Intelligent Cable Shovel Excavation Modeling and Simulation

Cable shovel excavators are used for primary production of geomaterials in many surface mining operations. A major problem in excavation is the variability of material diggability, resulting in varying mechanical energy input and stress loading of shovel dipper-and-tooth assembly across the working bench. This variability impacts the shovel dipper and tooth assembly in hard formations. In addition, the geometrical constraints within the working environment impose production limitations resulting in low production efficiency and high operating costs. An intelligent shovel excavation (ISE) technology has been proposed as a potential solution to these problems. This paper addresses the requirements of the dynamic models of the cable shovel underlying the ISE technology. The dynamic equations are developed using the Newton–Euler techniques. These models are validated with real-world data and simulated in a virtual prototype environment. The results provide the path trajectories, dynamic velocity and acceleration profiles, and dimensioned parameters for optimum feed force, torques and momentum of shovel boom-dipper assembly for efficient excavation. The optimum digging forces and resistances for the cable shovel excavators are modeled and used to predict optimum excavation performance.     

Case Study: Planar Kinematics of Dragline for Efficient Machine Control

Overburden excavation is an integral component of the surface mine production chain. In large mines, the walking dragline is a dominant strip mining machine. Dragline performance depends on the operating speed, the bucket payload, and the machine availability, which could be negatively impacted by the actions taken to increase the machine productivity. In this study, the writers develop the kinematics and dynamic modeling of a dragline front-end assembly using the vector loop and simultaneous constraint methods. Based on the results of the kinematics and dynamic simulations, stress modeling and analysis are performed. Detailed analysis of the simulation results show that the angular accelerations of the drag and hoist ropes are close to zero, which indicate very smooth simulated operations. The respective maximum drag and hoist forces are 100 and 75?kN, which also indicate a dominant drag operation. The maximum stress loading of the boom’s Arm-1 (166.5?MPa) and Arm-2 (159.9?MPa) are less than the boom yield stress at 305?MPa. These results indicate machine health and longevity within the simulated conditions.     

Constructing Hydraulic Robot Models Using Memory-Based Learning

Hydraulic machines used in mining and excavation applications are nonlinear systems. Apart from the nonlinearity due to the dynamic coupling between the different links there are significant actuator nonlinearities due to the inherent properties of the hydraulic system. Optimal motion planning for these machines, i.e., planning motions that optimize a user-selectable combination of criteria such as time, energy, etc., would help the designers of such machines, besides aiding the development of more productive robotic machines. Optimal motion planning in turn requires fast (computationally efficient) machine models in order to be practically usable. This work proposes a method for constructing hydraulic machine models using memory-based learning. We demonstrate the approach by constructing a machine model of a 25-ton hydraulic excavator with a 10 m maximum reach. The learning method is used to construct the hydraulic actuator model and is used in conjunction with a linkage dynamic model to construct a complete excavator model that is much faster than an analytical model. Our test results show an average bucket tip position prediction error of 1 m over 50 sec of machine operation. This is better than any comparable speed model reported in the literature. The results also show that the approach effectively captures the interactions between the different hydraulic actuators. The excavator model is used in a time-optimal motion planning scheme. We demonstrate the optimization results on a real excavator testbed to underscore the effectiveness of the model for optimal motion computation.     

