Wheeled Mobile Robot For Variable Configuration Design And Cooperative Handling Control

For the current situation of single-vehicle carrying capacity is limited,the super-large and heavy-duty transportation is developing towards the multivehicle collaboration.The multi-agent collaboration technology can lay a foundation for the environment perception,autonomous decision planning and high-precision collaborative control of multi-vehicle collaborative heavy-duty transport platform and improve the efficiency of oversized cargo transportation.In this paper,a variable configuration modular wheeled mobile robot is designed for multi-agent cooperative transportation system,and the trajectory tracking control of two wheeled mobile robots cooperative transportation system is also studied.Firstly,a variable configuration modular wheeled mobile robot is designed for the future multi-agent cooperative transportation system of oversized cargo transportation.The robot has two states of folding and unfolding.When folding,the wheel is retracted to the inside of the car body.At this time,the whole wheeled mobile robot becomes a cube,which is convenient for storage,handling and transportation.In addition,wheeled mobile robots can be combined into multiple intelligent cooperative transportation platforms according to the requirements of transportation tasks,such as 2×2 type,3×3 type,etc.,to jointly complete cooperative transportation tasks.Secondly,based on Udwadia-Kalaba theory,two kinds of dynamic closedform modeling methods for multi-body mechanical systems are summarized,namely nested dynamic closed-form modeling and hierarchical dynamic closed-form modeling.In the modeling of these two methods,the multi-body system needs to be disassembled into several sub-systems.After establishing the dynamics model of each subsystem,the dynamics model of the closed-form of the multi-body system can be obtained by combining them.The two methods take the trajectory tracking system of four mobile robots as an example to demonstrate its modeling process.Nested dynamic closed-form modeling is more suitable for complex multi-body mechanical systems with strong selfadaptation,while hierarchical dynamic closed-form modeling is suitable for simple multi-body systems.Thirdly,the trajectory tracking control for dual wheeled mobile robots cooperative handling system is studied.Using the hierarchical dynamic closedform modeling,the cooperative handling system is divided into three subsystems.After the unconstrained dynamics model of each subsystem is established,the constraint equation of the cooperative handling system is designed through the coupling relationship between the subsystems.An improved control method based on analytical dynamics was used to correct the trajectory constraints of guided and followed wheeled mobile robots.The modified constraint equation was embedded into the cooperative handling system,and the constraint dynamics model of the whole cooperative handling system was established.Finally,based on the Udwadia-Kalaba equation,the analytical solution of the driving torque required by the whole system was obtained.Finally,to solve the problems of parameter uncertainty,external interference,load variation and so on,an adaptive robust approximate constraint following control method based on fuzzy optimization is proposed.By using the fuzzy description of uncertainty,the gain design of the adaptive law is transformed into a constrained optimization problem which minimizes the average fuzzy system performance and control cost.The proposed adaptive robust control can ensure the uniform boundedness and uniform ultimate boundedness of mechanical systems under uncertain conditions and minimize the average fuzzy system performance and control cost.