试验型水下滑翔机的动力学分析及实验

第20卷第12期 2016年12月船舶力学Journal of Ship MechanicsVol.20 No.12Dec. 2016Article ID：1007-7294(2016)12-1523-12Dynamics and Experiments of a Laboratorial Underwater GliderCAO Jun-liang1, CAO Jun-jun1, ZHAO Bao-qiang2, YAO Bao-heng1,3, LIAN Lian1,3(1. State Key Laboratory of Ocean Engineering; Institute of Oceanology, Shanghai Jiao Tong University,Shanghai 200240; 2. Qingdao Collaborative Innovation Center of Marine Science and Technology,Qingdao 266000, China; 3. China Ship Development and Design Center, Wuhan 430064, China)Abstract: In this paper, the design, implementation, and experiments of a weight-varied underwater are presented. The realization of the buoyancy engine is mainly accomplished by a unidirectional water pump and a three position five-way solenoid valve. The glider is designed to operate within 30 meters deep down to the water surface, and the detailed design process is introduced. The glider's equation of motion and dynamic features are presented and the steady-state solution is analyzed. The hydrody­namic coefficients are also calculated by using Computational Fluid Dynamics (CFD) method. Simula­tion and experimental results show the reliability and utility of the underwater glider.Key words: underwater glider; buoyancy engine; w eight-varied; dynamic; CFDC LC number: U674.941 Document code: A doi: 10.3969/j.issn.1007-7294.2016.12.0030 IntroductionThe interest in monitoring underwater environments by using conventional autonomous underwater vehicles (AUVs) and underwater gliders is growing in recent years. The practical applications include patrolling seaports, tracking oil spills, and monitoring harmful algal blooms111. The vehicle needs to be capable of high efficiency to maintain sustainable operating time du­ration, and meanwhile high maneuverability to negotiate with versatile environments. Under­water glider is a new dynamic underwater observation platform, known for its great energy-ef- ficie ncyand long-durationoperationinoceanographicapplications[21, w h ic h u tiliz e s its n e t buoyancy to achieve motion without any additional propulsion system and alters its center of gravity to adjust attitude.Legacy underwater glider is driven by the change of net buoyancy which is mostly achieved by adjusting its volume of displacement and meanwhile its weight is remain unchanged such asSeaglider丨31,Spray丨41,andS locum丨51.T hehyb rid-d rive n u n d e rw a te rg lid e risa n o ve lre se a rch area in recent years, for instance, Folaga丨61hasadivingactuationm echanism asanoceano- graphic glider and autonomous surface navigation capabilities as self-propelled AUVs; PETRAL[71Received date: 2016-06-25Foundation item: The Research Fund for Science and Technology Commission of Shanghai Municipality(STCSM) (No.13dz1204600)Biography：CAO Jun-liang(1989-), male, Ph.D. candidate ofShanghai Jiao Tong University, E-mail:xavier.cao@; LIAN Lian(1962-), female, professor/tutor of Shanghai Jiao TongUniversity, E-mail: llian@.1524船舶力学第20卷第12期and Sterne[8] are designed with both ballast control and a thruster. Other driven solutions have been used: the ALBAC design uses a drop weight to drive the glider in a single dive cycle be­tween deployment and recovery from ship[9]; SML glider[1] is a miniaturized underwater com­bines the desirable features of both an underwater glider and robotic fish; Wave glider[10] is an unmanned maritime vehicle (UMV) unique in its ability to harness ocean wave energy for platform propulsion.In this paper, the change of net buoyancy is achieved by adjusting the body weight while the volume of displacement is remain unchanged. For conventional bidirectional water pumps, either the volume is oversized for underwater glider or the flow rate is dilatory for the buoy­ancy adjustment process. The mechanism in this paper has overcome these problems and veri­fied through experiments. This kind of underwater glider is easier to operate than conventional gliders, suitable for fundamental studies and laboratorial experiments. Also, the hydrodynamic model and mathematic model have been analyzed to obtain the necessary parameters which w ill be used in the simulating process. The experimental results have demonstrated the relia­bility and utility of the glider.This paper is organized as follow: the glider description and the design process are intro­duced in Chap.1; the establishments and analysis of mathematic model as well as the hydro­dynamic model of the underwater glider is given in Chap.2; the experiment results comparing with simulation results are shown in Chap.3; finally the conclusions and future works are drawn in Chap.4.1 Glider descriptionAs a demonstrated underwater glider in this study, it is designed to work 30 meters deep under the water surface. Some of the main design parameters are listed in Tab.1. The pressure Tab.1 M ain parameters o f the gliderhull of the underwater glider consists of the front pod, cylindrical hull and the rear pod. The material we choose is polymethylmethacrylate (PMMA), which is a transparent organic com­pound capable of considerable compression strength and appropriate for the experimental underwater glider. The front pod and rear pod are designed in streamlined shape to optimize the lift-drag ratio. The aspect ratio of the wing is 