Underwater operation robot remote control system and method based on relay station

Abstract

The invention discloses an underwater operation robot remote control system and method based on a relay station. The system comprises a mother ship, a relay station and a plurality of underwater robots. According to the method, firstly, an underwater robot control system model is obtained based on general kinematics and dynamics principles of an underwater robot; a dynamic event triggering mechanism is introduced to screen and transmit data, so that the energy consumption of the underwater robot during information transmission is reduced, and the operation time is prolonged. Meanwhile, a static output feedback mode is adopted to control the system, a randomly occurring saturation phenomenon and a network attack phenomenon are comprehensively considered, the asymptotic stability of the closed-loop control system is analyzed based on a Lyapunov stability theory, and sufficient conditions meeting given performance indexes are established. And finally, based on a singular value decomposition method, solving a linear matrix inequality, designing an underwater robot static output feedback controller based on the relay station, and realizing safe and effective control of an underwater robot system.

Description

Technical Field

[0001] The present invention belongs to the field of automation technology, and relates to distributed system control of underwater communication, and in particular to a remote control system and method for an underwater operating robot based on a relay station. Background Art

[0002] The research on underwater robots can provide important technical support for deep-sea topography and resource exploration, environmental monitoring, submarine search and rescue, and national security. The underwater robot based on the relay station is a distributed control system, in which the underwater robot is mainly responsible for information collection, measurement and transmission, and task execution, while the relay station, as the control center of the underwater robot, is responsible for solving the control algorithm. The mother ship is deployed to the relay station in the designated sea area and connected by wired cables. When it arrives near the designated area, one or more underwater robots are released by the relay station. The underwater robot communicates with the relay station, and the relay station receives the information collected by the underwater robot and performs calculations and processing, and returns the control instructions to the underwater robot to achieve the control target. The control method based on the relay station can control multiple underwater robots to operate at the same time, which significantly improves work efficiency. At the same time, the relay station can be used as a station for underwater robots to replenish energy, so the underwater robot can be designed to be more compact and flexible to adapt to complex seabed environments, such as deep-sea trenches and unknown areas.

[0003] The underwater environment mainly relies on acoustic communication, and the propagation speed of acoustic waves is much lower than the propagation speed of electromagnetic waves in the air. In addition, it is affected by factors such as the complex physical environment and energy consumption of the ocean. Compared with the traditional distributed system control method on land, the communication between underwater relay stations and robots tends to be intermittent rather than continuous, and it is necessary to consider communication delays and the noise and uncertainty of sensor data. In addition, in order to achieve the goal of long-term stable operation of underwater robots, in addition to reducing energy consumption, it is also necessary to consider the impact of network attacks, the saturation of signals due to various factors during transmission, and the problem of difficulty in accurately obtaining state variables.

[0004] In summary, there is an urgent need for a control scheme for underwater robots based on relay stations under the influence of network attacks and random saturation to ensure that the underwater robots can perform underwater operation tasks safely and efficiently. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention proposes a remote control system and method for an underwater working robot based on a relay station, introduces a dynamic event trigger mechanism to reduce the amount of data transmission, considers the saturation phenomenon and possible network attacks during signal transmission, and proposes a static output feedback control method to achieve effective remote control of the underwater working robot system based on a relay station.

[0006] A remote control method for an underwater working robot based on a relay station specifically comprises the following steps:

[0007] Step 1: Based on the general kinematics and dynamics principles of the underwater robot, the model is linearized and discretized to establish the following underwater operation robot control system model:

[0008]

[0009] Among them, k represents the system sampling time; x(k) represents the state vector of the underwater robot system at time k, u(k) represents the system control input vector at time k, y(k) represents the system measurement output vector at time k, z(k) represents the system control output vector at time k; ω(k) represents the interference that satisfies infinite square additive, and A, B, C, D, F, and G are all known constant matrices.

