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Tuesday, January 22, 2008

New Toyota Aurion: In Depth (AU)

One of the safest cars on the road

Toyota's new Aurion has an impressive package of active safety features. Standard equipment includes Vehicle Stability Control (VSC), Traction Control (TRC) and Active Braking with intelligence (AB-i), incorporating ABS (anti-skid brakes), Brake Assist (BA) and Electronic Brakeforce Distribution (EBD). In addition, Aurion has a large footprint on the road for increased stability, a new chassis, revised suspension, and larger-diameter and wider tyres.

Aurion's new brake hardware includes 296mm by 28mm ventilated front disc rotors and 286mm by 10mm rear disc rotors. Aurion AT-X, Prodigy and Sportivo (SX6 and ZR6) have projector-type low beam headlamps. High-grade Presara has adaptive, self-levelling high-intensity discharge protector-type low-beam headlamps. Prodigy, Sportivo and Presara grades have front foglamps.

Toyota Brake Assist is designed to assist the driver in emergency braking, where the driver cannot apply the high pedal force required in time to minimise braking distance. Brake Assist interprets a quick, hard push of the brake pedal as emergency braking. It supplements the brake pressure applied if the driver has not pushed hard enough on the brake pedal. The Toyota system measures the speed and the force with which the pedal is pushed to determine whether the driver is attempting to brake rapidly. The system then applies additional hydraulic pressure to maximise braking performance. The timing and degree of braking assistance are designed to ensure the driver does not discern anything unusual in the braking operation. The system reduces the amount of assistance it provides when the driver intentionally eases the pressure on the pedal. The Toyota Brake Assist system may help drivers avoid potential incidents.

Electronic Brakeforce Distribution is a sophisticated electronic system designed to minimise stopping distances by maximising braking power to the wheels with the most grip. It replaces the conventional load-sensing and proportioning valve. The system functions electronically rather than mechanically, via an algorithm in the brake system's Electronic Control Unit (ECU). The EBD system in Aurion can adjust the fore/aft brake balance according to vehicle loading conditions and the right/left brake balance if the brakes are applied during cornering.

VSC as standard

Toyota Aurion has Vehicle Stability Control (VSC) and Traction Control (TRC) as standard equipment. It is the first built-in-Australia six-cylinder Toyota with these active safety features across the range.

VSC helps maintain vehicle stability during cornering, and TRC optimises traction when accelerating on slippery surfaces. VSC dampens strong understeer or oversteer to help maximise vehicle stability. The system includes a dedicated electronic control unit, which controls VSC, ABS and TRC. VSC utilises much of Aurion's brake control system hardware and software.

The sensors used in the VSC system include wheel speed sensors for all four wheels, a throttle position sensor, steering wheel angle sensor, and yaw-rate and lateral acceleration sensor. The wheel speed sensors provide information regarding vehicle speed at any time. The yaw-rate and lateral acceleration sensor detects the vehicle's lateral acceleration and angular velocity of the vehicle's rotation around the perpendicular axis.

The VSC system can identify understeer by analysing the vehicle's actual rates of yaw compared with the target rates. The calculation is a function of the steering wheel angle and vehicle speed. By analysing the actual vehicle speed and steering wheel input, the computer can identify the appropriate curve or line the vehicle should be travelling along, which is derived using the target yaw rate. The yaw and lateral acceleration sensor analyses the actual yaw rate or line of travel. If the actual yaw rate is different to the target rate, the skid control ECU recognises potential understeer.

If the car is understeering, VSC reduces throttle opening to reduce engine output and applies brakes to the front wheels and inside rear wheel to help turn the vehicle into the corner. If VSC detects oversteer (loss of rear-wheel grip), the brakes on the outside front wheel are applied. This generates an inertial moment in the vehicle's outward direction and helps dampen its tendency to oversteer. A beeping noise is heard in the cabin when VSC is activated.

VSC has been designed as a driver aid. It works most dramatically under slippery conditions such as wet weather, but will also work in the dry. It is not intended as a cure-all for overdriving.

Traction Control: TRC is designed to prevent the driven wheels from slipping when accelerating on marginal traction surfaces. It ensures the vehicle accelerates in the direction the driver intended.

Examples of marginal or dual-traction surfaces would be in winter driving conditions, on tarmac roads when rain has fallen after a prolonged dry spell and when accelerating with one side of the vehicle on a low-traction road surface, like grass or gravel. If the skid control ECU detects wheel slippage, it reduces the engine output and also applies some braking pressure to the slipping wheel(s).

