Two-dimensional Localization System of a Legged Robot for Shaft Tillage Cultivation

We studied shaft tillage cultivation as practiced by an autonomous robot. Through previous studies, we determined that leg locomotion has a higher compatibility with the shaft tillage method than wheeled locomotion. Therefore, we are currently developing a legged robot for shaft tillage cultivation. In general, robots require a positioning system to autonomously travel in fields. The objectives of this study are the development of a localization method for an agricultural legged robot and an evaluation of the localization method. We assumed that an agricultural legged robot exhibits its slowest wave gait when walking. In this gait, after each leg is sequentially moved, the body is moved forward to complete one movement. This means that the body stops for a long time despite the robot is walking. The proposed localization method utilizes this unique characteristic of the legged robot. This study first reports on the development of localization using a laser distance sensor and a pan-tilt unit. Secondly, we report on a localization experiment to evaluate the localization accuracy of the proposed method. In this experiment, a total station with automatic target recognition was used as a ground truth. From the experimental results, we found that the measurement error between the proposed method and the total station data was approximately 14mm and 0.232°. Additionally, we found that we could improve the localization accuracy if we could fix the reflector sheet with higher accuracy and replace the laser distance sensor with a more precise resolution. Therefore, we determined that the legged robot will be able to autonomously travel with a positioning accuracy of approximately 10mm when using the proposed localization method.