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1、Electronic power steering systemWhatitisElectrically steeri ng uses an motor to drive either steeri nghydraulicthe steeri ng lin kage The power steeri ng therefore in depe ndentofspeed, resulting in en ergy sav in gs. How it works :Conven tio nalEPS system layoutEPS mode switchpowered electric the p
2、ower pumpor directly. fun cti on isengine sig nifica ntpowersteering systemsusean engineaccessory belt to drive the pump, providing pressurized fluid that operates a piston in the power steeri ng gear or actuator to assist the driver.In electro-hydraulic steering, one electrically powered steering c
3、oncept uses a high efficiency pump driven by an electric motor. Pump speed is regulated by an electric controller to vary pump pressure and flow, providing steering efforts tailored for different driving situations. The pump can be run at low speed or shut off to provide energy savings during straig
4、ht ahead driving (which is most of the time in most world markets.Direct electric steering uses an electric motor attached to the steering rackvia a gear mechanism (no pump or fluid. A variety of motor types and gear drives ispossible. A microprocessor con trols steeri ng dyn amics and driver effort
5、. In puts in clude vehicle speed and steeri ng, wheel torque, an gular positi on and tur ning rate.Working In Detail:A steeri ng sen sor is located on the in put shaft where it en ters the gearb hous ing. The steeri ng sen sor is actually two sen sorsi n one: a torque sen sor that conv erts steeri n
6、g torque in put and its direct ion into voltage sig nals, and a rotati on sen sor that conv erts the rotati on speed and directi on into voltage sig nals. An in terface circuit that shares the same hous ing con verts the sig nals from the torquesensorand rotation sensor into signals the control elec
7、tronics can process.In puts from the steeri ng sen sor are digested by a microprocessor con trol unit that also mon itors in put from the vehicles speed sen sor. The sen sor in puts are the n compared to determ ine how much power assist is required accord ing to a preprogrammed force map in the cont
8、rol units memory. The control unit then sends out the appropriate comma nd to the power un it which the n supplies the electric motor with curre nt. The motor pushes the rack to the right or left depe nding on which way the voltage flows(revers ing the curre nt reverses the directi on the motor spin
9、s. In creas ing the curre nt to the motor in creases the amount of power assist.The system has three operating modes: a normal control mode in which left or right power assist is provided in resp onse to in put from the steeri ng torque and rotatio n sen sors in puts。 a return con trol mode which is
10、 used to assist steeri ng return after completing a turn。 and a damper control mode that changeswith vehicle speed to improve road feel and dampe n kickback.If the steering wheel is turned and held in the full-lock position and steering assist reaches a maximum, the con trol unit reduces curre nt to
11、 the electric motor to preve nt an overload situation that might damage the motor. The control unit is also designed to protect the motor against voltage surges from a faulty alternatoror charging problem.The electronic steering control unit is capable of self-diagnosing faults by mon itori ng the s
12、ystems in puts and outputs, and the driv ing curre nt of the electric motor. If a problem occurs, the control unit turns the system off by actuating a failsafe relay in the power unit. This eliminates all power assist, causing the system to revert back to manual steering. A dash EPS warning light is
13、 also illuminated to alert the driver. To diagnose the problem, a technician jumps the terminals on the service check conn ector and reads out the trouble codes.click here to see a biggerElectric power steeri ng systems promise weight reduct ion, fuel sav ings and package flexibility, at no cost pen
14、alty.Europes high fuel prices and smaller vehicles make a fertile testbed for electric steeri ng, a tech no logy that promises automakers weight sav ings and fuel economy gains. And in a short time, electric steering will make it to the U.S., too. Its just just a matter of time, says Aly Badawy, dir
15、ector of research and developme nt for Delphi Saginaw Steering Systems in Saginaw, Mich. The issue was cost and thats behind us now. By 2002 here in the U.S. the cost of electric power steering will absolutely be a wash over hydraulic.Today, electric and hybrid-powered vehicles (EV , in clud ing Toy
16、otas Prius and GMs EV-1, are the perfect domain for electric steering. But by 2018, a TRW Inc. internal study estimates that one out of every three cars produced in the world will be equipped with some form of electrically-assisted steering. The Cleveland-based supplier claims its new steeri ng systems could improve fuel economy by up to 2 mpg, while enhancing han dli ng. There are true bottom-li ne be
