CN100491197C - Two body robot fish - Google Patents

Abstract

The invention provides a twin-body mechanical fish which comprises a fish head part of the mechanical fish; two sets of tail-waving drive mechanism are arranged on the back of the fish head part, and are connected with the fish head in row; compared with a mechanical fish propelled by a single tail fin, the twin-body biomimetic mechanical fish not only makes use of, and develops the advantages of the fish-liked propelling, but also overcomes the head shaking problem of the single-tail propelling, and ensures the navigating stability of the biomimetic mechanical fish, thereby, reducing the navigating resistance of the mechanical fish, and improving the efficiency of the tail-biomimetic propeller.

Description

Two body robot fish

(1) Technical field

The invention relates to a robot, in particular to a bionic fish robot without yaw motion.

(2) Background technology

Modern research on the swimming mechanism of fish began in the 1930s. However, it has been shown from the open literature that the research on this aspect has made rapid progress in the past fifteen years, and a large amount of research on the propulsion mechanism of the imitation fish began in the middle and late nineties. Lighthill was the first to classify and analyze the swimming methods of animals in water. According to the characteristics of fish propulsion, underwater propellers can be divided into two basic modes: one is anguilliform, such as hagfish, etc.; the other is carangiform, such as dolphins and Tuna etc. Anguilliform is characterized by the fact that the entire body (or almost the entire body) participates in large-amplitude fluctuations. Since at least one complete wavelength is provided over the entire length of the body, the lateral forces are cancelled, and the lateral movement tendency Minimized, many flexion-swimming fish can achieve the same backward movement as forward movement by changing the direction of the wave. The propulsion efficiency of the curved-extension type is mainly related to the propagation speed of the wave. The greater the wave propagation speed, the higher the propulsion efficiency. Compared with the swing-tail type, the propulsion efficiency of the wave-body type is lower, and it is mainly suitable for slits walk through. Czrangiform swimming is characterized by little movement of the front of the body, only the tail of the body and a large-aspect-ratio caudal fin are swung for thrust and maneuver control. The fastest swimming fishes in the ocean all use the tail swing style. During the movement, the tail fin swings, while the body only has small swings or fluctuations, and even maintains great rigidity. Its propulsion efficiency is mainly related to the following parameters: 1) the aspect ratio of the tail fin; 2) the sweep angle of the tail fin and the curvature of the front end; 3) the stiffness of the tail fin; 4) the shape of the tail fin; 5) the swing law of the tail fin. Tail fin swing propulsion has high efficiency and is suitable for long-term and long-distance swimming. In addition, some fish have low resistance and high efficiency through this swimming method, which is especially suitable for AUV and UUV. Propulsion and maneuver control.

N. Kat et al. from Tokai University in Japan studied the movement principle of the pectoral fins of the black fish, and preliminarily analyzed the relationship between the movement state of the pectoral fins and the swimming posture. N.Kat mainly analyzed the relationship between the hovering on the horizontal plane and the vertical plane, the steering movement and the swing of the pectoral fin of the fish from the maneuverability of the underwater motion device, and developed a test prototype, which can be controlled by a PC to achieve fish-like motion. Researchers from Japan's Toshiba Corporation have developed a wireless-controlled fish-like robot that can swim like a real fish. The fish-like robot is about 60 cm long and weighs about 6 pounds. The fish-like robot controls one of its tail fins through a desktop computer 1. The movement of the two pectoral fins. Since it is not necessary to completely and accurately replicate the driving mode of marine fishes, a test prototype was made using elastic vibrating fins. Japan's Tokyo Institute of Technology has developed a self-propelled test model of a 1.75-meter dolphin-type submersible. There are two nodes in its tail, the first node is driven by an engine, and the second node is connected by a spring. Japan's National Marine Research Institute (NMRI) has also developed fish-like robots such as UPF-2001.

In China, Beihang Institute of Robotics, Harbin Engineering University, Institute of Automation of Chinese Academy of Sciences, Harbin Institute of Technology, University of Science and Technology of China, Shenyang Institute of Automation and other units have carried out theoretical research on fish swimming mechanism and underwater robot imitation fish propulsion.

