How do I model a simple robot arm as a plant?. I know how to model motors but, I think, controlling individual motors may not be enough; and in order to control the the arm as a plant I need to model it as a plant. In the block diagram below my trouble is in finding the hardware model of the robot arm.
Each joint of your robot is one motor. They are coupled though kinematic relations and dynamic physics.
One straight forward way is to derive these so called 'equations of motion' using the euler-lagrange formalism. Once you obtained your equations you can create for example a Matlab function to solve them dynamically.
But back to the modelling part, check out the slides in Dynamic model of robots: Lagrangian approach, by Prof. Alessandro De Luca .