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    Sum capacity bounds and design of errorless codes for binary asynchronous CDMA systems

    , Article 2012 19th International Conference on Telecommunications, ICT 2012, 23 April 2012 through 25 April 2012, Jounieh ; 2012 ; 9781467307475 (ISBN) Dashmiz, S ; Mansouri, S. M ; Najafi, A ; Marvasti, F ; Sharif University of Technology
    IEEE  2012
    Abstract
    In this paper, some codes are designed for a binary chip-asynchronous CDMA system which guarantee errorless communication in the absence of noise. These codes also show good performance for noisy channels. In addition, lower and upper bounds for the sum channel capacity are derived for finite and asymptotic cases with the assumption of both noiseless and noisy channels. The results are derived assuming that user delays are known at the receiver end. The performance of proposed codes in the noisy case is also compared to both Gold sequences and a similar class of binary sequences with constrained amount of correlation  

    Errorless codes for CDMA systems with near-far effect

    , Article IEEE International Conference on Communications, 23 May 2010 through 27 May 2010, Cape Town ; 2010 ; 05361486 (ISSN) ; 9781424464043 (ISBN) Shafinia, M. H ; Kabir, P ; Pad, P ; Mansouri, S. M ; Marvasti, F ; Sharif University of Technology
    2010
    Abstract
    In this paper we propose a new model for the near-far effect in a CDMA system. We derive upper and lower bounds for the maximum near-far effect for errorless transmission. Using these bounds, we propose some near-far resistant codes. Also a very low complexity ML decoder for a subclass of the proposed codes is suggested  

    Online path planning for Surena III humanoid robot using model predictive control scheme

    , Article 4th RSI International Conference on Robotics and Mechatronics, ICRoM 2016, 26 October 2016 through 28 October 2016 ; 2017 , Pages 416-421 ; 9781509032228 (ISBN) Mirjalili, R ; Yousefi Koma, A ; Shirazi, F. A ; Mansouri, S ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2017
    Abstract
    In this paper, two online path planning methods are presented for SURENA III humanoid robot by using model predictive control scheme. The methods are general control schemes which can generate the online motions for walking of a humanoid robot. For lowering computational costs a three dimensional linear inverted pendulum model is used instead of the full dynamical model of the robot. The generated trajectories are then used for computing the zero-moment point (ZMP) of the robot and the joint torques. The resulted joint torques of the two methods are compared to torques obtained from Genetic Algorithm (GA) path planning method presented for SURENA III humanoid robot in previous studies. The... 

    Investigation on dynamic modeling of SURENA III humanoid robot with heel-off and heel-strike motions

    , Article Iranian Journal of Science and Technology - Transactions of Mechanical Engineering ; Volume 41, Issue 1 , 2017 , Pages 9-23 ; 22286187 (ISSN) Sadedel, M ; Yousefi Koma, A ; Khadiv, M ; Mansouri, S ; Sharif University of Technology
    Shiraz University  2017
    Abstract
    The understudy SURENA III humanoid robot was designed and fabricated at the Center of Advanced Systems and Technologies (CAST) located in the Universityof Tehran. In this paper, a full dynamic model of SURENA III in different walking phases including heel-offand heel-strike motions is presented. To this end, first a trajectory planning method based on robot kinematics is introduced. Then, the multi-body dynamics of the robot links are calculated using Lagrange and Kane approaches which are then verified. In this model, the power transmissionsystem is considered to be ideal. Afterward, system identification routine is adopted to model the dynamic behavior of the power transmission system. By... 

    Optimal stair climbing pattern generation for humanoids using virtual slope and distributed mass model

    , Article Journal of Intelligent and Robotic Systems: Theory and Applications ; Volume 94, Issue 1 , 2019 , Pages 43-59 ; 09210296 (ISSN) Shahrokhshahi, A ; Yousefi Koma, A ; Khadiv, M ; Mansouri, S ; Mohtasebi, S. S ; Sharif University of Technology
    Springer Netherlands  2019
    Abstract
    This study addresses optimal walking pattern generation for SURENA III humanoid robot in a stair-climbing scenario. To this end, the kinematic configuration of the 31-DOF humanoid robot is studied. Integrating the detailed dynamic properties of the robot, a comprehensive and precise dynamic model is developed for its lower-limb. In order to generate the optimal walking pattern for the considered humanoid robot, trajectories for feet and pelvis are first designed, and then joint angles are derived by means of inverse kinematics. Such a complete model provides the designer with the necessary tools to optimize the trajectory generation. Using two different types of objective functions, namely... 

