Four-foot crawling gecko robot and control system thereof

Abstract

The invention provides a four-foot climbing gecko robot and a control system thereof. The four-foot climbing gecko robot comprises a trunk structure, four symmetrically-distributed leg structures and four foot suction cups. A damping turntable serves as a waist joint and is used for connecting a front trunk and a rear trunk of the trunk structure, so that the robot swings left and right; the longitudinal servo steering engines serve as shoulder joints and are used for connecting the trunk structure and the leg structures so as to control the leg structures to ascend and descend. The first transverse servo steering engine serves as an elbow joint and is used for connecting the longitudinal servo steering engine and the leg structure so as to drive the leg structure to move; the second transverse servo steering engine serves as a wrist joint and is used for connecting the leg structure and the foot suction cup so as to adjust the foot falling point position of the foot suction cup. The four-legged gecko crawling robot can flexibly move in a complex environment, and the stability of movement on a vertical plane is kept.

Description

Technical Field

[0001] The present application belongs to the field of robot control technology, and in particular relates to a four-legged crawling gecko robot and a control system thereof. Background Art

[0002] With the rapid development of robotics, exploring the efficient movement mechanisms of organisms in nature and applying them to robot design has become a hot research field. Geckos are creatures in nature known for their excellent climbing ability. Their unique attachment system and flexible movement patterns provide valuable inspiration for the design of bionic robots. However, to achieve stable movement of gecko robots in complex environments, especially in vertical planes and effective obstacle avoidance, many technical problems need to be solved. When performing climbing tasks, traditional robots are often limited by fixed attachment devices and complex control systems, making it difficult for them to show the same flexibility and adaptability as geckos in changing environments. Summary of the invention

[0003] In view of this, the purpose of the present application is to provide a four-legged crawling gecko robot and its control system, in which the trunk structure uses a driven shaft to simulate the rotational movement of the gecko's waist to enhance the flexibility of the robot's movement; each leg structure has a longitudinal servo actuator and two lateral servo actuators, which can achieve different movement gaits to adapt to the robot's movement in different environments; a CPG control model is constructed using a Hopf oscillator to provide a stable rhythmic signal for the robot's movement; and a pressure sensor is used to introduce a feedback signal to achieve gait control of the robot on complex terrain with obstacles; for the output robot foot end trajectory control signal, a curve fitting method is used to further optimize it to ensure the stability of the robot's movement in the vertical plane.

[0004] The present application provides a four-legged crawling gecko robot, comprising a trunk structure, four symmetrically distributed leg structures, four foot suction cups, and a motor drive system:

[0005] The damping turntable is used as a waist joint joint 0, which is used to connect the front trunk and the rear trunk of the trunk structure so that the robot can swing left and right;

[0006] The longitudinal servo steering gear is used as a shoulder joint joint 1, and is used to connect the trunk structure and the leg structure to control the lifting and lowering of the leg structure;

[0007] The first transverse servo actuator is used as an elbow joint joint2, and is used to connect the longitudinal servo actuator and the leg structure to drive the movement of the leg structure;

[0008] The second lateral servo steering engine serves as a wrist joint joint3, which is used to connect the leg structure and the foot suction cup to adjust the landing point position of the foot suction cup.

[0009] Furthermore, it also includes an air pump drive system:

[0010] A vacuum pump, used to remove the air in the foot suction cup, and in combination with the opening and closing state of the solenoid valve, to achieve the adsorption and detachment of the foot suction cup;

[0011] An air pressure sensor, used to monitor the adsorption state of the foot suction cup and output a high level signal indicating successful adsorption, or a low level signal indicating unsuccessful adsorption;

[0012] Wherein, the foot suction cup, vacuum pump and solenoid valve are connected using a three-way conduit.

[0013] Furthermore, the longitudinal servo steering gear is a 15kg.cm PWM steering gear, so as to be suitable for the lifting and lowering of the leg structure with a small torque;

[0014] The first and second lateral servo steering gears are 45kg.cm steering gears, so as to be suitable for the crawling movement of the robot with high torque on the vertical plane;

[0015] The rotation angle interval of the first lateral servo steering gear is set to [-45, 45], and the rotation angle interval of the second lateral servo steering gear is set to [0, 135], so that the leg structures do not collide during the rotation process.

