Electronics and software are teaming up with hydraulics to lower system costs, boost performance and add features, creating a transition to electronic controls for telehandler systems. Enhancing hydraulic systems with electronic controllers and joysticks is adding intelligence and flexibility to these systems, allowing such features as XY path control and customer-specific performance options.
“The industry has done a good job keeping the component costs down but to drive the overall system cost lower, there is a need to look at the whole system and move to electronics to make further gains,” says Jim Eisenmenger, senior applications engineer for Sauer-Danfoss. “Instead of looking at the pumps, valves or joysticks by themselves, OEMs are looking at all of these components, machine variation costs, installation costs and the cost for the service organization to understand and maintain systems in the field.”
Telehandlers, also known as rough terrain forklifts, are four-wheel drive, tractor-like machines with an extendable boom and a set of forks to lift pallets and place loads into high locations. Some machines can lift and place loads up to 17m in the air and the capacities of systems range over 5,400 kg.
In Europe, electronic control systems are already common because owner-operators have justified the extra expense by utilizing the value of electronic controls. In the U.S., the main buyers are rental companies and the purchase cost has historically been more important than adding more performance.
What has changed is that the electronics and software required for electronic control have become more robust and simpler to use. In the past, customers needed to know a programming language and how to design or specify hardware, but now there are graphical-type programming environments and configurable hardware such as the Sauer-Danfoss PLUS+1™ control system.
Sauer-Danfoss expanded its line of PLUS+1™ controllers to provide communication to the joystick, sensors and valves in the system. The system allows OEMs to easily configure control hardware and program software for their machines instead of relying on outside assistance to design and develop hardware and software. Plus, there has been a reduction in the cost of the sensors required on the machines. “Now the sensors, joysticks and the controllers themselves are getting closer to where they are competitive with individual hydraulic components,” says Eisenmenger.
While the goal is both improvements in performance and reduction in costs, a main benefit is machine variation defined in software rather than hardware. Machine options and performance levels can be implemented via software and/or sensors, with minimal variation in hydraulic hardware.
One example of this is lowering cycle times by using greater hydraulic flow from the pump to move the cylinders faster. Electronic control enables this by preventing the engine from stalling when the operator commands more pressure and flow than the engine can support. The controls also can dampen the fast motion with software ramping of operator commands and near end-of-stroke conditions.
Another example is XY path control where the operator can direct the load to move vertically or horizontally with a single joystick command. In the past, if the user wanted to move a load up vertically, the operator had to boom up and telescope out. “But users needed to do both operations at once or sequentially with stops to keep the load moving in the right direction,” says Eisenmenger. “You can still do that, but now you can flip a switch and change the effect of the joystick motion, so that the load goes either straight up and down or straight in and out, without the operator needing to make the precise adjustments to keep the load moving smoothly in the desired direction.”
The system is making it easier for inexperienced operators to operate the machinery. Someone who has never run a machine can come closer to experienced operators in terms of picking up loads and setting them in high, hard to get to places. By using advanced functions such as XY path control, they can more easily move loads straight up, straight out and easily set them in place.
The other area of performance improvement is that OEMs can electronically tune a machine to a customer's needs. One rental company may want a well-damped, very smooth system for inexperienced operators that will produce smooth and well-controlled motion. Another customer might want a higher-performance machine that reacts more quickly to joystick input. The machine can be tuned via software to achieve a different “look and feel.”
There are also installation benefits compared to hydraulic pilot control. Compared to existing machines, there is a reduction in the hoses, connections and fittings required on the machine; and electronic control makes for a clean installation.
Some barriers to a transition to electronic control have been sensor cost and perceived complexity. Even though sensor costs have dropped, there are still cost concerns with some types of sensors. Service organizations have been trained to fix mechanical or hydraulic problems and their perception is the electronics are hard to work on and complicated. Instead of looking for a mechanical or hydraulic problem, they may need to plug in an analyzer and look for an error code. It may actually be easier to do maintenance but there is a mental barrier that will need to be overcome for the service organizations to fully embrace the electronic controls.
The previous architecture had a hydraulically controlled joystick which would meter a pressure signal to move the valves; now there is an electrical signal to a solenoid to electrically move the valve. The older system did not require a controller but the downside was hydraulic hoses with associated noise, potential leaks and heat coming into the cab. The newer architecture provides intelligence in the system by adding the electronic controller and joystick.
“This new approach is optimizing the hydraulic system with more sophisticated controls. The fundamentals of the machine, in terms of lifting capacity, are unchanged but there are more elegant controls plus features such as customized performance and XY path control,” says Eisenmenger. “The best way to move the boom up and down is still with a hydraulic cylinder and no other solution can touch that in terms of cost and performance. Now we are controlling that capability with more intelligence.”
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