Material grade-based task planning for robotic limestone mining

Authors have been conducting research on an unmanned loading system by wheel loader. The system has function of sensing, decision making and control of motion. The operation of the system is autonomous completely without any assist of human operator. As a part of the research, the detection method of location and shape of the pile will be described in this paper. At the beginning of the loading operation, scooping positions should be decided based on the location and shape of the pile. Stereo vision system with two CCD cameras is attached on the loader. For obtaining three dimensional data of the shape of the pile, a correlation method is applied on the images. The 3D data is converted into the column model by quantization. The scooping positions are decided based on the data of the pile and the location and direction of the dump truck for effective operation at the beginning state of the operation. Because the shape of the pile is changed by scooping with advancing the loading operation, the measured shape has to be updated during operation. After several scooping, the images of the pile are captured during travelling between the scooping position and the loading position. It is not necessary to slow down of velocity of the loader up to 8km/h for capturing. 3D shape and column model of the pile is obtained in the same manner. The proposed method is applied on the experimental system for autonomous loading operation and shows good results in the test field trial.

There is a demand of mining automation by heavy equipment in an open mine. Authors aim to automization of motion for wheel loader in scooping and loading operation. In this paper, we applied the optimization method by Genetic Algorithm to the path planning for the wheel loader on scooping and loading operation. We showed the quasi-optimized path and demonstrated by the miniature wheel loader robot.

Estimation of ore grade is very important for the value evaluation of ore deposits, and it directly affects the development of mineral resources. To improve the accuracy of the inverse distance weighting (IDW) method in ore grade estimation and reduce the smoothing effect of the IDW method in grade estimation, the weight calculation method involved in the IDW method was improved. The length parameter of the ore sample was used to calculate the weight of the IDW method. The length of the ore samples was used as a new factor of the weighting calculation. A new method of IDW integrated with sample length weighting (IDWW) was proposed. The grade estimation of Li, Al, and Fe in porcelain clay ore was used as a case study. A comparative protocol for grade estimation via the IDWW method was designed and implemented. The number of samples involved in the estimation, sample combination, sample grade distribution, and other factors affecting the grade estimation were considered in the experimental scheme. The grade estimation results of the IDWW and the IDW methods were used for comparative analysis of grades of the original and combined samples. The estimated results of the IDWW method were also compared with those of the IDW method. The deviation analysis of the estimated grade mainly included the minimum, maximum, mean, and coefficient of variation of the ore grade. The estimation effect of IDWW method was verified. The minimum deviations of the estimated grade of Li, Al, and Fe were between 9.129% and 59.554%. The maximum deviations were between 4.210 and 22.375%. The mean deviations were between − 1.068 and 7.187%. The deviations in the coefficient of variation were between 3.076 and 36.186%. The deviations in the maximum, minimum, mean, and coefficients of variation of the IDWW were consistent with those of the IDW, demonstrating the accuracy and stability of the IDWW method. The more the samples involved in the estimation, the greater the estimation deviations of IDW and IDWW methods. The estimated deviations of Li, Al, and Fe were affected by the shape of the grade distribution, when the same estimation parameters were used. The grade distribution pattern of the samples significantly influenced the grade estimation results. The IDWW method offers significant theoretical advantages and addresses the adverse effects of uneven sample lengths on the estimates. The IDWW method can effectively reduce the smoothing effect and improves the utilization efficiency of the original samples.

A wheel loader is one of the major loading machine in surface mines. This paper describes the path planning which is a part of the research on automatic loading operation by a wheel loader. At loading operation, loader moves on V-shape path from scooping point to dumping point. A wheel loader has the articulated structure and steering is controlled by change of articulate angle. The path planning method for V-shape is proposed.Major contents of this paper are as follows;1) Kinematics of the articulate steering mechanism is analyzed. The relation between the steering angle and the curvature of path is almost liner.(2) V-shape can be composed of two straight lines and the turn path which is a combination of four pseudo clothoid paths. For given position and direction of loader at scooping point and dumping point, length of the straight lines and the shape of turn path are determined by the proposed method. Example of V-shape generation for piled ore model is shown.(3) For tracking control, the proposed control system includes the reference values generator. In path planning, control values are represented by function of moving distance. During tracking control, the reference values at each time are generated based on measured moving distance, and issued to the controller.

Authors have been engaged in the research on the outdoor working robotics, and targeting the autonomous pile loading operation by a wheel loader in mining particularly. Authors developed a real sized autonomous wheel loader "Yamazumi-4," and succeeded the unmanned autonomous pile loading operation experimentally. The precise traveling control is necessary to repeat loading operations. The real sized construction machines like the wheel loader are difficult to control the travelling speed precisely. Authors adopted the path planning and path following control based on the odometer and succeeded to gain precise geometric shape of the path. This paper describes the path planning and path flowing control of the autonomous wheel loader.

The authors have been conducting research on an autonomous system for loading operation by wheel loader. Experimental results at a field test site using full-size model (length: 6.1m) will be described in this paper. Basic structure of system consists of three sub systems: measuring and modeling of environment, task planning and motion control. The experimental operation includes four cycles of scooping and loading to dump truck. The experimental results prove that the developed system performed the autonomous operation smoothly and completed the mission.

