Nanoradian digital stabilization of a suspended table for scientific experiments

Digital control design of a suspended table for fine scientific experiments is presented. The problem was suggested by an experiment to measure the universal gravitation constant G, requiring two residual rotations of the table with respect to the horizontal plane to be below 1 nrad. The problem was tackled by assuming a 2D clinometer and accelerometers as transducers. As actuators, linear electric moving-coil motors are necessary to avoid contact between the building and the table. The digital control was designed and tested using a fine numerical simulator of the plant and of environmental disturbances. The simulation tests of a first simplified version of the Digital Control Unit showed that the requirements may be met.