技术领域technical field
本发明属于电加工领域，更具体涉及一种超前两步预测的电火花加工自适应控制系统及方法。The invention belongs to the field of electrical machining, and more specifically relates to an adaptive control system and method for electrical discharge machining with two-step prediction in advance.
背景技术Background technique
电火花加工是利用浸在工作液中的电极用电源产生的放电脉冲进行电蚀，蚀除导电材料的一种加工方法。电火花加工过程是一个弱稳态过程。如果加工过程中冲油或排屑状况恶劣的情况下，会出现有害加工。有害加工的出现，使系统进入不稳定状态，放电状态变化剧烈，会烧伤加工工件的表面、影响加工效率。EDM is a processing method that uses the discharge pulse generated by the electrode immersed in the working fluid to perform electric erosion and remove conductive materials. The EDM process is a weak steady state process. Harmful machining can occur if oil flushing or chip removal conditions are poor during machining. The emergence of harmful processing makes the system enter an unstable state, and the discharge state changes drastically, which will burn the surface of the processed workpiece and affect the processing efficiency.
为了避免有害加工的出现，有效的方法是通过改变加工过程中的伺服运动参数或电参数，在不影响加工精度的前提下，使加工从有害加工阶段重新回到有效加工阶段，或提前改变伺服运动参数或电参数，避免加工进入有害加工阶段，其中抬刀周期是电参数的一种，其对电火花加工的精度起到一定的影响。In order to avoid harmful processing, the effective method is to return the processing from the harmful processing stage to the effective processing stage by changing the servo motion parameters or electrical parameters in the processing process without affecting the processing accuracy, or to change the servo motor in advance. Motion parameters or electrical parameters, to avoid machining from entering the harmful processing stage, among which the tool lifting cycle is a kind of electrical parameters, which has a certain impact on the accuracy of EDM.
发明内容Contents of the invention
(一)要解决的技术问题(1) Technical problems to be solved
本发明要解决的技术问题是如何在电火花加工过程中实时监测加工状况，并根据加工状况对抬刀周期作出调整，以保证电火花加工处于有效加工阶段。The technical problem to be solved by the present invention is how to monitor the machining status in real time during the EDM process, and adjust the tool lifting cycle according to the machining status, so as to ensure that the EDM is in an effective machining stage.
(二)技术方案(2) Technical solution
为了解决上述技术问题，本发明提供了一种超前两步预测的电火花加工自适应控制系统，所述系统包括：In order to solve the above technical problems, the present invention provides an adaptive control system for EDM with two-step prediction in advance, the system includes:
参数估计器，用于根据电火花加工过程中的间隙电压和间隙电流进行实时判断，得到放电状态，并将所述放电状态传传递给控制模块；所述参数估计器还用于根据所述放电状态以及控制模块提供的控制信号在线识别过程参数，并将识别得到的所述过程参数传递给参数计算器；The parameter estimator is used to judge in real time according to the gap voltage and gap current in the electric discharge machining process, obtain the discharge state, and transmit the discharge state to the control module; the parameter estimator is also used to judge according to the discharge state The state and the control signal provided by the control module identify the process parameters online, and pass the identified process parameters to the parameter calculator;
参数计算器，用于根据所述过程参数计算得到多个控制方程多项式，并将多个所述控制方程多项式传递给所述控制器；a parameter calculator, used to calculate a plurality of control equation polynomials according to the process parameters, and transmit the plurality of control equation polynomials to the controller;
控制器，用于根据所述多个控制方程多项式和所述放电状态，根据极点配置得到控制信号，并利用所述控制信号确定抬刀周期；A controller, configured to obtain a control signal according to the pole configuration according to the plurality of control equation polynomials and the discharge state, and use the control signal to determine the period of lifting the knife;
被控对象，用于根据所述抬刀周期进行调整；The controlled object is used to adjust according to the knife lifting cycle;
其中，电火花加工过程实变模型：Among them, the EDM process consolidation model:
所述参数计算器利用下面公式计算所述多个控制方程多项式：The parameter calculator calculates the plurality of governing equation polynomials using the following formula:
A(q)＝A1(q)D1(q)A(q)＝A1 (q)D1 (q)
B(q)＝B1(q)D1(q)B(q)＝B1 (q)D1 (q)
C(q)＝C1(q)A1(q)C(q)＝C1 (q)A1 (q)
qd-1B+C＝AR+BSqd-1 B+ C = AR + BS
式中，A(q)、B(q)、C(q)、Am(q)、Bm(q)、R、S、T为所述多个控制方程多项式；q为前向移位算子；d＝2为超前两步；B+表示B(q)中的稳定可约分部分；B-表示B(q)中的不稳定不可约分部分；R1＝R/B+；a1···ana、b1···bnb、c1···cnc以及d1···dnd均为所述过程参；am1···amnam、bm1···bmnbm为参考模型参数，e(t)为随机干扰信号。In the formula, A(q), B(q), C(q), Am (q), Bm (q), R, S, T are the multiple control equation polynomials; q is the forward shift Operator; d=2 is two steps ahead; B+ represents the stable reducible part in B(q); B- represents the unstable irreducible part in B(q); R1 =R/B+ ; a1···ana , b1···bnb , c1···cnc and d1···dnd are the process parameters; am1 ···amnam , bm1 ···bmnbm are Referring to model parameters, e(t) is a random interference signal.
