Vehicle control system and vehicle control method

A vehicle control system comprising:

• a first controlled variable calculating unit that calculates a first controlled variable used for controlling at least one of a braking force and a driving force of each wheel so as to optimize a μ utilization ratio of said each wheel, or an integrated controlled variable including the first controlled variable and a second controlled variable used for controlling a steering angle of said each wheel, based on constraints including, as parameters, a target resultant force to be applied to a vehicle body so as to achieve a vehicle body motion desired by a driver and a size of a friction circle of said each wheel;
• a second controlled variable calculating unit that calculates a steering controlled variable of each wheel for achieving the target resultant force by controlling only the steering angle of said each wheel;
• and
• a controller that determines a final controlled variable used for controlling at least one of the steering angle, the braking force and the driving force of said each wheel such that a proportion of a sum of the second controlled variable and the steering controlled variable, calculated by at least one of the first controlled variable calculating unit and the second controlled variable calculating unit, for controlling the steering angle of said each wheel in the final controlled variable is made larger than that of the first controlled variable used for controlling at least one of the braking force and the driving force of said each wheel in a region in which the μ utilization ratio is small, than those in a region in which the μ utilization ratio is large.

A method of controlling a motor vehicle, comprising:

• calculating a first controlled variable used for controlling at least one of a braking force and a driving force of each wheel so as to optimize a μ utilization ratio of said each wheel, or an integrated controlled variable including the first controlled variable and a second controlled variable used for controlling a steering angle of said each wheel, based on constraints including, as parameters, a target resultant force to be applied to a vehicle body so as to achieve a vehicle body motion desired by a driver and a size of a friction circle of said each wheel;
• calculating a steering controlled variable of each wheel for achieving the target resultant force by controlling only the steering angle of said each wheel;
• and
• determining a final controlled variable used for controlling at least one of the steering angle, the braking force and the driving force of said each wheel such that a proportion of a controlled variable used for controlling the steering angle of said each wheel in the final controlled variable is made larger than that of a controlled variable used for controlling at least one of the braking force and the driving force of said each wheel in a region in which the μ utilization ratio is small, than those in a region in which the μ utilization ratio is large.