An Efficient Driver for Dimmable LED Lighting

An efficient driver circuit is proposed for light-emitting-diode (LED) lamps with dimming feature. The driver consists of a flyback converter in series with the dc-link. By processing partial power of the driver circuit for current regulation, the loss produced by power conversion can be diminished. The dimming feature is accomplished by means of current amplitude modulation (AM) or double pulse-width modulation (DPWM). The detailed circuit operation stages and analysis are provided. A laboratory circuit is designed for a 45 W LED lamp. Experimental results demonstrate that a high efficiency can be achieved, even at a dimmed lamp power.The light-emitting-diode (LED) characterized by mercury-free, high efficiency and long life cycle, is expected to be the new generation of lighting source . With great improvement in power capacity and reduction in cost, the LED has been becoming more and more popular in many applications. The increased popularity of LEDs has challenged electronic engineers to come up with efficient and cost-effective solutions on the design of the driver circuits.Up to now, one of the most commonly used high-brightness white LED is rated at 1 Watt, which is driven at 350 mA, even though manufacturers are constantly working on driving LEDs at a higher current.To provide sufficient light output, an LED lamp fixture always involves large arrays of individual LEDs stacked in series. LEDs are current-driven devices. A white LED's luminous intensity and chromaticity are proportional to the forward current. For this reason, a driver circuit is designed essentially to drive LEDs at a required constant current . Conventionally, driving a string of high-brightness LEDs at an accurate dc current typically resorts to a linear regulator or a more complicated switching regulator with sophisticated control, especially when dimming function is included. These solutions, however, are of either poor efficiency or higher cost. To improve the overall efficiency of LED lighting, an efficient driver is proposed in this paper. The main concept of the efficient driver is explained by Fig. 1. The operating characteristic of an LED. Theoretically, only a trivial current is generated on an LED when the forward voltage is lower than its cut-in voltage. Beyond the threshold, a small variation in the forward voltage results in a significant change in the LED current. the proposed LED driver circuit, in which a string of LEDs is driven by two sources, one for providing the cut-in voltage and the other for regulating the forward current. In practice, the cut-in voltage is much higher than that for current regulation. In such a configuration, the dc voltage source for cutting in LED linear operation supplies the most part of LED power directly, while only a small amount of power has to be processed for current regulation, leading to a high overall efficiency.

Development of a Microcontroller Based Robotic Arm

Robotic arm has become popular in the world of robotics. The essential part of the robotic arm is a programmable microcontroller based brick capable of driving basically three stepper motors design to form an anthropomorphic structure. The first design was for experimental use on a human-size industrial robot arm called PUMA 560 used to explore issues in versatile object handling and compliance control in grasp actions (Bejczy & Jau, 1986). This paper explains the method of interfacing the robotic arm stepper motors with the programmed 8051-based microcontroller which are used to control the robot operations. We have employed the assembly language in programming our microcontroller. A sample robot which can grab (by magnetizing) and release small objects (by demagnetizing) is built for demonstrating the method explained.

Taking a look back at the history of robot development, a special kind of human-size industrial robotic arm called Programmable Universal Machine for Assembly (PUMA) came into existence.This type of robot is often termed anthropomorphic because of the similarities between its structure and the human arm. The individual joints are named after their human-arm counterparts. “It is worth noting that in our work, the hand is magnetic and not a generalized manipulator. In the proper sense of the word, manipulation is the function of the arm. The function of the arm is to position and orient the hand, act as a mechanical connection and power and sensing transmission link between the hand and the main body of the person. The full functional meaning of the arm rests in the hand” (Bejczy & Jau, 1986). Our work provides important elements that are required to build a simple robotic arm of very high quality. As stated earlier we are making use of the 8051-based microcontroller.

A Wireless Robot for Networked Laparoscopy

State-of-the-art laparoscopes for minimally invasive abdominal surgery are encumbered by cabling for power, video,and light sources. Although these laparoscopes provide good image quality, they interfere with surgical instruments, occupy a trocar port, require an assistant in the operating room to control the scope,
have a very limited field of view, and are expensive. MARVEL is a wireless Miniature Anchored Robotic Videoscope for Expedited Laparoscopy that addresses these limitations by providing an inexpensive
in vivo wireless camera module (CM) that eliminates the surgical-tool bottleneck experienced by surgeons in current laparoscopic endoscopic single-site (LESS) procedures. The MARVEL system includes 1) multipleCMsthat feature a wirelessly controlled pan/tilt camera platform, which enable a full hemisphere field of view inside the abdominal cavity, wirelessly adjustable focus, and a multiwavelength illumination control system; 2) amaster control module that provides a near-zero latency video wireless communications link, independent wireless control for multiple MARVEL CMs, digital zoom; and 3) awireless human–machine interface that gives the surgeon full control over CM functionality. The research reported in this paper is the first step in developing a suite of semiautonomous wirelessly controlled and networked robotic cyberphysical devices to enable a paradigm shift in minimally invasive surgery and other domains such as wireless body area networks.

Cloud Robotics: Architecture, Challenges and Applications

the computation and information sharing capabilities of networked robotics by proposing a cloud robotic architecture. The cloud robotics architecture leverages the combination of a virtual ad-hoc cloud formed by machine-to-machine (M2M) communications among participating robots, and an infrastructure cloud enabled by machine-to-cloud (M2C) communications.Cloud robotics utilizes elastic computing models, in
which resources are dynamically allocated from a shared resource pool in the cloud, to support task offloading and information sharing in robotic applications. We propose communication protocols, and several elastic computing models to handle different applications. We discuss the technical challenges in computation,
communications and security, and illustrate the potential benefits of cloud robotics in several applications