Boom Of Excavator Research Articles

The productivity and cost of harvesting whole trees from early thinnings with a felling head designed for continuous cutting and accumulation

ABSTRACT The main problem with the utilization of untended stands for energy use is that small-diameter trees are expensive to harvest, and the value of the harvest fails to exceed the harvesting cost. Until now, the equation has appeared difficult to solve, but a wood harvesting innovation – the Risupeto II accumulating felling head – which works on a continuous basis, could provide a solution to the harvesting cost problem of young stands with a dense undergrowth. The novel accumulating felling head is attached to the boom of the crawler excavator, and trees are harvested at full-tree length. The crosscutting is done later during loading by a forwarder equipped with a grapple saw. The objectives of the present study were: 1) to define the productivity; 2) produce time consumption models for the Risupeto II harvesting unit in selective thinnings and 3) to determine the harvesting cost of whole trees from the early thinnings based on the above described two-machine configuration. Time study data from the 16 study plots consisted of 3,099 whole trees where the average tree volume varied between 14.2 and 52.0 dm3 resulting in 73 m3 of whole trees. The productivity varied between 11.2 and 26.6 m3/PMh on the time study plots indicating that felling-bunching productivity was relatively high compared to the latest studies with the Nordic harvesting technology in early thinning. According to the profitability analysis, the harvesting costs could be covered by the revenue from energy wood sales.

Knowledge-Based Structure Optimization Design for Boom of Excavator

During the design optimization of the excavator boom, there are many design variables and complicated processes. The original optimization methods mainly focused on the optimization of mathematical models, and they lacked consideration in the use of domain knowledge, design-specification knowledge, expert experience knowledge, and historical examples. In order to comprehensively utilize the domain knowledge and expert experience knowledge, this study uses the optimization process analysis, uses knowledge expression and coding processing technology to encode the boom structure, builds an optimal design coding system based on knowledge guidance, and realizes the automatic optimization design of the boom structure. In the process of constructing the knowledge-oriented optimization system, to realize the reuse of the knowledge of the boom structure design in the numerical optimization iteration, a knowledge processing flowchart of the boom structure design is constructed. The concept of “shape distance” is proposed to judge the similarity feature matrix of the boom structure coding. To evaluate whether the stress distribution is uniform, a fast prediction model based on stress characteristic regions is constructed. The research results show that, under the comprehensive consideration of the four working conditions, the knowledge-guided optimization of the boom structure can avoid the deformity in the optimization process, accelerate the calculation speed of the optimization model, and improve the optimization quality of the model.

Determining the parameters of the trajectory of the bucket of mining quarries excavators

The bucket positioning of the excavator in three-dimensions (3-D) is the precondition of the robotic excavator starting automatized works. The electric excavator is one of the most widely used machinery in the mining industry, mainly due to its versatility and portability. Among the tasks performed by the excavator, there is a significant number of repetitive movements associated with moving the bucket to the unloading point and back to the face. Using automated functions to perform such repetitive tasks will not only significantly increase overall productivity, but also reduce energy consumption. This research is carried out to create a method of coordinate control of electric drives of the boom, dipper stick, and bucket of an electric excavator to perform accurate and efficient work. On the basis of the kinematic analysis of the excavator’s attachment system, the trajectory of the end of the working body can be determined from the point of view of the coordinated movement of the electric drives of the main mechanisms of the excavator. Thus, the complex algorithm of the excavator bucket 3-D position control can be carried out by coordinated control of the movement of three separate electric drives. This coordinate control algorithm was tested on the example of the EKG-8I excavator, and the results of the verification showed that this developed control method can satisfactorily perform the function of automatic control of the bucket position in three-dimensional space. Optimization of control will be further carried out based on the analysis of the energy efficiency of various possible trajectories.

Fatigue life evaluation of web butt welding structure on boom of excavator by hot spot stress approach

The working load of excavator is complex and the working environment is bad. As the main part of excavator, the boom bears a large complex load and is prone to fatigue damage. A large hydraulic excavating boom is taken as the research object in this paper, aiming at the damaged position in the platform fatigue test, that is, the web butt weld on the root of the boom, and the fatigue life of this part is evaluated by means of hot spot stress and load spectrum. The result shows that the theoretical lifetime of this part is 4148 h, which is completely agree with the equivalent life 4278 h when the cracks appeared in bench fatigue tests. Accordingly, the hot spot stress approach is suitable for the fatigue life evaluation of the boom, and its accuracy is high.

Performance enhancement of hybrid hydraulic excavator using multiple hydro-pneumatic accumulators

In this article, the heavy earth moving machinery like hydraulic excavator used in the construction and mining industries has been taken into consideration. Most of the heavy earth moving machineries used in these industries are mobile with engine as the main source of power. The work deals with two different hydraulic circuits: first the proposed one and second the conventional one, and both are studied at laboratory scale, which resembles the circuit of the hydraulic excavator. In the hydraulic circuit, out of the three hydraulic linear actuators, two are connected with hydro-pneumatic accumulators and one hydro-motor is also taken into consideration, which resembles the boom, arm, bucket and swing motor, respectively. The idea behind the proposed circuit is to store substantial potential energy during downward movement of the two linear actuators in the accumulators, which resembles the boom and arm cylinder of the excavator. The stored energy is used for upward motion of the two actuators without utilizing any energy from the main pump. For the devised strategy, MATLAB/Simulink environment has been utilized for developing the simulation model and the same has been validated with the experimental data with reasonable accuracy. The effect of accumulator volume and pre-charge pressure has been studied for optimization of the accumulator size on the validated simulation model. This concept helps in saving 14.06% energy than its conventional counterpart which does not have the energy storage elements. The linear position control of the boom and the arm actuator in the proposed circuit have been accomplished using proportional–integral–derivative control and pressure-compensated proportional flow control valve and have been achieved with reasonably accuracy.

