雙足機器人轉彎步態與力回授步行步態開發

Abstract

本論文內容主要包含兩個部分，一為設計開發機器人轉彎步態，以建構雙足機器人在平面上運動的完整性。一為以機器人腳踝上的六軸力規為感測基礎，開發力回授控制的步行步態，使機器人步行具抗干擾與穩定的特性。轉彎步態開發包含原地定點轉彎與步行轉彎兩個類型，以線性倒單擺為模型，藉由質心軌跡與腳板運動軌跡的規畫，配合運用逆運動學以求得機器人雙腳上各個驅動關節的運動軌跡，同時，以零力矩點(Zero-Moment Point,ZMP)理論為基礎，在模擬環境中驗證所開發步態的可行性，並以機器人實體進行實驗驗證，確立轉彎步態的可行性。力回授步行步態是以預觀控制(Preview Control)軌跡即時生成法為基礎，藉由給定零力矩點參考軌跡，由控制器自動生成對應出預設的質心運動軌跡。同時，藉由倒單擺模型所建構零力矩點和質心加速度間關連性，以創新具物理意義的質心加速度回授調控方式，來調整機器人步行時零力矩點的位置，以確保機器人運動時的穩定性。為突顯出回授機制的性能，除了一般步行實驗外，也進行外力干擾的步行實驗，而在模擬和實體實驗中均明顯顯示出，具有回授控制機制的機器人在步行時，能將機器人機身劇烈晃動現象快速收斂至穩態以保持機器人原本的步行運動。最後，以模仿生物在遭受大干擾時會自動變換步態以求穩定運動的特性，開發出即時調控零力矩點參考軌跡與腳板運動軌跡的功能，讓機器人在必要時得以即時改變腳板踩點位置。同時，並配合前述的力回授機制，使機器人在受大外力干擾時，同步調整質心運動軌跡與變換跨步距離，建構出具更強韌抗干擾特性的步行步態，並經由實體實驗驗證其可行性。

The thesis contains two parts. One is to develop the turning gait of biped robot to construct the comprehensiveness of planar motion. The other one is to develop the walking gait of force-feedback control on the basis of six-axis force sensors installed on the ankle of each leg, so that the robot is equipped with the features of disturbance rejection and stability. The development of turning gait includes making a turn at a fixed point and making a turn while walking. Based on the Linear Inverted Pendulum Model (LIPM), the trajectories of each foot and the center of mass (COG) could be planned well. Then, the Inverse Kinematics is applied to calculate the trajectories of each actuated joints on both legs of biped robot. Meanwhile, based on the theory of ZMP (Zero-Moment Point), verify the validity of the turning gait in simulation and further in the robot experiments. The force-feedback walking gait is based on real-time trajectory generation of preview control method. Form the planned ZMP tracking reference, the controller automatically generates the corresponding trajectory of center of mass. Moreover, from the correlation of ZMP and COG state grounded the Linear Inverted Pendulum Model, the COG acceleration feedback control method, which is innovative and with physical significance, is used to adjust the position of ZMP while the robot is walking. Therefore, the stability of robot motion is ensured. In order to highlight the functions of force-feedback control, in addition to ordinary walking experiments, the experiments with interference of external force are also conducted. Both simulations and experiments reveal that while the robot with feedback control is walking, the violent vibrations of robot’s body converge rapidly to the stable extent that the robot is able to maintain the earlier walking motion. Last, the function of real-time ZMP tracking reference and foot trajectory adjustment is developed by imitating the characteristic of creatures that they are able to maintain stable motion by changing gaits automatically when encountering strong external force. Therefore, the robot is able to instantly change the stepping position of swing leg if necessary. Besides, considering the feedback control method as mentioned above together, the robot, when disturbed with strong external force, adjusts the COG trajectory and changes the stepping length simultaneously. Thus the force-feedback walking gait with a more robust characteristic of disturbance rejection is constructed. And the validity is verified by the robot experiments.