Department Publications

In this work, we propose a framework that can provide performance metrics with regards to the usability of an assistive device designed to provide visual servoing of a reaching task performed by a visually impaired individual. The framework provides a model and methodology from which performance metrics can be synthesized based on robotic manipular kinematics and an adaptation of Fitts' law for reaching task motions in a 3D environment. The purpose of which is to facilitate an understanding of how well the system's design accommodates the user's natural movement style when performing the reaching task. Use of advances in visual tracking techniques employing scale, view-point, and illumination invariant features are incorporated to allow for a further decoupling of the feature space from the joint-level control space.

A new type of force-position compliant control is proposed, where hyperbolic tangent function is used to dynamically adjust the gain of the position feedback loop so that to control the contact force safely and according to a given pattern. The proposed compliant controller uses a high gain in the position control loop when the robotic device is in free space motion, and as and when it comes into contact with the environment, the gain of the position loop is lowered according to the roll-off of inverse tangent function. The controller is tunable with only one parametery, and is capable of mimicking a wide range of force control behaviors. In this paper we apply the proposed controller to mimic human compliant motion in gripping and lifting objects. And, we have verified that the human compliant behavior can be satisfactorily realized by the proposed compliant controller.

The optimum distribution of treated pipe-borne water is a critical requirement in countries which have a deficit production in comparison with the demand. However, in 3rd world countries, it is not feasible to design the entire water distribution network as a whole, to enable near-optimized delivery, due to economic constraints. The current practice in such countries is to operate the nodes of the water distribution network, such as pump houses and water towers, in isolation, based on ad hoc criteria. Improper co-ordination of these nodes leads to wastage and inefficiencies in the utilization of the scarce resource of treated water. Hence the challenge lies in improving the water distribution process via a network that has not been inherently designed to support optimum distribution. The proposed system presents a solution to this predicament by centrally monitoring and controlling the functionality of these points of …

The vision of this research paper is that the mobile phone is aware of its user's motion state and surroundings and modifies its behaviour especially the characteristics of Location-Based-Services based on this information. In the research it is implemented, and evaluated a methodology which can identify individual user, states. This learning is expected to occur online and not expected the requirement of any external supervision. The proposed system relies on hidden markov modelling and Log Likelihood Method. The implementation of the methodology is performed by first training the hidden markov model for the required number of states by an intended network trace. The log likelihood value of the data for each hidden markov model in the set is computed and the motion state is identified by choosing the hidden markov model that produced the highest value. The results of simulations carried out in WCDMA environment indicate that the proposed method is able to assist to create a meaningful user context model at various propagation conditions defined by both 3rd Generation Partnership Project (3GPP) and Wireless World Initiative New Radio (WINNER) propagation scenarios while only requiring a network trace without having an integrated sensor onboard cellular phone or any other wearable sensor device.

The paper describes the design and development of an alarm device that can disseminate disaster early warnings to threatened communities over the GSM network. The device is capable of generating audible, high-volume alarms, flashlights and turning on an in-built radio in response to a warning message from an authorized entity via GSM's short message service (SMS) or cell broadcast (CB). The design of the device follows international guidelines on emergency communications, such as the ability to reach a large number of people very fast, awaken sleeping communities, and be able to acknowledge warning messages. The alarm has been designed as a last-mile technology in a larger disaster early warning network (DEWN). It is intended to be place in selected locations such as police stations, places of religious places and community centres. Thus the DEWN system and thus the alarm device presents a …

A novel method of individual level adaptive mutation rate control called the rank-scaled mutation rate for genetic algorithms is introduced. The rank-scaled mutation rate controlled genetic algorithm varies the mutation parameters based on the rank of each individual within the population. Thereby the distribution of the fitness of the papulation is taken into consideration in forming the new mutation rates. The best fit mutate at the lowest rate and the least fit mutate at the highest rate. The complexity of the algorithm is of the order of an individual adaptation scheme and is lower than that of a self-adaptation scheme. The proposed algorithm is tested on two common problems, namely, numerical optimization of a function and the traveling salesman problem. The results show that the proposed algorithm outperforms both the fixed and deterministic mutation rate schemes. It is best suited for problems with several local optimum solutions without a high demand for excessive mutation rates.

