Kenneth K. K. Ku

A Novel Actuator for Underwater Robots

Pneumatic muscles have been used for a number of years as actuators in robotic systems, usually for those that mimic human actions. They are most commonly used in systems designed to aid physically handicapped people. This feasibility study reports mechanical testing and modeling results for the Shadowtrade artificial muscle pneumatic actuator working in both air and underwater. The static and dynamic tension-contraction measurements were recorded through both the force and contraction relationship test and the dynamic response and time relationship test. A model of the properties of the muscle working in water was derived from the measurements of the tests that can be considered for its feasibility for use in undersea robotics.

Exploration for novel uses of air muscles as hydraulic muscles for underwater actuator

Since a dextrous robotic arm has been designed for use on land and in space, further development could be its use underwater for performing delicate tasks, just like a human hand, for operations such as picking up small or irregular size objects. Hitherto there has been no report on studies on modelling and control of rubber artificial muscles in hydraulic mode. The feasibility of developing these actuators using water as the articulating medium for underwater robots was therefore investigated by studying the properties of the hydraulic rubber muscle actuator. The rubber muscles used in the present tests were developed by the Shadowtrade Robot Co. Ltd. for installing in dextrous robotic arms. The objectives of this study were, thus, first, to define the kinematics of the hydraulic muscle. A test set up was designed to obtained contraction, force and response time values based on reference of a model defined for the rubber muscle when used in air. Second, to compare the performance of the rubber muscle in air and underwater using the test set up and thus third, to obtain a modelling of the hydraulic rubber muscle which was derived from that of the air rubber muscle.

Application of a real-time underwater surveillance camera in monitoring of fish assemblages on a shallow coral communities in a marine park

An underwater surveillance camera has been designed for monitoring fish species activity on an inshore coral reef in a Marine Park in Hong Kong. The system consisted of a high-resolution camera. It was connected to the shore base station via a fibre-optic cable with power conductors. The camera could record video on a DVD recorder with hard disk in real time. The system was designed to be used for long periods of time up to three months continuously without maintainence. It was used to monitor changes in coral fish abundance with respect to time of day and among months. The present results thus showed two major behavioural patterns of coral fish in Hoi Ha Wan. The first is the diurnal activities as most fish species are active during the daylight rather than at night. Both mean number of species and fish density showed an increase in daylight and a decrease at night. The second was the seasonal migratory pattern. A seasonal variation of fish abundance on a subtropical reef was recorded with water temperature changes from 29degC in summer to 17degC in winter. Mean maximum number of species during daylight in warmer months was ~10-12 while that in colder months decreased to 2-3.

Real-time monitoring of fish activity on an inshore coral reef

This paper describes an underwater camera and instrumentation system for monitoring fish species activity on an inshore coral reef in a Marine Park in Hong Kong. The system consists of a high-resolution pan, tilt and zoom camera with associated instrumentation package for measuring the local environment, including dissolved oxygen, temperature, pressure, salinity and ambient light conditions. It is connected to the shore base station via a fibre-optic cable with power conductors. The system is designed to be used for long periods of time, continuously. The first period chosen was for 100 days during the coral spawning season from June to August 2004. The system has also been used regularly for 2-3 weeks at a time to monitor changes in fish behaviour in different climatic conditions. Results from the initial experiment show that fish species activity is generally markedly different from that recorded by human divers. There is also some correlation between species, time of day, and climatic and environmental conditions - correlations that have not been reported before. The paper will give details of the results of the observations, as well as technical details of the system. It will also refer to an associated project using an ROV for transect measurements on the reef, data from which has a bearing on the subject of the paper.

An underwater camera for security and recreational use

The objective of this project was to design an underwater camera and instrumentation system that could be used to detect and follow moving objects, and be able to be deployed at a depth of up to 100 m for an extended period of time. This was achieved by using a pan, tilt and zoom high resolution camera connected to a base station via a powered fibre optic cable. The camera was successfully deployed for 100 days continuously, recording video on to a DVD recorder in real time.

