Markus Optiz's Partial Exoskeleton Uses a Single Servo to Increase His Father's Reach
A damaged shoulder is given a motorized boost in this clever and thoughtful wearable project.
Artist, maker, and teacher Markus Opitz has extended his work on wearables with a partial exoskeleton — designed to provide shoulder support via a servo driven by an Espressif ESP32 microcontroller linked to a motion-tracking controller on the wrist.
"My father is over 80 years old and has a damaged shoulder which he does not want to have operated on. He can no longer lift his arm very high," Optiz explains of the project's inspiration. "We have tried various exoskeletons for craftspeople, but the devices all bring the same problem: people with disabilities can't put them on themselves!"
That's exactly what Opitz has developed: a partial exoskeleton, designed in such a way that it's easy to put on and take off again without assistance. The heart of the build is a beefy 40kg servo linked to a support arm and designed to take some of the strain off lifting the user's arm. "This device only requires a single servo to lift the arm," Opitz explains. "Lateral movements of the patient's arm are still possible under their own power. The hinge behind the servo makes this possible. The hinge should be positioned as directly as possible above the shoulder joint."
The servo is under the control of an Espressif ESP32 microcontroller, which is linked over Bluetooth Low Energy (BLE) to a wrist-worn device powered by a Seeed Studio XIAO BLE nRF52840 Sense. As the XIAO's integrated accelerometer detects the user attempting to lift their arm, the servo kicks in to provide powered assistance — and lowers again when required.
"So that the device has enough power and my father doesn't have to use smaller 3.7V batteries, I use a battery pack (Bosch) from a Gardena gardening tool," Optiz adds. "Its 18 volts must first be brought [down] to 7.4V, which is compatible with the servo, using an adjustable buck converter. An intermediate capacitor prevents current fluctuations and trembling in the servo. Although the battery is large, it is easy to grip and only needs to be pushed into the holder, where the copper strips ensure contact."
The exoskeleton project is documented in full on Opitz's Instructables page; the wrist controller is detailed in a separate project.