Introduction - Microsurgery: Advances, Simulations, and Applications - page 9

Reference Output

Process

Controller

a)

Output

Reference

Process

Controller

-

Sensor

b)

Figure 1.6 (a) Open-loop control system. (b) Feedback Control System.

In an open-loop system, the output signal is obtained by calculating
the response of the multiplication of the transfer functions of the
controller and process to the reference signal. In feedback control,
the output of the process is measured using a sensor enabling to
calculate the error signal, in these systems the output of the systems
is calculated from the response of the multiplication of the transfer
functions of the controller and process to the error signal. For linear
or linearized systems the controller can be designed to improve
the system stability, reduce the response time, to limit the system
response overshoot or minimizing the steady error [22]. From these
basic control theory fundaments, different control technical areas are
being developed. Among them are Adaptive and Learning Systems,
Discrete Event and Hybrid Systems, Stochastic Systems, Networked
Systems, Control Design, Linear Control Systems, Non-linear Control
Systems, Optimal Control and Robust Control [23].

1.2.2 Diagnostic and Training

This domain of medical robotics comprises systems that are used in
a pre-surgical stage for disease diagnosis or for the surgeon skills
improvement. Recently different organ modeling, visualization and
examination systems have been proposed. An endoscope composed
of a sheath with controlled stiffness and distal end bending and a
iberscope was used for inspection of a swine colon [30]. Augmented
reality systems using sensor fusion of magnetic trackers and
ultrasound probes has been proposed for organ modeling in virtual
reality for endoscopies [31]. Training systems have been proposed