The production SH-AWD is a three-motor hybrid system designed for a sports car and offers high power, lightweight and high response, with high cooling performance for high-load operation such as circuit driving.

The three-motor SH-AWD system features a midship-mounted V6 twin-turbo engine; the direct drive motor of a hybrid system mounted directly on the engine; and a 9-speed dual-clutch transmission (DCT). The front wheels are driven by a twin-motor unit (TMU).

The E-Drive system uses the three motors to enhance cornering performance by torque vectoring and front/rear traction force allocation. Direct acceleration response is achieved by a constant assist according to the accelerator position (AP) utilizing the twin-motor unit (TMU) and compensating lack of low speed torque of the turbocharged engine with the direct drive motor and the high-power battery.

The SH-AWD TMU consists of two independent motors, planetary gear sets and a brake. The TMU can freely allocate the right/left torque in any speed region.

Cross-section of the SH-AWD TMU. Each motor is connected to a wheel. Motor torque is applied to the sun gear, then propels the drive shaft by way of the planetary gear. If the vehicle moves forward, the ring gear is fixed by the one-way clutch. During reverse and deceleration, the ring gear is fixed by the brake to reverse the direction of torque. Tamura and Yoshinari (2016). Click to enlarge.

Honda R&D has been developing “super handling” technology for more than 20 years in the pursuit of ideal vehicle handling. By applying separate Twin Motor Units (TMUs), the brains of Sport Hybrid SH-AWD, on each axle in the new EV Concept, Acura is enabling independent torque vectoring to all four corners. Based upon the learnings from last year’s race, the team updated the system management of the powertrain for more precise thrust at each wheel.

SH-AWD torque vectoring with the TMU. The figure shows the principle of torque vectoring during high speed. If the vehicle speed is a above 200 km/h (the motor speed is 14000 rpm), the brake releases the ring gear, and the rotation speed of the tire is absorbed by the idling of the ring gear. It is thus possible to reduce the rotation speed of the motor. In this case, the torque distribution to the left and right tires without increasing the rotation speed of the motor is possible by drive/regenerative operation of the left and right motors. Tamura and Yoshinari (2016) Click to enlarge.

Acura’s Sport Hybrid SH-AWD technology utilizes the highly responsive acceleration characteristics and regeneration capability of electric motors to advance the torque vectoring systems currently applied to NSX, and available on RLX and the upcoming 2017 MDX.

The system enables ideal handling characteristics in various driving situations by coordinating and managing all dynamic systems, including Electronic Power Steering (EPS), Vehicle Stability Assist (VSA) and Sport Hybrid SH-AWD.

Resources

• Tamura, S. and Yoshinari, T. (2016) “Development of Electric Drive System for New Model Super Sports Hybrid Vehicle,” SAE Technical Paper 2016-01-1685 doi: 10.4271/2016-01-1685