Temperature Following Control Method for Dyeing Liquid Process Based on Temperature and Speed Regulation

Abstract

The method for controlling the process temperature following of dye liquor based on temperature and speed adjustment measures the temperature of the dye liquor to calculate the deviation from the set temperature, calculates the set value of the temperature and speed in real time according to the temperature deviation to obtain the deviation between the temperature and speed, thereby obtaining the opening degree of the pneumatic diaphragm regulating valve, and indirectly realizing the precise control of the dye liquor temperature and speed, so as to achieve the design purpose of stepless speed regulation and high-precision temperature following and temperature and speed control. During the printing and dyeing process, according to the requirements of the printing and dyeing process for temperature and temperature and speed indicators, the controller compares the real-time monitored temperature with the process temperature; by measuring the temperature of the dye liquor, calculates the deviation from the set temperature, calculates the set value of the temperature and speed according to the temperature deviation, calculates the deviation from the actual temperature and speed in real time, and controls the opening degree of the pneumatic diaphragm regulating valve to indirectly realize the control of the dye liquor temperature and speed.

Description

Technical Field

[0001] The present invention provides a temperature following and temperature - speed control method for the dyeing process of overflow dyeing machines, belonging to the technical field of printing and dyeing equipment. Background Art

[0002] Currently, overflow dyeing equipment is widely used in the domestic fabric printing and dyeing industry for the pretreatment and dyeing of various knitted grey fabrics such as pure cotton, pure polyester, polyester - cotton, spandex, etc. It is particularly suitable for dyeing new synthetic fibers and superfine fibers with high added value. At the same time, it can also be used for fabric scouring, bleaching, pre - shrinking, alkali reduction and other processes.

[0003] The overflow dyeing machine is a widely used dyeing equipment in existing printing and dyeing factories. Its working principle is that the dye liquor is pumped out from the bottom of the dye vat by the main pump, sent to the heat exchanger for heating, and then enters the overflow tank at the front end of the dye vat. Two or more downward - inclined overflow pipes are installed in parallel in the overflow tank. The fabric is circulated by the driving of the active fabric - guiding roller and the overflow of the dye liquor. Fabric printing and dyeing is a complex process affected by multiple factors, and these factors are coupled and interact with each other, making it difficult to control the dyeing quality. There are many main factors affecting the dyeing quality of the overflow dyeing machine, such as the dye liquor and its adding method, dyeing temperature, types of salts and alkali agents, dosage and adding method, dyeing time, dye liquor bath ratio, etc. The dyeing process has very strict requirements for temperature control. The heating, heat preservation and cooling of the dye liquor must meet the process requirements, otherwise, defective products such as color difference, vat difference, uneven coloring, etc. will be produced.

[0004] In the existing technology, when the overflow dyeing machine is dyeing, the accuracy of temperature control is relatively low. Due to the differences in different environments and machines, the actual temperature curve during the dyeing process deviates greatly from the ideal set curve, which will correspondingly lead to related dyeing quality problems, resulting in poor dyeing efficiency and high production costs, and unable to meet the needs of modern production processes and high - efficiency mass production. In addition, due to the low temperature control level, a large amount of water resources will be wasted, the environmental protection cost investment will be increased, and a satisfactory printing and dyeing quality control effect cannot be obtained.

[0005] In view of this, this patent application is specifically proposed. Summary of the Invention

[0006] The dye liquor process temperature following control method based on temperature - speed regulation according to the present invention aims to solve the problems existing in the prior art. By measuring the dye liquor temperature to calculate the deviation from the set temperature, and calculating the set value of the temperature - speed in real - time according to the temperature deviation to obtain the temperature - speed deviation, thereby obtaining the opening degree of the pneumatic diaphragm regulating valve, indirectly realizing the precise control of the dye liquor temperature and temperature - speed, in order to achieve the design purpose of stepless speed regulation and high - precision temperature following and temperature - speed control.