[0010] The underwater robot system relies on relay stations to solve communication range and control problems. Compared with the distributed control system composed of multiple sensors on land robots, which has real-time, continuous and high-reliability communication conditions on the ground, the communication of underwater robots is limited by the low bandwidth and high latency caused by the complex physical environment of the ocean. The following dynamic event trigger protocol is introduced to schedule the transmission signal to optimize environmental adaptability and communication quality:

[0011]

[0012] The superscript T indicates transposition, k s and k s+1 denote the time when the sth and s+1th systems meet the triggering conditions for data transmission, ψ(k)=y(k s )-y(k) represents the triggering time k s The difference between the transmitted measurement value and the system measurement value at time k, k∈[k s ,k s+1 ). 0<ε<1, are all known scalars, represents a set of positive integers, inf{·} represents the infimum, ρ(k) is a non-negative variable inside the system and satisfies:

[0013]

[0014] in, is a known scalar that satisfies

[0015] Step 2: Static Output Feedback Controller Design

[0016] Combined with the dynamic event triggering mechanism, considering the random occurrence of deception attacks and the occurrence of random saturation, the following controller is established:

[0017] u(k)=L[α(k)σ(y(k s )+β(k)r(k))+(1-α(k))(y(k s )+β(k)r(k))] (4)

[0018] Where L is the controller gain matrix to be designed. β(k) is a random variable that satisfies the probability characteristic. When β(k) = 1, the system is affected by the spoofing attack, and when β(k) = 0, the system is not affected. is a known positive scalar, Prob{·} represents the probability of an event. α(k) is a random sequence representing saturation occurrence, is a known positive scalar.

[0019] r(k) represents the deception attack suffered by the underwater robot system when transmitting data:

[0020]

[0021] in, It means that after the attacker intercepts the data packet sent by the control system at time k, the data sent to replace the original data packet satisfies H is a known matrix, and ||·|| represents the Euclidean norm.

[0022] σ(·) is the saturation function σ(p)=[σ T (p 1 ),σ T (p 2 ),…,σ T (p 6 )] T , p=[p 1 ,p 2 ,p 3 ,p 4 ,p 5 ,p 6 ] T ,satisfy i=1,2,…,6. Where sign(·) is the sign function, min{} means taking the minimum value, Indicates p i The saturation threshold of || means taking the absolute value. The saturation function σ(·) satisfies the following fan-shaped conditions:

[0023] (σ(p i )-υ i p i ) T (σ(p i )-p i )≤0 (6) where 0<υi <1 is a known scalar. The fan condition of the saturation function is extended to multiple dimensions:

[0024]

[0025] in, U = diag{υ 1 ,υ 2 ,…,υ 6},diag{υ 1 ,υ 2 ,…,υ 6} indicates that 1 ,υ 2 ,…,υ 6 is a diagonal matrix of elements. I represents the identity matrix with matching dimensions.

[0026] Combined with the controller form, the following closed-loop control system equation of the underwater robot is obtained:

[0027]

[0028] Step 3: Based on the Lyapunov stability method, establish the underwater robot closed-loop control system to be asymptotically stable and satisfy H ∞ The sufficient conditions for the performance indicators are then transformed through singular value decomposition to obtain the gain matrix L of the output feedback controller.

[0029] A remote control system for underwater working robots based on a relay station comprises a mother ship, a relay station and a plurality of underwater robots. The mother ship is deployed into a relay station in a designated sea area and is connected to the relay station through a wired cable. The relay station releases a plurality of underwater robots in a designated working sea area. The plurality of underwater robots communicate with the relay station through a wireless network and transmit sensor signals to the relay station based on a set event trigger mechanism. The relay station performs calculations on the received information, solves the controller gain, and returns control instructions to the corresponding underwater robots.

[0030] The present invention has the following beneficial effects:

[0031] 1. The relay station can control multiple underwater robots to operate at the same time, which significantly improves the operating efficiency. The algorithm calculation of the underwater robot is completed by the relay station, which prolongs the operation time of the underwater robot. The relay station can be used as a station for underwater robots to replenish energy, so the underwater robot can be designed to be more compact and flexible, and more adaptable to the complex working environment on the seabed.