优选地，所述参数估计器利用递归最小二乘法估计所述过程参数，并且所述过程参数为：Preferably, the parameter estimator estimates the process parameters using a recursive least squares method, and the process parameters are:
式中，a1···ana、b1···bnb、c1···cnc以及d1···dnd为所述过程参数，θ为表示所述过程参数的集合，na、nb、nc、nd表示过程参数的个数。In the formula, a1···ana , b1···bnb , c1···cnc and d1···dnd are the process parameters, θ is a set representing the process parameters, na andnb , nc , andnd represent the number of process parameters.
优选地，计算所述控制信号：Preferably, the control signal is calculated as:
Ru(t)＝Tuc-Sy(t)Ru(t)=Tuc -Sy(t)
式中，R、S、T为根据极点配置和超前两步预测计算出的多个控制方程多项式，uc为参考模型状态，y(t)为所述放电状态，u(t)为所述控制信号。In the formula, R, S, T are multiple control equation polynomials calculated according to the pole configuration and two-step ahead prediction, uc is the state of the reference model, y(t) is the discharge state, and u(t) is the control signal.
优选地，所述抬刀周期利用如下公式计算：Preferably, the tool lifting period is calculated using the following formula:
T＝u/kT=u/k
式中，T为所述抬刀周期，u为所述控制信号，k为抬刀周期控制系数。In the formula, T is the period of lifting the knife, u is the control signal, and k is the control coefficient of the period of lifting the knife.
优选地，所述参数估计器包括放电状态识别单元和放电状态判别单元；所述放电状态识别单元根据所述间隙电压和间隙电流识别得到有害放电状态、有效放电状态以及放电延迟状态，并传递给所述放电状态判别单元；所述放电状态判别单元计算所述有害放电状态的数目与所述有害放电状态、有效放电状态以及放电延迟状态的数目的和的比值，并将得到的比值作为所述放电状态。Preferably, the parameter estimator includes a discharge state identification unit and a discharge state discrimination unit; the discharge state identification unit identifies harmful discharge states, effective discharge states and discharge delay states according to the gap voltage and gap current, and transmits them to The discharge state judging unit; the discharge state judging unit calculates the ratio of the number of harmful discharge states to the sum of the number of harmful discharge states, effective discharge states, and discharge delay states, and uses the obtained ratio as the discharge state.
优选地，有效放电状态包括火花放电状态和瞬态拉弧状态，所述有害放电状态包括稳态拉弧状态和短路状态。Preferably, the effective discharge state includes a spark discharge state and a transient arc state, and the harmful discharge state includes a steady state arc state and a short circuit state.
优选地，所述系统还包括通讯模块，其与所述控制器、被控对象以及参数估计器连接；Preferably, the system further includes a communication module connected to the controller, the controlled object and the parameter estimator;
所述参数估计器还包括抬刀状态判断单元，其根据所述间隙电压和间隙电流进行实时判断，得到抬刀状态，生成并发送有效抬刀信号给所述通讯模块；所述通讯模块在接收到所述有效抬刀信号后，将所述控制器最新计算得到的所述抬刀周期传递给所述被控对象。The parameter estimator also includes a knife lifting state judging unit, which performs real-time judgment according to the gap voltage and gap current, obtains the knife lifting state, generates and sends an effective knife lifting signal to the communication module; After receiving the valid tool lift signal, the tool lift cycle newly calculated by the controller is transmitted to the controlled object.
