Who’s Afraid Of Electric Power Steering? | The Truth About Cars

9 Июн 2015 | Author: | No comments yet »
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Who’s Afraid Of Electric Steering?

Here’s a challenge: try to a review of the Toyota Corolla doesn’t bemoan its numb Now try with a Chevy Cobalt. Or a or Vibe, Or Rav4, or Equinox. do these vehicles have in Column-mounted electric power systems from JTEKT. a spin-off supplier which has a brisk business in these steering systems. And though the press has been bashing power assist steering or EPS) for its deleterious effect on the explosive growth in these may put more at risk than enthusiast-approved steering feel.

anesthetization of steering systems has not place because manufacturers the proliferation of words like and “overboosted” in reviews of their EPS offers improved efficiency due to its of parasitic losses, and is cheaper to than traditional hydraulic This killer combination manufacturers a combination of improvements have proven near-impossible to resulting in the broad proliferation of EPS And if reduced steering feel the only casualty of the switch, it be a tradeoff that any manufacturer be willing to run.

But as EPS has exploded the market, a number of troubling has plagued the system. The National Traffic Safety Administration has investigations into the Chevy and Toyota Corolla. which the column-mounted JTEKT EPS system. which moved to an EPS system for the model year has been by an accelerating number of failures the switch, while the Corolla centers on Corollas built the 2009 model-year switch to

In both of these vehicles, down exact steering is proving to be difficult. Many of the complaints are related to sudden particularly at speeds above 40 The Cobalt, meanwhile, seems to complete EPS failure, causing loss of steering and/or the for drastically increased steering Again, the inability to stay in a set lane is being targeted as the dangerous symptom of the possible

These symptoms fit conveniently a category that an early (by Amit Rohidas Bendale of the Institute of Technology, publication unknown) on EPAS technology at college-seminars.com calls “auto a term the paper asserts crept into the lexicon as an to the development of EPAS system.” attempts to explain this in his paper’s section on the disadvantages of EPS

To-date, technical and product concerns have precluded the of such systems in the U.S. through it is expected that application may be expected in the near-to-mid mix of future vehicles. Such design have yet to prove sufficiently reliable and safe to dangerous “auto steer” “Auto steer” has crept the lexicon as an adjunct to the development of system. As the name implies steer” denotes an uncontrolled event neither commanded nor by the vehicle’s driver due to catastrophic in the electron hardware or software. In these systems are control systems, similar in function to control servo systems, and have multiple redundancy. these new EPAS systems are to have multiple redundancy. design and broad application the automotive industry have and will continue to be, subject to pressure more extreme found in the aircraft industry. For one obvious safety related has been universally deleted such system specifications: a for physically disengaging the reduction box and drive motor assist from the host steering in the event of system failure. means that a driver an EPAS system failure have to exert additional to “back drive” (i.e. over ride) the systems gear box and drive motor assembly while attempting to control of the vehicle in the absence of power steering assist.

Already, the parallels between EPS issues (which are admittedly but reflect NHTSA complaints) and gas pedal issues are plain to The first is the issue of economic towards cost-cutting, which to the reduction of fail-safes and redundancy. parallel is the fragility of by-wire systems: in Toyota gas pedals, amounts of moisture was enough to the pedals to stick. In the case of EPS there’s evidence to suggest even cell phone could cause system This is not to say that these two are directly comparable, but both indicate that earlier systems offer few clues as to malfunctions of electronic systems. the most important parallel Toyota’s “unintended acceleration” and EPS veering” is the complicated dynamic the driver and the system at the moment of or failure. Bendale continues:

Unlike the manual system above, PAS with the presence of steering force to that solely by the operator introduces engineering challenges in terms of the desired steering linearity previously. In fact, with to steering linearity, a poorly power steering assist may have almost no relationship the hand wheel torque by the operator and the actual required force imposed by the wheel or There no longer may exist the consistent and predictable relationship the “input and outputs” to facilitate reference driving.” Restated, the sense of the driver to maintain control, and the magnitude and modulation of the force may not bear a direct, relationship to the required “output” delivered by the steering system. reference steering is simply not with such vehicles. their drivers must engage in “visual reference to maintain directional control. The is that such vehicles are tiring to drive for any length of or distance. Further their are constrained to continuously look at the If such driver should away even momentarily to check a rearview mirror or a in the car), he or she has minimal tactile as to the actual position of the vehicle that period of time. is dangerous because, depending the road topography and condition, the may have moved transversely in amount relative to where the thought his or her vehicle was positioned. can and often does lead to trouble.

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This helps explain the accounts of unintended veering, as the to handle sudden changes in response varies greatly driver to driver. Like acceleration, this makes the of narrowing down the primary of EPS failure or malfunction impossible on recorded accounts alone.

importantly, this helps the link between numb, and uncommunicative steering and safety. At speeds, any failure or malfunction be registered and reacted to by touch feedback) before the brain be able to register visual that vehicle control has compromised. Because of EPS’s in tactile feedback, and consistency wheel and steering wheel that all-important emergency feedback would be more for even a well-trained driver to making a crash more even if the unassisted steering were still functioning (as has reported in certain Cobalt

This is clearly an issue companies like JTEKT known about, as a 2008 on EPS [PDF ] by a JTEKT engineer that making EPS feel the hydraulic systems the buying is used to has been a major Another paper from the Engineering Journal [PDF ] that on higher-power versions of EPS,

sensitivity to such inputs as flutter and brake has become higher. J-ISM EPS assist control algorithm] has a suppression system that can inverse input vibration as differentiation value, and by providing in the direction of canceling the vibration, the is not transmitted to the steering wheel.

In tactile feedback is actively not only reducing the driver’s to respond to an emergency based on feel, but also further the EPS system with compensation in addition to pure steering

The point of all this is not to merely unwarranted fears about Improved efficiency and lower are the very definition of a successful system, and as long as EPS offers benefits, its use will continue to As this trend continues, it be important for safety watchdogs to pay attention to these systems. pressure to include redundancy, and extremely robust sensor suppliers will continue to cut the of these systems to remain with the growing number of that offer similar Just as importantly, these new systems require a new approach to that pays as much to driver reaction to malfunctions as to the themselves. Only in this way can we be that relatively minor don’t yield an epidemic of accidents and recalls.

Toyota Kluger I
Toyota Kluger I

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