Model Predictive Controller

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Model Predictive Controller

• Emad Ali
• Chemical Engineering Department
• King Saud University

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Review

• Major Control Elements
• Instrumentation
• Control algorithm
• Process model

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Review

• Control Algorithms
• Classical
• PID cascade override ratio split range
  inferential
• Advanced
• Adaptive control
• Fuzzy logic control
• Internal model control
• Optimal control
• Neural network control
• Globally linearizing control
• Model predictive control

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Benefits of MPC
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Industrial MPC Technology

• IDCOM (Identification and Command)
• Model type Impulse response
• Optimization is solved by QP approach
• DMC (Dynamic Matrix Control)
• Model type Step response
• Optimization is solved by LP approach
• OPC (Optimum Predictive Control)
• Use step response solves LP problem
• Model building controller design and simulation
• tasks are carried out on PCs
• PCT (Predictive Control Technology)
• Combines the aspects of IDCOM and DMC
• HMPC (Horizon Multivariable Predictive Control)
• For proprietary reasons information is
  unavailable

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Multivariable vs. Multi-loops
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General Application Concept
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Receding Horizon Concept(Prediction)
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Process Model
Model
Y(k/k) M Y(k-1/k) S Du(k-1/k)
Y(k/k) y(k/k) y(k1/k) y(kn-1/k)
Y(k-1/k) y(k-1/k) y(k/k) y(kn-2/k)
Prediction
Y(k1/k) MP Y(k/k) SP DU(k/k)
Y(k1/k) y(k/k) y(k1/k) y(kP-1/k)
DU(k/k) Du(k/k) Du(k1/k) Du(kM-1/k)
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Process Model Correction

• Output Feedback

Y(k1/k) Y(k1/k) N yp(k)-ym(k)
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Methods of Solution
1. Algebraic Equation
R(k1)Y(k1) MP Y(k) SP DU(k)
2. Linear Programming (LP)
R(k1)-Y(k1) R(k1)-MP Y(k) SP DU(k)
0
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Methods of solution
3. Quadratic Programming
min R(k1)-Y(k1)T G R(k1)-Y(k1) DUT(k) L
DU(k) DU(k)
4. Constrained QP
min R(k1)-Y(k1)T G R(k1)-Y(k1) DUT(k) L
DU(k) DU(k)
Ul U Uu DUl DU DUu
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Methods of solution
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Tuning Parameters
Output weights
Input weights
Prediction horizon
Control horizon
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Tuning Guidelines
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Generating Step Response Model
1. Step testing
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Generating Step Response Model
2. PBRS Testing
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Step Vs. PBRS
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Implementation requirement

• DCS system
• Personal Computer
• Step response model
• Tuning

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Special Features of MPC

• Feed-forward capability
• Inferential control
• Output Constraints

Y(k1/k) M Y(k/k) S DU(k/k) W d(k/k)
Y(k1/k) M Y(k/k) S DU(k/k) Z(k1/k)
CY(k1/k)
Yl (k1) Y (k1) Yu(k1)
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Special Features of MPC

• Variable set point
• or constraints

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Simulation Example
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F200/C2 P100/P2
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P100/C2 F200/P2
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Thank You

• Questions