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The Self Organizing Fuzzy PID Controller


									The Self Organizing Fuzzy PID Controller

                   老師:曾慶耀 教授

   Conceptual development of a SOF-PID controller
    and applies it to a non-linear revolute-joint robot-
   SOF-PID controller produced a smaller steady state
    error and a negligible overshoot compared to the
    SOF controller, the PID controller and the Self-
    tuning controller.

   A fuzzy controller can act as a master controller
    readjusting the PID gains at the actuator level
    to compensate for the PID’s short falls.
   the rule-based fuzzy PID is a non-learning
    controller, and the difficulty with this type of
    controller is that the rules are pre-written in the
    rule base block copying the experience of a
    human operator.
   The way the SOF-PID controller works is that, the
    PID gains are tuned initially using conventional
    tuning methods.
   fuzzy logic control theory uses linguistic statements
    in place of numerical values.
Design Aspects of SOD-PID Controller

   Further reduction in the steady state error, overshoot
    and rise time is required
   Retuning the gains Kp,Ki and Kd, improves some
    part of the output response and worsens the other
Structure of the SOF-PID controller

 Figure 1 shows the structure of a Single-Input
Single-Output SOF-PID controller.

 Kpi=Kpi-n +P (3)
 Kii=Kii-n+P  (4)
 Kdi=Kdi-n+P  (5)
 Kp=Kp+Upi*K1 (6)
 Ki=Ki+Uii*K2  (7)
 Kd=Kd+Udi*K3 (8)
DC motor dynamics of the robot-arm

   A second order differential equation was used to
    present the dynamics of a DC motor and load
Experiments for a step input

   Experimental results of the SOF-PI0 controller
    applied to a non-linear revolute-joint robot-am are
    studied and compared with the SOF controller, the
    PID controller and the Self-tuning controller.
   For the step input two sets of experiments were
    carried out using the SOF-PID controller,labelled
    as method I and method II.
The experimental results (I) - methodI

   The PID gains were tuned initially, without the
    SOF master controller. Firstly, large values of KP
    were chosen and gradually Kp values were
    decreased until the time the process output
    overshoot was minimized.
The experimental results (II) - methodII

   The process was first controlled using Kp only. The
    PID gain Kp, was slowly increased until continuous
    oscillations resulted.

    the objectives for the SOF-PID controller were: to
     achieve a good damping around the setpoint; to
     produce no overshoot as the setpoint being
     approached, and to reduce the steady state error.

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