Optimal bucking hardwood species in Central Appalachia

An optimal tree-stem bucking system was developed for central Appalachian hardwood species using 3D modeling techniques. ActiveX Data Objects were implemented via MS Visual C++/OpenGL to manipulate tree data which were supported by a backend relational data model with five data tables for stems, grades and prices, logs, defects and stem shapes. Network analysis was employed to achieve the optimal bucking solution with four different alternative stage intervals under bucking by value principle. Once all the data associated with a tree were retrieved, a 3-D tree stem could be displayed for either optimal or manual bucking based on the user\u27s option. Doyle and International 1/8 log rules were used to compute the log volumes during the bucking processes. Compared to manual bucking, total log value and volume gain from each tree-stem by using this computer bucking system could be increased averagely by 31.39% to 37.69% and 16.03% to 16.60%. Also, by computer optimal bucking, tree-stem utilization rate was increased by 10.11% to 11.23% compared to manual bucking results. The system execution time increased by 13, 108, and 1702 times while bucking stage interval changed from 4-foot, to 1-foot, 4-inch, and 1-inch. The optimal bucking system developed can be used as a training tool on desktop PCs and can also be installed on field PCs to aid field buckers

A Three-Dimensional Bucking System for Optimal Bucking of Central Appalachian

An optimal tree stem bucking system was developed for central Appalachian hardwood species using three-dimensional (3D) modeling techniques. ActiveX Data Objects were implemented via MS Visual C++/OpenGL to manipulate tree data which were supported by a backend relational data model with five data entity types for stems, grades and prices, logs, defects, and stem shapes. A network analysis algorithm was employed to achieve the optimal bucking solution with four different alternative stage intervals under the bucking by value principle. A total of 264 tree stems were measured in the field including stem dimensions, defects, sweep, and the manual bucking solution of each stem. Results when using the 3D optimal bucking system suggest that compared to manual bucking the total log value and volume gain from each tree stem could be increased on average by 31 to 38 percent and 16 to 17 percent, respectively. Results also show the individual tree stem utilization rate could be increased by 10 to 11 percent. The optimal bucking system developed can be used as a training tool on desktop PCs and can also be installed on field PCs to aid field buckers and operators of sawbucks. The 3D bucking optimization system developed in this research should be valuable to operators in the central Appalachian region due to the variability in tree stems and species of hardwoods

Visualization Experiment on Electrorheological Fluid in Dynamic Coupling Field

Due to lack of visualization experiment on the mechanism of electrorheological effect in dynamic field, a visualization experimental system is designed and successfully made. Through this experiment, the submicroscopic dynamic structural changes of electrorheological (ER) fluids in the coupling field composed by external electric field and flow field are observed. The experimental results indicate that the rheological behaviors of ER fluids are mainly influenced by the polarization forces and the hydrodynamic forces in the dynamic coupling field. And the experiment shows that the yield fracture of chain structures determined the yield strength of ER fluids firstly occurring near the plate electrodes, which expresses the microflow characteristic of velocity slip. Meanwhile, the capture effect has been verified in this experiment

Shoe–Floor Interactions in Human Walking With Slips: Modeling and Experiments

Shoe–floor interactions play a crucial role in determining the possibility of potential slip and fall during human walking. Biomechanical and tribological parameters influence the friction characteristics between the shoe sole and the floor and the existing work mainly focus on experimental studies. In this paper, we present modeling, analysis, and experiments to understand slip and force distributions between the shoe sole and floor surface during human walking. We present results for both soft and hard sole material. The computational approaches for slip and friction force distributions are presented using a spring-beam networks model. The model predictions match the experimentally observed sole deformations with large soft sole deformation at the beginning and the end stages of the stance, which indicates the increased risk for slip. The experiments confirm that both the previously reported required coefficient of friction (RCOF) and the deformation measurements in this study can be used to predict slip occurrence. Moreover, the deformation and force distribution results reported in this study provide further understanding and knowledge of slip initiation and termination under various biomechanical conditions

