Design and Implement of a Trimaran Unmanned Surface Vehicle System

Proceedings of the 2007 International Conference on Information Acquisition July 9-11, 2007, Jeju City, Korea

Design and Implement of a Trimaran Unmanned Surface Vehicle System Juntong Qi and Yan Peng Robotics Laboratory Shenyang Institute ofAutomation, Chinese Academy Sciences Shenyang, Liaoning Province, China Graduate School, Chinese Academy of Sciences Beijing, China {qijt & pengyan} @uspringfield.edu

He Wang, Jianda Han Robotics Laboratory Shenyang Institute ofAutomation, Chinese Academy Sciences Shenyang, Liaoning Province, China

{wanghe & jdhan} guspringfield.edu

Abstract - This paper describes recent research on system design of a Trimaran Unmanned Surface Vehicle (TUSV) control system and a control scheme for such a vehicle. The trimaran is to be designed as a test bed for the implementation of new

In the recent work, we have designed and implemented a TUSV prototype. The trimaran, control box, PC-104 control computer, communication units, sensors such as inertial measured unit (IMU), compass, altimeter and so on should be

nonlinear control theories. The full system has been tested successfully in the manual operation and obtained useful data, which is to be analyzed and used in identifying the TUSV model and design advanced control technologies. A control methodology

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dsigned, comp andchosen Wo assemble the graoun supporting system which is used to pre-schedule the trajectory,

update the onboard computer program and collect useful data. A wireless-LAN will be used to provide the real-time communications between the control computer and the ground supporting station. The software frame based on QNX realtime operation system (RTOS) has also been constructed including PWM output module, 8-serials sensor data collecting module, 8255 timer speed sensor module and wireless commutation module. A wide range of control methodologies have been applied to previous underactuated ships, but the control of trimans has less been mentioned. In this paper we present the methodology of multi-channel decoupling PID control which is necessitates the development of a plant model. The brief of this paper is as follow: In the Section II, we Tr e thed of th e Ts system. The Sembin of the TUSV system will be present in Section III. The multichannel deoupl PI control methoology isTesignedii ctin IV. In the end, we conclude our work and discuss issues for future research.

for trimaran, which is based on nonlinear dynamic equations with a simplified thrust-torque generation model valid for cruising is presented. Index Terms - Trimaran,

USV, controller design, PID control

I. INTRODUCTION Unmanned surface vehicles (USV) can be made as a platform for pure academic research and many applications where human intervention is considered difficult or dangerous Marine vehicles have been dramatically researched for over a decade. Currently, many types of ships have been operating on the seas or rivers such as cargo ships, container ships, fishing ships, and tanker ships. Traditionally, the underactuated ships have been served as the unit for above missions because its simple, symmetric, decoupled dynamics and stable futures, and have many successful records in actual field operations. The underactuated piece hulls of a special type speed trimarans are constructed by a main center hull and two small outer hulls, which could be called Small Outer Hull Trimarans(SOHT), they provide spacious deck surface as one of their main advantage. Because of the particular construction, the high speed trimarans, SOHTs have lower resistance,excellent sea-keeping performance, obvious virtue in general layout and stealth, compared with single hull ships or catamarans. In particular, high speed SOHTs cancel the waves by the wave interference effect from each piece hulls to reduce wave resistance; alleviate the "diagonal shake" and "fast roll", which often occurs in the catamarans; damp the os rmudrae hphls pitch and heave; shield noise . ' from . .underwater ship . hulls.. Now, sea-keeping performance is paid more attention, so is the stealth. Therefore in recent years the unconvertional ship forms are studied and applied more than ever, and their size tends to increase. High speed trimarans manifest obvious virtue in these aspects so that the high speed trimran are desirable platform ofthe frigates in future.

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II. DESIGN AND IMPLEMENTATION OF TUSV CONTROL SYSTEM The overall TUSV system comprises of the trimaran platform, the onboard control system, and the ground monitoring station. The trimaran itself is able to operate with the control computer system and onboard sensors independently. The full duplex wireless-LAN equipments are installed in the ground station and the USV system to exchange data from them including receiving commands from the ground system and reporting the operating status or damages to the ground station. The architecture of the possible in Figure 1. TUVcnrlsteispsnednFgue1 control system iS presented ~~~~~~~TUSV

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The onboard control system is responsible for the overall TUSV main managements including navigation, autonomous control, communication and so on. The PC- 104 control computer, communication components and sensor units including inertial measure unit, global position system (GPS), digital compass, are installed onboard. In our research in the project, PC-104 computer system is used as the onboard computer which is shown in Figure 3.

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A. Trimaran Platform As the basic vehicle of the TUSV system, we chose the trimaran which is designed by Dalian University of Technology. Such a choice is easy for us to exchange the accessories and cost low price. The trimaran, shown in Figure 2, is a high quality ship which is changed by us using a ship platform operating with a remote controller. The modified system allows the payload of more than 5 kilogram, which is sufficient to take the whole onboard control box and the communication units. The trimaran is constructed by a main center hull and two small outer hulls, which could be called Small Outer Hull Trimarans(SOHT), they provide spacious deck surface as one of their main advantage. The vehicle is powered by a 500W motor which generates 30hp at about 2000 rpm, practical angular rate ranging 100 to 2,000 rpm. The full length of the vehicle is 1609mm as well as the full width of it is 232mm.

