CN100394417C - Regular scheduling method with state and performance feedback and its scheduling system - Google Patents

Abstract

The present invention relates to a rule scheduling system with state performance feedback and a scheduling system thereof, which can reduce the delay time of work pieces and improve the utilization ratio of equipment. On the basis of the existing regular scheduling, the demand quantity of equipment, the demand tendency of equipment and the average relaxation time of the work pieces are introduced and used as the state feedback of system operation, the machining time of equipment, the machining time of the work pieces, the waiting time of the work pieces and the advance/delay time of the work pieces are introduced and used as the performance feedback of system operation, and a feedback scheduling rule is formed. Scheduling objective function is introduced, and an iterative optimized scheduling method is proposed. A sequence planning tree of an expansion process is defined and is used for denoting the flexibility of process sequence planning of the work pieces and the flexibility of machining paths of the work pieces, the decision space of the scheduling system is enlarged, and the enlarged space is favorable for forming a better scheduling scheme. The scheduling system is composed of a central control apparatus, a loading and unloading station, a system buffering station, an automatic orbit trolley, production equipment, etc. During each time of decision making, the central control apparatus calculates the priorites of the idle equipment and the work pieces to be machined according to the feedback scheduling rule, the idle equipment having a high priority is selected to machine the work piece having a high priority to be machined.

Description

Rule scheduling method with state performance feedback and scheduling system thereof

Technical Field

The invention belongs to the technical field of production scheduling and management, and particularly relates to a regular scheduling method with state performance feedback and a scheduling system thereof.

Background

According to the optimal production technology, the production capacity of the bottleneck device determines the production capacity of the whole system and determines the operation performance of the system. The equipment processing capacity of the produced production system is fixed and unchanged, and the logistics in the production system can be changed and the requirements of workpieces on the equipment production capacity can be adjusted only through a proper scheduling system and a proper scheduling method, so that the bottleneck equipment effect of the system is reduced or eliminated, and the running performance of the whole system is improved.

The scale of the production scheduling problem increases with the increase of the number of production equipment, the variety and the number of workpieces and the number of process plans, and the computational complexity of the scheduling problem exponentially increases with the increase of the scale of the scheduling problem. Therefore, for a large-scale production system with complex logistics situation, a rule-based scheduling method is generally adopted to complete real-time scheduling and control of the production system.

A scheduling rule is a sort method used to determine the competing priorities of the production equipment and the workpieces to be processed in the production system. When the equipment is idle, or a new blank enters the system, or one process of the workpiece is finished, a decision moment is entered, at the moment, the scheduling system determines which process of which workpiece is allocated to which equipment for processing according to the scheduling rule, so as to implement scheduling and control on the production process. Under the control of the scheduling rules, the sequence of processes assigned to each equipment process in the production system and the start and end times of each process of the process are referred to as the solution of the rule scheduling.

At a certain decision moment, if a plurality of processing devices in the system can finish the processing of the same workpiece to be processed, the production device with the highest priority is selected to finish the processing task. Similarly, at a certain decision time, if a plurality of workpieces are waiting to be processed in the system, the workpiece to be processed with the highest priority is selected first for processing. Through the scheduling rule, the priority ranking of the production equipment and the workpieces to be processed in the production system can be realized. Different scheduling rules can generate different sequencing results, so that the flow process of workpieces in the production system can be changed, and the purpose of controlling the operation process and the operation performance of the production system is achieved.

Generally, the regular scheduling has the advantages of simplicity and feasibility, has the dynamic scheduling capability, and is particularly suitable for scheduling of a complex production system with more random interference factors in the production process. See: baker, A below of factory control alcohols and can be implemented in a multi-agent hierarchy: dispatching, scheduling, and pull, J.of Manufacturing Systems, 1998, 17 (4): 297-320.

The disadvantage of regular scheduling is that it does not guarantee an optimal solution, and in many cases even a satisfactory solution, mainly because: regular scheduling lacks scheduling objective functions and optimized control means for the objective functions. Once the scheduling rule is determined, the sequencing methods of the production equipment and the workpieces to be processed are determined, so that the rule-based scheduling cannot adjust the sequencing methods of the production equipment and the workpieces to be processed in real time according to the system running state and running performance, cannot optimize the production process according to the actual running condition of the system, and particularly cannot optimize the production process aiming at the current scheduling objective function. On the other hand, the existing regular scheduling does not fully utilize the process sequence planning flexibility of the workpieces and the processing path flexibility of the workpieces, so that the decision space is small, the number of available scheduling schemes is small, and a better scheduling scheme is not favorably formed.

Disclosure of Invention

The invention aims to provide a regular scheduling method with state performance feedback, which can overcome the defects, can adjust the sequencing methods of production equipment and workpieces to be processed in real time according to the running state and the running performance of a system, can optimize the production process according to the actual running condition of the system, and particularly optimizes the production process aiming at the current scheduling objective function; the invention can also make full use of the process sequence of the work piece to plan the flexibility and the processing path flexibility of the work piece in the scheduling process, and form a better scheduling scheme; the invention also provides a scheduling system for implementing the method.

The invention provides a regular scheduling method with state performance feedback, which sequentially comprises the following steps:

(1) a scheduling objective function Obj is formulated according to the production task;

(2) respectively appointing a scheduling rule r for a production device k and a workpiece i_M，k、r_J，i，k＝1，2，......，k，i＝1，2，......，N；

(3) Constructing an iterative feedback scheduling rule r_cM，k、r_cJ,i：

r_cM，k＝r_M，k+p_k1R_k+p_k2D_k+q_kT_k

r_cJ，i＝r_J，i+p_it_s，i+q_i1t_p，i/t_w，i-q_i2t_d，i

Wherein p is_k1、p_k2Is the state feedback coefficient of device k, q_kAs a coefficient of performance feedback, p, for device k_iIs a state feedback coefficient, q, of the workpiece i_i1、q_i2The performance feedback coefficient of the workpiece i is obtained; r_kIs the demand of the equipment k, D_kIs the demand trend of the equipment k, T_kThe processing time of the device k; t is t_s，iMean relaxation time, t, of workpiece i_p，iIs the machining time, t, of the workpiece i_w，iIs the waiting time, t, of the workpiece i_d，iDelay time of the workpiece i; wherein,

equipment demand R_k(t) is calculated from the following formula:

R_k(t)＝|{J_i(t) } |, wherein, J_i(t) represents a workpiece that can be processed on the production facility at time t, { } represents a set, | | represents a basis of the set;

device demand trend D_k(t) is:

$D_k\left(t\right)=\frac{d}{\mathrm{dt}}{F}_k\left(t\right),$ in the formula, F_k(t) is according to R_k(t) fitting the generated continuously derivable function;

mean relaxation time t of workpiece i_s，iComprises the following steps:

$t_{s,i}=\frac{d_i-t-t_{r,i}}{n_{r,i}},$ where t is the current time, d_iScheduled delivery time, t, for workpiece i_{r， i}Desired value, n, of the total machining time required for the non-machining process of the workpiece i_r，iThe number of unprocessed processes of the workpiece i is shown;

(4) setting iteration control parameters and an iteration initial value:

let the current iteration number j equal to 1 and the maximum iteration number be N_max；

Order S_optIs empty, and let Obj (S)_opt) Is a sufficiently large number;

let T⁽⁰⁾ _k＝0，t⁽⁰⁾ _p，i＝t⁽⁰⁾ _w，i＝t⁽⁰⁾ _d，i＝0；

(5) Setting all equipment to be in an idle state, and setting all workpieces to be in an initial state;

(6) allocating workpieces to be processed to the idle equipment according to the following steps:

(6.1) if no spare equipment or no workpiece to be machined exists, turning to the step (7);

(6.2) calculating the priority of all idle devices using the following formula;

r^(j) _cM，k＝r_M，k+p_k1R^(j) _k+p_k2D^(j) _k+q_kT^(j-1) _k

(6.3) completing for each idle device in order of priority from high to low:

(6.3.1) determining a set L of workpieces to be processed which can be processed on the workpiece set L, if the set L is an empty set, taking the equipment with the priority level as the idle equipment, and repeating the step;

(6.3.2) calculating the priority of the workpiece to be machined in L according to the following formula:

r^(j) _cJ，i＝r_J，i+p_it^(j) _s，i+q_i1t^(j-1) _p，i/t^(j-1) _w，i-q_i2t^(j-1) _d，i

(6.3.3) taking the workpiece with the highest priority to process the idle equipment;

(6.3.4) judging whether there is any spare equipment, if yes, entering the step (6.3.1), otherwise, entering the step (7);

(7) if all the workpieces are machined, turning to the step (8); otherwise, advancing for a unit time, and turning to the step (6);

(8) when the iteration is finished, the operation performance of the iteration system is calculated, and the scheduling objective function value Obj is calculated (S)^(j)) And j is the current iteration number. If Obj (S)^(j))＜Obj(S_opt) Then S is_opt＝S^(j)；

(9) Let j equal j +1, if j is less than or equal to N_maxTurning to the step (5), otherwise, entering the step (10);

(10) stopping iteration, and outputting an optimal scheduling result which can be directly used for scheduling the same production task.

The dispatching system for realizing the method comprises a central controller, a loading and unloading station, a system buffer station, an automatic rail trolley and processing equipment, and is characterized in that:

the processing equipment is provided with an equipment controller;

the blank enters a system buffer station through a loading and unloading station to wait for processing, and the finished product exits the system through the loading and unloading station;

the system buffer station is used for temporarily storing the workpieces and is provided with a buffer station controller; the system buffer station is provided with physical stations, each physical station is provided with a tray, and workpieces to be processed are clamped on the trays; the relative position of the physical station relative to the absolute origin of the system buffer station is recorded in the buffer station controller, and the state of the physical station is also recorded;

the automatic rail trolley can move among the loading and unloading station, the system buffer station and the processing equipment, and an automatic tray taking/placing mechanism is attached to the automatic rail trolley;

the loading and unloading station, the system buffer station and the processing equipment are all provided with tray exchange stations, each tray exchange station is provided with a position indicating element, and a position detecting element arranged on the automatic rail trolley can detect each tray exchange station, so that the accurate positioning of the automatic rail trolley is realized;

the central controller is respectively connected with the loading and unloading station display device, the loading and unloading station input device, the automatic rail trolley, the system buffer controller and the production equipment controller to control all the parts to work.

In the scheduling method and the scheduling system, the feedback of the running state and the running performance of the system is added on the basis of the conventional regular scheduling, the sequencing method of the production equipment and the workpieces to be processed is adjusted in real time through a feedback mechanism, the logistics in the production system is controlled, the demand of the workpieces to be processed on the production equipment is matched with the processing capacity of the production equipment, the bottleneck equipment effect of the system is reduced or eliminated, and the production running is optimized, so that the problems of the conventional regular scheduling method are solved. Meanwhile, the invention also provides a technical means for realizing the production target of the production manager and optimizing the specified operation performance, namely, a scheduling objective function is established according to the system performance index most concerned by the production manager at present, and the operation performance of the system in the meaning of the scheduling objective function is gradually improved in an iterative optimization mode on the basis of feeding back the scheduling rule. The method has important significance in actual production scheduling, and a production manager can formulate a scheduling objective function of a current production task according to a most concerned performance index, so that the scheduling method and the scheduling system can optimize the running performance of a relevant system to the maximum extent.

The scheduling method provided by the invention respectively processes three scheduling objective functions: obj1 (workpiece delay time is minimum), Obj2 (equipment utilization rate is maximum) and Obj3 (workpiece delay time is minimum and equipment utilization rate is maximum) are tested and compared with the conventional regular scheduling method, and statistical analysis of experimental results shows that: when the minimum delay time of the workpieces is taken as a scheduling target, compared with the conventional regular scheduling method, the method can reduce the delay time of the workpieces by over 96.7 percent under the condition of a 0.001 obvious level (t-test), and the utilization rate of equipment is slightly improved (less than 2 percent). When the maximum equipment utilization rate is used for scheduling the objective function, compared with the conventional regular scheduling method, the method can improve the equipment utilization rate by more than 3.2 percent and reduce the workpiece delay time by only 2.2 percent under the condition of a 0.001 obvious level (t-test). Compared with the conventional regular scheduling method, when the workpiece delay time is the minimum and the equipment utilization rate is the maximum, the method can reduce the workpiece delay time by over 93.5 percent and improve the equipment utilization rate by over 4 percent under the condition of a 0.001 obvious level (t-test). The test result of the invention shows that: for a given scheduling rule, the performance of the scheduling method is generally superior to that of the existing rule scheduling method.

Drawings

FIG. 1 is an extended process sequence planning tree;

FIG. 2 is a schematic diagram of a rule scheduling principle with state performance feedback;

FIG. 3 is a schematic diagram of a decision flow of the scheduling method at a decision time according to the present invention;

FIG. 4 is a model of equipment composition and layout for a production system;

fig. 5 is a communication connection diagram of a scheduling system.

Detailed Description

In the production system, the production equipment M has certain processing capacity and can complete certain processing operation. The workpiece is a workpiece, and the machining of the workpiece can be divided into a plurality of different machining operations, each of which is called a workpiece one-pass operation Op. In the process of processing the workpiece, some procedures must be completed before other procedures, namely, certain requirements are required on the processing sequence of the procedures. A possible sequence of operations for a workpiece is referred to as a process sequence plan for the workpiece. When there is more than one available process sequence plan for a workpiece, the workpiece is said to have multiple process sequence plans, or the workpiece is said to have process sequence plan flexibility.

Each process of the workpiece can be processed on one or more production devices, but at the same time, one workpiece can be processed on only one device at most. When a process of a workpiece is processed on different production equipment, the required processing time is different. In order to complete the processing of the workpiece, each process of the workpiece must be processed in sequence according to the process sequence planning requirement of the workpiece, and for this purpose, the workpiece must visit the production equipment in a certain sequence and be processed on the equipment. The sequence in which the workpiece is accessed in the system to the production facility is referred to as the processing path of the workpiece. If a process of a workpiece can be performed on multiple production facilities, the workpiece has multiple processing paths in the production system, which is called the processing path flexibility of the workpiece.

Furthermore, due to the requirements of the production process, different workpieces may have different processing paths, and the same workpiece may be accessed multiple times to the same production facility.

From the above discussion, it can be seen that the present invention does not impose any additional limitation on the production process, and is the most general production process, therefore, the scheduling method and scheduling system provided by the present invention have wide adaptability, and are suitable for scheduling of production systems with small product batch, multiple product varieties and complex logistics process, such as flexible manufacturing systems, and also suitable for scheduling of mass production systems, flow production systems, single-piece production systems and reentrant production systems.

The invention provides a scheduling method and a scheduling system, aiming at planning a tree according to an extended process sequence, taking a scheduling objective function as an optimization index by means of state and performance feedback, reasonably arranging the processing of a workpiece procedure and improving the running performance of a production system.

The invention provides an extended process sequence planning tree (figure 1) model and is used for representing the process sequence planning flexibility of workpieces and the processing path flexibility of the workpieces, wherein, a node represents a process and is represented by Op, the number of elements in { } represents the equipment number of a production system, the number sequence in { } represents the relation between the process and the equipment in the production system, wherein "-1" represents that the process cannot be processed on the equipment, positive numbers represent that the process can be processed on the equipment, and the magnitude of the numerical value represents the required processing time. For example, Op1{10, -1, -1, -1, 14, -1, -1, -1, -1, -1}, indicates that 10 devices are in total in the production system, and the process Op1 can be processed on the device 1 and the device 5, and the required processing time is 10 and 14 unit times, respectively.