[0032] 2. Considering the impact of network deception attacks on underwater robot systems, combined with the actual working environment of marine engineering, a mathematical model of saturation and attack was established, which is more engineering meaningful.

[0033] 3. The dynamic event trigger mechanism is introduced to schedule the transmission signal, which reduces the data transmission frequency and thus reduces the energy consumption of the underwater robot.

[0034] 4. Use the singular value decomposition method to decouple the nonlinear terms and obtain the controller existence conditions expressed in the form of linear matrix inequalities, which can be easily solved to obtain the controller parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Diagram of the relay-based underwater robot control system. DETAILED DESCRIPTION

[0036] The present invention will be further explained below with reference to the accompanying drawings;

[0037] like Figure 1 As shown, a remote control system for underwater working robots based on relay stations is provided. The mother ship is deployed to the relay station in the designated sea area and connected to the relay station via a wired cable. When the relay station arrives at the designated working sea area, the underwater robot is released to operate. The underwater robot and the relay station communicate via a wireless network. The relay station receives information, performs calculations, and returns control instructions to the underwater robot to achieve the control purpose.

[0038] A remote control method for underwater working robots based on relay stations is proposed for the above system. The specific steps are as follows:

[0039] Step 1: Based on the general kinematics and dynamics principles of the underwater robot and combined with the actual situation, the model is linearized and discretized to obtain a control system model of the underwater operation robot:

[0040]

[0041] in, represents the state vector of the underwater robot system at time k, and the superscript T represents the transpose of the matrix or vector. represents an n-dimensional column vector. 1 (k), x 2 (k), …, x 12 (k) represents the longitudinal displacement, lateral displacement, vertical displacement, longitudinal velocity, lateral velocity, vertical velocity, roll angle, pitch angle, heading angle, roll angular velocity, pitch angular velocity, and heading angular velocity of the underwater robot at time k respectively. represents the system control input vector at time k, where u 1 (k) and u 2 (k) represents the angular velocity and rotation speed of the propeller of the underwater robot at time k respectively. represents the system measurement output vector at time k, where y1 (k), y 2 (k), y 3 (k), y 4 (k), y 5 (k), y 6 (k) represents the longitudinal velocity, lateral velocity, vertical velocity, roll angular velocity, pitch angular velocity, and heading angular velocity measured and output by the system at time k respectively. represents the system control output vector at time k; represents the interference that satisfies infinite square additive, ω 1 (k),ω 2 (k),ω 3 (k) represents the disturbance caused by ocean current, seawater density and the robot’s own gravity change at time k; They are all known constant matrices. Indicates n 1 ×n 2 Dimensional real matrix.

[0042] In order to increase the operation time of underwater robots and reduce the energy consumption of information transmission, a dynamic event trigger protocol is introduced to schedule the transmission signal. Only when the measurement information of a certain underwater robot meets the trigger condition, the underwater robot will transmit the latest measurement data to the relay station for controller solution. Otherwise, the relay station still uses the transmission value at the last trigger moment held by the zero-order holder to control the robot system:

[0043]

[0044] Among them, k s and k s+1 denote the time when the sth and s+1th systems meet the triggering conditions for data transmission, ψ(k)=y(k s )-y(k) represents the triggering time k s The difference between the transmitted measurement value and the system measurement value at time k, k∈[k s ,k s+1 ). 0<ε<1, are all known scalars, represents a set of positive integers, inf{·} represents the infimum, ρ(k) is a non-negative variable inside the system and satisfies:

[0045]

[0046] in, is a known scalar that satisfies

[0047] Using a dynamic event-triggered protocol, communication signal transmission is infrequent, the number of communication requests that the relay station needs to process is relatively small, and the computing load is controllable. At the same time, the relay station is powered by the mother ship through cables, which can provide sufficient power to support high-performance and high-computing computing devices. The computing power of the relay station can still be guaranteed, and it can receive and process the control signals of multiple underwater robots in a timely manner.

