement state, design a speed controller to achieve speed control of the amphibious robot in the ground mode by controlling the rotation angle of the passive roller. ​

[0158] Design a speed controller for the ground motion state. Install an optoelectronic encoder on the passive roller to measure the rotation angle of the roller, and control the speed of the amphibious robot in the ground mode by controlling the rotation angle of the passive roller. Adopt the PD control method and introduce the Kane equation as the feedforward. The output of the entire system is the expected torque of the frame on the roller, and this torque is τ z The expected value of, where φ d Is the target rolling angle, design the controller Make lim t→+∞ ||e φ (t)|| = 0, Combine the torques output by the attitude control and the speed control, and perform power distribution on the rotors, then the control of the ground motion is completed.

[0159] The specific architecture of the speed controller is as shown in Figure 11 The ground mode speed control block diagram designed in the present invention, Is the rotation angle of the passive roller defined in the ground mode, Is its ideal value, Are the proportional and differential parameters of the PD control, and the corresponding input τ z The expression is as follows:

[0160]

[0161] The present invention provides a three-rotor land-air amphibious robot and its control method. The robot body is composed of a Y-shaped three-axis rotorcraft equipped with passive rollers. The Y-shaped layout of the three-axis rotorcraft is relatively compact, which can reduce the degree of mutual interference of the airflow between the rotors and improve the stability and flight performance of the aircraft. By adjusting the rotation speed of each rotor motor, the lift and torque are changed, and an amphibious movement mode with both flight ability and ground movement ability is realized. At the same time, the present invention can establish the dynamic equation in the flight state through the Newton-Euler method and establish the dynamic equation in the ground movement by using the Kane method. In the flight mode, the inner and outer loop two-layer PID control is combined. The inner loop controls the three-axis torque and the Z-axis tension increment, and the outer loop controls the expected angle and height to ensure the stability of the UAV attitude and movement state; install an optoelectronic encoder on the passive roller to measure the roller rotation angle and realize the speed control in the ground movement mode. The attitude controller and the speed controller in the ground mode both introduce the Kane equation as the feedforward and adopt PD control to achieve rapid angle compensation.

[0162] The present invention is not limited to the above embodiments. Based on the technical solutions disclosed in the present invention, those skilled in the art can make some substitutions and deformations to some technical features without creative labor according to the disclosed technical content, and these substitutions and deformations are all within the protection scope of the present invention.

Claims

1. A three-rotor amphibious robot, characterized in that: It includes a fuselage shell and a fuselage body, and the fuselage shell is connected to the fuselage body through a fixing piece; the fuselage body includes a bottom mounting plate, a three-axis rotor and a passive roller; the three-axis rotor is Y-shaped and evenly distributed on the bottom mounting plate; the three-axis rotor includes a top rotor and left and right rotors at the tail, and the top rotor is connected to the rotor rotating servo on the bottom mounting plate through a rotating rod; the left and right rotors at the tail are mounted on the bottom mounting plate through corresponding rotor motors; the passive roller is mounted at the center of the bottom mounting plate, and the passive roller is fixed to the wheel axle of the bottom mounting plate through a retaining spring; support plates are installed at the three top corners of the bottom mounting plate through hinges.

2. A three-rotor amphibious robot according to claim 1, characterized in that: A battery installation location is provided at the bottom of the bottom mounting plate, and the battery installation location is located between the left and right rotors of the tail.

3. The three-rotor amphibious robot according to claim 1, characterized in that: The electric regulators of the left and right rotors of the tail wing are arranged above the bottom mounting plate, and the electric regulator of the top rotor is arranged at the bottom of the bottom mounting plate.

4. The three-rotor amphibious robot according to claim 1, characterized in that: A photoelectric encoder is installed on the passive roller.

5. The three-rotor amphibious robot according to claim 1, characterized in that: The bottom mounting plate, the fuselage shell, the rotating rod and the supporting plate are made of carbon fiber composite materials, and the wheel axle is made of aluminum alloy material.

