Conference paper

Orion MinAngle: A flexure-based, double-tilting parallel kinematics for ultra-high precision applications requiring high angles of rotation

If you need to design ultra-high precision devices for mechanisms with multiple axes there are not a lot of ways leading around flexure-based joints. Using this type of articulations totally eliminates backlash and friction and is, by this, providing an accurate mechanical foundation for your device. The most important disadvantage of this technology is the low range of motion. The basic joint types, blades and circular hinges, have angular limits which strongly depend on the targeted stiffness, the quantity of motion cycles and the elastic limit of the material. This article will introduce novel parallel kinematics which are totally based on 1 dof flexures and whose angular range of motion is determined by twice the range of the single joint. It is a 3 dof parallel kinematic based on 3 identical kinematic chains which produce movements in θx, θy and z. The model has been designed to constitute the left hand of a machine tool that requires orienting the workpiece in a very precise manner and with high rotation amplitudes. Additionally to this it presents very interesting characteristics of Remote-Center-of-Motion (RCM) mechanisms. This is a vital feature for applications where the linear movements are highly limited and should not be consumed by parasitic movements of other axes. All these features, combined with the advantages of parallel kinematics, make the Orion MinAngle a very interesting concept. The model has been designed with joints achieving ±7.6° leading to an output angle of ±15° on both rotation axes. The study has shown really promising results concerning the mechanical properties, the high rotation angles and the RCM capabilities. The paper presents the kinematics and its optimization method which is used to guarantee a nearly perfect division of the output angle on all pivots of the mechanism. The next chapters talk about the dimensioning of the flexible joints and generally about the design of the robot. The last part of the paper verifies the optimization trough kinematic modeling of the robot and computes the mechanical properties like stiffness, internal strains and mechanical Eigenfrequencies. At the end we propose a realistic application as a 5-axes parallel-kinematic machine tool and we come to a conclusion about the potential of the Orion MinAngle mechanism.

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