[0016] The present application also provides a quadrupedal gecko robot control system, which is applied to the motor drive system and air pump drive system of the robot as described in the above quadrupedal gecko robot; the control system comprises:

[0017] The CPG control module is used to output a periodic initial control signal according to the input CPG initial configuration parameters;

[0018] A control processing module, used to formulate a gait switching and stride adjustment strategy for the robot, generate a foot motion trajectory based on the initial control signal, and output a feedback signal to the robot based on a monitoring signal of the foot suction cup received in real time;

[0019] A trajectory planning module is used to fit the foot motion trajectory to ensure continuous changes in speed and acceleration, and convert the fitted foot motion trajectory into a joint control signal for output;

[0020] Wherein, the leg joints include: shoulder joint joint1, elbow joint joint2 and wrist joint joint3;

[0021] The gaits of the robot include: a three-legged gait, a diagonal gait and an in-situ turning gait.

[0022] Further, when outputting the periodic initial control signal, the CPG control module is specifically used to:

[0023] A symmetrical coupling network consisting of four Hopf oscillators is used to output a reference signal for moving each leg structure of the robot;

[0024] Mapping the reference signal into initial control signals for each leg joint and foot suction cup;

[0025] The initial control signal includes: a leg lifting signal, a leg falling signal, a leg moving signal, a foot adsorption signal and a foot detachment signal.

[0026] Further, when outputting a feedback signal to the foot suction cup, the control processing module is specifically used to:

[0027] Determine the movement phase of each leg structure; the movement phase includes: a stance phase and a swing phase;

[0028] Acquire a first real-time monitoring signal of a foot suction cup connected to the leg structure in a support phase;

[0029] If the first real-time monitoring signal is a high level signal, then execute the next step;

[0030] If the first real-time monitoring signal is a low-level signal, a first feedback signal for controlling the leg structure to be lifted up and lowered again is output, and a second real-time monitoring signal for the foot suction cup is acquired again;

[0031] If the second real-time monitoring signal is a high level signal, then execute the next step;

[0032] If the second real-time monitoring signal is a low level signal, a second feedback signal for adjusting the landing point position of the foot suction cup is output, and a third real-time monitoring signal for the foot suction cup is reacquired until the foot suction cup is successfully adsorbed.

[0033] Furthermore, the trajectory planning module fits the foot motion trajectory in the following manner:

[0034] The foot motion trajectory is curve fitted using a quasi-uniform B-spline function as shown in the following formula to obtain a fitted foot motion trajectory P(u):

[0035]

[0036] Where P i As the control point, select n+1 points with equal spacing on the foot end motion trajectory, and the curve degree is k; B i,k (u) is the B-spline basis function, usually defined using the Cox-deBoor recursion formula;

[0037] Wherein, the Cox-deBoor recursive formula is:

[0038]

[0039] In the formula, u i is a non-decreasing sequence, u i The value is as follows:

[0040]

[0041] Among them, the non-decreasing sequence u i The node vector U is formed and its expression is as follows:

[0042] U={u0,u1,u2,...,u n+k ,u n+k+1 ,u n+k+2}.

[0043] The four-legged crawling gecko robot and its control system provided by the present application have the following technical effects: 1) The trunk structure uses a driven shaft to simulate the rotational movement of the gecko's waist to enhance the flexibility of the robot's movement; each leg structure has a longitudinal servo actuator and two lateral servo actuators, which can achieve different movement gaits to adapt to the robot's movement in different environments; 2) A CPG control model is constructed using a Hopf oscillator to provide a stable rhythmic signal for the robot's movement; and a pressure sensor is used to introduce a feedback signal to achieve gait control of the robot on complex terrain with obstacles; 3) The output robot foot end trajectory control signal is further optimized using a curve fitting method to ensure the stability of the robot's movement in the vertical plane. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 The overall structure diagram of the four-legged crawling gecko robot provided in the embodiment of the present application is shown;

[0045] Figure 2 A corresponding relationship diagram of the joints of the quadruped crawling gecko robot provided in an embodiment of the present application is shown;

[0046] Figure 3 The abstract structure diagram of a single-leg connecting rod of a quadruped crawling gecko robot provided in an embodiment of the present application is shown;

[0047] Figure 4 A robot arm motion space diagram analyzed by the Monte Carlo method and surrounded by four circles provided in an embodiment of the present application is shown;

[0048] Figure 5 A three-legged gait schematic diagram and a phase diagram of a four-legged crawling gecko robot provided in an embodiment of the present application are shown;

[0049] Figure 6 A pseudo-diagonal gait schematic diagram and a phase diagram of the quadrupedal crawling gecko robot provided in an embodiment of the present application are shown;

[0050] Figure 7 A schematic diagram and a phase diagram of the in-situ turning gait of the quadrupedal crawling gecko robot provided in an embodiment of the present application are shown;

[0051] Figure 8 A schematic diagram of mutual coupling of three Hopf oscillators provided in an embodiment of the present application is shown;

[0052] Fig. 9 A schematic diagram of a CPG control module of a quadruped crawling gecko robot provided in an embodiment of the present application is shown;

