examples of auvs in this document use a thruster having a first end and a second end and configured to propel fluid flow in a direction from the first end to the second end and in a direction from the second end to the first end and arrange multiple first connectors or valves in fluid communication with the first end of the thruster and multiple second connectors or valves in fluid communication with the second end of the thruster . each of the first and second connectors can be opened to allow the fluid flow and closed to block the fluid flow . the opening and closing of each connector can be individually controlled . the opening and closing of the first and second connectors and the two opposite flow directions provided by the thruster can be controlled to allow the fluid flow to enter one or more connectors and to exit one or more other connectors in various flow configurations . hence , this combination of the first and second connectors and the thruster forms a reconfigurable multiplex thruster system using a single thruster . the various flow configurations of this reconfigurable multiplex thruster system can be channeled to propel the fluid flow in various configurations to provide multiple motions of an auv utilizing such a reconfigurable multiplex thruster system . an auv may be designed to use one or more such reconfigurable multiplex thruster system and the auv examples provided below use a single reconfigurable multiplex thruster system . auvs based on the present reconfigurable multiplex thruster system can be small , agile , easy to use and maintain , versatile for multiple functions , and adaptable and reconfigurable for different sensors and instruments in the field . the auvs provided herein can be compact , inexpensive , and marine - approved systems that may integrate various technologies , such as intelligent robotic behaviors , autonomous navigation and control , modular and reusable hardware and software , reconfigurable components , embedded systems , advanced micro sensors , power technology , underwater communication and packaging techniques . the auvs can include a underwater actuation system that has a multiplex - thruster which may enable the auvs to have omni - directional movement and satisfy other demanding actuation needs without increasing the size , weight , power , and cost . the auvs can also include a modular architecture that may enable and support the auvs &# 39 ; components to reconfigure , exchange , and plug - and - play for versatile needs ( such as multifunction or multi - sensory ) as well as for easy deployment , operation , and maintenance in the field . the auvs can have a wide range of applications in the industry for underwater actuation and systems , including oceanographic measurement , environmental monitor and protection , aquaculture , and offshore oilfields . a multiplex - thruster ( mt ) system that can be used in the auvs provided herein can include a single thruster and a flow multiplexer with multiple channels to deliver thrusting flow to wherever and whenever it is needed for generating torque for underwater vehicles . to compare the present mt system to some other thrusting systems used in various underwater or surface vehicles , an analogy of comparing two different electrical systems can be used . the present mt system is analogous to an electrical system in which there is one generator for the entire system and the electricity is delivered via wires and switches to where it is consumed . some other thrusting systems are analogous to an electrical system in which there are many generators and every consuming device has its own generator . the present mt system can be economic , lightweight , and flexible , whereas some other thrusting systems can be expensive , heavy , and hard to change . as shown from this analogy , the present mt design can be implemented to consume low power and to be lightweight , flexible , and can be capable of dynamically controlling the thrust distribution , direction , and configuration at the run time . the present mt system may provide capabilities that go beyond the capabilities of many other thrust systems . a multiplex - thruster can provide desired movement and spinning with much less weight and power consumption . the present mt design can be flexible , power efficient , and can be dynamically controlled for thrust direction , distribution and configuration , to achieve better performance , speed and accuracy . mechanically , a mt is a thruster plus a multiplexer with multiple channels whose states can be dynamically configured and controlled so that thrust can be directed to flow from some channels into some other channels . each channel can have three possible states : input , output , and closed . an input channel allows current to flow into the mt ; an output channel allows current to flow out from the mt ; and a closed channel blocks any current flow . multiple channels can be set into the same state . both input and output channels must exist in order to use a mt as a thruster . the number of channels that a mt can have and the direction that a channel can direct the flow may be selected based on specific needs or requirements in a vehicle .. furthermore , the state of a channel can be a continuous value ranging from − 1 . 