根据上述系统进行超前预测的电火花加工自适应控制的方法，包括以下步骤：The method for performing the self-adaptive control of electrical discharge machining according to the above-mentioned system includes the following steps:
S1、根据电火花加工过程中的间隙电压和间隙电流进行实时判断，得到放电状态；S1. Real-time judgment is made according to the gap voltage and gap current in the EDM process, and the discharge state is obtained;
S2、在线识别过程参数；S2, online identification process parameters;
S3、根据所述过程参数计算得到多个控制方程多项式；S3. Calculate and obtain multiple control equation polynomials according to the process parameters;
S4、根据所述多个控制方程多项式和所述放电状态，利用极点配置方法计算得到控制信号，并利用所述控制信号确定抬刀周期；S4. According to the plurality of polynomials of the control equations and the discharge state, the pole configuration method is used to calculate the control signal, and the control signal is used to determine the period of lifting the knife;
其中，电火花加工过程实变模型：Among them, the EDM process consolidation model:
利用下面公式计算所述多个控制方程多项式：The plurality of governing equation polynomials are calculated using the following formula:
A(q)＝A1(q)D1(q)A(q)＝A1 (q)D1 (q)
B(q)＝B1(q)D1(q)B(q)＝B1 (q)D1 (q)
C(q)＝C1(q)A1(q)C(q)＝C1 (q)A1 (q)
qd-1B+C＝AR+BSqd-1 B+ C = AR + BS
式中，A(q)、B(q)、C(q)、Am(q)、Bm(q)、R、S、T为所述多个控制方程多项式；q为前向移位算子；d＝2为超前两步；B+表示B(q)中的稳定可约分部分；B-表示B(q)中的不稳定不可约分部分；R1＝R/B+；a1···ana、b1···bnb、c1···cnc以及d1···dnd均为所述过程参数；am1···amnam、bm1···bmnbm为参考模型参数，e(t)为随机干扰信号。In the formula, A(q), B(q), C(q), Am (q), Bm (q), R, S, T are the multiple control equation polynomials; q is the forward shift Operator; d=2 is two steps ahead; B+ represents the stable reducible part in B(q); B- represents the unstable irreducible part in B(q); R1 =R/B+ ; a1···ana , b1···bnb , c1···cnc and d1···dnd are the process parameters; am1 ···amnam , bm1 ···bmnbm are Referring to model parameters, e(t) is a random interference signal.
优选地，计算所述控制信号：Preferably, the control signal is calculated as:
Ru(t)＝Tuc-Sy(t)Ru(t)=Tuc -Sy(t)
式中，R、S、T为所述多个控制方程多项式，uc为参考模型状态，y(t)为所述放电状态，u(t)为所述控制信号；In the formula, R, S, T are the polynomials of the multiple control equations, uc is the state of the reference model, y(t) is the discharge state, and u(t) is the control signal;
所述步骤S4中的抬刀周期利用如下公式计算：The knife lifting period in the step S4 is calculated by the following formula:
T＝u/kT=u/k
式中，T为所述抬刀周期，u为所述控制信号，k为抬刀周期控制系数。In the formula, T is the period of lifting the knife, u is the control signal, and k is the control coefficient of the period of lifting the knife.
优选地，所述方法还包括确定有效抬刀状态步骤：Preferably, the method also includes the step of determining an effective knife lifting state:
根据所述间隙电压和间隙电流进行实时判断，得到抬刀状态，并在所述抬刀状态数目大于抬刀参考模型值时，生成有效抬刀信号；Carry out real-time judgment according to the gap voltage and gap current, obtain the knife lifting state, and generate an effective knife lifting signal when the number of the knife lifting states is greater than the knife lifting reference model value;
在所述有效抬刀信号生成时，将最新计算得到的所述抬刀周期传递给所述被控对象。When the effective tool raising signal is generated, the latest calculated tool raising cycle is transmitted to the controlled object.
(三)有益效果(3) Beneficial effects
本发明提供了一种超前两步预测的电火花加工自适应控制系统及方法，本发明通过对过程参数的在线识别，并利用在线识别的过程参数，根据本发明的控制模型以及当前的放电状态得到控制信号，实现对抬刀周期的实时调节，能够使加工维持在有效加工阶段，极大加强了系统的稳定性，并提高了加工效率。The present invention provides an adaptive control system and method for EDM with two-step prediction in advance. The present invention recognizes the process parameters online and utilizes the process parameters recognized online, according to the control model of the present invention and the current discharge state The control signal is obtained to realize the real-time adjustment of the tool lifting cycle, which can maintain the processing in the effective processing stage, greatly enhance the stability of the system, and improve the processing efficiency.
附图说明Description of drawings
为了更清楚地说明本发明实施例或现有技术中的技术方案，下面将对实施例或现有技术描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本发明的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的附图。In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. Those skilled in the art can also obtain other drawings based on these drawings without creative work.
图1为本发明的一个较佳实施例的超前两步预测的电火花加工自适应控制系统的结构示意图；Fig. 1 is the structural representation of the electric discharge machining adaptive control system of the two-step prediction in advance of a preferred embodiment of the present invention;
图2为本发明的另一个较佳实施例的超前两步预测的电火花加工自适应控制系统的结构示意图；Fig. 2 is the structural representation of the electric discharge machining adaptive control system of the two-step prediction in advance of another preferred embodiment of the present invention;
图3为本发明的一个较佳实施例的放电状态判断流程图；Fig. 3 is a flow chart for judging the discharge state of a preferred embodiment of the present invention;
图4为本发明的一个较佳实施例的超前两步预测的电火花加工自适应控制方法流程图；Fig. 4 is a flow chart of an adaptive control method for electric discharge machining of two-step prediction in advance of a preferred embodiment of the present invention;
图5a为利用传统方法进行电火花加工的放电状态示意图；Figure 5a is a schematic diagram of the discharge state of EDM using the traditional method;
图5b为利用本发明的系统或方法进行电火花加工的放电状态和抬刀周期的示意图；Fig. 5b is a schematic diagram of the discharge state and the tool lifting period of the electric discharge machining using the system or method of the present invention;
图5c为利用传统方法进行电火花加工与利用本发明的系统或方法进行电火花加工的放电状态和抬刀周期的对比示意图；Fig. 5c is a schematic diagram of the comparison of the discharge state and the tool lifting period between the electric discharge machining using the traditional method and the electric discharge machining using the system or method of the present invention;
图6a为图5b中1部分的放大示意图；Figure 6a is an enlarged schematic view of part 1 in Figure 5b;
图6b为图5b中2部分的放大示意图；Figure 6b is an enlarged schematic view of part 2 in Figure 5b;
图6c为图5b中3部分的放大示意图。Fig. 6c is an enlarged schematic view of part 3 in Fig. 5b.
