Overview
The Huawei xMotion system is a Huawei self-developed intelligent body coordination control system that provides integrated longitudinal, lateral, and vertical coordination control solutions for new energy vehicles.
Torque Vectoring Control (TVC)
Torque vectoring control (TVC) in the Huawei xMotion system addresses vehicle cornering behavior by dynamically sensing road conditions during entry and exit of a turn and adaptively adjusting torque. This helps increase lateral force, reduce the risk of oversteer, and improve vehicle controllability and safety.
Tire friction limit and its effects
Experienced drivers often say that front-wheel-drive vehicles tend to understeer while rear-wheel-drive vehicles tend to oversteer, and this effect is more pronounced in wet or snowy conditions. To explain why, consider the tire, the vehicle component that directly contacts the road. The tire provides the friction that enables vehicle motion, but this friction has limits, commonly represented by the "tire friction circle".
In short: the friction force a tire can provide is limited, so when longitudinal force is large, available lateral force decreases.
In wet or snowy conditions, the tire grip limit is reduced, so for the same drive torque the available lateral force is further decreased. For rear-wheel-drive vehicles, because the rear axle receives all driving torque, the rear tires have reduced lateral force capacity; heavy throttle can exceed the tire friction limit, causing the rear wheels to slip and the vehicle to oversteer. Similarly, front-wheel-drive vehicles can experience understeer when the front tires slip.
Applying torque distribution to mitigate cornering risk
One solution is to redistribute large torque from a single axle to other axles. The TVC feature provided by Huawei xMotion is developed based on this principle.
The TVC feature continuously senses the vehicle state in real time and identifies potential risks of unexpected understeer or oversteer. It reduces risk by adjusting torque across the vehicle. As a key chassis technology for the Tuling platform, this feature is applied on the Wenjie M9 model.
How TVC operates
TVC computes the driver's expected steering angle in real time from collected data and continuously monitors vehicle dynamics. For example, when oversteer is detected, the system reduces rear-drive torque so the rear wheels can provide better lateral force; the reduced torque is transferred to the front drive to maintain overall vehicle torque. This approach reduces the risk of oversteer without a large change in vehicle speed.
Driving behavior with TVC
During cornering, by dynamically adjusting front-to-rear torque distribution, TVC allocates more torque to the rear wheels during turn-in to make steering more responsive and complete the turn quicker. During turn exit, TVC shifts torque toward the front wheels to prevent oversteer while accelerating out of the corner, improving driver stability through the maneuver.
