Velocity and Position Hybrid Control for Excavator Boom Based on Independent Metering System

Abstract

Excavators are widely used in construction, mining, and other projects. However, there are certain environments, such as chemical substance leakage and conflagration sites, which are not suitable for on-site operation. In such situations, the necessity for automatic control and position control is considerably high and it is the development trend of the excavators. In this paper, a position control strategy combined with velocity feedforward is proposed for the excavator boom to achieve position and velocity control simultaneously. Moreover, an independent metering system is introduced to reduce throttling loss. In this work, the controller is designed with two modes-velocity control and position control-based on the difference between the target and real displacements. When the target position is given, if the difference is sufficiently large, the system operates in the velocity control mode. In this mode, the velocity feedforward signal is generated as a designed type to control the cylinder velocity, and the desired trajectory can be obtained by integrating the generated velocity. In order to account for the velocity error and realize trajectory tracking, displacement control is employed to compensate for the velocity feedforward control. During this process, the valve can be fully open to reduce throttling loss. When the boom approaches the target position, the system operates in the position control mode. With this strategy, position control and velocity control can be achieved simultaneously, fast positioning and low energy consumption are also realized. In order to verify the feasibility of the foregoing strategy, a test rig is installed on a 6-t excavator. The test results show that the boom can move smoothly to the target position along the desired trajectory and achieve fast positioning. The investigation can provide some reference for the automatic operation of mobile machinery.