Anti-Windup Compensator Design For Improved Tracking Performance Of Differential Drive Mobile Robot

Wheeled mobile robots (WMRs) have been widely used for navigation purposes as well as industrial applications such as path tracking and obstacle detections. Differential drive robot (DDR) is one type of WMRs with a specific wheel configuration where two fixed wheels are controlled by the motors and a castor wheel is added to mechanically support its translational and rotational movements. For tracking purposes, the controller plays a very important role to ensure it does not deviate far from the targeted locations or path. In this project, a DDR is built with two DC motors. As most motors exhibit nonlinear behavior, they are modeled as a multivariable Hammerstein-Wiener structure which contains static nonlinearities and a linear system in series with each other. The identification of the linear model is performed via time response analysis with different types of inputs, whereas the nonlinearities are estimated via several tests in MATLAB Simulink. This work also focuses on both dynamic and kinematic models of the DDR where a proportional-integral (PI) controller is designed to achieve the desired specifications in the linear region. In order to account for the nonlinear effects from the DC motor model which is mainly influenced by its bounded velocity capability, a static anti-windup compensator (AWC) is implemented which is activated when the controller output exceeds the bound. Via this strategy, a significant improvement on the tracking performance of the DDR can be observed via simulations especially when the desired path involves sharp corners or turns.

Consumer beliefs and attitudes toward marketing : an emerging market perspective

The burgeoning consumerism in emerging market economies has significant implications for both multinational corporations and local companies. Based on a survey in four cities in China, this study examines the effect of consumer beliefs and attitudes towards marketing on satisfaction. The results suggest that attitudes towards marketing activities and their beliefs about marketing have significant effect on consumer satisfaction, but these effects are not uniform across marketing mix variables. Implications for future research and marketing operations in Emerging Markets are explored

An Ex Post Evaluation of the U.S. Acid Rain Program

Emissions trading programs have been recommended by economists and implemented by policy makers because they are expected to keep compliance costs low; but, studies on actual savings are limited. This paper is the first to conduct a comprehensive ex post analysis of the cost savings from the Acid Rain Program (ARP), the largest emissions trading program to be implemented in the U.S. In Chapter 2, I provide a brief overview of the Acid Rain Program. I then discuss other policies that are relevant to evaluating the ARP including the New Source Performance Standard and local emission standards. I conclude the chapter by analyzing the determinants of local emission standards and arguing that it is safe to treat these standards as exogenous. In Chapter 3 I illustrate the cost savings from a cap-and-trade system such as the ARP, and discuss factors affecting the potential gains from trade and the determinants. I then estimate a discrete choice model of coal procurement and scrubber installation to recover structural parameters of compliance cost functions at the generating unit level. Using the model I predict compliance choices under a uniform emission standard that yields the same aggregate emissions as the ARP. In Chapter 4, I estimate cost savings under the ARP to be about 265-380 million (1995 USD) per year. The numbers are much smaller than in previous literature (Carlson et al., 2000; Ellerman et al., 2000). I propose that lower transport costs reduced cost heterogeneity across generating units, and that improvements in scrubbing technology and state policies may have also contributed to a decrease in cost savings

The Western songs (Xiqu) of the southern dynasties (420-589) - a critical study

Though the Western songs or Xiqu have been frequently anthologized alongside the Wu songs to represent the folk poetry of the Southern Dynasties (420-589 A.D.), there has been as yet no attempt to study the songs in depth. It is the purpose of this study to fill the gap. The songs are viewed primarily as an orally delivered art, fostered by a particular social context and a regional folk tradition. The ethnic and musical backgrounds are discussed, then the lyrics are analysed in terms of themes, imagery, prosodic structures, formulaic language and puns. The emphasis is always on the distinctive features of the songs which may reflect a regional folk tradition and the peculiarities of oral delivery. The result of this study points up the presence of regional folk tradition, which has, in matters of music, incorporated into itself some significant non-Han-Chinese elements, and was interactive with the literary tradition and other local song traditions•. The finding should not only enrich our understanding of an important song repertory, but also reveal something of the Chinese folk literature in general. The work should, moreover, form part of the basis for a systematic investigation of the interaction between the folk and the literary traditions in the Chinese culture

Optimal stimulation duration of tens in the management of osteoarthritic knee pain

Objective: This study examined the optimal stimulation duration of transcutaneous electrical nerve stimulation (TENS) for relieving osteoarthritic knee pain and the duration (as measured by half-life) of post-stimulation analgesia. Subjects: Thirty-eight patients received either: (i) 20 minutes (TENS20); (ii) 40 minutes (TENS40); (iii) 60 minutes (TENS60) of TENS; or (iv) 60 minutes of placebo TENS (TENSPL) 5 days a week for 2 weeks. Methods: A visual analogue scale recorded the magnitude and pain relief period for up to 10 hours after stimulation. Results: By Day10, a significantly greater cumulative reduction in the visual analogue scale scores was found in the TENS40 (83.40%) and TENS60 (68.37%) groups than in the TENS20 (54.59%) and TENSPL (6.14%) groups (p 3 0.000), such a group difference was maintained in the 2-week followup session (p 3 0.000). In terms of the duration of post-stimulation analgesia period, the duration for the TENS40 (256 minutes) and TENS60 (258 minutes) groups was more prolonged than in the other 2 groups (TENS20 = 168 minutes, TENSPL = 35 minutes) by Day10 (p 3 0.000). However, the TENS40 group produced the longest pain relief period by the follow-up session. Conclusion: 40 minutes is the optimal treatment duration of TENS, in terms of both the magnitude (VAS scores) of pain reduction and the duration of post-stimulation analgesia for knee osetoarthritis.<br /