具体实施方式detailed description
下面结合附图和实施例对本发明作进一步详细描述。以下实施例用于说明本发明，但不能用来限制本发明的范围。The present invention will be described in further detail below in conjunction with the accompanying drawings and embodiments. The following examples are used to illustrate the present invention, but should not be used to limit the scope of the present invention.
一种超前两步预测的电火花加工自适应控制系统，如图1所示，所述系统包括：An adaptive control system for electric discharge machining with two-step prediction in advance, as shown in Figure 1, the system includes:
参数估计器，用于根据电火花加工过程中的间隙电压和间隙电流进行实时判断，得到放电状态，并将所述放电状态传传递给控制模块；所述参数估计器还用于根据所述放电状态以及控制模块提供的控制信号在线识别过程参数，并将识别得到的所述过程参数传递给参数计算器；The parameter estimator is used to judge in real time according to the gap voltage and gap current in the electric discharge machining process, obtain the discharge state, and transmit the discharge state to the control module; the parameter estimator is also used to judge according to the discharge state The state and the control signal provided by the control module identify the process parameters online, and pass the identified process parameters to the parameter calculator;
参数计算器，用于根据所述过程参数计算得到多个控制方程多项式，并将多个所述控制方程多项式传递给所述控制器；a parameter calculator, used to calculate a plurality of control equation polynomials according to the process parameters, and transmit the plurality of control equation polynomials to the controller;
控制器，用于根据所述多个控制方程多项式和所述放电状态，根据极点配置计算得到控制信号，并利用所述控制信号确定抬刀周期；A controller, configured to calculate and obtain a control signal according to the pole configuration according to the plurality of control equation polynomials and the discharge state, and use the control signal to determine the knife-lifting period;
被控对象EDM，电火花加工机EDM作为被控对象，接收控制器发送的抬刀周期，进而实时调整抬刀周期；The controlled object EDM, the EDM as the controlled object, receives the tool lifting cycle sent by the controller, and then adjusts the tool lifting cycle in real time;
其中，电火花加工过程实变模型：Among them, the EDM process consolidation model:
所述参数计算器利用下面公式计算所述多个控制方程多项式：The parameter calculator calculates the plurality of governing equation polynomials using the following formula:
A(q)＝A1(q)D1(q)A(q)＝A1 (q)D1 (q)
B(q)＝B1(q)D1(q)B(q)＝B1 (q)D1 (q)
C(q)＝C1(q)A1(q)C(q)＝C1 (q)A1 (q)
qd-1B+C＝AR+BSqd-1 B+ C = AR + BS
式中，A(q)、B(q)、C(q)、Am(q)、Bm(q)、R、S、T为所述多个控制方程多项式；q为前向移位算子；d＝2为超前两步；B+，表示B(q)中的稳定可约分部分；B-，表示B(q)中的不稳定不可约分部分；R1＝R/B+；a1···ana、b1···bnb、c1···cnc以及d1···dnd均为所述过程参；am1···amnam、bm1···bmnbm为参考模型参数，e(t)为随机干扰信号。In the formula, A(q), B(q), C(q), Am (q), Bm (q), R, S, T are the multiple control equation polynomials; q is the forward shift operator; d=2 means two steps ahead; B+ , represents the stable reducible part in B(q); B- , represents the unstable irreducible part in B(q); R1 ＝R/B+ ; a1···ana , b1···bnb , c1···cnc and d1···dnd are the process parameters; am1 ···amnam , bm1 ···bmnbm is the reference model parameter, e(t) is the random interference signal.
