Impact-Resilient Orchestrated Robust Controller for Heavy-duty Hydraulic Manipulators

TL;DR

This work addresses the challenge of achieving high-precision, impact-resilient control for heavy-duty hydraulic manipulators without relying on end-effector force sensors. It combines a neuroadaptive impedance controller with a Generalized Momentum Observer (GMO) formulated in Plücker coordinates, integrated within a Virtual Decomposition Control (VDC) framework and stabilized through Virtual Stability and Virtual Power Flow concepts. A novel GMO in Plücker coordinates is developed to estimate contact forces directly from inertial dynamics, enabling sensorless force-aware impedance control and SGUUB stability for the full $6$-DoF HHM. Experimental results on a real industrial HHM demonstrate subcentimeter tracking accuracy in free motion and an up to $80\%$ reduction in contact impact, highlighting practical viability for collision-rich, heavy-duty manipulation tasks.

Abstract

Heavy-duty operations, typically performed using heavy-duty hydraulic manipulators (HHMs), are susceptible to environmental contact due to tracking errors or sudden environmental changes. Therefore, beyond precise control design, it is crucial that the manipulator be resilient to potential impacts without relying on contact-force sensors, which mostly cannot be utilized. This paper proposes a novel force-sensorless robust impact-resilient controller for a generic 6-degree-of-freedom (DoF) HHM constituting from anthropomorphic arm and spherical wrist mechanisms. The scheme consists of a neuroadaptive subsystem-based impedance controller, which is designed to ensure both accurate tracking of position and orientation with stabilization of HHMs upon contact, along with a novel generalized momentum observer, which is for the first time introduced in Plücker coordinate, to estimate the impact force. Finally, by leveraging the concepts of virtual stability and virtual power flow, the semi-global uniformly ultimately boundedness of the entire system is assured. To demonstrate the efficacy and versatility of the proposed method, extensive experiments were conducted using a generic 6-DoF industrial HHM. The experimental results confirm the exceptional performance of the designed method by achieving a subcentimeter tracking accuracy and by 80% reduction of impact of the contact.

Figures (14)

• Figure 1: Interconnected rigid bodies with attached Plücker coordinates.
• Figure 2: Scheme of 6-DoF heavy-duty hydraulic manipulator (HHM) with VDC approach. a) general configuration of HHM, b) decomposition of HHM into subsystems, c) Scheme of VDC with VCP concept
• Figure 3: Impact resilient control scheme. The impedance law $\dot{\mathcal{X}}_r$ computed in (\ref{['DXr']}), is transformed into joint space command $\Dot{q}_r$ which is executed by the control approach in hejrati2023orchestrated. The actuator-level control command, $u_{fr}$ being desired voltage, is designed to generated required piston force $f_{pr}$, accomplishing control objectives. The command $u_{fr}$ controls the hydraulic valves. Please see hejrati2023orchestrated for detailed explanation.
• Figure 4: End-effector of HHM approaching an environment
• Figure 5: Experimental setup

Theorems & Definitions (13)

• Definition 1
• Definition 2
• Definition 3
• Theorem 1
• Remark 1
• Remark 2
• Remark 3
• Theorem 2
• Proof 1
• Lemma 1