0 to + 1 . 0 , with 0 . 0 representing the closed state , − 1 . 0 representing the fluid input with a full opening , and + 1 . 0 representing the flow output with a full opening . state values other than 0 . 0 , − 1 . 0 and + 1 . 0 represent channels to be partially opened or closed for inputting or outputting the fluid so that the amount of flow can be precisely controlled to achieve a desired movement or maneuver . fig1 ( a ) shows a concept diagram for an example mt 100 . the mt 100 has a thruster 110 and six bi - directional channels 120 a - f that are connected to the thruster 110 . each channel 120 a - f has three states of operation : input , output , and closed . when a channel 120 a - f is set to be input , the thruster 110 can flow fluid into the mt 100 through that channel 120 a - f , when a channel 120 a - f is set to be output , the thruster 110 can flow fluid out of the mt 100 through that channel 120 a - f , and when a channel 120 a - f is set to be closed , no fluid can flow through that channel 120 a - f . to illustrate how the mt 100 works , channels 120 a and 120 f are set to be input , channels 120 b and 120 c output , and channels 120 d and 120 e are closed . in this case , the thruster 110 can flow fluid from channels 120 a and 120 f to channels 120 b and 120 c . there are many other possible flow configurations for the mt 100 . in general , a mt that has n channels can have 3 n different flow configurations . a single mt 100 can be used to drive a underwater vehicle in 3 - dimensional movement . for example , the mt 100 can be enclosed inside the underwater vehicle where the six channels 120 a - f of the mt 100 may be connected to thrusting ports or channels of the vehicle . for instance , channels 120 a and 120 b can be connected to the vertical thrusting port or channel of the vehicle so that the mt 100 can move the vehicle up or down by thrusting fluid flow from channel 120 a to channel 120 b or vice versa . channels 120 c and 120 d can be connected to the longitudinal thrusting port or channel of the vehicle so that the mt 100 can move the vehicle left or right by thrusting fluid flow from channel 120 c to channel 120 d or vice versa . channels 120 e and 120 f can be connected to the transverse thrusting port or channel so that the mt 100 can move the vehicle forward or backward by thrusting fluid flow from channel 120 e to channel 120 f or vice versa . fig1 ( b ) shows an implementation of a mt 150 . the mt 150 includes a single thruster 160 that has two ends 165 a , 165 b . the thruster 160 can propel fluid flow in a direction from thruster end 165 a to thruster end 165 b and in an opposite direction from thruster end 165 b to thruster end 165 a . one example of thrusters that may be used in a mt system is thruster sbt150a available from seabotix ( san diego , calif .). this thruster can provide 2 . 9 kgf thrust for 80 w . another example of thrusters that may be used in a mt system is integratedthrusters ™ available from tsl technology ( hampshire , england ). these thrusters range from 50 mm propellers to 300 mm 250 kgf thrust workhorses . the mt 150 also includes two connector assemblies 170 a , 170 b that are in fluid communication with the thruster 160 . connector assembly 170 a is connected to thruster end 165 a , and connector assembly 170 b is connected to thruster end 165 b . connector assembly 170 a has one set of three or more connectors or valves 175 a 1 - 5 , and connector assembly 170 b has another set of three or more connectors valves 175 b 1 - 5 . in fig1 ( b ), connectors 1 - 5 are numbered consecutively from left to right for each set of connectors . each connector 175 a 1 - 5 , 175 b 1 - 5 can be set to be open or closed . when a connector 175 a 1 - 5 , 175 b 1 - 5 is set to be open , fluid can flow through that connector 175 a 1 - 5 , 175 b 1 - 5 ; and when a connector 175 a 1 - 5 , 175 b 1 - 5 is set to be closed , no