Shoulder joint kinetics during the push phase of wheelchair propulsion

The purpose of this investigation was to quantify the forces and moments at the shoulder joint during free, level wheelchair propulsion and to document changes imposed by increased speed, inclined terrain, and 15 minutes of continuous propulsion. Data were collected using a six-camera VICON motion analysis system, a strain gauge instrumented wheel, and a wheelchair ergometer. Seventeen men with low level paraplegia participated in this study. Shoulder joint forces and moments were calculated using a three-dimensional model applying the inverse dynamics approach. During free propulsion, peak shoulder joint forces were in the posterior (46 N) and superior directions (14 N), producing a peak resultant force of 51 N at an angle of 185 degrees (180 degrees = posterior). Peak shoulder joint moments were greatest in extension (14 Newton-meters [Nm]), followed by abduction (10 Nm), and internal rotation (6 Nm). With fast and inclined propulsion, peak vertical force increased by greater than 360%, and the increase in posterior force and shoulder moments ranged from 107% to 167%. At the end of 15 minutes of continuous free propulsion, there were no significant changes compared with short duration free propulsion. The increased joint loads documented during fast and inclined propulsion could lead to compression of subacromial structures against the overlying acromion.     

Hydraulic Joint for Pipe Jacking

A newly developed hydraulic joint for pipe jacking is described and compared with conventional compression rings. It is shown that with the hydraulic joint, thrust eccentricities are largely reduced, resulting in a much more uniform stress profile at the pipe ends and hence a considerably reduced pipe damage potential. Higher jacking forces can be applied (fewer or no intermediate jacking stations are necessary), longer pipes can be used (fewer joints are necessary), smaller radii of curvature are feasible (fewer or no intermediate jacking pits are necessary) and frictional forces are reduced. The measurement of joint displacements and joint liquid pressures permits an effective real-time monitoring of the jacking process. 30 of the 40 pipelines with a total length of 8.2?km completed so far had curved alignments. The smallest radius of curvature was 86?m using 3?m long pipes with an internal diameter of 1.2?m. Practical experiences gained with the hydraulic joint are summarized.     

4m3电铲常见故障原因、诊断方法、维护操作

目前国内大型露天矿山的铲装设备主要是电铲.由于其作业环境恶劣,工作机构极易发生故障.因此,探讨电铲常见故障原因、诊断方法、维护操作对提高电铲作业效率有着极为重要的意义.     

The effect of intersegmental knee moments on patellofemoral contact mechanics in cycling

The aim of this study was to evaluate the effect of bicycle pedal design on the mechanics of the patellofemoral joint. Previous research determined that for certain riders the non-driving varus and internal knee moments could be reduced by switching from fixed to free floating pedals (Ruby and Hull, 1993). It was postulated that the presence of varus and internal knee moments during fixed pedal cycling may adversely affect patellofemoral joint contact mechanics which could lead to the development of anterior knee pain. To investigate the effect of pedal design the hypothesis that varus and internal intersegmental knee moments significantly increase patellofemoral contact pressure, contact area and contact force was tested. To test this hypothesis cycling loads were simulated in vitro using a six-degree-of-freedom load application system (LAS). Using the LAS, varus moments ranging from 0-20 Nm and internal knee moments ranging from 0-10 Nm were applied simultaneously with quadriceps force at knee flexion angles of 60 and 90 degrees. Patellofemoral contact patterns were measured using pressure sensitive film. An applied 10 Nm internal moment significantly increased both contact area by 16% and contact force by 22% at 90 of flexion. The application of a 20 Nm varus moment modestly yet significantly increased contact area by 6% and contact force by 5%. When applied in combination, varus and internal knee moments increased contact area and force by as much as 29% and 28% respectively. The mean contact pressure was not significantly increased by either of the two moments. The results suggest that non-driving intersegmental knee moments subject the patellofemoral joint to loads and contact patterns which may accelerate the development of chondromalacia.     

Aliphatic and alicyclic diols induce melanogenesis in cultured cells and guinea pig skin

The forces and moments in the shaft of a distal femoral replacement were measured by telemetry for a subject during different activities, and calculations were then made of the forces at the knee. The axial force showed a small peak at heel-strike followed by two main peaks during stance. In level walking, the peak axial force was between 1,487 and 1,718 N (2.2-2.5 BW), the peak shear force was 269-368 N (0.4-0.54 BW) directed anteriorly on the tibia, the peak axial torque was 7 Nm internal, while the patellofemoral force was 466-571 N. The highest axial force was recorded for descending stairs (2.8 BW). Standing on one leg produced 2.4 BW, while lying supine and raising the leg produced 1.7 BW. The data produced may resemble that of a normal subject, and has application to basic joint mechanics, to joint reconstruction, and to total knee replacement design and evaluation.     

