Study on Low Noise Front-end Circuit Design For Biomedical Myo-electric Feedback System Application

[[abstract]]電刺激治療早在公元前四世紀羅馬人已經開始使用，他們首先利用電鰻來治療關節疼痛，而經由許多臨床驗證及文獻數據顯示，電刺激治療已被確認具有其療效，不僅在抑制疼痛方面，對於神經受損後防止肌肉萎縮亦有一定的功效。電刺激器已不再侷限於復健門診的使用，坊間即可方便購得隨身型刺激器，然而，市售電刺激器雖然皆符合國際電工委員會（IEC）對於人體電刺激的安全規範，但若使用者不當調整還是有可能會對人體造成傷害。因此，本篇希望利用類比感測器前端讀出電路設計，擷取刺激後的肌肉收縮電位來建構一套生物回饋控制系統，依據適當的設定來穩定控制刺激的強度。 經刺激的肌肉收縮電訊號擷取系統，對於訊號品質有一定的要求，在本篇的設計中，包含感測器特性描述及生理訊號處理模式，針對EMG訊號特性本系統規劃其增益227倍，頻寬20～500Hz。另外；針對前端讀出電路的雜訊抑制能力，貼上電極片後本系統第一級輸出端雜訊均方電壓值為 ，而經濾波器能有效抑制其輸出雜訊均方電壓為 。迴饋的架構中也驗證了刺激振幅調整在10~50mA為線性輸出，由肌肉收縮電訊號與控制訊號的比較，證實了可建構出生物回饋控制系統，使得電刺激器除了符合安全規範，更能夠自動判別使用者的肌肉收縮情況穩定控制其刺激的輸出。[[abstract]]Electrotherapy had been used by the Romans before the Gregorian calendar. They applied electric eels to cure arthralgia. Electrotherapy had been confirmed having curative effects by several clinical verifications and technical literatures. It is effective not only for inhibition of pains but also muscular dystrophy avoiding after nerve injured. The electro-therapy instrument applications more than rehabilitate outpatient services, the portable type can even be easily purchased. Generally, commercial portable instruments tally with the safety regulation of The International Electrotechnical Commission, IEC, however, the possibility of injuring the human body due to an improper application still exists. Therefore, thesis applies an analog sensor to sense the front-end signal, and to build up a bio-feedback control system via a contractor potential after the muscle is excited. Then the control system relies on the appropriate parameters to stabilize the exciting intensity. The signal quality demand of the muscle contractor potential sensing system is extremely strict. Due to the requirement of the signal quality, the sensor characteristic description and biology signal processing mode based on EMG signal characteristic are presented in this thesis with 227 times gain and 20~500 Hz bandwidth. Moreover, after the electrode is placed, the output noise voltage is sufficiently large. An filter is designed for the noise reduction capability promotion of the front-end sensing circuit, it reduces output noise voltage from to . The system obtained error signals by the comparison of the sensed muscle contractor potential and a control signal, the error signals are applied to modify the output amplitude. The experiment results verified the performance of the controller, the system output is well regulated in 10~50 mA. Finally, we verified the established controller can be applied on electro-therapy instruments. It not only determinates the states of muscle contractor to regulate the output stability automatically, but also tallies with the international safety standard.[[note]]碩