[0007] To achieve the above design objective, for the temperature following control method of the dye solution process based on temperature and speed adjustment, during the printing and dyeing process, according to the requirements of the printing and dyeing process for temperature and temperature change rate indicators, the controller compares the real-time monitored temperature with the process temperature; by measuring the temperature of the dye solution, calculates the deviation from the set temperature, and calculates the set value of the temperature change rate based on the temperature deviation, and in real time calculates the deviation from the actual temperature change rate, and controls the opening of the pneumatic diaphragm regulating valve to indirectly achieve the control of the dye solution temperature and temperature change rate;

[0008] The real-time dye solution temperature (Ts) is measured by a temperature sensor installed between the dye solution outlet of the heat exchanger and the dye solution inlet of the main cylinder. The relationship between the real-time dye solution temperature Ts and the temperature change rate V is:

[0009]

[0010] where V is the real-time temperature change rate, with the unit of °C / min;

[0011] The control law of the temperature change rate controller adopts the incremental PID algorithm. At the kth moment, the PID position discrete algorithm is:

[0012]

[0013] where u is the controller output; K P is the controller amplification factor; T I is the controller integral time, with the unit of min; T D is the controller differential time, with the unit of min; TS is the controller differential time, with the unit of min;

[0014] Let the temperature change rate control increment be Δu, then there is:

[0015]

[0016] Furthermore, based on Δu(k) = u(k) - u(k - 1) (17)

[0017] The iterative incremental temperature change rate control algorithm is as follows:

[0018] u(k) = u(k - 1) + Δu(k)

[0019] or (19)

[0020] u(k) = u(0) + Δu(k)

[0021] Furthermore, when the set temperature change rate Vset is less than 0.2 °C / min,

[0022] K P ′ = K P / α (20)

[0023] TI ' = T I / β (21)

[0024] where α is the reduced magnification factor;

[0025] β is the multiple for increasing the integral action;

[0026] Substitute the above formulas (20) and (21) into formula (18) to obtain

[0027]

[0028] According to the magnitude of the temperature rate, the self-setting of PID parameters can be realized to ensure the control accuracy of the temperature rate, thereby indirectly realizing the control of the temperature.

[0029] As described above, the advantages of the dye liquor process temperature following control method based on temperature rate regulation in this application are:

[0030] 1. This application can meet the requirements of the dyeing industry process for temperature control accuracy and stability. Through the temperature following and temperature rate control means in the dyeing process, a multi-parameter and high-precision control is achieved. The control means has the characteristics of a small overshoot, intelligence, and high controllability, and can automatically detect and accurately control the temperature trend in the dyeing process, achieving the effects of rapid heating, cooling, and stable heat preservation.

[0031] 2. This application can effectively maintain the temperature condition of the dye liquor according to the process requirements, which not only improves the dyeing effect and ensures the product quality, but also significantly improves the production efficiency and reduces the production cost. At the same time, it avoids the waste of water resources in the dyeing process and reduces the environmental protection pressure.

[0032] 3. This application is an intelligent method that comprehensively applies technologies such as dyeing process, automatic control, mechatronics, soft measurement technology, and computer monitoring, thus laying a solid foundation for the digital, intelligent, and information-based development of the overflow dyeing industry technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is the process and system structure schematic diagram of an overflow dyeing machine applying the control method of this application;

[0034] Figure 2 is the preset curve graph of the process dye liquor temperature;

[0035] Figure 3 is the real-time control schematic diagram of the temperature rate follow-up system;

[0036] Figure 4 is the heating and heat preservation curve graph;

[0037] Figure 5It is a temperature setting curve graph. Detailed implementation manners