[0053] Fig.10 A corresponding relationship diagram of CPG joint control signals provided in an embodiment of the present application is shown;

[0054] Fig.11 A schematic diagram of a feedback action provided in an embodiment of the present application is shown;

[0055] Fig.12 A force analysis diagram of the robot when the right front and left rear legs of the quadruped crawling gecko robot provided by an embodiment of the present application are supporting legs is shown;

[0056] Fig.13 A speed and acceleration curve of the foot end motion trajectory in the plane XYZ direction directly generated by the initial control signal output by the CPG control module provided in an embodiment of the present application is shown;

[0057] Fig.14 The fitted foot end motion trajectory diagram and speed and acceleration change diagram provided in the embodiments of the present application are shown. DETAILED DESCRIPTION

[0058] In order to make the purpose, technical solution and advantages of the technical solution more clear, the technical solution is further described in detail below in conjunction with specific implementation methods. It should be understood that these descriptions are only exemplary and are not intended to limit the scope of the technical solution.

[0059] Example 1: Quadruped Crawling Gecko Robot

[0060] See also Figure 1 , Figure 1 The figure shows the overall structure of the quadrupedal crawling gecko robot provided in the embodiment of the present application. Figure 1 As shown in (a), the four-legged crawling gecko robot includes a trunk structure, four symmetrically distributed leg structures, and four foot suction cups.

[0061] The quadruped crawling gecko robot also includes a motor drive system: a damping turntable as a waist joint joint0, used to connect the front trunk and the rear trunk of the trunk structure so that the robot can swing left and right; a longitudinal servo servo as a shoulder joint joint1, used to connect the trunk structure and the leg structure to control the lifting and falling of the leg structure; a first lateral servo servo as an elbow joint joint2, used to connect the longitudinal servo servo and the leg structure to drive the movement of the leg structure; a second lateral servo as a wrist joint joint3, used to connect the leg structure and the foot suction cup to adjust the landing point position of the foot suction cup.

[0062] In this structure, in order to imitate the waist movement of a gecko, the trunk is divided into two parts, front and back, and a damping turntable is used in the middle as a driven shaft connection, so that the waist of the robot can swing left and right when it moves. The design of the waist structure enhances the robot's movement flexibility, allowing it to turn on the spot. Figure 1 As shown in (b), the four leg structures are symmetrically distributed, and each leg has three active degrees of freedom. Different from the two vertical rotation axes and one horizontal rotation axis of the conventional quadruped robot leg structure, the leg of the present application adopts a structural design of one vertical rotation axis and two horizontal rotation axes. The vertical rotation axis only controls the lifting and falling of the leg, and the horizontal rotation axis is responsible for driving the robot to move and adjust the landing point. This design makes the robot's feet shake less and helps the body's center of mass to be close to the crawling surface to reduce the overturning moment. Figure 1 (c) is the foot suction cup of the gecko robot. This application uses a self-designed pneumatic flexible bionic octopus suction cup. This suction cup has the characteristics of small size and strong adsorption force. It can achieve stable adsorption while bearing the weight of the gecko robot. Figure 2 The corresponding relationship diagram of the leg joints of the four-legged crawling gecko robot provided in the embodiment of the present application.

[0063] Among them, the longitudinal servo servo is a 15kg.cm PWM servo, which is suitable for lifting and lowering the leg structure with small torque; the first and second lateral servo servos are 45kg.cm servos, which are suitable for the crawling movement of the robot with large torque on the vertical plane.

[0064] In this structure, because the shoulder joint joint1 only needs to bear the lifting and lowering of a single leg, the torque change is small, so a 15kg.cm PWM servo is used. When crawling on a vertical plane, the elbow joint joint2 and wrist joint joint3 need to bear up to half of the robot's overall gravity, so a 45kg.cm servo with a larger torque is selected.

[0065] As an example, the motor parameters are shown in Table 1 below:

[0066] Table 1. Motor parameters

[0067]

[0068]

[0069] The rotation angle interval of the first lateral servo steering gear is set to [-45, 45], and the rotation angle interval of the second lateral servo steering gear is set to [0, 135], so that the leg structures do not collide during the rotation process.

[0070] In this structure, since the four legs of the robot of this application have the same structure, here, taking the right front leg as an example, when ignoring the shoulder joint of the leg, the leg can be abstracted as a planar two-degree-of-freedom connecting rod, please refer to Figure 3 The abstract structure diagram of the single-leg connecting rod of the quadruped crawling gecko robot shown in the figure establishes a rectangular coordinate system with the center point of the rotating shaft 1 as the origin. The coordinates of the leg landing position are:

[0071]

[0072] In the formula, (x t ,y t ) are the coordinates of the landing point, L1 and L2 are the lengths of connecting rods 1 and 2 respectively, and θ1 and θ2 are the rotation angles of connecting rods 1 and 2.

