Electronic Torque Vectoring: Revolution in Vehicle Dynamics
Introduction: From Mechanical Differentials to Electronic Control
The evolution of torque management systems has progressed from simple mechanical differentials to complex electronic systems capable of distributing power between wheels in real-time. Electronic Torque Vectoring is a technology that fundamentally changes vehicle motion physics.
Basic Principles of Torque Vectoring
What is Torque Vector?
In vehicle physics, torque has both magnitude and direction. Torque vectoring allows:
- Changing torque distribution between wheels
- Creating steering moment around vertical axis
- Compensating for understeer and oversteer
- Optimizing traction in various conditions
The Physics Process
During cornering, several forces act on the vehicle:
- Centrifugal Force - pushes vehicle outward
- Traction Force - limits torque transmission capability
- Gyroscopic Moments - generated by rotating masses
Torque vectoring uses torque difference between wheels to create Steering Moment (Yaw Moment).
Types of Torque Vectoring Systems
1. Brake-based Torque Vectoring
Operating Principle: Braking inner wheel during cornering to create torque difference.
Characteristics: Simple implementation, high heat generation.
Examples: BMW xDrive (basic version), Audi quattro with brake torque vectoring, stability control systems with extended functions.
2. Active Differential Systems
Operating Principle: Electronically controlled multi-plate clutches with continuous variation of locking.
Characteristics: Precise torque distribution between wheels.
Examples: Audi Sport Differential, BMW M Active Differential, Mercedes-AMG Torque Vectoring.
3. Dual Motor Systems
Operating Principle: Separate electric motors for each wheel with complete independent control.
Characteristics: Maximum precision and speed.
Examples: Tesla Model S Plaid (with limitations), Rivian Quad-Motor, new electric vehicle developments.
Practical Applications in Various Conditions
1. Cornering
Corner Entry: Preliminary torque distribution, creating mild understeer, vehicle stabilization.
Apex: Maximum torque vectoring, optimal traction utilization, slip minimization.
Corner Exit: Gradual torque increase, trajectory stabilization, preparation for next maneuver.
2. Acceleration on Split-Mu Surfaces
Situation: One wheel on asphalt, another on ice.
Without Torque Vectoring: Wheel spin on ice, traction loss, stability control activation.
With Torque Vectoring: Torque redistribution to wheel with better traction, smooth acceleration without wheel spin, stability preservation.
3. Emergency Lane Change
Situation: Avoiding sudden obstacle.
Conventional Vehicle: Sharp steering input, potential stability loss, extended recovery time.
With Torque Vectoring: Coordinated torque distribution, minimal trajectory deviation, rapid stability recovery.
Impact on Vehicle Characteristics
Handling
Steering Response Improvement: Reduced response time, more predictable behavior, increased "sharpness" of handling.
Limits Handling Expansion: Higher cornering speeds, better stability at traction limits, smooth transition to slide/plow.
Safety
Active Safety: Prevention of skid development, compensation for driver errors, improved handling in critical situations.
Passive Safety: More predictable trajectory during loss of control, preparation time for safety systems before impact.
Future of Torque Vectoring
Integration with Autonomous Driving
System Coordination: Torque vectoring as part of ADAS, synchronization with stability control, integration with adaptive cruise control.
Predictive Control: Using mapping data, accounting for road topography, weather condition adaptation.
Electrification and Torque Vectoring
Electric Vehicle Advantages: Instant electric motor response, precise torque control, regenerative torque vectoring capability.
New Architectures: Hub motors, modular powertrains, distributed control systems.
Technical Challenges and Limitations
Heat Generation
Brake-based System Issues: Brake mechanism overheating, reduced efficiency when hot, operational duration limits.
Solutions: Improved cooling, combined systems, transition to active differentials.
Complexity and Reliability
Mechanical Complexity: Multiple additional components, higher quality requirements, complex maintenance and repair.
Electronic Reliability: Dependence on multiple sensors, criticality of electronic failures, complex fault diagnosis.
Practical Recommendations
For Drivers
Technology Familiarization:
- Gradual Adaptation - Give yourself time to adjust
- Safe Environment Experimentation - Feel the difference
- Feature Study - Each system has nuances
Effective Usage:
- Smooth Corner Entry - Systems work better
- Trust the Electronics - Don't fight the system
- Regular Maintenance - Critical for complex systems
For Engineers and Tuners
Settings Optimization:
- Balance between sharpness and stability
- Consideration of tire characteristics
- Adaptation to intended use
Diagnostics and Maintenance:
- Regular sensor calibration
- Actuator condition monitoring
- Software updates
Conclusion
Electronic Torque Vectoring represents a fundamental shift in vehicle dynamics. This technology overcomes physical limitations of traditional systems and creates new possibilities for vehicle control while enhancing safety without compromising driving pleasure.
Understanding these systems' operating principles allows not only better utilization of their capabilities but also anticipation of future automotive technology development.
This article is based on SAE technical publications, leading automaker patents, and practical experience with active control systems.