I am looking to design a sensor feedback system that someone can stand on whilst in teh gym ( like a mat say with sensors in it). The purpose is to measure the force distribution between the big toe little toe and heel and then triangulate the COG ( centre of gravity/force) to see if they have the COG thru their midfoot. So it would need an visual interface ( could be super simple) so they can see in real time if they are keeping the COG in the midfoot as they squat?
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Hi Scott,
I’d take a look at using some load cells and rubber spacers on a platform to bear the weight.
Then using the load cell amplifier and a microcontroller/SBC you can calculte a ratio between all of them and draw your point on the screen
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Hi Scott,
Cool idea! A neat trick with Liam’s setup is that an equivalent force vector through the plate will be the same as the force through their foot.
You technically only need three load sensors, but 4 would probably get you a more stable platform and be easier to work with - and the maths is about the same.
As long as your plate is stiff enough (ie. relatively small in width and length, but appreciably thick, and made of something sturdy like steel plate), you should get quite good results.
Just keep in mind that any one sensor will have to be able to take close to the full load you design it for. Some rubber in between the plate and the load sensor is not a bad idea, but you want to keep it minimal - just enough to help distribute the load evenly over the sensor and minimize/prevent plastic deformation where it meets the plate.
Once you’ve got it setup, the total weight is just the sum of the weight from each sensor. The equivalent force can be found the same way as for corner weights on a car - you check the two x pairs to get an x location, then check the two y pairs to get a y location, and that gives you the X,Y coordinates of your ‘CoG’.
The tricky part in practice is to include ‘bump stops’ that take the load instead of your load cell in an overload condition, and cleaning up the signal from the load cell to get a smooth result, and working out and overlaying the position of the foot, though there are some low tech solutions to this (like always place their feet in the same spot).
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