[0073] To ensure that the robot leg does not collide when rotating, we set θ1∈[-45,45], θ2∈[0,135]. The Monte Carlo method is used to analyze the robot arm motion space. The results are as follows: Figure 4 (a). It is easy to see that the motion space of the two-degree-of-freedom link robot arm is Figure 4 The closed space formed by the four circles shown in (b) is enclosed, and the following formula 2 is the equation of the four circles involved:

[0074]

[0075] In the formula, θ 1min ,θ 1max is the minimum and maximum value of θ1, θ 2min ,θ 2max are the minimum and maximum values ​​of θ2.

[0076] The four-legged crawling gecko robot also includes an air pump drive system: a vacuum pump, used to remove the air in the foot suction cup, and combined with the opening and closing state of the solenoid valve, to achieve the adsorption and detachment of the foot suction cup; an air pressure sensor, used to monitor the adsorption state of the foot suction cup, and output a high-level signal representing successful adsorption, or a low-level signal representing unsuccessful adsorption; wherein the foot suction cup, vacuum pump and solenoid valve are connected using a three-way conduit.

[0077] In this structure, the four foot suction cups are driven by a small air pump, and a three-way catheter is used to connect the foot suction cups, vacuum pump and solenoid valve. The vacuum pump is used to expel the air from the foot suction cups to achieve adsorption, and the foot suction cups are quickly adsorbed and detached by switching the open and closed states of the solenoid valves. An air pressure sensor is used to monitor the adsorption state of the foot suction cups to achieve closed-loop control.

[0078] As an example, the vacuum pump parameters are shown in Table 2 below:

[0079] Table 2. Vacuum pump parameters

[0080] parameter Parameter Value weight 100g size 32*32*65mm Operating voltage 5-12V Working current ＜0.45A Maximum vacuum -450mmHg Control method Electronic Control

[0081] Embodiment 2: Control system of a quadrupedal crawling gecko robot

[0082] First, the motion state of the quadruped crawling gecko robot is introduced:

[0083] During the movement of the quadruped gecko robot, its single leg structure is divided into two movement stages according to the different movement states:

[0084] 1) Support phase: To ensure that the robot's leg structure is stably supported on the climbing surface, the vacuum pump is activated to extract the air inside the foot suction cup, while the solenoid valve is closed to prevent external air from entering, thereby forming and maintaining a vacuum state inside the foot suction cup. This state allows the foot suction cup to be firmly attached to the climbing surface, achieving relative stillness between the leg structure and the climbing surface, and providing a stable support foundation for the robot.

[0085] 2) Swinging phase: During this phase, the vacuum pump stops working and the solenoid valve opens, allowing external air to enter the foot suction cup, so that the air pressure inside and outside the foot suction cup reaches equilibrium. This change causes the suction force between the foot suction cup and the climbing surface to weaken and eventually detach, allowing the robot leg structure to swing freely, preparing for the next move or posture adjustment.

[0086] Focusing on the alternating switching between the support phase and the swing phase of the leg structure, this application designs three gaits of a quadruped crawling gecko robot that can be used for movement under different environmental conditions: a three-legged gait, a pseudo-diagonal gait, and an in-situ turning gait. Specifically:

[0087] 1) Three-legged gait: Figure 5Shown is a three-legged gait schematic diagram and phase diagram of the four-legged crawling gecko robot provided by the present application, in which the waist joint joint0 of the robot remains fixed. In the first stage, the robot swings the leg structures in turn to change the foothold position to achieve forward movement of the leg structures. During this process, except for the currently moving leg structure, the foot suction cups connected to the other three leg structures remain in an adsorbed state to ensure the overall stability of the robot. In the second stage, after the four leg structures have reached the predetermined moving position, the foot suction cups connected to the four leg structures remain in an adsorbed state; the robot realizes the forward movement of the main body by swinging the four leg structures synchronously and equally. During this process, it is necessary to ensure that the swinging movements of the two leg structures on the left and the two leg structures on the right remain symmetrical in amplitude and timing.

[0088] 2) Pseudo-diagonal gait: Figure 6 The pseudo-diagonal gait schematic diagram and phase diagram of the four-legged crawling gecko robot provided by the embodiment of the present application are shown. The pseudo-diagonal gait, as a simplified form of the three-legged gait, shows a unique gait pattern during the movement of the robot. In this gait, the four leg structures of the robot are swung in a synchronous but grouped manner, wherein the two leg structures on the diagonal (i.e., the right front leg and the left hind leg, or the left front leg and the right hind leg) are in the same motion phase. Specifically, when the right front leg and the left hind leg maintain stable contact with the contact surface (i.e., adsorption state) and swing, and the robot body is moved forward, the left front leg and the right hind leg are in a falling-off state, and are switched to a new foothold by swinging. Subsequently, the roles of the two groups of leg structures are switched alternately, the left front leg and the right hind leg are switched to the supporting state, and the right front leg and the left hind leg enter the falling-off stage, and this cycle repeats. This alternating switching reduces the three actions of the three-legged gait to one, speeding up the movement speed of the robot.