[0038] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0039] Embodiment 1. The present application proposes a method for controlling the temperature following of a dyeing solution process based on temperature and speed adjustment, based on the Figure 1 overflow dyeing machine process and system structure shown in the figure. In order to meet the requirements of the dyeing process for temperature control accuracy and stability, the overflow dyeing machine includes a dyeing vat, a main pump, a heat exchanger, a nozzle, a temperature sensor, a control system, a pneumatic diaphragm regulating valve, etc. During the printing and dyeing process, operations such as heating up, keeping warm, and cooling down the dyeing solution in the dyeing vat are required. The heat exchange medium for heating up and keeping warm is steam, and the heat exchange medium for cooling down is cold water. The heat exchange is all realized through the heat exchanger, that is, only one medium can flow through the heat exchanger within a certain period of time. That is to say, it is impossible to cool down during the heating up and keeping warm processes, and the cooling only comes from the heat dissipation of the equipment itself.

[0040] Based on the principle of gas-liquid overflow temperature and speed adjustment, during the printing and dyeing process, the dyeing solution at the bottom of the dyeing vat is sent to the heat exchanger for heating or cooling with the main pump as the power, so that the temperature of the dyeing solution reaches the temperature required by the process. Then, the dyeing solution is sprayed on the fabric by the nozzle to achieve the purpose of dyeing. At the same time, the dyed fabric moves downward along with the liquid flow, and the dyeing solution naturally falls to the bottom of the dyeing vat, and works in such a cycle. When the dyeing solution is heated, steam passes through the heat exchanger, and when it is cooled, cold water passes through the heat exchanger. According to the requirements of the printing and dyeing process for temperature and temperature and speed indicators, the controller compares the temperature monitored in real time with the process temperature; by measuring the temperature of the dyeing solution, calculates the deviation from the set temperature, and calculates the set value of the temperature and speed in real time based on the temperature deviation, and calculates the deviation from the actual temperature and speed, and controls the opening degree of the pneumatic diaphragm regulating valve to indirectly realize the control of the temperature and speed of the dyeing solution, so as to achieve the purpose of controlling the temperature and speed.

[0041] As Figure 2 shown, the process dyeing solution temperature preset curve includes three stages: heating up, keeping warm, and cooling down. The dyeing process consists of one or more stages of heating up, keeping warm, and cooling down, which is specifically determined by the fabric dyeing.

[0042] The mathematical model for setting the process dyeing solution temperature established during the dyeing process is as follows:

[0043]

[0044] When the temperature reaches T2, T3, and T4, it is the constant temperature stage. Therefore, V2 = V4 = V6 = 0, and Equation (1) can be adjusted to:

[0045]

[0046] As Figure 3As shown in the real-time control principle of the temperature-speed servo system, the control law of the temperature controller adopts the incremental PID algorithm. At time k, the discrete formula for the temperature deviation Te of the controller is as follows:

[0047] Te(k) = Tset(k) - T S (k) (3)

[0048] At time k, the discrete formula for the PID position of the temperature controller is as follows:

[0049]

[0050] Among them, Vset is the output value of the temperature controller, unit: °C / min;

[0051] K TP is the amplification factor of the temperature controller;

[0052] T TI is the integral time of the temperature controller, unit: min;

[0053] T TD is the differential time of the temperature controller, unit: min;

[0054] TS is the sampling period of the system, unit: min;

[0055] Correspondingly, at time k - 1, the discrete formula for the PID position of the temperature controller is as follows:

[0056]

[0057] Subtracting Equation (5) from Equation (4) gives the control increment as:

[0058] ΔV set (k) = V set (k) - V set (k - 1) (6)

[0059] Among them, ΔVset is the output increment of the temperature controller;

[0060] Substituting Equations (4) and (5) into Equation (6) at time k, we get

[0061]

[0062] The above formula (7) is usually called the differential PID incremental algorithm;

[0063] From Equation (7), it can be transformed into:

[0064] V set (k) = V set (k - 1) + ΔV set (k)

[0065] or (8)

[0066] V set V(k)=V set (0)+ΔV set V(k)

[0067] The above formulas (7) and (8) are iterative incremental temperature PID control algorithms respectively.

