A bionic underwater robot and its intermittent swimming control method

Abstract

The present invention provides a bionic underwater robot and an intermittent swimming control method thereof, belonging to the technical field of bionic underwater robots, including underwater bionic tuna structure design, underwater bionic tuna circuit design, and CPG-based intermittent swimming motion mode of a robot fish. The bionic underwater robot is realized by imitating the yellowfin tuna in nature, and has key features such as the streamlined shape of the yellowfin tuna. The CPG-based intermittent swimming control method of the robot fish can naturally switch between the gliding mode and the swimming mode by imitating the intermittent swimming behavior of real fish in nature. The present invention has both good maneuverability and motion stability, strong environmental adaptability, and can achieve smooth movement in a complex seabed environment. At the same time, the present invention has an information acquisition module and a detection module that can be applied to underwater environmental monitoring and underwater exploration.

Description

Technical Field

[0001] The invention belongs to the technical field of bionic robots, and in particular relates to a bionic underwater robot and an intermittent swimming control method thereof. Background Art

[0002] In recent years, underwater vehicles have been widely used in the fields of oceanographic research, marine development, underwater environmental protection, etc. The traditional propeller drive method will generate a lot of noise in the wake of the vehicle, causing damage to some underwater ecosystems, and this drive method is inefficient and has poor maneuverability. However, fish have evolved over a long period of time and have a variety of efficient and highly maneuverable propulsion methods. Simulating the propulsion method of fish and developing bionic underwater propulsion devices has become the work direction of more and more researchers.

[0003] In nature, tuna are known for their strong bodies and high-speed swimming ability. They have a streamlined body shape suitable for fast swimming, making them a good model to imitate. Due to the highly active nature of tuna, they adopt a special breathing method called "impact breathing" that allows them to effectively obtain oxygen when swimming at high speeds to meet their high metabolic needs. This swimming method requires tuna to swim continuously to breathe, and impingement breathing is less efficient at low speeds, so tuna need to maintain a certain swimming speed. In order to save energy and maintain a suitable swimming speed, tuna adopts a movement method called intermittent swimming. By combining high-frequency swinging and gliding, energy can be saved to the maximum extent while maintaining the swimming speed.

[0004] However, most existing robot fish move by continuously swinging their tail fins, which significantly increases their swimming efficiency compared to intermittent swimming. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a bionic underwater robot and an intermittent swimming control method thereof. By imitating the intermittent swimming movement of tuna, an intermittent factor is introduced into the CPG (central pattern generator) model, so that the robot can efficiently switch between swimming and gliding modes to achieve efficient swimming.

[0006] In nature, the swimming behavior of real fish is different from that of most existing bionic robot fish. Most of the existing bionic robot fish swim in a way that continuously swings the tail fin for propulsion, but real fish do not swing their tail fins continuously when swimming. Instead, they exhibit intermittent swimming behavior, and intermittently adjust their movements to improve swimming efficiency according to different external environmental conditions. Intermittent swimming behavior includes a two-phase sequence: an explosive phase in which the fish generates propulsion, followed by a gliding phase. During gliding, the fish will not actively exert muscle force. For real fish, moving only by inertia during the gliding phase can effectively save energy and improve swimming efficiency. Therefore, the present invention constructs an intermittent swimming control method by imitating the intermittent swimming behavior of fish. This control method only uses one parameter, the intermittent factor, to achieve the switching of the swimming mode of the robot fish, and can more conveniently control the swimming and gliding modes of the robot fish, simulate the two swimming modes of fish in nature, generate a stable periodic phase-locked signal, and control the tail fin of the robot fish to swing.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] A bionic underwater robot adopts the structure of a tuna, including a fish body, a dorsal fin, a pair of pectoral fins and a caudal fin; the dorsal fin is fixed to the upper part of the fish body, the pair of pectoral fins are symmetrically arranged on the left and right sides of the fish body, and the caudal fin is sequentially connected to the rear of the fish body.

[0009] Preferably, the fish body includes a head compartment, a tail compartment No. 1, a tail compartment No. 2, and a tail compartment No. 3; the head compartment is sequentially connected to the tail compartment No. 1, the tail compartment No. 2, the tail compartment No. 3, and the tail fin.

