A land-air amphibious robot platform rotor flywheel and control method thereof

Abstract

The present invention discloses a rotor flywheel for an amphibious robot platform in the field of unmanned aerial vehicles and a control method thereof, comprising an inner ring structure and an outer ring structure, wherein the inner ring structure is arranged in the outer ring structure, and the inner ring structure and the outer ring structure are connected by a rolling mechanism, a plurality of landing gears are arranged at the bottom of the outer ring structure, a forward rotor mechanism is arranged at the upper part of the inner ring structure, and a reverse rotor mechanism is arranged at the lower part of the inner ring structure, the forward rotor mechanism and the reverse rotor mechanism are symmetrical to each other, a control mechanism is also arranged on the inner ring structure, and the outer periphery of the outer ring structure is also covered with a circle of unicycle shell; eight rotors are used for flight control, with a simple structure and high maneuverability, and the forward and reverse rotor mechanisms can generate forward and reverse thrusts respectively, so as to quickly change the direction of the thrust and control the stability of the posture of the body; the unicycle shell contacts the ground, and is a rolling structure with a high center of gravity and a single fulcrum, which is less disturbed by terrain fluctuations during rolling and has flexible obstacle-crossing capability.

Description

Technical Field

[0001] The present invention relates to a rotor flywheel in the field of unmanned aerial vehicles and a control method thereof. Background Art

[0002] Existing amphibious drones (UAVs) use forward and reverse propeller rotation to generate forward and reverse thrust for takeoff and landing. However, the aerodynamic shape of the propeller blades currently generates greater forward thrust when rotating forward and less reverse thrust when rotating reversely. This reduces aerodynamic efficiency, resulting in increased energy consumption for the same thrust, longer delays in achieving stable thrust, and the need for a bidirectional electronic speed regulator for control. These drones suffer from rapid battery drain, slow response times for changing thrust to change direction, and, on the ground, are mostly four-wheeled, relatively small wheels that have limited ability to overcome obstacles on narrow and rugged roads. This results in insufficient cross-media mobility and limited flexibility. Summary of the Invention

[0003] The purpose of the present invention is to provide a rotor flywheel for a land-air amphibious robot platform and a control method thereof, which has cross-medium movement capability, good flexibility, lower energy consumption, and higher safety and reliability.

[0004] To achieve the above objectives, the present invention provides a rotor flywheel for an amphibious robot platform, comprising an inner ring structure and an outer ring structure. The inner ring structure is disposed within the outer ring structure, and the inner and outer ring structures are connected via a rolling mechanism. A plurality of landing gears are disposed at the bottom of the outer ring structure. A forward rotor mechanism is disposed at the upper portion of the inner ring structure, and a reverse rotor mechanism is disposed at the lower portion of the inner ring structure. The forward rotor mechanism and the reverse rotor mechanism are symmetrical to each other. A control mechanism is also disposed on the inner ring structure, and the outer circumference of the outer ring structure is further covered with a unicycle housing.

[0005] The outer ring structure includes an upper outer roller ring and a lower outer roller ring, the outer edges of which are connected by an outer column, and the outer shell of the wheel covers the outer circumference between the upper and lower outer roller rings; the landing gear is connected to the bottom of the lower outer roller ring, and there are four landing gears evenly distributed on the same circumference of the lower outer roller ring; the inner ring structure includes an upper inner ring frame and a lower inner ring frame, which are connected by an inner column, and the upper inner ring frame, the lower inner ring frame, the upper outer roller ring and the lower outer roller ring are concentrically arranged;

[0006] The rolling mechanism includes a rolling motor and a concentric shaft. The rolling motor is installed in the center of the upper inner ring frame. The shaft end of the rolling motor extends out of the upper inner ring frame and is connected to the center of the upper outer rolling ring. The two ends of the concentric shaft are respectively connected to the center of the bottom of the lower inner ring frame and the center of the lower outer rolling ring.

[0007] Compared with the prior art, the beneficial effects of the present invention are that it adopts a wheeled control structure, which is in contact with the ground and has the characteristics of shock absorption, easy control, and light weight. At the same time, it has a strong obstacle-crossing ability on uneven ground; it adopts eight-rotor control in flight, which has a simple structure and high maneuverability. Through the forward and reverse rotor mechanisms, it can generate forward and reverse thrust respectively, so as to quickly change the direction of the thrust and control the stability of the body's posture; it is in contact with the ground through a single wheel shell, which is a rolling structure with a high center of gravity and a single fulcrum. It is less disturbed by terrain undulations during rolling and has flexible obstacle-crossing ability.

[0008] As a further improvement of the present invention, the forward rotor mechanism includes four forward motors, which are evenly distributed on the same circumference within the upper inner ring frame. The shaft ends of the forward motors are equipped with forward blades, and the direction of the forward blades is facing the upper outer rolling ring; the reverse rotor mechanism includes four reverse motors, which are evenly distributed on the same circumference within the lower inner ring frame. The shaft ends of the reverse motors are equipped with reverse blades, and the direction of the reverse blades is facing the lower outer rolling ring.

[0009] In this way, in flight mode, the four rotors work in the same direction to generate thrust in the opposite direction of gravity for takeoff; in ground motion mode, only one of the two coaxial rotors works at the same time to generate thrust in the positive and negative directions, so that the direction of thrust can be changed quickly to control the stability of the aircraft's attitude.

[0010] As a further improvement of the present invention, the control mechanism includes an IMU, a controller, a control circuit board, a battery and a camera, wherein the IMU and the controller are placed at the top center of the lower inner ring frame, the control circuit board is arranged in the upper inner ring frame and is close to the rolling motor; the battery is installed in the center of the lower inner ring frame, and the camera is arranged at the end of the battery.

[0011] In this way, the entire control mechanism can be reasonably distributed in the rotor flywheel, so that the entire control mechanism can work normally and the weight can be evenly distributed, making it more stable during flight and rolling.

[0012] To achieve the above objectives, the present invention also provides a control method for a rotor flywheel of an amphibious robot platform, which includes the following contents: step 1, establishment of motion mode and coordinate system; step 2, control allocation; step 3, dynamic modeling; step 4, establishment of a rotor flywheel control system.