Strong safe and built to last

The new Aurion has the highest body rigidity ever achieved in a built-in-Australia Toyota model. The foundation for Aurion's new body is a global underbody that optimises ride, handling and safety. Aurion's strong body contributes to high levels of passive safety and low noise vibration and harshness (NVH). The highly rigid body provides a stable platform for Aurion's revised suspension package.

Aurion's new body structure makes extensive use of high-strength steel to maximise strength and rigidity while minimising weight. Body structure features include substantial sub-frames and a newly adopted cowl top outer panel that mounts directly to the top of the suspension towers.

All Aurion models have a substantial V-shaped brace behind the rear seat back, connecting the rear suspension towers and the floor. Anti-corrosion steel is used for virtually the entire Aurion body, except the roof and some interior panels, to ensure longevity.

Aurion models fitted with a moonroof have a unique roof panel pressed from anti-corrosion sheet steel, with the moonroof aperture created in the stamping process. Corrosion protection measures also include PVC coating applied to the underside of the body, the rear wheel housings and other key parts. Large rocker panel mouldings help protect the doors from possible stone chipping.

High standard in passive safety

All Aurion models have six SRS airbags, for high levels of passive safety. Toyota uses Computer Aided Design (CAD) and numerous on-vehicle tests to achieve high levels of crashworthiness. Aurion's new body was designed to minimise cabin deformation in front and side collisions.

The body is designed with a comprehensive strategy to act as a crumple zone and channel impact loads away from the cabin. The cabin has been reinforced and the load paths re-engineered to minimise cabin deformation in front or side collisions.

In addition, Aurion has a package of features to reduce the chance of injury to pedestrians, including crash-absorbing brackets in the front guards. This package includes impact-absorbing front fender brackets and a new bonnet support frame to provide uniform distribution of impact loads to reduce trauma to the head and torso of a pedestrian.

Aurion's impact-protection measures for occupants include impact-absorbing material in the door trims to reduce impact to the body in the event of a side collision. It also has head impact protection (HIP) impact-absorbing materials and structures in the pillars and roof side rails. Aurion's front seats employ Toyota's WIL (whiplash-injury lessening) design to reduce the chance of neck injury in a rear-end collision.

Aurion has a dual stage front SRS airbag system, which measures the intensity of the collision and deploys the airbags accordingly. Front-seat side airbags and side curtain-shield airbags are also standard equipment.

Aurion also has height-adjustable seatbelt upper anchorages, pretensioners and force limiters in the front seats and three-point automatic locking retractor/emergency locking retractor seatbelts in all three rear-seat seating positions.

Aurion Presara lights the way

The new top-of-the-range Aurion Presara has the added active safety feature of Toyota's intelligent adaptive headlamp system - to allow drivers to see slightly further ahead of corners. The system, known as AFS (Adaptive Front-lighting System), operates on Aurion Presara's high-intensity discharge projector-type low beam lamps only.

The AFS system is in addition to the auto-levelling headlamp technology specified in Australian Design Rules for HID-type headlamps. The new Toyota AFS technology consists of a swivel actuator for each low beam lamp and a dedicated ECU to extract the required information from the steering angle sensor and the front-wheel speed sensors. The articulation angle is specific to each lamp and to whether the vehicle is turning right or left. The right-hand lamp has a range of 15 degrees movement and the right-hand lamp a range of 10 degrees. The Toyota AFS is activated once the vehicle is travelling forward at more than 10km/h and when the steering articulation angle exceeds six degrees.

Rain sensing wipers

New Aurion Presara has automatic rain-sensing windscreen wipers. It is the first six-cylinder Toyota vehicle built in Australia with this feature. The rain-sensing wiper system automatically establishes wiper speed, including intermittent wiper interval. It is designed to increase convenience and reduce potential driver distraction.
The rain sensor consists of two light-emitting diodes (LED) that emit infra-red rays, a lens and a photo diode that receives those rays. The sensor is attached to the windscreen and located behind the interior mirror. The detection method is based on the infra-red rays that are reflected by the windscreen glass onto the photo diode. If no raindrops are present, all the infra-red rays from the LEDs are reflected to the photo diode.

If raindrops are present in the detection area, the difference in refractive indices of the glass and the area above the windshield changes and a portion of the emitted infra-red rays penetrates the windscreen, reducing the amount of rays received by the photo diode. In addition to detecting rain, the system varies wiper speed according to the volume of rain falling on the windshield.

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Related entries:

Toyota TRD Aurion and HiLux at Melbourne
Toyota Aurion Sports Concept Unveiled (AU)
Toyota Aurion V6 Joins Police (AU)


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