Detection of straight lines in an image is a fundamental requirement for many applications in computer vision. We formulate the straight line detection task as an energy minimization problem. This formulation helps the detection of lines in a global manner in contrast to the local detection methods used in conventional algorithms. As a result the proposed straight line detection algorithm can handle virtually co-located straight lines, slightly curved lines and edge linking in a unified manner. In addition, due to its the global nature, the algorithm is not deceived by image noise giving rise to spurious line segments. Therefore, the proposed algorithm can robustly detect straight lines. The main component of the algorithm is formulating the energy to be minimized. The contribution to this energy function is less at a pixel which is a good candidate to be a member of an existing line segment depending on the directional …

Map building and obstacle detection are basic tasks in mobile robot navigation. In this paper we present a probability based solution for map building which utilizes time of flight information from an ultrasonic sensor. In contrast to most of the available map building systems, this uses a single ultrasonic sensor, mounted on a rotating shaft. Discrete sonar observations taken at regular time intervals, by rotating the shaft in small step angles are incrementally merged into partial planes to produce a realistic representation of environment that is amenable to sonar localization. Readings of close proximity are averaged to suppress the transient errors and the results are further refined by using the sonar probability model to fill an occupancy grid and Bayesian combination for the purpose of data fusion. Experimental results obtained in a real indoor environment are presented to verify the validity of our algorithm.

In this paper, a semiautonomous low-cost wheelchair robot to supplement impaired mobility of handicapped or elderly people is presented. The motion of the wheelchair is controlled by the joystick and the sonar sensor in such a manner that the sonar sensor has higher priority than joystick in normal conditions. The wheelchair uses two permanent magnet DC motors which are differentially driven using pulse width modulation (PWM) control signals. The motors drive the worm to drive the wheelchair. The semiautonomous wheelchair is equipped with four ultrasonic range finders in the front, one at the back to avoid the obstacles in its path and another one near the foot rest to detect steps. The system totally uses six ultrasonic sensors. The semiautonomous wheelchair was successfully tested under various conditions and satisfactory results were obtained.

Monocular vision based robot navigation requires feature tracking for localization. In this paper we present a tracking system using discriminative features as well as less discriminative features. Discriminative features such as SIFT are easily tracked and useful to obtain the initial estimates of the transforms such as affinities and homographies. On the other hand less discriminative features such as Harris corners and manually selected features are not easily tracked in a subsequent frame due to problems in matching. We use SIFT features to obtain the the estimates of the planar homographies representing the motion of the major planar structures in the scene. Planar structure assumption is valid for indoor and architectural scenes. The combination of discriminative and less discriminative feature are tracked using the prediction by these homographies. Then normalized cross correlation matching is used to find the …

Industrial robot manipulators are used in various applications in order to achieve fast, precise, and quality production. In pick-and-place operations such as part handling, assembly, etc., the end-effector of the manipulator has to travel between two specific points in the workspace, and the path it takes in between is of no concern. In trajectory tracking applications such as welding, cutting, painting, etc., the end-effector has to follow a specific trajectory in 3-space as closely as possible, while maintaining rated velocity as much as possible (Munasinghe, 2001). In the latter case, planning the trajectory can be complex when there are constraints on the end-effector velocity, joint acceleration, and trajectory error. Trajectories planned without proper consideration to these constraints often result in poor performance such as trajectory overshoots, end-effector deviations from the planned trajectory, and undue velocity fluctuations (Nakamura, et. al., 2000). Performance could be even more deteriorated especially at sharp corners in the Cartesian trajectory (Nakamura, 20001). Lot of trajectory planning algorithms have been proposed so far starting from simple Cartesian path control (Paul, 1979) to time optimized trajectories (Shin, 1985). However, the industrial systems experience difficulties accommodating most of these methods because of at least two specific reasons; 1) These techniques often require hardware changes in the existing setup and the manufacturing process has to be interrupted for system reconfigurations, which usually takes a longer period of time, and 2) Many of these methods often consider only one constraint, and often they pay less …

