Abstract: An electronic system is provided for stimulating a segmented transducer with resonant electrical signals to produce a nonsinusoidal transducer output. In an illustrative embodiment, the transducer comprises a segmented piezoelectric actuator. The actuator comprises stacked piezoelectric dimorphs forming the actuator segments, each of which reacts electrically as a capacitance. Each segment (capacitance) is connected in a loop in electrical series with an external capacitor or a corresponding segment of a second actuator. An electrical controller stimulates each loop with a separate resonant electrical signal related to the others in frequency, phase, amplitude, and polarity. The resulting output of each actuator is the vector sum of the mechanical outputs of the individual dimorphs of that actuator. In an ideal resonant drive system for a segmented transducer, the only electrical energy used is that which is converted directly to mechanical work by the actuator.

Abstract: A direct current traveling wave motor generates motive force by utilizing shear deformation resulting from electrical contact between a rolling element and a layer of material that experiences shear deformation in response to an applied electric field. In a rotary piezoelectric embodiment, rotation of a motor shaft results from the non-uniform electric field intensity around the contacts between rollers surrounding the shaft and an outer race of piezoelectric material that undergoes shear deformation. Rotation occurs as the rollers roll down the faces of piezoelectric shear waves that travel with the rollers. The rollers perform the function of commutators, but without sliding friction, and they eliminate the need for traditional roller bearings. Zero clearance between motor parts results in shaft stiffness that allows precise positioning and high speed operation.

Abstract: An electric traction motor provides forcible rotary or linear positioning of a motor shaft by pairs of actuators that are electrically stimulated to produce tractive cyclical walking. Smooth walking actuators provide high mechanical efficiency and long life by eliminating sliding friction. The actuators are stimulated by a high efficiency electrical drive system to position relatively large-area traction members that match the speed of the motor shaft. The preferred embodiment comprises piezoelectric actuators having layers of shear deformation piezoelectric material. Conventional bearings and lubrication are not required, and embodiments of the motor can be constructed to operate satisfactorily in intense magnetic fields and severe ionizing radiation. The traction motor can range in scale from microscopic to very large, and positioning accuracy on the order of nanometers has been demonstrated.

Abstract: A light weight, efficient, and compact piezoelectric rotary union system is provided for joining structures such as space station modules. The system comprises piezoelectric actuators attached to a first structure that engage and rotate a ring attached to a second structure. The actuators position and rotate the ring by non-sliding, smooth walking motion that provides high mechanical efficiency, long life, and negligible electrical noise. Electrical conductors embedded in the ring and the actuator traction surfaces transmit electric currents and signals between the structures. Moderate traction pressure and large contact area substantially eliminate contact heating and associated vacuum welding. The piezoelectric actuators generate relatively large translational forces at relatively low speeds. The absence of conventional rolling bearings eases connection and disconnection of the rotary union.