A path from a root node to a leaf node is referred to as a process sequence planning scheme for the workpiece. For the workpiece shown in fig. 1, which consists of 4 processes, namely Op1, Op2, Op3 and Op4, there are 3 possible process sequence plans for the processing of the workpiece, namely:

(1)Op1→Op3→Op4→Op2；

(2)Op1→Op4→Op3→Op2；

(3)Op1→Op4→Op2→Op3。

wherein the process sequence plan (1) represents: after Op1 is processed, Op3 can be processed; after Op3 is processed, Op4 can be processed; after Op4 is processed, Op2 can be processed; and the rest can be analogized.

Since both Op1 and Op4 can be processed on two machines, there are 4 possible processing paths for the workpiece in the production system for any one process sequence plan, for example, for process sequence plan (1), the 4 possible processing paths for the workpiece are:

(1)M1→M2→M4→M3

(2)M1→M2→M8→M3

(3)M5→M2→M4→M3

(4)M5→M2→M8→M3

the process sequence planning tree is expanded to show the process sequence planning flexibility of the workpieces and the processing path flexibility of the workpieces, so that the flexibility of the system and the workpieces can be effectively utilized in the regular scheduling process to form a better scheduling scheme.

The regular scheduling aims at arranging a suitable process for each idle equipment at each decision time, for example, for the workpiece shown in fig. 1, when Op1 finishes processing, the next processing process can select Op3 or Op 4. Op3 can be processed on the device M2, the required processing time is 30 units of time; and Op4 can be processed on the equipment M4 and M8, the required processing time is 24 and 31 unit times respectively. The particular process selected and the equipment on which the process is scheduled to be processed is determined by the scheduling rules. In the invention, the priority of equipment and workpieces is determined by adopting a scheduling rule with state and performance feedback, and the equipment with high priority is selected to process the workpieces with high priority, thereby completing production scheduling.

In the process of operating the production system, variables characterizing the operational properties of equipment and workpieces in the system are called system state variables. For a state variable, the change process of the state variable in the whole scheduling period is mainly concerned, and the value of the state variable at the scheduling end time is not only concerned. The operation state of the production system is divided into an equipment state and a workpiece state.

The quantity reflecting the demand of the workpiece to be machined on each production device is called a device state variable. The equipment state variables include equipment demand and equipment demand trends.

At the moment t, the demand of all the workpieces to be processed in the production system on the production equipment Mk is called the demand of the equipment k and is recorded as R_k(t) of (d). The plant demand is calculated by:

R_k(t)＝|{J_i(t) } (formula 1a)

Wherein: j. the design is a square_i(t) represents a workpiece that can be processed on the production facility Mk at time t, { } represents a set, | | represents a base of the set.

For the workpiece shown in fig. 1, assuming that the workpiece has entered the system and has not yet been processed at time t, the workpiece may be processed on equipment M1 and M5, which are both required; if the operation Op1 of the workpiece is finished, the next operation can select Op3 or Op4, wherein Op3 can be processed on the device M2, and Op4 can be processed on the device M4 or M8, so that the workpiece has a demand for the devices M2, M4 and M8. The tree is planned according to the expanded process sequence, the requirements of all the workpieces to be processed on the equipment can be calculated, and therefore the required quantity of each idle equipment can be calculated.

Equipment requirements are a different concept than the queue length of workpieces to be processed before the equipment. Queue length represents the number of workpieces that have been allocated to the equipment but have not yet been processed; and the equipment demand represents the potential demand for the equipment by the workpieces in the system. Because of the flexibility of the process sequence planning and the flexibility of the processing paths of the workpieces, these workpieces may be allocated to the processing of this device and also to the processing of other devices.

The variation trend of the Mk demand of the workpieces to be processed on the equipment in a period of time in the future is called the demand trend of the equipment k and is recorded as D_k(t) of (d). Let it be possible to use a continuously derivable function F_k(t) fitting the plant requirement R_k(t), the equipment demand trend is:

$D_k\left(t\right)=\frac{d}{\mathrm{dt}}{F}_k\left(t\right)$ (formula 1b)

Quantities in the production system that reflect the properties of the workpiece being machined are referred to as workpiece state variables. The workpiece state variables mainly include the mean relaxation time (t) of the workpiece i_s，i) The calculation method is as follows:

$t_{s,i}=\frac{d_i-t-t_{r,i}}{n_{r,i}}$ (formula 1c)

Where t is the current time, d_iScheduled delivery time, t, for workpiece i_r，iDesired value, n, of the total machining time required for the non-machining process of the workpiece i_r，iThe number of unprocessed steps of the workpiece i.

The system state variables defined by the invention are:

$x=\left[\begin{array}{c}R\\ D\\ t_s\end{array}\right]$ (formula 1d)

Wherein R ═ R₁，R₂，......，R_K]^T，D＝[D₁，D₂，......，D_K]^T，t_s＝[t_s，1，t_s，2，......，t_s，N]^TK is the number of production facilities in the system, and N is the number of workpieces in the system.

The operation performance index of the production system is an evaluation standard for measuring the operation condition of the production system. As regards the runnability, its value at the end of the production cycle is of major concern, not its course of variation throughout the production cycle. The operating performance indexes of the production system can be divided into two categories: the equipment related index and the workpiece related index can be divided into a workpiece finishing index and a workpiece flowing index.

The index for evaluating the running performance of the equipment in the production system is called equipment association index, and the key factor for measuring the equipment association index is the processing time of the equipment in the whole scheduling period. The equipment association index mainly comprises an average utilization rate (U) and an equipment load imbalance rate (B) of equipment in the system, and the calculation method comprises the following steps:

<math><mrow> <mi>U</mi> <mo>=</mo> <mrow> <mo>(</mo> <mfrac> <mn>1</mn> <mi>KT</mi> </mfrac> <munderover> <mi>&Sigma;</mi> <mrow> <mi>k</mi> <mo>=</mo> <mn>1</mn> </mrow> <mi>K</mi> </munderover> <msub> <mi>T</mi> <mi>k</mi> </msub> <mo>)</mo> </mrow> <mo>&times;</mo> <mn>100</mn> <mo>%</mo> </mrow></math> (formula 2a)

<math><mrow> <mi>B</mi> <mo>=</mo> <mrow> <mo>(</mo> <mfrac> <mn>1</mn> <mi>K</mi> </mfrac> <munderover> <mi>&Sigma;</mi> <mrow> <mi>k</mi> <mo>=</mo> <mn>1</mn> </mrow> <mi>K</mi> </munderover> <mo>|</mo> <msub> <mi>T</mi> <mi>k</mi> </msub> <mo>-</mo> <mfrac> <mn>1</mn> <mi>K</mi> </mfrac> <munderover> <mi>&Sigma;</mi> <mrow> <mi>j</mi> <mo>=</mo> <mn>1</mn> </mrow> <mi>K</mi> </munderover> <msub> <mi>T</mi> <mi>j</mi> </msub> <mo>|</mo> <mo>)</mo> </mrow> <mo>&times;</mo> <mn>100</mn> <mo>%</mo> </mrow></math> (formula 2b)

Wherein T is a scheduling period, T_j、T_kThe machining time (including the workpiece mounting/demounting time, the same applies hereinafter) of each of the devices j and k.

The equipment load unbalance rate is an important index for measuring the relative load of the equipment. When the load unbalance rate is high, the load distribution of equipment in the production system is uneven, bottleneck equipment exists, and the system productivity is limited by the productivity of the bottleneck equipment; when the load unbalance rate is small, the load distribution of the equipment in the system is uniform.

