Electrically Driven Large-load-ratio Six-legged Robot Structural Design And Its Mobile Characteristics Research

NASA-JPL‘s ATHLETE not only extends the knowledge horizon of humankind on large-load-ratio legged robots for interstellar exploration, but also brings the interest of research on electrically driven large-load-ratio legged robots. The electrically driven large-load-ratio legged robot does not need flat terrain on the lunar surface, and it can utilize the discontinuous walking modes to overpass the obstacles which are not traversed for wheeled robots and tracked robots. Currently, the research of electrically driven large-load-ratio legged robot in China lags behind the developed countries. Hence, to research technologies of the electrically driven large-load-ratio legged robot will be usefull to promote the development of robotics for our country and successfully carry out the interplanetary missions.Based on the hexapod and knowledge of robotics, the mobile system of electrically driven large-load-ratio six-legged robot is analyzed and designed. According to the characteristics of hexapod and the knowledge of robotics, the configuration of robot is confirmed. Based on the D-H method, the forward / inverse kinematics is analyzed for robot. The mathematic expressions of articulated rotating speed are derived for single leg. In order to improve the reasonableness on matching the drive devices and actuating devices for joints, the analysis method of articulated rotating speed is put forward when the joint rotating makes the robot to arrive at the maximum walking speed. The required rotating speed of every joint is obtained. The analysis method of articulated torque is brought forward when the equivalence is executed from the legs of the support phase to the middle line of symmetry. The required maximum output torque of every joint and the poses of robot are gained under the rated load. The simulation verification is actualized for the analysis method of articulated torque thorugh ADAMS software. Based on the aim of larger load ratio, the transmission project of joint is confirmed. The drive devices and actuating devices of joints are selected through the analysis results of the articulated rotating speeds and articulated torques. Then, the prototype of electrically driven large-load-ratio six-legged robot is developed, which lays the foundation for the experimental research of mobile characteristics of robot.The gait planning and statics analysis of robot are actualized because that the normal force of foot directly influences on the balance of robot pose and the power consumption of mobile system. Based on the configuration of robot, the walking mode and mobile gait are confirmed. The mathematical modes of foot tracks are established, and they are applied to the prototype of robot. According to the waking experiments of the robot prototype, the feasibility and correctness of the gait planning is dirctively validated. The thory analysis of the force of foot is performed under the robot gait. The mathematic model is established for the normal force of foot. Based on the force data of feet in the walking experiments, the experimental analysises of the forces of feet are carried out under the robot gait. Through comparing the theory analysis results with the experimental data on the normal forces of feet, the correctness of theory analysis results and the dependability of experimental data are validated. The excellence gait is gained. The foundation is set up for the research of power consumption of robot mobile system.In order to boost the survival ability of the electrically driven large-load-ratio six-legged robot on the lunar surface, the power consumption of mobile system is researched. Based on the dynamics analysis of robot, the mathematic expressions of articulated loads are derived for the support phase and the transfer phase. The mathematic models of power consumption are established for the single leg and robot mobile system. Considering that the tripod gait is the fastest gait and common gait for six-legged robot, the power consumption of mobile system is researched under the tripod gait. Based on the normal force data of foot from the walking experiment of tripod gait, the dimensionality reduction of statically indeterminate problem is disposed. The equal consitions of normal force under the tripod gait and the constraint conditions of stable walking are presented. The reduced mathematic model of power consumption of robot mobile system is established under the tripod gait. Then, the power consumption of mobile system is calculated. The influences are analyzed on the power consumtion of mobile system with the changes of the articulated rotating angle, high of body, and span. The ranges of articulated rotating angle, high of body, and span are confirmed under lower power consumption, which provides the data support for the lower power consumption walking.In order to carry out experimental research on the mobile charateristics of the electrically driven large-load-ratio six-legged robot, the experimental environment is builded. According to the prototype of robot, the experimental verifications are performed for the technical indicators of robot. The test results show that the prototype meets the requirements of technical indicators, and part of the performance is better than technical indicators. Then, the reasonabless and availability are validated for the theoretical analysises of the articulated rotating speed, articulated torque, and gait planning. The walking experiments of the prototype of robot are actualized. The influences are analyzed on the average power consumption of robot mobile system with the changes of gait parameters. Then the correctness of the theory analysis of mobile system power consumption is validated.