In this paper, as a part of research work on the autonomous loading operation by wheel loader at surface mines or construction working places, a method of path generation for wheel loader will be described. V shape path connecting between the scooping position and the loading position consists of clothoid curves and straight lines. Each length of line segments are optimized in path generation procedure. The scooping direction is determined based on the estimation of resistance force applied on the bucket during scooping motion, by using simplified shape model of pile and bucket trajectory model. Proposed method is installed on the experimental model. Shape of the pile is measured by a stereo-vision system. For giving scooping position, scooping direction giving the least moment on the bucket is selected. By this method, appropriate path is generated.

Summary. A control system for crude loading to tankers at the Statfjord field has been designed to allow tanker loading to take place at all times to prevent production shutdowns caused by loading-buoy problems. This paper discusses how the control system was designed to maximize the flexibility of loading operations and to meet all safety and regulatory requirements. The experience gained from more than 4 years of operation of the system is reviewed. The system has allowed maximum use of total field crude storage capacity while loading to 125,000-DWT [127 000-Mg] tankers nearly every day throughout the year. It has been possible to maintain a high production rate even through the periods of difficult weather conditions experienced in the northern North Sea. Introduction The Statfjord Platforms A, B, and C are located in the Norwegian Sector of the northern North Sea. The platforms are of the gravity-base type with total crude storage capacity of 5 million bbl [795 000 m3]. The current total crude production rate is on the order of 720,000 BOPD [114 000 m3/d oil]. The crude production and storage capacities are different on each platform. Statfjord A has the highest production level at approximately 300,000 BOPD [47 700 m3/d oil], but the storage capacity is only 1.2 million bbl [191 000 m3]. Statfjord B and C have production levels greater than 200,000 BOPD [31 800 m3/d oil] and storage capacities of 1.9 million bbl [302 000 m3]. The crude is exported by 125,000-DWT [127 000-Mg] shuttle tankers, each tanker capacity being about 800,000 bbl [127 000 m3]. This means that one tanker loading is required nearly every day to avoid production shutdown. During loading operations, the tankers are moored to a single-point mooring (SPM). Each loading operation takes 16 to 20 hours. Currently, two SPM's are installed: one at Platform B and the other at Platform C. A third loading buoy, at Platform A, was removed from service in 1984 and replaced by a new subsea loading system, the offshore loading system (OLS). To maintain production and to optimize storage capacity, 36-in. [91-cm] crude tie lines were installed between Statfjord B and C SPM's and the Statfjord Platform A, as shown in Fig. 1 (see the Appendix for explanation of terms). This has enabled the field to be operated with only the two SPM'S. Initially, an operational procedure was considered that used physical sectioning of the tie lines with blind flanges to achieve different loading modes. It was realized, however, that such operations would be time-consuming and would present safety hazards resulting in delays to crude export with a subsequent reduction in production. As an alternative to this physical sectioning, a telemetry and control system was designed. This system was commissioned on Statfjord A and B in Nov. 1982, just before production startup on Statfjord B. At that time, three tankers were in operation for crude export from Statfjord A. The changeover to the new control system from the previous concept used when Statfjord A was the only platform in the field took place between two crude loadings without causing any delay in the loading schedule. This paper describes the design and operation of the telemetry and control system and summarizes the operational experience gained over the last 5 years. Objectives of the Control System Two major objectives were identified for the interplatform crude-loading control system. The first was to assist control-room operators in completing all preparations required for loading operations. This implies that upon completion of loading-mode selection, valve operations, radio initialization, and mooring operations, a "ready-to-start" signal was to be sent to the crude-pump-protection logic to enable manual start of the pumps. The second objective was to ensure automatic crude-pump shutdown in case of an emergency outside the platform itself. Specifically, the tanker must be able to stop the pumps under all circumstances, regardless of loading mode selected, and no failure in the control system must prevent this emergency action from taking place when required. Additionally, the following design requirements were established.1. To obtain maximum flexibility of loading operations. This is a requirement that any platform shall be able to use any of the loading buoys for crude export. Additionally, all platforms must, if required, be able to export crude simultaneously. Finally, crude transfer between platforms must be possible to maximize crude storage capacity whenever tanker loading is impossible as a result of bad weather. This is particularly important for Statfjord A because of the high production rate and low storage capacity. As a consequence of this requirement, an emergency stop from a tanker should involve only that particular loading operation, not simultaneous loading operations to other tankers. On the other hand, the actual crude pumps to be stopped by a tanker, e.g., at the Statfjord C loading buoy, would vary from time to time, depending on the loading mode selected. Finally, predefined emergencies on the loading buoys, as well as on all platforms involved in the loading operation, should lead to automatic shutdown of crude pumps, again depending on the loading mode selected.2. To obtain maximum availability of the system. The important requirement here was that no failure in the control system itself should ever prevent or abort any loading operation. To meet this requirement, all shutdown circuitry was duplicated, high-quality components were used throughout the system, and manual over-rides with key switches were provided on signals where duplication of circuitry was not viable. The crude tie lines and the control system ensure that crude can be exported from any platform, regardless of maintenance activities on a particular loading buoy.3. To comply with regulations. The fiscal metering of the exported crude should take place at the source platform, and all crude that is metered must go to the assigned receiver. Accordingly, pumping from one platform to more than one tanker simultaneously is not permitted. JPT P. 453^

