Modeling And Motion Control Of Omnidirectional Wheelchair Bed

With the extensive research and rapid development of robotics technology,robots with various functions come into people's vision one after another.The omnidirectional mobile wheelchair bed is an intelligent medical and nursing robot,which can be switched to bed for rest or wheelchair for mobile tools.Wheelchair bed has flexible motion performance,which can keep the attitude unchanged and move in any direction.It has greater motion advantage in limited space and narrow workplace,but it also needs higher control accuracy and robustness.Therefore,it is of great significance to study the motion control of omnidirectional mobile wheelchair bed.In this paper,the omnidirectional mobile wheelchair bed is taken as the research object,and the kinematics and dynamics models are built according to its geometric structure and motion characteristics.Aiming at the problem of Mecanum wheel skidding in wheelchair bed motion,an Active Disturbance Rejection Backstepping Controller(ADRBTC)backstepping controller is designed.Aiming at the uncertain parameters and disturbance in wheelchair bed control system,a neural network adaptive sliding mode controller(NNASMC)is designed based on the dynamic model.In addition,an omnidirectional mobile wheelchair bed simulation platform based on Robot Operating System(ROS)and Controller Area Network(CAN)bus communication is built,and a closed-loop control system of the wheelchair bed is built based on visual feedback.The motion control experiments are carried out on the omnidirectional mobile simulation platform and the wheelchair bed platform,respectively.The main content of the paper is divided into the following aspects:(1)System analysis and modeling of omnidirectional mobile wheelchair bedAccording to the geometric structure and motion characteristics of omnidirectional mobile wheelchair bed,the kinematics model and dynamic model are established.Considering the wheel skidding disturbance,model parameters and disturbance uncertainty,the mathematical model is further analyzed.An improved particle swarm optimization algorithm(PSO)is used to optimize the kinematics model by offline identification of Jacobian matrix parameters.The identification results also show that the improved PSO has faster convergence speed in the process of objective function optimization.(2)Trajectory Tracking Control for Omnidirectional Mobile Robot in presence of Wheel SlippingAiming at the problem of wheel skidding disturbance in the motion of omnidirectional mobile wheelchair bed,an ADRBTC controller is designed.The ADRBTC controller combines active disturbance rejection control(ADRC)technology with backstepping control technology to estimate and compensate the skidding disturbance from longitudinal control,lateral control and attitude control respectively.The stability of the closed-loop control system based on ADRBTC is theoretically analyzed by using Lyapunov theorem,and the feasibility and robustness of ADRBTC are further verified by simulation experiments.(3)Motion control of omnidirectional mobile robot based on sliding mode adaptive algorithmAiming at the uncertainties of parameters and disturbance of omnidirectional mobile wheelchair bed model,a motion control system based on NNASMC is designed.The dynamic controller is designed by sliding mode control(SMC),and the adaptive law of artificial neural network is introduced to improve the robustness and anti-interference ability of the control system.The Lyapunov stability theory is used to analyze and prove the robustness of the control system,and the stability of the NNASMC control algorithm is further verified by simulation experiments.(4)Verification and analysis of omnidirectional mobile wheelchair bed control systemAccording to the chassis structure of omnidirectional mobile wheelchair bed,an omnidirectional mobile wheelchair bed simulation platform based on ROS and CAN bus communication is built.The control performance of NNASMC is validated on the simulation platform of wheelchair bed.The experimental results show that NNASMC has higher control accuracy and stability than SMC and PID.The closed-loop control system of wheelchair bed is built by using the method of visual positioning feedback position information.The effectiveness of the omnidirectional mobile wheelchair bed motion control system based on visual feedback is verified by the motion control experiment.