[0048] In addition, the event triggering mechanism of each underwater robot is based on its own local perception and environmental feedback, such as water flow speed, temperature change, and obstacle distance. The environmental disturbances at different locations are usually different. This independent triggering condition determines that the signal transmission time of each underwater robot is highly random and dispersed. Even if multiple underwater robots send signals at a similar time, since the communication paths between each underwater robot and the relay station come from different locations and directions, and the signal propagation underwater is directional and dispersed, and is subject to different path delays and attenuation characteristics, even if multiple signals arrive at the relay station at the same time, they usually do not completely overlap. Therefore, the signals of multiple underwater robots are independent of each other in time and space, reducing the probability of communication conflicts.

[0049] Step 2: Static Output Feedback Controller Design

[0050] Considering that the system state of the underwater robot is difficult to measure directly in an economical and effective way, the system is controlled by output feedback. Combined with the dynamic event triggering mechanism given in step 1, the following static output feedback controller is constructed:

[0051] u(k)=Ly(k s ) (4)

[0052] in, is the controller gain matrix to be designed.

[0053] During actual operation, underwater robots may be affected by malicious attacks from the enemy. Usually, in order to make the attack signal more difficult to detect, the attacker will use a random strategy to send the attack signal, and the underwater robot system will deploy a certain network defense mechanism. Therefore, considering the randomly occurring deceptive attack signal, the following controller form is obtained:

[0054] u(k)=L[y(k s )+β(k)r(k)] (5)

[0055] Among them, β(k) is a random variable that satisfies the probability characteristics, When β(k) = 1, the system is affected by the spoofing attack, and when β(k) = 0, the system is not affected. is a known positive scalar, Prob{·} represents the probability of an event. r(k) represents the deception attack suffered by the underwater robot system when transmitting data:

[0056]

[0057] in, It means that after the attacker intercepts the data packet sent by the control system at time k, the data sent to replace the original data packet satisfies is a known matrix, and ||·|| represents the Euclidean norm.

[0058] The measurement signal of the underwater robot control system may be saturated before reaching the relay station. Due to the influence of the complex marine environment, the occurrence of saturation usually has random characteristics. Therefore, further considering the occurrence of random saturation, the following controller form is finally obtained:

[0059] u(k)=L[α(k)σ(y(k s )+β(k)r(k))+(1-α(k))(y(k s )+β(k)r(k))] (7)

[0060] where α(k) is a random sequence indicating the occurrence of saturation, is a known positive scalar. σ(·) is a saturation function σ(p) = [σ T (p 1 ),σ T (p 2 ),…,σ T (p 6 )] T , p=[p 1 ,p 2 ,p 3 ,p 4 ,p 5 ,p 6 ] T ,satisfy i=1,2,…,6. Where sign(·) is the sign function, min{} means taking the minimum value, Indicates p i The saturation threshold of || means taking the absolute value. The saturation function σ(·) satisfies the following fan-shaped conditions:

[0061] (σ(p i )-υ i p i ) T (σ(p i )-p i )≤0 (8)

[0062] Among them, 0<υ i <1 is a known scalar. The fan condition of the saturation function is extended to multiple dimensions:

[0063]

[0064] in, U = diag{υ 1 ,υ 2 ,…,υ 6},diag{υ 1 ,υ 2 ,…,υ 6} indicates that 1 ,υ 2 ,…,υ 6 is a diagonal matrix of elements. I represents the identity matrix with matching dimensions.

[0065] Combined with the controller, the following closed-loop control system equation of the underwater robot is obtained:

[0066]

[0067] Step 3: Based on the Lyapunov stability method, establish the underwater robot closed-loop control system to be asymptotically stable and satisfy H ∞ Sufficient conditions for performance indicators. Select the following Lyapunov function:

[0068]

[0069] in, is a positive definite symmetric matrix.