ABSTRACTA method has been developed to estimate the environmental impact of wheel loaders used in earthmoving operations. The impact is evaluated in terms of energy use and emissions of air pollutants (CO2, CO, NOx, CH4, VOC, and PM) based on the fuel consumption per cubic meter of hauled material. In addition, the effects of selected operational factors on emissions during earthmoving activities were investigated to provide better guidance for practitioners during the early planning stage of construction projects. The relationships between six independent parameters relating to wheel loaders and jobsite conditions (namely loader utilization rates, loading time, bucket payload, horsepower, load factor, and server capacity) were analyzed using artificial neural networks, machine performance data from manufacturer’s handbooks, and discrete event simulations of selected earthmoving scenarios. A sensitivity analysis showed that the load factor is the largest contributor to air pollutant emissions, and that the best way to minimize environmental impact is to maximize the wheel loaders’ effective utilization rates. The new method will enable planners and contractors to accurately assess the environmental impact of wheel loaders and/or hauling activities during earthmoving operations in the early stages of construction projects.Implications: There is an urgent need for effective ways of benchmarking and mitigating emissions due to construction operations, and particularly those due to construction equipment, during the pre-construction phase of construction projects. Artificial Neural Networks (ANN) are shown to be powerful tools for analyzing the complex relationships that determine the environmental impact of construction operations and for developing simple models that can be used in the early stages of project planning to select machine configurations and work plans that minimize emissions and energy consumption. Using such a model, it is shown that the fuel consumption and emissions of wheel loaders are primarily determined by their engine load, utilization rate, and bucket payload. Moreover, project planners can minimize the environmental impact of wheel loader operations by selecting work plans and equipment configurations that minimize wheel loaders’ idle time and avoid bucket payloads that exceed the upper limits specified by the equipment manufacturer.

Stress distributions in human teeth modeled with a natural graded material distribution

Wheel loader optimal transients in the short loading cycle

Grade estimation is very important in designing open pits. In the process of grade estimation, underestimation can result in loss of economic ore, whereas overestimation would unnecessarily increase stripping ratio. Normally, kriging method, which suffers from underestimation and/or overestimation due to smoothing effect, is used for grade estimation. To overcome drawbacks of the kriging method, more efficient techniques such as conditional simulation can be applied. In this paper, utilizing sequential Gaussian conditional simulation, grade models were constructed for Sungun copper deposit situated in the North West of Iran. According to the obtained results, it was observed that conditional simulation can effectively cope with the weakness of kriging method. Also, it was observed that as compared to the kriging method, grade distribution, resulted from the conditional simulation, is almost identical to that of the real exploration data. Accordingly, using conditional simulation, the amount of mineable ore was significantly increased, and also, average net present value as the mines’ most important economic indicator was improved by 40%.

Our group developed a method for planning of scooping point and approach path as a part of our ongoing research on autonomous loading operation of wheel loader at construction sites. The planning of scooping position and direction is obtained through processing pile model. The pile model represents shape and volume of the pile, changes of shape and volume by scooping, and falling behavior accompanied scooping. Scooping direction should be perpendicular to slope of the pile to avoid unbalance of resistance force around the center line of the bucket. The resistance force imposed on the bucket is estimated using the pile model and bucket trajectory model. The scooping direction with least unbalance of resistance force is selected. V shape path between the scooping position and the loading position to dump track is composed of straight lines and clothoid curves. For given scooping position and loading position, the path with the least length is produced by the proposed planning method using optimization by Lagrange multiplier. For selection of the next scooping point, V shape paths for candidate of scooping points are planned by proposed method.

A method of making desired rock sediment shapes on a truck bed is developed by designing target motion trajectories of a wheel loader bucket. The behavior of the rocks in the bucket and on the truck bed in loading operation is analyzed by camera images and simulations. By combining both behavior models obtained by the analyses, an algorithm of designing the bucket motion to make desired rock sediment shapes is proposed, and its effectiveness is verified by fundamental experiments.

Wheel loader ride comfort is a critical factor affecting operator safety, productivity, and long-term health. This study systematically investigates the influence of different operating load conditions using a half-vehicle dynamic model. The ride comfort is evaluated based on the root mean square (r.m.s) values of acceleration responses of the vertical driver's seat (aws) and pitch angles of cab (awc), in accordance with ISO 2631:1997(E) standards. The simulation results demonstrate that variations in operating loads significantly affect ride comfort when the machine operates under an ISO class D road surface at a speed of 10 km/h. These findings provide a theoretical basis for optimizing the load configuration of wheel loaders to ensure acceptable ride comfort during operation.