Understanding the role of the neuromuscular dynamics in biodynamic feedthrough problems

Biodynamic feedthrough (BDFT) refers to a phenomenon where accelerations cause involuntary limb motions which, when coupled to a control device, can result in unintentional control inputs. This study aims to increase the understanding of BDFT, and the role of the neuromuscular system (NMS) in particular. The fundamental question driving this research is how accelerations are transferred through the human body, i.e., through the NMS, and how the exact setting of the NMS influences this feedthrough. As the neuromuscular system differs from person to person and is highly adaptable, it is expected that BDFT does not only vary from person to person, but that also a single person can express a range of BDFT dynamics by adaptation of the neuromuscular settings. To investigate this hypothesis, use is made of the neuromuscular admittance, which describes the dynamic response of human limbs in response to force disturbances. A measurement method was developed to measure neuromuscular admittance and BDFT simultaneously. The results from this experiment confirm that the neuromuscular system plays such a large role in the occurrence of BDFT that the variability of the neuromuscular system cannot be ignored when investigating BDFT problems. Based on the experimental data a BDFT model was developed. The model parameters were estimated by fitting the model on the experimental data. The model successfully captures BDFT dynamics in both the frequency domain and the time domain, for different subjects and different settings of the neuromuscular system