Trajectory planning and tracking control of a seven degree of freedom shotcrete robot in coal mine roadway

During the construction process, the coal mine roadway shotcrete robot has the problems of discontinuous motions, large position errors, and low stability. In order to solve the above problems, a trajectory planning and tracking control method of a seven degree of freedom shotcrete robot in coal mine roadways is proposed. Based on the range of motion of the working arm when the shotcrete robot is stationary and the shotcrete length of the airbrush along the roadway direction, the roadway is divided into several sections to be sprayed. The robot's motion trajectory between each section and the motion trajectory of the working arm on each section are planned to ensure continuous action of the robot during the spraying process. A kinematic model of the shotcrete robot is established. Firstly, the robot's motion trajectory is planned using the cubic polynomial interpolation method. Secondly, the reference trajectory generated by the cubic polynomial interpolation is tracked and controlled using the model predictive control algorithm. It achieves precise and smooth motion of the robot in the roadway. A kinematic model of the working arm is established based on the standard D-H parameter method. The 3-5-3 section polynomial interpolation method is used to plan the motion trajectory of the robot's working arm on the section to be sprayed, so that the working arm has continuous acceleration during the spraying process. The simulation results show that the maximum position error of the shotcrete robot during its motion is 0.07 m, and the maximum directional angle error is only 0.99 rad. The overall motion speed is stable, and it can quickly return to a stable state after speed fluctuations, meeting the requirements of accurate and stable robot motion. During the motion of the working arm, the spraying trajectory, joint variable changes, joint velocity and acceleration curves are overall continuous and smooth, meeting the requirements of continuous and stable spraying actions.