Seoyong Shin

Development of Optical Fiber-based Daylighting System with Uniform Illumination

Daylighting has a very effective role in reducing power consumption and improving indoor environments in office buildings. Previously, it was not under consideration as a major source of renewable energy due to poor reliability in the design. Optical fiber as a transmission medium in the daylighting system demands uniform distribution of light to solve cost, heat, and efficiency issues. Therefore, this study focuses on the uniform distribution of sunlight through the fiber bundle and to the interior of the building. To this end, two efficient approaches for the fiber-based daylighting system are presented. The first approach consists of a parabolic mirror, and the second approach contains a Fresnel lens. Sunlight is captured, guided, and distributed through the concentrator, optical fibers, and lenses, respectively. At the capturing stage, uniform illumination solves the heat problem, which has critical importance in making the system cost-effective by introducing plastic optical fibers. The efficiency of the system is increased by collimated light, which helps to insert maximum light into the optical fibers. Furthermore, we find that the hybrid system of combining sunlight and light emitting diode light gives better illumination levels than that of traditional lighting systems. Simulation and experimental results have shown that the efficiency of the system is better than previous fiber-based daylighting systems.

Integrated collision avoidance and tracking system for mobile robot

In the intelligent transportation system, various accident avoidance techniques have been applied. Among them, one of the most common issues is the collision, which is yet unsolved problem. To this end, we develop collision warning and avoidance system (CWAS), which is implemented in the wheeled mobile robot. Likewise, path planning is a crucial problem in the mobile robots to perform a given task correctly. Here, a tracking system is presented for the mobile robot, which follows an object. Thus, we have implemented an integrated CWAS and tracking system in the mobile robot. Both systems can be activated independently. In the CWAS, the robot is controlled through a remotely controlled device, and collision prediction and avoidance functions are performed. In the tracking system, the robot performs tasks autonomously, where the robot maintains a constant distance from the followed object. The surrounding information is obtained through the range sensors, and the control functions are performed through the microcontroller. The front, left, and right sensors are activated to track the object, and all the sensors are used for the CWAS. Two algorithms based on the sensory information are developed with the distance control approach. The proposed system is tested using the binary logic controller and the fuzzy logic controller (FLC). The comparison of both controllers is also described by preferring time delay and complexity. The efficiency of the robot is improved by increasing smoothness in motion using the FLC, achieving accuracy in tracking, and advancements in the CWAS. Finally, simulation and experimental outcomes have displayed the authenticity of the system.

Modified optical fiber daylighting system with sunlight transportation in free space

We present the design, optical simulation, and experiment of a modified optical fiber daylighting system (M-OFDS) for indoor lighting. The M-OFDS is comprised of three sub-systems: concentration, collimation, and distribution. The concentration part is formed by coupling a Fresnel lens with a large-core plastic optical fiber. The sunlight collected by the concentration sub-system is propagated in a plastic optical fiber and then collimated by the collimator, which is a combination of a parabolic mirror and a convex lens. The collimated beam of sunlight travels in free space and is guided to the interior by directing flat mirrors, where it is diffused uniformly by a distributor. All parameters of the system are calculated theoretically. Based on the designed system, our simulation results demonstrated a maximum optical efficiency of 71%. The simulation results also showed that sunlight could be delivered to the illumination destination at distance of 30 m. A prototype of the M-OFDS was fabricated, and preliminary experiments were performed outdoors. The simulation results and experimental results confirmed that the M-OFDS was designed effectively. A large-scale system constructed by several M-OFDSs is also proposed. The results showed that the presented optical fiber daylighting system is a strong candidate for an inexpensive and highly efficient application of solar energy in buildings.

Mobile robot navigation with distance control

Intelligent systems to increase the road safety have been widely applied in the automotive sector; similarly, they have critical importance in the robotics to navigate the robot safely. Automatic distance control system helps to avoid collision between vehicles. In this paper, we present an algorithm to maintain a distance between the robot and the object. It keeps the autonomous mobile robot at a safe distance from the object. It is implemented in a wheeled mobile robot to track the moving object. The surrounding information is obtained through the range sensors that are mounted at the front side of the robot. The central sensor gives instructions for the forward and backward motion, and the other sensors help for the left and right motion. To avoid collision, safety distance, which makes the movement easy in the out of range, stop, and forward and backward modes, is predefined in the mobile robot. Each time the range data is compared with the predefined distance measurements, and the respected function is activated. The robot is characterized due to low cost and simple control architecture. Different experiments were carried out in the indoor and outdoor environments with different objects. The results have shown that the robot tracks the object correctly by maintaining a constant distance from the followed object.

A Metro WDM Star Network with a Hybrid MAC Protocol Based on an Arrayed Waveguide Grating

In this paper, we introduce a reliable, scalable, and cost-effective switchless wavelength division multiplexing (WDM) network based on a quality-of-service supporting reservation-based medium access control (MAC) protocol. The protocol not only provides both packet and circuit switching but also supports multicasting. The network efficiency is significantly increased by spatially reusing wavelengths and exploiting multiple free spectral ranges (FSRs) of arrayed waveguide grating (AWG) employed in the architecture. We have demonstrated the feasibility of this architecture by simulating in

Optical Fiber Daylighting System Combined with LED Lighting and CPV based on Stepped Thickness Waveguide for Indoor Lighting

Optsim^{TM}

Development of optical fiber-based daylighting system with collimated illumination

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Design and Performance Analysis of 2- Dimensional Optical CDMA Encoder/Decoder Using an Array of SSFBGs

We present a design and optical simulation of a cost-effective hybrid daylighting/LED system composed of mixing sunlight and light-emitting diode (LED) illumination powered by renewable solar energy for indoor lighting. In this approach, the sunlight collected by the concentrator is split into visible and non-visible rays by a beam splitter. The proposed sunlight collector consists of a Fresnel lens array. The non-visible rays are absorbed by the solar photovoltaic devices to provide electrical power for the LEDs. The visible rays passing through the beam splitters are coupled to a stepped thickness waveguide (STW) by tilted mirrors and confined by total internal reflection (TIR). LEDs are integrated at the end of the STW to improve the lighting quality. LEDs’ light and sunlight are mixed in the waveguide and they are coupled into an optical fiber bundle for indoor illumination. An optical sensor and lighting control system are used to control the LED light flow to ensure that the total output flux for indoor lighting is a fixed value when the sunlight is inadequate. The daylighting capacity was modeled and simulated with a commercial ray tracing software (LighttoolsTM). Results show that the system can achieve 63.8% optical efficiency at geometrical concentration ratio of 630. A required accuracy of sun tracking system achieved more than ±0.5o. Therefore, our results provide an important breakthrough for the commercialization of large scale optical fiber daylighting systems that are faced with challenges related to high costs.

Development of daylighting systems with non-imaging concentrator

Uniform illumination for optical fiber-based daylighting system is acquired at capturing and distributing stages, and efficiency of the system is increased by collimated light. Two approaches are proposed for parabolic mirror and Fresnel lens.

Fast gain-transient recovery of cascaded EDFAs in WDM networks using a disturbance observer with a PID controller

We propose a two-dimensional temporal/wavelength optical code division multiple access (OCDMA) encoder/decoder, which has an array of superstructured fiber Bragg gratings (SSFBGs). SSFBGs in an encoder/decoder have different wavelengths from each other and can be coded with the same OCDMA code or not. Simulation was performed to analyze the feasibility of the scheme.