6. A control method for a three-rotor amphibious robot, characterized in that: The following steps are involved: 1) Establish dynamic models of the flight state and ground motion state, and perform mode conversion by controlling the flight altitude of the amphibious robot; 2) In the flight state, the cascade PID control method is used to control the output of the amphibious robot by combining the inner and outer loops. The inner loop controls the three-axis torque and the Z-axis tension increment, and the outer loop controls the desired angle and height to ensure the stability of the fuselage posture and motion state. 3) In the ground motion state, design an attitude controller to change the rotation speed of the three rotors, thereby changing the magnitude and direction of the lift generated by the rotors, and then changing the thrust direction of the fuselage on the passive rollers to achieve the motion of the amphibious robot on the ground; 4) In the ground motion state, a speed controller is designed to achieve speed control of the amphibious robot in ground mode by controlling the rotation angle of the passive roller.

7. The control method of a three-rotor amphibious robot according to claim 6, characterized in that: The step 1) specifically includes: in the flight state, establishing the earth coordinate system and the body coordinate system, using the Newton-Euler method to establish a dynamic model, and obtaining the following dynamic equation: in, is the linear acceleration in all directions during flight, m ​​is the mass of the robot, g is the acceleration due to gravity, J x ,J y ,J z is the moment of inertia of the fuselage, φ, θ, ψ are the roll angle, pitch angle and yaw angle of the fuselage in flight, μ is the tilt angle of the tail rotor; the expressions of U1, U2, U3, U4 are as follows: Among them, l1 and l3 are the distances from rotor No. 1 and rotor No. 3 to the center of gravity, Ω i , i=1,2,3 is the speed of the i-th rotor, K T is the comprehensive pulling force coefficient of a single propeller, K Q is the comprehensive moment coefficient of single propeller; Under the ground motion state, the earth coordinate system and the moving coordinate system at the center of mass are established, and the roller dynamics model is established using the Kane method to obtain the following dynamic equation: Where R is the radius of the passive roller, J A and J C The moments of inertia along the roller radial direction and along the p-axis direction are θ1, ψ1, are the roll angle, yaw angle and roller angle of the aircraft under ground motion state, T is the moment acting on the roller axis along the n-axis direction of the aircraft, f x is the force component of the roller shaft on the roller along the n-axis direction of the body, let β1 be the pitch angle of the frame, T and f x The expression is as follows: By changing the lift generated by the rotor to control the flight altitude, the flight mode and ground motion mode can be converted to each other, and the center of gravity height is z c , the roller radius is R, when the height of the body's center of gravity is equal to the product of the roller radius and the cosine value of the roll angle, that is, z c =Rcosθ1, the flight altitude is close to the wheel radius. At this time, the rotor speed is adjusted to reduce the lift generated by the rotor. The roller is subjected to the pressure of the frame and the friction of the ground to make it roll to achieve mode conversion.