[0013] Compared with the prior art, the present invention has the advantage that the rotor flywheel's operation process includes flight, mode switching, and ground rolling. Due to the complex operating conditions, especially during mode switching and ground rolling, it is necessary to find a reasonable model to describe the rotor flywheel's dynamic characteristics under different driving conditions. Therefore, a complete motion pattern polar coordinate is established, and the dynamic model is built based on this, and the control system is established to achieve flight and ground rolling control.

[0014] As a further improvement of the present invention, the specific content of step 1 is as follows:

[0015] Establish a world coordinate system. The world coordinate system is divided into coordinate system Body_1 and coordinate system Body_2. Coordinate system Body_1 and coordinate system Body_2 correspond to the aerial flight mode and ground motion mode respectively. The aerial flight mode and ground motion mode are switched to each other through the switching mode.

[0016] Among them, the three coordinate directions in the earth coordinate system are e x, e y, e z, three-coordinate directions in the Body_1 coordinate system Three coordinate directions in Body_2 coordinate system

[0017] As a further improvement of the present invention, the specific content of step 2 is as follows:

[0018] In flight mode, the forward, backward, left, and right motion of the rotor flywheel depends on the thrust generated by the rotor. In ground mode, its forward and backward rolling motion depends on the rolling motor located in the center. The control distribution equation is as follows:

[0019]

[0020] set then

[0021]

[0022]

[0023] in, The angle between the axis and the support arm where the rotor is located, unit: deg; d: the distance between the center of the coordinate system O and the projection of the rotor on the xoy plane, unit: m; f i :The i-th motor edge The thrust generated by the shaft, unit: N; f: total thrust of the body, satisfying Unit: N; τ x ,τ y ,τ z, the total torque of the body, Decomposed in different directions, unit: N·m; c T : Speed-force proportional coefficient; c M : thrust-torque proportional coefficient; Stable rotor speed, unit: rad / s; P a : Coefficient matrix, which is the unit matrix; M4(1,1,1): Distribution matrix, each entry is 1 or -1.

[0024] As a further improvement of the present invention, the specific content of step 3 is as follows:

[0025] Step 3.1, flight dynamics modeling based on the Newton-Euler method. The flight mode dynamics model is modeled by the Newton-Euler method as follows:

[0026]

[0027] The first two columns describe the relationship between the position change of the rotor flywheel and the output of the total thrust, and the last two columns describe the relationship between the attitude change of the rotor flywheel and the output of the torque;

[0028] In the above formula, m is the total mass of the drone, in kg; g is the acceleration due to gravity, in m / s 2 ; J,: inertia matrix with respect to the body coordinate system, unit kg·m 2 R, the rotation matrix from the body coordinate system to the inertial coordinate system: b ω: angular velocity in the Body_1 coordinate system, unit rad / s; Θ: Euler angle in the Body_1 coordinate system, unit rad; W: transformation matrix between Euler angle derivative and angular velocity in the Body_1 coordinate system; ep: position of the center of mass in the Earth coordinate system, unit m; e v: velocity of the center of mass in the Earth coordinate system, unit: m / s; τ: total torque generated by the rotor, unit: N·m; G a : Gyroscopic torque generated by rotor rotation, unit: N·m;

[0029] Step 3.2: The ground mode dynamics model is modeled by the Kane method:

[0030]

[0031]

[0032] When the body thrust fi and Euler angle and angular velocity are set The rolling state of the rotor flywheel can be calculated; these nonlinear second-order differential equations describe the rolling state of the rotor flywheel at θ, The dynamic behaviors in the three directions of ψ and φ provide a model for control;

[0033] Wherein, n axis: Body_2 coordinate system Direction, m-axis: Body_2 coordinate system Direction; p-axis: in the Body_2 coordinate system Direction, R: total radius of the UAV's circular shell, unit: m; A, C: moment of inertia of the body about the n, m, and p axes J = diag (AAC), unit: kg·m 2 ; ψ: rolling heading angle, unit: rad; θ: attitude pitch angle, 0° in flight mode and 90° in ground mode, unit: rad; Roll angle, which describes the rolling distance, unit: rad; T: rolling motor output torque, unit: N·m; f: ground friction, unit: N;

[0034] In order to save energy and increase endurance when the rotor flywheel is rolling, do not let the rotor motor work and only use the rolling motor, that is, f i = 0, T = 0; because the rotor relies on high-speed compressed air to generate thrust to maintain its rolling upright posture, this will generate a large amount of heat loss and battery energy consumption; while the torque of the rolling motor directly acts on the outer ring of the rotor flywheel to drive it to roll, which is energy efficient; the dynamic equation at this time is as follows:

[0035]

[0036] When the four thrusts of the body maintain the changing rules When M is a constant, the torque in the yaw direction can be stably generated to control the rolling direction.

[0037] As a further improvement of the present invention, the specific content of step 4 is as follows:

[0038] After modeling the two motion modes of the rotor flywheel, consideration is given to selecting an appropriate controller to maintain the stability of the flywheel motion. The rotor flywheel's Euler angles, body angular velocity, and body acceleration state quantities can be used to observe the motion control effect. Since mode switching and rolling actions are more complex, they are selected for analysis and control.

[0039] To meet the controller feedback requirements, the rotor flywheel pitch, yaw, force, and torque are important performance indicators of system stability. The state variables and output vectors of the system are selected; the state space is shown below:

[0040]

[0041] Indicates the status of the system

[0042] U k-1 =[f τ x τy τ z ] T , represents the control input of the system

[0043] Represents the disturbance of the system

[0044] Y k Represents the output of the system

[0045] The aerial flight mode, ground rolling attitude stabilization, and air-to-ground mode switching actions are controlled primarily by the air thrust generated by the rotors. For air-to-ground mode switching, the state variable is the pitch angle of the Body_1 coordinate system, which enables a rotation of 0 to 90°. For ground mode steering, the main state variable is the yaw angle of the Body_2 coordinate system, which enables control in the predetermined direction.

[0046] As a further improvement of the present invention, the specific contents of switching from flight mode to ground mode in step 4 are as follows:

[0047] The motion state when switching from flight mode to ground mode is: mode switch-roll-turn.

