Devlog 5: Aerial Manipulator Design

Over the past couple of days, I completed the aerial manipulator — the robot arm — for the drone. The current design assumes the use of DYNAMIXEL XL430 and XL330 servos, though the final servo mounting is not fully finalized in CAD yet.

Cool Things

• The arm is animated in CAD
• The full manipulator is now integrated into the drone assembly
• I designed and compared two different gripper concepts

The Arm

The arm uses DYNAMIXEL smart servos because they provide positional feedback and include many features that may be useful later.

The current manipulator is a 4-DOF robotic arm with a gripper:

• Base rotation about the Z-axis
• Shoulder rotation about the X-axis
• Elbow rotation about the X-axis
• Wrist rotation about the X-axis
• Servo-driven gripper as the end effector

The arm is intended to be fully 3D printed, allowing for fast iteration and easier replacement of parts if the design changes.

The Gripper

The bulk of the time was spent on the gripper, partly because I designed two different models:

1. A linkage gripper
2. A standard parallel gripper, inspired by this guide: 3D Printed Parallel Gripper for Robotic Arms

Linkages…

The linkage gripper was designed with compactness in mind. It used a gear-driven linkage system and was intended to use TPU fingers to grip rigid payloads.

However, maintaining printing tolerances and designing around the linkage geometry made the CAD extremely messy. The mechanism had too many small pivot points, tolerance-sensitive parts, and potential failure points. Because of that, I could not justify printing and prototyping this version.

The main focus of the project is not the gripper itself. The focus is on testing how the drone handles disturbances induced by arm movement and held payloads. Because of this, I need full confidence that the gripper will work reliably without spending too much project time reprinting and redesigning it.

Parallel Gripper!

Following the Instructables guide, I designed a simpler parallel gripper using a similar bearing, rod, and rack-and-pinion layout.

This gripper uses:

• A 3D-printed main body
• Rigid 3D-printed fingers instead of TPU fingers
• Two identical gear racks
• A central pinion gear
• Linear rods for jaw guidance

The CAD design was much simpler, and I am more confident that this version will produce reliable performance. The parallel gripper should be easier to print, easier to assemble, and easier to debug than the linkage gripper.

Next Things to Do

• Add push/pull rods in CAD to the tilting pods
• Finalize internal electronics mounting
• Evaluate costs for plates and add weights in CAD
• Bias the center of gravity toward the ideal location
• Research and add drone motors and propellers to the BOM
• Add the DYNAMIXEL XL330 mount in the arm