Could you share more about your experience with elastic actuators? What did your hardware look like? I'm working on something similar, and would love your input.
Using a flexible servo horn, this allows some degree of deformation when torque is applied. Embed a 1/32" neodymium
magnet in the horn, and a magnetic rotary position sensor in the driven part. As resistance to movement ("torque") increases, the flexible servo horn twists/deflects, angle of difference between the two parts changes and this can be detected by the magnetic sensor.
Picture a torque strain gauge, the way the needle deflects from the centerline of the gauge. This is similar but we're doing so in an radial (edit:removed axial) and not linear sense.
Different amounts of sensitivity are obtained by printing different spoke stiffness on the horn.
Result is a compact, modular torque sensor for about $2 in parts.
Feed the results to a PID look and you have a nice controller that can tell me when a robot leg is bearing a load, or is jammed, etc. This is essential to proper gait. Otherwise your robot is simply an electronic marionette.
One of the big challenges was getting 16 additional 16bit voltage reads back to my Rpi over i2c bus. (one value for each servo)
https://www.adafruit.com/product/1085
jackhack|8 years ago
Using a flexible servo horn, this allows some degree of deformation when torque is applied. Embed a 1/32" neodymium magnet in the horn, and a magnetic rotary position sensor in the driven part. As resistance to movement ("torque") increases, the flexible servo horn twists/deflects, angle of difference between the two parts changes and this can be detected by the magnetic sensor.
Picture a torque strain gauge, the way the needle deflects from the centerline of the gauge. This is similar but we're doing so in an radial (edit:removed axial) and not linear sense.
I went on to 3d print a flexible servo horn somewhat similar to this: http://mechanismsrobotics.asmedigitalcollection.asme.org/dat... but with the magnet embedded in the outer rim of the wheel and the sensor in the inner section.
Different amounts of sensitivity are obtained by printing different spoke stiffness on the horn.
Result is a compact, modular torque sensor for about $2 in parts. Feed the results to a PID look and you have a nice controller that can tell me when a robot leg is bearing a load, or is jammed, etc. This is essential to proper gait. Otherwise your robot is simply an electronic marionette.
One of the big challenges was getting 16 additional 16bit voltage reads back to my Rpi over i2c bus. (one value for each servo) https://www.adafruit.com/product/1085
Soln: used one of these multiplexer boards: https://www.adafruit.com/product/2717
and I used AdaFruit's excellent servo controller board: https://www.adafruit.com/product/815
and some neopixel rings for eyes: https://www.adafruit.com/product/3047
(wonderful for expressing mood)
adammck|8 years ago