Sharif Digital Repository

A combination of low-cost micro-electoro-mechanical sensors (MEMSs) and nonlinear attitude estimation algorithm techniques can provide an inexpensive and accurate system for navigation and attitude determination. The features of MEMSs are their light weight and small size; hence, the MEMSs have found significant attention in low-cost navigation and control systems [1]. A common disadvantage of these sensors is the significant errors that accompany the corresponding measurements. The accuracy obtained using MEMSs depends on a number of factors, such as scale factor, bias, and random noise corrections [2]. However, these low-cost sensors suffer from large noise and errors, making calibration... 

The navigation algorithms which use inertial measurement units (IMUs), such as inertial navigation systems (INSs), always suffer from intrinsic accumulated errors. Bias in gyros induces a significant drift in navigation output especially when micro-electro-mechanical sensor (MEMS) type is used. This error has high-and low-frequency components. De-noising of the long-term error (LTE) (the low-frequency component) is more challenging due to undeterministic behavior and overlapping with carrier motion in the low-frequency band. In this article, a method for de-noising of long-term MEMS-based gyro is presented. In this approach, an auto-regressive (AR) model for the LTE is developed which is... 

In wireless body area networks (WBANs) it is necessary to devise an energy-efficient MAC scheduling mechanism which is capable of meeting strict QoS requirements. In this paper, special characteristics of WBAN channels, namely, the slow fading, the periodicity of fading, and the correlation among the channels have been exploited to formulate the sensor scheduling problem as a partially observable Markov decision problem (POMDP). Specific algorithms based on value iteration and pruning have been proposed in order to reduce the computational burden associated with the corresponding POMDP. The proposed scheduling mechanism is compared against a TDMA scheduling for a three-sensor network, and an... 

Control of powered lower limb prostheses has a locomotion mode-dependent structure which demands a pattern recognizer that can classify the current locomotion mode and also detect transitions between them in an appropriate time. In order to achieve this goal, this paper presents a Fuzzy sequential locomotion mode recognition system to classify daily locomotion modes including level- walking, stair climbing, slope walking, standing and sitting using low-cost mechanical sensors. Since these signals have a quasi-periodic nature, using sequential pattern recognition tools, such as Hidden Markov Model(HMM) improves the recognition performance considering they use sequences of information to make... 

This paper is concerned with the stability of nonlinear Lipschitz systems subject to bounded process and measurement noises when transmission from sensor to controller is subject to distortion due to quantization. A stabilizing technique and a sufficient condition relating transmission rate to Lipschitz coefficients are presented for almost sure asymptotic bounded stability of nonlinear uncertain Lipschitz systems. In the absence of process and measurement noises, it is shown that the proposed stabilizing technique results in almost sure asymptotic stability. Computer simulations illustrate the satisfactory performance of the proposed technique for almost sure asymptotic bounded stability... 

Two-degree-of-freedom (2-DOF) electrical machines require position sensors for their motion control. In comparison with using two independent sensors, using a 2-DOF sensor enhances the closed-loop control system's performance. However, due to the 3-D structure of the 2-DOF sensor, its performance evaluation needs 3-D analysis. Also, due to helical motion the accuracy deterioration of the sensor, under mechanical faults needs more attention. Although the finite element method (FEM) is the best way to simulate such sensors, most of the commercial packages for transient finite element simulations are not able to consider two separate motions simultaneously. Furthermore, FEM has a high...