Richard Ferguson wrote:
The application is not clear to me, but I can give you a way to do it. Years ago, I worked for a company that made aircraft simulators. The rudder pedals had to apply a force to the pilot reflecting the conditions of flight. The torque sensor was a rod of 1/4" spring steel about 4' long, with a servo pot at each end. One end of the rod had a worm gear/screw, driven by a Bosch weed whacker PM motor. The other end of the rod had a pulley around which the cables to the rudder pedals were wound. As torque was applied via the rudder pedals, the torque bar would twist. The twist puts the pots at different settings. The difference in resistance is proportional to torque. That torque value, along with the aircraft simulation inputs, was used to control the motor. The motor control was cheap and elegant. The motor was controlled by a triac, running off the AC line. The motor controller determined which half of the AC wave would be gated to the motor, giving motor direction, and the percentage of that half wave, to control drive. In operation, "on the ground" you could work the rudder pedals back and forth with little force as the motor servoed to put no torque on the rod. As "airspeed" increased, more force would be required to push the rudder. In a fault condition (one of the situations had the instructor sneaking over to pull the fuel cutoff for one of the engines)the pedal would come at you with (IIRC) 150 ft/lbs of force. It was inexpensive, simple, and worked very well. The system was designed by Jim Patmore, who was a genius.
Kevin Gallimore