The document proposes an override control system consisting of two anti-reset windup controllers, a common actuator, and a limiter surrounded by pre and post filters. The prefilter inverts the post-filter. The limiter defines the desired limit on the override variable and its setpoint. In contrast to standard systems, the proposed structure achieves the override variable response practically without overshoot. The postfilter parameters are adjusted using a defined procedure. Simulations demonstrate the ideas, and experiments on a thermal plant confirm the solution's validity.

1. PROCESS CONTROL
Subject:
Chien Tran Minh
Nghia Le Van

2. Design and Tuning of PID Override Control
System Based on Signal Filtering
ABSTRACT: The proposed override control system consists of two anti-reset windup controllers,
common actuator and a limiter, surrounded by pre and post biproper filters. Prefilter is inverse of
the post-filter. The desired limit on the override variable and its set-point are defined by output of
the limiter. Signal selector is not applied in the proposed structure. Other characteristic feature of
the proposed solution, compared to standard one, is that the override variable response is
obtained practically without overshoot. Procedure for adjusting parameters of the postfilter are
defined and illustrated in detail. Simulation results are used to demonstrate the basic ideas.
Experiment on a laboratory thermal plant with noisy measurements is used to confirm validity of
the proposed solution.
Keywords: PID control; Override control; Constraints; Dead-time compensation; Tuning

3. I. INTRODUCTION
Figure 1. Block diagram of a standard override control system: primary
controller Cp and override controller Co connected to the common
actuator AC trough the min/max selector.
𝑮 𝒑 𝒔 =
𝒆−𝟎.𝟐𝒔
𝒔
𝑮 𝒐 𝒔 =
𝟏𝟎𝒆−𝒔
𝟏𝟎𝒔 + 𝟏

4. I. INTRODUCTION
Figure 1. Block diagram of a standard override control system: primary
controller Cp and override controller Co connected to the common
actuator AC trough the min/max selector.
𝑮 𝒑 𝒔 =
𝒆−𝟎.𝟐𝒔
𝒔
𝑮 𝒐 𝒔 =
𝟏𝟎𝒆−𝒔
𝟏𝟎𝒔 + 𝟏

5. I. INTRODUCTION
Figure 2. Control signals up (dashed), uo (dotted) and resulting u (solid)
of override control system in Fig. 1, with selector of a min type.

6. I. INTRODUCTION
Figure 3. Set-point (dashed) and process output (solid) responses of
override control system in Fig. 1. Standard override controller Co can not
prevent appearance of overshoot in the override variable yo.

7. II. PROPOSED STRUCTURE
Figure 4. Proposed override control system: primary controller Cp and override
controller Co connected to the common actuator AC. Inside limits u(t)≡up(t) and
override controller Co is inactive. Fr(s) is a biproper post-filter with Fr(0)=1.

8. II. PROPOSED STRUCTURE
Figure 4. Proposed override control system: primary controller Cp and override
controller Co connected to the common actuator AC. Inside limits u(t)≡up(t) and
override controller Co is inactive. Fr(s) is a biproper post-filter with Fr(0)=1.

9. II. PROPOSED STRUCTURE
Figure 5. Set-point (dashed) and process output (solid) responses of the
proposed override control system in Fig. 4. Dot line presents the desired limit
for yo.

10. Reference
• Design and Tuning of PID Override Control SystemBased on Signal Filtering,
Aleksandar I. Ribić, Miroslav R. Mataušek, International Symposiumon
Industrial Electronics INDEL 2014, Banja Luka, November 06-08,2014

11. The End
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