Abstract: A slippage sensor comprises a light-transmissive elastic component (14) defining an object-contactor face (15), input and output light guide (16a, 16b) defining a light transmission path through the component, and an indicator (19) connected with the output guide to detect transmission variations caused by elastic deformation of the component due, in turn, to relative slipping movement of an object (10) contacted thereby. In one form of sensor the input/output guides define a light path discontinous at the contactor face and to be completed by a surface (13) of the object as a reflector. In another form the component carries a reflector deformable therewith. In a further form the component is photoelastic and the input/output guides include polarisers. The sensor is useful to indicate when a minimum object gripping force is attained or it can indicate object characterisation.

Abstract: A drive mechanism for driving one or a plurality of displaceable elements around a closed path, such as a circle, constituted by a linear induction actuator associated with means for constraining the displaceable elements to move in the closed path. A capacitive feedback control system determines the position of the element or elements around the path and controls the windings of the linear induction actuator in dependence on an error signal generated therefrom. An open path drive mechanism having a plurality of linear induction actuators and a capacitive feedback control system is also encompassed by the invention as are hybrid linear induction motors using sets of arcuate linear induction actuators around the rim of a reaction member which drives an output shaft of the motor.

Abstract: A passive transponder, particularly for dental or medical applications, is described in which signals received by one or more receive resonant circuits are changed in frequency either up or down by a non-linear device coupled to one or more transmit resonant circuits. Each transmit resonant circuit includes a transducer whose impedance depends on a quantity whose value is to be transmitted and thus the frequency of signals received from the transponder depends on the value of the quantity.