During the swimming process of the robotic fish, the yaw of the robotic fish caused by the lateral force generated by the flapping of the tail fin can affect the propulsion efficiency of the aircraft. This adverse effect is manifested in two aspects: first, the fish body without a flexible mechanism increases the angle of attack under the condition of yaw, resulting in great resistance; second, the current law of tail fin movement is based on the fish body It is calculated by the system, and does not consider the influence of fish body shaking on the movement state of the caudal fin. Triantafylloul summed up a large number of previous works and pointed out that there are three conditions for efficient caudal fin propulsion swimming, one of which is that the angle of attack of the caudal fin should be within a certain angle range. The existence of yaw will make the tail fin attack angle deviate from the set optimal range, thereby reducing the propulsion efficiency. At present, a large number of researches on robotic fish have been carried out at home and abroad. In terms of theoretical work, Wu Yaozu proposed the unsteady two-dimensional unsteady plate theory, Tong Binggang, Zhuang Lixian and Cheng Jianyu established a semi-analytical and semi-numerical three-dimensional unsteady plate theory, which gave a quantitative three-dimensional unsteady theoretical description; in terms of model tests , Cheng et al. studied the motion of finite aspect ratio wings. However, the above-mentioned work has done very little targeted research on the influence of yaw on the stability of robotic fish, and there is no relatively mature research result in this area for the time being, and it is not very good in solving the problem of yaw during swimming of robotic fish. s solution.

Previously, the applicant of the present invention had filed an invention patent application with the application number 200710072128.9 titled a multi-joint wave-propelled fish-shaped robot. It includes multi-joint tail swing drive mechanism, pectoral fin synchronous rotation mechanism, drive control circuit, counterweight, shape support and sealing parts, multi-joint tail swing drive mechanism includes drive motor, multi-stage four-bar linkage transmission mechanism and tail fin, drive motor is connected The multi-stage transmission mechanism, the multi-stage four-bar linkage transmission mechanism is connected to the caudal fin, and the pectoral fin synchronous rotation mechanism includes a supporting fixed part, a driving motor installed on the supporting and fixed part, two left and right pectoral fins and a transmission rod, the driving motor is connected to the transmission rod, and the transmission rod The two pectoral fins are connected, and the drive control circuit includes an infrared remote sensing control part and a lower computer circuit installed in the robot. The infrared remote sensing control part is connected to the lower computer circuit through a signal transmission interface. Although the robot of this structure can swim freely underwater, has the advantages of floating and diving functions, remote control, and rapid acceleration in complex water flow environments. But still can't solve the yaw problem in the robotic fish swimming.

(3) Contents of the invention

The purpose of the present invention is to provide a two-body robotic fish that can solve the problem of the bionic robotic fish heading swaying in terms of mechanical structure.

The object of the present invention is achieved as follows: it includes the fish head part of the robot fish, two sets of tail swing drive mechanisms are installed behind the fish head part, and the two sets of tail swing drive mechanisms are connected side by side with the fish head; the tail swing drive The mechanism is composed of a first-stage four-bar linkage mechanism and a tail connecting rod, and its composition includes rod I2, L-shaped connecting rod 4, rod II6, and rod III8; the two ends of rod III8 respectively pass through one end of rod I2 and L-shaped connecting rod 4 The rotating shaft I1 and the rotating shaft IV7 are hinged, and the hinge point is connected with the fish head part; the other end of the rod II6 is hinged with one end of the L-shaped connecting rod 4 through the rotating shaft II3; the turning point of the L-shaped connecting rod 4 is connected with the rod I2 through the rotating shaft III5 The other end is hinged.

The present invention can also include such structural features:

1. The tail swing driving mechanism is composed of a two-stage link mechanism joint and a tail joint; its composition includes two drive motors 11, 33, two crank remotes composed of rod 9 and rod 10, rod 32 and rod 31 Rod assembly, chute 12, two slide rods 13, 30, a primary propulsion joint composed of L-shaped rod 17, rod [29], a secondary propulsion joint composed of L-shaped rod 22, rod 24, rod 26, and rod 28 Joint, the three-stage propelling joint that is made up of L-shaped bar 20, bar 19, bar 18, bar 16, bar 15, bar 14.

2. The tail swing driving mechanism is composed of a two-stage link mechanism joint and a tail joint, and its driving motor is a double output shaft driving motor.

