This project presents a multi-mission transformer robot capable of operating both as a ground vehicle and a quadrotor drone.
The design integrates constant-velocity (CV) joints, slip rings, and a servo-driven lifting mechanism to enable seamless transformation between driving and flying modes.
We also utilize the dual-use wheel-propeller system, where each wheel houses a brushless drone motor (BLDC) and propeller. This allows the same structure to serve as a rolling surface in ground mode and as an active rotor in drone mode, minimizing redundant components.
| Vehicle Mode | Drone Mode |
|---|---|
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| Leg |
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- Constant-Velocity Joints: Enable torque transfer from body-mounted DC motors to wheels while allowing leg rotation during transformation.
- Body-Mounted Wheel Motors: Reduces unsprung mass, improves robustness, and isolates motors from ground impacts.
- Slip Rings: Integrated between each leg and wheel to transmit power/signals to BLDC motors without cable twisting.
- Servo-Driven Leg Lifting: Central servo connects via a rigid rod to both legs on each side, enabling synchronized lifting with minimal actuator count.
- Integrated Bearing Housings: Maintain alignment and smooth rotation of suspended DC motors during transformation.
- Spring Landing Gear: Provides basic shock absorption for landing impacts, enhancing durability. Extendable structure.
The transformation from ground vehicle to drone involves:
- Leg Rotation: Servo-driven rods lift both legs on one side simultaneously.
- Wheel Orientation Change: Wheels rotate from vertical (ground) to horizontal (flight) position.
- Propeller Activation: Embedded BLDC motors power the propellers for lift-off.
- CAD Software: Autodesk Fusion 360.
- Realistic Weight Estimation: We assigned accurate material densities and created custom materials for realistic mass and flight capability predictions.
- Hierarchical Component Design:
- Body Assembly:
- Two-layer chassis (lower plate for battery/power, upper plate for electronics, servos, and lifting mechanism).
- Proper kinematic alignment of servo rotation axis with bearing housings to ensure smooth leg lift.
- Weight Excess: Actual build heavier than estimated, requiring more powerful motors.
- Slip Ring Current Overload: Initial 6-wire slip rings exceeded rated current by ~30% after upgrading motors for higher lift capacity.
- Redundant 4-Wheel Drive: Could be replaced with 2-wheel drive for weight and cost reduction.
- Non-Modular Leg Connection: Rod connecting legs is fixed, making 3D printing and replacement more cumbersome.
- Slip Ring Upgrade: Replace 6-wire slip rings with 12-wire for high-current accomodation (identical series, slightly longer).
- Weight Reduction: Optimize structural parts, reduce material where possible, and reassess drive configuration.
- Propeller Optimization: Increase diameter and pitch for better thrust efficiency.
- Landing Gear Redesign:
- Helicopter-style legs with flexible damping material (e.g., silicone).
- Motorcycle-style impact plate with dissipating materials.
- Advanced Control System: Move beyond PID to cascaded control, LQR, or MPC.
- Sensor Suite Expansion: Add cameras, small LiDAR, and other perception modules.
- Modular Leg Connection: Make connecting rod detachable for easier maintenance and manufacturing.
- We adopted the wheel design from the project by Michael Rechtin.