Research On Fuzzy Control System Of Offshore Mobile Fish Cage

The inability of wild fisheries to supply the burgeoning demand for protein-richseafood has given rise to a robust aquaculture industry that has helped alleviate the threat ofoverfishing in the world’s oceans. But raising marine finfish in pens and ponds, whilecontributing to the availability of delicious sea food, has given rise to a range ofenvironmental concerns. Shore-based and inland farms, when poorly sited, can compromisewater quality, and compete for space with sea transportation, offshore drilling recreation,and so on.To solve these environmental concerns and protect the promise of aquaculture’s abilityto satisfy the demand for healthful fresh seafood, a new automatic offshore mobile fish cagesystem was developed in this paper, which is connected to a barge that tows with the ocean.The cage can move in6degrees of freedom, such as erecting, rotating, and descending. Thecomponents of the drifting fish cage consist of a rigid frame assembly with eight variableairbags. The variable airbags are used to change the buoyancy characteristics of the cagesystem by pneumatic control so that it can either be placed at the submerged or surface. Thecontrol system was designed so that when air is injected into the airbags by opening themain evacuation valve on the manifold, the model raised. By changing each airbag volume,it is modified to accommodate other functions, such as fish transfer, grading, feeding, andharvesting. The mobile cage system, which is constantly moving over the ocean’s surface,solves the potential problems of impacts on the seafloor or impacts on water quality, andappears to improve marine finfish health and growth.The control system is being developed with the view to augmenting the functionalityof existing sea cage systems and automating functionality such as cage robust capabilities.The nonlinear and under-actuated feature of sea cage is difficulty in control. According toestablishing offshore aquaculture systems mathematical model and simplified the model offish cage, the equations of cage motion in the horizontal plane are established.The modeling and control of automated mobile fish cage is considered by using aTakagi-Sugeno (for short T-S) type fuzzy model, which are represented by a set of IF-THEN fuzzy rules, and then local dynamic in the different state space can be regard asthe linear system. The nonlinear stochastic system controller can be blended by the linearcontrollers of all rules. One can build a model-based fuzzy controller design utilizing thenotion of Parallel Distributed Compensation (for short PDC) and Takagi-Sugeno fuzzymodel. The PDC concept is useful for the fuzzy controller design of T-S type fuzzy models.The control approach is to design linear feedback gains for each local linear model and letthe overall system input can be blended by these linear feedback gains. Utilizing theLyapunov theory, the sufficient conditions which guarantee the system stability areacquired. These sufficient conditions belong to the Linear Matrix Inequality (for short LMI)forms, which can be solved by the mathematical software. One can learn a suitablecommon positive definite matrix and linear feedback gains for each rule, and then to satisfythe stability conditions for closed-loop systems. The responses of states of fish cagedynamic T-S fuzzy model show in the simulation.The mobile fish cage is immersed in wind waves and the stochastic disturbances. Forhandle the complicated disturbances, the T-S fuzzy model is used to represent the nonlineardrifting fish cage systems with state multiplicative noises. For achieve variance, passivity,and stability performances at the same instant, some sufficient conditions are derived.Employing the matrix transformation technique, these sufficient conditions can beexpressed in terms of LMI.By solving the corresponding linear matrix inequality conditions, a PDC based fuzzycontroller can be obtained to guarantee the stability of the closed-loop nonlinear driftingfish cage systems subject to variance and passivity performance constraints. Simulationillustrates the applicability of the proposed multiple performances constrained drifting fishcage fuzzy control method.The system proposed will provide a single integrated control solution to the variety ofcontrol tasks required on commercial mobile fish cages i.e. control of buoyancy, control ofposition and in addition, provide functionalities such as external hazard discernment andprevention. Based on ATmega2560control system was proposed for reliable mobile control,a fish cage control system for ego adjustment using an inertial measurement unit (for short IMU) and other sensors is presented. Cage’s angle velocity and angle accelerationmeasurement of three axles are gauged by MPU-6050, which is to increase the cage mobilestability. The pulse width modulation (for short PWM) control method is used to transformthe effective cross sectional opening areas of the switch-type valves, so that to change eachairbag volume, buoyancy regulation characteristics of fishing cages. If the fish cage modelis inclined due to the buoyancy difference, the injected and released flow rate of theseairbags are adjusted according to the frame angle of the model cage measured by the IMU.The cage is free to move vertically within an air column by adjusting the weight and thebuoyancy with attitude control system. After the analysis of cage’s position and attitude,control parameters are studied and achieve the corresponding suitable control algorithm.Represent the rotation of fish cages using quaternion, dispatch the attitude to three separatecontrol angel and fuse the senor measurement.Finally, a series of model experiments were conducted to examine the workingperformance and characteristics of the mobile fish cage. The model of this system wasconstructed to be1/10the size of the full-scale system. Results of this tow test showed thatcages are low resistance, and longitudinal drag resistance is about2times of that of lateraldrag movement. The decreasing rate of the water volume could be less than6%. These arebeing used to enhance the numerical modeling capabilities of aquaculture cage systems.The experiments of the offshore mobile fish cages show that the design had high reliability.The control system performance indexes met the design requirements. The tests showedpromise that such a system could possibly be used on a much larger scale to avoid therigors of the environment in support of commercial level offshore aquaculture. Using themobile cage method, mariculture could produce large volumes of high quality seafood withreduced costs.