Electro-hydraulics are enhancing off-highway automobile performance and effectivity, enabling machine management and offering the constructing blocks for energy-recovery programs. Trade specialists give perception into the evolution of this expertise and predict future developments
Over the previous three many years off-highway automobile designers have moved away from constructing machines which have hydraulics managed through mechanical programs and hydraulic pilot traces to utilising digital management – electro-hydraulics. However, whereas such programs are effectively established, the total prospects of this structure are nonetheless being explored.
Despite the fact that 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, slightly through a gradual evolution.
That is borne out by part specs. Danfoss, for instance, after years of designing parts that could possibly be used with both mechanical or digital interfaces, has now fully transitioned its new parts to electro-hydraulics.
“The interface of our hydraulic merchandise has gone via three phases of evolution,” says Jeff Herrin, senior vice chairman of R&D at Danfoss Energy Options. “The primary stage, relationship again a few years, concerned hydraulic and mechanical interfaces. For instance, a hydraulic pump managed by a lever that an operator might use to create the specified stream.
“The second stage launched designs with each lever entry and digital management. This transitional part was mandatory as a result of trade shifts don’t occur in a single day. We wanted a 10-year plan the place prospects who needed the legacy answer might nonetheless get it, whereas we additionally constructed within the fashionable, future answer of a digital actuator that they might management.
“As soon as we reached a sure degree 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 prospects nonetheless want a mechanical interface, they’ll purchase the older technology, which we nonetheless produce. They’ve totally different efficiency and security ranges, however they continue to be accessible.
“Our focus now could be on designing hydraulics with digital interfaces as a result of we all know the long run lies in electro-hydraulic programs. In truth, 100% of our new product growth applications are focused in that path.”
New methods to maneuver
Not too long ago Volvo Development Gear has used electro-hydraulic structure in its new Unbiased Metering Valve Know-how (IMVT), accessible on 50-tonne EC550 and EC530 excavators.
“IMVT marks a departure from the standard mechanically coupled hydraulic programs and introduces clever digital management with quite a few variables,” says Sejong Ko, Volvo CE’s product supervisor for big excavators. “The outcomes are as much as 25% improved gas effectivity and higher operator management.”
IMVT allows further options utilizing a closed-centre valve-control system, which in contrast to conventional open-centre programs, can cease or decrease hydraulic stream via the principle management valve when there’s no demand for a hydraulic actuator. This considerably reduces gas consumption and eliminates the necessity for an eco mode.
It additionally makes use of impartial cylinder management, sensing and controlling all sides of a cylinder’s chamber independently, with out utilizing hydraulic spools and pilot traces. 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 strain losses and optimizing valve management based mostly on load situations,” says Sejong Ko. “This results in quicker cycle occasions, improved regeneration and lowered stream loss, with evaluation displaying a 20% increase 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 programs utilized in hydraulic braking for automotive; lately, tighter emissions targets and rising power prices have offered better demand, significantly 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. “It’s a must to add extra complexity with further parts and circuits, and to do it, you completely must have an digital system.”
The worth proposition for that further 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, in truth, 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 instantly from hydraulic programs, not primarily by utilizing pumps, however as an alternative via a hydraulic accumulator. It captures and reuses hydraulic energy, leading to as much as 17% improve in gas effectivity and 15% discount in CO2 emissions. Not too long ago the OEM introduced this Hybrid expertise can 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 increase, and because the increase goes down, the high- strain oil that you just use to retard the increase dropping goes into the accumulator as an alternative 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 via help motors and put again into the cylinders on the upswing. The whole course of is managed robotically – 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 aren’t any electronics to program and no management programs 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 are extra reliant on pumps being able to working in a bi-directional method. For instance, pump- managed actuators handle movement primarily via velocity and/or displacement management of particular person pumps, making the pump a central part 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. “Significantly for electrically powered machines, the place bi-directional speed- managed pumps can get well power again to {the electrical} energy system.”
Sooner or later further steps could possibly be taken with hydraulic power restoration applied sciences. For instance, dead-weight compensation programs. “These use further cylinders and hydraulic accumulators working in parallel with the principle hydraulic movement management system and will provide benefits in particular functions,” says Hongsuk Kim. “These programs are comparatively easy and shouldn’t face important hurdles to reaching market readiness.
“A extra superior answer is the frequent strain rail structure, which makes use of one or a number of semi- fixed strain ranges mixed with hydraulic accumulators. On this setup, pressure and velocity are managed via hydraulic transformers and multi-chamber cylinders, which signify state-of-the-art expertise. Even these superior programs 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.”
“Finally electrified linear actuation will remove hydraulic fluid on machines”
Electromechanical actuators
Plenty of prototype autos, in addition to Bobcat’s manufacturing all-electric T7X and S7X compact observe loaders and skid steers, have finished away with conventional hydraulics altogether and changed them with electromechanical linear actuators. Herrin sees continued evolution within the subject. 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, in the end electrified linear actuation will remove hydraulic fluid on machines. Rotary actuators (wheel drives, work features) will probably 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 reviews constructive buyer suggestions. “You will need to observe 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. “Nevertheless, each hydraulic and electrical programs have their respective benefits and limitations. We don’t consider that one expertise will totally dominate throughout all functions.
At Volvo, we’re not dedicated to phasing out hydraulics however as an alternative deal with adopting the expertise that most accurately fits our prospects’ wants. We acknowledge the challenges related to electro-mechanical drives, particularly for linear movement functions. These challenges are much less pronounced for rotary drives, making them extra possible to switch 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 programs or full automation, with the ability to management actions through digital programs is a crucial enabler.
“Considered one of our flagship innovation programmes is round autonomy,” says Herrin. “There are only a few use instances for totally autonomous machines proper now, however there’s an entire lot for semi-autonomous, which imply operators might be much less expert, as a result of the machine can function itself in cycles which are repeatable.”
This development in the direction of automation is driving the necessity for extra superior applied sciences. As Herrin factors out, “Once you get into that house, AI and machine studying are required. It’s the core digital algorithm expertise that allows automation.”
This text first appeared within the October concern of iVT