fluid can flow through that connector 175 a 1 - 5 , 175 b 1 - 5 . by setting the connectors 175 a 1 - 5 , 175 b 1 - 5 into different states , the mt 150 can thrust fluid flow from some connectors on one side of the thruster 160 to some connectors on the other side of the thruster 160 . for example , if connectors 175 a 2 and 175 a 4 are set to be open , connectors 175 b 2 and 175 b 4 open , and the rest of the connectors 175 a 1 , 175 a 3 , 175 a 5 , 175 b 1 , 175 b 3 , and 175 b 5 closed , the mt 150 can thrust fluid flow from connectors 175 a 2 and 175 a 4 to 175 b 2 and 175 b 4 by controlling the thruster 160 to propel fluid from thruster end 165 a to thruster end 165 b , or from connectors 175 b 2 and 175 b 4 to 175 a 2 and 175 a 4 by controlling the thruster 160 to propel fluid from thruster end 165 b to thruster end 165 a . the state selection of the connectors can be realized either by mechanical devices or electronic valves , such as the two - way solenoid valves available from kuhnway corporation ( taipei , taiwan ), depending on the speed and force requirements . fig1 ( c ) shows how a single mt 150 of fig1 ( b ) can provide various fluid flow configurations to achieve desired auv movements . as shown in fig1 ( c ), the mt 150 can reside inside an auv support shell or frame 190 that supports multiple thrusting ports and channels that are connected to respective connectors 175 a 1 - 5 and 175 b 1 - 5 at the two ends of the thruster 160 . the support shell or frame 190 can also be used to mount other components or modules to the auv , e . g ., an auv controller that controls the opening and closing of the connectors 175 a 1 - 5 and 175 b 1 - 5 and operations of the thruster 165 . this auv controller can be in wired or wireless communications with an external control device to carry out commands from the external control device . selective fluid flow through one or more of the thrusting ports or channels allows for desired movement of the auv . in general , the auv can have as many thrusting ports or channels as needed for its desired movement . for example , the auv can have one or more pairs of vertical thrusting ports or channels to provide up - down movement , and one or more pairs of port thrusting ports or channels and one or more pairs of starboard thrusting ports or channels to provide forward - backward movement when the port thrusting ports or channels and the starboard thrusting ports or channels run in the same direction and to provide spinning motion when the port thrusting ports or channels and the starboard thrusting ports or channels run in opposite directions . the auv can also one or more pair of vertical thrusting ports or channels to provide up - down movement , one or more pairs of longitudinal thrusting ports or channels to provide left - right movement , and one or more pairs of transverse thrusting ports or channels to provide forward - backward movement . for purpose of illustration , only four thrusting ports or channels 180 a - d are shown in fig1 ( c ). the thrusting ports or channels of the auv can be so shaped , positioned and / or arranged as to provide the desired auv movement . each thrusting port or channel can be connected to one or more connectors of the mt by one or more fluid conducting conduits . in fig1 ( c ), thrusting ports or channels 180 a - d are connected respectively to connectors 175 a 1 , 175 a 4 , 175 b 5 , 175 b 2 by fluid conducting conduits 185 a - d respectively . some or all other connectors can also be connected to one or more thrusting ports or channels . by setting the connectors to different states , the mt 150 can selectively flow fluid from some thrusting ports or channels to some other thrusting ports or channels or vice versa so as to move the auv in desired directions . a multiplex thruster can have many applications . as an example , the 10 - connector mt in fig1 ( b ) can be used to implement 3dof actuation of a sphere - shaped vehicle . to do so , the thrusting arrangement of such a vehicle 200 can be viewed as a configuration of six bi - directional channels 210 a - f shown in fig2 ( a ). channels 210 a and 210 b are aligned with the vertical axis of the sphere with channel 210 a positioned at north pole and 210 b positioned at south pole . channels 210 a and 210 b can provide vertical thrusting for the vehicle 200 . channels 210 c and 210 d are positioned at the port side of the sphere and perpendicular to the vertical axis of the sphere . channels 210 c and 210 d provides port thrusting for the vehicle 200 . channels 210 e and 210 f are positioned at the starboard side