Foot sensors for RN
Foot sensors for RN
by NovaOne
Fri Sep 14, 2007 7:18 pm
I've abandoned my "vision system" once again to work on another RN add-on instead... but i need help and advice:
Can anyone suggest the best positions to fit force sensors on the feet of RN?
I noticed JonHylands has 4 senors; pairs positioned roughly in the toe and heel area....
Any thoughts are welcome, I don't want to waste my time down a blind alley.
Can anyone suggest the best positions to fit force sensors on the feet of RN?
I noticed JonHylands has 4 senors; pairs positioned roughly in the toe and heel area....
Any thoughts are welcome, I don't want to waste my time down a blind alley.
by i-Bot
Fri Sep 14, 2007 8:23 pm
I have no experience, but my thoughts are that you if you are working to Static balance, you are trying to determine where the center of mass is with respect to both feet.
Three sensor per foot may be enough, but four in the corner seems to give better coverage, and simpler coordinate maths.
However you need also to consider the impact to the motion. Do you plan to have 4 point contacts, or four sensors to a seperate rigid foot plate?
My thoughts are a rigid foot plate, four sensors feeding A2D per foot. I can do you an A2D SPI interface on the C3024 if you want. or even give you an X and Y per foot.
I had a lot of fun and success down blind alleys, don't under estimate them !
Three sensor per foot may be enough, but four in the corner seems to give better coverage, and simpler coordinate maths.
However you need also to consider the impact to the motion. Do you plan to have 4 point contacts, or four sensors to a seperate rigid foot plate?
My thoughts are a rigid foot plate, four sensors feeding A2D per foot. I can do you an A2D SPI interface on the C3024 if you want. or even give you an X and Y per foot.
I had a lot of fun and success down blind alleys, don't under estimate them !
by NovaOne
Fri Sep 14, 2007 10:00 pm
Thanks i-Bot...I don't want you to do it all for me 
The i2c flash upgrade should do just fine, i already have two AD7417 4-Channel, i2c ADC's I was thinking of using?
You seem to have thought about this, or understand the problem better than I do.
This is what i understand (am I on the right lines)?
Four sensors seems to be good because (as you say) if considering one foot only; you average the values from the left pair of sensors and find the difference between this and the average values from the right pair of sensors, you can find crudely how much the robot (centre of gravity) is off side to side (X value). Likewise for the comparison between the average heel and toe pairs, to find a Y value.
Then comparing both x and y values from both feet it should be possible to calculate an approx. overall robot center of gravity? (assuming the robot is standing on both feet)
All sensors will be fitted to a rigid PCB.
Thanks
The i2c flash upgrade should do just fine, i already have two AD7417 4-Channel, i2c ADC's I was thinking of using?
You seem to have thought about this, or understand the problem better than I do.
This is what i understand (am I on the right lines)?
Four sensors seems to be good because (as you say) if considering one foot only; you average the values from the left pair of sensors and find the difference between this and the average values from the right pair of sensors, you can find crudely how much the robot (centre of gravity) is off side to side (X value). Likewise for the comparison between the average heel and toe pairs, to find a Y value.
Then comparing both x and y values from both feet it should be possible to calculate an approx. overall robot center of gravity? (assuming the robot is standing on both feet)
However you need also to consider the impact to the motion. Do you plan to have 4 point contacts, or four sensors to a separate rigid foot plate?
All sensors will be fitted to a rigid PCB.
Thanks