SHIP MODEL BASIN CARRIAGE CONTROL SYSTEM

Transcription

1 10th International DAAAM Baltic Conference "INDUSTRIAL ENGINEERING May 2015, Tallinn, Estonia SHIP MODEL BASIN CARRIAGE CONTROL SYSTEM Liyanage, D.C., Aasmäe, E., Sutt, K.O., Tamre, M. Hiiemaa, M. Abstract: Modern ship model basin towing carriage control systems demand advance features which are not possible with ordinary motion control systems. When it comes to relatively shorter length towing tanks which are designed to use with belt driven carriages the control system development is more challenging task. This paper concerns about the design of towing carriage control system for ship model towing tank built in Kuressaare College of Tallinn University of Technology, Saaremaa Estonia. The following study covered requirement analysis, system design, control equipment selection and concept validation of the proposed towing carriage control system. And also it includes proposals for future tasks regarding robust positioning system for belt-driven servo mechanism. Key words: Ship model basin, towing tank, towing carriage control 1.INTRODUCTION There are number of ship model tow tanks that are used by various research institutes to investigate hydrodynamic performance of ship hull designs. Majority of them are longer than 100m [ 1 ] lengthwise and are capable of different simulations from calm water resistance tests to vessel maneuvering characteristics predictions. Most of the towing carriages are powered by direct drive mechanisms. Due to longer length of the tank it is possible to achieve higher velocity with enough acceleration distance. The size of the basins used for ship model testing varies greatly depending on the tests desired. A basin with bigger dimensions can be used for deep water testing or maneuvering testing. The paddles used in the basin also define its use. In modern testing facilities two kinds of paddles are used. Flap paddles that are mounted to the bottom of the tank for generating deep water waves where there is negligible motion at the bottom and the orbital particle motion decays with depth. And piston paddles that for generating shallow water motion. Neither of these types of paddles achieve the motion that accords to real waves. For that a combination of paddle types are used. In our case calm water resistance tests and head or following sea resistance tests were required. For that the measurements of the pool are 60 m x 6m. and flap paddles are used for wave generation. After receiving the instructions from the client and getting a final overview of the objective a clear plan of action was made. Firstly it was necessary to select suitable equipment for the carriage control system. As a next step we had to work out the concept of the human machine interface and the graphical user interface for the system. 2. SYSTEM DESIGN System design was started with requirement analysis of the ship model basin. Then the design concept has been developed. After that the equipment selection, field bus selection and concept validation were carried out. 2.1 REQUIREMENT ANALYSIS

2 The requirements for the carriage movement parameters and the motor selections were set by the client in the documentation presented to us. Based on that information.. Fig 1. Dimensions of the ship model basin The requirements given for the carriage movements showed the maximum speed of the model to be at least 5.5 m/s and the acceleration distance nor the deceleration distance to exceed 6 m. The required level of speed has to be kept with the accuracy of ± m/s. Also the accuracy tolerance of the carriage trajectory must not exceed ± 01 mm/m in relation to water surface. 2.1 SYSTEM CONCEPT The towing carriage has been designed to use belt drives to pull the from both sides. So that drive control system comprised of two synchronous servo motors to drive the carriage. Fig 2. Carriage control system block diagram According to the conceptual diagram Fig 2, the motion controller is controlling two servo drives and IO modules. And also HMI and remote IPC connected to the same motion controller. The motion profile, which governs the carriage movement will be built desktop application running in the IPC. This profile defines the position of the carriage, velocity, acceleration or deceleration values. And the status information and basic system controls are presented in HMI. Line topology used in servo drives and IO modules sub network. Since multiple drives driving the carriage, they are need to synchronize with fast industrial fieldbus. When it comes to locating the components, motion controllers need to be installed in the operator room area which is starting side of the pool and servo drives and IO modules need to place on the other end which is close to servo motors and sensors. This concept makes the controllers and drives apart more than 60m in distance. 2.2 CONTROLLER SELECTION It was proposed that Lenze synchronous servo motors and servo drives would be most suitable for the application. This selection imposed constraint to select suitable controller by maintaining interoperability. Other than that, there were several key requirements to fulfill by the controller which are listed below. Modular system - To be expand based on future requirements. Multiple motion axes synchronization MATLAB/Simulink integration Communication interface to desktop application software development (Visual C#, VB.etc.) Multiple programming language support Web server availability for remote data visualization. Multiple fieldbus options availability - Interoperability with other devices.

