What is kinematics?

I've used the term kinematics a number of times in this lecture and I haven't really been very clear about what it means. Kinematics is a branch of mathematics that studies the motion of a body or a system of bodies. Kinematics is concerned with the positions of things or the angles between things and is concerned with velocities. These can be translational velocities or they could be angular velocities.

Kinematics is not concerned with forces and moments. That's the business of dynamics. So in kinematics people study mechanisms such as the ones shown here and try to understand how the motion of one body is related to the motion of another body.

I have shown here examples of a number of quite complex mechanisms. In kinematics, is the study of the motion of the various components of these mechanisms. In robotics, we consider two kinematic problems.

First one, in what we discuss in this particular lecture is what's called the forward kinematic problem. And that is given the robot joint angles, what's the pose of the robot's tool tip?

The second problem is called the inverse kinematics. And we're going to discuss that in the next lecture. Given that I know the pose that I want the robot in-defector to have, the problem is to determine what are the joint angles required in order to achieve that. Let me leave you with this quote I really like. It's about kinematics.