[0070] Consider the event trigger mechanism, when there is no trigger signal:

[0071]

[0072] From the restriction conditions of the deception attack r(k), we can get:

[0073] When the interference ω(k) is 0, combined with the fan-shaped constraint of the saturation function, we can obtain:

[0074]

[0075] in,

[0076]

[0077] In the formula, 0 represents the zero matrix of dimension matching, and the symbol * represents the transposition of the elements of the matrix symmetrically located along the main diagonal. is any positive scalar.

[0078] Therefore, to make E{△W(k)}<0, that is, E{W(k+1)-W(k)}<0, it is only necessary to make the inequalities Γ<0 and Θ<0 hold. According to the Lyapunov stability theory, the closed-loop control system of the underwater robot is asymptotically stable at this time.

[0079] Introducing performance indicator functions in, is a given positive scalar, representing the interference suppression performance of the system.

[0080] When ω(k)≠0, for any positive scalar ε, we can get in:

[0081]

[0082]

[0083] Obviously, if the inequality And Θ<0 holds true, then the performance indicator function J<0, we can get Therefore, the system satisfies H ∞ Performance indicators.

[0084] Depend on It can be seen that Γ<0, so if and Θ<0, the underwater robot system is asymptotically stable under the disturbance ω(k)=0, and satisfies the given H when the disturbance ω(k)≠0 ∞ Performance indicators.

[0085] Based on the above conditions, to solve the output feedback controller gain matrix, we first use the Schur complement lemma to convert the inequality The equivalent transformation is:

[0086]

[0087] Among them, P -1 represents the inverse of the matrix P,

[0088]

[0089] Decompose the column full rank matrix B into singular value form in are all orthogonal matrices, matrices It is a diagonal matrix composed of elements with non-zero eigenvalues ​​of matrix B.

[0090] According to the singular value decomposition method, there is a matrix Make If and only if the symmetric positive definite matrix P satisfies hour, in

[0091] Multiply the inequality Π<0 by the matrix diag{I,I,I,I,I,P,P,P,P,P,P} on the left and right respectively, and then use And order We can get the linear matrix inequality The matrix With the matrix Π except elements are different, the rest of the elements are the same,

[0092] Finally, the linear matrix inequality toolbox in Matlab software is used to solve the inequality and Θ<0, we get the values ​​of matrices P and K, and we can get the matrix B by decomposing it into its singular value. Y and P 1 The value of the underwater robot output feedback controller gain matrix is ​​further obtained as:

[0093]

Claims

1. A remote control method for an underwater working robot based on a relay station, characterized in that: The specific steps include: Step 1: Based on the general kinematics and dynamics principles of underwater robots, a control system model of underwater operation robots is established, and a dynamic event trigger protocol is designed. When the trigger condition is met, the underwater robot transmits the latest measurement data to the relay station for controller solution. Otherwise, the relay station still controls the underwater robot based on the transmission value at the last trigger moment. Step 2: Considering the random deception attacks and saturation problems, design a static output feedback controller and establish the closed-loop control system equation of the underwater robot: u(k)=L[α(k)σ(y(k s )+β(k)r(k))+(1-α(k))(y(k s )+β(k)r(k))] (1) Where u(k) represents the system control input vector at time k, L is the controller gain matrix to be designed; α(k) and β(k) are random sequences representing saturation and deception attacks, r(k) represents the deception attack suffered by the underwater robot system when transmitting data, y(k) represents the system measurement output vector at time k, and k s represents the time when the sth system meets the trigger condition for data transmission, σ(·) is a saturation function; Step 3: Based on the Lyapunov stability method, establish the underwater robot closed-loop control system to be asymptotically stable and satisfy H ∞ The sufficient conditions for the performance indicators are then transformed through singular value decomposition to obtain the gain matrix L of the output feedback controller.

