# How to move robotic arm in straight line

So here is my problem. I need to grab an object with my robotic arm, but I don't know the position of the object. The only thing I know is the angle between object and gripper. You will maybe better understand better from this image. So my question is, how do I do that my robotic arm will be approaching the possible position of object in straight line? I tried inverse kinematic but it didn't work, because I don't know position of the object although I tried set the position of the object to end of the gripper. So I think IK is not the right way.

• It seems you're asking two questions. First, how the robot knows that it is approaching an object. The answer is you need some sort of sensors. Second, how to move the end-effector through straight line. The answer is first compute the equations that relate the position of the gripper to the joint angles. – CroCo Jan 28 '18 at 9:45
• How many DoF is your arm? Do you have an arbitrary vector in which you want the arm to travel, or is the vector formed by the last link as in your diagram? – Ben Jan 28 '18 at 19:57

1. the angle $\alpha$ is given by some sensor