The electrification of mobile machinery is rapidly transforming the hydraulics industry. But what happens if the electric motor and hydraulic pump are built together into a single unit? That is exactly what new research from Linköping University is investigating – and the results point to both major opportunities and several technical challenges for future hydraulic systems.
In a new doctoral thesis from Linköping University, researchers analyze how electric machines and hydraulic pumps/motors can be integrated into so-called electrohydraulic energy converters. The research focuses particularly on how hydraulics need to evolve to work optimally together with modern electric drive systems.
Hydraulics must adapt to electrification
Traditional hydraulic systems have historically been developed for diesel engines operating at relatively constant speeds. Electric drivetrains function differently and place entirely new demands on hydraulic machinery.
The research shows that electrification opens opportunities for:
- higher energy efficiency
- energy regeneration
- variable speed operation
- improved controllability
- lower noise levels
- more compact system solutions
At the same time, the study concludes that today’s hydraulic pumps and motors are not optimized for electric operation. To fully benefit from electrification, lubrication, commutation, and internal flow paths need to be redesigned.
The opportunity: integrating the hydraulic pump into the electric motor
One of the most interesting conclusions in the research is the possibility of placing the hydraulic machine directly inside the core of the electric motor. This would allow unused space within the electric machine to be utilized for hydraulics.
Potential benefits include:
- significantly higher power density
- fewer components
- lower weight
- more compact installations
- fewer bearings and mechanical parts
- potentially lower costs
The researchers point out that such solutions are particularly interesting for mobile machinery where installation space and energy efficiency are becoming increasingly important.
The challenges: noise, cooling, and high speeds
Despite the major opportunities, several technical challenges remain before the technology can achieve broad commercial adoption.
One of the biggest challenges is noise. When the diesel engine disappears, hydraulic noise becomes much more noticeable. As a result, factors such as valve plate design and pressure pulsations become far more important than before.
Another major challenge is cooling and lubrication at high rotational speeds. Electric drive systems enable both very low and very high speeds, placing hydraulic machines under new types of stress. The researchers describe how leakage oil flows and cooling strategies need to be optimized to manage heat generation in integrated systems.
Control systems also become more advanced when hydraulics and electric drivetrains are required to work together seamlessly.
Important research for the future of mobile hydraulics
The research was carried out at Linköping University, which has long been a leading institution in mobile hydraulics and energy-efficient hydraulic systems research. The work was conducted within the university’s eHydraulics research program focusing on future electrified working machines.
The thesis was written by researcher Alexander Murrenhoff and examines the development of electrohydraulic energy converters with a focus on integrated solutions between electric machines and hydraulics. Supervisors and the research environment are connected to Linköping University’s well-known hydraulics research within fluid and mechatronic systems.
The research also has clear industrial relevance for future construction machinery and mobile hydraulic systems, where both energy efficiency and electrification are becoming decisive competitive factors.
Conclusion: hydraulics will play a key role in electrification
Perhaps the most important conclusion from the research is that hydraulics will not disappear with electrification – quite the opposite. For mobile machinery with high power demands, hydraulics will likely remain central in the future.
However, hydraulics must evolve together with electrification.
Integrated electric and hydraulic solutions could create significantly more efficient, compact, and intelligent machines. At the same time, the technology requires new solutions for noise, cooling, lubrication, and system control.
For the hydraulics industry, this means major opportunities – but also a clear demand for innovation in the years ahead.
