Abstract

Computation time is the main factor that limits the application of model predictive control (MPC). This paper presents a fast model predictive control algorithm that combines offline method and online optimization to solve the MPC problem. The offline method uses a k-d tree instead of a table to implement partial enumeration, which accelerates online searching operation. Only a part of the explicit solution is stored in the k-d tree for online searching, and the k-d tree is updated in runtime to accommodate the change in the operating point. Online optimization is invoked when searching on the k-d tree fails. Numerical experiments show that the proposed algorithm is efficient on both small-scale and large-scale processes. The average speedup factor in the large-scale process is at least 6, the worst-case speedup factor is at least 2, and the performance is less than 0.05% suboptimal.

Highlights

  • Model predictive control (MPC) is widely applied in the process control area because of its ability to handle constraints and MIMO systems

  • Many researchers attempted to exploit the special structure of MPC and tailor the two algorithms to speed up the solving process

  • Considering combining explicit MPC and online optimization, the k-d tree is used in this study to design an algorithm that implements fast MPC

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Summary

Introduction

Model predictive control (MPC) is widely applied in the process control area because of its ability to handle constraints and MIMO systems. QPSchur, which is a QP algorithm based on the active-set method, is proposed in [4] and focuses on large-scale MPC Another online active-set strategy is described in [5] for the fast solution of parametric QPs in MPC; this strategy uses the information of the previous QP under the assumption that the QP problem only slightly changes. The PE method uses a table to store the recently searched CRs and combines it with the online method to achieve fast MPC for large-scale problems. We propose a method that combines the explicit MPC and online optimization by using the k-d tree structure to obtain fast MPC for both small-scale and large-scale problems.

Background
Combined Method with K-D Tree
10 20 30 40 50 60 70 80 90 100 Result of PE method
Result of our method
Numerical Experiments
Findings
Conclusion
Full Text
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