An electroencephalogram (EEG) instrument has been successfully developed and tested for capturing, visualizing and recording brain activity using both active and passive electrodes. The key idea is to capture a noise free composite brain wave and separate out its constituent components, namely delta, theta, alpha, beta and gamma. The system consists of three functional parts including EEG signal capturing, Digitizing and wireless transmission and PC end software for visualizing and post processing. EEG signal capturing part consists of electrodes, amplification circuit for each channel and Right Leg Driver circuit to eliminate 50 Hz power line noise. The digital band pass filters and the 50 Hz notch filter which confiscates any residual noise components are built in the PC software. Battery power and wireless communication gives the sovereignty to the user to move around with the system while being monitored …

An autonomous mobile robot is an intelligent agent which explores an unknown environment with minimal human intervention. Building a relative map which describes the spatial model of the environment is essential for exploration by such a robot. Recent advances for robot navigation motivate mapping algorithms to evolve into simultaneous localization and map-building (SLAM). Initial uncertainty is one of the key factors in SLAM. An update scheme of the feature initialization in monocular vision based SLAM will be briefly introduced, which is within a detailed implementation of feature detection and matching, and 3-D reconstruction by multiple view geometry (MVG) within extended Kalman filter (EKF) framework. Experiments clearly show that the proposed scheme can maximize the optimization capacity of EKF.

Managing data related to Tsunami damage, and providing sufficient detailed information to interested parties in the reconstruction and recovery process is a challenge faced by the National Data Center, Sri Lanka. The paper proposes a Web-based GIS system to assist the post - Tsunami recovery process. The data components needed to provide timely information for decision makers were identified from the ambiguous subject domain of the massive-scaled disaster. It facilitates the user to access interactive maps and query information through the maps via a standard Web browser. All tools used are free and open source software which makes the system affordable to a developing country such as Sri Lanka. The Hambantota district was selected for a pilot-scale implementation of the proposed system.

This paper describes an optimal method of inserting new frames or recovering missing frames in a video sequence. The method is based on an optimization scheme using graph-cuts that finds the 'optimal' frames to be inserted in between two given frames. The core problem is a typical visual correspondence problem between pixels in two or more frames and having formulated the appropriate energy, graph-cuts can be used for optimization. The two frames are assumed to be 'close' and the motion of the objects is small. The motion is seen as a set of two dimensional disparities, and the graph-cuts based optimization is able to find these. Once the disparities are found, an intermediate frame can be trivially placed at an arbitrary position in between the two original frames. The advantage of using graph-cuts instead of the typical techniques used in calculating optical flow lies in the global nature of the graph-cuts …

This paper presents a coherent demodulation scheme that reduces the multiple-access interference (MAI) considerably in a band-limited direct-sequence code-division multiple-access system. The despreading signal is obtained from a combination of the conventional despreading signal and its weighted early and late versions that are used in the delay-locked loop (DLL). It is shown that with appropriate choice of the weighting parameter of the early-late signals of the DLL, the signal-to-interference-plus-noise ratio of the decision variable is increased, which leads to improvement in the bit-error performance and hence the potential increase in the system capacity by about 25%. The analyses are performed in the frequency domain. The effect of imperfect synchronization on the system performance is also analyzed.

The paper describes a system to automate the monitoring and recording of rainfall using cellular network infrastructure. The paper describes the hardware and the software components and the data communication aspects of the design, and their integration as a complete system. Ancient Sri Lanka had been proud for centuries, of a very successful agricultural economy. Today, even though Agriculture still plays a key role in the Sri Lankan Economy, the agricultural sector has failed to keep up with the adoption of advancing technology and has thus fallen behind many other developing nations. Weather information such as rainfall is critical for successful agricultural activities. Unfortunately present methods of monitoring such information utilize manual observation and recording of data which is highly error-prone. Automation of these monitoring methods can not only increase the reliability, but also improve the timely availability of data, and hence contribute significantly to the betterment of agriculture in day-to-day activities as well as to long-term planning. The system consists of rain gauges with wireless interfaces and a central station. The rainfall information is transferred via SMS (Short Message Service) messages to the central station via a GSM cellular network. The information is received in a database at the central station and can be accessed via the Internet, and the data analyzed.

