Research And Realization Of Trajectory Tracking Control System For Mowing Robot

Lawn is an important part of urban greening,as well as an important facility in parks,courts,and other places.It needs regular pruning,but it has the characteristics of large area and wide range,resulting in high cost of manual pruning.Therefore,it is a general trend to explore new intelligent and humanized low-cost pruning methods.In this context,mowing robots emerge at the right moment.After twenty years of development,they basically have the ability of self-mowing and can maintain some ordinary family courtyards.However,in the face of complex environment,there are still omissive mowing and re-mowing.The core of grass mowing robot includes path planning and track tracking,which complement each other.However,only an accurate and efficient track tracking control system can make path planning meaningful and reduce the phenomenon of missing and recutting of grass mowing robot in complex environment.Under the above background,in order to reduce the phenomenon of missing cutting and recutting in the mowing process of the mowing robot and realize the accurate and efficient tracking of the mowing path,this topic focuses on the trajectory tracking control of the mowing robot,which is summarized as follows:1.Studied the mowing robot mobile platform and mathematical model.A mobile platform scheme of mowing robot with three wheels differential driving was determined,and the kinematics model,dynamics model and motor driving model of mowing robot were deduced in detail under this scheme.The Extended State Observer(ESO)is designed for the unmodeled disturbance and external disturbance in the motor.Finally,the validity is verified by MATLAB simulation.2.The trajectory tracking control algorithm of mowing robot is studied.Firstly,the outer loop speed controller of mowing robot based on kinematics is designed.Secondly,the inner loop speed control algorithm based on Exponential Reaching Law(ERL)sliding mode control is studied,and the control parameters are optimized by Particle Swarm Optimization(PSO).The simulation results show that,the dynamic performance of this algorithm is better than that of PID controller optimized by PSO,but there is still room for improvement.Therefore,based on the Fractional Power Rate Reaching Law(FPRRL),this paper presents an improved Fractional Power Rate Reaching Law.IFPRRL),and compared with PID,EERL and FPRRL,the results show that the improved algorithm has better dynamic index than other algorithms.Finally,the outer ring and inner ring speed control algorithm of speed controller,the formation of double closed loop trajectory tracking control algorithm,simulation results show that this design of double closed loop trajectory tracking algorithm can effectively track the desired trajectory,and have good robustness,the sliding mode control algorithm is designed so that chattering also got good control.3.The hardware and software of the mowing robot track tracking control system are designed.It includes overall design,controller selection,power module,drive motor and drive circuit design,rotary encoder selection,main program design,track tracking control algorithm programming and mileage calculation,which lays the foundation for the algorithm verification through experiments.4.Carried out the grass-cutting robot track tracking experiment.The experiment is divided into three parts.The first part is the driving motor speed tracking experiment based on IFPRRL sliding mode control algorithm.The experiment shows that the dynamic index of the algorithm is better than that of PID control.The second part is the straight-line tracking experiment of mowing robot,which verifies that the algorithm designed in this paper can effectively coordinate the left and right wheels and has the potential of tracking complex paths.The third part is the indirect type cutting grass trajectory tracking experiment,the desired trajectory of the straight-line length is 2 m turning radius of 0.5 m,the experimental results show that the mowing robot trajectory tracking control system designed by this paper can effectively track the predetermined circuitous track type cutting grass,horizontal and vertical error can be within0.15 m,with the potential and value of engineering application.