Double pendulum balanced by counter-rotary counter-masses as useful element for synthesis of dynamically balanced mechanisms

Complete dynamic balancing principles still cannot avoid a substantial increase of mass and inertia. In addition, the conditions for dynamic balance and the inertia equations can be complicated to derive. This article shows how a double pendulum can be fully dynamically balanced by using counter-rotary counter-masses (CRCMs) for reduced additional mass and inertia. New CRCM-configurations were derived that have a low inertia, a single CRCM or have all CRCMs near the base. This article also shows how a CRCM-balanced double pendulum can be used as building element in the synthesis of balanced mechanisms for which the balancing conditions and inertia equations can be written down quickly. For constrained mechanisms the procedure is to first write down the known balancing conditions and inertia equations for the balanced double pendula and subsequently substitute the kinematic relations

Synthesis method for linkages with conter of mass at invariant link point-Pantograph based mechnisms

This paper deals with the synthesis of the motion of the center of mass (CoM) of linkages as being a stationary or invariant point at one of its links. This is of importance for the design of inherently shaking force balanced mechanisms, static balancing, and other branches of mechanical synthesis. For this purpose Fischer's mechanism is investigated as being a composition of pantographs. It can be shown that linkages that are composed of pantographs and of which all links have an arbitrary CoM can be inherently balanced for which Fischer's method is a useful tool. To calculate the principal dimensions for which linkages have their CoM at an invariant link point, an approach based on linear momentum is proposed. With this approach it is possible to investigate each degree-of-freedom individually. Equivalent Linear Momentum Systems are proposed to facilitate the calculations in order to use different convenient reference frames. The method is applied to planar linkages with revolute joints, however it also applies to linkages with other types of joints. As a practical example a shaking force and shaking moment balanced 2-DoF grasper mechanism is derived. -------------------------------------------------------------------------------

A layered approach to model interconnected infrastructure and its significance for asset management

Physical infrastructures facilitate much of societal and economic wellbeing of countries, regions and urban areas. In our increasingly urbanizing world, infrastructures in urban areas are densely located and interconnected. The effects of this interconnectedness are being studied increasingly, particularly in light of climate change effects. In this paper, we develop an agent-based simulation model that allows us to study interconnected infrastructure. We present a layered approach that is analogous to GIS overlay approaches, which allows us to integrate representations of different infrastructures. We explore how this approach can help asset managers to gain insights in interconnected infrastructure by estimating their total damage and repair requirements during a flood event. The results show a difference in these estimates, when compared to non-integrated models, highlighting the need for asset managers to consider interconnectedness in infrastructure

Generic method for deriving the general shaking force balance conditions of parallel manipulators with application to a redundant planar 4-RRR parallel manipulator

This paper proposes a generic method for deriving\ud the general shaking force balance conditions of parallel\ud manipulators. Instead of considering the balancing of a parallel\ud manipulator link-by-link or leg-by-leg, the architecture is\ud considered altogether.\ud The first step is to write the linear momentum of each element.\ud The second step is to substitute the derivatives of the\ud loop equations, by which the general force balance conditions\ud are obtained. Subsequently specific kinematic conditions are\ud investigated in order to find advantageous, simple balance solutions.\ud As an example, the method is applied to a planar 4-RRR parallel\ud manipulator, for which the force balance conditions and\ud solutions are discussed and illustrated for each step respectively.\ud By including the loop equations, linear relations of the\ud motion among mechanism elements lead to an increase of balance\ud possibilities.For specific kinematic conditions, additional\ud linear relations among the motion of mechanism elements may\ud be obtained, resulting in another increase of balance possibilities.\ud For the latter, symmetric motion is an important feature\ud for which a 4-RRR manipulator is advantageou

Design and experimental evaluation of a dynamically balanced redundant planar 4-RRR parallel manipulator

International audienceShaking forces and shaking moments in high speed parallel manipulators are a significant cause of base vibrations. These vibrations can be eliminated by designing the manipulator to be shaking-force balanced and shaking-moment balanced. In this article an approach for the design and for the evaluation of high speed dynamically balanced parallel manipulators is presented and applied for a comparative experimental investigation of the balanced and the unbalanced DUAL-V planar 4-RRR parallel manipulator. For precise simulation of the manipulator motion, the inverse dynamic model of the manipulator is derived and validated. Experiments show that the balanced manipulator has up to 97% lower shaking forces and up to a 96% lower shaking moment. For small inaccuracies of the counter-masses or for a small unbalanced payload on the platform, base vibrations may be considerable for high speed manipulation, however their values remain significantly low as compared to the unbalanced manipulator. For the balanced manipulator the actuator torques are about 1.6 times higher and the bearing forces are about 71% lower as compared to the unbalanced manipulator

Pituitary adenomas, some diagnostic and therapeutical aspects

The treatment of almost all types of pituitary adenomas has changed considerably in recent years. New types of drugs as well as improved application forms of older drug therapies are now becoming more and more available for everyday treatment of patients with these relatively rare diseases. For the most frequently occurring pituitary adenomas the drugs of first choice are described, as well as other available treatments, their indications and efficacies. Also the main side-effects are described