上述系统内环由被控对象和控制器组成，其中控制器由极点配置的方法进行设计；外环则由参数估计器和控制方程多项式计算器所组成，其任务是辨识过程参数再按选定的设计方法综合出控制器参数，用以修改内环的控制器。该系统的特点是必须对过程或者被控对象的参数进行在线辨识估计，然后用参数的估计值和事先规定的性能指标在线综合出控制器的控制方程多项式，并据此对被控对象进行控制。经过多次地辨识和综合调节参数(即上述控制方程多项式)可以使系统的性能指标趋于最优。The inner loop of the above-mentioned system is composed of the controlled object and the controller, and the controller is designed by the pole configuration method; the outer loop is composed of the parameter estimator and the control equation polynomial calculator, and its task is to identify the process parameters and then press the selected The design method synthesizes the controller parameters to modify the controller of the inner loop. The characteristic of this system is that the parameters of the process or the controlled object must be identified and estimated online, and then the control equation polynomial of the controller is synthesized online with the estimated value of the parameter and the performance index specified in advance, and the controlled object is controlled accordingly. . The performance index of the system tends to be optimal after several times of identification and synthesis of adjustment parameters (that is, the polynomial of the above-mentioned control equation).
进一步地，所述参数估计器利用递归最小二乘法进行估计过程参数，并且所述过程参数为：Further, the parameter estimator uses the recursive least square method The process parameters are estimated, and the process parameters are:
式中，a1···ana、b1···bnb、c1···cnc以及d1···dnd为所述过程参数，θ为表示所述过程参数的集合，na、nb、nc、nd表示过程参数的个数。In the formula, a1···ana , b1···bnb , c1···cnc and d1···dnd are the process parameters, θ is a set representing the process parameters, na andnb , nc , andnd represent the number of process parameters.
进一步地，所述控制器计算所述控制信号：Further, the controller calculates the control signal:
Ru(t)＝Tuc-Sy(t)Ru(t)=Tuc -Sy(t)
式中，R、S、T为所述多个控制方程多项式，uc为参考模型状态，y(t)为所述放电状态，u(t)为所述控制信号。In the formula, R, S, T are polynomials of the multiple control equations, uc is the state of the reference model, y(t) is the discharge state, and u(t) is the control signal.
进一步地，所述抬刀周期利用如下公式计算：Further, the cycle of lifting the knife is calculated using the following formula:
Tdown＝u/kTdown =u/k
式中，Tdown为所述抬刀周期，u为所述控制信号，k为抬刀周期控制系数。In the formula, Tdown is the period of lifting the knife, u is the control signal, and k is the control coefficient of the period of lifting the knife.
进一步地，所述参数估计器包括放电状态识别单元和放电状态判别单元；所述放电状态识别单元的采集卡不断采集间隙电压和间隙电流，并根据所述间隙电压和间隙电流识别得到有害放电状态、有效放电状态以及放电延迟状态，并传递给所述放电状态判别单元；所述放电状态判别单元计算所述有害放电状态的数目与所述有害放电状态、有效放电状态以及放电延迟状态的数目的和的比值，并将得到的比值作为所述放电状态，图1中输出y为输出的放电状态。Further, the parameter estimator includes a discharge state identification unit and a discharge state discrimination unit; the acquisition card of the discharge state identification unit continuously collects the gap voltage and gap current, and obtains the harmful discharge state according to the gap voltage and gap current identification , effective discharge state and discharge delay state, and pass them to the discharge state discrimination unit; the discharge state discrimination unit calculates the number of the harmful discharge state and the number of the harmful discharge state, effective discharge state and discharge delay state and the ratio, and the obtained ratio is used as the discharge state, and the output y in FIG. 1 is the output discharge state.
有效放电状态包括火花放电状态和瞬态拉弧状态，所述有害放电状态包括稳态拉弧状态和短路状态。The effective discharge state includes spark discharge state and transient arc state, and the harmful discharge state includes steady state arc state and short circuit state.
进一步地，所述系统还包括连接下位机的通讯模块，如图2所示，其与所述控制器、被控对象以及参数估计器连接。所述参数估计器还包括抬刀状态判断单元，其根据所述间隙电压和间隙电流进行实时判断，得到抬刀状态，并在所述抬刀状态数目大于抬刀参考模型值时，生成并发送有效抬刀信号给所述通讯模块；所述通讯模块在接收到所述有效抬刀信号后，将所述控制器最新计算得到的所述抬刀周期。Further, the system also includes a communication module connected to the lower computer, as shown in FIG. 2 , which is connected to the controller, the controlled object and the parameter estimator. The parameter estimator also includes a knife lifting state judging unit, which performs real-time judgment according to the gap voltage and gap current to obtain the knife lifting state, and generates and sends the An effective knife-lifting signal is sent to the communication module; after the communication module receives the effective knife-lifting signal, it sends the knife-lifting period newly calculated by the controller.