of the sphere and perpendicular to the vertical axis of the sphere . channels 210 e and 210 f provides starboard thrusting for the vehicle 200 . fig2 ( b ) shows the configuration of vertical , port and starboard thrustings in a sphere can provide three degrees of freedom movement ( up - down , forward - backward , and spin - left - right ) for a sphere - shaped vehicle . vertical thrusting 260 ( i . e ., thrusting along the vertical axis of the sphere ) can provide up or down movement of vehicle 250 when thrusting flow is downward or upward . port thrusting 262 ( i . e ., thrusting tangential to the port side of the sphere ) and starboard thrusting 264 ( i . e ., thrusting tangential to the starboard side of the sphere ) can provide forward - backward movement of vehicle 250 when both thrusting flow are backward or forward . port thrusting 262 and starboard thrusting 264 can also provide spinning left - right when port thrusting flow is forward and starboard thrusting flow is backward or vice versa . with the ability to spin , a sphere - shaped underwater vehicle can have a turning radius of less than 0 . 1 meter . this is an advantage over the torpedo - shaped underwater vehicle . by setting the six channels 210 a - f shown in fig2 ( a ) into different state combinations , the vehicle 200 can perform its desired 3dof movements . for example , if channel 210 a is set to be input and 210 b is output ( with all other channels 210 c - f closed ), then the vehicle 200 can move up . if channels 210 d and 210 f are inputs , and channels 210 c and 210 e are outputs ( with all other channels 210 a and 210 b closed ), then the vehicle 200 can move backward . if channels 210 c and 210 f are inputs , and channels 210 d and 210 e are outputs ( with all other channels 210 a and 210 b closed ), then the vehicle 200 can spin to the right . table 1 lists the channel states that are necessary for the desired 3dof movements for such a vehicle . the 10 - connector mt 150 shown in fig1 ( b ) can be used to realize the above state table . for example , the six channels 210 a - f in fig2 ( a ) can be connected to the connectors 175 a 1 - 5 , 175 a 1 - 5 in fig1 ( b ) as follows : fig3 ( a )-( c ) shows how the above connection works . consider the following situations : if connectors 175 a 1 and 175 b 1 are open and all others 175 a 2 - 5 , 175 b 2 - 5 are closed , then channels 210 a and 210 b will be connected ( fig3 a ), so the mt 150 can move the vehicle 300 up or down by thrusting fluid flow from connector 175 a 1 to connector 175 b 1 or vice versa . if connectors 175 a 2 , 175 b 4 , 175 b 3 , 175 b 5 are open and all others 175 a 1 , 175 a 3 , 175 a 5 , 175 b 1 , 175 b 2 , 175 b 4 are closed , then channels 210 c and 210 e will be on one side of the thruster and channels 210 d and 210 f on the other side ( fig3 b ), so the mt 150 can move the vehicle 300 forward or backward by thrusting fluid flow from connectors 175 a 2 , 175 a 4 to connectors 175 a 3 , 175 b 5 respectively or vice versa . if connector 175 a 3 , 175 a 4 , 175 b 2 , 175 b 5 are open and all others 175 a 1 , 175 a 2 , 175 a 5 , 175 b 1 , 175 b 3 , 175 b 4 are closed , then channels 210 c and 210 f will be on one side of the thruster and channels 210 d and 210 e on the other side ( fig3 c ), so the mt 150 can spin the vehicle 300 left or right by thrusting fluid flow from connectors 175 b 2 , 175 b 5 to connectors 175 a 3 , 175 a 4 respectively or vice versa . the above example shows only one of many possible connections between the channels 210 a - f and the connectors 175 a 1 - 5 , 175 b 1 - 5 . to illustrate , examples of other possible connections can include ( 1 ) 210 a - 175 a 1 , 210 b - 175 b 1 , 210 c - 175 a 2 , 210 d - 175 b 2 , 210 e - 175 a 3 , 210 f - 175 b 3 ; ( 2 ) 210 a - 175 a 3 , 210 b - 175 b 3 , 210 c - 175 a 4 , 210 d - 175 b 4 , 210 e - 175 a 5 , 210 f - 175 b 5 ; ( 3 ) 210 a - 175 a 1 & amp ; 175 b 1 , 210 b - 175 a 2 & amp ; 175 b 2 , 210 c - 175 a 3 & amp ; 175 b 3 , 210 d - 175 a 4 & amp ; 175 b 4 , 210 e - 175 a 5 , 210 f - 175 b 5 ; ( 4 ) 210 a - 175 a 1 , 210 - 175 b 1 , 210 c - 175 a 2 & amp ; 175 b 2 , 210 d - 175 a 3 & amp ; 175 b 3 , 210 e - 175 a 4 , 210 f - 175 b 4 ; and many more . the above example only uses eight out of the ten connectors of the mt . this is to show that a single mt can be used for multiple purposes simultaneously . the unused connectors , 175 a 5 and 175 b 4 , can be used for other purposes that may or may not be related to the actuation of vehicle . the above example also shows the possibility of real - time omni - directional control with