[0048] The control goal of the “flight-ground” mode switch is to know the reference attitude angle Θ after the UAV lands. d =θ d , design the controller Make lim t→+∞ ||e Θ (t)||=0, where Θ d is the target pitch angle; the pitch angle is expected to be 0 degrees in flight mode and 90 degrees in ground mode; the dynamic model for air-to-ground mode switching is:

[0049]

[0050] The angle-angular velocity dual-loop PID controller is used to control the pitch angle of the rotor flywheel by considering the influence of the nonlinear term in the Kane equation.

[0051] Design expected angular velocity Expected torque

[0052] Finally, the desired force and torque vectors in the body_1 coordinate system are obtained, which are converted into rotor motor throttle commands through the power distribution matrix and the electronic control link for output;

[0053] The rolling steering direction control target is the known reference attitude angle Θ d =ψ d , design the controller Make lim t→+∞ ||eΘ (t)||=0, where Θ d is the target yaw angle; the pitch angle is expected to be zero when landing and 90 degrees when rolling; the dynamic model of rolling direction control is

[0054]

[0055] Scroll speed control:

[0056] Since the forward roll action is assumed to be decoupled from the rotor, the roll motion within the body_2 frame is controlled only by the roll motor. The roll motion control strategy aims to maintain a stable roll velocity;

[0057] The inverted pendulum dynamics model shows that the outer ring speed is related to the angle between the center of gravity and the direction of gravity. The larger the angle, the greater the torque provided by gravity, and the greater the torque acting on the outer ring through the rolling motor, which can accelerate the outer ring's rolling. Therefore, a three-loop PID controller is implemented because it is more conducive to achieving the control goal of a single state.

[0058] Step 1, in the outermost outer ring speed control, the outer ring speed calculation formula is as follows:

[0059]

[0060] --The relative angular velocity of the inner and outer rings is obtained by the encoder of the rolling motor,

[0061] --The angular velocity of the outer ring in the Earth coordinate system is derived by the formula,

[0062] --The inner circle angular velocity in the Earth coordinate system is obtained by the roll angle of the IMU,

[0063] With the feedback of the outer ring speed, stable speed control can be achieved through the P controller;

[0064] Step 2: A closed-loop control of the inner ring position was designed using a PD controller. The roll angle feedback from the IMU stabilizes the inner ring position of the flywheel. Furthermore, a camera is mounted on the inner ring of the flywheel; maintaining this position improves video quality. The PD controller is used to compensate for oscillations caused by the nonlinear term in the torque generated by gravity, ensuring early response and a degree of intelligent predictability.

[0065] Step 3: Use a PI controller to design a closed-loop control of the inner ring angular velocity. The rolling speed is fed back by the IMU. Since there is an error in the mechanical mean value of the flywheel inner ring, an integral term is introduced to eliminate it.

[0066] After the cascade PID, the output is the control current value of the rolling motor, which is sent to the rolling motor through the ESC to drive the motor to rotate.

[0067] As a further improvement of the present invention, the specific contents of the transition from ground mode to flight mode in step 4 are as follows:

[0068] From ground mode to flight mode: mode switching - takeoff - flight attitude control;

[0069] The control goal of the “ground-to-flight” mode switch is to flip the upright rotor flywheel to the take-off attitude. d =θ d , design the controller Make lim t→+∞ ||e Θ (t)||=0, where Θ d is the target pitch angle; in ground mode, it is 90 degrees, and in flight mode, the pitch angle is expected to be 0. The dynamic model of air-to-ground mode switching is:

[0070]

[0071] Flight altitude and attitude control

[0072] The desired center of mass position p of the rotor flywheel d (t) follows the target trajectory and the desired yaw angle ψ d Follow the desired direction of the target trajectory;

[0073] The translational motion of the quadrotor drone is determined by the total thrust f d The total thrust is directly controlled, which is the sum of the thrusts generated by the four motors. The direction of the total thrust is along the body coordinate axis. negative direction; therefore, in obtaining the desired trajectory p d After (t), the controller controls the total thrust and yaw direction ψ d to determine the translational motion of the quadrotor; the controller then follows this desired pose by controlling the torque τ. BRIEF DESCRIPTION OF THE DRAWINGS

[0074] Figure 1 It is a structural schematic diagram of the present invention.

[0075] Figure 2 It is a schematic diagram of the overall framework and internal structure of the present invention.

[0076] Figure 3 This is a hardware schematic diagram of the rotor flywheel of the present invention.

[0077] Figure 4This is a diagram defining the motion mode of the rotor flywheel of the present invention.

[0078] Figure 5 Schematic diagram of the reference coordinate system position of the rotor flywheel system of the present invention.

[0079] Figure 6 This is a rolling dynamics analysis diagram of the present invention.

[0080] Figure 7 This is a flow chart of the rotor flywheel mode switching and rolling direction control method of the present invention.

[0081] Figure 8 This is a flow chart of the rotor flywheel rolling speed control method of the present invention.

[0082] Figure 9 This is a flow chart of the rotor flywheel flight control method of the present invention.

[0083] Among them: 1 unicycle shell, 2 landing gear, 3 lower outer roller, 4 lower inner frame, 5 camera, 6 battery, 7 concentric shaft, 8 reverse motor, 9 inner column, 10 reverse blade, 11 outer column, 12 forward blade, 13 forward motor, 14 upper inner frame, 15 IMU and controller, 16 rolling motor, 17 control circuit board, 18 upper outer roller. DETAILED DESCRIPTION

[0084] The present invention will be further described below in conjunction with the accompanying drawings:

[0085] like Figure 1-3 The rotor flywheel of a land-air amphibious robot platform shown in the figure includes an inner ring structure and an outer ring structure. The inner ring structure is arranged in the outer ring structure. The inner ring structure and the outer ring structure are connected by a rolling mechanism. Multiple landing gears 2 are arranged at the bottom of the outer ring structure. A forward rotor mechanism is arranged on the upper part of the inner ring structure, and a reverse rotor mechanism is arranged on the lower part of the inner ring structure. The forward rotor mechanism and the reverse rotor mechanism are symmetrical to each other. A control mechanism is also arranged on the inner ring structure, and the outer periphery of the outer ring structure is also covered with a circle of single wheel shell 1.

