以並聯機器人呈現大範圍之三維虛擬阻抗

A Parallel Robot for Large-range Stiffness Rendering in Three Dimensions

藍兆杰(Chao-Chieh Lan)

《科儀新知》 231期 (2022/06) Pp. 27-41

摘要

觸覺回饋裝置用於向操作者傳輸阻抗，以模擬虛擬或真實環境的阻抗。現有的觸覺回饋裝置使用串聯或並聯機器人來提供多維度的阻抗。這些機器人通常具有非恆定雅可比矩陣，導致工作空間內某些區域的動態特性差和阻抗穩定性限制低。考慮到這些區域，虛擬勁度呈現的範圍有限。本文提出一種三自由度平移並聯機器人，在整個工作空間中具有恆定的雅可比矩陣。一致的動態參數允許呈現大範圍的虛擬勁度。為了提供高勁度呈現所需的大且準確的輸出力，以串聯彈性致動器驅動並聯機器人。串聯彈性致動器可用於大幅降低齒輪摩擦和輸出端慣量，以更準確地控制輸出力量和阻抗。本文將介紹觸覺回饋裝置的設計、動態模型和三維阻抗控制，並以多維阻抗和虛擬牆控制實驗，證明觸覺回饋裝置的準確性和呈現範圍。由於虛擬勁度的穩定範圍比現有的裝置要大得多，因此預計這種新型裝置可用於為軟硬環境提供準確的勁度呈現。

並列摘要

A haptic device is used to transmit impedance to a human user to mimic the impedance of a virtual or real environment. Existing haptic devices use serial or parallel robots to deliver impedance in multiple dimensions. These robots usually have nonconstant Jacobian matrices that result in poor dynamic properties and low impedance stability limits in certain regions within the workspace. To account for these regions, the range of stiffness rendering is limited. This paper presents a three-degrees-of-freedom translational parallel robot with a constant Jacobian matrix in the entire workspace. The consistent dynamic parameters allow a large-range virtual stiffness to be rendered. To provide the accurate and large output force required for high-stiffness rendering, series elastic actuators (SEAs) are used as the input for the parallel robot. SEAs can be used to minimize the geartrain friction and effective inertia to control the output force and impedance more accurately. Design, modeling, and three-dimensional impedance control of the haptic device are presented in this work. Multi-dimensional impedance and virtual-wall control experiments are illustrated to demonstrate the accuracy and rendering range of the haptic device. Since the stable range of virtual stiffness is much larger than existing ones, it is expected that this novel device can be used to render accurate stiffness for both soft and stiff environments.