結合多體動力學及限制型卡曼濾波器建構輪腳機構地面接觸力估測

Abstract

本文主要探討多連桿輪腳複合機構之外力估測，此輪腳機構為五連桿內接七連桿的雙自由度機構，可以透過連桿幾何形狀的主動控制，在輪模式及腳模式平滑轉換，此機構特性讓新型四足輪腳複合機器人得以在平坦地形上使用輪型式移動，在崎嶇地形則切換至腳模式，藉由步態選擇、踏點控制或是跳躍的方式，跨越障礙物，為使足類機器人可以在各式各樣未知的地形上穿梭，需要知道機器人目前的機身狀態，並透過狀態資訊即時更新命令，而足類機器人的機身動態主要取決於足部末端與地面的接觸力，由於此輪腳複合機構較複雜，且因應輪模式下連續旋轉的限制，不易在機構末端安裝力感測器，因而無法直接取得機構末端與地面接觸的交互作用力，本研究使用間接的方式取得地面接觸力。 本研究透過多體動力學方式建構輪腳機構之動力學模型，模型主要透過幾何限制以及接觸限制條件約束系統運動行為，由於實際系統中存在許多其他未知的干擾因素，以及無法建模的損耗，因此設計一個具有限制條件的卡曼濾波器，不僅確保在使用感測器量測值更新模型預測之系統狀態時，仍滿足系統設定之限制條件，且可同時修正模型預測之接觸力。

This paper mainly discussed the ground reaction force estimation of a complex 11-linkage and closed-chain leg-wheel module. This leg-wheel module has two degrees of freedom and is capable of transforming between wheel mode and leg mode rapidly yet smoothly. Therefore, the new quadruped composed of 4 leg-wheel modules is able to cruise on flat terrains with wheels efficiently, while traversing uneven terrains in leg mode. In order to enable the legged robot to traverse diverse unknown terrains, it is crucial to track the status of the robot. The dynamic of the legged robot mainly depends on the ground reaction forces and the contact status. Due to the complexity of the leg-wheel module and the limitation of continuous rotating in wheel mode, it is difficult to mount force sensors on the legs. Therefore, in this paper, we establish the dynamic model of the leg-wheel module using the multibody dynamic approach. The contact-constrained Kalman filter developed in this paper can not only ensure the constraints are satisfied through the measurement update, but also correct the contact forces predicted by the dynamic model.