An elbow exoskeleton for haptic feedback made with a direct drive hobby motor

A direct-drive motor is one of the simplest mechanisms to cause a mechanical joint to move. Specifically, a brushless direct current (BLDC) motor with no gearing produces a low parasitic torque due to its backdrivability and low inertia, which is ideal for some applications such as wearable systems. While capable of operating with a higher power density than brushed motors, BLDC motors require accurate position feedback to be controlled via vector control at slow speeds. The MotorWare™ library from Texas Instruments (TI), which is designed to run with a C2000 microcontroller, is written to run BLDCs. However, the code was written to run the motor continuously with an incremental encoder and requires further engineering to be used at low speeds, for example, in an exoskeleton. In this paper, we provide custom code to modify the software provided by TI so that the motor can provide a controlled torque at low speeds, code to enable the microcontroller to communicate with a computer for high-level commands and data storage, and procedures to build the hardware for a simple arm exoskeleton that can provide haptic feedback to the wearer. The supplementary design files included are: 1) CAD_Files.zip, 2) CCS_codes.zip, 3) Frame_drawings.pdf, and 4) Processing_codes.zip.