具体的，如图2所示，参数估计器和通讯模块是并行模块，同时进行对放电状态的判别，和上、下位机间的通讯；当参数估计器中的放电状态被赋值成功以后，控制器调用放电状态，计算得出抬刀周期T；当参数估计器中生成的有效抬刀状态信号被通讯模块检测到时，通讯模块开始调用控制器计算出的T，并传输给被控对象EDM，使其按照抬到周期T改变抬刀周期，实现自适应控制。Specifically, as shown in Figure 2, the parameter estimator and the communication module are parallel modules, which simultaneously perform the discrimination of the discharge state and the communication between the upper and lower computers; when the discharge state in the parameter estimator is assigned successfully, the control The discharge state is called by the controller, and the tool lifting cycle T is calculated; when the effective tool lifting state signal generated in the parameter estimator is detected by the communication module, the communication module starts to call the T calculated by the controller, and transmits it to the controlled object EDM , so that it changes the tool lifting cycle according to the lifting cycle T to realize adaptive control.
综上，本发明的参数估计模块采用了递归的最小二乘法，控制模块采用了最小方差和极点配置的耦合方法构建，根据加工过程中的放电状态，实时控制电极的抬刀周期，可以极大地提高系统的稳定性和加工效率，并且使加工维持在有效加工阶段，保证了高效、稳定的加工过程。In summary, the parameter estimation module of the present invention adopts the recursive least squares method, and the control module adopts the coupling method of minimum variance and pole configuration to construct. According to the discharge state in the processing process, the lifting cycle of the electrode is controlled in real time, which can greatly improve the Improve the stability and processing efficiency of the system, and maintain the processing in the effective processing stage, ensuring an efficient and stable processing process.
另外上述系统的处理过程可以基于VC++平台，多线程运行，采用模块化编程，使被控对象(电火花加工EDM)按照预测值改变抬刀周期，实现了对抬刀周期的自适应控制。In addition, the processing process of the above system can be based on the VC++ platform, multi-threaded operation, and modular programming, so that the controlled object (EDM) can change the tool lifting cycle according to the predicted value, and realize the self-adaptive control of the tool lifting cycle.
总之，参数估计器用于根据放电状态以及控制器提供的控制信号在线识别过程参数，并根据识别得到的所述过程参数传递给参数计算器。In short, the parameter estimator is used to identify process parameters online according to the discharge state and the control signal provided by the controller, and transmit the identified process parameters to the parameter calculator.
上述判断放电状态的过程如下：The above process of judging the discharge state is as follows:
参数估计器通过采集卡不断对采集的间隙电压和电流进行采集和识别，得到有害放电状态、有效放电状态以及放电延迟状态，如图3所示。几种放电状态的数目分别累加，直至采集卡读入数据已达到存储上限，利用下面放电状态y的计算公式，对累计的放电状态数目进行计算，即求得有害放电状态的数目与所述有害放电状态、有效放电状态以及放电延迟状态的数目的和的比值，将得到的比值作为所述放电状态y。The parameter estimator continuously collects and identifies the collected gap voltage and current through the acquisition card, and obtains the harmful discharge state, effective discharge state and discharge delay state, as shown in Figure 3. The numbers of several discharge states are accumulated separately until the data read by the acquisition card has reached the upper limit of storage, and the calculation formula of the following discharge state y is used to calculate the accumulated number of discharge states, that is, the number of harmful discharge states and the number of harmful discharge states are obtained. The ratio of the sum of the number of the discharge state, the effective discharge state and the discharge delay state is used as the discharge state y.
其中，测量的放电状态分为以下五种：火花放电τspark、瞬态拉弧τtran.arc、稳态拉弧τstab.arc，放电延迟τdelay和短路τshort，其中火花放电、瞬态拉弧为有效放电状态，稳态拉弧和短路为有害放电状态，以有害放电率来定义放电状态y，即为：Among them, the measured discharge state is divided into the following five types: spark discharge τspark , transient arc τtran.arc , steady-state arc τstab.arc , discharge delay τdelay and short circuit τshort , among which spark discharge, transient The arc is an effective discharge state, and the steady-state arc and short circuit are harmful discharge states. The discharge state y is defined by the harmful discharge rate, which is:
计算具体过程如下：每一轮采集数据和判别放电状态完成后，将有效、有害状态和放电延迟状态相加，作为总的放电状态数目，并计算有害状态数与总放电状态数的比值，以此衡量此时放电状态的恶化程度，称之为放电状态。而后开始下一轮采集和判别。The specific calculation process is as follows: After each round of data collection and discrimination of the discharge state is completed, the effective, harmful state and discharge delay state are added together as the total number of discharge states, and the ratio of the number of harmful states to the total number of discharge states is calculated to obtain This measures the degree of deterioration of the discharge state at this time, which is called the discharge state. Then start the next round of collection and discrimination.