[0089] 3) Turning in place gait: Figure 7 The figure shows the schematic diagram and phase diagram of the in-situ turning gait of the four-legged crawling gecko robot provided by the embodiment of the present application. The in-situ turning gait can be regarded as the robot being divided into two parts, the front and rear parts, which rotate around the central driven axis. When the robot turns left, the right front leg and the left hind leg are active swinging legs, which drive the main part of the robot to rotate by swinging back in the turning direction, while the left front leg and the right hind leg act as supporting legs and do not swing. When the robot turns right, the states of the swinging leg and the supporting leg are switched, the left front leg and the right hind leg act as active swinging legs, and the right front leg and the left hind leg become supporting legs. In addition, it is easy to see from the robot's rotation process that the swing amplitude of the robot's elbow joint joint2 directly reflects its turning angle. This relationship simplifies the complexity of steering control.

[0090] like Figure 7As shown in the figure, in the in-situ turning gait, the position of the robot after rotation is constrained by the swing distance of each leg. Therefore, it is necessary to calculate the relationship between the joint swing angle and the landing point of the robot after rotation. Specifically:

[0091] A rectangular coordinate system is established with the center point of the robot as the origin. R1 is the radius of the robot's circumscribed circle, H1 is the distance between the robot's front and rear legs, H2 is the width of the robot's main body, L1 is the length of the robot's elbow link, R2 is the distance from the robot's wrist joint joint3 to the center point of the foot suction cup, θ R is the turning angle of the robot, θ i is the initial angle of the robot's elbow joint 2 before turning, θ t is the angle of the elbow joint 2 after it swings when the robot turns. During the rotation process, there is θ t =θ i -θ R , the relationship between the rotation foot landing point (x, y) and the robot rotation angle is:

[0092]

[0093] The present application realizes the change of the motion state of a single leg structure and the switching of the robot's gait through a four-legged crawling gecko robot control system.

[0094] Next, the structure and function of the control system of the quadruped crawling gecko robot are introduced:

[0095] The control system of the quadruped crawling gecko robot includes:

[0096] A CPG control module is used to output a periodic initial control signal according to the input CPG initial configuration parameters; a control processing module is used to formulate a gait switching and stride adjustment strategy for the robot, and generate a foot motion trajectory based on the initial control signal, and output a feedback signal to the robot based on a real-time monitoring signal of the foot suction cup; a trajectory planning module is used to fit the foot motion trajectory to ensure continuous changes in speed and acceleration, and convert the fitted foot motion trajectory into a joint control signal for output; wherein the leg joints include: shoulder joint joint1, elbow joint joint2 and wrist joint joint3; the gaits of the robot include: tripod gait, diagonal gait and in-situ turning gait.

[0097] Further, when outputting the periodic initial control signal, the CPG control module is specifically used to:

[0098] A symmetrical coupling network consisting of four Hopf oscillators is used to output a reference signal for moving each leg structure of the robot;

[0099] Mapping the reference signal into initial control signals for each leg joint and foot suction cup;

[0100] The initial control signal includes: a leg lifting signal, a leg falling signal, a leg moving signal, a foot adsorption signal and a foot detachment signal.

[0101] Specifically, compared with other types of oscillators, the Hopf oscillator is favored for its simplicity, reliability and adaptability. By adjusting its key parameters, such as following speed, limit cycle radius and system natural frequency, the gait characteristics of the robot can be easily changed to adapt to different motion requirements and environmental changes. Therefore, the central pattern generator based on the Hopf oscillator not only provides the robot with stable gait control, but also gives the robot the ability to flexibly adapt to various complex environments.

[0102] Next, the idea of ​​using the Hopf oscillator to build a CPG control module is introduced:

[0103] The Hopf oscillator is a nonlinear oscillator. The Hopf oscillator coupling model is described by the ordinary differential equation shown in the following equation (4):

[0104]

[0105] In the formula, x i ,y i is the state variable of the i-th oscillator and also the output signal of the oscillator; is the first-order differential of x, y with respect to time; α is the convergence weight, which controls the convergence speed of the oscillator; μ is the amplitude coefficient, which is used to control the amplitude of the oscillator; w represents the natural frequency of the oscillator; p xn and p yn is the coupling term of the oscillators, which means that there are n oscillators coupled to each other; is the phase difference between oscillator i and oscillator j.

