Patent ID: 7793755

Claim:
A steering system for use in a vehicle having a steering wheel and a tire wheel, the steering system comprising: a first motor that is configured to generate a first torque for use in varying a transmission ratio between a steering wheel angle of the steering wheel and a steering tire angle of the tire wheel; a first speed reducer mechanism that is configured to increase the first torque of the first motor and output the first torque so that the transmission ratio is variable; a first rotation angle sensor that is configured to detect a first rotation angle of the first motor; a second motor that is configured to generate a second torque for use in assisting in steering the tire wheel; a second speed reducer mechanism that is configured to increase the second torque of the second motor and output the second torque so that the steering of the tire wheel is assisted; a second rotation angle sensor that is configured to detect a second rotation angle of the second motor; a steering wheel angle sensor that is configured to detect a value of a steering wheel angle of the steering wheel; and a steering wheel angle computation processing unit that is integrated with the steering wheel angle sensor, wherein the steering wheel angle computation processing unit includes: a steering wheel angle estimation device that is configured to respectively obtain the detected first and second rotation angles of the first and second motors from the first and second rotation angle sensors, wherein the steering wheel angle estimation device is configured to calculate an estimation value of the steering wheel angle of the steering wheel based on the detected first and second rotation angles; and a steering wheel angle comparison device that is configured to compare between the estimation value of the steering wheel angle and the detected value of the steering wheel angle.