[0086] The outer ring structure includes an upper outer roller ring 18 and a lower outer roller ring 3. The outer edges of the upper outer roller ring 18 and the lower outer roller ring 3 are connected by an outer column 11. The wheel shell 1 covers the outer circumference between the upper outer roller ring 18 and the lower outer roller ring 3. The landing gear 2 is connected to the bottom of the lower outer roller ring 3. There are four landing gears 2 and they are evenly distributed on the same circumference of the lower outer roller ring 3. The inner ring structure includes an upper inner ring frame 14 and a lower inner ring frame 4. The upper inner ring frame 14 and the lower inner ring frame 4 are connected by an inner column 9. The upper inner ring frame 14, the lower inner ring frame 4, the upper outer roller ring 18 and the lower outer roller ring 3 are concentrically arranged.

[0087] The rolling mechanism includes a rolling motor 16 and a concentric shaft 7. The rolling motor 16 is installed in the center of the upper inner ring frame 14. The shaft end of the rolling motor 16 extends out of the upper inner ring frame 14 and is connected to the center of the upper outer roller ring 18. The two ends of the concentric shaft 7 are respectively connected to the center of the bottom of the lower inner ring frame 4 and the center of the lower outer roller ring 3.

[0088] The forward rotor mechanism includes four forward motors 13, which are evenly distributed on the same circumference within the upper inner ring frame 14. The shaft end of the forward motor 13 is equipped with a forward blade 12, and the direction of the forward blade 12 is facing the upper outer roller ring 18; the reverse rotor mechanism includes four reverse motors 8, which are evenly distributed on the same circumference within the lower inner ring frame 4. The shaft end of the reverse motor 8 is equipped with a reverse blade 10, and the direction of the reverse blade 10 is facing the lower outer roller ring 3.

[0089] The control mechanism includes an IMU, a controller, a control circuit board 17, a battery 6 and a camera 5, wherein the IMU and the controller 15 are placed at the top center of the lower inner ring frame 4, the control circuit board 17 is arranged in the upper inner ring frame 14 and is close to the rolling motor 16; the battery 6 is installed in the center of the lower inner ring frame 4, and the camera 5 is arranged at the end of the battery 6.

[0090] like Figure 4-9 The control method of the rotor flywheel of the amphibious robot platform shown in the figure includes the following contents:

[0091] Step 1: Establishing motion mode and coordinate system

[0092] Establish a world coordinate system. The world coordinate system is divided into coordinate system Body_1 and coordinate system Body_2. Coordinate system Body_1 and coordinate system Body_2 correspond to the aerial flight mode and ground motion mode respectively. The aerial flight mode and ground motion mode are switched to each other through the switching mode.

[0093] Among them, the three coordinate directions in the earth coordinate system are e x, e y, e z, three-coordinate directions in the Body_1 coordinate system Three coordinate directions in Body_2 coordinate system

[0094] Step 2, control allocation;

[0095] In flight mode, the forward, backward, left, and right motion of the rotor flywheel depends on the thrust generated by the rotor. In ground mode, its forward and backward rolling motion depends on the rolling motor located in the center. The control distribution equation is as follows:

[0096]

[0097] set then

[0098]

[0099]

[0100] Such an allocation matrix will not have multiple solutions of pseudo-inverse.

[0101] in, O b1 The angle between the x-axis and the support arm where the rotor is located, unit: deg; d: the distance between the center of the coordinate system O and the projection of the rotor on the xoy plane, unit: m; f i :The i-th motor edge The thrust generated by the shaft, unit: N; f: total thrust of the body, satisfying Unit: N; τ x ,τ y ,τ z , the total torque of the body, Decomposed in different directions, unit: N·m; c T : Speed-force proportional coefficient; c M : thrust-torque proportional coefficient; Stable rotor speed, unit: rad / s; P a : Coefficient matrix, which is the unit matrix; M4(1,1,1): Distribution matrix, each entry is 1 or -1.

[0102] Step 3: Dynamic Modeling: The driving force for the flywheel's rotation comes from an eccentric simple pendulum model. Due to the structural design of the inner ring, the center of gravity is not centered. A motor can be used to rotate the inner ring to create an angle of deflection from the vertical. Gravity creates a gravitational torque that drives the entire flywheel. Controlling the motor's output force maintains a constant angle of deflection, thereby producing a stable camera image.

[0103] Step 3.1, flight dynamics modeling based on the Newton-Euler method. The flight mode dynamics model is modeled by the Newton-Euler method as follows:

[0104]

[0105] The first two columns describe the relationship between the rotor flywheel's position change (acceleration integral) and the total thrust output, and the last two columns describe the relationship between the rotor flywheel's attitude change (angular velocity integral) and the torque output.

[0106] In the above formula, m is the total mass of the drone, in kg; g is the acceleration due to gravity, in m / s 2 ; J,: inertia matrix with respect to the body coordinate system, unit kg·m 2 R, the rotation matrix from the body coordinate system to the inertial coordinate system: bω: angular velocity in the Body_1 coordinate system, unit rad / s; Θ: Euler angle in the Body_1 coordinate system, unit rad; W: transformation matrix between Euler angle derivative and angular velocity in the Body_1 coordinate system; e p: the position of the center of mass in the Earth coordinate system, unit: m; e v: velocity of the center of mass in the Earth coordinate system, unit: m / s; τ: total torque generated by the rotor, unit: N·m; G a : Gyroscopic torque generated by rotor rotation, unit: N·m;

[0107] Step 3.2: The ground mode dynamics model is modeled by the Kane method:

[0108]

[0109]

[0110] When the body thrust fi and Euler angle and angular velocity are set The rolling state of the rotor flywheel can be calculated; these nonlinear second-order differential equations describe the rolling state of the rotor flywheel at θ, The dynamic behaviors in the three directions of ψ and φ provide a model for control;

[0111] Wherein, n axis: Body_2 coordinate system Direction, m-axis: Body_2 coordinate system Direction; p-axis: in the Body_2 coordinate system Direction, R: total radius of the UAV's circular shell, unit: m; A, C: moment of inertia of the body about the n, m, and p axes J = diag (AAC), unit: kg·m 2 ; ψ: rolling heading angle, unit: rad; θ: attitude pitch angle, 0° in flight mode and 90° in ground mode, unit: rad; Roll angle, which describes the rolling distance, unit: rad; T: rolling motor output torque, unit: N·m; f: ground friction, unit: N;

[0112] In order to save energy and increase endurance when the rotor flywheel is rolling, do not let the rotor motor work and only use the rolling motor, that is, f i = 0, T = 0; because the rotor relies on high-speed compressed air to generate thrust to maintain its rolling upright posture, this will generate a large amount of heat loss and battery energy consumption; while the torque of the rolling motor directly acts on the outer ring of the rotor flywheel to drive it to roll, which is energy efficient; the dynamic equation at this time is as follows:

[0113]

[0114] When the four thrusts of the body maintain the changing rules When M is a constant, the torque in the yaw direction can be stably generated to control the rolling direction.