Limitations of quasi-static estimation of human joint loading during locomotion

The forces and moments at the ankle, knee and hip joints of the human lower limbs are divided into static and inertial components. They are calculated for various activities ranging from slow walking to running. The relative roles of these two components in the 'total' joint loads are studied, and the limitations of using a quasi-static analysis approach for joint load approximation are discussed. The results indicate that the static loads only reflect the gravitational and external reactions between the body and the environment, whereas the inertial loads provide dynamic information on each body segment involved. The effect of the inertial forces and moments becomes more important as the speed of locomotion increases; where the more proximal joints in the human lower extremity are concerned; and where the shear components of the force and moment are of interest. On the other hand, it seems that most of the joint moments in the lower extremity during walking and even running could reasonably be approximated by static components.     

Using Hue, Saturation, and Value Color Space for Hydraulic Excavator Idle Time Analysis

Accurate analyses of equipment idle time are crucial for the efficient utilization of construction equipment in large construction projects. The less idle time the equipment has, the higher productivity it can achieve. However, it is not feasible for field personnel to visually observe the operation of construction equipment all day. An image processing-based methodology is presented in this paper to automatically quantify the idle time of hydraulic excavators. The image color space (hue, saturation, and value), which shows significant advantages over the red, green, and blue color space in identifying and tracing hydraulic excavators, is used as the base for image segmentation and tracing algorithms. The changing centroid coordinates of an excavator in successive images taken at constant time intervals are used as indicators of movement. Experimental results show that the presented methodology has a promising application potential for effective equipment management in construction projects.     

Loads on Braced Excavations in Soft Clay

A parametric finite element study has been carried out to demonstrate the importance of clay strength and depth of clay layer on the earth pressures, strut loads, and bending moments for a strutted sheet pile wall in soft, essentially normally consolidated clay. The clay is modeled as nonlinear and anisotropic. The modeled excavation is 10?m deep. For a shear strength profile giving a close to failure condition the maximum bending moment is found to be 6 times larger than for a clay profile with 40% higher strength, and the maximum strut loads are up to twice as large. The maximum strut loads are significantly higher than those given by existing empirical design rules. Comparative analyses with an isotropic linear elastic–plastic soil model show relatively small differences in moments and strut loads. Comparisons against analyses with a beam-on-spring type finite element model show significant differences to the continuum FEM analyses. The main reason is that beam-on-spring models cannot capture the significant effect of arching on earth pressures, strut loads and bending moments.     

Three-Dimensional Responses Observed in an Internally Braced Excavation in Soft Clay

Several three-dimensional effects were observed in the performance monitoring data collected during excavation for the Ford Engineering Design Center in Evanston, Illinois. The elevations of the soil around the excavation varied and the excavator removed the soil in a nonuniform excavation process, both of which contributed to the observed three-dimensional (3D) effects. This paper describes the excavation support system and subsurface conditions at the site, summarizes the construction procedures, and presents the lateral soil movements measured by inclinometers, ground-surface movements measured by an automated total station, tilt of components of an adjacent structure, and forces in internal braces. These responses are compared with expected responses from current design methods. The 3D nature of the excavation resulted in smaller movements on the side of the excavation, where the retained soil was lowest, an unexpected pattern of axial strut loads and very slight damage to an exterior wall that paralleled one of the excavation walls.     