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Fig. 3 PC-104 computer system

The control computer installed in control box is a typical industrial embedded computer system, so-called PC-104 which the whole system is kept as compact and light-weight as possible. The PC-104 has the ISA or PCI bus which features a 108.2cm X 115.06cm footprint circuit board. Our control computer system consists of a main CPU board and some other peripheral boards such as DC-DC power supply board, 8-channel serial communication device and PWM generation board. The main CPU board has a Celeron processor at 400MHz with 256MB SDRAM, fully compatible with the real-time operation system such as QNX. Hard drive or other equivalent mass-storage device for booting and running an operation system and store useful sensor data is needed to the control (aCF card by KingStone® is a computer. The C aompct Flash 1GB flash RAM device and is suitable for air environment. Th Eurotech®* PC- 10 procswsor boIard has oly two ;seialu ports, which are not enough for collection data from more than two sensors that communicate with serial port. As a result, a serial port expender is packed with the main CPU board providing RS-232 / 485 communications. In order to control the Futabag model helicopter servos, a PWM generation board is needed. Take price and reliable as consideration, DSP board is chosen to generate PWM signal as wel as capture te ~~~~~~~PWM\ signal encoded by remote controller when the system run at manual mode. Such a design is to ensure that the system can run independently at manual mode, which the close loop of the servo control is not through PC- 104 processor except for receiving the commands of servos form serial port. Li-Ion battery serves as a power supplement to the overall onboard communication units and servos through DC-DC converter.

Fig. 2 SIA-Trimarann Vehicle B. ControlComputer system

system design requirement of converting a 9-40V DC input

~~voltage to multi-voltage power outputs including ±5V, ±3.3V 362

and ± 12V with overload protection. An optional onboard microprocessor monitors the temperature of the module and protects it by turning the module off when temperatures exceed 85 centigrade-degree. The power supplement of the overall control system as well as five servos that control the

helicopter is powered by a Li-Ion battery pack which has the capacity of 78W`H at the output of 19V. To our control system, a real-time operation system (RTOS) is required for the onboard computer system. After carefully consideration and comparison, QNX Neutrino RTOS is selected as the operation system, which is ideal for embedded real-time applications. It can be scaled to very small size and provides multitasking, threads, priority-driven preemptive scheduling, and fast context-switching - all essential ingredients of an embedded real-time system. The applied program can be coded and debugged in the remote

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supply. Loop again, current limit, input gain and offset can be adjusted using 14-turn potentiometers. The offset adjusting potentiometer can also be used as an on-board input signal for testing purposes when SW1O is ON. The two auxiliary motors are Maxon® electronically commutated (EC) motors. The characteristics of the motor are Neodymium magnets, unsurpassed life time, no abrasion, low noise level, high speeds even at low voltages, no magnetic cogging, good heat dissipation, high overload ability, very small electrical time constant and low inductance. The motors are high quality DC motors with neodymium magnets. Unlike Maxon® DC motors, the iron-less winding is stationary in this case. Instead, the permanent magnet turns in the electrically generated rotating field of the three-phase winding. We choose Maxon® 4-Q-EC Servoamplifier DES as the control of the auxiliary motor. With the Hall sensors and Encoder closed loop, the digital servoamplifier with sinusoidal power commutation for perfectly controlling EC motors. The control can reach an output of up to 700 watts which is satisfied our

requirements. The heading servo which we used is Futaba® S5301 high

torque. The dimension of the servo is 6.1 * 3.05 * 5.08 cm while the weight is of it is 124.74 g. High torque for the heading control of the trimaran is required. S5301 can provide 291.5 oz-in torque at the speed of 0.23 sec/60deg when working at 6.OV. The servo is controlled by PWM\ input which is generated by PC- 104 peripheral board. E. Communication Devices To exchange data between the onboard computer system and the ground computers, two Lucent® wireless access point devices, which are shown in Figure 7, are installed both in the TUSV onboard control system and ground supporting station.

computer program developments and monitors its real-time status. The pre-scheduled trajectory and commands as well as the synchronized sensor data are transmitted and received by wireless modem. The ground control computer is a notebook computer, which sends the pre-scheduled commands and trajectory to the onboard control computer. The program of the ground control computer is developed by C++. The interface of it is present in the Figure 8. Development computer is used for the onboard software development of QNX Neutrino RTOS as well as the DSP processor. QNX Momentics IDE which is an integrated development environment of the QNX system is installed in the computer as a windows-host to modify the remote control computer programme. As the same to the QNX system, Code Composer Studio IDE (CCS) is also setup in the development computer to change the programme in the DSP which is the PWM signal generator in onboard control box. The 9-channel RC controller which is at 35MHz radio communication signal is used in manual mode in system modelling.

Fig. 8 Interface ofthe ground control computer III. ASSEMBLING OF THE TUSV SYSTEM

Designing the control box and packing the box appropriatel in te carbin of te timaran are tomain tasks to implement of the TUSV system. In the actual surface and vehicle environment, the quality

Fig. 7 Lucent wireless access point

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364

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