Visual and real-time simulation of dynamic cutting of earthmoving work

Abstract: The surface objects of terrain are the main operation objects of earthmoving machinery, and soil cutting resistance from the process is a basic source of all vehicle dynamic phenomenons. The soil cutting resistance is the basis of mathematical model of excavator - terrain dynamic interaction, which has an important influence on hydraulic system, working device, motion mechanism and vehicle performances. Hydraulic excavator as a representative model of engineering machinery, is widely used in construction, mining, forestry, municipal engineering and other fields. The most common working condition of excavator is earthmoving work. However, because of the complexity of working environments, even if the skilled operator couldn't completely understand the status of operation terrain areas, soil parameters, soil - cutting resistance, etc. Especially the soil - cutting resistance has a great significance for the phase of product design and development and path planning. Due to unpredictability of operational terrain areas, improper operation often causes safety accidents, and even machine apart. At present, most construction machinery driving simulators are typically limited to the modeling and simulation of the kinematics and dynamics of the working device under no-loading or steady loading condition. This neglects the influence of the soil excavation resistance on the system under operating conditions. Therefore, it is difficult for these simulators to realistically capture the dynamic interaction between the device and environment, and impossible to make a proper evaluation of the closed-loop human-machine-environment system, which caused the physics behavior of vehicle was not accurate enough. This caused the sense of reality is very low and couldn't provide drivers enough immersion, forming the situation that demonstration effect is greater than engineering application. On the basis of geometric entity modeling in visual simulation engine, Delta3D, real-time multi-body dynamics simulation platform, Vortex, are adopted to build the software framework and simulate dynamic characteristics of excavator, which also has complex collision detection function. A simulation platform for hydraulic excavator driving simulator was established, and carried on typical driving conditions tests of the excavator in the virtual environment, such as excavation, outward transport, pouring soil. It assumed that soil particles are mainly destroyed by shear fracture during digging operations, according to theory of passive soil pressure presented by Terzaghi, cutting resistance model of the soil in working condition is established, which assumed the soil as rigid-plastic material and use the static equilibrium to solve the soil particles resistance acting on excavator bucket..According to the actual operation situations of digging bucket, terrain inclination, acceleration, and side friction from soil to bucket parameters are applied to revise FEE put forward by Reece. The cutting resistance forces from soil to bucket in three interaction operations are obtained, and the factors affecting the cutting resistance were analyzed. By changing the soil cutting parameters, the system can realize the simulation of soil cutting resistance under different working condition. The visualization and real-time simulation of dynamic cutting of earthmoving work platform established provides highly accurate and real-time simulation of the kinetics of hydraulic excavators under a virtual environment. The system has characteristics of high fidelity, well real-time performance and strong immersive, and can be not only used for auxiliary training, guaranteeing the stability in interaction process and improving work efficiency, but also used in the engineering application, providing intuitive measurement method of product design and development, evaluating performance, operating characteristics, control strategy, human-machine safety, etc. With the interaction simulation platform, operators can make correct evaluation of a closed loop system for human - machine - environment. Furthermore, the visualization and real-time simulation of dynamic cutting of earthmoving work platform can provide the multi-repeated data for evaluation of the vehicle manipulation performance for hydraulic excavator.