Study on Loading-Machine Production Scheduling Algorithm of Forest-Pulp-Paper Enterprise

Through the needs of Loading-Machine storage scheduling in forestry-pulp-paper production logistics intelligent distribution system, analysis the Loading-Machine scheduling model of problems and improvement measures, put forward Loading-Machine intelligent production scheduling algorithm, based on ensuring the feasibility of scheduling, scheduling to rationalization, equalization, execute only, production process optimization, and realize the Loading-Machine intelligent production scheduling through the computer programming.


Introduction
One of the most important problems in the production logistics intelligent distribution system of Forest-Pulp -Paper enterprise is to carry out the Loading-Machine production scheduling .The main production of wood in the workshop is completed by the Loading-Machine, and the pulp package is mainly carried out by the stacker or forklift.Therefore, it is necessary to realize the automatic scheduling of the handling equipment, and to ensure the feasibility of scheduling, so as to realize the scientific management of the Loading-Machine.Scheduling problem is a typical combinatorial optimization problem, which is an important research field of CIMS (computer integrated manufacturing).To determine the storage strategy and location assignment rules provide a strong guarantee for the calculation of these transportation production.
At present, the loader management approach is the administrator of verbal work instruction or to an operator or from the storage list of operators according to their own preferences to decide what to do , operator can find the target position for timber; operation chaos, low efficiency, error rate is high, often allowing out -trucks for transporting logs for a long time waiting.There are a lot of waste and unreasonable.
Therefore, how to realize the automatic scheduling of the loader work becomes a problem needs to be solved.Due to scheduling object is loader (a device needs operating security), according to the regulations, still need to operate on the loader, so instructions need to be sent to the loader operator.
The loader scheduling problem to solve is: how to according to the production plan, timber delivery order, inventory plan from various departments of the use of timber demand, the automatic generation of the loader operating instructions, how to assign tasks to different loading machine to carry out the instructions, how to deliver necessary wood when necessary loading machine, send work order at what moment, how to determine the operation order, how to ensure the mixed order can arranged well and deadlock phenomenon is not appear, how to according to the actual situation of change auto released work instructions, how to monitoring perform tasks, how to ensure wrong order don't be execution.

Description of Scheduling Problem
Regarded the wood or wood chip as a workpiece, regarded the loader as a special processing of wood, each of its handling process as a working process, then the loader scheduling can be understood as a kind of special department scheduling job.The department scheduling problem (Job-Shop Scheduling Problem, referred to as JSSP) can be expressed as: have n-kinds of wood {J 1 , J 2 , J 3 , L, J m } to be processed in m-machines {M 1 , M 2 , M 3 , L, M m }, each kind of wood contains a process composed of multi-channel collection {O i j } , which O i j indicates that the j process of the i wood industry, wood processing order is given in advance, processing time of each process may fluctuate, but the average available, in addition to the machine and wood have some basic constraints, such as: each machine only have once wood processing; the process begins, it can not be interrupted; after the permit for timber processing on other machines, it can be return to the original machine and so on.
The problem to be solved in the job scheduling is to determine the processing sequence of each machine (loader and other shared machines), allocate the resources reasonably, and make the scheduling result meet the preset schedule.
For non-deterministic problem of complete polynomial can be solved by exhaustive method.Because of the complexity of the algorithm and the amount of input data is exponential relationship, so the calculation of the time with the complexity of the problem of exponential growth, and ultimately will not be able to calculated .
Verify the feasibility of a loader job scheduling , which is a P problem.The P problem is a decision problem that can be solved in polynomial time(A decision problem is a question that needs to be answered "yes" or "no" ).But if it is the best solution to the job scheduling, it is a NP-Hard problem (NP problem).The NP problem is the problem that the "guess" result can be verified in polynomial time.

Loading-Machine Scheduling Objectives
The goal of the loader job scheduling is: (1).Instructions deliver necessary loader log when necessary (chip) to the position.Therefore, to select the appropriate instructions to send in time, the appropriate allocation of resources.
(2).Executable job only.That is to say, the loader has the right to execute the first job instruction and does not have the right to choose which job to perform.
(3).The loader movement target position calculation (location calculation) to achieve the comprehensive optimal storage strategy.The calculation results to the exact location, only, and not to crash phenomenon.
(4).The total operating time is the shortest, or that all the work should be taken into account in advance to the production of the work out of the shortest distance between the carrier motion.
(5).Personnel and equipment utilization is the largest, the average delay time is the shortest, and the waiting time is the shortest.
(6).The scheduling system is easy to operate, easy to accept and understand.

Disjunctive Graph Model
Based on the mathematical model of the disjunctive graph model of loader scheduling problem in the analysis of the available graph represented.Disjunctive graph proposed by Roy and Sussman in 1964, after the Job Shop scheduling problem instance description has been widely studied and applied.Disjunctive graph W  (M , B, H ) is defined as follows: M is the vertex set, set corresponding to all processes (including two virtual procedure, respectively, the beginning and the end); B is a directed edge set, said sequence constraints of each process with a wood between the lines in the figure represented by one-way; H is a disjunctive edge the collection, it is an undirected edge set, said mutex relationship is processed in the same machine process, with a dotted line in the figure.Disjunctive edge set is divided into sub set H  H 1 U H 2 ULH k , which H k indicates that the K machine procedures set.In-out warehouse operation scheduling problem disjunctive as shown in Figure 1.

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Conclusion
Through the study enterprise Loading-Machine Production Scheduling Algorithm, we can analysis the Loading-Machine scheduling model of problems and improvement measures, and use Loading-Machine intelligent production scheduling algorithm, realize the Loading-Machine intelligent production scheduling through the computer programming.

Figure 1 cis
Figure1have 3 parts, multiple machines disjunctive graph examples, the machines here include: loading machine, electronic weighing (virtual machine), log chain feeder, peeling machine.The logs andpurchased wood chip processing includes 4 steps (production library, electronic weighing, input, processing), net tablet contains 4 Figu