Virtual prototype simulation of hydraulic shovel kinematics for spatial characterization in surface mining operations

Koivo A.J.

To use construction machines effectively in the dark, severe weather, or hazardous and/or unhealthy environments, their operations should be controlled automatically. It can be realized if the kinematics and dynamics of the machine are understood. To help achieve this goal, the kinematics of specific construction machines—excavators (backhoes and loaders)—are investigated here. A systematic procedure is presented to assign Cartesian coordinate frames for the links (joints) of an excavator. Then, the homogeneous transformation matrices that relate two adjacent coordinate frames are given. The kinematic relations of the pose (position and orientation) of the bucket, the joint shaft angles, and the lengths of the cylinder rods in the hydraulic actuators for an excavator are studied. Explicit expressions for the forward and backward (inverse) kinematic relations are presented. Then, the corresponding kinematic velocity relations for the excavators are developed. The kinematic relations presented provide the f...

Takahashi H., Morikawa Y., Tateyama K., Fukagawa R.

In this study, an over-head-type load-haul-dump (LHD) with a vessel (Advanced LHD with a Vessel: ALV) is proposed to increase the carrying capacity. As the working environment is severe for workers, especially in underground mines, unmanned LHD task is desirable. In this case, the cabin for the operator is not necessary. Therefore, overhead loading into the vessel will be possible. In this paper, a concept of ALV is proposed, and kinematics and dynamics of ALV is described. Furthermore, the experimental results by using the ALV model are also described. In order to obtain the mobility of ALV, the wheels and the articulated steering system are adopted for moving and steering. Furthermore, in order to increase the carrying capacity, a vessel is installed on the rear body. It was confirmed through the experiments that the working efficiency of ALV is higher than that of traditional LHD.

Hemami A.

Xu G., Feng Z., Wang W., Ding H.

Khoroshavin S.A., Shestakov V.S., Saitov V.I.

The relevance of the paper is due to the need to improve the efficiency of mining excavators. The traditional scheme of a hydraulic excavator straight shovel is considered. Studies have shown that it is possible to increase the performance of an excavator by reducing the weight of working equipment and increasing the bucket capacity while retaining all the advantages of hydraulic excavators and without changing the initial weight of the entire machine, to reduce the weight of the developed scheme of working equipment with a cable-hydraulic drive. The transfer of hydraulic cylinders to the rotary platform of the excavator and the transfer from them of efforts through the cable system provided an exception to the bending moments on the boom and stick, which allows reducing the cross section of these elements and, accordingly, their mass. To expand the scope of hydraulic excavators, studies have been conducted on the creation of a control algorithm for the main mechanisms. Objective: To study the possibility of using a combined cable-hydraulic drive for mining excavators. Research methodology: mathematical modeling of the workflow. Results: A mathematical model, algorithm and program in algorithmic language have been developed for a career shovel with working equipment “direct shovel,” which allows determining the required graphs of the control law of the main drives for shaping the displacement speeds of the hydraulic cylinders ensuring the movement of the bucket along the desired trajectory.

Shestakov V., Babenkov P., Horoshavin S.

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.

Cao Y., Xie Y.

This paper presents a new mathematical model of 4 degrees of freedom of links to qualitatively describe the dynamic behavior of the front structure of an excavator. In the model, the effects of couple of forces as new additional effects are involved. The exact forms and solutions for position-varying moments of inertia used in this model are presented. A topologic structure is used for the kinematic analysis of the body frame. The numerical results show that the new additional effects can change the angular kinetic energy of all links to a significant degree when the upper structure swings. The results suggest that the new additional effects should be taken into account for analysis of excavator dynamics.

Gao Y., Huang W., Quan L., Lan Y., Huang J.