high precisions . to do so , the number of channels in the vehicle can be increased to evenly distribute them in desired directions and a corresponding increase in the number of connectors in the mt if necessary . adjustable valves can also be used to precisely control the amount of flow in each connector in the mt . the present mt system can be used in various underwater vehicles or other devices that may require flexible , precise , and economic thruster systems that can be easy to control and capable of providing multiple degrees of freedom without utilizing a large number of separate thrusters . such underwater vehicles can be small , agile and less power - consuming . an example of a modularized system architecture that can be used in the auvs provided herein is shown in fig4 . the system architecture 400 can include modularized components ( or modules ) that provide subsystem functions and that can be easily exchanged or replaced . the modules can include one multiplex thruster 410 , one thruster controller 420 , one battery package 430 , one embedded computer 440 , one water sampler 450 , one underwater communication unit 460 , and five sensor modules 470 a - e that can host different types of sensors . the modules can be easily exchanged for fresh modules . this may reduce the in - field maintenance time and increase the versatility of auvs for multifunctional usage . in some embodiments , the battery package 430 of the auvs provided herein can include smart batteries for high - performance power supply . an example of such batteries is n12040hd24 smart li ion battery available from inspired energy corporation ( newberry , fla .). a n12040hd24 battery is 10 . 8v and 7 . 2 ahr . in some embodiments , the auvs can use 12 such batteries ( 6 parallel of 2 serial ) to make a package of 21v and 28 . 8 ahr . such a package can be more than sufficient for up to 10 hours of continuous operation in open water . in some embodiments , the sensor modules 470 a - e of the auvs provided herein can host up to five different types of sensors as shown in the system diagram in fig4 . each sensor module 470 a - e can host a different type of sensor at different time . sensors suitable for use in the auvs can include depth , altimeter , camera , chlorophyll , dissolved oxygen , ctd , ph , light , turbidity , photosynthetic active radiation ( par ), and more . in some embodiments , the auvs can use a pressure sensor to autonomously measure and maintain a fixed depth from the surface . an example of suitable pressure sensors is the fm60 pressure sensor available from bts fluid measurement ( england ). the fm60 sensor has a standard usb interface so that the sensor can be plugged into a pc usb port or hub . in some embodiments , the auvs can use an altimeter to autonomously measure and maintain a fixed distance to the sea bottom . an example of suitable altimeters is tritech pa500 bathy altimeter available from ashtead technology rentals . the pa500 altimeter is accurate and has a standard rs232 interface . the altimeter can be mounted at the bottom of the auvs . an altimeter , together with a depth sensor , may provide sufficient measurements for the auvs to autonomously undulate near the bottom and near the surface , where much of the biological activity is taking place . in some embodiments , the auvs can use other environmental sensors for data acquisition . for example , the auvs can use a sensor to measure conductivity , temperature , and pressure . an example of such sensors is the micro - 3 ctd sensor available from applied microsystems ( sidney , b . c . canada ). the micro - 3 package has rs - 232 logging capability and can integrate with up to six other sensors such as ph , dissolved oxygen , turbidity , and chlorophyll . in some embodiments , the water sampler 450 of the auvs provided herein can be used for autonomous water sampling . an example of suitable water samplers is the carousel water sampler sbe 32 available from sea - bird electronics ( bellevue , wash .) or a similar device with a smaller size . the sbe water sampler includes a bottle with an electric valve that can be controlled by the embedded computer inside the auv system . in some embodiments , the underwater wireless communication and remote control unit 460 of the auvs provided herein can include a whoi micro - modem to communicate with an underwater transducer that is attached to a floating surface station such as a boat or a buoy . an example of suitable micro - modems is tms320c5416 dsp available from texas instruments ( dallas , tex .). the tms320c5416 dsp modem has a transmit