[0115] Step 4: Establishment of the rotor flywheel control system.

[0116] After modeling the two motion modes of the rotor flywheel, consideration is given to selecting an appropriate controller to maintain the stability of the flywheel motion. The rotor flywheel's Euler angles, body angular velocity, and body acceleration state quantities can be used to observe the motion control effect. Since mode switching and rolling actions are more complex, they are selected for analysis and control.

[0117] To meet the controller feedback requirements, the rotor flywheel pitch, yaw, force, and torque are important performance indicators of system stability. The state variables and output vectors of the system are selected; the state space is shown below:

[0118]

[0119] Indicates the status of the system

[0120] U k-1 =[f τ x τ y τ z ] T , represents the control input of the system

[0121] Represents the disturbance of the system

[0122] Y k Represents the output of the system

[0123] The aerial flight mode, ground rolling attitude stabilization, and air-to-ground mode switching actions are controlled primarily by the air thrust generated by the rotors. For air-to-ground mode switching, the state variable is the pitch angle of the Body_1 coordinate system, which enables a rotation of 0 to 90°. For ground mode steering, the main state variable is the yaw angle of the Body_2 coordinate system, which enables control in the predetermined direction.

[0124] The details of the transition from flight mode to ground mode are as follows:

[0125] The motion state when switching from flight mode to ground mode is: mode switch-roll-turn.

[0126] The control goal of the “flight-ground” mode switch is to know the reference attitude angle Θ after the UAV lands. d =θ d , design the controller Make lim t→+∞ ||e Θ(t)||=0, where Θ d is the target pitch angle; the pitch angle is expected to be 0 degrees in flight mode and 90 degrees in ground mode; the dynamic model for air-to-ground mode switching is:

[0127]

[0128] The angle-angular velocity dual-loop PID controller is used to control the pitch angle of the rotor flywheel by considering the influence of the nonlinear term in the Kane equation.

[0129] Design expected angular velocity Expected torque

[0130] Finally, the desired force and torque vectors in the body_1 coordinate system are obtained, which are converted into rotor motor throttle commands through the power distribution matrix and the electronic control link for output;

[0131] The rolling steering direction control target is the known reference attitude angle Θ d =ψ d , design the controller Make lim t→+∞ ||e Θ (t)||=0, where Θ d is the target yaw angle; the pitch angle is expected to be zero when landing and 90 degrees when rolling; the dynamic model of rolling direction control is

[0132]

[0133] The heading control has no gravity effect in the dynamic model. It is used to control the stabilization of the heading angle (range -180 to 180).

[0134] Scroll speed control:

[0135] Since the forward roll action is assumed to be decoupled from the rotor, the roll motion within the body_2 frame is controlled only by the roll motor. The roll motion control strategy aims to maintain a stable roll velocity;

[0136] The inverted pendulum dynamics model shows that the outer ring speed is related to the angle between the center of gravity and the direction of gravity. The larger the angle, the greater the torque provided by gravity, and the greater the torque acting on the outer ring through the rolling motor, which can accelerate the outer ring's rolling. Therefore, a three-loop PID controller is implemented because it is more conducive to achieving the control goal of a single state.

[0137] Step 1, in the outermost outer ring speed control, the outer ring speed calculation formula is as follows:

[0138]

[0139] --The relative angular velocity of the inner and outer rings is obtained by the encoder of the rolling motor,

[0140] --The angular velocity of the outer ring in the Earth coordinate system is derived by the formula,

[0141] --The inner circle angular velocity in the Earth coordinate system is obtained by the roll angle of the IMU,

[0142] With the feedback of the outer ring speed, stable speed control can be achieved through the P controller;

[0143] In Step 2, a closed-loop control of the inner rotor position was designed using a PD controller. Using roll angle feedback from the IMU, the position of the flywheel's inner ring was stabilized. Actual testing revealed a delay of tens to hundreds of milliseconds between the ESC receiving the throttle signal and outputting a stable speed. Furthermore, the formula for calculating the desired torque in the body_2 coordinate system for rolling direction control contains trigonometric terms related to the roll angle. Rapid changes in the inner rotor roll angle would cause system oscillations, preventing the eight rotors from generating a stable combined torque to achieve rolling direction control. Furthermore, a camera is mounted on the flywheel's inner ring; stabilizing the inner ring's position improves video quality. The PD controller is used to compensate for oscillations caused by the nonlinear terms in the torque generated by gravity, ensuring early response and a degree of intelligent predictive capability.

[0144] Step 3: Use a PI controller to design a closed-loop control of the inner ring angular velocity. The rolling speed is fed back by the IMU. Since there is an error in the mechanical mean value of the flywheel inner ring, an integral term is introduced to eliminate it.

[0145] After the cascade PID, the output is the control current value of the rolling motor, which is sent to the rolling motor through the ESC to drive the motor to rotate.

[0146] The details of the transition from ground mode to flight mode are as follows:

[0147] From ground mode to flight mode: mode switching - takeoff - flight attitude control;

[0148] The control goal of the “ground-to-flight” mode switch is to flip the upright rotor flywheel to the take-off attitude. d =θ d , design the controller Make lim t→+∞ ||e Θ (t)||=0, where Θ d is the target pitch angle; in ground mode, it is 90 degrees, and in flight mode, the pitch angle is expected to be 0. The dynamic model of air-to-ground mode switching is:

[0149]

[0150] Flight altitude and attitude control

[0151] During tracking, the target point is determined by the current time scale, and the quadcopter's lateral and longitudinal movements must be controlled simultaneously to approach the target point. The ultimate result of trajectory tracking is that the quadcopter will fly close to the trajectory, and the duration of the flight will approach the reference trajectory.

