This paper reports the development of an unconstrained sensing technique for monitoring the respiration and heartbeats during sleep using a polyvinylidene fluoride (PVDF) piezopolymer film sensor with the aim that the sensor can be used on the ordinary bed together with the condition that the use of the sensor does not interfere the daily sleep of the patient under measurement. A PVDF film is used as the sensory material in the sensor system. The film is placed under the sheet at the location of the thorax to pick up the fluctuation of the pressure on the bed caused by the respiratory movement and heartbeats. Wavelet multiresolution decomposition analysis is used for the detection of respiration and heartbeat from the sensor output. It is shown that the respiration and heartbeats can simultaneously be detected by the sensor with the use of the wavelet multiresolution decomposition analysis.

No abstract

This paper is a study of a minute force control of a two-fingered miniature gripper driven by piezoelectric bimorph cells. The system is composed of two flexible cantilevers and a compact force sensor attached to the tip on one finger. Controi action is applied by a co-located set ofpiezoelectric bimorph strips placed at the base ofeach finger. The mathematical model ofthe electro--mechanical system is developed and applied to the study ofa control problem where the gripper is commanded to grasp its object with a time-constant force O.OIN. The Pil) control algorithm is introduced and the dynamics and control behaviour ofthe system are investigated both theoretically and experimentally. The obtained results can be surnmarized as follows.(1) The present artificial finger system works well as a miniature gripper. It control the fingertip force on the order ofO.OIN. can (2) The theoretical and experimental results are in good agreement with each other, which leads to an understanding that the mathematical model of the system is reasonable and can be applied to the design of more dexterous soft-handling grippers that will be developed in the near future.(3) The PID control algorithm is sufficient for the stable grasping ofa variety of objects with different. It was found the integral feedback gain plays a significant role in the control behaviour of the system. The optimal PD controller can be designed relatively easily by determining the feedback gains through the comparison of the system characteristic roots with the roots of the reference system and then adjusting the values referring to the simulated system response on the computer.

No abstract

No abstract