Study on Calculating Method of External Load on Digging Arm of Underground Excavator Truck

Abstract

Abstract The digging arm of underground excavator truck has many movable joints, complex structure and variable operation properties which results in the complicated loading. So it is difficult to obtain the external working load directly through the test. For this problem, the calculation of the external load on the digging arm of the underground excavator truck is studied by combining test and virtual prototype in this paper. The details include: Firstly, the static test of the digging arm was conducted using pressure sensor and displacement sensor, and the parameters of the virtual prototype built by Motion View software were modified. Then the pressure and displacement curves of each hydraulic oil cylinder are measured during the operation on site. The working process of digging arm is simulated and reconstructed by taking the measured displacement curves of each cylinder as the driving inputs, and outputs the curves of centre of mass coordinate, curves of acceleration and corresponding curves of torque. The rotary torque of external forces and gravity on a rotation axis (rotation axes of movable arm and pitch) should be equal to the sum of torque of the product of each component’s mass and the acceleration of the centre of mass on that point according to the law of torque calculation. Thus, the non-homogeneous linear equations of external loads (horizontal, vertical and lateral loads) are derived under the actual conditions. And external loads were solved by substituting the above curve parameters into the equations. Finally, the obtained external load is reloaded into the virtual prototype of the digging arm to simulate the force of actual digging process. The error is less than 5% by comparing the calculated and test values of the oil cylinders force of rod and bucket and the effective strain error of the movable arm is less than 10%. So the correctness of the derivation method of external load and the dynamic model considering inertial force is verified. It provides theoretical and algorithm support for the next acquisition of load spectrum and fatigue analysis of digging arm.