DSPs Go Off-Highway to Control Hydraulics

Number Cruncher: Sauer-Danfoss' Plus 1 hardware modules use DSP to control complex functions for construction and agricultural equipment.

Off-highway equipment designers facing increasingly complex control problems may now have a new tool. Digital signal processors (DSPs), once reserved for the most intense number-crunching problems, are now migrating into agricultural and construction equipment.

New hardware modules from Sauer-Danfoss Inc. (Ames, IA) and Texas Instruments use DSP, instead of the more traditional microcontroller, to handle control of engines and transmissions, hydraulic valves, joysticks, input switches, brakes, and lights. Engineers say that DSP's time has come in such applications, mainly because the new breed of chips from makers such as Texas Instruments, have decided to include on-board CAN (controller area network) ports and Flash memory.

Compute power

"Traditionally, you would have found CAN ports and Flash only on microcontrollers," notes Dan Ricklefs, product portfolio manager for Sauer. "But when you can have all that on DSP, you take advantage of DSP's extra computing horsepower to run complex software algorithms."

Indeed, Sauer-Danfoss engineers say that Texas Instruments' F2812 device, one of two TI DSP being employed in Sauer's Plus 1 hardware modules, offers 150 MIPS (millions of instructions per second) of processing power, about 10 times that of the company's previous microcontroller-based systems.

The additional "compute power" enables designers to tackle more complex problems, such as creating a pulsewidth-modulated signal to control a hydraulic valve. As a result, the system can handle a bucket on a backhoe, or a three-point hitch on a tractor, while dealing with hydrostatic transmission controls or fuel efficiency issues on an engine.

"When you're managing the speed of an engine and the displacement of a hydrostatic pump, and at the same time optimizing for fuel efficiency and noise, you need some pretty sophisticated math-crunching capabilities," Ricklefs says.

Engineers say that the additional computing capability is becoming more important as cranes, backhoes, combines, and other machines adopt more sophisticated displays and user interfaces. Equally important, DSP could aid as more managers of heavy fleets try to track their equipment while it's being used.

Information management

"People who run heavy equipment fleets want to know where their equipment is, how long it's been out, and what its performance efficiencies are, Ricklefs says. In addition, fleet managers could use such capabilities for remote diagnostics of faults in heavy equipment.

Suppliers and OEMs are now considering putting Bluetooth nodes in electronics modules so that data can be downloaded to a remote location through a cellular link. But such capabilities require additional processing—one more reason why DSP is gaining appeal.

"There's a lot of interest in getting that information off the machine and back to the office," Ricklefs says. Some of those capabilities already exist on million-dollar mining machines. But the new DSP-based control modules may bring information management to lower-priced off-highway equipment such as tractors.

"We're now looking at ways of reducing the price point so that we can bring those kinds of technologies into more machines," Ricklefs says.