CN105759615A - Fault-tolerant flexible small piece assembly control method based on collaborative Petri network - Google Patents

Abstract

A kind of fault tolerant flexibility smallclothes assembly control method based on the Petri network that can cooperate,Include the following steps: 1. to provide Petri net model generality mathematical definition; 2. by for the Petri network workflow of each sub- product be described as an open chain,Acyclic Petri network workflow; 3. the Petri network workflow between different sub- products is combined,Connection; Definition | | indicate sub- product mix,Different assembly collaboration process control tasks is completed in different sub- product Petri network combinations,And complete different target product tasks; 4. the supply of assembly system raw material is failed,Assembly execution acts the influence not in place to system with fault-tolerant scaling function F (C) to characterize,Transitional link of the F (C) comprising the Petri network that can cooperate There is raw material supply in the somewhere p of whole process to be unsuccessfully expressed as reducing δ (p) amp; amp at p; gt; 0, the size of control Δ (mc) guarantees the robustness of assembly system. Working flexibility of the present invention is preferable, controls fault tolerant.

Description

Fault-tolerant flexible small part assembly control method based on collaborative Petri network

Technical Field

The invention relates to the field of automatic manufacturing, in particular to a fault-tolerant flexible small part assembly control method based on a collaborative Petri network.

Background

A method for complex small part assembly and flow control is one of the hot points and difficulties in the field of automatic manufacturing control engineering. In 2008, F.S.Hsieh and the like establish a Petri network model oriented to assembly of components and analyze the assembly and disassembly processes of complex mechanical components, so that the fault tolerance and the robustness of the whole system when the raw material supply fails in the operation process are effectively improved. In 2010, J.Huang et al analyzed the electronic circuit socket connection assembly process and proposed an electronic device assembly method, so that an assembly system could complete the port docking of multiple transmission lines of an electronic circuit. In 2011, the assembly process of small and medium-sized parts is analyzed and solved by a Hessian model by D.J.Cappeleri et al, so that the manipulator can complete the assembly work of small nail holes. In 2012, a.n.das et al proposed a multi-scale assembly and packaging system Model (MASP), and analyzed the whole process of robot assembly, so that the robot can complete the multi-degree-of-freedom assembly of products. In 2014, C.W.Chou et al proposed a multi-target hybrid genetic algorithm (MO-HGA) for the LCD assembly process, so that the LCD screens meeting different user requirements can be simultaneously produced in the sequencing assembly process of the TFT-LCD liquid crystal screen crystal units. In 2015, H.P.Chen et al put forward a Gaussian Process Regression Bayesian Optimization Algorithm (GPRBOA) on the basis of a Gaussian regression algorithm (GPR) to learn control parameters, so that the defects that an accurate mathematical model of a robot is difficult to obtain and the efficiency of the existing industrial robot is low are overcome. Wang et al uses a cooperative dynamic control algorithm to unify the three modes of the control method: the independent mode, the dependent mode and the semi-dependent mode control the motion mode of the redundant double-arm robot and the required force, so that the double-arm robot can be better applied to engineering assembly.

Through a general review of the research on the key problems, no research report on the assembly method of the fault-tolerant flexible small parts is found at home and abroad currently. Therefore, it is very necessary to provide a fault-tolerant flexible small part assembly control method based on a collaborative Petri network.

Disclosure of Invention

In order to overcome the defects of poor working flexibility and no control fault tolerance of the conventional small part assembly control method, the invention provides the fault-tolerant flexible small part assembly control method based on the cooperative Petri network, which has good working flexibility and control fault tolerance.

The technical scheme adopted by the invention for solving the technical problems is as follows:

a fault-tolerant flexible small part assembly control method based on a collaborative Petri network comprises the following steps:

① shows a general mathematical definition of the Petri Net model, i.e. a four-element expression, G ═ P, T, W, m₀) Where P denotes all site-restricted elements, T denotes a restriction factor of the product schedule, W denotes a relationship (P × T) ∪ (T × P) → {0,1}, m denotes a relationship (P × T) between the production site and the product schedule₀Initial state information for the entire system: p → Z^|P|Z is a non-negative integer; based on the definition, a production flow task beat logic sequence branch and a raw material combination task beat logic branch are given, namely a so-called subproduct Petri net and a raw material flow Petri net;

