Six-degree-of-freedom hexapods for active damping and active isolation of vibrations

Abstract : As future astronomic missions will require more and more stringent resolution requirements, the high demand for an environment clean of vibrations and disturbance appears. This also leads to the need for high precision steering devices for fine pointing of sensitive optics with the highest possible accuracy. Several methods exist to reduce vibration levels: the first consists in isolating the sensitive system from the perturbation and the second in damping the structure vibration modes. Therefore, two Stewart platforms have been designed, manufactured and tested. The first is a soft hexapod that provides 6 degree-of-freedom (DOF) active isolation and the second is a stiff hexapod that provides active damping to whatever flexible payload attached/mounted to it. In addition, both hexapods have steering capabilities. 1. INTRODUCTION The two robots presented in this paper are based on the cubic configuration of Stewart platform [9], more details about cubic configuration are shown in [1]. The legs of the soft hexapod consist in soft electro-dynamic actuators. This hexapod consists mainly of two plates connected to each other by six legs. Each leg of the soft Stewart platform contains a voice coil electro-dynamic linear actuator, a force sensor and two flexible joints. This Stewart platform is aimed to be used in active vibration isolation. Only active control can achieve simultaneously high isolation performances (–40