No abstract

Studies have been carried on the effect of rocking on a baby and concluded that baby sleeps easier while being rocked. In Malaysia, as in many Southeast Asian Countries, it is common to put babies to sleep in a baby hammock. The vertical rocking motion generated by baby hammock has exposed babies to whole-body vibration (WBV). It has been shown by ISO2631 (1997) that WBV may lead the discomfort and adverse effect on health. Standards have been set by ISO 2631 (1997) concerning the WBV for people in a recumbent position and consider weighted vibrations of more than 2 m/s 2 to be extremely uncomfortable. However, standards concerning the allowable amount vibrations a baby in a baby hammock can safety endure are currently lacking. WBV analysis of the baby hammock with the weight ranged from 3kg to 14kg is conducted. For each measurement, four conditions are considered: manual rocking, auto rocking with low, medium and high speed. In this study, average root-mean-square values for the acceleration were found to be at a maximum of 2.46 m/s 2 , and to be above the extremely uncomfortable level. This study develops a baseline exposure time for the baby hammock before it reaches the safety values of exposure action value (EAV) and exposure limit value (ELV) set by ISO 2631ISO (1997.

Severely disabled people have difficulties to use joystick in controlling electrical power wheelchair because controlling the joystick requires a large force which is more than the threshold for severely disabled people. It is difficult for them to use joystick to provide precise commands to the electrical system of the wheelchair because they cannot control over the deck tilt angles of joystick precisely. Thus, the idea of using fingers bending motion to control electrical wheelchair provides a solution for this problem. However, trembling fingers motions from disabled people generate signal noise that cause the motion control of the wheelchair not running smoothly. The objective of this paper is to tackle signal noises that are caused by trembling fingers motion. Three filtering methods were conducted which are Moving Average, Low-Pass, and Kalman Filters. The results indicate that Kalman Filter has significantly improved the smoothness of fingers bending command signal to the electrical wheelchair as compared to Moving Average and Low-Pass Filter.

Human is exposed to whole-body vibration either in sitting, standing or recumbent position. Many studies had been carried out to study the vibration responses and develop the mathematical modelling in sitting and standing vertical position. According to previous studies, the resonant frequencies of the human body were identified to be in the range of 4-6 Hz and 8-12 Hz in the vertical position. Recumbent whole-body vibration also plays an important role as many situations in our everyday life are related to recumbent whole-body vibrations such as riding a train, ambulance transporting a patient or even sleeping. However, the studies of recumbent whole-body vibration are very lacking. Therefore, the main objective of this study is to develop a mathematical model to identify the response when a human body is subjected to recumbent whole-body vibrations. In this study, a nine degree of freedom mathematical model was developed, and the responses of the body were analyzed using Matlab Simulink. The overall resonant frequency of the body was found to be 1.4 Hz. Meanwhile, the head and neck had two resonant frequencies, which were 1.3 and 3.28 Hz for the head, and 1.4 and 3.4 Hz for the neck. This newly developed mathematical model can be used as a fundamental model to predict the response of any recumbent whole-body vibration.

The challenge of designing an effective vibration absorber for any mechanical or mechatronic system is formidable. A good vibration absorber must provide broadband vibration reduction yet still keep in lightweight and size to minimize space requirements and maximize equipment accessibility. Broadband vibration is usually attenuated by using an active or semi-active vibration absorber. However, these methods are relatively costly and complicated compared with a passive vibration absorber. Moreover, passive vibration absorber often limited to narrowband frequency reduction since, in the past, it is usually tuned to the targeted frequency or optimum damping and optimum tuning ratio. This paper demonstrated that a passive vibration absorber could be implemented to reduce the broadband vibration of a system, considering the effect of the parameter of passive vibration absorber, the location attachment of the absorber, and the targeted mode shape. The result shows that a properly tuned passive vibration absorber can reduce the root mean square amplitude vibration by 60.91%, covering the first four vibration modes (0 to 300Hz).