进一步地，上述计算控制信号的推导过程如下：Further, the derivation process of the above calculation control signal is as follows:
所述控制器采用的放电状态的预测模型为：The prediction model of the discharge state adopted by the controller is:
， ,
采用超前2步预测，特征方程可表示为：Using 2-step ahead prediction, the characteristic equation can be expressed as:
qd-1B+C＝AR+BSqd-1 B+ C = AR + BS
式中，d＝2表示超前2步预测，依此式，求得R和S，进而并根据极点配置的方法计算控制变量u(t)：In the formula, d=2 means 2-step ahead prediction, according to this formula, R and S are obtained, and then the control variable u(t) is calculated according to the pole configuration method:
式中，R1＝R/B+，最终求得控制变量u(t)：In the formula, R1 ＝R/B+ , finally obtain the control variable u(t):
利用上述系统进行超前两步预测的电火花加工自适应控制的方法，如图4所示，所述方法包括以下步骤：Utilize above-mentioned system to carry out the method for the electric discharge machining self-adaptive control of advance two-step prediction, as shown in Figure 4, described method comprises the following steps:
S1、根据电火花加工过程中的间隙电压和间隙电流进行实时判断，得到放电状态；S1. Real-time judgment is made according to the gap voltage and gap current in the EDM process, and the discharge state is obtained;
S2、在线识别过程参数；S2, online identification process parameters;
S3、根据所述过程参数计算得到多个控制方程多项式；S3. Calculate and obtain multiple control equation polynomials according to the process parameters;
S4、根据所述多个控制方程多项式和所述放电状态，根据极点配置计算得到控制信号，并利用所述控制信号确定抬刀周期；S4. According to the polynomials of the control equations and the discharge state, the control signal is calculated according to the pole configuration, and the knife lifting cycle is determined by using the control signal;
其中，电火花加工过程实变模型：Among them, the EDM process consolidation model:
利用下面公式计算所述多个控制方程多项式：The plurality of governing equation polynomials are calculated using the following formula:
A(q)＝A1(q)D1(q)A(q)＝A1 (q)D1 (q)
B(q)＝B1(q)D1(q)B(q)＝B1 (q)D1 (q)
C(q)＝C1(q)A1(q)C(q)＝C1 (q)A1 (q)
qd-1B+C＝AR+BSqd-1 B+ C = AR + BS
式中，A(q)、B(q)、C(q)、Am(q)、Bm(q)、R、S、T为所述多个控制方程多项式；q为前向移位算子；d为超前步数；B+，表示B(q)中的稳定可约分部分；B-，表示B(q)中的不稳定不可约分部分；R1＝R/B+；a1···ana、b1···bnb、c1···cnc以及d1···dnd均为所述过程参；am1···amnam、bm1···bmnbm为参考模型参数，e(t)为随机干扰信号。In the formula, A(q), B(q), C(q), Am (q), Bm (q), R, S, T are the multiple control equation polynomials; q is the forward shift Operator; d is the number of advance steps; B+ , represents the stable reducible part in B(q); B- , represents the unstable irreducible part in B(q); R1 = R/B+ ; a1···ana , b1···bnb , c1···cnc and d1···dnd are the process parameters; am1 ···amnam , bm1 ···bmnbm are Referring to model parameters, e(t) is a random interference signal.
进一步地，所述步骤S4中计算所述控制信号：Further, the control signal is calculated in the step S4:
Ru(t)＝Tuc-Sy(t)Ru(t)=Tuc -Sy(t)
式中，R、S、T为所述多个控制方程多项式，uc为参考模型状态，y(t)为所述放电状态，u(t)为所述控制信号；In the formula, R, S, T are the polynomials of the multiple control equations, uc is the state of the reference model, y(t) is the discharge state, and u(t) is the control signal;
所述步骤S4中的抬刀周期利用如下公式计算：The knife lifting period in the step S4 is calculated by the following formula:
T＝u/kT=u/k
式中，T为所述抬刀周期，u为所述控制信号，k为抬刀周期控制系数。In the formula, T is the period of lifting the knife, u is the control signal, and k is the control coefficient of the period of lifting the knife.
进一步地，所述方法还包括确定有效抬刀状态步骤：Further, the method also includes the step of determining an effective knife lifting state:
根据所述间隙电压和间隙电流进行实时判断，得到抬刀状态，并在所述抬刀状态数目大于抬刀参考模型值时，生成有效抬刀信号；Carry out real-time judgment according to the gap voltage and gap current, obtain the knife lifting state, and generate an effective knife lifting signal when the number of the knife lifting states is greater than the knife lifting reference model value;
在所述有效抬刀信号生成时，将最新计算得到的所述抬刀周期传递给所述被控对象When the effective tool lift signal is generated, the latest calculated tool lift cycle is delivered to the controlled object
由于上述方法是与上述装置相对应的，所以不再对方法进行赘述。Since the above method corresponds to the above device, the method will not be described in detail here.
