Climate change is the most pressing environmental challenge of our time. The transport sector was the largest contributor to UK greenhouse gas emissions (GHG) in 2020, with an overall contribution of 24% [1]. While decarbonisation of on-road transportation, such as cars, buses and trucks, is well underway by employing electric alternatives, the important sector of off-road vehicles is technologically far behind and represents a major contributor to GHG emissions. In 2018, the total GHGs emission of UK off-road vehicles was 11,043 kilotonnes [2], which is equivalent to the GHGs emission from 12.2 Giga pounds of coal burned, or the annual energy use of 1.4m homes' [3]. Hydraulic fluid power transmission is widely used in off-road vehicles, such as construction and agricultural machinery. Current state-of-the-art hydraulic fluid power components and control technologies continue to be highly energy- and cost-inefficient and generate significant CO2 emissions, as speed and force are controlled by using metering valves to throttle the flow and control the hydraulic pressure. This is a simple but extremely inefficient method because the energy is dissipated through an orifice and consequently lost as heat; it is common for more than 50% of the input power to be wasted in this way. A recent study showed that the average energy power efficiency of fluid power systems is only 21%, and a 5% improvement in efficiency can save 0.51 quadrillion Btu of energy, which relates to a saving of US$10.1 billion and a reduction in CO2 emissions of over 33.95 million tonnes. Therefore, there is an urgent need to create new technologies to significantly improve hydraulic energy efficiency to enable efficient decarbonisation and electrification of off-road vehicles and achieve Net Zero. To significantly improve hydraulic fluid power efficiency to over 90%, I will provide a transformative change in next-generation digital hydraulic components and control technologies by developing new additively manufactured high-performance digital hydraulic valves (WP1) and novel digital hydraulic converters (WP2) to reduce hydraulic pressure and energy losses. I will create high-fidelity analytical modelling tools to understand the underlying science of complex fluid power components and systems and establish new additive manufacturing-based designs and methodologies for energy-efficient digital valves and converters. An intelligent control platform (WP3) which will integrate model- and machine-learning-based control algorithms, will be developed to control the digital valves and converters to achieve their optimum performance and maximum efficiencies. These transformative and emerging technologies will be implemented on off-road vehicles (e.g. excavators, elevating platforms) as technology demonstrations and case studies (WP4) in order to produce future digital hydraulic fluid power products and solutions for Net Zero (WP5). I will conduct scoping studies in Phases 1 and 2 to define new research directions, deliver high-impact publications and conduct the pathways to impact activities. The research outcomes will generate significant academic, economic and societal impact. They will ensure the UK has a unique world-leading research activity in digital fluid power and its future applications. UK-based companies will receive a competitive advantage in exploiting the deliverables from the Fellowship and in significantly influencing the application potential of digital hydraulic fluid power in the market, which can have an immense range of customers. The research outcomes will provide long-term zero-carbon machines for people living and improving their quality of life. [1]. 2020 UK Greenhouse Gas Emissions, Final Figures. National Statistics. Department for Business, Energy & Industrial Strategy. 2022. [2]. National Atmospheric Emissions Inventory UK Data. 2022. [3]. Greenhouse Gas Equivalencies Calculator, the US Environmental Protection Agency. 2022.

