An electro-hydraulic system is a control system that combines electrical and hydraulic power to operate machinery and equipment. In this type of system, electrical signals are used in place of mechanical force to regulate the flow of hydraulic fluid, enabling functions such as movement, lifting, turning, and holding in industrial machines. Increasingly, excavators and wheel loaders are adopting electro-hydraulic systems rather than hydro-mechanical systems in order to achieve greater control accuracy and improved operational efficiency. This study examines several common hydraulic control methods used in excavators, including Negative Flow Control (NFC), Positive Flow Control (PFC), Load-Sensing Control (LSC), and Power-Limitation Control (PLC). In addition, linearized multiple-input, multiple-output models of variable-displacement piston pumps and working loads are developed and analyzed with respect to stability and controllability. The control input signals are further investigated and designed according to the objectives and characteristics of NFC, PFC, and LSC systems. Furthermore, an integrated electronic control algorithm is proposed, incorporating electronic sensor feedback to enable the machine to apply and switch among NFC, PFC, and LSC either manually or automatically. Power-Limitation Control (PLC) is also implemented through swashplate angle feedback to prevent the machine’s prime mover from stalling. The integrated control system provides the flexibility to optimize machine efficiency and performance under varying working conditions, while also accommodating different operator preferences. This work is novel in that it unifies multiple conventional pump control methods into one integrated electro-hydraulic control platform. Its practical impact lies in enabling a single excavator system to achieve better adaptability, improved operating efficiency, and more flexible control under varied task demands. Such a capability is especially valuable for modern construction equipment, where intelligent control, reduced energy consumption, and higher productivity are increasingly important.
Clement Wang (Fri,) studied this question.