The Finite Element Analysis of the Boom of 20-ton Backhoe Hydraulic Excavator Based on ANSYS

Taking the boom of 20-ton backhoe hydraulic excavator as the research object, this paper analyzed the strength of the boom by ANSYS software, simulated the load condition of the boom under the bucket excavation condition, and obtained the stress distribution cloud diagram of the boom. The analysis results show that the stress of the boom of the excavator is mainly concentrated on the hinge of the boom and the stick cylinder, which is the weakest link.

Electro-hydraulic velocity and position control based on independent metering valve control in mobile construction equipment

Abstract Independent metering valve control system can overcome the shortcomings of the traditional four-side linkage valve controlled system, such as poor controllability and large energy consumption, especially under the overrunning load condition. Current researches mainly focus on the velocity, pressure and energy consumption characteristics of the hydraulic system. However, with the intelligent development of mobile machinery and the continuous improvement of work quality requirements, each actuator should not only meet the velocity and output force requirements, but also achieve high positioning accuracy. Therefore, according to the independent metering valve control system and pump-valve hybrid control principle, a velocity and position combined control strategy based on mode switching is proposed to control the boom and arm of hydraulic excavator. Then, a mechanical-hydraulic co-simulation model including the whole hydraulic excavator is established to verify the strategy, predict control characteristics and determine the controller parameters. Furthermore, a test prototype based on the above principle is established, and the boom and arm operating characteristics with the proposed strategy are tested and analyzed. The results show that the hydraulic cylinders can move smoothly along the expected trajectory under the premise of low energy consumption. The operate velocity fluctuation is small and the positioning error to the target position is about 1 mm. Due to the boom cylinder and arm cylinder in the research are separately typical two and four quadrants working actuators, the research work has universal significance to smooth, high-precision and low energy consumption automation operation of various types of mobile machineries.

Research on Welding Structure with Transition Changing Faces at Cylinder Block on Boom of Medium Excavator by Means of Hot Spot Stress Approach

To investigate the cracking reason in welding structure with transition changing faces at cylinder block on boom of medium excavator during fatigue test, the finite element model of boom was established by using ANSYS finite element software. The stress distribution of the boom was obtained under fatigue loading spectrum of medium excavator. In addition, the fine model of welding structure with solid element length 2 mm was set up with the help of sub-model technology in ANSYS software to get the accurate hot spot stresses around welding toes. Finally, the fatigue life of this welding structure was calculated according to IIW fatigue class. The results show that the stress gradient along with the thickness direction can be acquired by fine three-dimensional finite element sub-model of welding structure. Therefore, the weakest point in thick plate was located, which was in accordance with the experiment result.

The gravitational potential energy regeneration system with closed-circuit of boom of hydraulic excavator

Considering the disadvantage of higher throttling loss for the open-circuit hydrostatic transmission at present, a novel gravitational potential energy regeneration system (GPERS) of the boom of hydraulic excavator, namely the closed-circuit GPERS, is proposed in this paper. The closed-circuit GPERS is based on a closed-circuit hydrostatic transmission and adopts a hydraulic accumulator as main energy storage element fabricated in novel configuration to recover the entire gravitational potential energy of the boom of hydraulic excavator. The matching parameter and control system design are carried out for the proposed system, and the system is modeled based on its physical attributes. Simulation and experiments are performed to validate the employed mathematical models, and then, the velocity and the pressure performance of system are analyzed. It is observed that the closed-circuit GPERS shows better velocity control of the boom and response characteristics. After that, the average working efficiency of the closed-circuit GPERS of boom is estimated under different load conditions. The results indicate that the proposed system is highly effective and that the average working efficiency in different load conditions varied from 60% to 68.2% for the experiment platform.

Modeling and control of hydraulic excavator’s arm

In order to find a feasible way to control excavator’s arm and realize autonomous excavation, the dynamic model for the boom of excavator’s arm which was regarded as a planar manipulator with three degrees of freedom was constructed with Lagrange equation. The excavator was retrofitted with electrohydraulic proportional valves, associated sensors (three inclinometers) and a computer control system (the motion controller of EPEC). The full nonlinear mathematic model of electrohydraulic proportional system was achieved. A discontinuous projection based on an adaptive robust controller to approximate the nonlinear gain coefficient of the valve was presented to deal with the nonlinearity of the whole system, the error was dealt with by robust feedback and an adaptive robust controller was designed. The experiment results of the boom motion control show that, using the controller, good performance for tracking can be achieved, and the peak tracking error of boom angles is less than 4°.