2. A remote control method for an underwater working robot based on a relay station as claimed in claim 1, characterized in that: The following underwater operation robot control system model is established: Among them, k represents the system sampling time; x(k) represents the state vector of the underwater robot system at time k, u(k) represents the system control input vector at time k, y(k) represents the system measurement output vector at time k, z(k) represents the system control output vector at time k; ω(k) represents the interference that satisfies infinite square additive, and A, B, C, D, F, and G are all known constant matrices.

3. A remote control method for an underwater working robot based on a relay station as claimed in claim 2, characterized in that: x1(k), x2(k), …, x 12 (k) respectively represent the longitudinal displacement, lateral displacement, vertical displacement, longitudinal velocity, lateral velocity, vertical velocity, roll angle, pitch angle, heading angle, roll angular velocity, pitch angular velocity, and heading angular velocity of the underwater robot at time k; u1(k) and u2(k) represent the angular velocity and rotation speed of the propeller of the underwater robot at time k, respectively; y1(k), y2(k), y3(k), y4(k), y5(k), y6(k) represent the longitudinal velocity, lateral velocity, vertical velocity, roll angular velocity, pitch angular velocity, and heading angular velocity measured and output by the system at time k, respectively; ω1(k), ω2(k), and ω3(k) represent the disturbances caused by ocean currents, seawater density, and the robot’s own gravity changes at time k, respectively; represents an n1×n2 dimensional real matrix; the superscript T represents the transpose of a matrix or vector, Represents an n-dimensional column vector.

4. A remote control method for an underwater working robot based on a relay station as claimed in claim 1, characterized in that: Design the following dynamic event triggering protocol: Among them, k s+1 They represent the time when the system meets the trigger condition for data transmission for the s+1th time, ψ(k)=y(k s )-y(k) represents the triggering time k s The transmitted measured value y(k s ) and the difference y(k) between the system measurement value at time k, k∈[k s ,k s+1 ), 0<ε<1, are all known scalars, represents a set of positive integers, inf{·} represents the infimum, the superscript T represents the transpose of a matrix or vector, and ρ(k) is a non-negative variable inside the system and satisfies: in, is a known scalar that satisfies 5. A remote control method for an underwater working robot based on a relay station as claimed in claim 2, characterized in that: When β(k) = 1, the system is affected by the spoofing attack, and when β(k) = 0, the system is not affected. is a known positive scalar, Prob{·} represents the probability of an event occurring; is a known positive scalar; r(k) represents the deception attack suffered by the underwater robot system when transmitting data: in, It means that after the attacker intercepts the data packet sent by the control system at time k, the data sent to replace the original data packet satisfies H is a known matrix, ||·|| represents the Euclidean norm; The saturation function σ(·) satisfies With the following fan conditions: (σ(p i )-υ i p i ) T (σ(p i )-p i )≤0 (6) where 0<υ i <1 is a known scalar, i=1,2,…,6,σ(p)=[σ T (p1),σ T (p2),…,σ T (p6)] T , p=[p1,p2,p3,p4,p5,p6] T , sign(·) is the sign function, min{} means taking the minimum value, Indicates p i The saturation threshold of , | | indicates the absolute value.

6. A remote control system for an underwater operation robot based on a relay station, characterized in that: It includes a mother ship, a relay station and multiple underwater robots; the mother ship is put into the relay station in a designated sea area and connected to the relay station through a wired cable; the relay station releases multiple underwater robots in a designated working sea area; the multiple underwater robots communicate with the relay station through a wireless network, and transmit sensor signals to the relay station based on a set event trigger mechanism, the relay station performs calculations on the received information, solves the controller gain based on the method described in any one of claims 1 to 5, and returns the control command to the corresponding underwater robot.

7. A computer-readable storage medium having a computer program stored thereon, which, when executed in a computer, causes the computer to execute the method according to any one of claims 1 to 6.

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