Abstract: A linear force actuator system for stabilizing a support structure employs a linear dc motor whose primary winding is driven by a pulse width modulation control signal representative of a force input, through which the secondary member of the motor which acts as an inertial mass, is to be controllably translated. For improved control accuracy, the actuator system of the invention employs a pair of feedback loops, one of which monitors the current in the motor's primary winding to maintain a constant force output to the secondary member and a secondary of which monitors long term deviations from the center of the secondary member and corrects for centering offsets. An opto-electronic position sensing arrangement monitors the movement of the secondary member whereby precise control of commutation of the coils of the primary winding and a smooth translation of the secondary member are obtained.

Abstract: A binary bit pattern is reconstructed from a block of analog signals corresponding to the number of known bit positions of the pattern being reconstructed. The analog signals, which may take the form of light intensity signals, vary in signal level with the binary level represented as well as with a characteristic which causes the signal levels of the analog signals to vary in a known manner as a function of bit position. In reconstructing the bit pattern, an output signal is developed having a value dependent upon that of at least one of the analog signals which has a known bit level reconstruction. This signal is used for providing a variable threshold having a value which varies in dependence upon the outut signal as modified by a modifying factor which varies in the known manner as a function of bit position. Bit decision circuitry includes a comparator for sequentially comparing the analog signals with the variable threshold to provide bit decision indications.