FAM-DQ Is Two Quads on a Stick That Can Drive a Screw
Most aerial manipulators fight their own base. Tilt the multirotor and the arm moves. FAM-DQ (arXiv August 13) is a different shape: two quadrotor modules on the ends of a carbon-fiber tube, an end-effector hanging off a gear-driven servo, and passive joints so the props can point without dragging the tool.
Xuwei Yang, Ruoyu Ren, and Ziqian Guo built it for high-torque contact — valve work, bolt tightening — without a heavy tilt-rotor cage. The prototype masses 0.447 kg. Docked to a torque sensor, it measured 1.019 N·m, or about 2.28 N·m/kg.
How the wrench is made
Each module is four 1204 / 5000 kV motors on 3015 props, with its own flight controller and battery. A wireless link of about 10 ms carries thrust commands from a central controller. Module-1 is rigidly tied to the tube in one axis so it can yaw the frame. Module-2 has extra passive joints so its thrust can swing more freely.
The tube is the lever. Thrust at the tips becomes torque at the tool. The servo rotates the end-effector around the rod so the bit can point at the work without asking the whole airframe to pitch.
What they flew
Indoors, under motion capture:
- A 0.75 m radius circle in the XY plane with the end-effector held at a fixed attitude. Position error stayed inside ±0.05 m. Attitude wandered inside ±1.5°.
- Hover attitude tracking: 20° sinusoidal roll, 30° yaw, then both together. Position held within ±0.08 m (x), ±0.05 m (y), ±0.02 m (z).
- An M8 × 24 mm socket-head screw. The platform lined up the bit, pushed down, and turned until the screw went into a fixed workpiece.
The paper is careful about what it did not do. All of this is indoor, mocap-backed, and quasi-static when they measure peak torque. Future work they list is a stronger mechanism and controllers for messier contact.
A Human’s Take
I am here for the lever, not the CAD adjectives. Two cheap quads and a long tube is a readable way to buy torque without another tilt actuator. The screw video is the receipt I wanted. The next question is outdoor wind and a stuck fastener that does not sit on a lab plate.