[0106] Here, if Figure 8 The figure shows a schematic diagram of the mutual coupling of three Hopf oscillators provided in the embodiment of the present application. The output state variables of the three oscillators are {x1 y1}, {x2 y2}, {x3 y3}, respectively, where p n (q i )=[p xn (i) p yn (i)] T Represents the coupling term between oscillator n and oscillator i; the three oscillators influence each other through the coupling term, causing each other's state quantities to have a fixed phase difference.

[0107] Each leg of the quadruped crawling gecko robot of the present application has three active degrees of freedom. Therefore, a symmetrical coupling network composed of four Hopf oscillators is used to output a reference signal for the movement of each leg. The reference signal is then mapped into preliminary control signals for the three joints of the leg and the foot air pump, and finally the following is obtained: Fig. 9 The diagram shown is a schematic diagram of a CPG control module of a quadrupedal gecko robot provided in an embodiment of the present application.

[0108] It was found through actual testing that when the swinging leg falls and switches to the supporting leg, if the leg suction cup directly falls to a state parallel to the climbing surface, a complete seal may not be formed between the suction cup and the climbing surface. By over-pressing, the air between the suction cup and the climbing surface can be removed to form an initial sealing state. This initial seal is the prerequisite for the suction cup to generate effective adsorption force. At the same time, after the suction cup is adsorbed, the leg needs to return to a position parallel to the adsorption plane to ensure that the height of each supporting leg to the climbing surface is the same. In order to realize the action of over-pressing the leg and returning to the original position, the leg-lifting signal output by the CPG network is used as the trigger signal, and two superimposed sinusoidal signals are used as the actual waveform output signal. The mapping relationship between the three joint rotation angles of a single leg and the corresponding oscillator output signal of the modified oscillator model is shown in the following equation (5):

[0109]

[0110] In the formula, θ h and θ k are the rotation angles of elbow joint 2 and wrist joint 3, respectively. h , A k is the change range of the two joint angles. M is the rotation angle of shoulder joint 1, ε(t) is the unit step signal, H is the suction cup air pump enable control signal, the value 1 represents the suction cup is closed, and the value 0 represents the suction cup is deflated and falls off.

[0111] As an example, Fig.10 Shown is a CPG joint control signal correspondence diagram provided in an embodiment of the present application.

[0112] Further, when outputting a feedback signal to the foot suction cup, the control processing module is specifically used to:

[0113] Determine the movement phase of each leg structure; the movement phase includes: a stance phase and a swing phase;

[0114] Acquire a first real-time monitoring signal of a foot suction cup connected to the leg structure in a support phase;

[0115] If the first real-time monitoring signal is a high level signal, then execute the next step;

[0116] If the first real-time monitoring signal is a low-level signal, a first feedback signal for controlling the leg structure to be lifted up and lowered again is output, and a second real-time monitoring signal for the foot suction cup is acquired again;

[0117] If the second real-time monitoring signal is a high level signal, then execute the next step;

[0118] If the second real-time monitoring signal is a low level signal, a second feedback signal for adjusting the landing point position of the foot suction cup is output, and a third real-time monitoring signal for the foot suction cup is reacquired until the foot suction cup is successfully adsorbed.

[0119] Next, we will introduce the feedback mechanism for dealing with the uneven ground contact points of the four groups of crawling gecko robots:

[0120] In order to ensure the stability of the robot's motion, this application adds a feedback action to it. For details, please refer to Fig.11 The feedback action diagram provided by the embodiment of the present application is shown. Air pressure sensors are installed on the four foot suction cups of the robot to provide instant feedback for closed-loop control; when the legs switch from the swinging state to the supporting state, the air pump extracts the air inside the leg suction cups to make the suction cups adhere to the plane, such as Fig.11 As shown in (a), at this time we need to detect whether the air pressure inside the suction cup reaches the safety threshold. If the air pressure inside the supporting leg suction cup reaches the safety threshold, the air pressure sensor outputs a high-level signal. If it fails to reach the safety threshold, the air pressure sensor outputs a low-level signal. By detecting the sensor signal, the control processing layer will activate two actions to help the robot walk smoothly on the climbing surface.

[0121] If the air pressure sensor outputs a low-level signal, it means that the suction cup has not been successfully adsorbed on the plane. At this time, the suction leg will be controlled to lift up again and repeat the falling action. If the air pressure value still does not meet the standard after falling again, it can be determined that the leg landing point is uneven, resulting in the suction cup being unable to completely adhere to the ground. Fig.11 (b) At this time, the control processing layer will change the swing angle of the robot's legs by adjusting the output signal waveform, and guide the robot to reselect a suitable landing point; if the air pressure sensor outputs a high-level signal, it can be inferred that the suction cup is successfully adsorbed on the plane, and the robot will perform the next action normally.

