Review and Development Trend of Digital Hydraulic Technology

Abstract

Since the emergence of digital hydraulic technology, it has achieved good results in intelligence, integration, energy saving, etc. After decades of development, and it has also attracted wide attention in the industry. However, for many years, the definition of digital hydraulic technology has differed between researchers, and there is no uniform definition. Such a situation affects the development of it to a certain extent. Therefore, this paper gives the exact definition of digital hydraulic technology based on a large number of researches on it. At the same time, the paper analyzes the research status and developmental process of the such a technology, and we forecast the development trend of it.

Pitch Control of a Digital Hydraulics Pitch System for Wind Turbine Based on Neuro-Fuzzy Digital Pitch Controller

“…Though DH is advantageous, the controllability of DH is still a tedious task [18]. The different valve actuation methods that are implemented in the DH system are Pulse Width Modulation (PWM), Modified Pulse Width Modulation (MPWM), Pulse Frequency Control (PFC), Pulse Number Modulation (PNM), and Pulse Code Modulation (PCM) [15,19]. Research work on DFCU for WT is very limited and most of the work is focused on Digital Fluid Power (DFP) transmission [20][21][22][23].…”

“…The DHPS uses several 2/2 hydraulic valves arranged in parallel combination along with an orifice known as Digital Flow Control Unit (DFCU) as shown in Fig. 1 [15,16]. Moreover, the sizing of the orifice plays a vital role in replicating proportional flow.…”

Simulation of a high frequency on/off valve actuated by a piezo-ring stack for digital hydraulics

“…This simple calculation explains the reason why these power conversion systems are inefficient in terms of power consumption. A recent research field aims at substituting servovalves and proportional valves with digital hydraulics, in an attempt to reduce such high-power dissipations [11][12][13]. A digital hydraulic circuit can be either that shown in Fig.…”

“…In addition to reducing the pressure drops and hence the power losses, the digital hydraulic technology directly adopts digital signals to control valves without D/A conversion, which simplifies the control mode and removes the noise sensitivity typical of servovalves [11]. In spite of the advantages that it can provide, digital hydraulics does not have practical applications yet, apart from very small circuits, because of the difficulty in manufacturing the ON/OFF valves required for this purpose.…”

“…Indeed, these valves must be very fast, of the order of a few milliseconds, to change state between open and closed. In the literature, there are some examples of novel valve architectures designed to achieve very fast response, but these designs are limited to low flow applications and are not suitable for high flow circuits [11].…”