[0010] Preferably, the dorsal fin has an internal integrated antenna to achieve wireless communication with a host computer.

[0011] Preferably, the pectoral fin drive mechanism in the head cabin changes the angle of attack of the left and right pectoral fins through a servo; the servo transmits the output torque to the pectoral fin drive shaft through two bevel gears; the bionic tuna pectoral fins are fixed on the left and right sides of the drive shaft; the pectoral fin flange is connected to the head cabin, and a waterproof sealing ring is used in the middle to achieve a waterproof function.

[0012] Preferably, it includes a multi-joint series tail drive device, which is driven by a plurality of tail fin drive servos in series, so as to simulate the fish body wave pattern of fish in reality; tail fin drive servo No. 1, tail fin drive servo No. 2, and tail fin drive servo No. 3 are high-power waterproof servos; the high-power waterproof servos are interconnected by an aluminum alloy tail fin fixing frame to realize the transmission of the servo torque; the outside of the tail fin drive servo No. 1, tail fin drive servo No. 2, and tail fin drive servo No. 3 is covered with a bionic shell to imitate the streamlined shape of the tuna; the front end of the tail fin fixing frame is connected to the head cabin.

[0013] Preferably, the shell of the bionic tuna is made by 3D printing, and its material is nylon.

[0014] Preferably, the pectoral fin is driven by a steering gear, which is connected to the drive shaft via a bevel gear, and changing the angle of the steering gear can change the angle of attack of the bionic tuna pectoral fin.

[0015] Preferably, the tail fin is driven by multiple waterproof servos connected in series, and the servos are connected by an aluminum alloy tail fin fixing frame, and the signal line of each servo is connected to the control cabin of the bionic tuna through an air plug. At the same time, an antenna is also arranged inside the dorsal fin, and the wireless communication module is connected to the antenna to realize wireless communication of the underwater robot.

[0016] Preferably, the power supply module provides a stable voltage for the underwater bionic thruster, and the current measurement module can record the input current of the thruster main circuit in real time, and the input power of the thruster can be calculated by the obtained voltage and current.

[0017] The intermittent swimming motion mode of the bionic tuna is controlled by CPG. The computer host controls the underwater bionic tuna and sends intermittent CPG motion parameters.

[0018] Beneficial effects:

[0019] (1) The present invention imitates the intermittent swimming mode of fish in nature. Compared with the continuous swimming mode of other robotic fish, this swimming mode can be closer to the movement mode of real fish in nature, providing a stronger theoretical basis for the bionic behavior of robotic fish;

[0020] (2) This swimming mode can switch the swimming gait of the bionic robot fish more conveniently, directly switching between gliding and swimming modes, greatly simplifying the control process of the robot fish. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the bionic tuna;

[0022] Figure 2 It is a schematic diagram of the bionic tuna intermittent CPG;

[0023] Figure 3 This is a schematic diagram of the bionic tuna pectoral fin drive mechanism;

[0024] Figure 4 It is a schematic diagram of the bionic tuna tandem tail fin drive mechanism.

[0025] In the figure, the reference numerals are: 1.1. Dorsal fin, 1.2. Head cabin, 1.3. Pectoral fin, 1.4. Tail cabin No. 1, 1.5. Tail cabin No. 2, 1.6. Tail cabin No. 3, 1.7. Tail fin, 3.2. Pectoral fin flange, 3.3. Pectoral fin bearing, 3.4. Pectoral fin drive shaft, 3.5. Pectoral fin fixing frame, 3.6. Pectoral fin drive servo, 3.7. Pectoral fin drive bevel gear, 4.1. Tail fin fixing frame, 4.2. Tail fin drive servo No. 1, 4.3. Tail fin drive servo No. 2, 4.4. Tail fin drive servo No. 3, 4.5. Bionic fish tail. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in each embodiment of the present invention described below can be combined with each other as long as they do not conflict with each other. The mechanical structure of the robotic arm is described below in conjunction with the accompanying drawings.

