Motion analysis and path optimization of multi-DOF automatic shotcrete manipulator

Shotcrete support, widely used in underground heading and supporting, has the advantages of high strength and low cost.In order to realize the fully automation of shotcrete support operation and solve the problems of poor quality and low efficiency, a full-automatic multi-DOF (degree of freedom) shotcrete manipulator with redundancy and high flexibility was designed and implemented.The space kinematics model of shotcrete manipulator was established based on D-H method and the space pose transformation matrix was obtained through the forward and inverse kinematics analysis, which lay a foundation for the automatic control.Aiming at the uniformity of the sprayed surface, the shotcrete path planning model was established using the environmental grid method to investigate the influence of the motion parameters and motion modes on the shotcrete effect.In addition, the control system of multi-DOF shotcrete manipulator was developed and the motion control laboratory experiment was carried out on the fully-automatic shotcrete manipulator platform to investigate the performance of the fully automatic shotcrete manipulator.The results show that the kinematic model can accurately describe the spatial motion of the manipulator.In the motion control experiment, the errors of the pose parameters θ1, θ2 and θ3 are large, while the other errors are small, which basically satisfy the control performance requirements.The repeated sprayed area is concentrated at the intersection of the shotcrete path, and the non-sprayed area is located at the periphery of the sprayed area.And the "spraying periphery" method can be introduced to patch up the surrounding non-shotcrete area.The uniformity of the sprayed area is affected by the diameter and the transverse distance.The increase of the shotcrete diameter and the transverse distance will reduce the repeated shotcrete area and increase the non-shotcrete area.With the motion mode of shotcrete changing from l=D motion to l<D/2 motion, the proportion of non-shotcrete area becomes smaller and the proportion of repeated shotcrete area is larger.The better shotcrete effect can be obtained under the condition that the transverse distance is 1/2 of the shotcrete diameter. © 2020, Editorial Office of Journal of China Coal Society. All right reserved.