Application of a sliding-mode observer for position and speedestimation in switched reluctance motor drives

A sliding-mode observer is applied toward the operation of a switched reluctance motor (SRM) drive. The sliding-mode observer estimates rotor position and velocity to control the conduction angles of the machine. Conventional on-off control with hysteresis current control is included with the position estimation scheme. The particular case of an automotive brake system motor is considered in detail where the conduction angles are modified with velocity feedback to provide optimum time response to brake system commands. Nonlinear modeling of a SRM is described and a computer simulation is developed based on data from an experimental SRM system. The sliding-mode observer is implemented with fixed-point and floating-point digital signal processors (DSPs) and the discrete-time implementations first examined under locked-rotor conditions. A comparison is also made between the implementation in two different types of DSPs. After confirming the accuracy of the computer simulation with experimental data, the design considerations in selecting observer coefficients with regard to sampling time, convergence rate, and transient stability are discussed. In conclusion, the effects of flux estimation errors on the system time response during a startup transient are examined     

Switched reluctance and permanent magnet brushless motors in highly dynamic situations: a comparison in the context of electric brakes

Electromechanical brake (EMB) systems offer the potential for enhanced vehicle control while simplifying the car assembly as well as recycling process. This article offers a comparison of two motor technologies, switched reluctance (SR) and permanent magnet (PM) brushless, motor in highly dynamic situations, in all four quadrants of their torque-speed operating regions, for an EMB application and also describes the motor designs and their static characteristics, before examining in depth their dynamic behavior, in particular special control adaptations to enable the SR motor to reverse rapidly when needed. A 20% longer SR motor provided overall similar dynamic performance, but only if the SR motor is fitted with a speed limit. A method to choose such a speed limit was developed, and the software algorithm implementation was found to be simple and successful.     

Multilayer ARROW channel waveguide for evanescent field enhancement in low-index media

A multilayer antiresonance reflecting optical waveguide (ARROW) channel waveguide geometry, believed to be novel, is proposed for enhancing the evanescent field in low-index materials. The finite-difference method is used in the analysis of the structure. The fraction of the fundamental TE-like-mode power in the low-index material (air) is used as a measure of the evanescent field enhancement. The calculated results suggest that the evanescent field of the fundamental TE-like mode can be significantly increased in air while the low modal loss that characterizes the leaky nature of the structure is maintained. The results also suggest that a semivectorial approach to this problem is adequate for analysis of the proposed waveguide structure.     

Multiobjective mixed symmetric duality involving cones

A pair of multiobjective mixed symmetric dual programs is formulated over arbitrary cones. Weak, strong, converse and self-duality theorems are proved for these programs under K-preinvexity and K-pseudoinvexity assumptions. This mixed symmetric dual formulation unifies the symmetric dual formulations of Suneja et al. (2002) [14] and Khurana (2005) [15].     

A new error handling algorithm for controller area network in networked control system

An effective error handling mechanism plays an important role to ensure the reliability and robustness of the application of controller area network (CAN) in controlling dynamic systems. This paper addresses a new online error handling approach or named per-sample-error-counting (PSeC) technique that tends to replace native error handling protocol in controller area network (CAN). The mechanism is designed to manage transmission errors of both sensor and control data in networked control system (NCS) used in controlling dynamic system such that the stability of the feedback system is preserved. A new parameter denoted as maximum allowable number of error burst (MAEB) is introduced in which MAEB is selected based on available bandwidth of the CAN network. MAEB serves as the maximum number of attempt of re-transmission of erroneous data per sample which allows the maximum transmission period to be known and guaranteed for time-critical control system. The efficacy of the proposed method is verified by applying the algorithm on the fourth order inverted pendulum system simulated on Matlab/Truetime simulator and the performance is benchmarked with the existing CAN error management protocol. The simulation run under various systems conditions demonstrate that the proposed method results in superior system performance in handling data transmission error as well as meeting control system requirement.     

SURF: A distributed channel selection strategy for data dissemination in multi-hop cognitive radio networks

In this paper, we propose an intelligent and distributed channel selection strategy for efficient data dissemination in multi-hop cognitive radio network. Our strategy, SURF, classifies the available channels and uses them efficiently to increase data dissemination reliability in multi-hop cognitive radio networks. The classification is done on the basis of primary radio unoccupancy and of the number of cognitive radio neighbors using the channels. Through extensive NS-2 simulations, we study the performance of SURF compared to four related approaches. Simulation results confirm that our approach is effective in selecting the best channels for efficient communication (in terms of less primary radio interference) and for highest dissemination reachability in multi-hop cognitive radio networks.     

Evaluation of acoustic noise and mode frequencies with design variations of switched reluctance machines

The stator mode frequency, as well as the intensity of acoustic noise generated by magnetic radial force, is related to the geometry, configuration, and material properties of the switched reluctance machine (SRM). Two different four-phase 8/6 SRMs with similar specifications, torque-speed requirements, and envelope dimensions have been designed and built for experiments related to noise intensity and stator mode frequencies. One of these two SRMs, labeled as low-noise SRM is designed following the low-noise design guidelines. The other one, labeled as conventional SRM is designed following the conventional design methodology. The mode frequencies and noise pressure levels for both the SRMs have been calculated using the analytical models. Acoustic-noise data collected from a test bench are analyzed to correlate the experimental and theoretical results.     

Intelligent network: a key platform for PCS interworking andinteroperability

The Tl and TIA standards committees in the United States have worked jointly on the development of the first phase of personal communication services (PCS) standards, which were approved in December 1995. PCS systems based on these standards are currently under development. As these systems are deployed, the variety of wireless systems will grow, making interworking and interoperability a key challenge. This article provides an overview of PCS standards and explores how the different types of wireless systems (PCS and cellular) will utilize the capabilities of the intelligent network to provide seamless roaming     

Clinical profile of patients admitted to the coronary care unit with possible myocardial infarction without diagnostic ECG and/or enzyme changes

Concern has been expressed about the cost-effectiveness of the Coronary Care Unit (CCU) and solution options offered on account of the large number of patients admitted to the CCU who turn out not to have acute myocardial infarction. In a prospective study over four years, we studied a group of patients admitted to the CCU with suspected myocardial infarction but who did not have diagnostic ECG and/or enzyme changes for the causes of their chest pain. We compared the clinical profile of these patients (Group A) with that of a random sample of patients with confirmed myocardial infarction (Group B). Gastrointestinal disorders, musculoskeletal chest pain, panic and anxiety disorders were the major causes of chest pain in Group A patients. A normal ECG and a normal creatine phosphokinase (CPK) within the first 24 hours, a normal initial random blood sugar, a younger age and absence of coronary risk factors effectively separated Group A patients as low risk from Group B patients as high risk for acute myocardial infarction. These simple parameters will assist physicians providing CCU care in most hospitals in early decision making and in the judicious use of the CCU.     

Position kinematics of a two limbed mixed mechanism

Comparatively little attention has been paid to the kinematic and static characteristics of mixed mechanisms which have combinations of the characteristics of fully serial and fully parallel mechanisms. Such actively coordinated mechanisms having combinations of serial and parallel manipulator chains have been practically employed and are expected to become more useful in the future. This work addresses the direct and inverse position kainematics of a two limbed mixed mechanism having multiple actuated joints in each limb, along with other passive joints. Closed form solutions for the direct position kinematics problem have been obtained for two different cases of this mechanism.