[0027] like Figure 1 , Figure 2 As shown, the bionic underwater robot of the present invention adopts the structure of a tuna, can imitate the swimming mode of a tuna, and constructs a bionic tuna by imitating the key characteristics of the tuna.

[0028] The bionic underwater robot comprises a dorsal fin 1.1, a head compartment 1.2, a pectoral fin 1.3, a first tail compartment 1.4, a second tail compartment 1.5, a third tail compartment 1.6 and a tail fin 1.7. The head compartment 1.2 is sequentially connected to the first tail compartment 1.4, the second tail compartment 1.5, the third tail compartment 1.6 and the tail fin 1.7.

[0029] The head compartment 1.2 is connected to the dorsal fin 1.1 and the pectoral fin 1.3. The dorsal fin 1.1 has an internal integrated antenna, which can realize wireless communication with the host computer. The pectoral fin 1.3 is driven by the steering gear of the pectoral fin drive mechanism, and floats and dives by changing the angle of attack. The head compartment 1.2 is equipped with a main control board, preferably, its core is an STM32F407VGT6 chip, and multiple USART serial communication interfaces are arranged on the outside.

[0030] The first tail compartment 1.4, the second tail compartment 1.5 and the third tail compartment 1.6 are driven by a waterproof steering gear, and the first tail compartment 1.4, the second tail compartment 1.5 and the third tail compartment 1.6 are independently driven, and the tail compartments are sequentially connected by a tail fin fixing frame 4.1. The tail fin 1.7 is made of flexible silicone by 3D printing, and can provide thrust for the bionic underwater robot by swinging.

[0031] like Figure 3 As shown, the pectoral fin drive mechanism in the head compartment 1.2 of the bionic underwater robot can change the angle of attack of the left and right pectoral fins through a steering gear. The pectoral fin drive steering gear 3.6 transmits the output torque to the pectoral fin drive shaft 3.4 through two pectoral fin drive bevel gears 3.7. The pectoral fins 1.3 of the bionic tuna are fixed on the left and right sides of the transmission shaft. The pectoral fin flange 3.2 is connected to the head compartment 1.2, and the waterproof function is achieved through a waterproof sealing ring in the middle. The pectoral fin 1.3 is connected to the pectoral fin drive shaft 3.4 through screws, the pectoral fin flange 3.2 is fixed on the pectoral fin drive shaft 3.4, the pectoral fin fixing frame 3.5 can be fixed inside the bionic underwater robot, the pectoral fin fixing frame 3.5 is connected to the pectoral fin drive steering gear 3.6, the pectoral fin drive bevel gear 3.7 is fixed on the pectoral fin drive shaft 3.4, and meshes with the gear on the pectoral fin drive shaft 3.4, and the pectoral fin bearing 3.3 and the pectoral fin drive shaft 3.4 cooperate with each other to provide support. After the servo moves, the gear on it moves, driving the gear on the transmission shaft to move, and then driving the shaft to move, thereby driving the pectoral fins 1.3 to move.

[0032] like Figure 4 As shown, the bionic underwater robot includes a multi-joint series tail drive device, which is driven by multiple servos in series, so as to simulate the fish body wave pattern of fish in reality. The tail fin drive servo No. 1 4.2, the tail fin drive servo No. 2 4.3, and the tail fin drive servo No. 3 4.4 are high-power waterproof servos. The high-power waterproof servos are connected to each other through the aluminum alloy tail fin fixing frame 4.1 to realize the transmission of the servo torque. The tail fin drive servo No. 1 4.2, the tail fin drive servo No. 2 4.3, and the tail fin drive servo No. 3 4.4 are covered with a bionic shell on the outside to imitate the streamlined shape of the tuna. The front end of the tail fin fixing frame 4.1 is connected to the head cabin 1.2. The bionic fish tail 4.5 imitates the tail shape of the tuna, and its reciprocating swing provides thrust for the movement of the bionic tuna.

[0033] like Figure 2 As shown, the intermittent swimming control method of the present invention includes: adopting an intermittent swimming motion mode based on a central pattern generator network, introducing an intermittent factor in the central pattern generator network, and controlling the bionic underwater robot to switch between the burst mode and the gliding mode to achieve efficient swimming. Figure 2 middle, The tail fin angle of the robot fish output by intermittent CPG, i=1,2,3.