Forward Kinematics of Object Transport by a Multi-Robot System with Deformable Sheet

We present object handling and transport by a multi-robot team with a deformable sheet as a carrier. Due to the deformability of the sheet and the high dimension of the whole system, it is challenging to clearly describe all the possible positions of the object on the sheet for a given formation of the multi-robot system. A complete forward kinematics (FK) method is proposed in this paper for object handling by an $N$-mobile robot team with a deformable sheet. Based on the virtual variable cables model, a constrained quadratic problem (CQP) is formulated by combining the form closure and minimum potential energy conditions of the system. Analytical solutions to the CQP are presented and then further verified with the force closure condition. With the proposed FK method, all possible solutions are obtained with the given initial sheet shape and the robot team formation. We demonstrate the effectiveness, completeness, and efficiency of the FK method with simulation and experimental results.Comment: 8 pages, 6 figures, has been submitted to IEEE Robotics and Automation Letter

Foot Shape-Dependent Resistive Force Model for Bipedal Walkers on Granular Terrains

Legged robots have demonstrated high efficiency and effectiveness in unstructured and dynamic environments. However, it is still challenging for legged robots to achieve rapid and efficient locomotion on deformable, yielding substrates, such as granular terrains. We present an enhanced resistive force model for bipedal walkers on soft granular terrains by introducing effective intrusion depth correction. The enhanced force model captures fundamental kinetic results considering the robot foot shape, walking gait speed variation, and energy expense. The model is validated by extensive foot intrusion experiments with a bipedal robot. The results confirm the model accuracy on the given type of granular terrains. The model can be further integrated with the motion control of bipedal robotic walkers.Comment: ICRA 202

Multi-Robot Object Transport Motion Planning with a Deformable Sheet

Using a deformable sheet to handle objects is convenient and found in many practical applications. For object manipulation through a deformable sheet that is held by multiple mobile robots, it is a challenging task to model the object-sheet interactions. We present a computational model and algorithm to capture the object position on the deformable sheet with changing robotic team formations. A virtual variable cables model (VVCM) is proposed to simplify the modeling of the robot-sheet-object system. With the VVCM, we further present a motion planner for the robotic team to transport the object in a three-dimensional (3D) cluttered environment. Simulation and experimental results with different robot team sizes show the effectiveness and versatility of the proposed VVCM. We also compare and demonstrate the planning results to avoid the obstacle in 3D space with the other benchmark planner.Comment: 8 pages, 10 figures, accepted by RAL&CASE 2022 in June 24, 202

Accuracy Assessment of “Step-by-Step” Simulation Modeling Method for Rock Breaking by TBM Disc Cutters Assisted with Laser

Rock breaking by laser-assisted disc cutters is a novel high-efficiency rock breaking mode that combines mechanical stress induced by the disc cutters with thermal cracking by laser. This paper presented a “step-by-step” simulation modeling concept, and conducted an in-depth study on potential influencing factors of simulation accuracy at each key step. First, the prediction accuracy of laser holes in laser drilling simulation was discussed. Second, the SHPB simulation and experiment were carried out to evaluate the accuracy of the selected material constitutive model in simulating the dynamic fracture damage of rock. Then, taking the laser-assisted rock-penetrating process of the scaled disc cutter as an example, the simulation prediction accuracy of rock-breaking by the disc cutter was analyzed. Finally, the simulation and experiment of laser-assisted disc cutter penetration into rock was carried out, and then the feasibility of the “step-by-step” concept was analyzed. The results show that: (1) in the laser drilling simulation, the predicted accuracy of laser hole size is higher when the power is low; with the laser power increases, the large amount of glass glaze will affect the subsequent modeling accuracy; (2) the HJC model can be used to simulate the transient nonlinear fracture damage behavior of granite; (3) the damage morphology of the granite obtained by the penetration simulation is highly similar to the experimental results, and the load curve should be corrected by the peak point fitting method. The results show the application prospects of the proposed numerical modeling method in future laser-assisted TBM tunnelling