Determination of the Area of Energy-efficient Working Equipment Position and Effective Digging Radius of Hydraulic Excavators in Open-pit Mining

Since the end of the last century, a significant number of hydraulic excavators have arrived on Russian quarries. Most of these excavators are equipped with backhoe operating equipment. The widespread use of such excavators in open-pit mining proves their exceptional efficiency. However, at the same time there is no clear understanding of the conditions under which a hydraulic excavator will be most effective: a theory of the face block of hydraulic shovels has not yet been developed. The available scientific studies are limited to determining the rational height of the excavation layer for efficient operation. If to take the quality of preparation of rock mass and the scheme of its loading into dump trucks as external parameters, i.e. not depending on the features of excavator design, then the position of its working equipment relative to the rock block has a decisive influence on operation of the hydraulic drive and fuel consumption. This is due to the changing value of digging force at various points of the bucket teeth position in the range of their possible positions at constant power of the hydraulic drive. Thus, application of optimal position of hydraulic excavator working equipment elements (bucket, arm, and boom) relative to the rotary platform and the rock massive during the digging cycle allows both to reduce fuel consumption and to increase the digging force. The application of the developed methodology is promising in terms of improving the energy efficiency of both individual excavation and loading units and the enterprise as a whole.

Dynamic Analysis of Working Device of Excavator under Limit Digging Force

In order to more accurately analyze the dynamic characteristics of the working device of the hydraulic excavator. The load changes on the two digging trajectories were calculated and analyzed by using the limit digging force model and the theoretical digging force model, respectively. The rigid-flexible coupling model of the working device was established in ADAMS. Taking the limit digging force (LDF) and the theoretical digging force (TDF) as the external load of the working device, the dynamic simulation of the hinge force of the working device in the two trajectories was carried out, and the structural strength analysis of the bucket was carried out by using ANSYS. The results show that the tangential force of the LDF is generally larger than that of the TDF, the hinge point force of the working device changes dynamically with the external load of the tooling, and the influence of the LDF on the hinge point force is greater than that of the TDF. When the LDF is taken as the external load, the structural strength of the bucket meets the operational requirements.

Modeling of the limiting digging force of hydraulic excavator based on resistance characteristics

Based on the resistance characteristics, a model of theoretical digging force was proposed in this paper, taking the tangential force, the normal force, and the bending moment into account simultaneously. Utilizing the relation among the normal resistance, the resistance moment, and the tangential resistance in practical digging process, three independent unknown quantities are transformed into only one variable. Afterwards, according to different digging patterns and complete machine limiting conditions, this research derived the constraint inequalities of the limiting digging force (LDF) and established the calculation models for LDF. Then, based on the value distribution laws of the digging resistance coefficient and the resistance moment coefficient, the calculation process and corresponding method of LDF under a given digging posture were obtained. Taking the digging resistance obtained by testing for 35 t hydraulic excavator with backhoe attachment as the reference, this paper compared the calculation results of the theoretical digging force for complete machine with those of the LDF model proposed in this research. The comparative results indicate that the LDF is consistent with the fact that the theoretical digging force is larger than or at least equal to the actual digging resistance. So, the LDF can exactly show the real limiting digging ability of the excavator more accurately. In this way, it can provide basis for mechanism optimization, structural strength design, trajectory planning, and control automation of the excavator.

SETPOINT OPTIMIZATION FOR THE CONTROL SYSTEM OF THE MOTOR GRADER IN HEAVYLOAD MODE

Introduction. The authors suggest the optimal tuning method foran automatic control system of the heavy motor grader blade. The demonstrated system regulates the value of digging force. Moreover, the setpoint optimization criterion is the maximum of production rate.Materials and methods. The optimal setpoint is generating to the signal estimations, specifically to the measured digging force and the wheels slip ratio during the previous stroke of the motor grader.There searchincludes:development of the blade control system functional diagram including the setpoint former;meaningful estimation of the slip ratio signal for control purposes;development of the setpoint forming algorithm for a microprocessor control unit;program realization of the motor grader workflow model and simulation;development of the algorithm to compose the lookup table containing optimal setpoint values and based on simulation results;dependence of optimal setpoint on the incoming signal estimations.Results. The lookup table of optimal setpoint values is obtained, the estimations of digging force and wheels slip ratio are presented. In addition, the authors suggest the control system structure with the optimal setpoint former and also develop the former operation algorithm.Discussion and conclusion. The optimal setpoint values are theoretically validated for the motor grader control system. The tuning method for an automatic control system of the heavy motor grader blade has the following characteristics as:the optimal control criterion as the production rate;process dynamics and stochastics;the excessive slippage time ratio.

Features of designing hydraulic excavator in APM WinMachine

The urgency of the work is due to the need for design departments involved in the design of hydraulic excavators in techniques. Allowing to reduce the weight of excavators while providing at the same time sufficient reliability. The purpose of the work: development of a technique for application in the design of excavators of calculation modules based on the use of finite elements. Research methodology: modeling of working equipment. For a hydraulic excavator with a “direct” shovel working equipment, a mathematical model for calculating effort, an algorithm and a program in an algorithmic language have been developed, which allow to determine the working area of the excavator, possible digging forces, and efforts in the elements of the working equipment. To calculate stresses in the design of the working equipment, two modeling options are proposed: the models for the Strucrure 3D computational module are compiled separately for the bucket of the handle and the boom, the interaction of the models is carried out by efforts that are determined by the specified digging forces; a complete model of all the working equipment for the calculation module is compiled, without the need to calculate the loads between the elements, the calculation is carried out directly by the digging force. For the first variant formulas of calculation of efforts in elements of the working equipment are resulted. For the second variant, it is suggested to use a plate-rod model, and recommendations are given for the implementation of the relationships between the boom, the handle and the bucket. The results of stress calculations for the working equipment are presented.

Optimum dimensional synthesis for the working mechanism of a hydraulic excavator to improve the digging performance

The direction and magnitude of the digging resistance encountered by an excavator during digging process are usually uncertain. To identify the excavator’s capability to generate digging force to overcome the digging resistance in any direction, a hexahedral actuator force space is mapped to a polygon in bucket force space with the consideration of the whole machine stability constraints of an excavator. Then this polygon is called digging capability polygon. Based on the digging capability polygon, the maximum digging force, isotropy measure of the digging force, and the full exertion proportion measures of the driving capability of the working hydraulic cylinders are defined to quantify the digging performance of any configuration of the working mechanism. Further the average values of each of these indices in the customary digging workspace are used to comprehensively assess the digging performance of an excavator. A multi-objective evaluation function is constructed using the so-called ideal point method to increase all average values of the given indices simultaneously. Optimum dimensional synthesis of the working mechanism is finished by using the genetic algorithm to solve the established optimization problem. The optimization results indicate that the average values of the maximum digging force, isotropy measure of the digging force, and full exertion proportion measures of the bucket cylinder and stick cylinder in the customary digging workspace respectively increase by 1.81%, 1.51%, 9.64%, and 15.15% relative to the initial excavator, and obvious increases in the key workspace parameters of the optimized excavator are obtained. The performance indices proposed in this research can be used to assess the digging performance of an existing excavator and further guide the new excavator design and development. The optimization method provided in this research can be used to design new excavators or improve the existing excavators.