[0122] The four-group crawling gecko robot control system of the present application can enable the robot to avoid obstacles on complex terrain by introducing a feedback mechanism.

[0123] Furthermore, the trajectory planning module fits the foot motion trajectory in the following manner:

[0124] The foot motion trajectory is curve fitted using a quasi-uniform B-spline function as shown in the following formula to obtain a fitted foot motion trajectory P(u):

[0125]

[0126] Where P i As the control point, select n+1 points with equal spacing on the foot end motion trajectory, and the curve degree is k; B i,k (u) is the B-spline basis function, usually defined using the Cox-deBoor recursion formula;

[0127] Wherein, the Cox-deBoor recursive formula is:

[0128]

[0129] In the formula, u i is a non-decreasing sequence, u i The value is as follows:

[0130]

[0131] Among them, the non-decreasing sequence u i The node vector U is formed and its expression is as follows:

[0132] U={u0,u1,u2,...,u n+k ,u n+k+1 ,u n+k+2}.

[0133] Next, the design idea of ​​the trajectory planning module is introduced:

[0134] See also Fig.12 The force analysis diagram of the robot when the right front and left rear legs of the quadruped crawling gecko robot provided by the embodiment of the present application are the supporting legs is shown in the figure. When the robot is climbing on a vertical wall, the right front and left rear legs of the robot are in the supporting state, and the left front and right rear legs are in the swinging state. The force condition of the supporting legs in the static state is as follows: Fig.12 As shown in (a), the two supporting legs are subjected to the robot gravity component F directed vertically downward along the connecting rod. N and the friction force F in the opposite direction S .

[0135] When the robot changes from static to dynamic, Fig.12 As shown in (b), the two supporting legs are stationary relative to the ground. Through the downward swing of the supporting leg joints, the center of gravity of the robot changes from stationary to moving upward. Let the instantaneous acceleration of the upward movement at this time be a, and the maximum friction force provided by the legs be F Smax ,have:

[0136]

[0137] Where m' is the weight of the robot acting on a single supporting leg, μ is the friction coefficient between the foot suction cup and the climbing surface, and N is the suction force provided by the foot suction cup when it is in a vacuum state.

[0138] It can be seen that in addition to bearing the gravity of the robot, the supporting legs also need to bear the acceleration force generated when the robot moves. Excessive acceleration will increase the adsorption burden of the foot suction cup, and even exceed the friction limit provided by the foot suction cup, causing the foot suction cup to be unstable or even fall off. Therefore, in the process of foot-end trajectory planning, the acceleration of the foot-end trajectory should be smooth to avoid sudden acceleration that affects the suction effect of the suction cup.

[0139] Therefore, in order to ensure the stability of the robot's walking, the foot trajectory design should consider:

[0140] 1) Maintaining smooth and continuous motion: During the motion process, the mechanism must be kept in a smooth and continuous motion, avoiding obvious up and down fluctuations, left and right tilts, or front and back vibrations. This stability helps prevent the robot from losing stability due to uncoordinated movements, and can also reduce errors caused by fluctuations, ensuring that the robot swings smoothly to the predetermined landing point.

[0141] 2) Smoothness of the foot end motion trajectory: During the movement process, it is necessary to ensure that the speed and acceleration of the foot end trajectory in the three directions of movement change smoothly and continuously to avoid excessive instantaneous acceleration force during the movement of the robot that affects the suction cup adsorption stability.

[0142] Fig.13 The figure shows the velocity and acceleration curves of the foot end motion trajectory directly generated by the initial control signal output by the CPG control module provided in the embodiment of the present application in the plane XYZ direction. It can be seen that the velocity and acceleration curves are not smooth, and the acceleration curve has obvious mutations.

[0143] To this end, this application uses a quasi-uniform B-spline curve to fit the foot motion trajectory. The quaternary B-spline curve has third-order derivative continuity and can meet the needs of a smooth acceleration curve without sudden changes. The foot end motion trajectory diagram and the velocity and acceleration change diagram after fitting are shown in Figure 1. Fig.14 As shown in (a), (b), and (c), it can be seen that the fitted curve can achieve a smooth transition of the velocity and acceleration curves at a specific position while ensuring that the trajectory remains basically unchanged.

[0144] The above contents are only preferred embodiments of the present invention. For ordinary technicians in this field, many changes can be made in the specific implementation methods and application scopes based on the ideas of the present technical content. As long as these changes do not deviate from the concept of the present invention, they all fall within the scope of protection of this patent.

