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Sensors for flexion and calibration techniques

posted Jul 28, 2012, 10:03 PM by Gabriella Levine   [ updated Jul 28, 2012, 10:04 PM ]
I still have some questions about steppers which I need to address this week:
1. is the amperage too high? 
2. can we find the correct gear box mechanism? How will we mount the gears? 
3. is the speed going to be too slow?  (RPM is inversely proportional to torque on steppers)
4. Do i have to limit current, and if so how and how much? Will 12 V be good? 
5. how can we have a central calibration point....

which leads me to: 

How will we calibrate the center of the boat, or that the boat is TOO flexed, or that the sail is being pulled too far? What happens if the motors stall and get out uncalibrated on the open water? 

Calibration techniques for both the sail and for the body flexion:

1. Flex Sensor :  This sensor could be on either side of the boat. As the sensor is flexed, the resistance increases. Therefore we can program an equilibrium point into each side, to calibrate center. 
2. Stretch sensor: changes resistance when stretched. Similarly, this can be placed in between segments of the boat on either side, to allow for an equilibrium point to be known when both opposing sensors are equal. 

3. mechanical switch on either side of the sail that gets triggered , which can act like a limit switch if the sail is pulled too far. 
4. Hall effect sensor can be between each segment to determine the proximity of each segment from the next, and they can be equalized this way. 

5. Infrared or photo-interrupter can aid for positional control of the boom or the winch. 

6. A rotary encoder on the motor shaft can be a counter for calibrating the turns of the motor, but this won't actually give positional feedback. I also would have to investigate mounting techniques, and this would be better if we have a DC motor. 
7 an optical sensor / phototransistor can be mounted on the inside of the winch to determine number of rotations and rotational speed

Any more ideas on what would work?