Research On Mechanism Design And Control Method Of Spherical Robot With The Ability To Change The Center Of Mass Radiall

Spherical robot has the characteristic of high reliability and flexibility,as well as low energy consumption due to its special structure and motion mode.Therefore,spherical robot has greater development potential compared with traditional mobile robot.With the rapid development of the robotics field,the increasingly complex task environment requires spherical robots to have diversified adaptability in the face of different task requirements(such as long endurance,high mobility,etc.).However,the lack of this ability has become the main constraint for the development of spherical robots.The heavy pendulum eccentric torque drive mechanism is a widely studied driving mechanism of spherical robot,and its driving principle is that the circumferential change of the center of mass of the spherical robot caused by the circumferential movement of the heavy pendulum.The research idea is to increase the range of motion of the heavy pendulum inside the spherical robot,so that the heavy pendulum has the ability of circumferential and radial motion at the same time.It can not only enables the heavy pendulum to realize the conversion between the upper and lower hemispheres,that is,realizes the traditional heavy pendulum drive and the new inverted pendulum drive,which enriches the driving modes of the spherical robot,but also the radial motion of the heavy pendulum under the two different driving modes can make the motion of the spherical robot present different characteristics,which provides the basis for improving the adaptability of the spherical robot to the needs of diverse tasks.In this paper,the spherical robot having the ability to change the center of mass radially is taken as the research object,and the mechanism design of the robot,the construction of dynamic model,the motion characteristics analysis and the motion control strategy are deeply studied in this paper,so that the spherical robot can give full play to its structural advantages,and its adaptability to the needs of diverse tasks can be greatly improved.The main work is as follows:(1)Design and research of the spherical robot having the ability to change the center of mass radially.The radial change configuration of the center of mass of the heavy pendulum is integrated with the spherical robot structure that is based on the heavy pendulum eccentric torque drive mechanism,and the overall configuration of the prototype is proposed.Through the low velocity impact experiments and quasi-static plate compression experiments after impact,the damage to the spherical shells of spherical robots after falling from different heights in the actual application environment is simulated,so as to meet the requirements of unstructured environment.Based on the Hashin criterion,the stress distribution,structural deformation mode and energy dissipation mechanism of the spherical shell under impact are analyzed in order to provide reference for the design of high-strength spherical shell structure.The BYQ-GS spherical robot with the ability to change the center of mass radially is developed according to the above research results,which not only has the traditional heavy pendulum driving mode,but also has the new inverted pendulum driving mode.Under the two different motion modes,it can both realize the radial centroid change function.(2)The construction of spatial multibody dynamics model for unstructured task environment.According to the simplified omni-directional motion models of the two different motion modes,the radial variation of centroid is integrated into the construction of dynamic model.The spatial multibody dynamics model for idealized task environment of the different motion modes are constructed by using the first type of Lagrangian equation.The influencing factors of the spherical robot during the motion process are classified,and the model of controllable influence factors are established before they are integrated into the ideal dynamic model to realize the construction of spatial multibody dynamics model for unstructured task environment in two different motion modes.Experiments show that compared with the dynamic model without considering the influencing factors of the task environment,the spatial multibody dynamics model for unstructured task environment can make the stability of the motion of the spherical robot in the two motion modes increase by 43.64%when the motion speed increases to 3m/s,and the stability of the motion of the spherical robot having the ability to change the center of mass radially is effectively improved.(3)Research on the motion characteristics of the spherical robot having the ability to change the center of mass radially.According to the demand for the radial change of the center of mass during the task completion process and the task characteristics in the unstructured environment,the motion experimental verification of spherical robot in different motion modes,different centroid change modes,different motion speeds and different slopes are completed.According to experimental results,the influence of the inverted pendulum driving mode and the radial change function of the mass center on the control performance,motion ability and energy consumption level of the spherical robot is comprehensively analyzed and summarized based on 4 control performance indicators:the convergence speed,overshoot,stability and response speed of the control system,and 2 sports ability indicators:climbing ability and steering ability,and energy consumption.Moreover,the correlation model between the motion requirements of the spherical robot and the radial position of the center of mass is constructed,which provides the basis for the selection of the driving mode and the radial position of the center of mass of the spherical robot having the ability to change the center of mass radially for different tasks.(4)Research on motion control strategy of spherical robot with the ability to change the center of mass radially for actual task environment.Based on the spatial multibody dynamics model for unstructured task environment of spherical robot with the ability to change the center of mass radially,the integral sliding mode and fractional calculus is integrated into hierarchical sliding mode control,and the unknown uncontrollable disturbance caused by the task environment and the radial change of the mass center in the process of motion is adaptively evaluated and compensated to construct the fractional-order adaptive integral hierarchical sliding mode control method.Experiments show that compared with the adaptive hierarchical sliding mode control,when the motion speed increases to 3m/s,the fractional-order adaptive integral hierarchical sliding mode control method can make the convergence speed,overshoot and stability of the control system under two different driving modes increase by 22.64%on average,so that the motion control performance of the spherical robot having the ability to change the center of mass radially is effectively improved.