The applications of hydraulics are diverse. Hydraulic actuation offers many benefits including compact and lightweight design due to high power density, fast response and good controllability. In most fluid power hydraulic systems, speed and force of the load are controlled using valves to throttle the flow and reduce the hydraulic pressure. This is a simple but extremely inefficient method as the excess energy is lost as heat, and it is common for more than 50% of the input power to be wasted in this way. An alternative method is to use a variable capacity hydraulic pump or motor. This is more efficient, but variable capacity pumps and motors are expensive.The proposed work investigates two methods of increasing the efficiency of hydraulic systems while maintaining good control of speed and force without the expense associated with variable capacity pumps. The first method is the Switched Reactance Hydraulic Transformer (SRHT), a novel device for controlling the flow and pressure of a hydraulic supply. The second method is the Electro-Hydrostatic Actuator (EHA). Both of these systems increase efficiency by removing the need for control valves. For both applications, active fluid-borne noise attenuation techniques may be necessary.Switched Reactance Hydraulic Transformer (SRHT):A new device for controlling the flow and pressure of a hydraulic supply is proposed. It consists of a high-speed switching valve and an 'inertance tube'. Acting as a transformer, the device is able to boost the pressure or flow. The device could be configured to provide the functionality of a variable capacity pump, a pressure relief valve, a pressure compensated flow control valve or a proportional valve. Each of these control modes can be achieved without an expensive variable capacity pump and without the inefficiency inherent in a control valve. Previous work highlighted problems of noise and parasitic power losses. If these problems can be overcome using more recent materials and techniques combined with careful design, it could provide a more cost-effective efficient alternative to pressure/flow control valves.Electro-hydrostatic Actuation (EHA):In EHAs, a variable speed electric motor drives a fixed displacement pump which delivers flow directly to a linear actuator. Moving from centralised power supplies to distributed multi-pump/actuator systems brings reductions in power levels for individual subsystems. Furthermore, valveless electro-hydrostatic actuation systems provide benefits of greater efficiencies compared to conventional valve-controlled hydraulic systems, further reducing the power requirements. EHA systems can suffer from noise problems because of the close coupling between pump and actuator, allowing direct transmission of pressure pulsation. The challenges are to achieve good dynamic performance while achieving higher efficiency, low noise and reduced system weight and size.Active Fluid Borne Noise Attenuation:Fluid-borne noise (FBN) is a major contributor to air-borne noise and vibration in hydraulic systems as well as leading to increased fatigue in system components. Although passive systems to reduce the noise have been shown to be effective, they require tuning to specific systems, their attenuation frequency range is limited and they may be bulky. Furthermore, attenuation devices based on expansion chambers, accumulators or hoses are likely to be unsuitable for EHA or SRHT systems as they add compliance to the system and would impair the dynamic response. Active devices, which add energy to the fluid to cancel out or destroy the pressure ripple to reduce noise levels, can be effective at a much wider range of frequencies and system designs without affecting the system's dynamic response. Both the SRHT device and EHA system may suffer from noise issues, and as such, will benefit from active noise attenuation.

The Scottish Manufacturing Institute aims to research technology for manufacture, addressing the requirements of European, UK and regional industries. It taps into the broad expanse of research at Heriot-Watt University to deliver innovative manufacturing technology solutions. The SMI delivers high quality research and education in innovative manufacturing technology for high value, lower volume, highly customised, and high IP content products that enable European and UK Manufacturers to compete in an environment of increased global competition, environmental concern, sustainability and regulation, where access to knowledge, skills and IP determine where manufacturing is located. Our mission is to deliver high impact research in innovative manufacturing technologies based on the multidisciplinary technology resource across Heriot-Watt University, the Edinburgh Research Partnership, the Scottish Universities Physics Alliance and beyond. The Institute is organised into three themes:- Digital Tools;- Photonics; and - MicrosystemsThe vision of the Digital Tools Theme is to provide tomorrow's engineers with tools that will help them to easily capture, locate, exploit and manipulate 3D information for mechanical products of all kinds using distributed, networked resources. Photonics has strong resonance with the needs of developed economies to compete in the 21st Century global market for manufacturing, providing: routes to low cost automated manufacture; and the key processes underpinning high added value products. We have a shared conviction that photonics technologies are an essential component of any credible strategy for knowledge-based industrial production. The Photonics Theme vision is for the SMI to be internationally recognised as the leading UK focus for industrially-relevant photonics R&D, delivering a mix of academic and commercial outputs in hardware, process technology and production applications.The principal strategy of the Microsystems Theme is to research into new integration and packaging solutions of MEMS that are low cost, mass manufacturable and easily adoptable by the industry. The vision is to become a European Centre of Excellence in MEMS integration and packaging over the next 5 years. We thus aspire to service UK manufacturing industry with innovative technology for high value, lower volume, highly customised, and high IP content products; and to help UK industry expand globally in an internationally competitive market.