A vehicle guidance system for an agricultural vehicle is described which includes an optical imaging device collecting information of field characteristics, and a steering control device receiving the information of field characteristics transmitted from the optical imaging device. The steering control device having a steering actuator including a motor operatively connected to a hub adaptor. The hub adaptor is removably mountable to a central hub of a steering wheel of the agricultural vehicle in fixed rotary engagement, wherein when the hub adaptor is engaged to the central hub of the steering wheel, rotation of the hub adaptor by the motor causes corresponding rotation of the steering wheel. The steering control device thereby autonomously rotates the central hub of the steering wheel in response to the information of field characteristics received by the steering control device and the vehicle guidance system thereby steers the agricultural vehicle.
