This study focuses on Physical Human-Robot Interaction (pHRI) tasks that require a close coupling between safety constraints and compliance with human intentions. To address this, the authors propose a novel switched admittance controller for an n-link manipulator to comply with external forces while ensuring safety in the workspace. The controller switches between two reference models to generate a reference trajectory that maintains the safety constraints. Stability analysis of the switched reference model is performed by selecting an appropriate Common Quadratic Lyapunov Function (CQLF), which ensures the asymptotic convergence of the trajectory tracking error. The effectiveness of the proposed controller is demonstrated through simulation on a 4-DOF SCARA (RRPR) robot manipulator.

Time delay analysis is very crucial when it comes to the synchronization of chaotic systems. All practical dynamical systems are described by differential equations, hence the presence of time delay in dynamics becomes a pivotal part of the system analysis. So, in this article, an attempt has been made to study the synchronization problem of two identical same-ordered time-delayed chaotic systems, in strict-feedback form as described in (2) and (3) in master and slave configuration. Unlike other conventional nonlinear control techniques, the back-stepping control design strategy is used to serve the purpose of synchronization. The main advantage of using the back-stepping control technique is that it utilizes only a single scalar controller to attain synchronization among different chaotic systems. A generalized control function$u\in R$is designed for the same. For verification of the theoretical results, the 3D time-delayed Genesio-Tesi chaotic system is considered both a master and slave system. Simulation results are provided to support the proposition.

This article studies the behaviour of switched mechanical systems with respect to periodic perturbations. The switching considered is due to the one-sided stiffness present in many practical engineering systems. Due to one-sided stiffness, the overall system behaves like nonlinear dynamics. One peculiar phenomenon of nonlinear dynamics is the presence of harmonics in the response along with fundamental components when excited with periodic input. Hence, the response of these types of mechanical systems contains k-periodic solutions$(\mathrm{k}=2,3,4)$. Existence of these leads to the cause of unintended vibrations, which is adversarial for the system. In this paper, Contraction theory has been explored to suppress the components of k-periodic solutions in the output. The contractivity of the overall system ensures entrainment property which makes the output frequency the same as that of the input perturbation. A matrix measure is used to verify the Contraction of the overall switched system, which suggests the parameter regime for entrainment. Simulation results are attached to validate the proposition.