According to the existing fish bionics theory, the present invention designs: a dual-body robotic fish flexibly driven by a DC motor with multi-joint wave propulsion tail, and develops a dual-body bionic robotic fish without heading swing. In particular, the present invention aims at the problem that the head swing of the current single-tail propelled bionic robot fish swims, which greatly reduces the propulsion efficiency of the tail, and proposes a design scheme of a two-body bionic robot fish to solve the problem of the bow swing of the robot fish. The characteristic of the double-body robot fish is that it is propelled by two tails of the robot fish, and the fixed parts (heads) of the front end of the robot fish are fixedly connected to each other (it is also possible to use one fish head and two tails to advance, the principle is the same). The front ends (fish heads) of the two single-tail propulsion robot fish are fixedly connected to each other to make them integrated, and the rear two multi-joint robot fish tails are symmetrically swung and propelled. The principle of anti-rolling of the double-body robotic fish is to use the principle that the corresponding joints of the two multi-joint tails of the fish produce equal and opposite lateral forces to offset each other during the swing process, so that the whole robot fish is always in a state of lateral force balance, thus from The mechanical body solves the problem of head swaying in the swimming of the single-tailed bionic robotic fish. The invention of this device can provide an experimental body for studying the hydrodynamics of fish movement, swimming mechanism, and motion control methods, and provide a basic basis for manufacturing underwater transportation equipment with high efficiency, good mobility, low noise, and little environmental disturbance. The experimental platform, the double-body design idea is of great significance for improving the propulsion efficiency of the robot fish tail and improving the swimming speed of the robot fish.

The advantages of the dual-body bionic robotic fish compared with the single-tail fin robotic fish:

Generally speaking, robotic fish propelled by a single tail fin have the following problems:

1. Due to the yaw problem of the single-tail propelled robotic fish, this will inevitably increase the navigation resistance of the robotic fish and reduce the forward speed of the robotic fish.

2. The trajectory of the robotic fish propelled by a single tail fin is unstable, and it is difficult to achieve precise control of the forward path of the robotic fish.

3. The rotatability of the robot fish propelled by single tail fin in the horizontal plane is much worse than that of the real fish, especially the robot fish with fewer joints.

Compared with the robotic fish propelled by single tail fin, the bibody biomimetic robotic fish not only utilizes and exerts the advantages of fish-like propulsion, but also overcomes the yaw problem existing in the single-tail propulsion mode, ensuring the stability of biomimetic robotic fish navigation, thus The sailing resistance of the robotic fish is reduced, and the efficiency of the bionic propeller at the tail is improved. The main advantages are:

1. During the reverse swing process of the two tail fins of the bibody robot fish, the relatively large tail fin swing lateral force is offset by each other, thereby avoiding the bow movement of the robot fish, which reduces the navigation resistance of the robot fish and increases the tail fin. The effective swing, thereby improving the forward thrust and propulsion efficiency of the caudal fin.

2. The two-body bionic robot fish can realize one tail fin as the rudder, and the other tail fin swings and propels, so that the maneuverability of the robot fish in the horizontal plane is greatly improved, and it has good maneuverability.

3. Whether the multi-joint tail of the bionic dual-body robot fish is installed on a surface ship or an underwater submersible, the navigation body has good navigation stability and meets the needs of engineering applications.

In addition, the double-body robot fish with multi-joint wave propulsion also has the characteristics of step-by-step wave transmission, multi-joint drive, remote control function, can float up and down, can realize rapid acceleration in complex water flow environment, low energy loss, and high energy utilization rate , Wide range of production materials, low cost, simple production and so on.

This invention establishes a swimming pool that can swim freely underwater, has the functions of floating and diving, has no heading swing, reliable performance, small size, low price, wide range of production materials, remote control function and has the ability to operate in complex water flow. A micro underwater robot platform with rapid acceleration in the environment. It can be used as the carrier of underwater reconnaissance equipment, weapon systems, and communication systems to complete various tasks that ordinary soldiers cannot complete. It can also be developed as an ornamental robot fish or underwater robot toy, which has broad application prospects.

The significance of the present invention is to find a new propulsion mechanism for bionic fish based on the existing research results of bionic fish, focusing on solving the problem that the heading swing of a single-tailed robotic fish swimming in water greatly reduces the propulsion efficiency of the robot, and proposes Three kinds of multi-joint tail undulating propulsion design schemes for robotic fish are proposed to promote the application and research of underwater mobile robots.