[0152] The desired center of mass position p of the rotor flywheel d (t) follows the target trajectory and the desired yaw angle ψ d The desired direction to follow the target trajectory.

[0153] The translational motion of the quadrotor drone is determined by the total thrust f d The total thrust is directly controlled, which is the sum of the thrusts generated by the four motors. The direction of the total thrust is along the body coordinate axis. negative direction; therefore, in obtaining the desired trajectory p d After (t), the controller controls the total thrust and yaw direction ψ d to determine the translational motion of the quadrotor; the controller then follows this desired pose by controlling the torque τ.

[0154] In the present invention, taking into account the safety and reliability of the mobile control of the amphibious UAV, when designing the mechanical structure, it is necessary to consider the robot's own weight and the difficulty of control. A wheeled control structure is adopted, which has the characteristics of shock absorption, easy control, and light weight. At the same time, it has a strong ability to overcome obstacles on uneven ground. Therefore, a wheeled structure is selected to contact the ground; an eight-rotor control is adopted for flight, which has a simple structure and high maneuverability.

[0155] The platform of the rotor flywheel in the present invention is a carbon fiber structure. Based on the need for a compact system, a coaxial reverse eight-rotor configuration is selected for rapid movement. Eight brushless DC motors are equipped with propellers to generate thrust in the forward and reverse directions. In combination with the aircraft model battery 6, the platform can achieve long endurance. In flight mode, the four rotors in the same direction work to generate thrust in the opposite direction of gravity for takeoff (that is, the four reverse motors 8 rotate, driving the four return blades to rotate); in ground motion mode, only one of the two coaxial rotors above and below works at the same time to generate thrust in the forward and reverse directions, so that the direction of the thrust can be quickly changed to control the stability of the aircraft's attitude.

[0156] The rotor flywheel amphibious drone is composed of an inner and outer ring. The upper outer roller ring 18 and the lower outer roller ring 3 are fixedly connected by lightweight aluminum outer columns 11. The upper inner ring frame 14 and the lower inner ring frame 4 are carbon plate structures and connected by lightweight aluminum inner columns 9. The inner layer of the flywheel houses components such as the rotor motor and sensor controller, which measure its position and control. The placement is generally as follows: the IMU and controller are placed around the top center of the flywheel's lower inner ring frame 4. This layer also houses the electronic wiring. The control circuit board, including the power distribution board, the roller motor ESC, and the CAN-to-serial circuit board, is located in the middle of the upper inner ring frame 14. The camera 5 is fixed in front of the battery 6 and is placed in the center of the lower inner ring frame 4.

[0157] A disc-shaped lightweight unicycle shell 1 can also be fixed on the outer peripheral surface of the upper outer rolling ring 18 and the lower outer rolling ring 3 of the flywheel. The rough material is used to make the flywheel have a single-point contact with the ground when rolling. It is a unicycle structure that needs to maintain its own balance and not fall to the ground. If the disc shell is not fixed, the flywheel will have two-point (multi-point) contact with the ground when rolling. The multiple contact points can make it stand stably on the ground, but it still needs to control its own posture to change the rolling direction.

[0158] To achieve both aerial and ground control of the robot, the system is equipped with a flight controller using an STM32 microprocessor. All motors are controlled via PWM and the CANopen protocol (generator current control must be performed at a frequency of approximately 100 Hz or higher; otherwise, performance is poor). Sensors include an IMU, encoders, and a mono camera. These sensors provide information such as the robot's posture (updated at 400 Hz after a Kalman filter), the relative rotation angles of the interior and exterior, and a video stream. The robot can be remotely controlled via a mobile app or remote control. Finally, all robot operation data is stored in a log on an SD card.

[0159] The operation of a rotor flywheel includes flight, mode switching, and ground rolling. Due to the complex operating conditions, especially during mode switching and ground rolling, it is necessary to find a reasonable model to describe the dynamic characteristics of the rotor flywheel under different driving states.

[0160] The focus is on improving the ground performance of the flywheel rotor. Figure 4 The motion pattern of the rotor flywheel is described. Figure 5 The reference coordinate system established in different motion modes of the rotor flywheel is described. Two coordinate systems are used in flight mode and ground mode. The reason is that when the rotor flywheel switches from flight mode to ground mode, the Body_1 coordinate system will rotate around the The axis rotates 90°, which will cause the Euler angle singularity problem, so the Body_2 coordinate system is established. The axis is rotated -90° and can be used as a reference coordinate system for the rotor flywheel in ground mode to offset the effects of singularities.

[0161] Regarding the power drive issue, in flight mode, the forward, backward, left and right movement of the rotor flywheel depends on the thrust generated by the rotor; in ground mode, its forward and backward rolling depends on the rolling motor located in the center.

[0162] In dynamic modeling, the driving force for the flywheel's rolling motion comes from an eccentric simple pendulum model. Due to the structural design of the inner ring, the center of gravity is not centered. A motor can be used to rotate the inner ring to create an angle of deflection from the vertical. Gravity generates a gravitational torque that drives the entire flywheel's rotation. Controlling the motor's output force maintains a constant angle of deflection, thereby producing a stable camera image.

[0163] The rotor flywheel of this invention combines the characteristics of both wheels and rotorcraft drones, enabling both land and air amphibious movement across various media. It possesses excellent mobility and environmental adaptability, enabling both aerial flight and rolling motion on the ground. This cross-media mobility and flexibility are excellent. It can be used for inventory checks in large warehouses, capturing barcodes of items on shelves, and nimbly maneuvering between warehouse shelves. Operations in this environment require a platform with both aerial and ground mobility.

[0164] The present invention is not limited to the above-mentioned embodiments. On the basis of the technical solution disclosed herein, those skilled in the art can make some substitutions and modifications to some of the technical features therein according to the disclosed technical content without creative labor, and these substitutions and modifications are all within the protection scope of the present invention.

