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During locomotion, humans sometimes entrain (i.e. synchronize) their steps to external oscillations: e.g. swaying bridges, tandem walking, bouncy harnesses, vibrating treadmills, exoskeletons. Previous studies have discussed the role of nonlinear oscillators (e.g. central pattern generators) in facilitating entrainment. However, the energetics of such interactions are unknown. Given substantial evidence that humans prioritize economy during locomotion, we tested whether reduced metabolic expenditure is associated with human entrainment to vertical force oscillations, where frequency and amplitude were prescribed via a custom mechatronics system during walking. Although metabolic cost was not significantly reduced during entrainment, individuals expended less energy when the oscillation forces did net positive work on the body and roughly selected phase relationships that maximize positive work. It is possible that individuals use mechanical cues to infer energy cost and inform effective gait strategies. If so, an accurate prediction may rely on the relative stability of interactions with the environment. Our results suggest that entrainment occurs over a wide range of oscillation parameters, though not as a direct priority for minimizing metabolic cost. Instead, entrainment may act to stabilize interactions with the environment, thus increasing predictability for the effective implementation of internal models that guide energy minimization.

During locomotion, humans sometimes entrain (i.e. synchronize) their steps to external oscillations: e.g. swaying bridges, tandem walking, bouncy harnesses, vibrating treadmills, exoskeletons. Previous studies have discussed the role of nonlinear oscillators (e.g. central pattern generators) in facilitating entrainment. However, the energetics of such interactions are unknown. Given substantial evidence that humans prioritize economy during locomotion, we tested whether reduced metabolic expenditure is associated with human entrainment to vertical force oscillations, where frequency and amplitude were prescribed via a custom mechatronics system during walking. Although metabolic cost was not significantly reduced during entrainment, individuals expended less energy when the oscillation forces did net positive work on the body and roughly selected phase relationships that maximize positive work. It is possible that individuals use mechanical cues to infer energy cost and inform effective gait strategies. If so, an accurate prediction may rely on the relative stability of interactions with the environment. Our results suggest that entrainment occurs over a wide range of oscillation parameters, though not as a direct priority for minimizing metabolic cost. Instead, entrainment may act to stabilize interactions with the environment, thus increasing predictability for the effective implementation of internal models that guide energy minimization.

The fast development of CMOS IC process technology and the opening up of high frequency bands by regulatory bodies has aided wireless communication industry with development and commercialization of long-medium and short range wireless communication applications, for example GSM, Wireless LAN, Bluetooth and UWB. Ultra Wideband (UWB) is a promising technology that covers a bandwidth from 3.1GHz to 10.6GHz, which features distinctive advantages, such as high data rate over short and medium range, low interference or co-existence with other wireless technologies and robustness towards multipath fading and possible usage in personal area network (PAN) and body area network (BAN), targeting especially health care monitoring applications. Impulse radio UWB or ir-UWB, is one of the UWB technologies, which applies transmission of short duration (pico-nano second) and carrier less pulses. Several receiver architectures [1, 2 & 3] based on the principle of correlation has been proposed, with Quadrature Downconversion Auto-Correlation Receiver (QDAcR) [3] being one of them. This thesis work builds up further on the generalized QDAcR model of [3], starting with an advanced time domain analysis of principle of Downconversion in QDAcR and exploring the dependency of QDAcR on downconverter related stochastic perturbations such as phase noise, jitter and amplitude perturbations. The use of Stationary Stochastic Process Theory, Fokker-Planck Equation and Floquet’s Theory resulted in a simplified equation, incorporating the effect of stochastic perturbations; this equation of prominence, further can be extrapolated to perturbation analysis of Zero (low) – IF receivers. A complete system modeling of QDAcR downconverter resulted in vital specifications for the QDAcR downconverter being the requirement of a 5.6 GHz quadrature voltage controlled oscillator (QVCO) with a minimum phase noise of -90dBc/Hz at 1MHz offset and with a maximum permissible phase error of 4 degrees. This relaxed n, Analog and Radio Frequency (ELCA), Microelectronics & Computer Engineering, Electrical Engineering, Mathematics and Computer Science

The fast development of CMOS IC process technology and the opening up of high frequency bands by regulatory bodies has aided wireless communication industry with development and commercialization of long-medium and short range wireless communication applications, for example GSM, Wireless LAN, Bluetooth and UWB. Ultra Wideband (UWB) is a promising technology that covers a bandwidth from 3.1GHz to 10.6GHz, which features distinctive advantages, such as high data rate over short and medium range, low interference or co-existence with other wireless technologies and robustness towards multipath fading and possible usage in personal area network (PAN) and body area network (BAN), targeting especially health care monitoring applications. Impulse radio UWB or ir-UWB, is one of the UWB technologies, which applies transmission of short duration (pico-nano second) and carrier less pulses. Several receiver architectures [1, 2 & 3] based on the principle of correlation has been proposed, with Quadrature Downconversion Auto-Correlation Receiver (QDAcR) [3] being one of them. This thesis work builds up further on the generalized QDAcR model of [3], starting with an advanced time domain analysis of principle of Downconversion in QDAcR and exploring the dependency of QDAcR on downconverter related stochastic perturbations such as phase noise, jitter and amplitude perturbations. The use of Stationary Stochastic Process Theory, Fokker-Planck Equation and Floquet’s Theory resulted in a simplified equation, incorporating the effect of stochastic perturbations; this equation of prominence, further can be extrapolated to perturbation analysis of Zero (low) – IF receivers. A complete system modeling of QDAcR downconverter resulted in vital specifications for the QDAcR downconverter being the requirement of a 5.6 GHz quadrature voltage controlled oscillator (QVCO) with a minimum phase noise of -90dBc/Hz at 1MHz offset and with a maximum permissible phase error of 4 degrees. This relaxed n, Analog and Radio Frequency (ELCA), Microelectronics & Computer Engineering, Electrical Engineering, Mathematics and Computer Science

Schroeder, R. T., Croft, J. L., & Bertram, J. E. (2021). Evaluating the energetics of entrainment in a human–machine coupled oscillator system. Scientific Reports, 11, article 15804. https://doi.org/10.1038/s41598-021-95047-x