Objectives

The Warman Competition 2023 is part of the subject that I take in the Spring semester 2023 call 41059- Mechanical Fundamental Design Studio. The main objectives for this project are as follows:

  • Design a system working autonomously to deliver 3 squash balls to the oxidiser silo, and 3 tennis balls to the fuel silo.
  • The system should start and finish in the Setup/Start Zone.
  • The system must finish the task in 120 sec.
  • The system must weight less than 6kg.
  • The system dimension must less than 400 cubic milimeters.

    • Solution proposal

  • My group has 5 members, each member is responsible for a separate component, this is how we decide to design our system:
  • 1. A chassis made with 25x25 aluminum tube with 4 mechanum wheels. (Acknowledge to Carlos Pham)
  • 2. A scoop made with 3mm Plywood and drived by a gearbox. (I am responsible for this component, this will be discussed in the next section)
  • 3. A lift system made with the drawer slide drived by a pulley system. (Acknowledge to William Coxon)
  • 4. A storage with a door to release control by a SG90S servo and 4-bar linkage mechanism (Acknowledge to Sean Kim)
  • 5. An extending arm made of drawer slide integrated wth the lift system. (Acknowledge to Jarred Deluca)

    • Gearbox

    Why a gearbox... We target to the make the robot with lowest budget and the most weight efficient for the component. There are many ways to generatet the rotational movement for the scoop such as servo or stepper motor or a dc motor. However, a servo that can generate a sufficient torque with 350mm lever arm is so expensive for our budget, that is also the reason for rejecting using the stepper motor and the gear dc motor.

    In order to design this gearbox, I applied the following knowledge:

  • AGMA Method (American Gear manufacturers Association) to calculate the module and the face width by verifying the teeth pressure with the load handled.
  • Gear ratio calculation.
  • Deflection in shaft calculation and visualize with bending moment to select the profile for the shaft.
  • Torsion on shaft calculation with PLA material.
  • Analyzing the load capacity to select the suitable bearing.

    • Result

    This is the video that I tested the gearbox and my scoop. As you can see, in the video the gear are 3D printed with red PLA filament not wood material just like in the CAD model. Previously, I have not bought the 3D printer yet so I need to use the 3mm plywood that I can use this free in the Mechatronics lab in the university, to create the 9mm thickness I have to cut 3 pieces of plywood and glue them together. However, there was a problem with the precision of doing that, all the gears were not straightly aligned, I just doing that for submitting my own artifact for my assignment, after that the printer arrived I decided to print all the gears again.

    Code integration

  • I also did the code for the whole system with the Arduino Uno and then my friend Jarred also implemented my base code to the Arduino Mega by changing somne pins.
  • There are 6 DC motors and 1 servo to control. 4 DC motors of the mechanum wheels are controlled with 2 L298N dual bridge drivers.
  • The most challenging part when I debugged that was I always forgot to code the fucntion to turn off the motors after they performed some delay().
  • The second challenging parts here is adjust the distance for driving the chassis, our motors do not have the encoder so I just rely on the delay(time) and did some try and error tests to find out the suitable delay time for it.

    • Conclusion

    After this 12-week project, I have acquired many invaluable knowledge and skill:

  • 1. Documenting the instruction for other people. Some members in my group they want to test the robot, but they do not know what did I do previously, so I found that writing the documentation for the instruction and update all the changes is very important. This can help speed up the process of the testing aligned and minizing the errors that they are likely to make.
  • 2. More skills relating to mechanical drawing: How to have a good design intent when 3D modelling in SolidWorks, How to to the SolidWorks Simulation, AS1100 drawing template and how to create the drawing for manufacturing and how to design for additive manufacturing method.
  • 3. Using the Arduino Uno and embedded C++ to control the motors and servo.
  • 4. How to calculate the torque generate under a certain current and select the driver for the motor.
  • 5. Design the gear with AGMA theory, how calculate the facewidth for the spur gear.