The principle of double-body robotic fish eliminating the yaw generated during the swimming of the robotic fish is as follows:

Figure 1 is a schematic diagram of the force on the joints of a single-tailed robotic fish swimming in water. From the force analysis of any joint in the figure, it can be seen that the power generated by the joint swing (that is, the resistance D in the figure) can be decomposed into the X direction The forward power and the vertical decomposition force in the Z direction, because the vertical decomposition force in the Z direction generated by each joint is in the same direction, they cannot cancel each other out, thus affecting the stability of the entire structure in the Z direction, causing the robotic fish to swim During the process, the heading swing motion is continuously generated, which greatly reduces the propulsion efficiency of the robotic fish tail.

Figure 2 is a schematic diagram of the force on the joints of the two-body robotic fish swimming in water. From the force analysis of any two symmetrical joints in the figure, it can be seen that the power generated by the swing of the symmetrical joints (that is, the resistance D in the figure) It can be decomposed into the forward power in the X direction and the vertical decomposition force in the Z direction. Since the vertical decomposition forces in the Z direction generated by each joint are equal in magnitude and opposite in direction, the forces in the Z direction cancel each other out and the force is balanced. During the swimming process, except for the X-direction forward power generated by the two tails, there is no other force affecting the movement of the robotic fish, so there will be no bowing problem of the robotic fish, and the propulsion efficiency of the tail will be improved.

The working principle of the two-body robotic fish is as follows: the control system controls the rotation of the multi-joint tail drive motor and the pectoral fin motor of the robotic fish. Various swimming postures of the robot fish can be realized, such as: forward, turning, etc. Among them, the two multi-joint tails swing symmetrically to achieve fast forward swimming, as shown in Figure 8-10, when the two tails swing in the same direction, they can turn. , the rotation of the pectoral fins controls the floating and diving of the robotic fish.

(4) Description of drawings

Figure 1 is a schematic diagram of the stress on any joint of a single-tailed robotic fish swimming in water;

Figure 2 is a schematic diagram of the force on any joint when the two-body robotic fish swims in the water:

Fig. 3 is a schematic diagram of the principle of the tail swing driving mechanism of the first embodiment of the present invention;

Fig. 4 is the top view of Fig. 3;

Fig. 5 is a schematic diagram of the principle of the tail swing driving mechanism of the second embodiment of the present invention;

Figure 6 is a top view of Figure 5;

Fig. 7 is a schematic diagram of the structure of the second embodiment of the present invention;

Fig. 8 is a schematic diagram of the principle of the tail swing driving mechanism of the third embodiment of the present invention;

Figure 9 is a top view of Figure 8;

Fig. 10 is a schematic diagram of a two-body robot fishtail mechanism driven by a single motor and double joints (simplified structure).

(5) Specific implementation methods

The present invention is described in more detail below in conjunction with accompanying drawing example:

The double-body robot fish includes a fish head part of the robot fish, two sets of tail swing driving mechanisms are installed behind the fish head part, and the two sets of tail swing drive mechanisms are connected side by side with the fish head. The tail structure must be symmetrically designed, and swing symmetrically left and right when swimming forward, so as to ensure that the robotic fish swims forward at high speed, and can turn when the two tails swing in the same direction.

Two-body robot fish tail structure design can adopt the following three design schemes:

Tail structure design scheme 1:

As shown in Figure 3 and Figure 4, it is propelled by a four-bar linkage mechanism and a two-stage joint fluctuation of the tail link. Including rod 2, L-shaped connecting rod 4, rod 6, rod 8 and rotating shafts 1, 3, 5, 7, wherein, rod 2 is the driving rod, which constitutes the main body of the second joint, and L-shaped connecting rod 4 is the main body of the fishtail , bar 8 links to each other with robotic fish body. The propulsion principle is as follows: the rod 2 swings around the rotating shaft 1 under the drive of the servo motor (first-order swing), and the movement of the rod 2 drives the movement of the L-shaped rod 4 and the rod 6 around the rotating shafts 3, 5, and 7, thus driving Fish tail (L-shaped rod 4) swings left and right (secondary swing), and the left and right swings of two joints have produced mechanical fish forward power. This kind of structure is the simplest, and the designed robot fish can imitate the movement of fish with slow swimming speed and few joints, which is suitable for making toy or ornamental robot fish.