Hydraulic axial piston motor is one of the fundamental components in hydraulic systems; it is widely used in engineered machine, especially in high-power drive or reciprocating motion, such as hydraulic excavator. For hydraulic axial piston motor efficient planning, in addition designing and controlling are required for system operating safety and efficiency. Simulation delivers an advantage over analytical approaches and allows better understanding of the motor performance. For multi-piston hydraulic motor, one of the simulation methods, distributed parameter model, could analyze the detailed performance in each piston chamber. Therefore, in this study, we investigate the characteristics of hydraulic axial piston motor by setting up a distributed parameter model based on physical prototype, which includes mechanical–hydraulics coupling process. The effects of the dynamic pressure inside the piston chamber, the fluidic compressibility and other related parameters are considered in the coupling process. At the same time, the distributed parameter model of hydraulic axial piston motor was used in the simulation model of hydraulic excavator. The results indicate that in two-way hydraulic axial piston motor, the valve plane should adopt symmetrical structure, and silencing groove set should be put on both ends of the valve plane slots, which could reduce pressure ripple and overshoot in the piston chamber. Furthermore, the torque characteristics are highly affected by the clearance between the piston and the cylinder bore. Through this research, we may have a better understanding about the mechanism of output torque fluctuation in hydraulic axial piston motor, and the pressure ripple and overshoot in the piston chamber due to through-flow area discontinuity between the silencing groove and the ends of the valve plane slots. The model is verified using a nine-piston hydraulic motor in hydraulic excavator.

Pan Y., Hou L.

Earthmoving equipment in motor graders, which can be considered to be complex multibody systems (MBSs), are critical components for earthwork, compaction and re-handling. They have not yet received much attention due to their unusual applications and complicated structures. In this paper, a comprehensive study of an earthmoving MBS, from the mechanism identification and sensitivity analysis to the multi-objective optimization, is presented. First, the earthmoving MBS is identified to be a six degrees-of-freedom spatial hybrid mechanism, where a three revolute-revolute-prismatic-spherical (RRPS) and one spherical subchain (so, RRPS-S) spatial parallel mechanism is the key subsystem, through the mechanism analysis and synthesis. An earthmoving virtual prototyping model is built according to the system topology and connectivity. The kinematic simulations are carried out by imposing corresponding driving functions. Afterwards, the sensitivity analysis is introduced to extract several most relevant design variables from the global ones. A multi-objective optimization process is carried out to improve working performance, where fuzzy sets are used to define different objectives. Results show that the optimal earthmoving mechanism provides better lifting and parallel lifting capabilities.

Pan Y., Callejo A.

Earthmoving mechanisms in motor graders are critical components for earthwork, compaction and re-handling, and yet they have not received much attention by mechanical engineering research in recent times. In this paper, a comprehensive analysis, from mechanism identification and innovative design to kinematic analysis, is presented. First, the mechanism analysis and synthesis method based on multibody system dynamics is carried out through the analysis of the system topology and connectivity. We conclude that the earthmoving multibody system is a spatial hybrid mechanism, which consists of a spatial parallel mechanism and a spatial serial mechanism. Second, a number of new spatial parallel mechanisms, which are advantageous with respect to the original one under certain conditions, are generated. The kinematic characteristics of the parallel mechanism family are investigated in terms of constraint equations formulated in natural coordinates. Third and last, kinematic simulations and optimization processes are carried out to evaluate the advantages of the presented spatial parallel mechanisms. Simulation results show that these mechanisms can provide better kinematic performance.

Ding S., Ouyang X., Fan B., Yang H., Gong G.

The exoskeleton robot enhances the wearer's strength and plays an important role in various applications such as disaster relief, battlefield, rehabilitation, etc. The hydraulic system is often used to actuate the locomotion robotics for the advantages of high power-to-mass ratio, large force output, and so on. In this paper, the dynamic simulation of a hydraulic-driven exoskeleton robot is presented. Based on virtual prototyping, the controller and the parameters of the hydraulic system are determined and verified by modeling the driven system in AMESim, while the robot dynamic behavior is analyzed by building the robot dynamic model in ADAMS. The model of the prime mover, an IC engine, is simplified to reflect its torque-speed property rather than the complicated physical and chemical changes in the combustion cycle. In the simulation, the controller is determined first by employing a sufficient constant flow source to replace the engine model and the pump. Then the parameters of the hydraulic system are verified based on the determined controller. Lastly, the dynamic behavior of the exoskeleton robot is predicted by tracking the input reference from the Clinical Gait Analysis (CGA) data. The simulation results indicate that the designed exoskeleton robot can achieve expected working conditions. Experiments are set up on the exoskeleton robot prototype to validate the virtual prototype. The agreement of the results from simulation and experiments confirms that the virtual prototype predicts the dynamic behavior of the exoskeleton robot reliably.

