On Crossley's contribution to the development of graph based algorithms for the analysis of mechanisms and gear trains

This paper celebrates a particular branch of Crossley's early work dedicated to Mechanism Science, which deals with a rigorous introduction of Graph Theory to the study of some fundamental and intrinsic properties of kinematic chains and mechanisms. Although such idea gave its main outcome in Type and Number Synthesis (which has been much better and extensively described in another paper of the present special issue) some other intriguing side effects appeared, later in Mechanism Science, which yielded several results, and are still in the center of research and industrial world interest, such as, to name but a few, the automatic generation of the equations governing kinematic, static force and dynamic analysis of mechanisms and geared trains, the power flow analysis, the computation of the efficiency and, finally, the never fully explored structure-to-function mapping, which the present contribution points out to be still a challenge in the field

Control and virtual reality simulation of tendon driven mechanisms

In this paper the authors present a control strategy for tendon driven mechanisms. The aim of the control system is to find the correct torques which the motors have to exert to make the end effector describe a specific trajectory. In robotic assemblies this problem is often solved with closed loop algorithm, but here a simpler method, based on a open loop strategy, is developed. The difficulties in the actuation are in keeping the belt tight during all working conditions. So an innovative solution of this problem is presented here. This methodology can be easily applied in real time monitoring or very fast operations. For this reason several virtual reality simulations, developed using codes written in Virtual Reality Markup Language, are also presented. This approach is very efficient because it requires a very low cpu computation time, small size files, and the manipulator can be easily put into different simulated scenarios

Optimization of a High–Speed Deployment Slider–Crank Mechanism: A Design Charts Approach

Mechanical and aerospace applications often require that mechanisms deploy in a quick stable and reliable way. The objective of this study is to implement a general optimization procedure to perform a first stage conceptual design of HSD mechanisms, focusing on both kinematics and dynamics. In particular, the authors will focus on the development of design charts. In the very first part of the work, a parametric lumped-mass system will be modeled in order to reduce the number of parameters for the synthesis phase. A correlation will be established between geometry, inertia and initial position to guarantee the maximum value of acceleration during deployment of the deployable arm by means of the principle of virtual work. In the second part of this work, the influence of important factors such as friction and joint clearance on the overall dynamics of the system will be investigated. Finally, a coupled dynamic and structural analysis of the helical spring, that actuates the mechanism, will be carried out in order to achieve optimal performance. The developed charts will also take into account the space limitation requirement, that are often needed for both aerospace and mechanical applications. A final example will summarize all the points covered by this research effort. Results will be validated using the commercial software ABAQUS.</jats:p