Research On Key Technologies Of Adaptive Production Control In Discrete Manufacturing Workshop

With the economic globalization and the fierce market competition,the survival environment of manufacturing enterprises is more and more turbulent.On the one hand,the demand for flexibility and production capacity of manufacturing systems continues growing,on the other hand,the predictability of manufacturing processes continues declining.Therefore,production managers are required to make timely and accurate response to the dynamic and changeable manufacturing environment.The production control system is an important method to optimize operation and improve the performance of the workshop system.The dynamic parameters of the workshop system or the structure of the system model are often changed because of the changes of the actual operating conditions and the internal and external conditions of the workshop.Therefore,it is impossible for conventional controllers to obtain better control quality when considering production control problems from the perspective of system theory,and adaptive control is just the suitable method for controlling the workshop manufacturing system with certain degree of uncertainty.This paper focuses on the production-operation-decision problem of discrete manufacturing shop floor.From the point of view of cybernetics,the adaptive control of production capacity is taken as the main line,the main research work is as follows:1.A framework of adaptive production control system based on control theory is proposed.The adaptive production control system consists of three key modules: production controller,performance analysis and optimization,and workshop operation decision.The system adopts the centralized event-driven mechanism to link the production control strategy module and the workshop operation decision module,and uses the distributed event-driven mechanism to construct the workshop operation decision module,which can satisfy the complex dynamic and changeable workshop operation environment.An adaptive control strategy based on driving error is designed to improve the performance of the workshop system and reduce the frequency of the controller.2.Based on the idea of flow rate control,a production control system model of discrete manufacturing workshop is established in the continuous time domain,in which a two-layer feedback control link is integrated.In the time domain,the dynamic characteristics of the production control system with different parameters are analyzed in detail.The key parameters of the system,such as WIP(Work-in-Process,WIP),production lead time and production capacity adjustment time,are related to the damping ratio and natural frequency in the control theory.3.The self-adaptability of cybernetics is embedded in the parameter design of production controller.The feedback regulation principle of neuroendocrine system is analyzed,and the function of hormone regulation mechanism is studied.On this basis,double closed-loop controllers with backlog and WIP variables as controller parameters are designed,and the correlation between controller parameters and performance indicators of shop floor system is constructed.4.The performance of production control system of discrete manufacturing workshop under disturbed state is analyzed.The internal structure of the discrete manufacturing workshop is analyzed,and a self-organizing production mode is proposed,which simplifies the production control process and defines the order flow matrix to represent the internal structure of the workshop.Taking WIP as the state feedback variable of the system,the state feedback control law based on production capacity adjustment time and sampling period is designed.The state equation and output equation of workshop system are established in discrete time domain with order flow matrix.The eigenvalues of state matrix of discrete manufacturing workshop are solved by state-space method,and the performance of production control system is evaluated.5.The decision-making mechanism of workshop operation is designed,and an adaptive production control experiment platform is built.The objective function of workshop operation decision is defined.The objective function considers the production rate,cost and the key performance index of workshop,and designs the decision support system of workshop operation.The intelligent unit controller is built by embedded industrial computer,and then the distributed adaptive control experimental platform is built.The adaptive production control management platform is developed,which realizes the effective link between control strategy and execution decision.The key technologies proposed in this paper are verified.