Design of Front-back Symmetric Four-wheel-steering Mobile Robot

Ackermann steering can reduce the turning radius of a vehicle to a limited extent, and individual steering for mobile robots increases cost owing to the need for more actuators. Therefore, in this paper, we propose a novel front-back-symmetric-steering mechanism that allows four-wheel steering using only two actuators. A robot prototype is fabricated to verify the basic performance of this design. The proposed steering system has no restriction on the change of the steering angle; therefore, the robot can rotate in place without lateral slip of the wheels. In addition, the four-wheel-drive function combined with the steering mechanism facilitates smooth driving even on somewhat uneven road surfaces without requiring a suspension system. As a result, the proposed steering mechanism is expected to apply to various mobile robots owing to its simplicity and the ability to achieve excellent rotation characteristics.