Development of a quadruped robot platform for optimizing wheat and corn field for phenotyping

Abstract

Phenotyping farmland can be very challenging as the terrain is not even, and at times, due to continuous rain, the dirt can be muddy. Current solutions, such as wheeled robots, are ineffective because the wheels become trapped in the mud. Our proposed solution is to develop a quadruped platform robot explicitly built for phenotyping farmland. The idea was influenced by current quadrupeds platforms such as Spot from Boston Dynamics and the MIT Cheetah. The quadruped would be equipped with cameras and sensors to properly phenotype the plants on the field where data can be accessed live but would be processed offline through other means.The project’s approach to the problem led to the creation of three different quadruped prototypes, with each iteration being upgraded. Starting with the initial SpotMicro, subsequent iteration with the OpenQuadruped, and lastly, the “OmniAgrobot” brushless quadruped. The bodies of the three systems involved precisely designed 3-D printed parts made out of PETG filament due to their enhanced durability to UV resistance and stress handling. The first two platforms involved using servo motors for 12 degrees of freedom, with the second model red dog having a higher torque and different placement of the servo motor to reduce the stress on the lower part of the leg by placing it next to the upper leg. The two iterations had issues with weight, and the servos were not strong enough to hold them in place when tested in outdoor environments. OmniAgrobot, the brushless quadruped, uses a ROS motion control algorithm developed for the OpenQuadruped but modified with a hardware interface for brushless motors. The motion algorithm, called CHAMP, sends position commands to each of the 12 motors and updates them accordingly. The actuator was initially built using 3D-printed parts. The gears were made from nylon, while the housing was made of PETG. The 3D-printed actuators worked great and could output 12.8Nm of torque at 10 amps with a difference of 0.6 Nm from the calculated torque loss due to backlash and other factors. With the success of the 3D-printed actuators, prebuilt motor actuators were acquired with a higher torque of 23.814Nm at ten amps. The torque is enough for the robot dog leg to stand up with a payload of 4KG with these commercial actuators. The results of this research prove the feasibility and effectiveness of quadrupeds in the agricultural field for phenotyping crops for diseases like Fusarium Head Blight(FHB) in wheat and barley. The maneuverability and versatility of the quadrupeds provide superior mobility to the current options of using wheeled robots. Using a real sense camera can prove helpful when it's used for phenotyping, as this could provide a point cloud and RGBD imaging. The quadruped may also improve their mobility by using an IMU and upgrading their motion algorithm with the help of machine learning methods in the future.