Model Predictive Control
Assembly Line
Deep learning-based model predictive control for real-time supply chain optimization
This paper presents a deep learning-based model predictive control (MPC) method for operational supply chain optimization in real time. The method follows an offline-online procedure. In the offline phase, the state-space model of a supply chain system is developed and the MPC problem for supply chain operation is formulated. Then, the MPC problem is solved for a set of initial states to obtain the corresponding optimal inputs. A deep neural network (DNN) is built and trained by using the optimal state-input pairs as training data to approximate the optimal MPC law. In the online phase, the DNN controller is employed to provide real-time decisions. In this paper, the MPC problem for supply chain operation is formulated as a mixed-integer linear program. A deep learning-based MPC method is proposed to accommodate time delays in the system. Moreover, a heuristic method is proposed for feasibility recovery with the binary decision variables taken into account. The training set for the DNN controller contains two subsets, one formed from MPC solutions corresponding to random initial states, and the other formed from optimal state-input pairs in closed-loop simulations. The deep learning-based MPC is validated via two case studies through closed-loop simulation. The first case study involves a linear MPC, and the second case study involves a more complicated mixed-integer linear MPC. Results show that deep learning-based MPC can achieve a high accuracy in approximating the MPC decisions and a significant reduction in the online computation time. Compared with MPC, the average performance loss of using deep learning-based MPC in the two cases is 0.43% and 1.8%, respectively.
🎛️ Optimal control of the part mass for the injection molding process
Injection molding is one of the most important processes to manufacture plastic goods. During the long production times, process variations might lead to a varying product quality. Therefore, in the state of the art, the machine variables of injection molding machines (e. g. the barrel temperature and the screw speed) are controlled to suppress these variations. However, the influence of changes of the raw material on the part quality cannot be systematically suppressed with state-of-the-art controllers. In this work, a novel control concept is proposed where the part mass is controlled instead of the usual machine variables. The control strategy is based on an estimation of the plastics mass in the mold. In order to account for the system nonlinearities, a model predictive control strategy is developed for both the filling and the holding-pressure phase. The feasibility and the benefits of this proposed part-mass control strategy is evaluated by a series of measurements on an electric injection molding machine.