A review of independent metering control system for mobile machinery

Independent metering control is an advanced electro-hydraulic control technology for mobile machinery. By decoupling the inlet and outlet orifices in the conventional hydraulic valve, additional control degrees of freedom and energy-efficient mode switching are introduced. With onboard electronics controller and feedback, the hydraulic control is dependent on the software programming rather than hardware structure, such that the advantages, including simplification of valve structure, standardisation of valve technology, functional integration, flexible system configuration, and advanced control features, can be obtained. However, the resulting diversity of different layouts, configuration complexity, and expected high control effort still hinder a successful spread into industrial applications. This paper reviews commercial products and applications using independent metering control. The challenges, together with their key countermeasures and future trends, including flow control, fast response pilot drive, active damping control, smooth mode switching, as well as fault diagnosis and tolerance, are focused on and demonstrated in detail.