Double degree of freedom pendulum facility for the study of weak forces

Abstract

The LISA Test-Mass (TM) is sensitive to weak forces along all 6 Degrees of Freedom (DoFs). Extensive ground testing is required in order to evaluate the influence of crosstalks of various read-outs and actuators operating on different DoFs. To this purpose, and to better represent the flight conditions, we are developing a facility with 2 soft DoFs which consists of two stage roto-translational pendulum. This facility will measure the forces and stiffnesses simultaneously acting on the Test Mass along 2 different soft DoFs. The advantages with respect to a single DoF test bench are a more effective identification and debug of spurious effects between the TM and the capacitive position sensor surrounding it and the possibility to test actuation crosstalk with closed feedback loop. In particular, it allows us to measure the residual disturbance along one DoF when we close the control loop on the other one. © 2009 IOP Publishing Ltd.