A New Robotic Hand Based on the Design of Fingers With Spatial Motions

This article presents a new hand architecture with three under-actuated fingers. Each finger performs spatial movements to achieve more complex and varied grasping than the existing planar-movement fingers. The purpose of this hand is to grasp complex-shaped workpieces as they leave the machining centres. Among the taxonomy of grips, cylindrical and spherical grips are often used to grasp heavy objects. A combination of these two modes makes it possible to capture most of the workpieces machined with 5-axis machines. However, the change in grasping mode requires the fingers to reconfigure themselves to perform spatial movements. This solution requires the addition of two or three actuators to change the position of the fingers and requires sensors to recognize the shape of the workpiece and determine the type of grasp to be used. This article proposes to extend the notion of under-actuated fingers to spatial movements. After a presentation of the kinematics of the fingers, the problem of stability is discussed as well as the transmission of forces in this mechanism. The complete approach for calculating the stability conditions is presented from the study of Jacobian force transmission matrices. CAD representations of the hand and its behavior in spherical and cylindrical grips are presented.

2D Positioning Control System for the Planar Motion of a Nanopositioning Platform

A novel nanopositioning platform (referred as NanoPla) in development has been designed to achieve nanometre resolution in a large working range of 50 mm × 50 mm. Two-dimensional (2D) movement is performed by four custom-made Halbach linear motors, and a 2D laser system provides positioning feedback, while the moving part of the platform is levitating and unguided. For control hardware, this work proposes the use of a commercial generic solution, in contrast to other systems where the control hardware and software are specifically designed for that purpose. In a previous paper based on this research, the control system of one linear motor implemented in selected commercial hardware was presented. In this study, the developed control system is extended to the four motors of the nanopositioning platform to generate 2D planar movement in the whole working range of the nanopositioning platform. In addition, the positioning uncertainty of the control system is assessed. The obtained results satisfy the working requirements of the NanoPla, achieving a positioning uncertainty of ±0.5 µm along the whole working range.

The MemoSlide: An explorative study into a novel mechanical follow-the-leader mechanism

Follow-the-leader propagation allows for the insertion of flexible surgical instruments along curved paths, reducing the access required for natural orifice transluminal endoscopic surgery. Currently, the most promising follow-the-leader instruments use the alternating memory method containing two mechanical memory-banks for controlling the motion of the flexible shaft, which reduces the number of actuators to a minimum. These instruments do, however, require concentric structures inside the shaft, limiting its miniaturization. The goal of this research was, therefore, to develop a mechanism conforming the principles of the alternating memory method that could be located at the controller-side instead of inside the shaft of the instrument, which is positioned outside the patient and is therefore less restricted in size. First, the three-dimensional motion of the shaft was decoupled into movement in a horizontal and vertical plane, which allowed for a relatively simple planar alternating memory mechanism design for controlling planar follow-the-leader motion. Next, the planar movement of the alternating memory mechanism was discretized, increasing its resilience to errors. The resulting alternating memory mechanism was incorporated and tested in a proof-of-concept prototype called the Memo Slide. This prototype does not include a flexible shaft, but was fully focused on proving the function of the alternating memory mechanism. Evaluation of the Memo Slide shows the mechanism to work very well, being able to transfer any planar path that lays within its physical boundaries along the body of the mechanism without accumulating errors.

Cooperative Control for Satellite Formation Reconfiguration via Cyclic Pursuit Strategy

This paper investigates a methodology for group coordination and cooperative control of satellites with the aim to achieve formation reconfiguration such as radius enlargement and phase angle adjustment. The proposed approach separates the control law into two distinct stages: planar movement control and orthogonal displacement suppression. The in plane approach is based on a cyclic pursuit strategy, where satellite i pursues satellite i +1. For phase angle adjustment, a control law that makes use of beacons guidance is synthesized to maintain the circling centre stationary. In the orthogonal direction, a linear feed back control on displacement and velocity is used. Simulation of two missions with low thrust are provided, which high light the over all effectiveness of the proposed approach.

Study on Hydrodunamic Coefficients of Mini Automatic Underwater Vehicle

Maneuverability is an important part of the vehicle’s general abilities.This paper uses sofware Fluent to simulate the planar movement mechanism(PMM) experiment while turbulence modle is adoped.The results of steady-state tests and unsteady-state tests could be analyzed to the hydrodunamic coefficients of a Mini Automatic Underwater Vehicle(AUV)and the dymatic mesh is adoped to simulate the motion of heave,sway,pitch,yaw.Finally, the motion simulation platform was built with the hydrodunamic coefficients and the motion performance of the vehicle was analyzed.