Structure Design And Stability Analysis Of Mobile Humanoid Service Robot

With the growing popularity of the professional and home service robot, the technology of humanoid service robot got rapid development. Although service robot brings great convenience to human people, the working environment is so complicated that potential security risks exist. The main purpose of this paper is to design a new service robot, two main aspects are studied. One is designing the structure of the mobile humanoid service robot, and the other is to analyze its static and dynamic stability.First, the dimension scale of human’s upper body is determined by ergonomic factors. According to the principle of anthropomorphic, lightweight and safety, the design of mechanism of each joint, mainly including neck, arm, waist, mobile chassis and appearance, were finished. And the selection procedure of motors and reducer were also given.Next, the mathematic model of robot is constructed. The kinematics of mobile platform and the upper human-like body are studied according to screw theory and the dynamic modeling of the whole robot is presented by Lagrange equation. The importance of waist joint to the work space is discussed and the influence of chassis and manipulator movement on the waist moment is studied.Then, Co G Projection Method is selected to calculate static stability of robot and the waist static force analysis is finished by simulation in an extreme position. ZMP(Zero Moment Point) criterion is also applied to analyze dynamically stable of robot. And the paper analyses both disturbances from the cart motion and external disturbances due to interaction with the environment. In order to analyze the balance of the robot and to avoid tipping over, different situations are tested and the appropriate dimensions of the cart are estimated(relying on the ZMP calculation). Following that, on the basis of time and energy optimal, a multi-objective optimization modeling of the whole body motion planning is presented. Each joint motion trajectory is parameterization by B-spline and the interpolation time interval is selected as optimization variable.Finally, based on the Pareto theory, Non-dominated Sorting Genetic Algorithm is selected to solve the optimization problem. Moreover, the definition of dominance is modified in order to solve constrained multi-objective problems efficiently. And in the real world application, the decision maker is not interested in overall Pareto optimal front since the final decision is a unique solution. Considering the above problem, the reference point is used to guide the search toward the interesting parts of the Pareto optimal region based on the decision maker’s preference. The efficacy and usefulness is assessed by two standard test functions. Using the modified algorithm solve the motion planning problem mentioned above, and the next is comparative analysis of the optimization result by considering stability or not. And the result is indicated that the stability constraint has a great significant on improving the dynamically stable of robot. The motion cooperation planning is simulated by virtual prototype in software of ADAMS.