8. The control method of a three-rotor amphibious robot according to claim 6, characterized in that: The step 2) specifically includes: in the flight state, using the cascade PID control method, in the control system of the flight mode, the input is θ d =[φ d ,θ d ,ψ d ,z d ],φ d ,θ d , ψ d are the expected attitude angles received from the remote controller, z d is the expected fuselage height, φ d ,θ d , ψ d and z d The actual quantities corresponding to these expected values ​​are Θ = [φ, θ, ψ, z], and the velocity matrix is ​​obtained by differentiating Θ in They are the three attitude angles and angular velocities, is the velocity of the body corresponding to the z-axis direction in the earth coordinate system; The above angle and height values ​​are brought into the controller for cascade PID calculation, and the outer loop input is e(t) = Θ d -Θ(t) to get the desired speed and angular velocity, denoted as The inner loop input is The output is the corresponding torque and force, recorded as: a=[τ x ,t y ,t z ,F z ] T Among them, τ x is the moment of force on the body along the x-axis in the earth coordinate system, τ y is the moment of force on the body along the y-axis in the earth coordinate system, τ z is the moment of force on the body along the z-axis in the earth coordinate system, F z is the force on the body along the z-axis in the earth coordinate system; The input-output relationship of the outer and inner loop PID controllers is as follows: Among them, K p is the proportional gain of the PID controller, K I is the integral gain of the PID controller, K D is the differential gain of the PID controller; After the above calculation, the inner loop PID controller obtains four outputs. These four outputs τ x ,τ y ,τ z ,F z The relationship between the rotation speed of each rotor and the tilt angle of rotor No. 3 is as follows: The above formula is transformed into the following matrix form: In short: Δu δ =MΔu (8) The control output of the inner loop PID controller is further converted into Δu δ , Δu δ The physical meaning of is the control increment that needs to be changed from the starting state to the target state of the three-rotor robot. These control quantities correspond to the three-axis torque increment and the z-axis tension increment respectively. The change Δu of the intermediate control variable is derived from the above formula: Δu=M -1 Thu δ The initial control input u0 of the four motors is calculated based on the previously defined physical parameters. u0 is set as the value of each input of the amphibious robot when it is hovering. The calculation process is as follows. Initially, the torque in each direction is 0, u δ The expression is as follows: The solution of equation (6) and equation (9) is as follows: Oh 10 =Oh 20 θ0=0 According to the above definition and calculation results, the expression of u0 is as follows: Among them, Ω 10 ,Ω 20 ,Ω 30 are the control quantities of the rotation speeds of rotor No. 1, rotor No. 2 and rotor No. 3 respectively inputted at the initial stage; Adding Δu to u0 gives the expression for the control signal u received by the motor controller: uu0+Δu[u1,u2,u3,u4] T (10) Among them, u1, u2, u3, and u4 are the four components of the control signal u; The speed Ω1, Ω2, Ω3 and the steering gear deflection angle μ are obtained by solving equation (8) as follows: According to the above control method and power distribution method, the control of the amphibious robot in flight state is completed.

9. The control method of a three-rotor amphibious robot according to claim 6, characterized in that: The step 3) specifically includes: in the ground motion state, a posture controller is designed, and the pitch angle, yaw angle, lift and torque of the amphibious robot are determined as performance indicators of system stability; the state variables and output vectors of the system are selected, and the state space is shown in formula (12): θ k and ψ k are the roll angle and yaw angle of the amphibious robot when moving on the ground; X k is the state vector of the system, Y k is the output vector of the system, A d is the system matrix, B d is the input matrix, E d For U k-1 is the input control signal, which includes τ x is the moment of force on the body along the x-axis in the earth coordinate system, τ y is the moment of force on the body along the y-axis in the earth coordinate system, τ z is the moment along the z-axis in the earth coordinate system, f x is the force along the x-axis in the earth coordinate system on the body, W k-1 is the feedforward vector, where f x , τ x , τ y , τ z The corresponding control feedforward amount; During ground motion, the relationship between the Euler angle in the above state space and the angular velocity measured by the flight control is obtained by Euler's theorem as shown in equation (13), where is the pitch angle of the rack in the Cnmp coordinate system; From the above state space, we can see that the control target of the attitude controller is the known reference attitude angle θ d =[θ d ,ψ d ] T , design controller Make lim t→+∞ ||e Θ (t)||=0, where Θ d are the target roll angle and yaw angle, ω d is the ideal angular velocity; In the attitude controller, the part based on model decomposition introduces the Kane equation as feedforward to offset the influence of gravity and inertia; the part based on servo control adopts PD control to achieve rapid compensation of angle; the final controller output τ x and τ y The expected value provides input for the next step of rotor power distribution.

10. The control method of a three-rotor amphibious robot according to claim 9, characterized in that: The step 4) specifically includes: designing a speed controller in the ground motion state, installing a photoelectric encoder on the passive roller to measure the rotation angle of the roller, and controlling the rotation angle of the passive roller to achieve speed control of the amphibious robot in the ground mode, using PD control and introducing the Kane equation as feedforward, the output of the entire system is the desired torque of the frame on the roller, and the torque is τ z The expected value of d Design a controller for the target roll angle Make lim t→+∞ ||e φ (t)||=0, By combining the torque output by attitude control and speed control and distributing power to the rotor, ground motion control is completed.

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