Digital hydraulic control09 April 2024

Ashcourt Group is trialling Danfoss Dextreme in a Volvo excavator

​Hydraulic systems are entering a new dawn of digital control, with a number of emerging innovations expected to provide notable benefits

Digital hydraulic control; smart pump technology; intelligent fluid systems. Whatever the terminology, it is clear that hydraulic systems are about to enter a phase of transition, whereby innovations will help users of mobile machines enjoy gains such as greater energy efficiency and reduced emissions.

The importance of these sustainability-related objectives is gaining top-level attention. In September 2023, the UK Government’s Department for Energy Security and Net Zero published the phase 2 details of its ‘Red Diesel Replacement’ competition. Here, a number of projects involve the development of end-to-end low-carbon solutions that could potentially replace red diesel-using technologies at construction and mining/quarrying sites.

Danfoss Scotland, part of hydraulics and electric powertrain systems supplier Danfoss Power Solutions, is the owner of one project with ambitions to enhance the energy efficiency of excavators, which currently waste around 70% of useful power delivered by the engine. Phase 2 of the Red Diesel Replacement competition sees this particular project gain nearly £5 million in funding.


The Danfoss project centres on the company’s new ‘Dextreme’ system. At its heart is its Digital Displacement Pump, said to be the industry’s first truly digitally controlled hydraulic pump for off-highway machinery. A dedicated digital controller activates each pump piston individually, providing a fast and accurate response to system demand via multiple independently controllable outlets. The pump delivers full and part-load efficiency by using only the pistons needed to meet the load.

To minimise the risk for OEMs, Dextreme consists of three incremental pathway solutions: Swap, Flex and Max. The most basic system configuration, Dextreme Swap, replaces the excavator’s main hydraulic pump with the Danfoss Digital Displacement Pump, digital controller and custom software. The result is a 15% reduction in fuel use and CO2 emissions compared with an excavator featuring a conventional swash-plate pump.

Danfoss will shortly conclude a 12-month trial (2,000 operating hours) of Dextreme Swap in partnership with Yorkshire-based construction contractor Ashcourt Group. Involving three 20-tonne Volvo EC200 excavators, data from the trial will draw comparisons with Ashcourt’s existing fleet of standard Volvo EC200 machines. The integral digital pump controller provides extensive data in support of real-time performance monitoring and diagnostics.

The next pathway, Dextreme Flex, dynamically allocates the pump flow to services based on demand, reducing throttling losses in the main control valve. Dextreme Max, the most advanced pathway, adds energy recovery from excavator motions such as slew deceleration and boom down, as well as direct load control from the pump itself, further cutting throttling losses. Dextreme Flex and Dextreme Max offer potential energy savings of 30% and 50%, respectively.


As part of the Red Diesel Replacement competition, Danfoss will validate Dextreme Max in a 30-tonne electric excavator. Work to integrate the Digital Displacement pump, Editron electric drive and other system architecture components began in January 2024. Once complete, operational tests will commence at a UK quarry, with project completion estimated in February 2025.

“Electrification offers a promising route to decarbonisation, but the vast power consumption of excavators means they need costly batteries and charging infrastructure,” says Leif Bruhn, head of digital displacement, Danfoss Power Solutions. “This expense is a major barrier to the broader adoption of electric machines. Excavators account for 50% of emissions from construction machinery. By improving excavator energy efficiency, we can reduce the battery size and charging energy required to perform the same amount of work. This will bring down costs, accelerating the transition to zero-carbon energy sources.”


The ambitions of the Danfoss project are to demonstrate that improvements in excavator efficiency make it possible to: reduce battery capacity requirement from three packs to two; reduce electrical load on the charging infrastructure; lower overall capital and operating expenses compared with a baseline excavator; cut total cost of ownership in comparison with a diesel machine; and offer the same or better productivity and run time than baseline excavators.

“This project is an incredible opportunity to prove the efficacy of a new system solution and architecture, demonstrating that large-scale innovation is still possible in hydraulics,” states Jeff Herrin, senior vice president of research, development and engineering at Danfoss Power Solutions. Sarah Acheson, systems engineer - digital Displacement, Danfoss adds: “We can see a path to saving around 80 mega tonnes of CO2 annually by 2030.”

To back up this goal, Danfoss is building a £25 million low-carbon centre of excellence in Scotland that will bring digital displacement pumps and Editron electric drives to the construction market, leading to a new-generation of digitally enabled, efficient, electrically powered construction machines.


Beyond pumps, there are, of course, further opportunities for digital technologies in the hydraulic mobile machine arena. A case in point is the HydraForce Innercept digital proportional control system, a patent-pending proportional control valve featuring an integrated linear variable differential transformer (LVDT).

“Innercept combines the flexibility of a five-way proportional hydraulic cartridge valve with the precision of electronic control and the convenience of integrated digital feedback, thanks to the LVDT transducer,” explains Travis Schmidt, global engineering solutions & electronics engineering manager at HydraForce. “It combines servo-valve accuracy and repeatability with cartridge flexibility and compact dimensions.”

Created specifically for precision off-highway applications, particularly autonomous machines, HydraForce says the system offers less than 1% hysteresis and comes at a fraction of the cost of industrial-style servo valves. Beyond the proportional flow control valve and LVDT, the system comprises another key component: two-output closed-loop PID control, which receives CAN messages from the vehicle’s automatic steering control.

Due to growing demand for precision control, quick response times and improved efficiency, it is clear that new digital hydraulic control solutions are emerging which allow mobile machinery manufacturers to reduce time to market and deliver vital gains for end users. A proverbial (digital) display of force.

Better fuel efficiency

Digital hydraulics to facilitate energy-saving motion control: this is the premise of NorrDigi from Norrhydro. With the system’s multi-chamber cylinders and intelligent digital valve control, NorrDigi delivers only the power needed at any given time. Developed for the mobile machinery market, the company suggests users will see a 45-60% improvement in fuel efficiency and a 5-12% increase in productivity.

Unlike traditional cylinders with two chambers – one pushing, one pulling – the NorrDigi digital hydraulic actuator uses four chambers that connect in up to 16 different permutations, depending on the required load. The resulting system efficiency (optimal chamber use enables precise speed and force control) makes it possible to discard or downsize much of a machine’s hydraulic system: it removes the need for a main control valve, along with excessive pump capacity, piping and hoses.

“It’s a little like a 16-speed linear transmission,” explains Peter Stambro, vice president - business development at Norrhydro. “Multi-chamber cylinders have been around for a while, but we combine ours with advanced electronic control systems, whose complex algorithms and computational speed allow for instant response using only a fraction of the energy for the same machine manoeuvre or action compared with a traditional system.”

Thanks to system connectivity, a vast amount of system data is available. Volvo Construction Equipment and Norrhydro took part in a development project to validate NorrDigi using a Volvo EC300E 30-tonne excavator.

Thomas Bitter, head of technology at Volvo CE, adds: “The system shows the greatest benefits in larger machines – in the case of excavators, 30 tonnes and above. However, in the future, the technology could also be useful in electric machines, where higher hydraulic system efficiency would effectively extend battery life and the operating window.”

Steed Webzell

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