Patent ID: 11912091
Assignee: TOYOTA JIDOSHA KABUSHIKI KAISHA
Field: Transport (Mechanical engineering)
Classification: CPC B | IPC B

Claim 4:
5. A target roll moment computing method executed by an electronic control unit, the electronic control unit being configured to control a front wheel active steering system and a rear wheel active steering system such that a roll moment to be applied to a vehicle body that is generated by the front wheel active steering system and the rear wheel active steering system becomes a target roll moment, the target roll moment computing method comprising:
computing, by the electronic control unit, a sum of a product of a roll moment of inertia of a vehicle and a roll angular acceleration of the vehicle body detected by a roll angular acceleration detector, a product of a roll damping coefficient of the vehicle and a first-order integral of the roll angular acceleration, and a product of an equivalent roll stiffness of the vehicle and a second-order integral of the roll angular acceleration, as a controlled roll moment to be applied to the vehicle body;
computing, by the electronic control unit, a roll moment around a center of gravity of a sprung mass as a correction roll moment, the roll moment being generated by lateral force on wheels due to roll motion;
computing, by the electronic control unit, the target roll moment based on a value obtained by correcting the controlled roll moment with the correction roll moment; and
computing, by the electronic control unit, a target wheel steering angle of front wheels of the vehicle and a target wheel steering angle of rear wheels of the vehicle for applying the target roll moment to the vehicle, wherein:
the roll moment, Mxδ, is expressed by Mxδ=hsfFyfδ+hsrFyrδ, where hsf is a roll arm length at a position of the front wheels that is a difference between a height of the roll center and a height of the center of gravity at the position of the front wheels, hsr is a roll arm length at a position of the rear wheels that is a difference between a height of the roll center and the height of the center of gravity at the position of the rear wheels, Fyfδ are the tire lateral forces at the front wheels, and Fyrδ are the tire lateral force at the rear wheels, and wherein:
the tire lateral forces, Fyfδ, at the front wheels are expressed by, F
    
     yf
     ⁢
     δ
    
   
   =
   
    
     C
     f
    
    ⁢
    
     
      l
      r
     
     l
    
    ⁢
       
    
     mg
     ⁡
     (
     
      
       δ
       f
      
      -
      
       β
       f
      
     
     )
    
   
  
  ,, where Cf is a normalized equivalent cornering power of the front wheels, lr is a distance in a vehicle front and rear direction between the center of gravity of the vehicle and a rear wheel axle, l is a distance in the vehicle front and rear direction between a front wheel axle and the rear wheel axle, m is mass of the sprung mass, g is gravitational acceleration, δf is a wheel steering angle of the front wheels, and βf is a slip angle of the front wheels, and
the tire lateral forces, Fyrδ, at the rear wheels are expressed by, F
    
     yr
     ⁢
     δ
    
   
   =
   
    
     C
     r
    
    ⁢
    
     
      l
      f
     
     l
    
    ⁢
       
    
     mg
     ⁡
     (
     
      
       δ
       r
      
      -
      
       β
       r
      
     
     )
    
   
  
  ,, where Cr is a normalized equivalent cornering power of the rear wheels, lf is a distance in the vehicle front and rear direction between the center of gravity of the vehicle and the front wheel axle, m is mass of the sprung mass, g is the gravitational acceleration, δr is a wheel steering angle of the rear wheels, and βr is a slip angle of the rear wheels.