Electro-hydraulics are enhancing off-highway automobile performance and effectivity, enabling machine management and offering the constructing blocks for energy-recovery methods. Trade consultants give perception into the evolution of this expertise and predict future developments
Over the previous three a long time off-highway automobile designers have moved away from constructing machines which have hydraulics managed by way of mechanical methods and hydraulic pilot strains to utilising digital management – electro-hydraulics. However, whereas such methods are properly established, the complete potentialities of this structure are nonetheless being explored.
Though hydraulic actions are nonetheless very a lot analogue in nature, the controls that operators use are virtually wholly now within the digital age, although the change didn’t come about in a single day, relatively by way of a gradual evolution.
That is borne out by element specs. Danfoss, for instance, after years of designing parts that might be used with both mechanical or digital interfaces, has now utterly transitioned its new parts to electro-hydraulics.
“The interface of our hydraulic merchandise has gone by way of three levels of evolution,” says Jeff Herrin, senior vice chairman of R&D at Danfoss Energy Options. “The primary stage, courting again a few years, concerned hydraulic and mechanical interfaces. For instance, a hydraulic pump managed by a lever that an operator may use to create the specified stream.
“The second stage launched designs with each lever entry and digital management. This transitional section was essential as a result of business shifts don’t occur in a single day. We wanted a 10-year plan the place clients who wished the legacy resolution may nonetheless get it, whereas we additionally constructed within the fashionable, future resolution of a digital actuator that they might management.
“As soon as we reached a sure stage of adoption, we moved to the ultimate stage: merchandise particularly designed for digital management. These don’t carry the luggage of mechanical units, which add value and compromise designs.
“For many of our merchandise we’re already at this final stage so we not design future merchandise with legacy interfaces. If clients nonetheless want a mechanical interface, they’ll purchase the older era, which we nonetheless produce. They’ve completely different efficiency and security ranges, however they continue to be accessible.
“Our focus now’s on designing hydraulics with digital interfaces as a result of we all know the long run lies in electro-hydraulic methods. In truth, 100% of our new product growth packages are focused in that path.”
New methods to maneuver
Just lately Volvo Development Tools has used electro-hydraulic structure in its new Impartial Metering Valve Know-how (IMVT), accessible on 50-tonne EC550 and EC530 excavators.
“IMVT marks a departure from the standard mechanically coupled hydraulic methods and introduces clever digital management with quite a few variables,” says Sejong Ko, Volvo CE’s product supervisor for giant excavators. “The outcomes are as much as 25% improved gasoline effectivity and higher operator management.”
IMVT allows further options utilizing a closed-centre valve-control system, which in contrast to conventional open-centre methods, can cease or decrease hydraulic stream by way of the principle management valve when there’s no demand for a hydraulic actuator. This considerably reduces gasoline consumption and eliminates the necessity for an eco mode.
It additionally makes use of unbiased cylinder management, sensing and controlling all sides of a cylinder’s chamber independently, with out utilizing hydraulic spools and pilot strains. This ends in extra exact management of the excavator’s actions.
“IMVT replaces conventional spools with poppet and electro-hydraulic valves in the principle management valve (MCV), decreasing stress losses and optimizing valve management primarily based on load situations,” says Sejong Ko. “This results in quicker cycle instances, improved regeneration and diminished stream loss, with evaluation displaying a 20% enhance in productiveness.”
Hydraulic hybridisation
Regardless of potential power restoration ranges in off-highway automobile hydraulics being comparatively small when in comparison with the well-established hybrid methods utilized in hydraulic braking for automotive; in recent times, tighter emissions targets and rising power prices have supplied better demand, notably in excavators, which generate essentially the most carbon emissions of any automobile class within the off-highway world.
“However it’s not a trivial factor to do in hydraulics,” says Herrin. “You need to add extra complexity with extra parts and circuits, and to do it, you completely need to have an digital system.”
The worth proposition for that extra complexity has traditionally been pretty poor, with OEMs having to make the commerce off on complexity versus profit. However the rising push for sustainability is driving innovation. “We did a refresh on our industrial pump product line,” says Herrin. “It was designed 30 years in the past and is now being refreshed and up to date to fashionable specs. The spec for this new pump was, actually, to have the ability to get well power in addition to pump power.”
In 2020 Volvo CE first introduced that it had developed a Hybrid system for its excavators which recovers power straight from hydraulic methods, not primarily through the use of pumps, however as a substitute by the use of a hydraulic accumulator. It captures and reuses hydraulic energy, leading to as much as 17% enhance in gasoline effectivity and 15% discount in CO2 emissions. Just lately the OEM introduced this Hybrid expertise could be added to its massive EC400 and EC500 40 and 50 tonne machines, having already been accessible on 4 smaller autos within the vary – the EC380E Hybrid, EC350E Hybrid, EC300E Hybrid and EC250E Hybrid excavators.
