Frequency Domain Analysis of Nonlinear Series Elastic Actuator via Describing Function

Nonlinear stiffness SEAs (NSEAs) inspired by biological muscles offer promise in achieving adaptable stiffness for assistive robots. While assistive robots are often designed and compared based on torque capability and control bandwidth, NSEAs have not been systematically designed in the frequency domain due to their nonlinearity. The describing function, an analytical concept for nonlinear systems, offers a means to understand their behavior in the frequency domain. This paper introduces a frequency domain analysis of nonlinear series elastic actuators using the describing function method. This framework aims to equip researchers and engineers with tools for improved design and control in assistive robotics.Comment: accepted by 2023 IEEE ROBIO conferenc

Effects of Eating or Skipping Breakfast on Heart Rate and Oxygen Uptake

The purpose of this study was to compare changes in heart rate, oxygen uptake, blood pressure and oral temperature between subjects eating breakfast and subjects skipping breakfast when they exercise each day at 11:00 AM and 2:00 PM. The study design included two different groups, a breakfast group and a skipping group. Subjects rested for five minutes, and they exercised on a pendulum ergometer for twenty minutes. After exercising, the resistance was returned to zero for a one minute cool down followed by five more minutes of complete rest(recovery phase). Oral temperatures of the skipping group were lower than those of the breakfast group at 11:00 AM. Diet induced thermogenesis (DIT), which increases core body temperature, is generated by eating breakfast. In the skipping group, the resting heart rates at 11:00 AM were lower than at 2:00 PM. A significant difference in heart rate after the first minute of exercise was seen between 11:00 AM and 2:00 PM in the skipping group. These results suggested that when skipping breakfast, the heart rate response immediately after beginning exercise is slow in the morning. Although all subjects did cooling down for one minute after exercising, oxygen uptake during the recovery phase in the skipping group at 11:00 AM was significantly higher than at rest. These results suggest that eating breakfast has a physiological influence on both heart rate and oxygen uptake

Fast recovery of elastic stiffness in Ag thin film studied by resonant-ultrasound spectroscopy

Nobutomo Nakamura, Takeo Nakashima, Hirotsugu Ogi, Masahiko Hirao and Masayoshi Nishiyama. Fast recovery of elastic stiffness in Ag thin film studied by resonant-ultrasound spectroscopy. Japanese Journal of Applied Physics, 2009, 48(7S), 07GA02. https://doi.org/10.1143/JJAP.48.07GA02

170-MHz electrodeless quartz crystal microbalance biosensor : Capability and limitation of higher frequency measurement

We develop a highly sensitive quartz crystal microbalance (QCM) biosensor with a fundamental resonance frequency of 170 MHz. A naked AT-cut quartz plate of 9.7 μm thick is set in a sensor cell. Its shear vibration is excited by the line wire, and the vibration signals are detected by the other line wire, achieving the noncontacting measurement of the resonance frequency. The mass sensitivity of the 170 MHz QCM biosensor is 15 pg/(cm² Hz), which is better than that of a conventional 5 MHz QCM by 3 orders of magnitude. Its high sensitivity is confirmed by detecting human immunoglobulin G (hIgG) via Staphylococcus protein A immobilized nonspecifically on both surfaces of the quartz plate. The detection limit is 0.5 pM. Limitation of the high-frequency QCM measurement is then theoretically discussed with a continuum mechanics model for a plate with point masses connected by elastic springs. The result indicates that a QCM measurement will break down at frequencies one-order-of-magnitude higher than the local resonance frequency at specific binding cites.Hirotsugu Ogi, Hironao Nagai, Yuji Fukunishi, Masahiko Hirao, and Masayoshi Nishiyama. 170-MHz electrodeless quartz crystal microbalance biosensor: Capability and limitation of higher frequency measurement. Analytical Chemistry, 2009, 81(19), 8068-8073. ©2009 American Chemical Society. https://doi.org/10.1021/ac901267b

Detection of glypiean-3 proteins for hepatocellular carcinoma marker using wireless-electrodeless quartz-crystal microbalance

Pure shear-wave resonances were excited and detected in 18- and 30-μm-thick electrodeless AT-cut quartz plates in liquids using line antennas contactlessly, achieving high-frequency quartz-crystal microbalances (QCMs). Their fundamental resonance frequencies (85 and 54 MHz) were monitored to study interactions in real time between human glypican-3 and an anti-glypican-3 antibody: glypican-3 is a prospective protein marker for hepatocellular carcinoma. Their affinity was determined by the Langmuir kinetics. This study demonstrates the high ability of the wireless-electrodeless QCM for detection of the protein markers and development of drugs for disorders.Hirotsugu Ogi, Toshinobu Omori, Kenichi Hatanaka, Masahiko Hirao and Masayoshi Nishiyama. Detection of glypiean-3 proteins for hepatocellular carcinoma marker using wireless-electrodeless quartz-crystal microbalance. Japanese Journal of Applied Physics, 2008, 47(5S), 4021. https://doi.org/10.1143/JJAP.47.4021

Design, Modeling, and Parametric Analysis of a Syringe Pump for Soft Pneumatic Actuators

Syringe pump has been applied to actuate soft pneumatic robots. Most previous works focus on designs of the syringe pump, its applications, and improvement of its problems such as leaking air, inefficient motions, etc. This paper introduces dynamical modeling and parametric analysis of a syringe pump. The syringe pump is made of a commercial syringe and a linear actuator. The dynamic equation is derived from the motions of the linear actuator, the air dynamics in the syringe, and the airflow inside the soft actuator. Because of the high-elastic materials, the volume of the soft actuator is a time-varying parameter. Therefore, the variation of volume is estimated by the Kalman filter instead of relying on the traditional design method. The dynamic model is also utilized to select optimal parameters which are verified by the experiments for the syringe pump. Two system controllers are designed with and without consideration of the pressure dynamics. The controller considering pressure dynamics outperforms. This work shows the benefits of pressure dynamic of the syringe pump for both system design and advanced controller design