Maintenance/Management: Intelligent hydraulics
| June 12, 2007 |
In just the past few years, the progression from electro-hydraulic control to electronic control of hydraulic systems has given engineers almost unlimited potential to re-write the rules of how machines and their component subsystems work together. And smarter hydraulics combined with steady improvements in the mechanical elements of hydraulic pumps, motors, hoses and connections are leading to significant increases in the performance, fuel economy and maintainability of your new equipment.
“Today, instead of just reading the joystick and sending a signal to the valve with solid-state circuitry, you can take a bunch of input signals and do all sorts of interlock logic and safety logic and movement coordination logic,” says Mike Kern, global electronics business unit manager at Parker Hannifin’s hydraulics group. “By programming in the logic, you can drive the pump or the motor in a more sophisticated fashion.”
“There are a million different interlocks and dependencies, and once it all comes together it allows you to start adding value,” says Art Donaldson, systems engineering manager, mobile systems, for Parker Hannifin’s hydraulics group. “The information floating around a vehicle today, even compared to five years ago, is just amazing. As all this starts to tie together we’re getting close to total machine control, which is where all this has to go.”
What you will see more of in the future is communication across machine systems – for instance, the engine and hydraulics communicating with each other to achieve operational efficiency, says Brendan Casey, founder of www.HydraulicSupermarket.com and author of two books on the maintenance and repair of hydraulic equipment.
Casey cites an example of a diesel engine governed at 1,800 rpm, but with a maximum permissible rpm of 2,100, driving a hydrostatic transmission. The transmission goes into braking mode and a sensor detects a drop in boost pressure. The maintenance of adequate boost pressure is essential to prevent damage to the transmission, so the onboard electronics increase engine rpm above the continuous rating (and at the same time reduce the transmission pump’s displacement as required to maintain braking). The increase in engine speed results in more flow being available from the boost pump to maintain charge pressure and therefore prevent possible damage to the transmission as a result of cavitation. When the transmission is no longer in braking mode and charge pressure has stabilized, engine speed would be returned to the normal level – all without the operator lifting a finger, Casey says.
Talking to the sky
One of Parker Hannifin’s more sophisticated applications of intelligent hydraulics interfacing with wireless technology and satellite modem hookups is on a gantry crane, Donaldson says. “I was with the OEM engineer and he told me how he had dialed into the machine and was making some routine maintenance checks – but the machine was in Memphis and the engineer was in Mississippi,” he says. The engineer noticed some problems and telephoned the on-site supervisor, who drove out to make the repair before the operator even knew there was a problem.
Wireless alerts and diagnostics of hydraulic systems are currently limited to more expensive types of equipment, but they have widespread appeal. Parker has such systems on some forestry equipment, big cranes, refuse trucks and street sweepers (mostly in Europe) and construction waste grinders, Kern says.
The technology hasn’t migrated down to the average backhoe yet, but it probably will, says Donaldson. “We can all remember a time when cell phones were special,” he says. “Once the technology proves itself and the cellular carriers decide that there is a business there and they develop plans for this type of interface, then there will be more and more of it. The benefit is there.”
Program anything you want
With programmable software calling the shots in these new systems, Parker is able to offer its OEM customers the ability to design unique and highly customizable solutions. “Our IQAN (www.IQAN.com) system is a set of tools that allows the machine designer to take the standard hardware and software package and program his machine to do whatever he needs it to do, without the need for us or a trained programmer to step in and do it for him,” Kern says.
The software tools not only allow the OEM machine designers to create custom applications, but will also continue to play an increasingly important role in maintenance and shop diagnostics.
With increasing complexity, especially at the electronics/hydraulics interface, the need for a methodical, informed approach to troubleshooting will be imperative, Casey says. “The ‘duck hunter’ or shot-in-the-dark approach to troubleshooting will be even less effective than it is now,” he says. “We are seeing this happening, but all too often as an optional extra or accessory. As with all other technology the real cost will decrease exponentially over time. The early adopters, the sophisticated machine buyer or owner, will spend the money now in order to have access to this information. Those who don’t may find that their life-of-machine service and maintenance costs will be higher.”
Diagnostics information can be downloaded onto a laptop computer and analyzed in the shop. But depending on how the OEM wants to present the information to the end user, the machine’s in-cab display can also be programmed to deliver all the information there.
“On this gantry crane, the OEM spent a lot of time on diagnostic tools and screens that make it very intuitive,” Donaldson says. “They have cut the maintenance and operator training cycle of their onsite crane delivery to one-third of what it used to be. So much of what they used to do was walking people through relay panels and relay logic. Now it’s done automatically.”
Programmable systems also allow the dashboard to change depending on what the operator is doing or needs to see, Kern says. “They used to put up a rack of gauges and it was up to the operator to look in the right place.” he says. “We’ve been able to replace that with just a small display because we can change that display based on what the operator is doing – roading, digging, maintenance – you can change the screen to reflect that specific application.”
As OEMs reconfigure engines to meet Tier 3 and Tier 4 emissions, the electronics are increasingly being asked to convert all the available horsepower into real work, Donaldson says. “So every ounce of usable horsepower needs to be 100 percent used,” he says. “Things like energy recovery, total horsepower management and total machine control are the trends of the future. Look at a wheel loader. Because of energy recovery and total horsepower management it becomes more important to have a central processor controlling all aspects of the machine.” The goal is to operate the engine consistently in its sweet spot without having to rev up or rev down to meet demand.
In a similar fashion to hybrid cars, intelligent hydraulics are also being tapped to recover braking energy from moving construction equipment. (The difference is that hybrid cars use brake energy to generate electricity.) “We have an energy recovery system on a refuse vehicle that debuted at Waste Expo this year,” Donaldson says. “The system goes from hydrostatic to direct drive when the operator exceeds a given speed – the computer makes the change automatically. We tried it with a wheel loader but we weren’t able to recover enough energy with just the bucket and boom. But if you go with hydraulic drive and stop with the hydraulic system, your drive can be totally managed. With a computer you can optimize the flow to each wheel; then you can save some energy.”
Just over the horizon, but getting closer, are hydraulic systems with intelligent valves. “Eventually you’ll buy a generic valve and then buy a tuning package that goes with it,” Donaldson says. The hardware will be off the shelf, but the tuning package or software will enable the engineers to give that valve what Donaldson calls personality. “Two valves with identical parts numbers can act totally different once they have the personality programmed into them,” he says.
The only thing preventing further development of these smart valves is the speed of the currently available microprocessors, Kern says. The dialogue between the engine, transmission and hydraulic systems contains huge amounts of information and requires enormous processing power to get to the level where it can influence the position and reaction of the valves. “We’re not there now,” Donaldson says. “But it is the next logical step.”
Don’t ignore the basics
The technology behind today’s cutting-edge hydraulics may be out of this world, but you still have to follow some down-to-earth maintenance practices if you want to get the most life and best performance out of your systems. Good service and maintenance is even more important with today’s high-performance systems, says Brendan Casey, and he recommends the following six-point routine:
- Maintain fluid temperature and viscosity within optimum limits
- Maintain fluid cleanliness
- Maintain hydraulic system settings to machine specifications
- Schedule component change-outs before they fail
- Develop machine-specific commissioning procedures
- Conduct failure analysis.