Tail structure design scheme 2:

The structural design of the fish tail of the two-body robot adopts three-stage joint wave propulsion. Referring to Fig. 5 and Fig. 6, it has two-stage link mechanism joints and tail joints. It includes two drive motors 11,33, two crank remote rod assemblies (rods 9,10,31,32), chute 12, two slide rods 13,30, one-stage propulsion joints (L-shaped rod 17, rod [29), two-stage propulsion joint (L-shaped bar [22, bar 24, 26, 28), three-stage propulsion joint (L-shaped bar [20, bar 19, 18, 16, 15, 14), three of which are L Shaped rods 17, 22 and 20 are the main bodies of three joints advancing. The working principle is as follows: Take the clockwise swing of the whole fish tail as an example, the motor 33 rotates clockwise, and the slide bar 30 is pushed to slide leftward in the chute 12 through the crank remote lever mechanism (rod 32, 31), and the slide bar 30 slides leftward What drives on the one hand is that the first-order joint (L-shaped bar [17, bar 29) swings clockwise around the axis 25, on the other hand it also drives the second-order joint (L-shaped bar 22, bar 24,26,28) Swing clockwise around the shaft 23, that is to say, the motor 33 controls the movement of the first-stage joint and the second-stage joint. Meanwhile, motor 11 outputs power, rotates clockwise, pushes slide bar 13 to slide rightward in chute 12 by crank remote lever mechanism (rod 9,10), promotes by bar 14,15,16,17,18, The two-stage parallel four-bar linkage mechanism composed of 19, 20, and 22 moves to the right, which will push the L-shaped rod 20 to swing clockwise around the axis 21, and realize the undulating propulsion of the third-stage joint (tail), that is, the motor 11 controls It is the left and right swing of the fishtail joint 20. The movement process of the whole mechanism is opposite to realize the counterclockwise swing of the fish tail, and the two motors cooperate with each other to rotate back and forth to realize the flexible swing of the three joints of the tail, thereby realizing the undulating propulsion of the fish tail. 7 is a schematic diagram of a two-body robotic fish mechanism adopting a three-stage joint wave propulsion structure, wherein 34 is a pectoral fin for controlling the floating and diving of the robotic fish, and 35 is a motor for controlling the movement of the pectoral fin. Its front-end assembly is described as follows: pectoral fins 34 are connected to respective drive motors 35 through respective transmission rods 61, and drive motors 35 are fixedly connected to bodies 54 and 60 respectively. stability. The two bodies 54 and 60 of the robotic fish must be fixedly connected to each other through rods 57 (three rods are connected in series in the figure, the purpose is to facilitate disassembly and assembly), so that the lateral force generated by the swinging of the two tails of the robotic fish can pass through the bodies 54 and 60. And bar 57 cancel each other (equal in magnitude, opposite in direction). Two multi-joint propulsion robotic fish tails 55 and 58 are respectively connected to the bodies 54 and 60 through shafts 56 and 59, and the respective drive motors of the robotic fish are also fixed on the respective bodies, so that when the robotic fish drive motor 62 rotates, it will drive Respective robot fish tails 55 and 60 integrally symmetrically swing around respective axes 56 and 59, which will propel the robot fish forward. To put it simply, the assembly method of the two-body robotic fish is to connect the heads of two single-tail propelled robotic fish into one body, so that the lateral force can be transmitted together and offset each other when the robotic fish swims. It is worth noting The tails of the two robotic fishes must be swung symmetrically as a whole to propel them.