② describe the Petri Net workflow for each sub-product as an open-chain, acyclic Petri Net workflowWherein,refers to a single-input single-output node,refers to a node having only an input and no output,means a node having only an output and no input, and

③ based on the principle of minimum cost, combining the queue combination optimization method to provide the production event optimization combination flow capable of accommodating multiple sub-product assembly targets, the realization process is as follows, combining and connecting the Petri net work flow among different sub-products, defining | to represent the sub-product combination, and giving two Petri nets G₁＝(P₁,T₁,W₁,m₁₀) And G₂＝(P₂,T₂,W₂,m₂₀)，G₁||G₂＝(P,T,W,m₀) In the above expression:

P＝P₁∪P₂,T＝T₁∪T₂(1)

$W(p,t)=\left\{\begin{array}{c}{W}_1(p,t)p\∈P_1,t\∈T_1\\ W_2(p,t)p\∈P_2,t\∈T_2\end{array}\right.---\left(2\right)$

$T(p,t)=\left\{\begin{array}{c}{T}_1(t,p)p\∈P_1,t\∈T_1\\ T_2(t,p)p\∈P_2,t\∈T_2\end{array}\right.---\left(3\right)$

$m_0\left(p\right)=\left\{\begin{array}{c}{m}_{10}\left(p\right),p\∈P_1\\ m_{20}\left(p\right),p\∈P_2\end{array}\right.---\left(4\right)$

wherein W (p, t) represents an assembly workflow link, p represents a node position variable, m represents a feed stream variable, and t represents a time factor;

considering the operation, different sub-product Petri networks are combined to complete different assembly cooperation process control tasks and different target product tasks;

④ the influence of failure in raw material supply and poor assembly action on the system is represented by a fault tolerance scale function F (C) comprising a transition link of a collaborative Petri netBy Delta (m)_c) To indicate the failure of raw material supply in a certain link, to indicate the interference of the failure of the work material on the system, and the failure of raw material supply in a certain position p of the whole process is indicated as reduction in the position p (p)>0; correction of production flow errors by parallel path execution and single step back method, control of delta (m)_c) So that f (c) takes the maximum value in its range, the robustness of the assembled system can be effectively ensured.

The technical conception of the invention is as follows: aiming at the characteristics and the technological requirements of the assembling and disassembling process of small electromechanical products, a Petri net model considering the assembling and executing cooperation process is established.

Based on the model, aiming at different production task requirements, a production flow task beat logic sequence branch and a raw material combination task beat logic branch are given, namely a so-called subproduct Petri net and a raw material flow Petri net; based on the principle of minimum cost, a queue combination optimization method is combined, a production event optimization combination flow capable of accommodating various sub-product assembly targets is provided, and the flexible requirements of production tasks are met.

According to the influences of failure in raw material supply and failure in assembly execution action on the fault tolerance and production efficiency of the whole subassembly assembly system during assembly of the small component assembly system, the production flow errors are corrected by a parallel path execution and single step backspacing method, so that the fault tolerance and robustness of the whole system during the process fault are effectively guaranteed.

The invention has the following beneficial effects: 1) the production event optimization combination process capable of accommodating multiple sub-product assembly targets meets the flexible requirements of production tasks.

2) The error of the production flow is corrected by the parallel path execution and single step rollback method, so that the fault tolerance and robustness when the flow fault occurs in the whole system operation process are effectively ensured.

Drawings

Fig. 1 is a schematic diagram of a flexible fault-tolerant small-piece assembly Petri net model, wherein four thick ellipses comprise fault-tolerant auxiliary channels, and two thin ellipses are parallel cooperative channels.

Detailed Description

The invention is further described below with reference to the accompanying drawings.

Referring to fig. 1, a fault-tolerant flexible small part assembly control method based on a collaborative Petri net is used for establishing a Petri net model considering an assembly execution collaboration process aiming at characteristics and process requirements of an assembly and disassembly process of small part electromechanical products, and is shown in fig. 1.

Based on the model, aiming at different production task requirements (models, specifications and the like), a production flow task beat logic sequence branch and a raw material combination task beat logic branch are given, namely a so-called subproduct Petri net and a raw material flow Petri net.

