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Four wheel steering system


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Four steering system is about the maneuvering of the wheel using all four wheel. Which allows the vehicle to take sharp turn at slow speed and decrease the rollover accident danger at higher speed.

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Four wheel steering system

  3. 3. INTODUCTION TO STEERING:- Steering is the collection of components, linkages, etc. which allow a vehicle (car, motorcycle, bicycle) to follow the desired course. An exception is the case of rail transport by which rail tracks combined together with railroad switches (and also known as 'points' in British English) provide the steering function. Requirement of steering- •It should multiply the turning effort applied on the steering wheel by the driver. •It should be to a certain degree irreversible so that the shocks of the road surface encountered by the wheels are not transmitted to the driver’s hand. •The mechanism should have self –rightening effect so that when the driver release the steering wheel after negotiating the turn , the wheel should try to achieve straight ahead position.
  4. 4. TYPES OF STEERING SYSYEM Front wheel steering. Rear wheel steering. Four wheel steering.
  5. 5. FOUR WHEEL STEERING:- • Four-wheel steering (or all wheel steering) is a system employed by some vehicles to improve steering response, increase vehicle stability while maneuvering at high speed, or to decrease turning radius at low speed. A 4- wheel steering system is superior to a 2- wheel steering system. It reduces the turning radius as well as the space required for turning. It also enables to change road lane while driving even at high speed. • At lower speeds, turning the rear wheels in the opposite direction to the front wheels results in a smaller turning radius and faster cornering responses. At high speeds, turning all four wheels in concert improves high-speed stability.
  6. 6. The Four Wheel steering system offers a 21% reduction in turning radius. So if a vehicle is capable of making a U-turn in a 25-foot space. It allows the driver to do it in about 20 feet. . A front wheel active steering function was added to Rear Active Steer adopted on the Fuga. By controlling the steering angle of all four wheels, this active steering system helps improve stability and response at high speed and helps reduce driver’s steering workload at low speed. To achieve precise vehicle • Vehicles move smoothly and are easy to drive both in the city and on winding roads. • Added stability means vehicles can be driven safely on expressways and when changing lanes. • Quick and responsive control system will allow gentle steering operation.
  7. 7. TURNING RADIUS:- The turning radius of a vehicle is the radius of the smallest circular turn (i.e. U-turn) that the vehicle is capable of making. it refers to the tightest turn a vehicle can make and is dependent on several factors. One obvious one is the width of the wheel base — that is, how far apart the front tires are. All other things being equal, a smaller wheel base can offer a tighter radius, while a large wheel base, such as those on large trucks, will have a larger radius, regardless of other factors.
  8. 8. 4-WS SYSTEM PARTS: - • Rack and pinion front steering, • hydraulically controlled • Rear-steering shaft • Vehicle speed sensors • Steering-phase control unit • Centering lock spring • Solenoid valve
  9. 9. At higher speeds, the rear wheels turn in the same direction of the front wheels to increase stability by preventing oversteer and fish tailing. And reduces the turning radius. AT HIGH SPEED:- 4-WS DRIVE AT DIFFERENT SPEED
  10. 10. At lower speeds, the rear wheel turn in the opposite direction from the front wheels. This will help in easy maneuverability of the vehicle during parking and taking a tight curve. The turning radius of a vehicle can be reduced by a minimum of 20% by having this mechanism, which is a significant benefit for bigger cars and trucks. AT LOW SPEED
  11. 11. ADVANTAGES OF 4WS • Speed can be varied Slow Medium Fast • Improved maneuverability
  12. 12. Better handling in tight corners Better parking Stability is increased 4WS 2WS
  13. 13. MODERN CARS WITH ACTIVE FOUR WHEEL STEERING: - •Acura RLX (P-AWS) •BMW 850CSi (only Euro spec models) •BMW 7-Series (2009 onward, part of sport package) •BMW 5-series (2011 onwards, Integral Active Steering option) •Toyota Camry / Vista JDM 1988–1999 (Optional) •Toyota Carina ED / Toyota Corona EXiV (world's first dual-mode switchable 2WS to 4WS) •Toyota Celica (option on 5th and 6th generation, 1990–1993 ST183 and 1994–1997 ST203) (Dual-mode, high and low speed) •Toyota Soarer (UZZ32)
  14. 14. CONCLUSION: - An innovative feature of this steering linkage design and its ability to drive all four (or two) wheels using a single steering actuator makes it more efficient than 2WS. Though it is expensive now but by producing it at big level cost may be decreased. Its successful implementation will allow for the development of a four-wheel, steered power base with maximum maneuverability, uncompromised static stability, front- and rear- wheel tracking, and optimum obstacle climbing capability.