[0068] Due to the problem that the system temperature of the existing overflow dyeing machine is uncontrollable when overheating, this application proposes a method of segmented temperature and speed control. That is, the state control of temperature is aimed at controlling the temperature, and the expected curve of the segmented temperature is as Figure 4 shown.

[0069] Specifically, according to the temperature difference ΔT between the real-time dye liquor temperature Ts and the set temperature T set of the dyeing process, the speed setting value V set is determined, and the controller makes the speed V follow V set in real time to achieve the purpose of controlling the temperature.

[0070] Assume that at time t0, the magnitude of the temperature difference ΔT is TE. According to the magnitude of the temperature difference ΔT, the speed setting value can be set in segments to achieve continuous stepless control. Then there is:

[0071]

[0072] where V set is the speed setting value, unit: °C / min;

[0073] V0 is the initial speed setting value, unit: °C / min;

[0074] ΔT is the temperature difference between the heat preservation temperature Th and the real-time temperature Ts, unit: °C;

[0075] TE is a constant, and its value makes ΔT≈0 when V set becomes very small within the specified time tn - t0;

[0076] ω is the attenuation coefficient;

[0077] t is the time, unit: min;

[0078] According to the above formula (9), the curve of the speed setting value V set is as Figure 5 shown.

[0079] Assume that the deceleration process lasts for tn - t0 = m minutes, the sampling period is TS, and the total number of samplings is n = m / TS.

[0080] That is, after n samplings, ΔT≈0 and Vset≈0. Since ΔT = Th - Ts, the sign of Vset should be the same as that of ΔT. Discretizing the variable part of the above formula (9) gives:

[0081] V set = sgn(ΔT)·V0·e -ω·i·TS (i = 0, 1, 2…n) (10)

[0082] where m is the regulation process time, unit: min;

[0083] n is the number of regulations during the regulation process time;

[0084] sgn(ΔT) takes the sign of ΔT;

[0085] TS is the sampling period, unit: min;

[0086] i is the i-th sampling;

[0087] According to the above derivation process, when i = n, Vset = 0.05 °C / min, which can effectively meet the requirements of temperature control accuracy. Substituting this parameter into equation (10) and solving gives:

[0088]

[0089] Based on the above analysis and derivation, in the case of uncontrollable temperature, a follow-up control system theory and a conventional PID algorithm are adopted to achieve temperature control based on temperature rate control.

[0090] Applying this application to an overflow dyeing machine as Figure 1 shown, only the set temperature T of the dye liquor in the dyeing process needs to be given set , and the initial temperature rate V0 can be determined according to the magnitude of the temperature difference ΔT.

[0091] Specifically, the real-time dye liquor temperature Ts is measured by a temperature sensor installed between the dye liquor outlet of the heat exchanger and the dye liquor inlet of the main cylinder. The relationship between the real-time dye liquor temperature Ts and the temperature rate V is:

[0092]

[0093] where V is the real-time temperature rate, unit: °C / min.

[0094] Since the sampling period is TS and k is the k-th sampling, discretizing equation (12) gives

[0095]

[0096] The control law of the temperature rate controller adopts an incremental PID formula. At the k-th moment, the discrete formula of the temperature rate deviation Ve of the controller is:

[0097] Ve(k) = Vset(k) - V(k) (14)

[0098] At time k, the discrete PID position formula is as follows:

[0099]

[0100] where u is the output value of the controller;

[0101] K P is the amplification factor of the controller;

[0102] T I is the integral time of the controller, unit: min;

[0103] T D is the derivative time of the controller, unit: min;

[0104] TS is the derivative time of the controller, unit: min;

[0105] From the above formula (15), at time k - 1, the discrete PID position formula is as follows:

[0106]

[0107] Set the temperature and speed control increment as Δu, then there is:

[0108] Δu(k) = u(k) - u(k - 1) (17)

[0109] where Δu is the output increment of the temperature and speed controller;

[0110] Substitute formula (15) and formula (16) into formula (17) at time k, then there is:

[0111]

[0112] The above formula (18) is usually called the differential PID increment formula;

[0113] From the above formula (17), the temperature and speed controller increment formula can be transformed into:

[0114] u(k) = u(k - 1) + Δu(k)

[0115] or (19)

[0116] u(k) = u(0) + Δu(k)

[0117] The above formula (18) and formula (19) are the iterative increment temperature and speed control formulas.

