軟性壓電式觸覺感測器應用於機器人捉取控制

Grasp Control with Robotic Flexible Piezoelectric Tactile Sensor

本研究所提出軟性壓電式觸覺感測器，可辨認滑動與檢測動態側向力量之功能。為了防止機器手臂於抓取過程中發生掉落的情況，其機器人檢測未知重量的物體時的初始滑動訊號則為最重要的事情。此感測器利用軟性電路板（FPC）製作出兩個結構化電極夾著壓電薄膜（PVDF），利用內部凹凸結構彎曲作用，以感測器所產生的靜摩擦力現象使壓電薄膜（PVDF）輸出電壓值進行滑動檢測，因此兩個相反的電壓可判斷動態側向力與初始滑動。當感測器的產生壓縮應力時，其電壓發生將是正電位（V1）；另一方面，相反的壓縮應力則是呈現負電位（V3），壓縮應力的滑移信號皆與物體重量息息相關。本研究檢測初始滑動以三種加速度分別為（5、10、15 mm/s2），根據實驗結果顯示，感測器的對於滑動訊號的靈敏度會因為不同的加速度與物體重量變化成正比，實驗結果為在200克重下加速度為15 mm/s2電壓輸出0.08 V時為初始滑動判斷時之最佳靈敏度，故經由感測器辨認物體的初始滑動訊號，達到即時機器人手掌之監控功能。 We have developed a robust and fl exible tactile sensor for use in robotic gripping that can identify dual axis slippage by measuring the dynamic lateral force. The sensor consists of a rigid bump like structure embedded in a soft polydimethylsiloxane(PDMS) packaging and placed on top of a piezoelectric polvinylidene fl uoride(PVDF) fi lm that is sandwiched between two fl exible printed circuits(FPC) . The rigid structure induces two opposite stress states on the PVDF fi lm in the presence of a dynamic lateral force, resulting in a positive(V1) and negative voltage(V3) output at the electrodes located in the compressive and tensile areas, respectively. The sensor sensitivity defi ned as the voltage output variation depends on the slip acceleration and normal external force exerted on the sensor by the counter weight. From our results, it was observed that the best sensor response corresponding to a voltage output variation of 0.08V was obtained at an acceleration of 15 mm/s2 and a counter weight of 200 grams. To test its efficacy, the tactile sensor has been mounted on a robot arm and can successfully configure grab conditions by identifying slippage for objects with different weights. Consequently, the tactile sensor can sensitively detect slippage occurrence and direction of lateral force due to two opposite peak voltages occurring simultaneously rather than relying on variation in voltage output as utilized in conventional piezoelectric devices.