Hydraulic steering systems have long dominated the industrial utility vehicle market because of their familiarity both to vehicle designers and operators.
Recent trends in the industry position hydraulic steering as less advantageous for many industrial utility vehicles. Hydraulic steering systems require a motor, pump, valves, hoses and fittings. Utility vehicles that utilize hydraulic drives for other functions may or may not have a hydraulic pump with enough capacity to accommodate the steering system.
Advantages of electronic steer-by-wire systems.
Another reason for the trend away from hydraulic steering is substantial performance improvements that have been made in electric motors in recently years. The power density of electric motors has substantially increased because of advances in magnetic materials, lead/ball screw efficiency, construction, manufacturing techniques and electronics. Today’s electric motors can deliver substantially more power while maintaining high levels of efficiency. Steer-by-wire systems have also benefited by the improved reliability as published in Industrial Utility Vehicle & Mobile Equipment of all electronic and electrical products. Electronic steering systems provide nearly maintenance free operation and are thus much less prone to fail due to lack of maintenance.Nilfisk-Advance, Inc. is the world’s largest manufacturer of professional cleaning equipment. Nilfisk-Advance engineers made the decision to upgrade the steering system to electronic steer-by-wire in order to improve steering performance, reduce power consumption and make it possible to add additional features. Nilfisk-Advance, Inc. engineers adjusted the torque feedback to simulate the hydraulic steering systems that many customers are used to. They configured the unit to provide fewer lock-to-lock steering wheel turns than are required by most hydraulic systems to reduce the amount of operator effort. They also decreased the level of steering sensitivity when the vehicle is going straight in order to make it easier for the operator to keep the vehicle on a straight path.
Nilfisk-Advance, Inc. ran the Danaher integrated electronic steer-by-wire systems through thousands of cycles on life test fixtures. The units performed perfectly in these tests which simulated the service life of a machine. The integrated steer-by-wire system replaced the old torque-assist unit, a shaft and a u-joint while providing a cost reduction of 25%, said Steve Strand, Continuation Engineer for Nilfisk-Advance. The ability to fit within the envelope provided by the existing console saved thousands in tooling costs. Feedback from customers who have driven the prototypes has been very favorable, and the scrubbersweepers with the new steering system will soon enter production.
As published in Industrial Utility Vehicle & Mobile Equipment Jan/Feb 2009 Volume 21 – Issue 13 (repost)