Recently, consumers have shown a high level of interest in food safety and security, as well as in reducing environmental impacts. Therefore, for rice, which is the staple food of the Japanese people, its cultivation without the use of herbicides or chemical fertilizers is desired. This paper proposes a two-wheeled weeding robot that floats on a water surface and is equipped with a movable mechanism in which large-diameter wheels contact the soil under their own weight in response to water level height and soil unevenness. The robot body was designed to float on water by placing floats on both sides and spanning the rice row, enabling it to continue moving even as the rice grows. The movable system utilizes a simple yet robust four-bar linkage, which is designed to accommodate soil adhesion. This study first clarified the design method for a four-bar linkage mechanism. Next, it experimentally investigated the effect of the angle of paddles attached to the wheels on the propulsive force. Finally, it experimentally confirmed the effectiveness of the proposed weeding robot.

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