Honda Develops World's First Super Handling All-Wheel Drive

1 April, 2004 - Honda Motor Co., Ltd. today announced the development of a new Super Handling All-Wheel Drive system, called SH-AWD, that provides cornering performance that responds faithfully to driver input, and outstanding vehicle stability. A world’s first, the SH-AWD system combines front-rear torque distribution control with independently regulated torque distribution to the left and right rear wheels to freely distribute the optimum amount of torque to all four wheels in accordance with driving conditions. The new system will be available this autumn in the Acura RL (North America) and the Legend (Japan).

By monitoring driver input and driving conditions, the SH-AWD system determines the optimum front-rear and lateral (left-right) torque distribution. This information is then conveyed to the rear differential, where direct electromagnetic clutches continuously regulate and vary front-rear torque distribution between ratios of 30:70 and 70:30, and lateral torque distribution in the rear wheels between ratios of 100:0 and 0:100. Torque is used not only for propulsion, but for cornering as well, resulting in a significant enhancement in vehicle manoeuvrability.

The SH-AWD system is composed of sensors to detect steering angle, lateral g, and other vehicle information; an ECU; and the rear differential. The direct electromagnetic clutches inside the rear differential, another world’s first, employ electromagnets to obtain precise control over the multi-plate clutches. Built-in search coils monitor the gaps between the electromagnets and the magnetic body to achieve precise, continuously variable torque regulation.

The rear differential is also equipped with a built-in acceleration device, yet another world’s first. During cornering, the track of the outside rear wheel normally falls outside the average of the tracks of the front wheels. The outside rear wheel does not rotate fast enough to keep up with the front wheels, preventing efficient transmission of torque. To counteract this problem, the SH-AWD acceleration device alters the gearing to speed up the outside rear wheel’s rotation relative to the front wheels. This reduces torque transmission losses and significantly improves vehicle manoeuvrability.

At Honda, driving pleasure is regarded as one of the most important factors in vehicle development. The new SH-AWD system features "feed-forward" control, which utilises the degree of driver input to determine appropriate torque distribution. This results in a super-neutral steering feel that responds with optimal faithfulness to the driver’s handling of the steering wheel, realising outstanding driving comfort and stability.