Unconventional Foot Sensing

Hexapod Robots

Unconventional Foot Sensing

Postby CorbPeters » Fri Dec 21, 2012 6:48 pm

I have been thinking of different ways to add a foot sensor to my hexapod. I thought about just adding a microswitch to the bottom of each foot but I am looking for something smaller and more discrete. I first looking into making small capacitors with a compressible dielectric material and a 555 timer circuit; when the capacitor compresses the capacitance will increase making the 555 timer circuit change frequency. This would provide feedback that would respond differently based on how much pressure was placed on the capacitor. I have not tested this beyond Multisim but it seems like it would work.

Another idea that I want to bring up is that a leg will draw more current when it is on the ground than it will when it is in the air; using this I could just add current sensing to each leg and when it is moving down watch for increases in current. I have tested this a little. My hexapod has 3 servos per leg and together when the leg is in the air it draws under 200mA but when the leg is on the ground in a normal standing position the leg draws around 500mA. The idea here is to move the leg until the current jumps, then it has hit something. This would work as contact anywhere on the leg in any direction of motion, not just down. If the leg was moving upward and hit the ceiling the current would go up and the hexapod would know it hit something and based on which direction the leg was moving, the hexapod could estimate where an object is.

Any thoughts on either of these ideas? I will ttest the current sensing method in more detail and see how it goes but has anyone thought of either of these methods before?
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