WARNING
Fast-spinning blades are very dangerous. If you make this machine by yourself, please be very careful and ensure the safety of your surroundings before using it.
How dose it work.
Roktrack heads to the pylon recognized based on camera image. When it approaches the pylon more than a certain amount, it turns around and searches fot next one. By speeding up the turning timing with each lap, it will enter from the outside to the inside. A custom model trained on pylon images in yolov8 is used for recognition. Object detection shows the height of the pylon. By determining how high to approach, the turning timing is adjusted.
Blades
It is equipped with two blades. This allows pebbles to be ejected backward when they hit the blades, making the blades more durable. The upward-facing nylon cord prevents weed from tangling around the motor shaft.
With a single blade, the blade must be enlarged to the limit of the body's width in order to provide as much cutting width as possible. Then, in an environment where there are pebbles, the pebbles will get caught between the blade and the body. This would be a disaster, the fuse would blow in an instant, and the blade would be very badly damaged. It took more than 30 fuses and dozens of blades to achieve this shape. Now the grass is not tangled at all and the blades function for dozens of hours. This shape of blade allows mowing of weeds and grass up to 15 cm.
Rough Terrain
Eccentric tires on the outside of the sprockets allow the machine to overcome bumps of up to 5 cm. No additional actuator is required as the tire is directly attached to the sprocket.
Exterior
Interior
Best pylon color
The color of the pylon, which has a high recognition rate and can be detected from a distance, is red. Blue and green are more common in nature, so the recognition rate of blue and green is low.
Spec
Weight | 5~7kg |
Battery | Lifepo4 4S 12.8V |
Pylon Recognizable Distance | 15~30m |
Maximum working area | 20m * 20m |
Working hours per charge | 2~3 hours |
Mowing width | 20cm |
Speed | 1 km/h |
Raw Material Cost | $330 |
Recognizable Object | Pylon, Person, Roktrack, Digit, Animals |
Solar Power
Roktrack can also be recharged by solar panels, and if the weather is clear, it will continue to mow the weed automatically for about 15 minutes a day, permanently.
The solar panels generate 4W each at an open circuit voltage of 22V according to the data sheet. In reality, they generate about half that amount. Charge and discharge management is done by an off-the-shelf solar charge controller. These controllers can be set for cutoff and return voltages. If I set the cutoff to 12.7V and the return voltage to 13.2V, the system runs for 10-15 minutes every day when the weather is nice. If the cutoff voltage is lowered and the reset voltage is increased, it can run for an hour once every few days. At first I was trying to properly calculate the amount of charge, etc., but the voltage drop caused by the mowing motor (RS775) was so severe that I gave up trying to calculate it accurately. I decided on a setting that would work to some degree each day by changing the cutoff and return voltage over several days.
Wiring Diagram
*Each component is an image and differs from the actual component used.
Multi Node
Steep Slope
If two units work together, they can handle slopes of up to 60 degrees...
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I just saw your YT video and commented on it. Decided to ask my questions here. I hope you can answer them.
1. I assume running the two blade motors consumes most of the power.
a. Have you considered using only a plastic string cutter (or two) instead of using small metal blades?
b. Wound string cutters be more tolerable and less prone to damage by rocks or metal debris?
c. Does it have an overload protection when it cuts over very heavy/thick weeds?
2. Have you tried your robot in fields that have never been cut before? Does the robot slow down in heavy cutting applications?
3. Does the robot "know" when the weeds or grass needs to be cut again or is it simply based on time or performed daily regardless of weed growth?
4. Does the robot "know" when it does not have enough power to continue operating properly and stop automatically?
5. How does the robot reacts when it hits a tiny tree that it cannot roll over or prevents it from moving? Does it reverse and goes around the tree or obstacle?
6. Instead of pylons, have you considered using GPS or other methods for defining the area of the cut?
b. Must the pylons be in a rectangular shape (i.e., one in each corner, and add pylons for distances greater than 10M?)
7. What made you decide on RaspPi versus an Arduino based system? Would you have remained with Python if you used a Pi 5?
8. Will you continue working on this robot or move on to a new project?
Thanks!
Claude