# Choose the structure of the dynamic model for the generalized equations of motion of the robot

I ask the robotics specialists for help as I am a little confused.

I have two subsystems which are shown in the picture below:

One of them is a system of stable and controlled differential equations of motion for robot.

Second is a block that implements a Forward Kinematic $$f(\theta)$$ from a signal entering its input.

$$\theta,\Phi,\phi$$ - position of drives, positions of end-effector from dynamic model and Forward Kinematic data, $$u(t)$$ - control signal.

I came across this article and a diagram from it.

Hybrid Open-Loop Closed-Loop Control of Coupled Human-Robot Balance During Assisted Stance Transition with Extra Robotic Legs

Task: choose the structure of the mathematical model in such a way that $$\phi=\Phi$$. In the above diagram, I am confused by the fact that a block of direct kinematics is used to estimate the angular position of the robot, and, generally speaking, this mechanical coordinate should be available through the equations of motion.