A practical load detection framework considering uncertainty in hydraulic pressure-based force measurement for construction manipulator

Abstract

This paper proposes a practical framework for detecting (identifying the on-off state of) the external force applied to a construction manipulator (front load) by using a hydraulic sensor. Such a detection system requires high accuracy and robustness considering the uncertainty in pressure-based force measurement. Our framework is thus organized into (i) identifying the dominant error force component (self-weight and driving force) using theoretical and experimental estimation and binarizing the analog external cylinder force, (ii) evaluating detection conditions to address indeterminate conditions such as stroke-end, singular posture, and impulsive or oscillatory force and redefining three-valued outputs such as on, off, or not determinate (ND), and (iii) outputting the front load decision by combining all the cylinder decisions to improve robustness through priority analysis. Experiments were conducted using an instrumented hydraulic arm. Results indicate that our framework adequately detects on, off, and ND outputs of the front load in various detection conditions without misidentification.

Relative accuracy enhancement system based on internal error range estimation for external force measurement in construction manipulator

“…and , were derived from the experimental data, but they are affected by various minor factors such as the cylinder cushion and connector shape, so the proposed estimation using limited parameters (i.e., cylinder speed) cannot avoid a measurement error [14]. Such modeling errors are addressed mainly in the control engineering field by means such as model-correction using machine learning [11] and model-compensation using feedback [12].…”

“…and must be determined by taking into account the hysteresis of friction and the manipulator posture and velocity, so we determined them through dynamic experiments. We obtained waveforms when a manipulator moving at maximum velocity was suddenly stopped, to analyze damping time, in previous study [14]. We reanalyzed these data as shown in Fig.…”

“…We also obtained the relations among cylinder force, velocity, possible temperatures (30-60 ) as shown in Fig. 5 (b), to derive cylinder driving force, in the previous study [14]. We recalculated the maximum difference from estimated driving force at each cylinder velocity.…”

“…The enhancer thus excludes a cylinder at the stroke-end from among the measuring cylinder candidates, which means that one combination is uniquely defined. Moreover, to improve visualization for analyzing experimental results more easily, the measured external force vector was preprocessed by using the on-off detection framework developed in previous work [14].…”