| When studying the navigation performance of a new ship type,a ship Model Basin Test is required.Captive Model Test is one of the important experiments to test the maneuverability of the ship.The common equipment for captive the ship model motion is the Planar Motion Mechanism,which is mostly a two and three-degree of freedom constraint device.It can now make the ship model realize the constraint of six-degree of freedom motion.There are fewer Captive Model Test devices.The cable drives parallel mechanism has the characteristics of high bearing capacity,high precision and little disturbance to the fluid environment.There are many research and application cases in wind tunnel experiments such as airplanes in view of the similarity between the Captive Model Test and wind tunnel test,this paper it is proposed to introduce the cable drives parallel mechanism into the Captive Model Test,and explore and study its application.The control problem of the six-degree of freedom ship model cable drives redundant parallel mechanism is one of the key problems in applying the Captive Model Test.In this paper,the six-degree-of-freedom ship cable drives redundant parallel mechanism applied to the Captive Model Test is taken as the research object,the physical experiment prototype of the mechanism is built,the data measurement and motion control software is developed,and the six-degree-of-freedom ship model is studied.The Coordinates and attitude angles control strategy of the cable drives parallel mechanism is carried out,and test the actual control result.Firstly,for the structure of the six-degree-of-freedom ship model cable driven redundant parallel mechanism,the kinematics and dynamics model is derived.The optimal solution model of the cable tension is established based on characteristics of the cable.The modified feed-forward PD controller and tension feedback controller are designed.The compensation controller uses ADAMS/Simulink for joint control simulation in the absence of external loading.The simulation results show that the modified feed-forward PD controller can achieve good control effect without external loading.However,when a constant external load is added,the position errors will be generated 1.6mm;under the external load with constant or periodic variation,the position error of the moving platform is reduced to 0.1mm significantly counteract the influence of the external load.Secondly,using the modular design idea to build the experimental prototype of the cable rives parallel mechanism,adding the force sensor to the cable tension control module on the existing ball screw structure,combined with the incremental PI control algorithm to achieve the purpose of controlling the cable tension.The three-dimensional pose measurement module was designed by laser displacement sensor and gyroscope,and the three-dimensional pose calculation equation was derived.Based on the industrial computer and Lab VIEW,the upper computer control software consisting of six sub-modules was developed.Finally,the trajectory control experiment based on the modified feed-forward PD controller and the tension feedback controller is performed on the moving platform on the experimental prototype.Under no-load conditions,the position and attitude angle errors of the dynamic platform based on the modified feed-forward PD controller is respectively ±2mm、±0.2°.After loading the 20kg weight,the tension feedback controller is used to perform the combined motion in the direction of single degree freedom and the direction of multi-degree freedom.The error of the position and attitude angle of the moving platform can still be kept within 2mm、0.2°.The simulation experiment and prototype experiment results show that the designed tension feedback compensation controller is effective for the control of the six-degree-of-freedom ship model cable drives redundant parallel mechanism,which can avoid the cable slack and suppress the interference of the external load.The application has important engineering reference significance. |
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