Claims

1. A rotor flywheel for an amphibious robot platform, characterized by: The inner ring structure comprises an inner ring structure and an outer ring structure. The inner ring structure is arranged in the outer ring structure. The inner ring structure and the outer ring structure are connected by a rolling mechanism. A plurality of landing gears are arranged at the bottom of the outer ring structure. A forward rotor mechanism is arranged at the upper part of the inner ring structure. A reverse rotor mechanism is arranged at the lower part of the inner ring structure. The forward rotor mechanism and the reverse rotor mechanism are symmetrical to each other. A control mechanism is also arranged on the inner ring structure. The outer periphery of the outer ring structure is also covered with a circle of unicycle shell. The outer ring structure includes an upper outer roller ring and a lower outer roller ring, the outer edges of which are connected by an outer column, and the outer shell of the wheel covers the outer circumference between the upper and lower outer roller rings; the landing gear is connected to the bottom of the lower outer roller ring, and there are four landing gears evenly distributed on the same circumference of the lower outer roller ring; the inner ring structure includes an upper inner ring frame and a lower inner ring frame, which are connected by an inner column, and the upper inner ring frame, the lower inner ring frame, the upper outer roller ring and the lower outer roller ring are concentrically arranged; The rolling mechanism includes a rolling motor and a concentric shaft. The rolling motor is installed in the center of the upper inner ring frame. The shaft end of the rolling motor extends out of the upper inner ring frame and is connected to the center of the upper outer rolling ring. The two ends of the concentric shaft are respectively connected to the center of the bottom of the lower inner ring frame and the center of the lower outer rolling ring. The forward rotor mechanism includes four forward motors, which are evenly distributed on the same circumference within the upper inner ring frame. The shaft end of the forward motor is equipped with forward blades, and the direction of the forward blades is facing the upper outer rolling ring; the reverse rotor mechanism includes four reverse motors, which are evenly distributed on the same circumference within the lower inner ring frame. The shaft end of the reverse motor is equipped with reverse blades, and the direction of the reverse blades is facing the lower outer rolling ring.

2. The rotor flywheel for an amphibious robot platform according to claim 1, characterized in that: The control mechanism includes an IMU, a controller, a control circuit board, a battery and a camera, wherein the IMU and the controller are placed at the top center of the lower inner ring frame, the control circuit board is set in the upper inner ring frame and is close to the rolling motor; the battery is installed in the center of the lower inner ring frame, and the camera is set at the end of the battery.

3. A method for controlling a rotor flywheel of an amphibious robot platform, characterized by: A rotor flywheel for an amphibious robot platform according to claim 1, comprising the following contents: Step 1: Establishing motion mode and coordinate system Step 2, control allocation; Step 3: Dynamic modeling; Step 4: Establishment of the rotor flywheel control system.

4. The method for controlling a rotor flywheel of an amphibious robot platform according to claim 3, characterized in that: The specific contents of step 1 are as follows: Establish a world coordinate system. The world coordinate system is divided into coordinate system Body_1 and coordinate system Body_2. Coordinate system Body_1 and coordinate system Body_2 correspond to the aerial flight mode and ground motion mode respectively. The aerial flight mode and ground motion mode are switched to each other through the switching mode. Among them, the three coordinate directions in the earth coordinate system are e x, e y, e z, three-coordinate directions in the Body_1 coordinate system Three coordinate directions in Body_2 coordinate system 5. The method for controlling a rotor flywheel of an amphibious robot platform according to claim 4, characterized in that: The specific contents of step 2 are as follows: In flight mode, the forward, backward, left, and right motion of the rotor flywheel depends on the thrust generated by the rotor. In ground mode, its forward and backward rolling motion depends on the rolling motor located in the center. The control distribution equation is as follows: in, The angle between the axis and the support arm where the rotor is located, unit: deg; d: the projection distance between the center of the coordinate system O and the rotor on the xoy plane, unit: m; f: the distance along the i-th motor The thrust generated by the shaft, unit: N; f: total thrust of the body, satisfying Unit: N; τ x ,τ y ,τ z , the total torque of the body, Decomposed in different directions, unit: N·m; c T : Speed-force proportional coefficient; c M : thrust-torque proportional coefficient; Stable rotor speed, unit: rad / s; P a : Coefficient matrix, which is the unit matrix; M4(1,1,1): Distribution matrix, each entry is 1 or -1.

6. The method for controlling a rotor flywheel of an amphibious robot platform according to claim 5, characterized in that: The specific content of step 3 is as follows: Step 3.1, flight dynamics modeling based on the Newton-Euler method. The flight mode dynamics model is modeled by the Newton-Euler method as follows: The first two columns describe the relationship between the position change of the rotor flywheel and the output of the total thrust, and the last two columns describe the relationship between the attitude change of the rotor flywheel and the output of the torque; In the above formula, m: total mass of the UAV, unit: kg; g: acceleration due to gravity, unit: m / s 2 ; J: Inertia matrix with respect to the body coordinate system, unit: kg·m 2 R, the rotation matrix from the body coordinate system to the inertial coordinate system: b ω: angular velocity in the Body_1 coordinate system, unit: rad / s; Θ: Euler angle in the Body_1 coordinate system, unit rad; W: transformation matrix between Euler angle derivative and angular velocity in the Body_1 coordinate system; e p: the position of the center of mass in the Earth coordinate system, unit: m; e v : velocity of the center of mass in the Earth coordinate system, unit: m / s; τ: total torque generated by the rotor, unit: N·m; G a : Gyroscopic torque generated by rotor rotation, unit: N·m; Step 3.2: The ground mode dynamics model is modeled by the Kane method: When the body thrust fi and Euler angle and angular velocity are set The rolling state of the rotor flywheel is calculated; these nonlinear second-order differential equations describe the rolling state of the rotor flywheel at θ, The dynamic behaviors in the three directions of ψ and φ provide a model for control; Wherein, n axis: Body_2 coordinate system Direction; m-axis: in the Body_2 coordinate system Direction; p-axis: in the Body_2 coordinate system Direction; R: total radius of the UAV's circular shell, unit: m; A, C: moment of inertia of the UAV about the n, m, and p axes J = diag (AAC), unit: kg·m 2 ; ψ: rolling heading angle, unit: rad; θ: attitude pitch angle, 0° in flight mode and 90° in ground mode, unit: rad; Roll angle, describes the distance of rolling forward, unit: rad; T: rolling motor output torque, unit: N·m; f: ground friction, unit: N; In order to save energy and increase endurance when the rotor flywheel is rolling, do not let the rotor motor work and only use the rolling motor, that is, f i = 0, T = 0; because the rotor relies on high-speed compressed air to generate thrust to maintain its rolling upright posture, this will generate a large amount of heat loss and battery energy consumption; while the torque of the rolling motor directly acts on the outer ring of the rotor flywheel to drive it to roll, which is energy efficient; the dynamic equation at this time is as follows: When the four thrusts of the body maintain the changing rules When M is a constant, a stable torque in the yaw direction is generated to control the rolling direction.

