Colossal Tentacle Robot Wows EMF Camp Crowds

Every robot has a purpose, which is why we see so many different varieties. Even within the same general category, like “robot arms,” there are huge variations in layout and movement. A SCARA (Selective Compliance Assembly Robot Arm), for example, has very little in common with a delta robot arm. One of the strangest types is the oblique swivel joint robot arm, which has some very unusual properties and motion characteristics. To entertain attendees at EMF Camp, James Bruton built what may just be the largest oblique swivel joint “tentacle” robot arm on the planet.

This style of robot is actually very easy to understand once you see it in motion. Each joint is rotational, but mounts at an angle (usually 30 or 60 degrees). That angle forces the rest of the arm to rotate around a plane that is oblique to the central axis of the preceding section. When the robot contains multiple joints of this type, the resulting kinematics are strange and intriguing. This style of robot has limited practical utility, but always catches attention and that made it perfect for Bruton to exhibit at EMF Camp.

Bruton’s robot is massive and reaches a maximum height of around 2.5 meters — and that’s without an end effector attached. It has three joints, which is enough to show off the concept without making the size (and cost) cross the line from concerning to stratospheric. It rides on a trio of oversized omni wheels, so it has complete directional freedom. And at EMF Camp, Bruton attached a servo-driven cable-actuated tentacle-style mechanism with a gripper for the end effector.

Constructing all of that was a truly gargantuan undertaking, as none of the required parts (aside from things like bearings and fasteners) were available off-the-shelf. Bruton made each joint out of CNC-cut plywood and 3D-printed components. The joints are essentially massive rings with an outer track of gear teeth. A geared DC motor rotates those via a couple of intermediary gears. In total, the gears provide a reduction of 1600:1 and that let Bruton actuate the heavy robot with relatively small motors.

A series of Arduino Mega 2560 boards control those motors through ODrive modules. The first Arduino resides in the remote control and communicates with the robot’s primary Arduino via a direct Wi-Fi connection enabled by ESP32 development boards. That primary Arduino then communicates with an additional Arduino in each joint through a CAN bus. In theory, that makes the robot infinitely expandable; Bruton could keep adding more and more joints if he wanted. The Arduino in each joint then controls that joint’s motor and monitors its position.

This seems to have been a big hit at EMF camp, where it was quite the spectacle. Bruton designed the robot with intuitive controls so anyone could give it a try, including young kids. We’re confident that helped Bruton accomplish his goal of fostering interesting in engineering and robotics.