Study On Optimal Digging Trajectory Planning For Pmining Shovel Autonomous Excavation

Mining shovels play a key role in open-pit mining industry which are widly used in removing and loading minerals.Not merely the complextity of the digging conditions but also the working experience and the driving fatigure of the operators would significantly affect the efficiency,power consumption and frequence of breakdowns of the equipment in digging operations.Therefore,there is an ongoing imperative to realize steady digging process with high efficiency in uncertern and extreme working conditions.Automantion is seen as one of the strategies by which improvements can be realized.As different digging trajecroty results in different working performance,the optimal digging trajectory planning aiming at efficient and energy-saving digging can be seen as one of the basic technique to realize the fully automated operation of mining shovels.The optimal digging trajectory planning for autonomous mining shovel was studied in this research suppoted by the National Natural Science Foundation of China Program“Research on self-adaptive control and electro-mechanical coupling dynamics of multi-crawler mechinaries.”(No.51775225),Shanxi Province coal-based key science and technology projects(No.MJ2014-02)and National Natural Science Foundation of China Program“Research on key technology of Autonomous off-road vihecle Operations in unstructural terrain”(No.51875232).The WK-55 type mining shovel was taken as the research object in this study,the dynamic model was built and verified for its working device in the first step,based on which,a method to predict the payload inside the bucket was established.Field tests were taken in PingShuo mine in Shanxi Province so as to analyse the working performance of operating mining shovels.Taking the dynamic model and the working limits of working device into considerarion,a two-stage strategy for digging trajectory optimization was constructed and verified through Discrete Element Mechod(DEM)-Multi Body Dynamic(MBD)co-simulations.In the part of literature review,the research achievements on digging trajectory optimization were summarized in the first step.Secondly,taking the operational charactristics of other excavation equipment such as hydraulic excavator and loader into consideration,the advantages and disadvantages of techniques of dynamic modeling,payload online estimation and co-simulation were analyzed.At last,the research route of optimal digging trajectory planning for mining shovel was established.On the base of Denavit-Hartenberg(D-H)convention and D’Alembert’s principle,a 2DOF dynamic model of mining shovel working device was constructed.One step further,a mechanical-electrical model was built.A scale model of WK-55 mining shovel was established serving as the testing device to verify the reliability of the dynamic model.Four digging conditions which covered high speed,medium-high speed,medium-low speed and low speed were applied for the verification.By analyzing the test data and calculation results,the value of R~2 between designed and tested trajectory were higher than 0.99.Additionally,the value of R~2 between designed and tested power consumption were higher than 0.85.Those comparison results indicated the validity of the theoretical dynamic model.During the verification process of the dynamic model,it was indicated that the prediction of the payload on the base of the dynamic model can’t provide accurate results.In order to improve the accuracy and reliability of the payload estimation,static equilibrium was introduced for the calculation.Scale model tests were applied for validation of the payload estimation method.The test results showed that the method established in this study could effectively predict payload with acceptable accuracy.After getting the dynamic model and payload estimation method prepared,the method for recognising repose angle of the piled up material was set up on the base of the lidar technique.Besides,the distance and orientation between the mining shovel and the piled up material could be gained during the scanning process of the piled up material.For the purpose of getting the optimal digging trajectory planning more practically significant,field test had to be taken in AnJiaLing(PingShuo mine)in Shanxi Province so as to get the limitations of working performance and the operation modes of WK-55 type mining shovel.Taking the geometry conditions,working performance limitations and mechanical-electrical coupling charactors as restraints,a two stage strategy for optimal digging trajectory planning was established in this study for the purpose of higher digging efficiency and lower power consumption.In order to validate the optimization results,the method of DEM-MBD co-simulation was taken.To be more specific,the virtual prototype of WK-55 mining shovel was applied in the co-simulation for five different digging conditions.The simulation results matched with the theoretical optimization in a high degree,which validatetd the effectiveness of the optimal digging trajecroty planning method.It can be concluded that an intigrated digging trajectory optimizaiton process for automous mining shovel was accomplished in this study.Serving as the base for the optimization,the dynamic model of the working device was constructed in the first place.Then,a scale-model-based testing system was designed and constructed to validate the dynamic model and the new payload estimation method.In order to set up the restraints for the optimization,lidar technique was applied to recognize the digging condition.Besides,field tests were taken in the mining site in order to get the limitations and mode of the digging operations.At last,after all conditions prepared,low power consumption and high digging efficiency were chosen as the goal for the optimization and a two stage strategy was applied to realize the optimal planning of the digging trajectory.Finally,DEM-MBD co-simulation was applied to validate the effectiveness of the optimization.It can be safely summarized that systemetic and in-depth study was carefully implemented on the topic of optimal digging trajectory planning for autonomous mining shovel in this research.This research provides technique reference for realizing fully automation of shovel operations,which is significantly important for improving the level of automantion and robotic for mining shovels.