6-axis load cell force calculation
6-axis load cell force calculation
(OP)
I feel like I am overlooking something really simple here but I could use your help to restore my sanity.
I have some data I collected using a 6-axis load cell. I would like to use this and calculate the resultant load force applied to the tool tip.
Am I correct in wanting to use the 3 force balance equations and 3 moment balance equations to find the solution? The problem I am having trouble wrapping my head around is that I would have 6 equations but I'm not sure that I have 6 unknown values.
So, given some known distance along the z-axis (longitudinal axis) that the load force is applied, how can I calculate what that load force is and its spatial orientation?
I would really appreciate any insights you can provide.
I have some data I collected using a 6-axis load cell. I would like to use this and calculate the resultant load force applied to the tool tip.
Am I correct in wanting to use the 3 force balance equations and 3 moment balance equations to find the solution? The problem I am having trouble wrapping my head around is that I would have 6 equations but I'm not sure that I have 6 unknown values.
So, given some known distance along the z-axis (longitudinal axis) that the load force is applied, how can I calculate what that load force is and its spatial orientation?
I would really appreciate any insights you can provide.





RE: 6-axis load cell force calculation
Where did you find a 6 axis unit? I've heard of 3. My guess is that the moments at the tool tip will be low compared to the forces at the tool tip.
RE: 6-axis load cell force calculation
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: 6-axis load cell force calculation
If the tip where the load is applied is cantilevered out from the fixed load cell, wouldn't there be no moments applied at the tip?
As far as I know these things are fairly common. I've heard of them before but this is the first time I have used one.
RE: 6-axis load cell force calculation
So for example, Force_tip_X=Force_Load_Cell_x+Y*TorqueZ
where Y is the obvious measurement and the + may be - if I've got my signs wrong.
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: 6-axis load cell force calculation
RE: 6-axis load cell force calculation
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: 6-axis load cell force calculation
So your units are lbf*in^2 (or N*m^2)?
RE: 6-axis load cell force calculation
I should have drawn the diagram.
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: 6-axis load cell force calculation
Thanks for your help, I will be looking through the data more tomorrow and see if I can make sense of what is happening.
RE: 6-axis load cell force calculation
I'm not quite sure what that means. Where is the origin? If the origin is at the center of the Fx,Fy and Fz measurement points within the load cell, then Fx,Fy and Fz directly read the external forces applied at the tool tip (assuming no moments applied at the tool tip). In that case you don't need the Mz output from the cell (Measured Fx = Tool Tip Fx)
RE: 6-axis load cell force calculation
What I did find puzzling until I did the experiments and the math...every load cell for every axis had some degree of cross-talk to every other axis. Whether due to flexing of the structure, or simple alignment errors, or both. To put it another way, when we applied a strong sideways force (yaw) during calibration, some response would be noted on the fore/aft (drag) sensor, and some on the vertical (lift) sensor as well, ditto the moment sensors. This resulted in, e.g. for a 6-dof force balance, the correction equations forming a 6x6 matrix. To reduce the data, we multiplied the matrix by the measured force/torque "vector" to produce the true force "output" vector.
Dunno, maybe the sensor manufacturer has calibrated the device you are using, and the corrections are made internally in some black box, and the alignment is very tightly controlled by tight-fitting dowel pins and a finely polished flat surface plate...but I'd still calibrate it and verify that it is so, as any misalignment of your tool axes to the sensor axes will show up as moments or forces in funny places...
RE: 6-axis load cell force calculation
Even more incredible is that this 6 axis transducer is for a machine tool. It would have to be stiff in all 6 axes which would make the problem with cross talk even more difficult.
happygopher -
Is this for a lathe (transducer connected to tool bit) or a mill (transducer connected to work piece)? Can you say who the manufacturer is? (Just curious, multiaxis load cells are neat)