Abstract: A method and apparatus for accurately and reliably positioning an actuator arm (12) is disclosed. The actuator arm (12) is driven by a conventional DC motor (38). The conductors which supply current to the motor (38) serve as primary windings (60) of a current transformer (58). The signal induced on secondary windings (62) of the transformer (58) responds to fluctuations in average current flowing in the motor (38). These fluctuations are amplified (64) and filtered (66) so that an AC burst (68) is produced in response to each commutation of the motor (38). The AC burst (68) triggers a one-shot timing circuit (72), which generates a pulse that remains active until the AC burst (68) has decayed. The pulse disappears prior to a subsequent commutation of the motor (38). Thus, one pulse is generated for each commutation of motor (38). A counter (76) is clocked by these pulses. The counter (76) increments when the motor (38) moves in one direction and decrements when the motor (38) moves in the opposing direction.

Abstract: An arrangement for sensing rotational torque in an exercise machine utilizes a torque measuring collar, which is generally tubular with a flange at each end. One flange is mounted to a stationary member, such as the frame of a machine. A shaft which is to rotate when the force is applied extends through the tubular collar to a gear box which itself is mounted only to the other flange of the torque collar and is therefore freely rotatable. The flange of the collar which is mounted to the gear box attempts to rotate in response to the torque (force) applied to the machine shaft by the user. This causes the collar to rotationally deform, i.e. twist, in the area between its two flanges. This torque proportional deformation effect occurs independent of the rotation position of the shaft as it rotates either direction through continuous circular motion.