System and method for detecting hands-off state of steering wheel

A system of detecting a hands-off state of a steering wheel, the system including:

• a steering angular speed variance calculation unit configured to determine a variance value of a steering angular speed, detected by a steering sensor while a vehicle is driven, through cumulation for a first predetermined time;
• a steering angular speed estimation unit configured to estimate a steering angular speed through a steering system model determined on assumption that the steering wheel is in the hands-off state;
• a steering angular speed difference calculation unit configured to determine a difference value between the steering angular speed estimated through the steering system model and the steering angular speed measured by the steering sensor through cumulation for a second predetermined time, when the variance value of the steering angular speed is not less than a first threshold value;
• and
• a hands-on/off determination unit configured to divisionally determine the hands-off state or a hands-on state of the steering wheel according to the difference value between the measured and estimated steering angular speeds;
• and
• a steering torque variance calculation unit configured to determine a variance value of a steering torque through cumulation for a third predetermined time, when the variance value of the steering angular speed is less than the first threshold value,
• wherein the hands-on/off determination unit divisionally determines the hands-off state or the hands-on state of the steering wheel according to the variance value of the steering torque,
• wherein the variance value of the steering torque is determined by Equation 3:
• v
• r
• =
• ∑
• i
• =
• n
• n
• -
• N
• (
• τ
• i
• -
• τ
• _
• )
• 2
• N
• ,
• [
• Equation
• ⁢
• 3
• ]
• wherein Vτ indicates the variance value of the steering torque, τ vindicates the steering torque, indicates torque average and N indicates a test time, and
• wherein the steering angular speed compensates for the steering torque generated by reaction force to a road surface to prevent the hands-off state from being falsely detected as the hands-on state when noise is generated from the steering sensor due to the road surface during the vehicle is driven in the hands-off state of the steering wheel.

A system of detecting a hands-off state of a steering wheel, the system including a controller configured of:

• acquiring a steering torque, a steering angle and a steering angular speed while a vehicle is driven;
• determining a variance value of the steering angular speed through cumulation for a first predetermined time;
• determining a difference value between a steering angular speed estimated through a steering system model determined on assumption that the steering wheel is in the hands-off state and the steering angular speed measured by a steering sensor through cumulation for a second predetermined time, when the variance value of the steering angular speed is less than a first threshold value;
• divisionally determining when the steering wheel is in the hands-off state or in a hands-on state according to the difference value between the measured and estimated steering angular speeds;
• determining, by the controller, a variance value of the steering torque through cumulation for a fourth predetermined time, when the variance value of the steering angular speed is not less than the first threshold value;
• and
• divisionally determining, by the controller, when the steering wheel is in the hands-off state or in the hands-on state according to the variance value of the steering torque,
• wherein the variance value of the steering torque is determined by Equation 3:
• v
• r
• =
• ∑
• i
• =
• n
• n
• -
• N
• (
• τ
• i
• -
• τ
• _
• )
• 2
• N
• ,
• [
• Equation
• ⁢
• 3
• ]
• wherein Vτ indicates the variance value of the steering torque, τ indicates the steering torque, indicates torque average and N indicates a test time, and
• wherein the steering angular speed compensates for the steering torque generated by reaction force to a road surface to prevent the hands-off state from being falsely detected as the hands-on state when noise is generated from the steering sensor due to the road surface during the vehicle is driven in the hands-off state of the steering wheel.