7. The method for controlling a rotor flywheel of an amphibious robot platform according to claim 6, characterized in that: The specific contents of step 4 are as follows: After modeling the two motion modes of the rotor flywheel, we considered selecting an appropriate controller to maintain the stability of the flywheel's motion. The rotor flywheel's Euler angles, body angular velocity, and body acceleration state variables can be used to observe the effect of motion control. Because mode switching and rolling motions are more complex, they are selected for analysis and control. To meet the controller feedback requirements, the rotor flywheel pitch, yaw, force, and torque are important performance indicators of system stability. The state variables and output vectors of the system are selected; the state space is shown below: Indicates the status of the system U k-1 =[fτ x τ y τ z ] T , represents the control input of the system Represents the disturbance of the system Y k Represents the output of the system The aerial flight mode, ground rolling attitude stabilization, and air-to-ground mode switching actions are controlled by the air thrust generated by the rotor. For air-to-ground mode switching, the state quantity is the pitch angle of the Body_1 coordinate system, which realizes a rotation of 0 to 90 degrees. For ground mode steering, the state quantity is the yaw angle of the Body_2 coordinate system, which realizes control of the predetermined direction.

8. The method for controlling a rotor flywheel of an amphibious robot platform according to claim 7, characterized in that: The details of step 4 from flight mode to ground mode are as follows: The motion state when switching from flight mode to ground mode is: mode switch - roll - turn; The control goal of the "flight-ground" mode switch is to know the reference attitude angle Θ after the UAV lands. d =θ d , design the controller Make lim t→+∞ ||e Θ (t)||=0, where Θ d is the target pitch angle; the pitch angle is expected to be 0 degrees in flight mode and 90 degrees in ground mode; the dynamic model for air-to-ground mode switching is: The angle-angular velocity dual-loop PID controller is used to control the pitch angle of the rotor flywheel by considering the influence of the nonlinear term in the Kane equation. Design expected angular velocity Expected torque Finally, the desired force and torque vectors in the body_1 coordinate system are obtained, which are converted into rotor motor throttle commands through the power distribution matrix and the electronic control link for output; The rolling steering direction control target is the known reference attitude angle Θ d =ψ d , design the controller Make lim t→+∞ ||e Θ (t)||=0, where Θ d is the target yaw angle; the pitch angle is expected to be zero when landing and 90 degrees when rolling; the dynamic model of rolling direction control is Scroll speed control: Since the forward roll action is assumed to be decoupled from the rotor, the roll motion within the vehicle frame is controlled solely by the roll motor. The roll motion control strategy aims to maintain a stable roll velocity. The inverted pendulum dynamics model shows that the outer ring speed is related to the angle between the center of gravity and the direction of gravity. The larger the angle, the greater the torque provided by gravity, and the greater the torque acting on the outer ring through the rolling motor, which accelerates the outer ring's rolling. Therefore, a three-loop PID controller is implemented because it is more conducive to achieving the control goal of a single state. Step 1, in the outermost outer ring speed control, the outer ring speed calculation formula is as follows: --The relative angular velocity of the inner and outer rings is obtained by the encoder of the rolling motor, --The angular velocity of the outer ring in the Earth coordinate system is derived by the formula, --The inner circle angular velocity in the Earth coordinate system is obtained by the roll angle of the IMU, With the feedback of the outer ring speed, the P controller can achieve stable speed control; Step 2: A closed-loop control system for the inner ring position was designed using a PD controller. This stabilized position was achieved through roll angle feedback from the IMU. Furthermore, a camera was mounted on the inner ring of the flywheel, and this stability improved the quality of the video. The PD controller was used to compensate for oscillations caused by the nonlinear term in the torque generated by gravity, ensuring early response and a degree of intelligent predictability. Step 3: Use a PI controller to design a closed-loop control of the inner ring angular velocity. The rolling speed is fed back by the IMU. Since there is an error in the mechanical mean value of the flywheel inner ring, an integral term is introduced to eliminate it. After the cascade PID, the output is the control current value of the rolling motor, which is sent to the rolling motor through the ESC to drive the motor to rotate.

9. The method for controlling a rotor flywheel of an amphibious robot platform according to claim 8, characterized in that: The details of step 4 from ground mode to flight mode are as follows: From ground mode to flight mode: mode switching - takeoff - flight attitude control; The control goal of the "ground-to-flight" mode switch is to flip the upright rotor flywheel to the takeoff attitude; Known reference attitude angle Θ d =θ d , design the controller Make lim t→+∞ ||e Θ (t)||=0, where Θ d is the target pitch angle; in ground mode, it is 90 degrees, and in flight mode, the pitch angle is expected to be 0. The dynamic model of air-to-ground mode switching is: Flight altitude and attitude control The desired center of mass position p of the rotor flywheel d (t) follows the target trajectory and the desired yaw angle ψ d Follow the desired direction of the target trajectory; The translational motion of the quadrotor drone is determined by the total thrust f d The total thrust is directly controlled, which is the sum of the thrusts generated by the four motors. The direction of the total thrust is along the body coordinate axis. negative direction; therefore, in obtaining the desired trajectory p d After (t), the controller controls the total thrust and yaw direction ψ d to determine the translational motion of the quadrotor; the controller then follows this desired pose by controlling the torque τ.

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