“We do it by mounting a hydraulic accumulator simply behind the growth, and because the growth goes down, the high- stress oil that you simply use to retard the growth dropping goes into the accumulator as a substitute of being routed to the tank,” says Dr Ray Gallant of Volvo CE. “This provides the accumulator a high-pressure cost that’s then routed by way of help motors and put again into the cylinders on the upswing. Your entire course of is managed routinely – the operator isn’t required to do something. He merely sees a small image on the sprint that tells him when his accumulator is charging and discharging.”
Volvo CE’s hybrid hydraulic expertise doesn’t generate electrical energy or require batteries for storing it. “It requires minimal parts – there are not any electronics to program and no management methods apart from system monitoring,” says Gallant. “Upkeep can also be easy because the system is a basically a mix of hydraulic stream and valves.
There are different options which can be extra reliant on pumps being able to working in a bi-directional method. For instance, pump- managed actuators handle movement primarily by way of velocity and/or displacement management of particular person pumps, making the pump a central element within the system. It’s on this area that promising applied sciences embody Danfoss’s Digital Displacement pumps, floating cup expertise, and high-speed pumps. “We anticipate these options to succeed in the market over time,” says Hongsuk Kim, head of excavator medium and hydraulic platform at Volvo CE. “Notably for electrically powered machines, the place bi-directional speed- managed pumps can get well power again to {the electrical} energy system.”
Sooner or later extra steps might be taken with hydraulic power restoration applied sciences. For instance, dead-weight compensation methods. “These use extra cylinders and hydraulic accumulators working in parallel with the principle hydraulic movement management system and will provide benefits in particular purposes,” says Hongsuk Kim. “These methods are comparatively easy and mustn’t face vital hurdles to reaching market readiness.
“A extra superior resolution is the widespread stress rail structure, which makes use of one or a number of semi- fixed stress ranges mixed with hydraulic accumulators. On this setup, pressure and velocity are managed by way of hydraulic transformers and multi-chamber cylinders, which characterize state-of-the-art expertise. Even these superior methods require a number of independently managed valves, very similar to IMVT, demonstrating that our growth efforts in IMVT are paving the way in which for future improvements in hydraulic power restoration.”
“In the end electrified linear actuation will remove hydraulic fluid on machines”
Electromechanical actuators
A variety of prototype autos, in addition to Bobcat’s manufacturing all-electric T7X and S7X compact observe loaders and skid steers, have executed away with conventional hydraulics altogether and changed them with electromechanical linear actuators. Herrin sees continued evolution within the discipline. He notes that Danfoss Energy Options is investing in electromechanical actuators as
a complementary product line to their electrification portfolio. Whereas the use instances for this expertise are at present modest, Herrin anticipates that, “as electrification takes a much bigger maintain in off-highway tools, finally electrified linear actuation will remove hydraulic fluid on machines. Rotary actuators (wheel drives, work features) shall be first, steering subsequent, and linear actuators final.
Volvo CE is already making use of electric-motor pushed actuators in a few of its excavators, and studies optimistic buyer suggestions. “It is very important notice that electrical motor-driven actuators can work along with hydraulics as an intermediate energy transmission medium or, in some instances, with out hydraulics altogether,” says Hongsuk Kim. “Nonetheless, each hydraulic and electrical methods have their respective benefits and limitations. We don’t imagine that one expertise will absolutely dominate throughout all purposes.
At Volvo, we aren’t dedicated to phasing out hydraulics however as a substitute concentrate on adopting the expertise that most closely fits our clients’ wants. We acknowledge the challenges related to electro-mechanical drives, particularly for linear movement purposes. These challenges are much less pronounced for rotary drives, making them extra possible to interchange hydraulics now.”
Enabling automation
One of many key benefits of electro- hydraulics is that’s has enabled machine management – whether or not that be semi-autonomous driver help methods or full automation, having the ability to management actions by way of digital methods is a vital enabler.
“One in all our flagship innovation programmes is round autonomy,” says Herrin. “There are only a few use instances for absolutely autonomous machines proper now, however there’s a complete lot for semi-autonomous, which imply operators could be much less expert, as a result of the machine can function itself in cycles which can be repeatable.”
This pattern in the direction of automation is driving the necessity for extra superior applied sciences. As Herrin factors out, “While you get into that area, AI and machine studying are required. It’s the core digital algorithm expertise that permits automation.”
This text first appeared within the October subject of iVT
