CONTROL OBJETIVE OF DIFFERENTIAL BRAKING/STEERING

The major objectives of this differential braking/steering system can be described as:

  1. The vehicle should have the same orientation as the road.
  2. The vehicle should stay at the center of the road and have inertial acceleration equal to when driving on curve with radius
  3. Under certain circumstance, the cornering stiffness
can be changed suddenly due to abnormal road surface conditions, such as icy patch, etc. The vehicle would lose stability. A control effort should be exerted to resume the stability of the vehicle. The control effort can be realized by applying an extra torque on the front wheels by differential braking.
  1. Cs should be assumed to become small on the front tires, but not the rear tire. This should cause skidding.
  2. The time to switch the differential braking controller ON/OFF to ensure
    1. The vehicle does not skid (e1, e2 remain small)
    2. The switching is smooth and lateral ride quality is maintained
    3. Frequent switching the differential braking switching ON must be avoided as it could hamper the normal driving style of the drivers. It should be switched on only in the case of an emergency, also skidding has to be avoid.
  1. During the skidding, the linear tire model is no longer adequate (and neither are the small angle approximations). A nonlinear tire model is required.