Tail structure design scheme 3

The robot fish tail with this structural design is also propelled by three-stage joint fluctuations. Referring to Figures 8 and 9, the three-stage joints are driven by a motor. The principle is that the three-joint linkage mechanism is connected in series, and the difference between the connecting rods generated by the previous joint and the subsequent joint is used to drive the rotation of the latter joint, that is to say, the relative rotation angle of the latter joint is determined by the rotation of the adjacent two joints. The difference between the two connecting rods (i.e. the difference between the longitudinal length of the L-shaped rod 39 and the length of the rod 48, the difference between the length of the rod 48 and the length of the rod 53) is determined by the size of the difference, so that relative rotation occurs between the joints, and the tail is realized. Overall swing. The specific working principle is as follows: the motor 33 drives the slide bar 36 to move left and right in the chute 12 through the connecting rods 50, 51, and the left and right movement of the slide bar 36 pulls the movement of the back connecting rods 37, 49, 52, wherein the connecting rod 49 pulls the L The connecting rod 39 swings left and right around the shaft 38 to realize the left and right movement of the first-stage joint; and the connecting rod 52 promotes the movement of the four-bar linkage mechanism composed of the L-shaped rod 41, the rods 47, 48 and the L-shaped rod 39, and finally realizes the second joint. Level joint (L-shaped bar 41 transverse) moves around axis 40, same principle, bar 37 promotes the first joint four-bar linkage mechanism that is made up of L-shaped bar 41, bar 46,53, L-shaped bar 39 and is formed by L-shaped bar 41. The second four-bar linkage mechanism composed of bars 44, 45 and L-shaped bar 43 moves, and finally realizes the third-stage joint (L-shaped bar 43 transverse direction) to move left and right around the axis 42. Because L-shaped bar 39 vertically and bar 48, bar 48 and bar 53 produce difference successively when rotating around the axis [38], cause the first section L-shaped bar 39 horizontal direction and the second section L-shaped bar 41 when the three-section linkage mechanism rotates. Horizontally, and the second section L-shaped bar 41 and the third section L-shaped bar 43 have a rotation difference angle in the horizontal direction, so that relative differential motion will be generated between the sections, and the size of the difference angle is determined by the L-shaped bar 39 longitudinal direction. Length, the length difference decision of bar 48 and bar 53, just can realize robotic fish wave propelling state like this. Fig. 10 is a schematic diagram of a two-body robot fishtail mechanism driven by a single motor and double joints (simplified structure).

The dual-body robotic fish is not limited to the above three structures, such as the flexible tail drive made of memory alloy, the tail structure driven by each motor and each segment, etc. The purpose of designing the dual-body robotic fish is to solve the problem from the mechanical structure. The problem of head swaying when the robot fish swims in water.

The control system plays the role of controlling the rotation of the motor of the robotic fish and the remote control of the robotic fish. The control method can adopt the method of timely detection by the upper and lower computers of the single-chip microcomputer. The upper computer provides infrared remote sensing control for the robotic fish, and is mainly responsible for receiving external signals and sending instructions after receiving signals. It is connected with the lower computer through a signal transmission interface. The lower computer is responsible for the control of all motors, adjusting the swing angle, time and speed of each motor, so that the swimming mode of the robotic fish can be controlled. The drive control system can be a typical minimum system of a single-chip microcomputer, and other interface functions can also be expanded on this basis. The motor is controlled by the PWM signal output by the chip.

In addition, counterweight, shape support and sealing coat are necessary auxiliary parts for the production of robotic fish, and they are also necessary for the robotic fish to swim freely underwater. The counterweight adopts the method of heavy metal multi-point distribution of counterweight. In some specific applications of the robotic fish, the counterweight of the robotic fish can be adjusted with equipment. The shape support part is made of light and easy-to-process materials. The purpose is to ensure the overall imitation pituitary and the streamlined shape of the robotic fish, and meet the needs of the robotic fish's shape and fast swimming in the water. The sealing part adopts the method of overall sealing with soft rubber sleeve, and the pectoral fin seal belongs to the dynamic seal, which is the difficulty of sealing the whole robot fish. It can be realized by the way of rubber tube sleeve round tube, and the elastic friction between the rubber tube and the round tube. seal. The energy of the robotic fish is powered by rechargeable Ni-MH batteries, and there is a charging interface and a sealing interface for program debugging at the bottom of the belly of the robotic fish.

Claims (1)

1. A two-body robotic fish, which includes the fish head part of the robot fish. Two sets of tail swing driving mechanisms are installed behind the fish head part, and the two sets of tail swing driving mechanisms are connected to the fish head side by side; it is characterized in that: The tail swing driving mechanism is composed of a four-bar linkage mechanism and a tail link, and its composition includes a rod I (2), an L-shaped connecting rod (4), a rod II (6), and a rod III (8); a rod III ( 8) The two ends are respectively hinged with the rod I (2) and one end of the L-shaped connecting rod (4) through the rotating shaft I (1) and the rotating shaft IV (7), and the hinge point is connected with the fish head part; the rod II ( 6) The other end is hinged by one end of the rotating shaft II (3) and the L-shaped connecting rod (4); the turning point of the L-shaped connecting rod (4) is hinged by the other end of the rotating shaft III (5) and the rod I (2).

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