This paper presents a new improved nonlinear tracking differentiator (INTD) with hyperbolic tangent function in the state-space system. The stability and convergence of the INTD are thoroughly investigated and proved. Through the error analysis, the proposed INTD can extract differentiation of any piecewise smooth nonlinear signal to reach a high accuracy. The improved tracking differentiator (...

The nonlinear system becomes an area with numerous investigations over the past decades. The conventional modal analysis could not be  applied on nonlinear continuous system which makes it impossible to construct the reduced order models and obtain system response based on limited number of measurement points. Nonlinear normal modes provide a useful tool for extending modal analysis to nonlinea...

Series Elastic Actuators have linear springs intentionally placed in series between the motor and actuator output. The spring strain is measured to get an accurate estimate of force. Despite using a transmission to achieve high force/mass and high power/mass, the spring allows for good force control, high force fidelity, minimum impedance, and large dynamic range. A second order linear actuator...

In this paper, a simplified spring-dashpot model is proposed to represent the complicated nonlinear response of some viscoelastic materials. Recently, the viscoelastic modeling has been adopted by many researchers to characterize some parts of the human body in bioengineering and to simulate many material properties in mechanical engineering, electronic engineering and construction engineering....

This paper presents the stability analysis of a fuzzymodel-based control system consisting of a nonlinear plant and a nonlinear state feedback controller and the design of the nonlinear gains of the controller. The nonlinear plant is represented by a fuzzy model having rules. A nonlinear state feedback controller is designed to close the feedback loop. Under this design, the stability condition...

This paper presents vibration analysis of an autoparametric pendulum-like mechanism subjected to harmonic excitation. To improve dynamics and control motions, a new suspension composed of a semiactive magnetorheological damper and a nonlinear spring is applied. The influence of essential parameters such as the nonlinear damping or stiffness on vibration, near the main parametric resonance regio...

In this research, using the Modified Compression Field Theory (MCFT), a new model is proposed to predict the behavior of reinforced concrete coupling beams. The model is able to consider the effects of shear and axial forces and bending moment, simultaneously. The proposed model includes a nonlinear shear spring, an axial spring and some nonlinear springs for considering bending deformations. I...

this work is conducted to obtain mechanical properties of microtubule. for this aim, interaction energy in alpha-beta, beta-alpha, alpha-alpha, and beta-beta dimers was calculated using the molecular dynamic simulation. force-distance diagrams for these dimers were obtained using the relation between potential energy and force. afterwards, instead of each tubulin, one sphere with 55 kda weight ...

In this paper, we present a cable mechanism which synthesizes a nonlinear rotational spring from a linear spring. The nonlinearity is realized by winding the cable around a spool which has a varying radius. We show that for a given nonlinear torque profile (synthesis objective) there is an explicit geometric expression of the shape of the spool which synthesizes this profile. We present the geo...