Applied Mechanics and Materials Vol. 245

Abstract: A new approach for the detection of the step initiation in the lower extremity exoskeleton is presented. As the detection of the step initiation is the important factor for the lower extremity exoskeleton to shadow the operator’s movement as soon as possible, many studies have been done to detect it faster by using heel-off time or toe-off time. We detect the step initiation faster than other approaches with the vertical ground reaction forces. Also, we predict the first step’s heel strike time with the regression equations based on the vertical ground reaction forces as soon as we detect the step initiation. It could enable the lower extremity exoskeleton to shadow the operator’s movement much faster.

Abstract: The aim of this work is to research the feasibility of using optical odometer as the aided sensor for accuracy improvement of medium accuracy (FOG)-based IMU for land vehicle navigation. Usually GNSS is integrated with low cost SINS (strapdown inertial navigation systems) for land vehicle navigation but GNSS is not always reliable in land vehicle applications. The focus is on analysis of position and velocity accuracy of SINS/Odometer integration using close loop kalman filter. Integrated navigation algorithm for vehicle states estimation and correction have been designed and implemented. The measurement error model for odometer in navigation frame is developed for Kalman filter implementation. As the prior knowledge of measurement noise which represents the stochastic properties of odometer is not exactly known, so an adaptive Kalman filter (AKF) is also proposed for online estimation of the measurement noise matrix in order to improve the accuracy. For the performance analysis of the designed system, field test is carried out and results show that the accuracy of the medium accuracy fiber optics gyro (FOG)-based SINS is improved and the systems is capable for land vehicle navigation application

Abstract: A Continuous Sliding-Mode Controller (CSMC) using integral action is implemented to control the response of the longitudinal dynamics of an aircraft. Model-following of the pitch rate q is obtained through this method. Asymptotic regulation achieved by integral control has its downsides because transient performance is reduced. A solution to this problem consists in using the integral action only “conditionally”, thus eliminating the performance downgrade. Finally a comparison will show how Sliding-mode control will minimize the chattering phenomenon and also reduce “integrator windup” problem, thus minimizing the loss of transient performance.

Abstract: The observation that the chemical equilibrium between the combustion products of solid propellant samples within static calorimeters is unexpectedly freezing at high temperatures is proved through a general numerical simulation of the isochoric cooling with chemical reactions between the gaseous products. A proprietary, direct linearization method of thermochemical computation is used that enables following any chemical reaction in equilibrium with high convergence. The observed chemical freezing within calorimeters is proved.