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Figure 1. Final product of HKP
Figure 2. CAD of HKP
In order to achieve the given functional requirements, a new Hybrid Kapitza's Pendulum (HKP) mechanical design was created, and closed-loop controls were performed using electrical components from the Spring 2024 project team. The final product of the new design is shown on the left, with front and back views of the HKP.
Detail Design
Figure 3. Scotch Yoke CAD
Scotch-Yoke Mechanism
Scotch-Yoke Mechanism
The conversion of rotational energy into linear motion is achieved via the scotch-yoke assembly shown in the left. The drive consists of a center shaft coupled to a flywheel, which supports an offset roller assembly. To optimize the contact interface, the roller is encased in a 3D-printed ring made with VeroClear and Agilus30.
Multi-Layer Rotation Mechanism
Multi-Layer Rotation Mechanism
To facilitate independent rotation for both the scotch-yoke mechanism and the circular frame along a shared axis, a concentric multi-layer assembly was developed as shown on the right. The architecture of this mechanism ensures independent rotation motion.
Figure 4. Cross-sectional view of the Multi-Layer Rotation Mechanism CAD
Figure 5. CAD of timing belt mechanism
Timing belt mechanism
Timing belt mechanism
One of the most significant changes we'll be implementing onto the Hybrid Robust Kapitza's pendulum is the addition of a timing belt - pulley mechanism.
The said mechanism was designed to reduce strain and torsional stress on the servo motor and its shaft, respectively. It introduces new elements like the servo and shaft pulleys, a timing belt, and idler pulleys, with the latter serving the purpose of increasing wrapping around the pulleys to prevent slipping in the belt from taking place.
Frame Stabilization System
Frame Stabilization System
The circular frame’s rotation is restricted to one degree of freedom through a triad of V-grooved rollers. This configuration clamps the frame securely, ensuring it remains concentric with the rotation axis. To maintain the integrity of this constraint, lock bolts and spacers are utilized to prevent the rollers from shifting under load, thereby ensuring consistent tracking and preventing unwanted frame movement. An eccentric bushing was incorporated in the bottom roller. Through rotation, the eccentric bushing allows for vertical adjustment of the bottom roller to optimize frame contact and avoid overconstraining.
Figure 6. CAD of V-grooved rollers assembly
Figure 7. CAD of bottom V-grooved roller with eccentric bushing
Figure 8. ST3215 Servo
ST3215 Serial Bus Servo & Driver Board
ST3215 Serial Bus Servo & Driver Board
The new servo was selected to overcome the 270-degree rotation limit of the previous design in 2023 and 2024 Team, thereby enabling unrestricted 360-degree rotation of the circular frame. Because the ST3215 cannot be driven directly by the microcontroller, an additional driver board was integrated to facilitate communication with the Arduino Due. Same electrical components are used from Team 2024 and the wiring diagram is shown below
Figure 9. Wiring diagram
Protection Box
Protection Box
Due to the high frequency of oscillation during the operation, a protection box made from polycarbonate is fabricated (as shown in Figure 2.1.11). Due to the reflection of the protection box material, a window is set in the front panel for the camera.
Figure 10. Protection box
Performance
To verify that the design solution meets all functional requirements, multiple tests were performed and the results were recorded. For the robustness validation, a running test was conducted for 400+ seconds, with each cycle being 1-3 seconds, it is able to meet 100 cycles operation, Throughout this operation, the absolute pendulum angle was tracked and the closed-loop system successfully stabilized the medium length and short length pendulum, and stabilized the longest pendulum with human initiation. The HKP successfully achieved inverted stabilization within an average of 3 seconds with a frequency of 16 Hz without an encoder installed, and with a frequency of 14 Hz with an encoder installed due to the additional mass introduced to the oscillating system.
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