The orange end effector can move in the XOY vertical plane. The effector is pivoted at the end of the yellow connecting rod of a parallelogram mechanism (pink, red, yellow and white). The input motions of the red and pink cranks are provided by red and pink grounded servo motors.
The direction of the effector is kept unchanged by two parallelogram mechanisms (blue and jade).
Unstable positions of the parallelogram mechanisms are prevented when programming the motors.
This video was made based on:
   • 《3D列印》平行連桿手臂測試  

STEP files of this video:
https://www.mediafire.com/file/rg08q3...
Inventor files of this video:
https://www.mediafire.com/file/bmno53...