Based on the minimum cost principle, a queue combination optimization method is combined, a production event optimization combination flow capable of accommodating multiple sub-product assembly targets is given, and the flexible requirements of production tasks are met; according to the influences of failure in raw material supply and failure in assembly execution action on the fault tolerance and production efficiency of the whole subassembly assembly system during assembly of the small-piece electromechanical product assembly system, the production flow errors are corrected by a parallel path execution method (shown in figure 1) and a single step backspacing method, so that the fault tolerance and robustness of the whole system during the operation process of the whole system during flow faults are effectively guaranteed.

The Petri network model for executing the cooperation process in consideration of assembly comprises the following main technical routes: combining a workflow Petri Net model with a feed flow Petri Net model by replacing each sub-product node of an assembly target sub-product dependency Petri Net with the workflow Petri Net, as shown in the attached figure 1, wherein the related processing steps are as follows:

① shows a general mathematical definition of the Petri Net model, i.e. a four-element expression, G ═ P, T, W, m₀) In the above expression, P denotes all site-limiting elements, T denotes a limiting factor of product scheduling, W denotes a relationship (P × T) ∪ (T × P) → {0,1} of production site and product scheduling (m)₀Initial state information for the entire system: p → Z^|P|And Z is a non-negative integer.

② describe the Petri Net workflow for each sub-product as an open-chain, acyclic Petri Net workflowIn the above-mentioned expression, the expression,refers to a single-input single-output node,refers to a node having only an input and no output,means a node having only an output and no input, and

③ combining and connecting the Petri net work flow among different sub-products in consideration of the cooperability and the work flexibility of the assembly execution process, defining | to represent the sub-product combination, and giving two Petri nets G₁＝(P₁,T₁,W₁,m₁₀) And G₂＝(P₂,T₂,W₂,m₂₀)，G₁||G₂＝(P,T,W,m₀). In the above expression:

P＝P₁∪P₂,T＝T₁∪T₂(1)

$W(p,t)=\left\{\begin{array}{c}{W}_1(p,t)p\∈P_1,t\∈T_1\\ W_2(p,t)p\∈P_2,t\∈T_2\end{array}\right.---\left(2\right)$

$T(p,t)=\left\{\begin{array}{c}{T}_1(t,p)p\∈P_1,t\∈T_1\\ T_2(t,p)p\∈P_2,t\∈T_2\end{array}\right.---\left(3\right)$

$m_0\left(p\right)=\left\{\begin{array}{c}{m}_{10}\left(p\right),p\∈P_1\\ m_{20}\left(p\right),p\∈P_2\end{array}\right.---\left(4\right)$

wherein W (p, t) represents an assembly workflow link, p represents a node position variable, m represents a feed stream variable, and t represents a time factor.

In consideration of the operation, different sub-product Petri network combinations can complete different assembly cooperation process control tasks and different target product tasks, and the cooperability and the production task flexibility of the assembly process are reflected.

④ considering the fault tolerance of the assembly process, the influence of the failure of raw material supply and the poor assembly action on the system is characterized by a fault tolerance scale function F (C) comprising a transition link of a collaborative Petri netBy Delta (m)_c) To indicate a failure of material supply in a certain link, to indicate a disturbance of the system by a failure of work material, and the occurrence of a failure of material supply in p in a certain point of the whole process can be indicated as a decrease in p (p)>0; correction of production flow errors by parallel path execution and single step back method, control of delta (m)_c) So that f (c) takes the maximum value in its range, the robustness of the assembled system can be effectively ensured.

Based on the above processing steps, the present embodiment provides an example of a control process with the low-pressure air switch as an object, and the specific contents are as follows:

as shown in FIG. 1, the oval portion represents each product subassembly, denoted by h_iIt is shown that there are a total of 10 sub-components. h is₁Is a raw material component of a low-voltage electrical appliance power supply module without inputOutput to p₁Node pointp₁Completing the assembly of the power management chip and the minimum system thereof; h is₂Is a raw material component of a main control part of a low-voltage electrical appliance, and has no inputOutput to p₂Node pointp₂And the working node completes the assembly of the main control chip and the minimum system thereof.

For h₃Completing the assembly of the control part of the electric appliance with the input p₁,p₂Two nodesp₃Assembly of Signal driver chips, p₅Assembly of isolating optocouplers, p₆Assembly of peripheral executive relays, p₄Assembly of the overcurrent protection part of the power supply, p₇Assembly of a switching transformer, p₈Power supply circuit assembly, p₉And finishing the connection of the main control module and the power supply module.

