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Energy conservation has become one of the key elements of core competitiveness for manufacturing enterprise. On the basis of studying the characteristics of carbon emissions in machining process, the state space model of carbon footprint for machining process is constructed, and carbon footprint transfer matrix is derived. It reveals the mechanism of generation, transmission, and coupling for carbon footprint in machining process. Considering the machining precision constraints and time constraints, the paper researched on optimization control method for carbon footprint of machining process based on dynamic programming to minimize the carbon emissions. Finally, this method is applied in a fracture splitting workshop, and the result shows this method can reduce 10.28% of carbon emissions in machining process. This paper provides theoretical and technical support for energy saving in machining process.

Purpose The optimal control on reassembly (remanufacturing assembly) error is one of the key technologies to guarantee the assembly precision of remanufactured product. However, because of the uncertainty existing in remanufactured parts, it is difficult to control assembly error during reassembly process. Based on the state space model, this paper aims to propose the optimal control method on reassembly precision to solve this problem. Design/methodology/approach Initially, to ensure the assembly precision of a remanufactured car engine, this paper puts forward an optimal control method on assembly precision for a remanufactured car engine based on the state space model. This method takes assembly workstation operation and remanufactured part attribute as the input vector reassembly status as the state vector and assembly precision as the output vector. Then, the compensation function of reassembly workstation operation input vector is calculated to direct the optimization of the reassembly process. Finally, a case study of a certain remanufactured car engine crankshaft is constructed to verify the feasibility and effectiveness of the method proposed. Findings The optimal control method on reassembly precision is an effective technology in improving the quality of the remanufactured crankshaft. The average qualified rate of the remanufactured crankshaft increased from 83.05 to 90.97 per cent as shown in the case study. Originality/value The optimal control method on the reassembly precision based on the state space model is available to control the assembly precision, thus enhancing the core competitiveness of the remanufacturing enterprises.

Aiming at the mechanism of enterprise production equipment accidents, the workshop equipment safety evaluation index structure system based on knowledge management was proposed. And a fuzzy comprehensive evaluation model for workshop equipment security forewarning method was established .The manpower, machine, materials, methods, information and environments in the workshop production site management were predicted. So the workshop production equipments safety can be early warned and effectively treated and the running process was constructed. At last, the simulation shows the feasibility and effectiveness.