Inferring Cable-Suspended End-Effector Oscillations From Hydraulic Actuators’ Responses in Diaphragm Wall Hydraulic Grabs

A Diaphragm Wall Hydraulic Grab (DWHG), used in civil engineering for bulk excavation, is featured with a cable-suspended end-effector (also named attachment tool). The end-effector begins to oscillate during DWHG operation. Essential insights into the DWHG’s performance or productivity in operation could be derived from end-effector oscillations. However, due to limited robustness, the end-effector oscillation curves from a DWHG in operation can not be tracked directly by motion sensors attached to the end-effector. This article presents and evaluates a novel approach for DWHGs to infer cable-suspended end-effector oscillations from their hydraulic actuators’ responses. Hydraulic actuators’ responses depict the changes of hydraulic parameters in hydraulic actuators due to end-effector oscillations. The main contribution of this article is an investigation of how far oscillations of a cable-suspended end-effector in a DWHG can be inferred from their hydraulic actuators’ responses. For this purpose, a workflow is conducted: firstly, end-effector oscillations and their hydraulic actuators’ responses are collected for a typical DWHG steering sequence. Secondly, the collected end-effector oscillation and hydraulic actuators’ response curves are analyzed and processed. Thirdly, a model to infer end-effector oscillations from hydraulic actuators’ responses is built. Fourthly, an evaluation shows that the inferred oscillation curves (model output) are similar to the true end-effector oscillations. Note to Practitioners—This article is motivated by the demand to determine the oscillation curves of the cable-suspended end-effector (also named attachment tool) at a Diaphragm Wall Hydraulic Grab (DWHG) used in civil engineering for bulk excavation. Existing approaches for construction machines commonly install motion sensors at the end-effector to track its oscillations. However, mounting any sensors at the end-effector in DWHGs is not practicable because the end-effector is exposed to mechanical shocks and moisture. Thus, mounted sensors would be damaged or demolished. This article suggests and investigates a novel approach for DWHGs to infer end-effector oscillations from pressure data in hydraulic actuators that actuate the end-effector. Therefore, the pressure curves at the hydraulic actuators are tracked while the end-effector oscillates and are utilized afterward to infer these oscillations. A practical guide for a DWHG is presented and evaluated to collect, analyze, process, and utilize pressure data from hydraulic actuators to infer end-effector oscillations.