Analysis And Evaluation Of Backhoe Hydraulic Excavator Working Area Digging Performance

The working envelope of a hydraulic excavator is its working area,where the digging force is exerted to overcome the digging resistance to complete the task,so the digging performance is a key indicator in the analysis and evaluation of the excavator design.Therefore,the size of the digging force and the matching of the limiting factors affecting the digging force will be the focus of the analysis and evaluation of the digging performance.This paper starts from the matching characteristics of the theoretical digging force to the measured digging resistance,reveals the shortcomings of the compound digging force model,and lays the foundation for the establishment of the limit compound digging force model.And the research on the key evaluation index of digging performance,the main digging area definition problem,is carried out as follows:(1)The problem of matching the measured digging resistance with different theoretical digging force models.Based on the distribution rules of the measured digging resistance of the two working conditions,the smaller resistance is eliminated and the stage where the cutting and loading resistance is higher,which reflects the digging performance,is retained as the matching section.The limit digging force of the bucket,the limit digging force of the stick and the compound digging force under different digging modes are calculated according to the digging attitude of the matching section.The measured digging resistance is matched with the single cylinder limit digging force and the compound digging force from the magnitude of the force,as well as the limitation factors of the working devic e that affect the digging force.The results show that the limit digging force model can better characterise the digging force exerted by the excavator in single-cylinder operation,while the compound digging force model lacks consideration of the resistin g moment and leads to small calculation results.Matching the work device limitations for the different digging methods shows that the latching limit of the boom cylinder is too high for this model,indicating that the latching capacity is not sufficient,making it impossible to fully exploit its digging capacity.(2)To address the shortcomings of the compound digging force model.Based on the research of digging resistance characteristics and the kernel density non-parametric estimation method,the inertia interval of the moment coefficient load is selected.The concept and solution method of the limit compound digging force is established based on the main value interval of the compound digging direction angle and the inertia interval of the moment coefficient,and its correctness is verified.Based on the measured t rajectories of two digging conditions,the limit single-cylinder digging force,the compound digging force and the limit compound digging force solved by different digging force models are analysed and compared.The results show that the maximum limit compound digging force is about 20%larger than the compound digging force,which can more accurately characterise the change trend of the trajectory digging force,and give a method to characterise the trajectory digging force.In addition,the results show that the limit compound digging force has the best digging performance in the trenching operation.(3)The problem of defining the main digging area for the evaluation index of digging performance.Based on the ratio of the work device mechanism and the for ce arm curve,the force arm curve section in the main digging condition is selected.The concept of force arm coefficient is introduced and the main digging force arm proportioning scheme is established according to the change of force arm caused by different operation methods.Based on the working area mapping method,the working area of each ratio scheme is evaluated and the main digging area index one is constructed.The force mapping of the limit digging force of the bucket,the limit digging force of the stick and the limit compound digging force of the main digging area and the whole area of the different digging methods are analysed and compared to obtain index two.Combined with the mapping of the respective limiting factors affecting digging force,indicator three is obtained.The three indicators are combined to define the main digging zone and to give the main digging zone defined by the force arm factor for the evaluation of the best digging performance in each digging method.