Home > CAD Parts
- Reinforcement Learning for the Cart-Pole Apparatus
- H-Gantry
- Robotic Arm
- Freenove Smart Car Rear- and Front-Mounts
- Elevator
- DC Motors
This page documents parts I have designed for 3D printing. See here for general 3d-printing notes.
Reinforcement Learning for the Cart-Pole Apparatus
This is not a new concept. If you search for “cart-pole balancing”, you’ll see that this problem has been solved in a variety of ways. However, the details are always interesting, and I was curious whether my RLAI would find a solution. This is a work in progress.
H-Gantry
How to control a two-axis linear gantry system? The simple solution is to use two stepper motors, one attached to each axis. The harder solution: Use two fixed-position stepper motors with a crazy, winding belt. There are advantages each way. The former is simpler to design and build; however, the motor mass is attached to each axis, which is not ideal when the axes are changing direction quickly. In the latter design, the motors have fixed positions, so the motor mass is not attached to a moving axis. The control is more complicated, but this makes it interesting, which is also an advantage! The software is here.
Robotic Arm
This was the first real project that I pursued with 3D printing. The concept is basic, including five degrees of freedom driven by SG90 servo motors. The design poses several good challenges for anyone starting out with CAD or—like me—returning to CAD after a very long time (9th grade high school, if my memory serves):
- Mobility: A little practice goes a long way toward designing solid objects from 2D sketches (points, lines, circles, planes, etc.) and 3D operations (extrusions, joins, cuts, holes, etc.). I found the learning curve to be quite gentle in this regard, particularly with the right CAD system (more on this later). It was much more difficult to build constrained movement into the design. Think hinges and keyed rotation shafts. These were tricky at first, but effective patterns became evident after a few attempts.
- Motor-part integration: This is where the magic happens, where the design comes to life. In the case of the robotic arm it was a matter of connecting the rotating shaft of the SG90 servo with a mobile part of the arm design.
- Build tolerance: Mobility requires parts to be in contact but not be too tight. CAD provides exact precision, and although entry-level 3D printers provide surprising fidelity, they are not exact. However, the inexactness is systematic in my experience, and small tolerances seem to be quite achievable.
All of this adds up to a good bit of time, failure, iteration, and fun. Full details can be found here.
Related projects:
Freenove Smart Car Rear- and Front-Mounts
The smart car comes out of the box with a front-mounted camera. I designed this bracket to move the camera to the back and provide room for front-mounted parts like the robotic arm described above.
The files for this design can be downloaded from Thingiverse here.
Related projects:
Elevator
This is an elevator designed for the stepper motors found here.
Full details can be found here.
Related projects:
DC Motors
The following is a four-coil brushed direct-current (DC) motor:
Full details can be found here.