    Optimal gait planning for humanoids with 3D structure walking on slippery surfaces

    , Article Robotica ; 2015 ; 02635747 (ISSN) Khadiv, M ; Moosavian, S. A. A ; Yousefi Koma, A ; Sadedel, M ; Mansouri, S ; Sharif University of Technology
    Abstract
    In this study, a gait optimization routine is developed to generate walking patterns which demand the lowest friction forces for implementation. The aim of this research is to fully address the question “which walking pattern demands the lowest coefficient of friction amongst all feasible patterns?”. To this end, first, the kinematic structure of the considered 31 DOF (Degrees of Freedom) humanoid robot is investigated and a closed-form dynamics model for its lower-body is developed. Then, the medium through which the walking pattern generation is conducted is presented. In this medium, after designing trajectories for the feet and the pelvis, the joint space variables are obtained, using... 

    Optimal gait planning for humanoids with 3D structure walking on slippery surfaces

    , Article Robotica ; Volume 35, Issue 3 , 2017 , Pages 569-587 ; 02635747 (ISSN) Khadiv, M ; Moosavian, S. A. A ; Yousefi Koma, A ; Sadedel, M ; Mansouri, S ; Sharif University of Technology
    Cambridge University Press  2017
    Abstract
    In this study, a gait optimization routine is developed to generate walking patterns which demand the lowest friction forces for implementation. The aim of this research is to fully address the question which walking pattern demands the lowest coefficient of friction amongst all feasible patterns?. To this end, first, the kinematic structure of the considered 31 DOF (Degrees of Freedom) humanoid robot is investigated and a closed-form dynamics model for its lower-body is developed. Then, the medium through which the walking pattern generation is conducted is presented. In this medium, after designing trajectories for the feet and the pelvis, the joint space variables are obtained, using the... 

    Rigid vs compliant contact: an experimental study on biped walking

    , Article Multibody System Dynamics ; Volume 45, Issue 4 , 2019 , Pages 379-401 ; 13845640 (ISSN) Khadiv, M ; Moosavian, S. A. A ; Yousefi-Koma, A ; Sadedel, M ; Ehsani Seresht, A ; Mansouri, S ; Sharif University of Technology
    Springer Netherlands  2019
    Abstract
    Contact modeling plays a central role in motion planning, simulation and control of legged robots, as legged locomotion is realized through contact. The two prevailing approaches to model the contact consider rigid and compliant premise at interaction ports. Contrary to the dynamics model of legged systems with rigid contact (without impact) which is straightforward to develop, there is no consensus among researchers to employ a standard compliant contact model. Our main goal in this paper is to study the dynamics model structure of bipedal walking systems with rigid contact and a novel compliant contact model, and to present experimental validation of both models. For the model with rigid... 

    Dynamic simulation of natural gas transmission pipeline systems through autoregressive neural networks

    , Article Industrial and Engineering Chemistry Research ; Volume 60, Issue 27 , 2021 , Pages 9851-9859 ; 08885885 (ISSN) Fakhroleslam, M ; Bozorgmehry Boozarjomehry, R ; Sahlodin, A. M ; Sin, G ; Mansouri, S. S ; Sharif University of Technology
    American Chemical Society  2021
    Abstract
    Transmission of natural gas from its sources to end users in various geographical locations is carried out mostly by natural gas transmission pipeline networks (NGTNs). Effective design and operation of NGTNs requires insights into their steady-state and, particularly, dynamic behavior. This, in turn, calls for efficient computer-aided approaches furnished with accurate mathematical models. The conventional mathematical methods for the dynamic simulation of NGTNs are computationally intensive. In this paper, the use of autoregressive neural networks for cost-effective dynamic simulation of NGTNs is proposed. Considering the length, diameter, roughness, and elevation as the main...