A novel suspension mechanism has been developed and constructed at the BIPM. It has a dual purpose: to adjust the initial alignment of the coil with respect to the magnet and to correct the trajectory defects of the travelling coil.
The alignment mechanism is based on servo-controlled push-pull piezoelectric actuators, repeatability of positioning is currently better than 1 µm. Following testing, the system will be integrated into the watt balance.
Dynamic alignment system of the watt balance coil
4 piezo actuators (A) for horizontal alignment (C)
4 piezo actuators (B) for angular alignment (D)
Coil model (E)