Study of Functional Electrical Stimulation by Using Slip and Force Sensors for Grasping

功能性電刺激輔具可藉由電流刺激肌肉，幫助脊髓損傷患者肌肉收縮達成施力之目的，但需由外部操作電流強度來控制施力強度而無法達到最適施力量。本研究主要目的是將力量感測裝置與滑動感測器之訊號輸入至一閉迴路功能性電刺激系統，刺激脊髓損傷患者之癱瘓手部而能達成握物的動作。力量感測器是由CSA導電橡膠與梳狀電極組合而成，可監測手部施力值。滑動感測器由發光二極體與影像感測器所組成，能監測物體與手部的相對位移，避免物體從手部滑落。
為使患者能藉電刺激之功用拿起物體，本研究係以電流刺激手部及前臂使肌肉收縮，冀能握住物體；當滑動感測器停止輸出滑動訊號時，力量感測器感測之數值即為可握住物體之最小握力值。透過LabVIEW程式，可即時比較最小握力值與量測握力值之差距，適時調整電刺激強度以維持該施力值，改善因持續電刺激使肌肉疲勞導致握物滑落的問題。

The orthosis of functional electrical stimulation (FES) could help spinal cord injured (SCI) subjects generate muscle contraction so as to produce grasping force. However, the current for FES is controlled by manual input and it is troublesome to stimulate properly. The purpose of this research is to send the signals from slip and force sensors to a closed-loop FES system. Thus the SCI subjects could grasp objects with minimal force. The force sensor is composed of pressure conductive rubber CSA and comb electrode which can measure the strength of force. The slip sensor is made of light-emitting diodes which can detect movement between object and hand due to the object falling down.
In order to help the patient grasp object with the aid of electrical stimulation, electric current is applied to the palm and forearm of the patient to induce muscle contraction, thus hold the object can be hold. When the slip sensor stops sending signals, the value detected by the force sensor is the minimal value of grasping force. Difference between minimal grasping force and detected grasping force can be measured in real-time by using LabVIEW. Therefore, adjustment of intensity of electrical stimulation can be achieved by maintaining the minimal grasping force that improves grasping object in less fatigue.