Robot Kinematics: Forward and Inverse Kinematics

Forward Kinematics

A manipulator is composed of serial links which are affixed to each other revolute or prismatic joints from the base frame through the endeffector. Calculating the position and orientation of the endeffector in terms of the joint variables is called as forward kinematics. In order to have forward kinematics for a robot mechanism in a systematic manner, one should use a suitable kinematics model. Denavit-Hartenberg method that uses four parameters is the most common method for describing the robot kinematics. These parameters ai1, α −,1idi and θ the link length, link twist, link offset and joint angle, respectively. A coordinate frame is attached

to each joint to determine DH parameters. Zi axis of the coordinate frame is pointing along the rotary or sliding direction general manipulator.

Inverse Kinematics

The inverse kinematics problem of the serial manipulators has been studied for many

decades. It is needed in the control of manipulators. Solving the inverse kinematics is computationally expansive and generally takes a very long time in the real time control of manipulators. Tasks to be performed by a manipulator are in the Cartesian space, whereas actuators work in joint space. Cartesian space includes orientation matrix and position vector. However, joint space is represented by joint angles. The conversion of the position and orientation of a manipulator end effector from Cartesian space to joint space is called as inverse kinematics problem. There are two solutions approaches namely, geometric and algebraic used for deriving the inverse kinematics solution, analytically. 

Teach Pendant

A Control Box For Programming The Motions Of A Robot. Also Called A "Teach Box," The Robot Is Set To "Learning" Or "Teach" Mode, And The Pendant Is Used To Control The Robot Step By Step. Teach Pendants Are Typically Handheld Devices And May Be Wired Or Wireless.