Gait Generation And Power Consumotion Optimization Of Hexapod Walking Robot With Semi-Round Rigid Feet

Multi-legged walking machine, compared with wheeled or tracked locomotion, is widely recognized as a much more effective and efficient transportation vehicle, especially on complex and unstructured terrains. Hexapod robots, as a kind of legged walking machines, generally have much more superior performance than those with fewer legs in terms of less complexity of the control method, more walking statically stability and faster walking speed and therefore has already become the research hotspot. However, the legged system today has its own disadvatages, such as low payload to machine load ratio and high energy consumption. Since power is a very limited resource in autonoumous robots, it becomes urgent and imperative for researchers to explore the power-consumption optimizaition techniques. Therefore, this dissertation focues on the minimization of energy expenditure in hexapod robots'standing and walking status.This dissertation is organized as follows:The first chapter of this dissertation performs the background and significance of the project. Based on lots of domestic and foreign literature and reference, this chapter generally introduces the development of multi-legged walking robots and their gait generation techniques. The advantages and disadvantages of variable foot-force distribution methods as well as power consumption optimization methods are especially discussed in this chapter. At the end, the main research purpose and contents are illustrated.In the second chapter, the kinematic model of the robot is built, while the forward/inverse kinematic analysis is used to describe the relationship between the joints'angles/angular velocity and the foot-point positions in the body reference frame. Additional, this chapter analyse the hip misplaced problem caused by round rigid foot and provides a hip-control algorithm for restoring leg coordination. The algorithm is implemented in simulation model with a large-radius ball foot in order to evaluate how the algorithm would perform if applied to a real robot.The third chapter derived the robot's dynamic model with the foot-force distribution problem formulated. By using the joint torques as the primary variables, the distribtuion of required force and moments to the supporting legs of the hexapod robot is tackled as a torque-distribution problem. The objective function of this problem, which is constructed as the sum of the mechanical energetic cost and heat loss power, is formulated as to minimize the quadratic objective funtion with respect to linear equality and inequality constraints. In contrast to the force distribution method whose objective function corresponds to the sum of the squares of the tip-point force components, the torque distribution scheme could save the system energy cost obviously with appropriate walking velocities and duty factors of robot.In the fourth chapter, the optimal target of the robot standing posture about the dissipation power was proposed through utilizing the energy consumption mathematical model. Combining with the calculation of the foot-points workspace and the kinematic constraints, the Monte-Carlo Method was proposed to analyze the system energy consumption of the robot with different footholds. Furthermore, the protraction movement of a three-joint robot leg is optimized for minimum energy consumption. Foot-point trajectory is performed for various initial-final tip point positions of protraction by genetic algorithm. This chapter also provides analysis on parameters by simulation such as optimal stride length, duty factor, walking velocities, body height and lateral offset with various body mass and payload.In the fifth chapter, the mammal-like hexapod walking robot platform with its Human-Machine Interface are established. The hip-control algorithm lead by round rigid feet is implemented in the platform, while the power consumption experiments on standing posture and walking patterns with varies gait/structure parameters are also carried out. The optimal results of the former chapters derived from simulation are justified by those experiment.