Automated Plant Care Robot

This project creates a low-cost, highly reliable, and indoor-applicable automated planting solution, integrating IoT technology and automation to achieve unmanned fertilisation and irrigation management for multiple flower pots.

The currently common pipeline-style automated planting has relatively high costs for equipment installation and maintenance, which remains impractical for home plant owners. Therefore, I came up with the idea of using robots and sensors to build a system that can automatically perform soil monitoring, task dispatching, automatic path finding, automatic irrigation, and fertilisation.

This system consists of two parts: the soil testing kit and the planting operation vehicle.

1. The soil testing kit is equipped with soil sensors, which simultaneously measure the soil moisture and soil conductivity of multiple flower pots. Based on the preset values in the program, it determines whether the corresponding flower pots are lacking water or nutrients, and then sends irrigation and fertilisation instructions via Bluetooth.

2. After receiving the Bluetooth command, the planting operation vehicle will automatically find its way along the black tape path and perform precise operations through the mechanical arm.

This system is mainly implemented by robots. Compared with the pipeline solution, it is easier to modify and transfer, which can reduce construction costs and resource waste.

Soil testing kit:

1. 3x soil sensor (see image 1)
2. bluetooth module (see image 2)
3. arduino uno
4. DC power supply and interface
5. Breadboard and DuPont wires
6. LCD screen
7. 3D printed case and some screws

Robot chassis:

1. Aluminium profiles and their respective connecting parts
2. 2x DC motor and motor mounting base (see image 3)
3. 4x rubber wheels and coupling
4. 4x omniwheels and corresponding coupling, shaft, bushing, shaft sleeve (see image 4,5)
5. bluetooth module (see image 2)
6. Arduino UNO
7. motor driver expansion board (see image 6)
8. lithium battery pack
9. 3D printer waterproof case
10. DuPont wires
11. Hot glue

Functional modules:

1. Mechanical arm
2. Servo motor
3. 3D printed mounting base
4. Aluminium profile
5. Irrigation
6. water pump
7. water bucket
8. water pipe
9. pipe clamp
10. Fertilization
11. Servo motor
12. 3D printed fertiliser box
13. Navigation
14. 4x grayscale sensors
15. black and white electrical tape

To facilitate future expansion and modification, aluminium profiles are used for the vehicle body construction. Other structures can be made using 3D printing. Considering that the water tank capacity should not be too small (I used one around 3L), the vehicle body should also be made as large as possible, as space permits. Therefore, I completed the initial design of the model using SolidWorks and assembled it using assemblies to facilitate subsequent size measurements.

I have attached my complete Bambu Labs model below. Refer to this often as you work through the steps, since it is the easiest way to see how everything is attached.

Before assembling, it is recommended to connect the circuit and conduct a test first. For example, check whether the direction and speed control of the DC motor are normal, whether the suction force of the water pump is sufficient, whether the battery and expansion board can simultaneously power 2 DC motors, 3 servos and 1 water pump, and whether there will be insufficient power supply, etc.

See images for the circuit diagrams for the robot and the functional modules.

The assembly of the aluminium profile frame is relatively simple. No additional processing is required during ordering. Common L-shaped angle brackets and T-shaped nuts are sufficient to complete the connection of the frame. It is also very convenient to make subsequent structural modifications.

After installing the four wheels, the chassis height is determined. Then, based on the diameter and height of the flower pot, the length and height of the mechanical arm when it rotates and unfolds are determined to ensure that the water pipe and fertiliser outlet are above the flower pot.

I have uploaded a copy of the frame I used.

Based on the determined vehicle body dimensions, continue to design the servo motor mounting base, fertiliser box, and waterproof shell for electronic components, etc. These structures do not have high strength requirements and can be produced at a low cost using 3D printing. The subsequent modifications are also relatively simple. I have attached my designs, but you are welcome to adjust them according to your preferences.

Except for the mounting base, which needs to bear force, it is recommended to use a fill of 100%. For other parts, a 15% fill is sufficient.

First, power on the servo motor, run the program, observe the steering direction and angle of the servo motor, and find the appropriate position. Then, assemble the printed fertiliser box, water pipe, and servo unit into a mechanical arm. After powering on, observe whether the rotation angle and height of the mechanical arm are appropriate, whether the fertiliser box is discharging normally, and whether the water pumping force is sufficient.

If the mechanical arm is relatively heavy, you can control the servo motor to rotate slowly through variables to avoid excessive inertia that damages the servo shaft and swing arm.

Based on the size of the flower pot, determine the spacing of the tape placement, move the position of the flower pot, so that when the planting vehicle stops at the "intersection", the extended mechanical arm is exactly above the flower pot.

Then install four grayscale sensors and power them on. According to the indicator lights above the sensors, adjust the four knobs to make the vehicle accurately identify the tape.

Before testing the movement effect of the vehicle, encapsulate the electronic components with a 3D-printed shell to prevent water damage.

Then write the control program to enable the vehicle to change direction according to the sensor values, achieving the effect of moving forward along the tape. Observe whether the vehicle's body is straight when it reaches the "intersection", and adjust the recognition strength of the sensors, the speed of the vehicle, and the control logic to make the vehicle's navigation effect as stable and reliable as possible.

The monitoring end does not require movement, so no battery is needed. A DC power supply would be a better choice.

After setting up the display and sensor circuits, write the program for reading and displaying the data, observe the display effect of the values, then water or lift the sensor probe, and observe whether the change in humidity is normal.

After testing, use the 3D-printed casing to prevent the circuit from being short-circuited by water.

Finally, the automatic pathfinding and robotic arm programs are combined to enable the car to automatically locate water-depleted or fertiliser-deficient flower pots and automatically perform irrigation or fertilisation tasks.

Note: During the testing phase, it is recommended to set a status variable for the servo motors of the robotic arm. When the robotic arm is retracted, it cannot perform irrigation and fertilisation actions.

Conclusion:

The feasibility of this current plan has been verified. In the future, a lifting mechanism could be added to the robotic arm, combined with the use of a pot rack, to achieve vertical three-dimensional planting and increase the utilisation of space.