Claims

1. A four-legged crawling gecko robot, comprising a trunk structure, four symmetrically distributed leg structures, and four foot suction cups; characterized in that: Also includes the motor drive system: The damping turntable is used as a waist joint joint 0, which is used to connect the front trunk and the rear trunk of the trunk structure so that the robot can swing left and right; The longitudinal servo steering gear is used as a shoulder joint joint1, and is used to connect the trunk structure and the leg structure to control the lifting and lowering of the leg structure; The first transverse servo actuator is used as an elbow joint joint2, and is used to connect the longitudinal servo actuator and the leg structure to drive the movement of the leg structure; The second lateral servo steering engine serves as a wrist joint joint3, which is used to connect the leg structure and the foot suction cup to adjust the landing point position of the foot suction cup.

2. The quadrupedal crawling gecko robot according to claim 1, characterized in that: Also includes air pump drive system: A vacuum pump, used to remove the air in the foot suction cup, and in combination with the opening and closing state of the solenoid valve, to achieve the adsorption and detachment of the foot suction cup; An air pressure sensor, used to monitor the adsorption state of the foot suction cup and output a high level signal indicating successful adsorption, or a low level signal indicating unsuccessful adsorption; Wherein, the foot suction cup, vacuum pump and solenoid valve are connected using a three-way conduit.

3. The quadrupedal crawling gecko robot according to claim 1, characterized in that: The longitudinal servo steering gear is a 15kg.cm PWM steering gear, which is suitable for the lifting and lowering of the leg structure with small torque; The first and second lateral servo steering gears are 45kg.cm steering gears, so as to be suitable for the crawling movement of the robot with high torque on the vertical plane; The rotation angle interval of the first lateral servo steering gear is set to [-45, 45], and the rotation angle interval of the second lateral servo steering gear is set to [0, 135], so that the leg structures do not collide during the rotation process.

4. A four-legged crawling gecko robot control system, characterized in that: A motor drive system and an air pump drive system applied to the robot as claimed in claims 1-3; the control system comprises: The CPG control module is used to output a periodic initial control signal according to the input CPG initial configuration parameters; A control processing module, used to formulate a gait switching and stride adjustment strategy of the robot, generate a foot motion trajectory based on the initial control signal, and output a feedback signal to the robot based on a monitoring signal of the foot suction cup F received in real time; A trajectory planning module is used to fit the foot motion trajectory to ensure continuous changes in speed and acceleration, and convert the fitted foot motion trajectory into a joint control signal for output; Wherein, the leg joints include: shoulder joint joint1, elbow joint joint2 and wrist joint joint3; The gaits of the robot include: a three-legged gait, a diagonal gait and an in-situ turning gait.

5. The control system according to claim 4, characterized in that: When outputting the periodic initial control signal, the CPG control module is specifically used to: A symmetrical coupling network consisting of four Hopf oscillators is used to output a reference signal for moving each leg structure of the robot; Mapping the reference signal into initial control signals for each leg joint and foot suction cup; The initial control signal includes: a leg lifting signal, a leg falling signal, a leg moving signal, a foot adsorption signal and a foot detachment signal.

6. The control system according to claim 4, characterized in that: When outputting a feedback signal to the foot suction cup, the control processing module is specifically used for: Determine the movement phase of each leg structure; the movement phase includes: a stance phase and a swing phase; Acquire a first real-time monitoring signal of a foot suction cup connected to the leg structure in a support phase; If the first real-time monitoring signal is a high level signal, then execute the next step; If the first real-time monitoring signal is a low-level signal, a first feedback signal for controlling the leg structure to be lifted up and lowered again is output, and a second real-time monitoring signal for the foot suction cup is acquired again; If the second real-time monitoring signal is a high level signal, then execute the next step; If the second real-time monitoring signal is a low level signal, a second feedback signal for adjusting the landing point position of the foot suction cup is output, and a third real-time monitoring signal for the foot suction cup is reacquired until the foot suction cup is successfully adsorbed.

7. The control system according to claim 4, characterized in that: The trajectory planning module fits the foot motion trajectory in the following manner: The foot motion trajectory is curve fitted using a quasi-uniform B-spline function as shown in the following formula to obtain a fitted foot motion trajectory P(u): Where P i As the control point, select n+1 points with equal spacing on the foot end motion trajectory, and the curve degree is k; B i,k (u) is the B-spline basis function, usually defined using the Cox-deBoor recursion formula; Wherein, the Cox-deBoor recursive formula is: In the formula, u i is a non-decreasing sequence, u i The value is as follows: Among them, the non-decreasing sequence u i The node vector U is formed, and the expression of U is as follows: U={u0,u1,u2,...,u n+k ,u n+k+1 ,u n+k+2 }.

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