Influence of resistive forces on grain boundary motion

Abstract

Velocity of a grain boundary is determined by a balance between the driving force and the sum of all resistive forces acting on the boundary. In addition to the intrinsic resistive (drag) force, at least four unique extrinsic resistive forces can be identified: a surface pinning force, a surface drag force, an impurity pinning force, and an impurity drag force. Although the impurity drag force has been analyzed extensively, similar attention to other resistive forces thus far has been neglected. It is the purpose of this communication to describe the aforementioned resistive forces and indicate how their presence leads to a dynamic model for grain boundary motion involving both grain boundary pinning and drag. It is suggested that motion is effected by formation of impurity clusters at the boundary, thus permitting breakaway to proceed more easily. Accordingly, resultant properties are affected not only by final grain boundary configuration but also by kinetics of cluster dissolution in the wake of the moving boundary.

Résumé

La vitesse de migration d'un joint de grain est déterminée par l'équilibre qui s'ètablit entre la force motrice et la somme de to utes les forces résistives agissant sur le joint. En plus de la force résistive intrinséque (trainage), au moins quatre autres forces extrinsèques peuvent être identifiées: une force d'épinglage de surface, une force de trainage de surface, une force d'épinglage par les impuretés et une force de traînage due aux impuretés. Alors que cette dernière a été étudiée de façon intensive les autres forces ont été jusqu'a présent négligées. Le but de cette communication est de décrire les forces ci-dessus mentionnées et d'indiquer comment leur présence conduit à un modèle dynamique de la migration des joints incluant le traînage et l'épinglage du joint. L'auteur suggère que la migration est influencée par la formation d'amas d'impuretes au joint, ce qui permet un désépinglage plus aisé. Il s'ensuit que les propriétés de la migration ne sont pas seulement affectées par la configuration finale du joint de grain, mais aussi par la cinétique de dissolution des amas dans le sillage du joint migrant.     

混合动力液压挖掘机节能液压系统仿真分析

根据液压挖掘机的工况和混合动力技术的特点,提出了适合混合动力液压挖掘机的节能液压系统。为了证明节能液压系统的可靠性,以22t液压挖掘机为对象,用MATLAB软件进行了仿真。仿真结果表明,与采用开式节流控制系统的混合动力液压挖掘机相比,采用闭式节能液压系统的混合动力液压挖掘机的平均功率能减小到一半以下。从而发动机装机功率和油耗得到明显的改善。     

同步顶升液压系统设计及动态特性分析

In this paper, according to the characteristics of large load and uneven distribution of upper wall, large jacking height and high requirements for synchronous jacking precision in the separation process of the upper and lower wall of WK-35 electric excavator,a large-scale mining equipment in the mine, a hydraulic synchronous jacking method with four-point uneven load is proposed, which combines with the fuzzy PID control method which is suitable for nonlinear and time-varying complex system control to realize the synchronous jacking of excavator. Based on the synchronous jacking hydraulic system of WK-35 electric excavator, a simulation model of AMESim hydraulic system is built for dynamic simulation. The analysis results show that the changes of different loads only affected the piston velocity or oil velocity of the hydraulic cylinder in the final stable state. Both the balance control valve and the throttle speed control valve can quickly reach the stable state within 0~1s, which is conducive to better response performance when the hydraulic system enters the steady state.     

露天矿电铲铲装移动轨迹规划研究

自主铲装技术是未来露天矿智能开采的核心环节之一.为提高电铲在自主铲装过程中的工作效率,提出了一种电铲铲装移动路线的优化方法.在已知电铲工作区域的基础上,基于贪婪算法规划出电铲移动次数最少的作业位置集;在给定起始挖掘点的基础上,使用遗传算法生成电铲铲装移动最短路径,并规划每个位置对应的挖掘区域;最后结合电铲作业的相关几何...     