The index for evaluating the finished condition of the processed workpiece in the production system is called the finished workpiece index, and the key factor for measuring the finished workpiece index is the delay time of the workpiece. The finished work indexes are also called relative work indexes, the evaluation standards of the finished work indexes are relative to the planned delivery time of the work, the indexes reflect the response capability of the system to market change, and the finished work indexes are important indexes for measuring the competitiveness of enterprises. The finishing indicators of the workpieces mainly include the mean workpiece delay time (t)_d) Maximum workpiece delay time (t)_d，max) And the number of delay workers (N)_d) Their calculation method is as follows:

<math><mrow> <msub> <mi>t</mi> <mi>d</mi> </msub> <mo>=</mo> <mfrac> <mn>1</mn> <mi>N</mi> </mfrac> <munderover> <mi>&Sigma;</mi> <mrow> <mi>i</mi> <mo>=</mo> <mn>1</mn> </mrow> <mi>N</mi> </munderover> <mrow> <mo>(</mo> <mi>max</mi> <mo>{</mo> <msub> <mi>t</mi> <mrow> <mi>d</mi> <mo>,</mo> <mi>i</mi> </mrow> </msub> <mo>,</mo> <mn>0</mn> <mo>}</mo> <mo>)</mo> </mrow> </mrow></math> (formula 2c)

t_d，mam＝max{max{t_d，i0 (formula 2d)

N_d＝|{i，t_d，i> 0} | (formula 2e)

Wherein: t is t_d，iThe lead/lag time for workpiece i is defined as:

t_d，i＝t_c，i-d_i

wherein: t is t_c，iFor the finishing time of the workpiece i, d_iThe planned delivery time for workpiece i.

The index for evaluating the flow state of the processed workpiece in the production system is called a workpiece flow index, and the key factors for measuring the workpiece flow index are the workpiece processing time and the workpiece waiting time. The workpiece flow indexes are also called workpiece absolute indexes and reflect the absolute state of the workpiece in the machining process, and the indexes reflect the production efficiency of a production system and are related to the production cost. The workpiece flow index mainly comprises the average workpiece processing time (t)_p) Mean waiting time of workpiece (t)_w) And maximum workpiece transit time (t)_t，max) The calculation method is as follows:

<math><mrow> <msub> <mi>t</mi> <mi>p</mi> </msub> <mo>=</mo> <mfrac> <mn>1</mn> <mi>N</mi> </mfrac> <munderover> <mi>&Sigma;</mi> <mrow> <mi>i</mi> <mo>=</mo> <mn>1</mn> </mrow> <mi>N</mi> </munderover> <msub> <mi>t</mi> <mrow> <mi>p</mi> <mo>,</mo> <mi>i</mi> </mrow> </msub> </mrow></math> (formula 2f)

<math><mrow> <msub> <mi>t</mi> <mi>w</mi> </msub> <mo>=</mo> <mfrac> <mn>1</mn> <mi>N</mi> </mfrac> <munderover> <mi>&Sigma;</mi> <mrow> <mi>i</mi> <mo>=</mo> <mn>1</mn> </mrow> <mi>N</mi> </munderover> <msub> <mi>t</mi> <mrow> <mi>w</mi> <mo>,</mo> <mi>i</mi> </mrow> </msub> </mrow></math> (formula 2g)

t_t，max＝max{t_p，i+t_w，i} (formula 2h)

Wherein: n is the number of workpieces in the system, t_p，iThe machining time (including loading/unloading time, the same applies hereinafter) t of the workpiece i_w，iIs the waiting time of the workpiece i.

The first table shows typical evaluation indexes of the operation performance of the production system and key factors for measuring the indexes. As can be seen from table one, although there are many indexes for evaluating the operation performance of the production system, the key factors for measuring the operation performance are: the processing time (T) of the production equipment during the whole production cycle_k) Time of workpiece machining (t)_p，i) Workpiece waiting time (t)_w，i) And workpiece delay time (t)_d，i). In the scheduling method related by the invention, the performance feedback variables are defined as follows:

y＝[T₁...T_Kt_p，1...t_p，Nt_w，1...t_w，Nt_d，1...t_d，N]^T(formula 2i)

TABLE 1

The scheduling method provided by the invention introduces state and performance feedback on the basis of the conventional regular scheduling, therebyA feedback scheduling rule is constructed, the principle of which is shown in fig. 2. In the figure, T_askR is a scheduling rule vector specified by the production manager H for the tasks to be performed by the production system 1, r_cFor feeding back the scheduling rule vector, Obj is the scheduling target formulated by the production manager H, x is the system running state vector, and y is the system running performance feedback vector.

And if P and Q are respectively state and performance feedback coefficient matrixes, the matrix expression of the feedback scheduling rule is as follows:

r_cr + Px + Qy (formula 3)

The above formula gives a general matrix expression form of the feedback scheduling rule of the rule scheduling method with state performance feedback. According to a specific production system, different system states and operation performances can be selected, so that a corresponding feedback scheduling rule is formed.

In the scheduling algorithm of the present invention, for the device k, the scheduling rule with state and performance feedback is:

r_cM，k＝r_M，k+p_k1R_k+p_k2D_k+q_kT_k(formula 3a)

For a workpiece i to be processed, the scheduling rule with state and performance feedback is as follows:

r_cJ，i＝r_J，i+p_it_s，i+q_i1t_p，i/t_w，i-q_i2t_d，i(formula 3b)

Wherein r is_M，k、r_J，iIndicating the scheduling rules respectively assigned by the production manager to the equipment k, the scheduling rules assigned to the workpieces i, p_k1、p_k2Is the state feedback coefficient of device k, q_kAs a coefficient of performance feedback, p, for device k_iIs a state feedback coefficient, q, of the workpiece i_i1、q_i2And (4) a performance feedback coefficient of the workpiece i. A brief of the above formulaThe chemical conditions are as follows: assigning a scheduling rule r to all devices_MAssigning a scheduling rule r to all workpieces_JAnd then, the feedback scheduling rule is reconstructed on the basis. A more simplified case is: one scheduling rule is assigned to all devices and artifacts.

Order: r is_c＝[r_cM，1r_cM，2...r_cM，Kr_cJ，1r_cJ，2...r_cJ，N]^T

r＝[r_M，1r_M，2...r_M，Kr_J，1r_J，2...r_J，N]^T

x＝[R₁R₂...R_KD₁D₂...D_Kt_s，1t_s，2...t_s，N]^T

y＝[T₁T₂...T_Ku₁u₂...u_Nt_d，1t_d，2...t_d，N]^T(wherein u)_i＝t_p，i/t_w，i)

Then (equation 3a) and (equation 3b) can be expressed as matrix expressions in the form of (equation 3).

The feedback coefficients in the formulas 3a and 3b reflect the relative influence degree of the corresponding state and performance on the sorting rule, generally, the feedback coefficients of the state and performance can be simply set to 1, and if the optimization of certain operation performance needs to be enhanced, the feedback of the corresponding state and performance can be increased and decreasedAnd (4) the coefficient. Such as: given that a production task has very strict delivery time requirements, q in (equation 3b) can be increased_2i. In particular, when the feedback coefficient is 0, it indicates that the scheduling rule is independent of the corresponding feedback variable.

At any decision moment, the priority of the idle equipment is calculated according to the formula 3a, workpieces to be machined which can be machined on certain idle equipment are respectively determined according to the sequence from high to low of the priority, the priority of the workpieces to be machined is calculated according to the formula 3b, and the workpieces to be machined with the highest priority are allocated to the equipment for machining. The regular scheduling of the production system is to repeatedly apply the step, and at each decision time, the proper workpieces are allocated to the proper equipment for processing until all the workpieces are processed.

In the calculation of the priority, r_cM，kThe smaller the value of (d), the higher the priority of the corresponding device; r is_cJ，iThe smaller the value of (c), the higher the priority of the corresponding workpiece.

When the priorities of idle equipment and workpieces to be processed are calculated according to the formulas (3 a) and (3 b), because state feedback is introduced into the priority calculation formula, the priority calculation methods of the equipment and the workpieces are not fixed and constant, and the calculation of the priorities is related to the system running state, so that a technical means for adjusting the equipment and workpiece priority ordering method in real time according to the system running state is provided. Meanwhile, system operation performance feedback is introduced into the (formula 3a) and the (formula 3b), so that an iterative optimization means for adjusting equipment and a workpiece priority ordering method according to the last operation performance of the system is provided.

