Over-engineered robotic scalp scraper knows every move

These inexpensive corded arm head massagers are perfect for giving your scalp a nice and relaxing massage. But these are portable tools that require the user to manipulate the massager themselves or convince a partner to perform the task. David McDaid decided the experience would be much more enjoyable if a robot did the hard work, so he built this Stewart Platform Head Massager.

A Stewart rig is a dexterous manipulator often used with robotic effectors or to steer equipment. The standard configuration requires six linear actuators, each with universal joints at both ends. The actuators mount between two plates in an arrangement that gives the top plate six degrees of freedom (DoF): pitch, roll, yaw, and linear motion in each of three spatial axes. A Stewart platform is perfect for this application, as it allows the robot to move the head massager in different ways that mimic manual movement.

McDaid created its own Stewart rig using an Arduino Mega 2560 board and six AX-12A servos instead of the usual linear actuators. The use of servos affects the kinematics to some degree, but not enough to be a problem in an application like this that doesn't require a lot of precision. McDaid designed their own custom PCB for this project, which is a shield for the Mega that simplifies the electrical connection. This power comes from a hobby LiPo battery with an XT60 connector. The mechanical parts, including the servo arms, frame, and massager mount, were all designed in Fusion 360 and then 3D printed.

The finished robotic head massager is capable of performing many different movements, ensuring total relaxation with minimal physical exertion.