For h₄Completing the assembly of the signal acquisition part with input p₁,p₂Two nodesp₁₀Operational amplifier power supply chip assembly, p₁₁Assembly of peripheral electronic components of power supply chip, p₁₂Assembly of operational amplifier circuits, p₁₃Mounting of the sensor, p₁₄The acquisition module is connected with the power supply. h is₅Electric appliance housing forming unit, p₁₆Injection of plastic particles, p₁₇And pressing and forming the shell. h is₆And assembling an external output interface. h is₅、h₆Output to node p₂₀And finishing the assembly of the shell and the external interface. When h is generated₃、h₄、h₃、h₆After the subassembly modules are successfully built, products meeting the requirements of different users can be assembled in different combination modes. h is₃、h₄Passing through node P₁₅Low-voltage electrical appliance product h capable of being directly assembled without casing₇，h₈And h₉The two assembling processes assemble the low-voltage electrical appliance products with different grades through different application environments, and the final three products with different requirements pass through a node P₂₇Into h₁₀And (5) packaging and boxing are finished.

Finally, it should also be noted that the above-mentioned list is only one specific embodiment of the invention. It is obvious that the invention is not limited to the above embodiments, but that many variations are possible. All modifications which can be derived or suggested by a person skilled in the art from the disclosure of the present invention are to be considered within the scope of the invention.

Claims (1)

1. A fault-tolerant flexible small part assembly control method based on a collaborative Petri network is characterized by comprising the following steps: the method comprises the following steps:

① shows a general mathematical definition of the Petri Net model, i.e. a four-element expression, G ═ P, T, W, m₀) Where P denotes all site-restricted elements, T denotes a restriction factor of the product schedule, W denotes a relationship (P × T) ∪ (T × P) → {0,1}, m denotes a relationship (P × T) between the production site and the product schedule₀Initial state information for the entire system: p → Z^|P|Z is a non-negative integer; based on the above definition, toProducing a production flow task beat logic sequence branch and a raw material combination task beat logic branch, namely a so-called subproduct Petri net and a raw material flow Petri net;

② describe the Petri Net workflow for each sub-product as an open-chain, acyclic Petri Net workflowWherein,refers to a single-input single-output node,refers to a node having only an input and no output,means a node having only an output and no input, and

③ based on the principle of minimum cost, combining the queue combination optimization method to provide the production event optimization combination flow capable of accommodating multiple sub-product assembly targets, the realization process is as follows, combining and connecting the Petri net work flow among different sub-products, defining | to represent the sub-product combination, and giving two Petri nets G₁＝(P₁,T₁,W₁,m₁₀) And G₂＝(P₂,T₂,W₂,m₂₀)，G₁||G₂＝(P,T,W,m₀) In the above expression:

P＝P₁∪P₂,T＝T₁∪T₂(1)

$W(p,t)=\left\{\begin{array}{c}{W}_1(p,t)p\∈P_1,t\∈T_1\\ W_2(p,t)p\∈P_2,t\∈T_2\end{array}\right.---\left(2\right)$

$T(p,t)=\left\{\begin{array}{c}{T}_1(t,p)p\∈P_1,t\∈T_1\\ T_2(t,p)p\∈P_2,t\∈T_2\end{array}\right.---\left(3\right)$

$m_0\left(p\right)=\left\{\begin{array}{c}{m}_{10}\left(p\right),p\∈P_1\\ m_{20}\left(p\right),p\∈P_2\end{array}\right.---\left(4\right)$

wherein W (p, t) represents an assembly workflow link, p represents a node position variable, m represents a feed stream variable, and t represents a time factor;

considering the operation, different sub-product Petri networks are combined to complete different assembly cooperation process control tasks and different target product tasks;

④ the influence of failure in raw material supply and poor assembly action on the system is represented by a fault tolerance scale function F (C) comprising a transition link of a collaborative Petri netBy Delta (m)_c) To indicate the failure of raw material supply in a certain link, to indicate the interference of the failure of the work material on the system, and the failure of raw material supply in a certain position p of the whole process is indicated as reduction in the position p (p)>0; correction of production flow errors by parallel path execution and single step back method, control of delta (m)_c) So that f (c) takes the maximum value in its range, the robustness of the assembled system can be effectively ensured.