Shuji Nishiyama

Vibration Analysis System for a Bicycle With a Rider and Two Infant Seats

This paper describes a vibration analysis system for a rider and two infants riding on a bicycle with two infant seats. To examine the vibrations of the rider and infants, a vibration model and a simulation system were designed for this bicycle–rider–infant system. The vibration characteristics in the analytical results were compared with the experimentally measured results. The effects of the vibrations on the occupants owing to the altered centroid of the bicycle were investigated. This investigation indicated that the analytical results corresponded with the measurement results for the occupants. When the centroid of the bicycle was moved forward, the root mean square (RMS) acceleration values for the front infant increased, whereas the maximum acceleration values decreased. In contrast, both the RMS and maximum values of acceleration for the rear infant increased when the centroid of the bicycle was moved forward. However, both the RMS and maximum values of acceleration for the rider increased when the centroid of the bicycle was moved backward. On the basis of these results, a relationship between the centroid of the bicycle and the transient response of the occupants was found by using the proposed vibration analysis system.Copyright

Investigation of a Vibration Reduction System for Vehicle Seats by a Vibration Model Consisting of a Vehicle, Seat, and Human Body

This paper describes a vibration reduction system that can minimize the vertical vibrations of the human body in a vehicle. This system can control the mechanical properties of the seat cushions, such as the spring constants and damping coefficients. To examine the feasibility of this vibration reduction system, we design a vibration model of both an occupant–seat–steering wheel–pedals–vehicle system and a calculation system. Further, we carry out a numerical analysis to calculate the magnitude of vibrations transmitted from the road surface to the human body based on ISO7096-EM6. Comparison results of the frequency response between the analysis and the experiment indicate the feasibilities of both the vibration model and the analysis method. Furthermore, vibration of the head was reduced 60.1% by controlling the mechanical properties of the seat from 1/5 to 5 times. In summary, the in-vehicle vibration reduction system successfully reduces vibrations from the seat to the human body.Copyright

Vibration Characteristics of a Human Adult and Infants Travelling in a Bicycle With Two Child Seats

This paper describes the vibration characteristics transmitted from the road to the human body when riding a bicycle with two child seats. To examine the vibration characteristics for the bicycle, human body, and infants, we developed a system for measuring the vertical vibrations using acceleration sensors and infant dummies as a substitute for real infants. In an experiment on the transient response, subjects rode over three different types of lugs at a constant velocity. In an experiment on the frequency response, subjects were vibrated by a vibration exciter. The experimental results clarified the vibration characteristics of a bicycle–occupant–system.Copyright

Investigation of a Seat With an Active Control System for Reducing Vibrations From the Seat, Steering Wheel, and Pedals to the Human Body in a Vehicle

This paper describes an active control system aimed at minimizing vertical vibrations from the seat to the human body in a vehicle. This system controls mechanical properties such as spring constants and damping coefficients on the basis of vibration analysis. In our previous study, this active control system could not be validated for a model that considers the steering wheel. This study aimed to clarify the relationship between the mechanical properties of the seat and the vibrations of the human body in a seat–steering wheel–occupant system. Then, a vibration model for such a system was designed and the influence of seat cushions on the vibrations of the human body was examined using this system. The mechanical properties of the bearing surface and the back of the seal were controlled with reference to 1/5–5 times the standard condition, and the influence of seat cushions on the vibrations of the human body was examined by using this system. From these results, the effectiveness of the vibration model and the analytical system was examined by comparing the frequency response results of the analysis and an experiment. It was clarified that the frequency of the first resonance point changed significantly when the mechanical properties of the seat-bearing surface were modified, and the frequency of the second resonance point changed significantly when the mechanical properties of the seat back were modified.Copyright