Disturbance torque and motion state estimation with low-resolution position interfaces using heterodyning observers

This paper assesses and analyzes a harmonic vector modeling method for reducing disturbance torque and motion state estimation error using quantized input measurements of position. There is a finite resolution available for any digital interface, and quantization will always be present in some form. Although it is not possible to completely reconstruct a quantized measured state, it is possible to attenuate deterministic quantization characteristics. The discussed method models quantized position feedback as a spatially rotating vector consisting of fundamental and harmonic components. The error mitigation strategy involves decoupling these spatial quantization harmonics from the actual fundamental position, using heterodyning tracking observer topologies.