图5a为利用传统方法进行电火花加工的放电状态示意图，可以看出传统方法由于抬刀周期为定周期，随着加工深度增加，排屑情况越来越差，导致加工进入有害加工阶段，放电状态越来越差且无法抑制。而本发明系统或方法，如图5b所示，能够适应性地改变抬刀周期，当放电状态变差时，周期T迅速减小，即抬刀频率升高，使排屑状况好转，从而使放电状态稳定在设定值附近。随着加工深度增加排屑变差，T越来越小，从而维持更长时间的稳定加工，获得较大的深径比，由于有效放电数目多，也使得加工时间缩短，效率极大提高。图5c为利用传统方法进行电火花加工与利用本发明的系统或方法进行电火花加工的放电状态和抬刀周期的对比示意图，图中可明显观察到，传统方法(即最上面的图的部分)的放电状态在0.1左右，而本发明的系统或方法的放电状态稳定在设定值值0.01左右(图5c的下面两个图部分)，只有个别放电状态升至0.1，而后立即改善，并稳定在设定值附近。Figure 5a is a schematic diagram of the discharge state of EDM using the traditional method. It can be seen that the traditional method has a fixed period of tool lifting. As the processing depth increases, the chip removal situation becomes worse and worse, resulting in harmful processing. The state is getting worse and worse and cannot be suppressed. However, the system or method of the present invention, as shown in Figure 5b, can adaptively change the period of lifting the knife. When the discharge state becomes worse, the period T decreases rapidly, that is, the frequency of lifting the knife increases, so that the chip removal situation improves, so that The discharge state is stable near the set value. As the processing depth increases, the chip removal becomes worse, and T becomes smaller and smaller, so as to maintain stable processing for a longer time and obtain a larger depth-to-diameter ratio. Due to the large number of effective discharges, the processing time is also shortened and the efficiency is greatly improved. Figure 5c is a schematic diagram of the comparison of the discharge state and the tool lifting period between the traditional method of EDM and the system or method of the present invention. It can be clearly observed in the figure that the traditional method (that is, the part of the uppermost figure) ) discharge state is about 0.1, while the discharge state of the system or method of the present invention is stable at about 0.01 set value (the lower two graph parts of Fig. 5c), only individual discharge state rises to 0.1, and then improves immediately, and stable around the set value.
附图6a、6b、6c为附图5b中三个部分的局部放大图。图6a为图5b中1部分的放大图，体现了在加工伊始，排屑状况良好的情况下，放电状态始终稳定在设定值附近，此时u保持最大值从而获得最快的加工速度。图6b为2部分的放大图，体现了排屑状况逐渐变差的过程中，u随着放电状态变化而调整的具体过程：当放电状态恶化并且高于设定值，u迅速减小，使抬刀频率升高从而改善放电状况；当放电状态良好并低于设定值，u逐渐升高，以获得较快的加工速度。图6c为3部分的放大图，体现了加工末期排屑状况极差的情况下，放电状态较差，因此u维持在最小值以获得最快的抬刀频率，从而最大程度地改善放电状态。Accompanying drawing 6a, 6b, 6c are the partial enlarged views of three parts in accompanying drawing 5b. Fig. 6a is an enlarged view of part 1 in Fig. 5b, which shows that at the beginning of processing, when the chip removal condition is good, the discharge state is always stable near the set value. At this time, u maintains the maximum value to obtain the fastest processing speed. Figure 6b is an enlarged view of part 2, which reflects the specific process of adjusting u with the change of discharge state during the process of chip removal gradually getting worse: when the discharge state deteriorates and is higher than the set value, u decreases rapidly, so that The frequency of lifting the knife increases to improve the discharge condition; when the discharge condition is good and lower than the set value, u increases gradually to obtain a faster processing speed. Figure 6c is an enlarged view of part 3, which shows that when the chip removal condition is extremely poor at the end of machining, the discharge state is poor, so u is maintained at the minimum value to obtain the fastest tool lifting frequency, thereby improving the discharge state to the greatest extent.
上述方法通过对过程参数的在线识别，并利用在线识别的过程参数，根据本发明的控制模型以及当前的放电状态得到控制信号，实现对抬刀周期的实时调节。对应于上述方法，本发明同时公开了一种系统，可以采用VC++模块化编程，能够使加工维持在有效加工阶段，极大加强了系统的稳定性，并提高了加工效率。The above method realizes the real-time adjustment of the knife-lifting cycle through the online identification of the process parameters, and using the online identification of the process parameters to obtain the control signal according to the control model of the present invention and the current discharge state. Corresponding to the above method, the present invention also discloses a system, which can adopt VC++ modular programming, can maintain the processing in an effective processing stage, greatly strengthen the stability of the system, and improve the processing efficiency.
以上实施方式仅用于说明本发明，而非对本发明的限制。尽管参照实施例对本发明进行了详细说明，本领域的普通技术人员应当理解，对本发明的技术方案进行各种组合、修改或者等同替换，都不脱离本发明技术方案的精神和范围，均应涵盖在本发明的权利要求范围当中。The above embodiments are only used to illustrate the present invention, but not to limit the present invention. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art should understand that various combinations, modifications or equivalent replacements of the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention, and all should cover Within the scope of the claims of the present invention.
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