The feedback rule scheduling controls the logistics in the production system as follows: when the utilization rate of the device k is low, T_kDecrease by feedback control, r_kAnd the priority of the equipment k is increased, so that the equipment k can obtain more workpieces, and the utilization rate of the equipment k is improved. Similarly, when it is predicted that the workpiece i cannot be completed on schedule, t_d，iRising, by feedback control, r_iAnd descending, and ascending the priority of the workpiece i so as to enable the workpiece i to be processed in advance.

The system operation performance is an objective evaluation of the system operation condition, and the scheduling target is the pursuit of a production manager for the specific operation performance of the system. The scheduling objective reflects the subjective intention of the production manager, so different production managers often have different scheduling objectives, and even the same production manager can change the scheduling objectives with the change of production tasks and production cycles. The scheduling objective reflects the system operation performance which is most concerned by the production manager currently, so the production process optimization should be performed around the scheduling objective, i.e. the system operation performance contained in the scheduling objective is optimized with emphasis. In actual production scheduling, the scheduling objective may be expressed as a function of the system operation performance and the system operation state. Common scheduling objective functions are: the production cycle is shortest, the workpiece delay time is shortest, the equipment utilization rate is highest, the equipment load imbalance rate is minimum, and the like, and the scheduling objective function can also be the weighted sum of the indexes.

The scheduling system and the scheduling method provided by the invention provide a technical means for optimizing the system operation performance appearing in the scheduling objective function by adjusting the state and performance feedback coefficient in the feedback scheduling rule, and the specific adjusting method is as follows: for the state and performance variables appearing in the scheduling objective function, the feedback coefficients of the variables are increased in the feedback scheduling rule. Such as: when the scheduling objective function is that the workpiece delay time is minimum or the scheduling objective function contains a workpiece delay time variable, the feedback coefficient q in the (formula 3b) is increased_i2The feedback scheduling rules are made more sensitive to workpiece delay time.

In addition, when the system has a scheduling objective function, the scheduling method also adopts the following iterative optimization strategy to continuously optimize the production process.

r^(j) _cM，k＝r_M，k+p_k1R^(j) _k+p_k2D^(j) _k+q_kT^(j-1) _k(formula 4a)

r^(j) _cJ，i＝r_J，i+p_it^(j) _s，i+q_i1t^(j-1) _p，i/t^(j-1) _w，i-q_i2t^(j-1) _d，i(formula 4b)

S_opt＝S^(j)When Obj (S)^(j))＜Obj(S_opt) Hour (formula 4c)

In the formula, the superscript j represents the number of iterations. r is^(j) _cM,k、r^(j) _cJ，iAnd respectively representing feedback scheduling rules adopted by the equipment k and the workpiece i in the jth iteration, namely determining the priority of the production equipment and the priority of the workpiece according to the scheduling rules at each decision point moment. S^(j)According to a feedback scheduling rule r^(j) _cM，kAnd r^(j) _cJ，iAnd obtaining a system solution at the j iteration, namely a process queue completed on each production device and the starting time and the ending time of each process. S_optIs the optimal solution of the system. Obj is the scheduling objective function, Obj (S) represents the objective function value of the system when the system scheduling solution is S. On first iteration, define S_optIs empty, and defines Obj (S)_opt) Is a sufficiently large positive number, e.g., 1000, 10000, etc. Here, in the j-th iteration scheduling, the method for calculating the priority of the equipment and the workpiece is not only related to the current state of the system, but also related to the operation performance of the (j-1) th system, so that an iteration optimization means for adjusting the equipment and the method for calculating the priority of the workpiece according to the last operation performance of the system is provided.

The production system is provided with K processing devices, the production task comprising N workpieces needs to be completed, and the delivery time d of each workpiece in the production task is known_iIf the extended process sequence planning tree of each workpiece in the production task is known, the specific steps of implementing production scheduling by applying the method of the invention are as follows:

1. a scheduling objective function Obj is formulated according to the production task

If the production task is delivered in a time tight or a delay, the scheduling objective can be selected from the following equations 2c, 2d and 2 e:

<math><mrow> <mi>Obj</mi> <mo>=</mo> <mi>min</mi> <msub> <mi>t</mi> <mi>d</mi> </msub> <mo>=</mo> <mi>min</mi> <mfrac> <mn>1</mn> <mi>N</mi> </mfrac> <munderover> <mi>&Sigma;</mi> <mrow> <mi>i</mi> <mo>=</mo> <mn>1</mn> </mrow> <mi>N</mi> </munderover> <mrow> <mo>(</mo> <mi>max</mi> <mo>{</mo> <msub> <mi>t</mi> <mrow> <mi>d</mi> <mo>,</mo> <mi>i</mi> </mrow> </msub> <mo>,</mo> <mn>0</mn> <mo>}</mo> <mo>)</mo> </mrow> <mo>,</mo> </mrow></math> or

Obj＝mint_d，max＝min(max{max{t_d，i}, 0}), or

Obj＝minN_d＝min|{i，t_d，i＞0}|

If the delivery time of the production task is loose, then the alternative 2a or 2b is the scheduling target, namely:

<math><mrow> <mi>Obj</mi> <mo>=</mo> <mi>max</mi> <mi>U</mi> <mo>=</mo> <mi>max</mi> <mrow> <mo>(</mo> <mfrac> <mn>1</mn> <mi>KT</mi> </mfrac> <munderover> <mi>&Sigma;</mi> <mrow> <mi>k</mi> <mo>=</mo> <mn>1</mn> </mrow> <mi>K</mi> </munderover> <msub> <mi>T</mi> <mi>k</mi> </msub> <mo>)</mo> </mrow> <mo>&times;</mo> <mn>100</mn> <mo>%</mo> <mo>,</mo> </mrow></math> or

<math><mrow> <mi>Obj</mi> <mo>=</mo> <mi>min</mi> <mi>B</mi> <mo>=</mo> <mi>min</mi> <mrow> <mo>(</mo> <mfrac> <mn>1</mn> <mi>K</mi> </mfrac> <munderover> <mi>&Sigma;</mi> <mrow> <mi>k</mi> <mo>=</mo> <mn>1</mn> </mrow> <mi>K</mi> </munderover> <mo>|</mo> <msub> <mi>T</mi> <mi>k</mi> </msub> <mo>-</mo> <mfrac> <mn>1</mn> <mi>K</mi> </mfrac> <munderover> <mi>&Sigma;</mi> <mrow> <mi>j</mi> <mo>=</mo> <mn>1</mn> </mrow> <mi>K</mi> </munderover> <msub> <mi>T</mi> <mi>j</mi> </msub> <mo>|</mo> <mo>)</mo> </mrow> <mo>&times;</mo> <mn>100</mn> <mo>%</mo> </mrow></math>

Formula 2f, formula 2g, or formula 2h may also be selected as the scheduling target, i.e.:

<math><mrow> <mi>Obj</mi> <mo>=</mo> <mi>min</mi> <msub> <mi>t</mi> <mi>p</mi> </msub> <mo>=</mo> <mi>min</mi> <mfrac> <mn>1</mn> <mi>N</mi> </mfrac> <munderover> <mi>&Sigma;</mi> <mrow> <mi>i</mi> <mo>=</mo> <mn>1</mn> </mrow> <mi>N</mi> </munderover> <msub> <mi>t</mi> <mrow> <mi>p</mi> <mo>,</mo> <mi>i</mi> </mrow> </msub> <mo>,</mo> </mrow></math> or

<math><mrow> <mi>Obj</mi> <mo>=</mo> <mi>min</mi> <msub> <mi>t</mi> <mi>w</mi> </msub> <mo>=</mo> <mi>min</mi> <mfrac> <mn>1</mn> <mi>N</mi> </mfrac> <munderover> <mi>&Sigma;</mi> <mrow> <mi>i</mi> <mo>=</mo> <mn>1</mn> </mrow> <mi>N</mi> </munderover> <msub> <mi>t</mi> <mrow> <mi>w</mi> <mo>,</mo> <mi>i</mi> </mrow> </msub> <mo>,</mo> </mrow></math> Or