power of 10 w that can match to single omni - directional ceramic transducer , and a receive power of 80 mw , while detecting or decoding a low - rate fsk packet . the tms320c5416 dsp modem has a communication data rate of 80 - 5400 bps . the micro - modem can be installed inside the auvs and connected to the computer in the auvs . the corresponding transducer attached to the surface station can be connected to a portable computer operated by a human operator . when the auvs are on or near the surface , the auvs can communicate with the base station with a long - range radio modem and a short - range wireless ethernet . in some embodiments , the radio modem can be hydralink ml available from ocean science ( oceanside , calif .). in some embodiments , the wireless ethernet can be aironet 350 pcmcia available from cisco ( san jose , calif .). together , the radio modem and wireless ethernet can enable the auvs to be remotely accessed for control , programming , testing , tracking , and data downloading . in some embodiments , the auvs provided herein can have the capability of automatically resurfacing themselves in case of unexpected fault or emergency so that they can be retrieved easily . for this capability , the auvs can use an electromagnet to hold up a small weight that makes the total system mutually buoyant in seawater . under normal circumstances , the electromagnet can be constantly activated under the supervision of a watchdog timer inside the control computer of the auvs , so the auvs stay mutually buoyant . in case of emergency when the computer is dead or stalled , the watchdog can time out and deactivate the electromagnet . this may cause the auvs to drop the attached weight and become positively buoyant , thus float up to the surface . once on the surface of the water , the auvs can activate its radio modem ( e . g ., hydralink ml ) to emit a radio beacon so that the auvs can be located and retrieved within a range of a certain radius ( e . g ., 20 miles ). in some embodiments , the controller 420 of the auvs provided herein can be used to control the operation of the multiplex - thruster 410 . in some implementations , the auvs can use a pololu 30 - amp motor driver board available from pololu robotics and electronics ( las vegas , nev .) with an atmega128 microcontroller available from atmel ( san jose , calif .) as a compact solution to control the mt . the pololu driver board uses the vnh3sp30 motor driver integrated circuit available from stmicroelectronics ( geneva , switzerland ) and incorporates various components for typical applications , including pull - up and current - limiting resistors and a fet for reverse battery protection . software can be developed for the motor controller using atmega128 and feedback can be added to this controller . in some embodiments , the embedded computer 440 of the auvs provided herein can be used as the on - board controller for programming and executing autonomous behaviors , data acquisition and storage , communication , and interface with human operator . in some implementations , the auvs can use jrex - pm embedded 3 . 5 ″ sbc single - board computer available from diamond point international ( england ). the jrex - pm embedded computer includes 10 / 100 base - t ethernet , crt & amp ; lcd support via jili , standard pc i / o , one rs232 , and two usb2 . the embedded computer can be stacked with many other extension boards for more i / o ports and more communication capability . two useful add - on boards are jflex - serialgpio1 and jflex - communicationl . the first board enables multicom - communication , gpio or can - bus driven applications , and provides more interfaces of 3xrs232 ( or 3xttl ) and 1xrs422 / 485 . the second board includes 3xlan , 4xusb , and firewire . in some embodiments , the auvs provided herein can include an underwater color camera for navigation and data acquisition . such an underwater vision system may allow for autonomous behaviors . for example , the auvs can autonomously follow a diver who wears a red vest . the auvs can autonomously track the red color underwater and change their movements to follow the diver . in the auvs provided herein , all the mechanical and electronics hardware described above can be integrated into a single system . in some embodiments , the auvs provided herein can have a sphere shell in which all modules of the modular system architecture and the multiplex - thruster reside . the sphere can be free - flooded to eliminate the pressure difference in and out the auvs for maximum depth and easy in - field servicing and maintenance . this can maximize the payload volume without increasing the system &# 39 ; s overall weight . the auvs can be mutually buoyant in ocean water and the center of mass can be kept low near the bottom of the sphere so that the auvs can be balanced to keep the upright position along the vertical axis . the sphere shape can prevent the auvs from tangling with underwater plants and other materials . the sphere can also provide open hatches for maintenance . in some implementations , the auvs provided herein can be constructed as sphere - shaped auvs that may have a diameter of less than 1 meter , a total weight of no greater than 15 kg , and a turning radius of less than 0 . 