4.0, while the taper of the wing is 3.0, andit has a sweepback of 18 degrees so that the glider is in best working condition.Be distinguished from other underwater gliders in the world, the glider in this study ad­justs its net buoyancy by absorbing and draining ambient water. Compared with other volume- varied underwater gliders, this buoyancy engine (Fig.1) is much simple in processing and easyParametersSymbol Value Hull lengthLh 1.7 m Length (antenna included)L 2.0 m Wing span W 1.1m Weight of glider m 36 kg Weight of moving mass m p6 kg Displacement m v35.7 kg Outer diameter d 17 cm Wing areaS 0.21 m2Max. operating depthD30 m第12期CAO Jun-liang et al: Dynamics and Experiments o fa 噎1525to control. Besides, other underwater gliders usually must be capable of the ability to monitor the flow rate pre­cisely, while mechanism in this paper is simplified by controlling the work­ing time of the pump.The greatest difficulty in the de­sign process is to control the size of water pump and guarantee the pump­ing rate at the meantime. For conven­tional bidirectional water pump, either the volume is oversized for underwa­ter glider or the flow rate is dilatoryfor the buoyancy adjustment process. To deal with these problems, a unidirectional water pump and a three position five-way solenoid valve is used. The function of the three position five-way solenoid valve is to change both the water inlet and outlet simultaneously. A small capsule is set in the mechanism as an accumulator since the switch of the valve needs a start-up pressure.The same as most underwater gliders, changing the center of gravity is achieved by trans­lating an internal moving mass (including the battery), which is usually weighted 15%-20% of the whole glider. More translating distance w ill be needed if the moving mass is lighter, which w ill extend the length of the glider. Otherwise, if the weight of moving mass is too heavy, the attitude adjustment w ill be sensitive excessively, causing the underwater glider be difficult to control. The movement of the mass is accomplished by a high efficiency and high accuracy lin­ear actuator for the pitch system, the position of the moving mass is measured by the rotation of the stepper motor, which is convenient to control and operate precisely.The roll actuator is utilized another single mass for the sake of convenient, which is de­signed in a half-cylinder shape so that the center of gravity is slightly below the centerline of the glider. It is also driven by high efficiency and high accuracy stepper motor connected with worm gears to achieve the rotation.Several sensors are equipped on the underwater glider to collect data and monitor the operating status. A pressure sensor and a temperature sensor are installed at the front cover to record the operating depth and ambient temperature; an attitude sensor is set in the electronic bay to monitor and provide the attitude angles and angular accelerations for the control algo­rithm; a flowmeter is concatenated with the water bladder monitoring the working status of the buoyancy engine.2 Modeling2.1 M athem atic modelIn this paper, the underwater glider is modeled as a rigid-body system, with an externalFig.1 Buoyancyengine1526船舶力学第20卷第12期force and moment exerted by an internalmovable mass. The sketch map of the glid­er in the body-fixed reference frame de­noted as Oxb y b zb is shown in Fig.2; theorigin O is located at the geometric cen­ter, which w ill be the point of applicationfor the buoyancy force. The Oxb axis is a­long with the body’s longitudinal axis pointing to the head; the Oyb axis is per­pendicular to the O xb axis and pointing to the right wing; the Ozb axis is perpen­dicula r to the other axes and pointing downwards. The pitch angle 兹is defined as the angle between Oxb and horizontal plane; while the angle of attack 琢is de­fined as the angle between the velocity and Oxb. v = [ v1f 0, v3 ]stands for the trans­lational velocity of the glider, expressed in the body-fixed reference frame.The longitudinal equations of motion a re a d o p te d fro m th e re fe re n ce[111, which are restrict in the vertical plane. The def­initions of all variables appearing in e­quations of motion are listed in Tab.2.Fig.2 The glider’s reference framesTab.2 Definitions o f all variables appearing in longitudinal equations o f m otion ofthe underw ater gliderTitle Physical significance琢angle of attackD drag force componentg acceleration due to gravityL lift force componentm〇vehicle heavinessm"m3added mass along body-1/ body-3 directionm internal moving massm b ballast massM d l2pitching momentJ2added moment of inertia along the body-2 direction赘2pitch rate(rp 1, rp3) position of m with respect to CB in body coordinates 兹pitch angle(v 1, v3) velocity components in body coordinates兹=赘2赘2= 士（m j m) (m3+m j Y_m|m3+m)r P3X1-m1m|m3+m jr P3w1+ m (m j m) rn X3-1 m jm) mm3 ^ r p1 赘2v1=—^ (X1-m rP3 i赘2-mw1)m1+mv3=—(X3-m rP1 i i2+m rP1 赘2)m3+mr P1 =r P1r P1 =w1mb=W4(1)⑵⑶⑷(5)(6)(7)第12期CAO Jun-liang et al: Dynamics and Experiments o fa 噎1527wherea=J 2 (m 1+m) (m 3+m ) +mm 1 (m 3+m ) rP 3 +mm 3 (m 1+m ) rP 1(8)¥，3_，，3-1^2(卜1+^赘2^)^+(^弋1赘2)^)-m g(rn cos 兹+rp 3sin 兹）+MD L 2(9)X 1=-m (v 3-r P 1 赘2)赘2 -m 3赘2v 3-m 0 gsin 兹+Lsina-Dcosa (10)X 3=m (v 】+rP 3 赘 2 + r P 1)赘 2 +m 1 赘 2 V 1+m 。