Obj＝mint_t，max＝min(max{t_p，i+t_w，i})

The scheduling objective function may be a weighted sum of several performances in order to obtain a better overall performance. For example, when it is required to guarantee the delivery date of the workpiece and improve the utilization rate of the equipment, the scheduling objective function may be set as:

<math><mrow> <mi>Obj</mi> <mo>=</mo> <mi>min</mi> <mrow> <mo>(</mo> <msub> <mi>c</mi> <mn>1</mn> </msub> <msub> <mi>t</mi> <mi>d</mi> </msub> <mo>-</mo> <msub> <mi>c</mi> <mn>2</mn> </msub> <mi>U</mi> <mo>)</mo> </mrow> <mo>=</mo> <mi>min</mi> <mrow> <mo>(</mo> <msub> <mi>c</mi> <mn>1</mn> </msub> <msub> <mi>t</mi> <mi>d</mi> </msub> <mo>-</mo> <msub> <mi>c</mi> <mn>2</mn> </msub> <mrow> <mo>(</mo> <mfrac> <mn>1</mn> <mi>KT</mi> </mfrac> <munderover> <mi>&Sigma;</mi> <mrow> <mi>k</mi> <mo>=</mo> <mn>1</mn> </mrow> <mi>K</mi> </munderover> <msub> <mi>T</mi> <mi>k</mi> </msub> <mo>)</mo> </mrow> <mo>&times;</mo> <mn>100</mn> <mo>%</mo> <mo>)</mo> </mrow> </mrow></math>

wherein c is₁、c₂Is constant, and if the lead time is more important, a larger c may be used₁If the equipment utilization rate is more important, a larger c can be taken₂。

2. Respectively appointing a scheduling rule r for a production device k and a workpiece i_M，k、r_J，i. Simplified processing methods may also be employed: assigning a scheduling rule r to all devices_MAssigning a scheduling rule r to all workpieces_J. Simpler methods can also be used: the same scheduling rule r is assigned to all devices and workpieces. Commonly used scheduling rules may be selected, such as: the longest residual processing time is preferred, the shortest residual processing time is preferred, the largest residual process number is preferred, the smallest residual process number is preferred, the earliest delivery date is preferred, the shortest relaxation time is preferred, the highest processing efficiency is preferred, and the like;

3. respectively setting state and performance feedback coefficients in the iterative feedback scheduling rules (equation 4a) and (equation 4 b):

p_k1＝p_k2＝q_k＝1，k＝1，2，......，K

p_i＝q_i1＝q_i2＝1，i＝1，2，......，N

if the scheduling objective function contains the equipment utilization rate or the equipment load imbalance rate, increasing q_k(ii) a If the scheduling objective function includes an average workpiece delay time, or includes a maximum workpiece delay time, or includes a number of delayed workpieces, then increase q_i2(ii) a If the scheduling objective function comprises the workpiece average processing time, the workpiece average waiting time or the workpiece maximum passing time, increasing q_i1。

4. Setting iteration control parameters and iteration initial values, namely:

let current iterationThe number j is 1, and the maximum iteration number is N_max；

Order S_optIs empty, and let Obj (S)_opt) A sufficiently large number (1000 or 10000, etc.);

let T⁽⁰⁾ _k＝0，k＝1，2，......，K；

Let t⁽⁰⁾ _p，i＝t⁽⁰⁾ _w，i＝t⁽⁰⁾ _d，i＝0，i＝1，2，......，N

5. All the devices are set to an idle state, and all the workpieces are set to an initial state.

6. The spare equipment is assigned a workpiece to be machined according to the subroutine algorithm shown in fig. 3.

7. If the workpieces are not finished, the operation is proceeded for one unit time, and the step 6 is executed.

8. Ending the iteration, calculating the operation performance of the iteration system according to the formula (2 a) -formula (2 h), and calculating the scheduling objective function value Obj (S)^(j)) J is the current iteration number, if Obj (S)^(j))＜Obj(S_opt) Then S is_opt＝S^(j)。

9. Adding 1 to the iteration number, if j is less than or equal to N_maxAnd turning to the step 5, and entering next iteration.

10. Stopping iteration and outputting an optimal scheduling result S_optAnd a corresponding scheduling objective function Obj (S)_opt) The value is obtained.

Fig. 4 is a model of the equipment composition and layout of a production system (production system 1) implementing the scheduling algorithm of the present invention, and fig. 5 is a schematic diagram of the communication connection of the system.

In the production system 1, the workpiece may be divided into a blank R, a semi-finished product, and a finished product F according to the processing condition of the workpiece. The blank is manually clamped on a standard tray P at a loading and unloading station 4 and enters a production system 1 to wait for processing; the finished product is manually removed from the production system 1 at the loading and unloading station 4. The terminal 4 is provided with a display device 2 for receiving and displaying the output command of the central controller 8, and prompting the operator of the type of operation that should be currently performed: i.e. take off the finished product on the pallet P at the loading and unloading station 4 and clamp the blanks of the specified type on this pallet in the specified manner, as required by the command of the central controller 8. There is also an input device 3 at the terminal 4 for the operator to send information to the central controller 8 informing the central controller 8 to: the finished product on the pallet at the loading and unloading station has been removed and a new blank has been clamped as required, which blank can be loaded into the production system 1 by the automatic trolley 9 for processing.

The system buffer station 6 is used for temporarily storing workpieces. A certain number of physical stations 7a, 7b, 7c are arranged on the buffer station, a tray P can be arranged on each physical station, and workpieces to be processed are clamped on the trays P. In the system buffer station controller 5, the relative position of the physical station with respect to the absolute origin of the system buffer station 6 is recorded, and the state of the physical station (presence or absence of a tray on the physical station, presence or absence of a workpiece on the tray, the number of the tray, and the number of the workpiece on the tray) is also recorded. Upon command of the buffer station controller 5, the buffer station can move the designated physical station to the buffer station tray exchange station S02, S03, or S04, ready for the tray take/put operation. The buffer controller 5 is connected to the central controller 8 through a local area network LAN, and may receive a command from the central controller 8, or may feed back status information of the system buffer station 6 to the central controller 8.

The automatic rail trolley 9 can move on the rail 10, and the automatic tray taking/placing mechanism is attached to the trolley 9 and can complete the tray taking/placing operation. In the production system 1, a position indicating element is installed at each tray exchange station S01, S02, S03, S15, and a position detecting element installed on the automatic trolley (9) can detect each tray exchange station, thereby achieving accurate positioning of the automatic trolley (9). The cart receives commands from the central controller 8 via the wireless communication device a and returns status information of the cart. The automatic trolley 9 can move to the designated pallet changing station S01, S02, S03, S15 and complete the pallet taking/placing operation according to the command issued by the central controller 8, so that the blanks, semi-finished products, finished products can be moved between the loading and unloading station 4, the system buffer station 6 and the production facilities M1, M2, M3.

In the production system 1, there are several production apparatuses M1, M2, M3. The equipment has three states, namely a processing state, an idle state, and a fault (including scheduled maintenance) state. Each device has a device controller C1, C2, C3, which is responsible for monitoring and controlling the operation of the device. The equipment controllers C1, C2, C3, which are connected to the central controller 8 through the LAN, may receive commands and nc processing programs downloaded from the central controller 8, and perform corresponding processing tasks, or may upload equipment status to the central controller 8.

The central controller 8 is composed of a computer, an input/output circuit, a communication device, corresponding scheduling software and the like, and is responsible for monitoring the running state of the production system and controlling the running of the system.

The central controller 8 is connected with the loading and unloading station display device 2 and the loading and unloading station input device 3 through output and input interfaces respectively, is connected with the automatic rail trolley 9 through a wireless communication device A, and is connected with the system buffer controller 5 and the production equipment controllers C1, C2 and C3 through a local area network LAN.

