Pitch-Yaw串接型機器蛇之創新表達式與攀階之步態規劃

Abstract

本研究提出一套針對pitch-yaw交互串接型機器蛇之創新表達式：基於空間中移動Trihedron座標的概念，導出針對連續分段直線之Trihedron座標系統表示式，建構高自由度機器蛇各相鄰旋轉軸之簡潔齊次關係。由於pitch-yaw的串接機構與階梯環境的特性，考量機器蛇攀爬階梯時之姿態，將旋轉軸角度分三種狀況：0°、+90°或−90°進行探討。且僅用齊次矩陣的行平移與變號即能表達相鄰關節之座標轉換關係。可完全避免傳統的Denavit-Hartenberg表示法繁雜的矩陣乘積運算。最後，應用於此創新表達式進一步描述攀階運動整個過程，包括六個姿態，初始狀態、前端舉升、前端外展、轉折點平移、尾部抬升與初始化。結果證實一節數18節pitch-yaw交互串接之機器蛇，可攀爬級高25公分、級深25公分與級寬100公分之階梯。此創新表達式可簡化運算之複雜度、更為直觀地和機器蛇的姿態連結。

A novel representation for snake robots with pitch-yaw connection in series is proposed in this research. Trihedron-based coordinate systems for the expression of consecutive segments are established to describe snake robots with pitch-yaw structure, which are derived from the conventional Trihedron, usually for smooth curves in space. Furthermore, considering pitch-yaw structure and staircase environment, we simplify joint angles in three kinds while climbing: 0°, +90°, or −90°. The relation of adjoining joints can be expressed in homogeneous matrix and transformed simply by column shift and sign change. Thus, the complex matrix multiplications can be avoided, which often occur in the traditional Denavit-Hartenberg expression. Finally, we use the novel expression to depict the six configurations in stair climbing: initial state, rising, out-reaching, shifting at turning points, tail lifting, and initializing. The verification is done on the snake robot with 18 pitch-yaw segments by WebotsTM, which could climb the stairs with 25 cm of raiser height, 25 cm of tread depth, and 100 cm of tread width. The novel representation is proved to be much less computational complexity, more intuitive and direct link to robot configurations.