Design Strategies for the Geometric Synthesis of Orthoglide-type Mechanisms

TL;DR

This paper presents three analytical design strategies for optimizing Orthoglide-type mechanisms, balancing workspace size, kinematic performance, and structural stiffness for rapid machining applications.

Contribution

It introduces new analytical methods to define Orthoglide parameters based on workspace and performance bounds, achieving Pareto-optimal designs.

Findings

Strategies produce Pareto-optimal solutions

Designs balance workspace, performance, and stiffness

Numerical examples validate the approach

Abstract

The paper addresses the geometric synthesis of Orthoglide-type mechanism, a family of 3-DOF parallel manipulators for rapid machining applications, which combine advantages of both serial mechanisms and parallel kinematic architectures. These manipulators possess quasi-isotropic kinematic performances and are made up of three actuated fixed prismatic joints, which are mutually orthogonal and connected to a mobile platform via three parallelogram chains. The platform moves in the Cartesian space with fixed orientation, similar to conventional XYZ-machine. Three strategies have been proposed to define the Orthoglide geometric parameters (manipulator link lengths and actuated joint limits) as functions of a cubic workspace size and dextrous properties expressed by bounds on the velocity transmission factors, manipulability or the Jacobian condition number. Low inertia and intrinsic stiffness have been set as additional design goals expressed by the minimal link length requirement. For each design strategy, analytical expressions for computing the Orthoglide parameters are proposed. It is showed that the proposed strategies yield Pareto-optimal solutions, which differ by the kinematic performances outside the prescribed Cartesian cube (but within the workspace bounded by the actuated joint limits). The proposed technique is illustrated with numerical examples for the Orthoglide prototype design.