Abstract: Methods and apparatus for generating a linear vibratory output force having a variable amplitude. The force is generated by the cooperation of four rotating eccentric masses that are grouped in two pairs of two masses. The masses in each pair are counter-rotating (i.e., they rotate at the same speed but in opposite directions). The phase relationship between the two pairs is adjustable. For example, the phase of one pair can be advanced while the phase of the other pair is retarded by an equal amount, thereby changing the amplitude of the output force without changing the direction along which the force acts, and also without changing its frequency if desired.

Abstract: Methods and apparatus for generating a linear vibratory output force having a variable amplitude. The force is generated by the cooperation of four rotating eccentric masses that are grouped in two pairs of two masses. The masses in each pair are counter-rotating (i.e., they rotate at the same speed but in opposite directions). The phase relationship between the two pairs is adjustable. For example, the phase of one pair can be advanced while the phase of the other pair is retarded by an equal amount, thereby changing the amplitude of the output force without changing the direction along which the force acts, and also without changing its frequency if desired.

Abstract: An electro-mechanical actuator has two motors which normally operate at the same speed and combine (sum) to move a load via a rotary actuator output member. If the motors begin to operate at different speeds, this indicates that the system has failed, and the output member is automatically decoupled from the remainder of the actuator. This leaves the output member free to rotate relative to the remainder of the actuator. The speeds of the motors are monitored by a differential mechanism which produces a rotary output proportional to the average of the two motor speeds. This average is normally the same as the speed of the output member. Decoupling of the output member occurs when this average deviates from the output member speed.