1 meter . the auvs can maintain , change , or undulate its depth autonomously or under remote control ; host five types of sensor ; run for 4 to 10 hours without changing batteries ; and sample water when a sensor of choice detects an abnormal signal . all components can be exchangeable and replaceable for easy maintenance and reconfiguration in the filed . in some embodiments , the auvs provided herein can have programs for data acquisition in field , user - friendly interfaces for downloading software and data , and matlab for 3d data visualization and statistical analysis with user - specified parameters and thresholds . all software for autonomous behaviors , remote control , sensing , logging , and analysis can be modularized so that they can be easily rebooted , replaced , or updated . software for emergency recovery can be developed . in some implementations , the real - time software for the auvs &# 39 ; autonomous can include actuator drivers including driver for actuating the thruster and driver for sampling water ; sensor drivers including driver for reading current value from a sensor ; data logging including programs that start and stop continuous data acquisition from a sensor and store the data acquired in a file ; low - level vehicle controller implementation including programs that control auvs &# 39 ; 3odf movements ; higher - level controller management or autonomous behaviors ; mission level control ; and fault and emergency management . in some implementations , the real - time software for the auvs &# 39 ; autonomous behaviors can include a program that moves the auvs to the depth and maintain the auvs at that depth for a duration using the feedback from a depth sensor . the software can also include a program that moves the auvs to an altitude from the bottom and maintain the auvs at that altitude for a duration using the feedback from an altimeter . in some implementations , the real - time autonomous behaviors can run in parallel and be composed into more complex , mission - level behaviors . for example , consider a behavior that undulates the auvs between near surface and near bottom for every 30 minutes until 5 pm , and then moves the auvs to the surface and wait for pick up . when this undulating behavior is running , the auvs may also execute in parallel other sensor behaviors . for instance , one behavior can be to measure dissolved oxygen near the surface , another behavior can be to measure ctd near the bottom , and a third behavior can be to sample water when ph is higher than a threshold . the measured data can be stored in separate files , and they can be displayed and analyzed later by other on - board software , or downloaded to a remote computer for analysis . the sensor behaviors can be continuous for the entire mission , while the water sampling can be done only once . this shows the diversity of possible behaviors . in some implementations , the software for fault and emergency management can be another high - level behavior . this behavior can activate the electromagnet for the attached weight when a waterdog timer is not expired . under normal circumstances , the watchdog can be periodically renewed by the computer when it is alive . in case of emergency , the waterdog would not be renewed and the emergency behavior can eventually deactivate the electromagnet to drop the attached weight , causing the auvs to float up to the surface . in some implementations , software for communication with the remote control station can be an interrupt - driven behavior . this behavior can wake up every time there is a command received by the radio or the acoustic modem and can execute the received command immediately . a remote command can be a name of a behavior , such as forward , back , left , right , up , down , staydepth , or stayaltitude . a remote command can have a priority that is higher than any of the autonomous behaviors and this can ensure