I can't say that the load cells have been particularly problematic... if I built an accelerometer-based balancer I would probably just face different kinds of issues.
Firstly, the purpose of a balancer is to measure the vibration forces which act on the rotating assembly at a certain RPM. Then, knowing the vibration forces, you can determine suitable counterweights (which will generate centrifugal forces) to counteract the vibration forces.
Here is a simplified explanation of how an accelerometer-based balancer works:The shaft's bearings are suspended on flexible supports.
Vibration forces act on the shaft+wheel+tire+bearings+accelerometers assembly (moving assembly).
The moving assembly accelerates according to F = ma (Newton's Law) and the vibration forces which act on it, where "m" is the mass of the entire moving assembly.
The accelerometers measure the accelerations of the moving assembly, from which the correction masses can be determined...
The complicated part here is in F = ma. "m" is unknown. "F" is also some combination of vibration forces and forces from the flexible suspension system. The mass of the moving assembly and the stiffness of the supports create a mechanical low-pass filter with an unknown transfer function (with magnitude and phase shift) that describes the correspondence between the vibration forces and measured accelerations.
Sometimes, the flexible mounted balancers will have you add a known imbalance mass to the assembly, to figure the transfer function at a particular RPM.
Here is how a load-cell-based balancer works:The shaft's bearings are in rigid contact with fixed load cells.
Vibration forces act on the shaft+wheel+tire+bearings assembly (floating assembly).
The load cells measure the reaction forces required to keep the floating assembly immobilized; the reaction forces have a direct relationship with the vibration forces.
So here, with the assumption of infinite stiffness, it's really a lot more direct; there is no variable low-pass filter.
On a real load-cell based balancer, there is indeed a variable (depends on the wheel's mass) mechanical low-pass filter. At low frequency, the reaction forces are directly related to the vibration forces. As frequency increases, there is a phase shift. When the frequency of the vibration forces is higher than the corner frequency of the filter, there is attenuation.
However, a load-cell based balancer is designed to be as stiff as possible, so that the corner frequency is high enough (even with a heavy wheel) that there is negligible phase shift at the expected balancing RPM. Even if the transfer function is not precisely known, it's close enough to 1:1 at the balancing RPM. Well, that's the design objective anyway
So anyway, I picked a load-cell type because it seems MUCH simpler... The commercial wheel balancers are rigid.
However, balancers for electric motors, turbos are more likely to be flexible suspension. Probably with the higher balancing speeds, there may be unavoidable phase shift, so you just give up on the stiff load cell topology.
As for single-spin balancing, that is the objective. However, I do not expect to meet this objective... I don't think anyone does single-spin balancing. When the commercial balancers claim single-spin balancing, their displays show "0.00" ounces correction mass required, but when the mass is below some tolerance level, the software rounds it down to zero. So that's pretty much cheating.
When I use my balancer (Mk1), I do iterations, but I'm trying to get the imbalance as close to zero as possible (not just "good enough"). In the final iterations, the correction can consist of moving the weight by 2 mm, and then trying again.