Growing up on his family's farm was not easy for student Théo Gautier, as he was responsible for transporting heavy things to perform repairs around the land. One time he tried to build a gate but found that his small wheelbarrow was unable to move the heavy tools and building supplies required, which led him to create an autonomous robot that can carry up to 100kg of material across a wide variety of terrain. This system would need a way to automatically track the target and follow it, as well as support the weight of whatever might be loaded into its container.
Gautier created his CAD model with the help of Fusion 360. He began with a base of lattice steel tubes that had been placed in a lattice for extra strength. There is an additional box on top of the chassis that houses the batteries, electronics, and supports the weight on top. Finally, the four wheels were positioned underneath the chassis and protected by a metal bar. A simple wooden box sits on the top and it holds the cargo.
This four wheel drive robot required a lot of components to work, including four individual motors, motor drivers (50V 16A MOSFETs), and a microcontroller. In this case, however, Gautier decided to use two different MCUs: a PixyCam2 for gathering and processing images, and a SAM D21E mounted on a custom PCB to take that data and move the motors appropriately.
The chassis for this robot was constructed from a series of 40mm by 40mm steel tubes that were cut at various angles so they could be welded into a strong frame. Once the wheels and axles were mounted, each pair had a motor placed just behind that directly drives the wheels- no gearing necessary. Gautier then welded on a compartment for housing the electronics and batteries which he later painted red to give it some extra visibility. And finally, the basket was constructed from a piece of plywood that he cut with a CNC mill into several flat panels that got glued together. All of this work meant his robot could easily withstand the harsh weather and terrain that is often encountered while farming.
After soldering the MOSFET motor drivers onto a custom-milled PCB and running wires to the motors/batteries, Gautier connected it to the SAM D21E board along with the PixyCam2 and placed the whole assembly into the robot's chassis along with the batteries.
His code works by continuously reading new images from the PixyCam2 and checking the position of the target within a bounding box. If adjustments are needed, the robot can then move left, right, forwards, or stop. The robot also contains an HC-SR04 ultrasonic distance sensor that can prevent the wheels from moving if it gets too close to an obstacle.
As seen in Gautier's project demonstration video, his robot works very well for moving materials across his family's farm. It will be exciting to see what new features he can incorporate into this system for more accuracy or speed. You can read more about his project here.