Dynamic Modeling of Storm Surge and Inland Flooding in a Texas Coastal Floodplain

The purpose of this study is to analyze the combined effects of storm surge and inland rainfall on the floodplain of a coastal bayou in the Houston area by using dynamic hydraulic modeling. Most existing floodplains in the Houston area are defined using only rainfall as an input into steady-state hydraulic models and do not consider the impact of hurricane-induced storm surge on the floodplain. HEC-RAS, a one-dimensional flow model, was run for both steady- and unsteady-states to analyze the additional effect storm surge has on the coastal floodplain. Storm surge and rainfall data from Hurricane Ike were utilized to run an unsteady hydraulic model on Horsepen Bayou near Galveston Bay. The dynamic model generated a good match between the modeled hydrograph and measured data in the watershed. Additionally, a timing sensitivity analysis was completed by shifting the timing of the storm surge both earlier and later in time. The dynamic model revealed that the timing of both rainfall and storm surge play a significant role in the magnitude of inland flooding.     

3D Surface Modeling and Measuring System for Pneumatic Caisson

In order to build a 3D model environment of a pneumatic caisson for excavator operators and managers, a modeling and measuring 3D surface system of unmanned pneumatic caisson was presented in this paper. The whole system is based on two 3D laser scanners for the pneumatic caisson by acquiring the surface data of pneumatic caisson and successive data processing for surface reconstruction and measurement. Registration and reconstruction are also discussed in this paper. In order to convert two point sets into one common coordinate, Hough transforms were used to extract planes and then by using their parameters to register the two point sets. As for surface reconstruction using triangular meshing, a new method based on curves was presented. When combined with the real-time pose and location of the excavators, the 3D environment can be used as a “virtual reality” operating environment for excavation operators. The whole system has been applied in a pneumatic caisson of an underground project in a Shanghai subway, which proved to be working well, with less than 16-s work cycle (period of a single 180° 3D laser scan), at an estimated resolution of less than 20 mm.     

Forces in Wingwalls of Skewed Semi-Integral Bridges

In theory, semi-integral bridges with skewed approaches have a tendency to rotate toward the acute corners due to thermal expansion. This movement causes force to be transferred into the wingwalls that are often designed only as retaining walls. The wingwall/diaphragm joint of two semi-integral bridges were instrumented and monitored in the state of Ohio. Information pertaining to the thermal expansion was successfully compiled during the extent of this research and showed wingwalls’ forces can reach magnitudes of 159?kN (35.7?kip). The maximum longitudinal movement measured 16.36?mm (0.6442?in.) and the maximum movement into the wingwall measured as 3.289?mm (0.1295?in.). The effects of skew and span on the wingwall forces were also modeled and presented.     

Para-spinal regional anesthesia and prevention of thromboembolism/anticoagulation. Recommendations of the German Society of Anesthesiology and Intensive Care Medicine, October 1997

OBJECTIVE: To evaluate clinical and biomechanical consequences of desmotomy of the accessory ligament (AL) of the deep digital flexor tendon (DDFT) of equine forelimbs and determine whether this procedure is a viable treatment for chronic desmitis of the AL-DDFT. ANIMALS: 6 adult Standardbred trotters. PROCEDURE: Biomechanical recordings obtained before and 6 months after desmotomy were compared. Walk and trot joint angles, ground reaction forces, peak joint moments, and tendon forces were assessed. RESULTS: Within 10 days after surgery, all horses were sound at a trot. Swelling, increased carpal flexion in the terminal stance phase, and incidental stumbling at the beginning of exercise were observed. Flexion angle in the carpal joints was significantly increased at the end of the stance phase. Peak moments around the distal interphalangeal joint and forces in the DDFT and AL-DDFT were decreased. Metacarpophalangeal joint angles, peak metacarpophalangeal joint moments, and peak loading of the suspensory ligament and the superficial digital flexor tendon were unchanged. CONCLUSION: 6 months after desmotomy, AL-DDFT strain was reduced without causing changes in joint angles or increasing tendon loads or joint moments that could be considered hazardous for the horses. CLINICAL RELEVANCE: Changes in locomotion that remained 6 months after AL-DDFT desmotomy would be acceptable for horses with chronic desmitis if conservative treatment failed.