Introduced late in 2005 with the four-wheel, counterbalanced lift truck clearly in mind, Electric Direct Drive Steering (DDS) technology is continuing to devote ongoing development resources to solving the detailed technical challenges of cracking into this new market.
"The four-wheel, counterbalanced market is new to 'fly-by-wire' technology and it is an ongoing discussion to persuade them to accept this concept," says Peter Taube, systems engineering manager for Danaher Motion's Electric Vehicle System Division.
Taube says the most significant development with the DDS systems has been the successful integration of the motor with the ballscrew. "A new, patented design inside the unit has enabled us to squeeze down the size of the actuator, so that it is almost the size of the hydraulic cylinder it is replacing."
One approach to championing new technology is creating a device that is similar to what it is replacing, in this case the hydraulic cylinder used today. With heavy investments in tooling and castings, persuading truck manufacturers to make significant design changes can be an uphill battle.
"We have put in an effort to make the actuator look as much like a hydraulic cylinder as possible," Taube says. He says hydraulic cylinders normally have an outer diameter of 75 mm, and the DDS solution has now been reduced to an O.D. of 109 mm. The size is not exactly equivalent to the hydraulic cylinder, but Taube says manufacturers have been able to squeeze the electric actuator into their existing vehicle designs, and a number of systems are currently being tested.
Danaher Motion is continuing to pursue electric technology improvements and use of the two-wire CAN bus network to improve vehicle steering systems. Plans include support for "eight o'clock steering" for both its rotary and linear steering systems in the future.
"Electric steering will also bring ergonomic improvements in these vehicles and the ability to place the steering device more easily into locations where it benefits operators the most," Taube says.
Fly-by-wire also gives the possibility to change the sensitivity on the fly. You can have a less sensitive system if the driver is driving straight forward at high speed, or more sensitive steering if the driver is turning at slow speed.
For more information on Danaher Motion's DDS system, go to http://rbi.ims.ca/4928-514.