This paper describes a baby sitting robot system, which has the capabilities of baby tracking , cry signal processing, map building and obstacle avoidance, path planning, entertain the baby or alarm the guardian if any defined anomalies found and voice interaction. For that purpose, the baby sitting robot system has a capability to track and follow the baby with obstacle avoidance. It is also potential enough to identify when the baby cries, or reach near to any defined anomalies. Further more it provides a convenient voice interface for easy usage and various entertainment services for the baby. Rather than just notify the parents that the baby is approaching anomalies, it will try to prevent it from reaching the anomalies by either blocking or distracting with music. In this paper, the overall system is introduced and the detailed subsystems and functions are presented. Baby tracking, cry detection and step detection have …

This paper presents our approach in building an image guided navigational tool for neurosurgeons. The paper emphasizes critical methods which we have implemented within the main modules of the system, namely physical space model, calibrated frame and model transformation, MRI space model and the GUI. The surgeon is provided with special tools which contain markers which are detected by cameras to compute the real time positions of the tool tip. Special plastic markers are attached to the patient's head for the registration between two sets of coordinate systems. We were able to obtain satisfactory accuracy when equipped with low quality web cameras. Our GUI provides a modeled three-dimensional viewing of the patients head with the capability of rotating around fixed axes.

In this paper the design and implementation of a camera platform that can mimic the neck and the eye movements of humans is presented. The camera platform is intended for active vision applications. It has seven mechanical degrees of freedom corresponding to the degrees of freedom of the human visual system

The advent of low-cost, photo-quality inkjet printers has raised the need for an objective means of determining print quality that is consistent with what the end-user perceives. High-level quality metrics have been specified in the International Association for Standardization/International Electrotechnical Commission (ISO/IEC) guidelines on hardcopy print assessment [1]. These guidelines include metrics for four distinct categories of printed areas: line and character metrics, solid fill metrics, tint solid metrics, and background field metrics. Other metrics that enable the quantification of performance aspects relevant to inkjet printers have also been proposed. These aspects include color registration, color consistency, modulation transfer function (MTF), text quality, sharpness [2], dot quality, and line quality [3, 4]. Multiple efforts have been made to automate the process of image quality assessment both during product …

We demonstrate a powerful technique for detecting weak atomic or molecular transitions that is based on homodyning two atomic transition amplitudes. The scheme is tested on a weak Stark-induced transition in cesium by exciting its ground 6s^ 2S 1/2 state to the 8s^ 2S 1/2 excited state by a 411 nm laser field. The strong local oscillator signal is a two-photon transition excited by an 822 nm laser field that connects the same ground and exited states. The Stark-induced transition can be regulated by controlling a DC field across a Cs cell. The simultaneous excitation of the two pathways results in a quantum interference that can be controlled by phase modulating either of the driving laser fields. The change in the relative phase between the laser fields results in a change in the relative phase between the transition amplitudes of the two paths. Thus, phase modulating one of the beams gives rise to an amplitude …

A data-driven adaptive neurofuzzy controller is presented for the water-level control of U-tube steam generators in nuclear power plants. This neurofuzzy controller is capable of learning the control action principles from the data obtained using other methods of automatic or manual control. There are four inputs in the neurofuzzy system, yet only eighty fuzzy rules involved. Therefore, the fuzzy system is versatile and moderately compact. The versatility is due to the higher input space dimension that helps to learn more control principles. The compactness is due to the number of rules being not too many. A 10-h evaluation trial of the trained fuzzy controller demonstrated its capability in regulating the water level under random disturbances and reference level changes.

The velocity dipole field method is presented for real-time collision avoidance of mobile robots. The direction of motion of the obstacle is used as the axis of the dipole field, and the speed of the obstacle is used to proportionally strengthen the dipole field. The elliptical field lines of the dipole field are useful to skillfully guide the robot around obstacles, quite similar to the way humans avoid moving obstacles. Field modulation coefficient is also introduced to weaken the field effect as the obstacle recedes. The real-time algorithm of the velocity dipole field has been devised and experimentally tested on the robot soccer test-bed. The results show the capability of the new real-time collision avoidance strategy and how it can overcome the weaknesses in the conventional potential field method. The new method makes an explicit and proactive action of collision avoidance, unlike the conventional method, which forces the robot merely away from the obstacle aimlessly. The proposed method delivers greater capability with no considerable computational overhead