Automatic steering system and automatic steering method

An automatic steering system for a work vehicle that automatically travels along a predetermined travel route on a work site, comprising:

• a steering travel apparatus for performing leftward turning based on a leftward steering amount with respect to a straight-forward direction and performing rightward turning based on a rightward steering amount with respect to the straight-forward direction;
• a subject vehicle location calculator for calculating a location of a subject vehicle;
• a locational shifting calculator for calculating locational shifting from the travel route and the location of the subject vehicle;
• a vehicle body direction calculator for calculating a vehicle body direction that indicates a direction of a vehicle body;
• a directional shifting calculator for calculating directional shifting from the travel route and the vehicle body direction;
• a steering amount calculator for calculating a first steering amount, which is the steering amount for correcting the locational shifting and the directional shifting, based on the locational shifting and the directional shifting;
• and
• a steering amount limiter for limiting the first steering amount based on a second steering amount, the second steering amount being a steering amount at present,
• wherein:
• in response to the second steering amount being the leftward steering amount, the steering amount limiter limits the first steering amount to the leftward steering amount and a neutral steering amount, and
• in response to the second steering amount being the rightward steering amount, the steering amount limiter limits the first steering amount to the rightward steering amount and the neutral steering amount.