Designing And Molding For An Eccentric-type Legged Hexapod Robot

As breakthroughs in key technologies of mobile robotics are made constantly, and developments in many industries in our country such as aerospace, adventure and rescue equipments, mine safety, and nuclear industry are speed-up rapidly, types of mobile robots that could walk automatically and surmount obstacles in fields and rough terrain (such as scene of mine accidents and earthquake ruins) are needed urgently. In this paper we brought up of an eccentric-type legged hexapod robot—ELHR, according to characteristics of irregular terrain and based on other researchers' previous study. ELHR uses elastic eccentric circle instead of the traditional rigid rod structure as its walking mechanism. Elastic eccentric circle structure has been proved could relief the body toss and power fluctuations which would become strong while using rigid rod. And moreover, the robot's mechanical structure is designed symmetrically, walking mechanism is designed redundantly with six legs, and control system is designed modularly. With those characteristics the robot could adapt fields and some easy rough terrain.In this paper we discussed the designing and molding of ELHR in mainly of the following five parts. Firstly, kinematics is discussed. We descried mobile robot's position and orientation in the reference coordinate, analyzed forward and inverse kinematics model of our robot in the plane coordinate, and found out the relationship between its legs'(actually their axis') speed and the robot's (actually its centroid's) speed. Secondly, kinematics and dynamics of the eccentric-type leg are analyzed. While the eccentric wheel rolling across the ground, the height and speed of its axis will change by time, we analyzed the relationship between size, speed and actuation degrees of freedom of the eccentric leg and the legs'(actually their axis') speed in kinematic analysis, and the contribution of motor force to the robot (actually its centroid) in dynamics analysis. Thirdly, gait planning is given. According to traditional tripod gait, tetrapod gait, and the characteristics of eccentric-type leg, we design a set of gait fit for ELHR. The set including basic gait—walking forward or backward, and turn in left or right, and gait for climb and down stair. Fourthly, some ideas in control system designing are presented. This paper main introduced the designs of code-counter and directions determine circuit, and the dynamic PWM control method in this part. Finally, experimental verification and analysis of the robot model and the gait planning are given. Then the robot's obstacle-surmounting capability is been analyzed. Influence on obstacle-surmounting capability and other performances by the size and the main factors of the robot also are given in this part.According to the project and this paper, the eccentric-type leg structure is proved to be a very effective walking mechanism for wild fields and rough terrain. By owing symmetrical mechanical structure, redundant walking legs and effective control system, ELHR could walk straight, turn left and right by using a set of gait. The maximum speed of 0.311m/s, also could surmount obstacles as high as 95mm (76% of the robot's height).