Above is part of a 3D printed harmonic drive with 39:1 gear ratio. It may gear a motor for the shoulder rotation in lieu of a differential. Most notably, The MX-28 servos have a stall torque of 2.5 Nm, requiring an approximate 36:1 gear ratio minimum for one motor to actuate the arm. While, the servos have torque sufficient to lift the arm, their speed and precision may not be sufficient. Geared down from a maximum no load speed of 55 rpm, the shoulder would take approximately half a minute to move through its full range of motion. To track position through more than seven rotations, the servo's precision must be reduced by a factor of four. Presently, MEIOSIS has a functional harmonic drive. However, it is ailed with oscillations during rotations. In MEIOSIS's zeal to print a harmonic drive, the mountings for a DC motor were spaced improperly. While a DC motor could operate at higher speeds (and torques), it would introduce backlash from gearing and would likely be less precise than MX-28 servos. A test next week will further elucidate the tenability of a harmonic drive in the manipulator's design.

If the harmonic drive is inviable, two MX-28 servos could lift the arm. Using two servos would require a differential drive also introducing backlash into the system that would require compensation. After completing MATLAB trajectory kinematics and Python position control, MEIOSIS could explore software control options for gear backlash.