The central controller 8 stores the delivery date of all the workpieces in the production task and the extended process sequence planning tree thereof, and runs the scheduling program according to the scheduling method provided by the invention to realize the scheduling control of the production system 1, namely: and controlling an iteration loop, judging whether all iterations are finished, and outputting the optimal scheduling result of the system if all iterations are finished. In each iteration cycle, the state of each workpiece in the system, namely whether the workpiece is in a machining state or a to-be-machined state, and the process that the workpiece has just been machined (or is being machined) is recorded in real time. In addition, the state of each device, namely whether the device is in a processing state, an idle state or a fault state, the processing procedure finished by each device and the starting time and the ending time of the procedure are recorded in real time. At each decision moment, according to the feedback scheduling rule, determining which procedure of which workpiece is allocated to which equipment for processing, and after completing one task allocation, changing the state of relevant workpieces and equipment in the system in real time and sending a pallet (workpiece) exchange command to the relevant equipment.

The pallet (workpiece) exchange command format issued by the central controller 8 is as follows:

LD Pxx Sxx; taking out the tray Pxx at the tray exchange station Sxx

UL Pxx Sxx; storing trays Pxx in tray exchange station Sxx

After a task assignment is completed, that is, after it is determined that a certain process of a certain workpiece (e.g., workpiece i) is assigned to a certain equipment (e.g., equipment k) for processing, the central controller 8 will issue a tray (workpiece i) taking command to the system buffer controller 5, and after receiving the command, the buffer controller 5 will move the tray loaded with the workpiece i in the buffer station to the tray exchange station S02, S03, or S04, and wait for the automatic trolley 9 to take the tray. Meanwhile, the central controller 8 sends a tray taking command to the automatic rail trolley 9, and the trolley 9 moves to a specified buffer station tray exchange station to take out the tray after receiving the command. Thereafter, the central controller 8 will send a pallet storing command to the automatic rail car 9, and the car 9 will store the pallet loaded with the workpiece i to the equipment k for processing.

In addition, after a process is finished by a piece of equipment, if the work piece has unfinished processes, or all processes of the work piece are finished but a tray is on the loading and unloading station at present, the central controller 8 sends a tray taking command to the automatic trolley 9, takes out the tray in the equipment and the work piece clamped on the tray, sends a tray storing command to the automatic trolley and the system buffer station, and sends the tray and the work piece clamped on the tray to the system buffer station 6 for temporary storage. If all the working procedures of the workpiece are finished and the loading and unloading station is idle at present, the central controller 8 sends a tray taking command and a tray storing command to the automatic rail trolley 9 in sequence, takes out the tray in the equipment and the workpiece clamped on the tray, sends the workpiece to the system loading and unloading station, outputs display information to the loading and unloading station, informs an operator to unload the finished product on the tray and clamp a new blank according to requirements.

If there are finished products already processed at the system buffer station 6, the central controller 8 informs the automatic trolley 9 to take them out and send them to the loading and unloading station 4. At the same time, the central controller 8 outputs a command to the loading and unloading station display 2 informing the operating workers at the loading and unloading station 4 to take off the finished product on the pallet and clamp a new blank as required. If there are empty trays in the system buffer station 6, the central controller 8 informs the automated trolley 9 to take out the trays and deliver them to the loading and unloading station 4. At the same time, the central controller 8 outputs a command to the loading and unloading station display 2 informing the operator at the loading and unloading station 4 to load and unload a new blank as required.

After the blank is clamped at the loading and unloading station 4, an operator sends a signal through the loading and unloading station input device 3, and the central controller 8 receives the signal and controls the automatic rail trolley 9 to take the blank away and send the blank to the system buffer area 6 to wait for processing.

A similar system of the production system is: on the basis of the production system 1, a system input buffer station and a system output buffer station are added. The input buffer station is used for storing blanks, and the output buffer station is used for storing finished products. Another similar system of the production system is: before each production plant M1, M2, M3.

Claims (5)

1. A regular scheduling method with state performance feedback sequentially comprises the following steps:

(1) a scheduling objective function Obj is formulated according to the production task;

(2) respectively appointing a scheduling rule r for a production device k and a workpiece i_M，k、r_J，i，k＝1，2，……，K，i＝1，2，……，N；

(3) Constructing an iterative feedback scheduling rule r_cM，k、r_cJ，i：

r_cM，k＝r_M，k+p_k1R_k+p_k2D_k+q_kT_k

r_cJ，i＝r_J，i+p_it_s，i+q_i1t_p，i/t_w，i-q_i2t_d，i

Wherein p is_k1、p_k2Is the state feedback coefficient of device k, q_kAs a coefficient of performance feedback, p, for device k_iIs a state feedback coefficient, q, of the workpiece i_i1、q_i2The performance feedback coefficient of the workpiece i is obtained; r_kIs the demand of the equipment k, D_kIs the demand trend of the equipment k, T_kThe processing time of the device k; t is t_s，iMean relaxation time, t, of workpiece i_p，iIs the machining time, t, of the workpiece i_w，iIs the waiting time, t, of the workpiece i_d，iDelay time of the workpiece i; wherein,

equipment demand R_k(t) is calculated from the following formula:

R_k(t)＝|{J_i(t) } |, wherein, J_i(t) represents a workpiece that can be processed on the production facility at time t, { } represents a set, | | represents a basis of the set;

device demand trend D_k(t) is:

$D_k\left(t\right)=\frac{d}{\mathrm{dt}}{F}_k\left(t\right),$ in the formula, F_k(t) is according to R_k(t) fitting the generated continuously derivable function;

mean relaxation time t of workpiece i_s，iComprises the following steps:

$t_{s,i}=\frac{d_i-t-t_{r,i}}{n_{r,i}},$ where t is the current time, d_iScheduled delivery time, t, for workpiece i_r，i

Desired value, n, of the total machining time required for the non-machining process of the workpiece i_r，iThe number of unprocessed processes of the workpiece i is shown;

(4) setting iteration control parameters and an iteration initial value:

let the current iteration number j equal to 1 and the maximum iteration number be N_max；

Order S_optIs empty, and let Obj (S)_opt) Is a sufficiently large number;

let T⁽⁰⁾ _k＝0，t⁽⁰⁾ _p，i＝t⁽⁰⁾ _w，i＝t⁽⁰⁾ _d，i＝0；

(5) Setting all equipment to be in an idle state, and setting all workpieces to be in an initial state;

(6) allocating workpieces to be processed to the idle equipment according to the following steps:

(6.1) if no spare equipment or no workpiece to be machined exists, turning to the step (7);

(6.2) calculating the priority of all idle devices using the following formula;

r^(j) _cM，k＝r_M，k+p_k1R^(j) _k+p_k2D^(j) _k+q_kT^(j-1) _k

(6.3) completing for each idle device in order of priority from high to low:

(6.3.1) determining a set L of workpieces to be machined which can be machined on the workpiece, if the set L is an empty set, taking the idle equipment with the priority level, and repeating the step;

(6.3.2) calculating the priority of the workpiece to be machined in L according to the following formula:

r^(j) _cJ，i＝r_J，i+p_it^(j) _s，i+q_i1t^(j-1) _p，i/t^(j-1) _w，i-q_i2t^(j-1) _d，i

(6.3.3) taking the workpiece with the highest priority to process the idle equipment;

(6.3.4) judging whether there is any spare equipment, if yes, entering the step (6.3.1), otherwise, entering the step (7);

(7) if all the workpieces are machined, turning to the step (8); otherwise, advancing for a unit time, and turning to the step (6);

(8) when the iteration is finished, the operation performance of the iteration system is calculated, and the scheduling objective function value Obj is calculated (S)^(j)) J is the current iteration number, if Obj (S)^(j))＜Obj(S_opt) Then S is_opt＝S^(j)；

(9) Let j equal j +1, if j is less than or equal to N_maxTurning to the step (5), otherwise, entering the step (10);

(10) stopping iteration, and outputting an optimal scheduling result which can be directly used for scheduling the same production task.

