Suspension device for low-frequency structures

摘要

A suspension device is provided for simulating the free-free boundary conditions of space for a low frequency structure. A support cable is connected at one end to the test structure and is vertically guided by a guiding ring. The other end of the cable is connected to a cam having an outer circumference which supports the cable. A drive axle passes through the cam center of rotation and is rotatably journalled in a suitable manner to a rigid structure. Two torsion springs are provided about the drive axle. One end of each spring is connected to a respective face of the cam and the other end is connected to the fixed support. The cam is shaped and the torsion springs selected such that Wr(t)=Ts(t), wherein W is the weight of the test structure; r(t) is the instantaneous moment arm defined as the perpendicular distance from the rotational center of the cam to the cable at time t, and Ts(t) is the total spring torque exerted by the two springs on the cam at time t. The test structure is accordingly vertically suspended by the cable and the instantaneous moment arm compensates for any increased spring torque arising from a vertical displacement of the test structure to simulate space conditions.