[0118] To better eliminate temperature deviation and enhance the stability of the system, when the temperature rate setting Vset is less than 0.2 °C / min, the proportional action is reduced and the integral action is increased, that is

[0119] K P ′ = K P / α (20)

[0120] T I ′ = T I / β (21)

[0121] where α is the reduced amplification factor;

[0122] β is the multiple for increasing the integral action;

[0123] Substitute the above formulas (20) and (21) into formula (18) to obtain:

[0124]

[0125] As described above, the self - setting of PID parameters can be realized according to the magnitude of the temperature rate to ensure the control accuracy of the temperature rate, thereby indirectly realizing the control of the temperature.

[0126] The control method proposed in this application has the characteristics of rapid response and good tracking performance, and can eliminate the deviation between the process dyeing solution temperature and the actual dyeing solution temperature in real time, thereby effectively improving the uniformity and stability of the dyeing quality.

[0127] As described above, combining the content of the solution given in the accompanying drawings and the description, similar technical solutions can be derived. Any solution content that does not depart from the structure of the present invention still belongs to the scope of the technical solutions of the present invention.

Claims

1. A temperature following control method for dyeing solution process based on temperature and speed adjustment, characterized in that: During the printing and dyeing process, according to the requirements of the printing and dyeing process for temperature and temperature rate indicators, the controller compares the temperature monitored in real time with the process temperature; by measuring the temperature of the dye liquor, calculates the deviation from the set temperature, and calculates the set value of the temperature rate based on the temperature deviation, and calculates the deviation from the actual temperature rate in real time, and controls the opening of the pneumatic diaphragm regulating valve to indirectly control the temperature and temperature rate of the dye liquor; The real-time dye liquor temperature Ts is measured by a temperature sensor installed between the dye liquor outlet of the heat exchanger and the dye liquor inlet of the main cylinder. The relationship between the real-time dye liquor temperature Ts and the temperature rate V is: where V is the real-time temperature rate, with the unit of °C / min; Since the sampling period is TS and k is the k-th sampling, discretizing Equation (12) gives At the k-th moment, the discrete formula for the temperature rate deviation Ve of the controller is: Ve(k) = Vset(k) - V(k) (14) The control law of the temperature rate controller adopts the incremental PID formula. At the k-th moment, the discrete formula for the PID position is: Among them, u is the output value of the controller; K P is the amplification factor of the controller; T I is the integral time of the controller, with the unit of min; T D is the derivative time of the controller, with the unit of min; TS is the derivative time of the controller, with the unit of min; From the above formula (15), at the (k - 1)-th moment, the discrete formula for the PID position is: It is set that the output increment of the temperature rate controller is Δu, then there is: Δu(k) = u(k) - u(k - 1) (17) At the k-th moment, substituting Equation (15) and Equation (16) into Equation (17), then there is: From the above formula (17), the incremental formula of the temperature rate controller can be transformed into: u(k) = u(k - 1) + Δu(k) or (19) u(k) = u(0) + Δu(k) When the set temperature rate Vset is less than 0.2 °C / min, K P ′ = K P / α (20) T I ′ = T I / β (21) where α is the reduced amplification factor; β is the factor for increasing the integral action; Substituting the above formula (20) and formula (21) into formula (18) to obtain: Realize the self-setting of PID parameters according to the magnitude of the temperature rate to ensure the control accuracy of the temperature rate, and thus indirectly realize the control of temperature.

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