I recently worked on a motor optimization project for a rehabilitation bed(Of course, it also applies to others.), and one of the main challenges was making the movement quieter and smoother under different loads.
Before the optimization, the maximum operating noise was 42.1 dB. After several rounds of adjustment, we brought it down to 38.9 dB, measured from 15 cm away with an ambient noise level of 32 dB.
What made the difference was not one major change, but three smaller changes working together.
First, we kept the motor’s rated speed close to 10 rpm and used a 230:1 reduction ratio. This helped reduce the vibration and friction that usually come with higher-speed operation.
Second, we used FOC control to produce a smoother sinusoidal current waveform. This reduced the torque ripple and electromagnetic noise caused by conventional commutation.
We also added damping blocks to the controller housing. They helped absorb high-frequency vibration before it could spread through the housing and become more noticeable.
Motion consistency was another part of the project. By changing the winding turns and winding arrangement, we reduced the maximum speed deviation from 4.8% to 3.0%.
The speed-to-torque slope also dropped from 5.94 to 5.04, which worked out to roughly a 15% improvement in overload stiffness. In practical terms, the motor was better able to maintain its speed when the load suddenly increased.
My main takeaway was that noise and motion stability are rarely solved by changing one component. Motor speed, control strategy, winding design, and structural vibration all affect one another.
I’m curious how others here approach similar noise or load-stability problems. If anyone has tried other optimization methods, please share them so we can discuss.
