My senior design project was to design, build and control a 2.5DOF manipulator with a pneumatic gripper. This video shows stable control without the gripper attached. We used cubic polynomials for trajectories and adjusted the desired trajectory as the final desired position was changed (as the mouse was moved)
See the senior design proposal and some CAD pictures here:
https://drive.google.com/file/d/1jhpwhYcdwSQPc9HZFSuMkm-_aBhhXmyW/view?usp=sharing