This is the machine I designed for my thesis project. Some native plant species in the south west have seeds with extremely tough outer shells, which help them withstand adverse conditions. But when rehabilitating a minesite, we need seeds ready-to-go, they can’t be sitting around in the soil for years before germinating. This machine is able to crack the outer shell without damaging the seed embryo inside – the gap between the rollers can be adjusted to give the perfect amount of cracking effort. In addition, it’s designed to be ergonomic and easy to use and maintain.
This robot platform is just for my own experiments in robotics electronics & software, mostly just building on what I learned from Dusty & the NIARC project. Overall the aim is to provide a platform for localisation & mapping, for very low cost at the expense of added effort.
Structural parts: 3d printed in blue PETG
Drive: 2x high-torque stepper motors, each driven by a TI DRV8825 driver which offers comparatively high performance for the cost. Big fat squishy tires since hard wheels didn’t perform well before. A dedicated stepper cooling fan will keep things running nicely.
Sensors: 6x HC-SR04 ultrasonic sensors, GY-85 9dof inertial measurement unit.
Electrical & Brains: TBC! The system will run off two 3S lithium batteries in series, giving 24V. I’m aiming to use a separate microcontroller for each system, with CAN communication between systems.
We needed a motor bracket for the NIARC robot, so we had a look at what was currently around. Googling gave a few options in the $10-50 range, which was way too much! So I modelled one of the brackets in Inventor and had it printed in PLA:
This did the job of holding the motor, but it wasn’t very stiff (being made from PLA) which is bad news for accurate odometry, and it took up a lot of vertical space as the fasteners go between the motor and the bracket. So I redesigned it to have the fasteners either side of the motor, and with larger side supports:
This design also used the motor body itself as support structure to minimise flex, when mounted in the upright orientation. The cut-out in the base was to reduce material and allow room for the motor wires if needed. We had two of these printed in fancy red ABS:
These were very stiff and compact, and worked fantastically! You can see them in place here, in an early version of the robot: