New design for a 6 dof vibration simulator with improved reliability and performance

Simulators are an indispensable tool to study present-day machinery dynamics in a repeatable way and under controlled laboratory conditions. In the past Stewart configurations are described thoroughly using inverse kinematics and forward kinematics. When optimising such a design for specific performance criteria, kinematics and hydraulic restrictions are to be taken into account. In this paper an already designed and constructed 6 degrees of freedom (dot) electro-hydraulic vibration test rig is virtually redesigned, constructed and validated using the Stewart configuration as a basis. The former structure has fundamental faults, which prohibit an optimised performance. An important weakness lies in the use of Hook's joints, which are too weak for the exerted forces and introduce an eigenfrequency that lies in the excitation band of the simulator. The aim is to find the optimal angle between ground and cylinder a that provides minimum rotation, force and torque within the Hook's joints, satisfies a number of performance criteria, respects the symmetry of the construction, tries to minimise the asymmetry in the cylinder movement and provides a movement of the platform with high resolution. An inverse kinematics and a dynamic model are constructed. The result is a vibration simulator with great stability and performance. (C) 2003 Elsevier Ltd. All rights reserved.