This paper proposes a novel exponential hyper–chaotic system with complex dynamic behaviors. It also analyzes the chaotic attractor, bifurcation diagram, equilibrium points, Poincare map, Kaplan–Yorke dimension, and Lyapunov exponent behaviors. A fast terminal sliding mode control scheme is then designed to ensure the fast synchronization and stability of the new exponential hyper–chaotic system. Stability analysis was performed using the Lyapunov stability theory. One of the main features of the proposed controller is the finite time stability of the terminal sliding surface designed with high–order power function of error and derivative of error. The approach was implemented for image cryptosystem. Color image encryption was carried out to confirm the performance of the new hyper–chaotic system. For image encryption, the DNA encryption-based RGB algorithm was used. Performance assessment of the proposed approach confirmed the ability of the proposed hyper–chaotic system to increase the security of image encryption.

The 6061-T651 aluminium alloy is one of the most common aluminium alloys for marine components and general structures. The stress intensity factor (SIF) is an important parameter for estimating the life of the cracked structure. In this paper, the stress intensity factors of a slant-cracked plate, which is made of 6061-T651 aluminum, have been calculated using extended finite element method (XFEM) and finite element method (FEM) in ABAQUS software and the results were compared with theoretical values. Numerical values obtained from these two methods were close to the theoretical values. In simulations of crack growth at different crack angles, the crack propagation angle values were closer to the theoretical values in XFEM method. Also, the accuracy and validity of fatigue crack growth curve were much closer to the theoretical graph in XFEM than the FEM. Therefore, in this paper the capabilities of XFEM were realized in analyzing issues such as cracks.

This work proposes a novel impedance control strategy for a delayed bilateral tele-surgery system to perform a drilling process during spinal surgery. In the new designed control scheme, regarding a desired impedance model for master and slave robot, an especial dynamic characteristic at the surgeon and master as well as slave and vertebra interface is designed. Two desired impedance models are proposed for the master and slave robots such that: (a) the salve robot that holds the drilling device should track the master path but complies with the reaction force of the vertebra, and (b) the surgeon should receive feedback from the slave-vertebra interaction force via the master robot. These main objectives are attained by proper adjustment in the proposed impedance model, which does not require any direct measurement of vertebra reflections. Then, the impedance model is put into a proper sliding mode controller to cope with the modeling uncertainties in the slave side. Consequently, the absolute stability concept is utilized to investigate closed-loop system stability and transparency. Finally, the control scheme is implemented on one degree of freedom robotic manipulators as master and slave robot. Experimental results demonstrate the efficiency of the designed impedance control scheme in the presence of modeling uncertainties.

Performing various experimental, theoretical, and numerical investigations for better understanding of behavioural characteristics of metals under impact loading is of primary importance. In this paper, application of smoothed particle hydrodynamics (SPH) method in impact mechanics is discussed and effective parameters on impact strength of an aluminum plate are investigated. To evaluate the accuracy of smoothed particle hydrodynamics method for simulating impact, Recht and Ipson model is first provided thoroughly for both Rosenberg analytical model and smoothed particle hydrodynamics method, and then plots of initial velocity-residual velocity and initial velocity-absorbed energy for target of aluminum 6061-T651 are presented. The derived information and simulation results expresses that the maximum error percentage of smoothed particle hydrodynamics method in compared with Rosenberg analytical model is within an acceptable range. Therefore, the results of smoothed particle hydrodynamics method verify the Rosenberg analytical model with high accuracy. Results reveal that higher initial impact velocity decreases the time of projectile penetration, and so penetration depth and length as well as the local damage rate of plate increases.

Teleoperation systems have been presented to handle objects in environments in which the presence of operators are impracticable, unsafe or less effective. In this paper, a passive control strategy employing the new outputs to state synchronization of the master and slave robots is developed to attain position coordination during contact tasks. The proposed control scheme includes position signals plus force signals. However, force measurement in such applications is a major limitation. Therefore, a modified force estimation algorithm is proposed to predict external forces applied on the master and slave robots. The closed-loop bilateral teleoperation system is investigated by employing Lyapunov stability criteria. Finally, the experimental results demonstrate the efficiency of the proposed control scheme. It is observed that, in the presence of the estimated external forces in the control scheme, the slave robot follows the master position in both free and contact motion, and force reflecting occurs properly as well. Moreover, it is verified that the external forces are estimated appropriately through the proposed force estimation algorithm.

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