A low-cost, three-dimensional and real-time marine environment monitoring system, Databuoy with connection to the internet

The monitoring of environmental parameters of Hong Kong waters has usually been achieved by accumulating collected data from single point sources just below the sea surface, once or twice a month by the Hong Kong Environmental Protection Department. There has also been some experimentation involving data loggers placed on the seabed. However all of the above data collecting methods produce only historical datasets months or even years before such data is processed and made available. For a timely response to changing environmental conditions, it will be important that the data is received and processed in real-time if there is going to be a quick remedial action to changes. City University has developed a low-cost system, Databuoy, for collecting basic marine environmental parameters. This system is equipped with up to 10 sensor packs suspended in different depths in the water column under a floating buoy. Each sensor pack measures a physical parameter such as temperature, salinity or light intensity. All sensors, under each buoy, are connected to a single multiplexer that is in turn connected to a PC via a simple MODEM connection. The DataBuoy I system consisted of a single buoy with a string of sensors underneath it. The more advanced configuration, DataBuoy II, connect several nearby DataBuoys together for a 3-D representation of the measured parameters to be constructed from the data. The system has four basic components, that is, the supporting structure, the sensor packs and two levels of signal multiplexing and transmission units. Connection to the internet and other systems are then possible via this connection. The application for this type of system extends beyond the collection of field data. Real time water parameters exceeding warnings, data processing involving the rate of change of parameters and the control of marine area polluting equipment or discharges via closed loop feedback connections are all possible.

An Underwater Camera and Instrumentation System for Monitoring the Undersea Environment

It is impossible to use human divers carrying underwater cameras, with limited battery and recording capacity, to monitor marine life and coral behaviour, and to record for 24 hours a day over three months. As a result, the use of an instrumentation platform, remotely controlling a deployed underwater camera systems and sensors, is an alternative approach that can provide long-time monitoring and image recording.

Establishment of a three dimensional, real-time marine environment monitoring system, DataBuoy™ I, in the Hoi Ha Wan Marine Park, Hong Kong, with connection to the internet

DataBuoyTM I, a three dimensional, real-time marine environment monitoring system with connection to the internet, has been developed by the Department of Electronic Engineering, City University of Hong Kong (CityU). This equipment can multiplex up to five sensors placed at different depths in the water column for monitoring of temperature, salinity and light intensity. It was installed on a site in the Hoi Ha Wan Marine Park between June and July 2006. Data collected was transferred to the CityU Marine Laboratory at the Hoi Ha Wan Marine Life Centre. Preliminary results showed that Hoi Ha Wan has had a wide salinity variation (9 ppt to 33 ppt) among sites and within two days. During that data collecting period, the water temperature recorded at 30 cm from sea surface reached a maximum of 33.5degC, while that at 7 m deep was 25.5degC. The DataBuoyTM, therefore, could detect the hypoxia in shallow water caused by low salinity at the water surface whereas the deeper sensors could detect the thermocline associated with the hypoxia in deeper water, if any. Future work involves the setting up of a DataBuoyTM II network to monitor three areas in Hoi Ha Wan. The data could be collected every few seconds and consolidated in a computer server located in the CityU Marine Laboratory. It would be formatted for display at the Marine Life Centre for visitors " information on a mimic panel and on the CityUs WWW site. This would allow world wide access to the information, making it available on line to the Government Authority, schools and the general public for information and research purposes.

Towards a 3-dimensional model of Hoi Ha Wan Marine Park, Hong Kong

Hong Kong has a unique marine environment. The intermixing of low salinity water, from the nearby Pearl River estuary outflows, with sea water from three different marine currents producing a variety of varying marine environmental conditions at different times of the year. Hoi Ha Wan is a shallow, small, enclosed bay in the north-east corner of Hong Kong. It has been designated a Marine Park primarily because it contains significant examples of the incipient reefal coral systems that are scattered throughout the local waters. A key interesting feature of this marine community is its ability to tolerate a large variation of temperature and salinity during each year. It is therefore of interest to measure the changes and the rates of changes in key environmental parameters and try to relate these to the actual condition of the marine life in the key areas. The authors have previously reported the development of the Databuoy I system. This paper discusses the upgrades to the original systems, (to DataBuoy II) and reports preliminary results from the current project, which is to develop a 3-dimensional model of the bay, using real-time data from an array of sensors attached to the Databuoys.

Modelling pneumatic muscles as hydraulic muscles for use as an underwater actuator

Pneumatic muscles have been used for a number of years as actuators in robotic systems, usually for those that mimic human actions. They are most commonly used in systems designed to aid physically handicapped people. Air muscles consist of an inflatable tube, usually neoprene rubber that is constrained by a nylon mesh. When compressed air is passed into the muscle, which is blocked at one end, the tube inflates, but the action of the enclosing mesh forces the tube to shorten. The resultant force is sued as a linear actuator.