[0034] The intermittent central pattern generator model with the intermittent factor introduced is:

[0035] ;

[0036] in, , , Respectively represent The amplitude, offset angle, and phase offset of each joint. , , , F represent amplitude, offset, expected phase, and expected frequency respectively, which are all control commands. Three structural parameters , , Impact on transient dynamics of CPG models. is the output signal of the CPG model, indicating the corresponding joint Deflection angle at time t.

[0037] The present invention introduces an intermittent factor into the CPG model , is the control command to achieve more flexible control of the intermittent swimming behavior of the bionic underwater robot. , the swing of the bionic robot fish will be suppressed and it will start to glide by inertia; if , the bionic underwater robot will start swimming.

[0038] Based on this, the present invention enters the burst mode or the gliding mode by giving control commands, so that the bionic underwater robot can complete the intermittent swimming behavior more smoothly.

Claims

1. A method for controlling the intermittent swimming of a bionic underwater robot, characterized in that: The bionic underwater robot adopts the structure of a tuna, including a fish body, a dorsal fin, a pair of pectoral fins and a caudal fin; the dorsal fin is fixed to the upper part of the fish body, the pair of pectoral fins are symmetrically arranged on the left and right sides of the fish body, and the caudal fin is sequentially connected to the rear of the fish body; The intermittent swimming control method comprises: adopting an intermittent swimming motion mode based on a central pattern generator network, introducing an intermittent factor in the central pattern generator network, and controlling the bionic underwater robot to switch between a burst mode and a gliding mode to achieve efficient swimming; The central pattern generator model with the introduction of intermittent factors is as follows: ； in, , , Respectively represent The amplitude, offset angle, and phase offset of each joint; , , , F represents amplitude, offset, expected phase, and expected frequency, respectively, which are all control commands; , , Structural parameters in transient dynamics of the central pattern generator model; is the output signal of the central pattern generator model, indicating the corresponding joint The deflection angle at time t; An intermittent factor is introduced to achieve more flexible control of the intermittent swimming behavior of the bionic underwater robot.

2. The intermittent swimming control method according to claim 1, characterized in that: For control commands, if , the swing of the bionic underwater robot is suppressed, and it begins to glide by inertia and enters the gliding mode; if , the bionic underwater robot starts to swim and enters the burst mode; by giving control commands, the burst mode or the gliding mode is switched, so that the bionic underwater robot can complete intermittent swimming.

3. The intermittent swimming control method according to claim 1, characterized in that: The fish body includes a head compartment, a first tail compartment, a second tail compartment, and a third tail compartment; The head cabin is connected to the No. 1 tail cabin, No. 2 tail cabin, No. 3 tail cabin and the tail fin in sequence.

4. The intermittent swimming control method according to claim 1, characterized in that: The dorsal fin has an internal integrated antenna to achieve wireless communication with a host computer.

5. The intermittent swimming control method according to claim 1, characterized in that: The pectoral fin drive mechanism in the head cabin changes the angle of attack of the left and right pectoral fins through a servo; the servo transmits the output torque to the pectoral fin drive shaft through two bevel gears; the bionic tuna pectoral fins are fixed on the left and right sides of the drive shaft; the pectoral fin flange is connected to the head cabin, and a waterproof sealing ring is used in the middle to achieve waterproof function.

6. The intermittent swimming control method according to claim 3, characterized in that: It includes a multi-joint serial tail drive device, which is driven by multiple tail fin drive servos in series, so as to simulate the fish body wave pattern in reality; tail fin drive servo No. 1, tail fin drive servo No. 2, and tail fin drive servo No. 3 are high-power waterproof servos; the high-power waterproof servos are connected to each other through an aluminum alloy tail fin fixing frame to realize the transmission of servo torque; The exterior of the tail fin driven servo No. 1, tail fin driven servo No. 2 and tail fin driven servo No. 3 is covered with a bionic shell to imitate the streamlined shape of the tuna; the front end of the tail fin fixing frame is connected to the head cabin.

Images