| With the development of society and the continuous progress of science and technology,all kinds of robots have gradually entered people's life,production and work.It is more and more urgent to use small mobile robots in the fields of urban disaster relief,counter-terrorism,military reconnaissance and so on.However,it is difficult to balance the small mobile robot in the aspects of miniaturization,movement efficiency,adaptability to complex unstructured environment.This paper takes the new mobile mechanism of mobile robot as the starting point.Aiming at the shortcomings of mobility,passing and miniaturization of small mobile robot in unstructured and complex terrain,a new type of transformable wheel-legged mobile robot with complex terrain is proposed.The key issues of the mobile mechanism,mobile platform performance,kinematics,dynamics and stable motion control methods of this new mobile robot are deeply studied,by adopting theoretical tools such as mechanism,optimization,control and computer simulation.The main research contents are as follows:1)Through the analysis and research on the design scheme of the existing transformable wheel,a new design and optimization method of transformable wheel mechanism based on active/passive combination,which inspired from spatial folding mechanism and metamorphic mechanism is proposed.A new type of single drive transformable wheel mechanism with hinged multi-four-bar linkage mechanism is designed,and its transformation principle is analyzed.Aimed to minimize the driving moment and maximize the transformation ratio,the optimal design parameters of the transformable wheel are obtained by means of mechanical and geometric constraints.2)According to the adaptive environment of the robot and the structural characteristics of the transformable wheel,the assembly and layout scheme of symmetrical whole machine driven by double wheel differential speed is designed.The stability and reliability of the robot mode switching is ensured without adding additional drive.The motion pattern and basic characteristics of the robot under typical motion are obtained by means of kinematics method.According to the characteristics of the nonholonomic system,the kinematics and dynamics models of the robot under the wheeled motion state are derived,which provides a theoretical basis for the stability control of the whole machine.3)Aiming at the stability control of transformable wheel robot,the formula for calculating the tilting angle and the critical tipping condition of the robot are derived from the point of view of mechanics by using the stable cone method.Combined with the dynamic method,the stable motion characteristics of the robot with oblique plane and obstacle surmounting are obtained.From the perspective of control.The method of representing the position and pose error of robot is derived,and the robot position and attitude stabilization controller based on Lyapunov direct method is designed.4)The overall architecture and control scheme of the transformable wheel robot system are established,and a prototype of transformable wheel robot is designed and built.The feasibility and effectiveness of the controller are proved by Matlab Simulink simulation.The experiment of robot motion performance and stability,motion mode switching and obstacle-negotiation performance have been completed.The experiments show that the robot has excellent obstacle-negotiation performance and high efficiency and stable motion ability,which combines the advantages of wheel and leg movement.The experimental results provide an effective solution for the design of related robots,and also provide a useful reference for the design of other mobile robots. |
PDF Full Text Request