2. The scheduling method of claim 1, wherein: step (1) a scheduling objective function Obj is formulated according to the following modes:

if the production task is to be penalized for tight delivery times or for delayed deliveries, one of the following equations is selected as the scheduling objective function, namely:

<math><mrow> <mi>Obj</mi> <mo>=</mo> <mi>min</mi> </mrow> <mrow> <msub> <mi>t</mi> <mi>d</mi> </msub> <mo>=</mo> <mi>min</mi> <mfrac> <mn>1</mn> <mi>N</mi> </mfrac> <munderover> <mi>&Sigma;</mi> <mrow> <mi>i</mi> <mo>=</mo> <mn>1</mn> </mrow> <mi>N</mi> </munderover> <mrow> <mo>(</mo> <mi>max</mi> <mo>{</mo> <msub> <mi>t</mi> <mrow> <mi>d</mi> <mo>,</mo> <mi>i</mi> </mrow> </msub> <mo>,</mo> <mn>0</mn> <mo>}</mo> <mo>)</mo> </mrow> <mo>,</mo> </mrow></math> or

Obj＝mint_d，max＝min(max{max{t_d，i}, 0}), or

Obj＝minN_d＝min|{i，t_d，i＞0}|

If the delivery time of the production task is loose, one of the following formulas is selected as a scheduling objective function, namely:

<math><mrow> <mtext>Obj=maxU=max</mtext> <mrow> <mo>(</mo> <mfrac> <mn>1</mn> <mi>KT</mi> </mfrac> <munderover> <mi>&Sigma;</mi> <mrow> <mi>k</mi> <mo>=</mo> <mn>1</mn> </mrow> <mi>K</mi> </munderover> <msub> <mi>T</mi> <mi>k</mi> </msub> <mo>)</mo> </mrow> <mo>&times;</mo> <mn>100</mn> <mo>%</mo> <mo>,</mo> </mrow></math> or

<math><mrow> <mi>Obj</mi> <mo>=</mo> <mi>min</mi> <mi>B</mi> <mo>=</mo> <mi>min</mi> <mrow> <mo>(</mo> <mfrac> <mn>1</mn> <mi>K</mi> </mfrac> <munderover> <mi>&Sigma;</mi> <mrow> <mi>k</mi> <mo>=</mo> <mn>1</mn> </mrow> <mi>K</mi> </munderover> <mo>|</mo> <msub> <mi>T</mi> <mi>k</mi> </msub> <mo>-</mo> <mfrac> <mn>1</mn> <mi>K</mi> </mfrac> <munderover> <mi>&Sigma;</mi> <mrow> <mi>j</mi> <mo>=</mo> <mn>1</mn> </mrow> <mi>K</mi> </munderover> <msub> <mi>T</mi> <mi>j</mi> </msub> <mo>|</mo> <mo>)</mo> </mrow> <mo>&times;</mo> <mn>100</mn> <mo>%</mo> <mo>,</mo> </mrow></math> Or

<math><mrow> <mi>Obj</mi> <mo>=</mo> <mi>min</mi> <msub> <mi>t</mi> <mi>p</mi> </msub> <mo>=</mo> <mi>min</mi> <mfrac> <mn>1</mn> <mi>N</mi> </mfrac> <munderover> <mi>&Sigma;</mi> <mrow> <mi>i</mi> <mo>=</mo> <mn>1</mn> </mrow> <mi>N</mi> </munderover> <msub> <mi>t</mi> <mrow> <mi>p</mi> <mo>,</mo> <mi>i</mi> </mrow> </msub> <mo>,</mo> </mrow></math> Or

<math><mrow> <mi>Obj</mi> <mo>=</mo> <mi>min</mi> <msub> <mi>t</mi> <mi>w</mi> </msub> <mo>=</mo> <mi>min</mi> <mfrac> <mn>1</mn> <mi>N</mi> </mfrac> <munderover> <mi>&Sigma;</mi> <mrow> <mi>i</mi> <mo>=</mo> <mn>1</mn> </mrow> <mi>N</mi> </munderover> <msub> <mi>t</mi> <mrow> <mi>w</mi> <mo>,</mo> <mi>i</mi> </mrow> </msub> <mo>,</mo> </mrow></math> Or

Obj＝mint_t，max＝min(max{t_p，i+t_w，i})

When the guarantee of the delivery date of the workpiece and the improvement of the utilization rate of the equipment are simultaneously required, the scheduling objective function is set as follows:

<math><mrow> <mi>Obj</mi> <mo>=</mo> <mi>min</mi> <mrow> <mo>(</mo> <msub> <mi>c</mi> <mn>1</mn> </msub> <msub> <mi>t</mi> <mi>d</mi> </msub> <mo>-</mo> <msub> <mi>c</mi> <mn>2</mn> </msub> <mi>U</mi> <mo>)</mo> </mrow> <mo>=</mo> <mi>min</mi> <mrow> <mo>(</mo> <msub> <mi>c</mi> <mn>1</mn> </msub> <msub> <mi>t</mi> <mi>d</mi> </msub> <mo>-</mo> <msub> <mi>c</mi> <mn>2</mn> </msub> <mrow> <mo>(</mo> <mfrac> <mn>1</mn> <mi>KT</mi> </mfrac> <munderover> <mi>&Sigma;</mi> <mrow> <mi>k</mi> <mo>=</mo> <mn>1</mn> </mrow> <mi>K</mi> </munderover> <msub> <mi>T</mi> <mi>k</mi> </msub> <mo>)</mo> </mrow> <mo>&times;</mo> <mn>100</mn> <mo>%</mo> <mo>)</mo> </mrow> </mrow></math>

wherein c is₁、c₂Is a constant value of t_dFor average workpiece delay time, K is the number of production equipment in the system, T is the scheduling period, T_kIs the processing time of the device k.

3. A method according to claim 1 or 2, characterized in that: the method for determining the key factors for measuring the operation performance of the system comprises the following steps: the key factor for measuring the association performance of the equipment is the processing time of the equipment, the key factor for measuring the completion performance of the workpiece is the delay time of the workpiece, and the key factor for measuring the flow performance of the workpiece is the processing time of the workpiece and the waiting time of the workpiece.

4. A method according to claim 1, characterized in that: the extended process sequence planning tree is utilized to represent the process sequence planning flexibility of the workpiece and the machining path flexibility of the workpiece.

5. A scheduling system for implementing the method of claim 1, comprising a central controller (8), a loading and unloading station (4), a system buffer station (6), an automatic trolley (9) and processing equipment, characterized in that:

the processing equipment is provided with an equipment controller;

the blank enters a system buffer station (6) through a loading and unloading station (4) to wait for processing, and the finished product exits the system through the loading and unloading station (4);

the system buffer station (6) is used for temporarily storing the workpieces and is provided with a buffer station controller (5); the system buffer station (6) is provided with physical stations, each physical station is provided with a tray, and workpieces to be processed are clamped on the trays; the buffer controller (5) records the relative position of the physical station relative to the absolute origin of the system buffer station (6) and also records the state of the physical station;

the automatic rail trolley (9) moves among the loading and unloading station (4), the system buffer station (6) and the processing equipment, and an automatic tray taking/placing mechanism is attached to the automatic rail trolley;

the loading and unloading station (4), the system buffer station (6) and the processing equipment are respectively provided with a tray exchange station, each tray exchange station is provided with a position indicating element, and a position detecting element arranged on the automatic rail trolley (9) is used for detecting each tray exchange station so as to realize the accurate positioning of the automatic rail trolley (9);

the central controller (8) is respectively connected with the loading and unloading station display device (2), the loading and unloading station input device (3), the automatic rail trolley (9), the system buffer station controller (5) and the equipment controller to control the work of each part.

Images