Development of an integrated tracking control algorithm and a test platform for autonomous excavation

Date
2020-03-01
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Abstract
Since construction is part of the industrial sector where a large amount of labor is required and workers operate under harsh environmental conditions, the transformation from manual to autonomous operation in modern construction sites can be a solution to improve productivity, accuracy, and efficiency. Excavator is one of the key equipment in the construction field for earthmoving operations. In this study, an effective control strategy for excavation is introduced considering the position, contour, and force which are mutually associated factors for successful autonomous excavation. For position tracking of the bucket tip, a non-linear PI controller was devised to control the hydraulic actuators of the boom, arm, and bucket links of the excavator. To compensate for the ground resistive forces, an impedance controller was designed. Finally, contour compensation was considered to generate an optimal path of the bucket tip by reducing the contour profile error that is vital for skilled tasks such as ground levelling. Furthermore, the time-delayed control strategy was adopted to mitigate dynamic uncertainties. The performance of the developed algorithm was evaluated through co-simulation in multi-physics domains. Simulation results showed the designed control algorithm provided good tracking results in terms of the desired position and force of the bucket tip. In addition, the controller could reduce the contour error between the desired trajectory of the bucket tip and its actual trajectory. The simulation results were tested experimentally using the test platform that was developed by modifying an existing mini-hydraulic excavator. Experimental data was gathered to conduct an analysis of the bucket tip’s tracking error and, the error between the desired ground terrain profile and the excavated ground terrain profile. Experimental results showed the developed effective control strategy provided good tracking results of the bucket tip and reduced the standard deviation between the desired ground terrain profile and actual excavated ground terrain profile.
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Keywords
Excavator, Position control, Contour control, Force control, Simulation
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