Now the design we have has the 4 DOF (Base, Shoulder, Elbow, Wrist), there is no problem in moving the arm in a curved manner but the main problem arises in straight-line motion. I'm unable to fid=nd the solution for that. the main concern is which at least 2 motors I should move. Hoping For Solutions Here. Regards.
You need inverse kinematics. Which refers to calculating the joint angles so that the robot will reach a particular pose.
You can not simply move from point A to point B.. You will need to use inverse kinematics to calculate all the positions the arm will pass thru to form a straight line.