A novel model for layer jamming-based continuum robots

Continuum robots with variable stiffness have gained wide popularity in the last decade. Layer jamming (LJ) has emerged as a simple and efficient technique to achieve tunable stiffness for continuum robots. Despite its merits, the development of a control-oriented dynamical model tailored for this specific class of robots remains an open problem in the literature. This paper aims to present the first solution, to the best of our knowledge, to close the gap. We propose an energy-based model that is integrated with the LuGre frictional model for LJ-based continuum robots. Then, we take a comprehensive theoretical analysis for this model, focusing on two fundamental characteristics of LJ-based continuum robots: shape locking and adjustable stiffness. To validate the modeling approach and theoretical results, a series of experiments using our \textit{OctRobot-I} continuum robotic platform was conducted. The results show that the proposed model is capable of interpreting and predicting the dynamical behaviors in LJ-based continuum robots

Simultaneous Position-and-Stiffness Control of Underactuated Antagonistic Tendon-Driven Continuum Robots

Continuum robots have gained widespread popularity due to their inherent compliance and flexibility, particularly their adjustable levels of stiffness for various application scenarios. Despite efforts to dynamic modeling and control synthesis over the past decade, few studies have focused on incorporating stiffness regulation in their feedback control design; however, this is one of the initial motivations to develop continuum robots. This paper aims to address the crucial challenge of controlling both the position and stiffness of a class of highly underactuated continuum robots that are actuated by antagonistic tendons. To this end, the first step involves presenting a high-dimensional rigid-link dynamical model that can analyze the open-loop stiffening of tendon-driven continuum robots. Based on this model, we propose a novel passivity-based position-and-stiffness controller adheres to the non-negative tension constraint. To demonstrate the effectiveness of our approach, we tested the theoretical results on our continuum robot, and the experimental results show the efficacy and precise performance of the proposed methodology

Performance optimization design and analysis of bearingless induction motor with different magnetic slot wedges

This paper investigates the application of using magnetic wedges in a semi-closed slot bearingless induction (BI) motor. In this strategy, the electrical loss of the motor can be reduced, improving the overall efficiency. At the same time, the temperature rise of the winding is reduced, and the vibration and noise levels are greatly depressed, which prolong the service life of the motor. First, the principle of BI motor operation is introduced. Second, the different magnetic permeability and geometric shape of the magnetic wedge are taken into consideration during the analysis the proposed BI motor. Then, the performance of BI motor with magnetic wedge is analyzed by finite element method. Finally, the results show that too high relative permeability materials can degrade the performance of the BI motor, thus, the use of suitable permeable magnetic wedge is reasonable. After adding the optimal magnetic wedge, the torque ripple, motor efficiency and the suspension force of the BI motor are optimized. The use of magnetic wedges has economic advantages and is of great significance for improving the performance of BI motors. Keywords: Bearingless motor, Magnetic wedges, Induction motor, Finite element analysi