Path planning in continuous adjacent farmlands and robust path-tracking control of a rice-seeding robot in paddy field

Abstract

During rice seeding, paddy fields are segmented by embankments to hold water and evenly supply nutrients to the rice. Reasonable path planning from the entry to the exit of continuous adjacent sublands and accurate path tracking in harsh paddy fields are crucial for efficient and high quality work by an autonomous rice-seeding robot. In this study, four entering and exiting modes with continuous adjacent sublands are defined, and the corresponding planning paths for each mode are provided and analyzed. The optimal working path is obtained under the constraints of full coverage without overlap or skip between rows, minimum blank operation areas at the headland and minimum turns while working; The requirements for the width of standardized farmland and the number the farmland is divided into are given. A kinematic model of the rice-seeding robot embodying slip and side slip is built to achieve reliable and accurate path tracking under adverse conditions of paddy fields. The equivalent disturbances caused by slip and side slip are estimated using a nonlinear observer. Combined with a nonlinear observer, a fast terminal sliding-mode controller is designed for the path tracking of the rice-seeding robot in paddy fields. The control algorithm is validated through simulations and field tests.