3 Based on above mentioned requirements, several motion control systems has been investigated. As a result Beckhoff CX2030 series controller has been selected. It is an embedded PC which allows to connect up to 20 servo axes and connect many IO modules in different network configurations. the field bus for the towing carriage motion control application. 2.3 SELECTION OF FIELD BUS Choose a suitable field bus protocol was influenced by the high speed data communication requirement of the project. Since each servo motor will be driven by individual servo drives respectively, the time delay between velocity commands for each axis should be less than 20ms. Fig 3 shows the potential failure by de-railing the carriage in case of delay in velocity command execution. Below are the list of requirements imposed by the application to select suitable field bus. Fast data rate to communicate messages between synchronous axes. Synchronized clocks to trigger motion in order to minimize lag. Interoperability - Open standard protocol which is compatible with multiple vendor motion control devices. Topology - There is a need to have several network topologies in the system. Distance of the communication bus more than 60m. Ethernet based communication protocol. EtherCAT which is based on ethernet protocol, and known to be fastest fieldbus in the market, priority dependant, deterministic communication and multiple topology support are fulfill all requirements of the application[ 2 ]. Therefore EtherCAT protocol was selected as Fig 3. Carriage movement in case of belt tension difference. 2.4 CONCEPT VALIDATION After selecting the controllers, IO modules and interface devices, it was investigated the functionality of different motion concepts and different software integration techniques in a simulated environment. This was done in order to check whether the controller can be used for the carriage control system application. By using the built in motion and communication functions of the controller software development tools (TwinCAT 3) several test programs has been done. They were to synchronize two motors and move them according to different motion profiles which is similar to the end user requirements. And also communicate with desktop applications written in Visual C#. 3. DISCUSSION, FUTURE WORK During the design of the system it has been completed system design, component selection and testing various motion functions available with the controller software development kit (TwinCAT 3). This can ensure the functionality of the system. But still there are technical challenges imposed by mechanics of the system.

4 Since the towing carriage uses tooth belt driven servomechanism to pull it from both sides, this can be induce vibrations while it is in motion with different motion profiles. There are several contributory factors to vibrations. One of them is the elasticity of the belt drive, which demands to incorporate robust position control scheme overcome belt-stretch issues. In a similar study about belt drive systems it has been identified that non-linear friction of the system also cause positioning errors[ 3 ].And also gear reducers add backlash which may result in vibrations during motion. The resonance in the system also accumulate positioning errors [ 4 ]. Therefore all these cases demands advance control schemes for positioning. As part of the study it was investigated possible control solutions to overcome above mentioned positioning errors. There are some studies regarding accurate positioning of servo mechanisms using sliding mode control theories[ 5 ]. And also in a later study same authors has incorporated sliding mode control in conjunction with asymptotic disturbance observer[ 6 ]. And similar accurate positioning efforts has made by other authors using fuzzy-logic control systems[ 7 ]. Fig 4. Belt drive system of towing carriage. During controller selection, it was considered the possibilities of including MATLAB model into the motion controller. This is to try out different motion control models and optimize it. 4. CONCLUSION The development of control system is currently underway to its completion. At present the conceptual system design has been done according to the requirements of the facility. Based on evaluation of the motion functions, Visual C# application integration it has been proven that the controller is capable of fulfilling demanding control requirements. 5. REFERENCES [1]. 0of%20facilities/Index/index.pdf, retrieved on 9-May [2].EtherCAT technology group, EtherCAT - the Ethernet Fieldbus, Nov [3].Jokinen,M.; Saarakkala, S.; Niemela, M.; Pollanen, R.; Pyrhonen, J.; Physical Drawbacks of Linear High-Speed Tooth Belt-Drives, SPEEDAM 2008 IEEE Conf, June-2008, pp [4].Jayawardena, T.S.S.; Nakamura, M.; Goto, S.; Accurate Control Position of Belt Drives Under Acceleration and Velocity Constraints, Int'l Jnl of Automation & Systems, 2003, 1, pp [5].Hace, A.; Jezernik, K.; Sabanovic, A.; A new robust position control algorithm for a linear belt-drive, Proceedings of IEEE Int'l Conf Mechatronics, June-2004, pp [6].Hace, A.; Jezernik, K.; Sabanovic, A.; SMC with Disturbance Observer for a Linear Belt-Drive, IEEE, Dec-2007, 54, pp [7].Kulkarni,S.A.; El-Sharkawi, M.A.; Intelligent Position Control of Elastic Drive Systems, IEEE Energy Conv, Mar- 2001, 16, pp CORRESPONDING ADDRESS Dhanushka Chamara Liyanage Department of Mechatronics. Tallinn University of Technology, Ehitajate Tee 5, Tallinn 19086, Estonia. Phone: ,

5 ADDITIONAL DATA ABOUT AUTHORS 1. Dhanushka Chamara Liyanage, MSc Student Eva Aasmae, MSc Student Kristofer Ott Sutt, MSc Student Mart Tamre, PhD, professor Maido Hiiemaa, PhD, researcher