Frimpong S., Thiruvengadam M.

Large capacity shovels are deployed in surface mining operations for achieving economic bulk production targets. These shovels use crawler tracks for effective terrain engagement in these environments. Shovel reliability, maintainability, availability and efficiency depend on the service life of the crawler tracks. In rugged and challenging terrains, crawler wear, tear, cracks and failure are extensive resulting in prolonged downtimes with severe economic implications. In particular, crawler shoe wear, tear, cracks and fatigue failures can be expensive in terms of maintenance costs and production losses. No fundamental research has been undertaken to understand the crawler-formation interactions in challenging and rugged terrains in surface mining operations. This study forms the foundations for providing long-term solutions to crawler failure problems. The kinematic equations governing the crawler-formation interactions have been formulated to characterise the crawler motions during shovel production. Th...

Huang J., Dong Z., Quan L., Jin Z., Lan Y., Wang Y.

Complexity of large structure of hydraulic shovel system drives the guideline development for designing a swing unit of the shovel. Some of the issues are how to achieve smooth swing motion, save energy, and easily adjust its swing velocity. In this paper, we proposed a dual-closed-hydraulic-circuit (DCHC) accordingly to meet the design requirement. In the DCHC system, instead of manual adjustment, the displacement of hydraulic axial piston pump is controlled by programmed software algorithm through electronic control device, which significantly simplifies the current circuit design. The DCHC system also enables controllable recuperation of kinetic energy of swing motion for use by other actuators. Accordingly, the new system will achieve smoother motion compared with existing system and more efficient operation. We demonstrate the advantages of our DCHC design through simulation and verify through developing a hydraulic shovel prototype with bucket capacity of 15 cubic meters and operational weight of 270 tons. Both simulation and experimental results indicate that the DCHC system is feasible and works as intended.

Chen J., Qing F., Pang X.

In order to solve the problem that hydraulic excavator in the real working process cannot meet the design requirements and reveals insufficient digging force, a new method on mechanism optimal design of backhoe hydraulic excavator working device based on digging paths is introduced and discussed in this paper. Considering the characteristics of consecutive digging process of hydraulic excavator, a digging path is composed of bucket digging trajectories and arm digging trajectories. The feasible working region is divided into a series of uniform paths according to the working position of boom. The practical digging performance of excavator is evaluated based on the digging force parameters under combined work condition of the discrete points on the digging paths. It is turned out that the method is more accurate to analyze excavator’s real-world digging performance via the analysis of some practical cases. Based on the new digging performance analysis method, the optimization mathematical model is built to ensure the digging force under combined work condition and the average digging force of every operating path as big as possible. The layout design of hinge position on the working device is optimized through genetic algorithm. The optimization result shows that a certain model of an excavator’s maximum digging force on the customary digging paths is improved by 10% and the average digging force is improved by 4% after the optimization on the working device of the excavator with weak digging force.

Wubneh A., Au C.K., Ma Y.-.

This chapter proposes a method for feature synthesis of mechanisms and manipulators from user specifications based on a hybrid approach employing both neural network and optimization techniques. The typical mechanism design modeling problem with the lack of solution convergence observed in optimization is addressed by using a neural network method to generate reliable initial solutions. This chapter also discusses a module by which the validation of prescribed precision configuration points is evaluated.

Liu J.X., Li S.J., Peng J.T., Liu J.M.

Vertical clamps are representative large-capacity metallurgical lifting tool and wide spread employed to lift and to convey vertical cold or hot rolling steel coil of strip. To ensure absolute safety, the kinematics model of the vertical clamp was built, and its virtual prototype was established on Solid Edge, and the working process was simulated based on ADAMS environment. To explain the establishing mode of clamping force, the dynamic positive feedback working process of clamping was discussed. The correctness of simulation was validated by means of analytical investigation. The safe working conditions of vertical clamp were obtained.