the immediate response of the auvs and provide a mechanism for an adjustable autonomy . using this mechanism , the auvs can be remotely controlled for supervised behaviors . for example , the auvs can be remotely controlled to go to a target area , before they start their own autonomous behaviors . in some implementations , software for remote programming can be the set of standard protocols such as “ telnet ,” “ rlogin ,” “ xterm ,” or others . these remote protocols may allow a remote operator to login on the computer inside the auvs and perform remote operations such as creating or editing programs , compiling programs , starting / stopping behaviors , or downloading data . a remote operator can also visualize the data without downloading in a x window environment . in some implementations , the cots software matlab can be used as the main tool for data visualization and data analysis . in some implementations , software for operator interface can be developed for the remote control station . this software may allow the operator to query the auvs &# 39 ; current status and sensor reading , as well as send commands to the auvs to control their behaviors . the status information can include the depth , altitude , voltage of batteries , and status of each thruster or mt channels . the remote commands can include the auvs &# 39 ; behaviors described above . all the components of the auvs described above can be economically modularized to perform plug - and - play and achieve reconfiguration , multifunction , easy maintenance , and low cost . in various implementations , the auvs provided herein can maintain a fixed depth near surface or a fixed altitude near bottom for , e . g ., 4 to 10 hours ; undulate near surface and near bottom for a fixed frequency for , e . g ., 4 to 10 hours ; acquire data continuously and simultaneously on one , two , or three sensors for , e . g ., 4 hours ; sample water when triggered by a sensor or a clock ; remote control underwater behaviors ( e . g ., go to a target area in 3d space ) from a laptop ; remote program a simple behavior when the auvs are on or near surface ; remote download data and perform 3d visualization and statistical analysis ; and recover from an emergency ( e . g ., power lost or system crash ) by automatic resurfacing . the auvs provided herein can have a precision hovering ability and can be dynamically reconfigured to integrate with multiple underwater sensors and can be easy to deploy , operate , maintain , and adapt to a variety of underwater applications for environmental monitor and protection , offshore oil industry , aquaculture , and other ocean resource exploration and utilization . for example , the auvs can be used for offshore oil platform inspection if an underwater color camera is integrated for visual inspection and detecting problem situations in time . the auvs can also be used for offshore aquaculture as the auvs &# 39 ; reconfigurability can provide an economic solution to the need for frequent underwater operations with different sensors , manipulators , and actuators . the auvs can further be used for underwater inspection at seaports for security since the auvs can be easily tailored to perform periodic patrol and inspect some critical underwater structures in the port , as well as the incoming ships below the waterline . the auvs can additionally be used for ship cleaning because the auvs can be attached to a small cleaning device and perform the ship cleaning service for both government and private agencies . this document provides various examples of auvs where the multiplex thruster and modular architecture described herein can be utilized . such multiplex thruster and modular architecture can also be utilized in other types of vehicles or devices including surface vehicles . while this document contains many specifics , these should not be construed as limitations on the scope of an invention or of what may be claimed , but rather as descriptions of features specific to particular embodiments of the invention . certain features that are described in this document in the context of separate embodiments can also be implemented in combination in a single embodiment . conversely , various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination . moreover , although features may be described above as acting in certain combinations and even initially claimed as such , one or more features from a claimed combination can in some cases be excised from the combination , and the claimed combination may be directed to a sub combination or a variation of a subcombination .