CN108937588A - A kind of customization brewing system and method suitable for household espresso machine - Google Patents

Abstract

The invention discloses a customized brewing system and method suitable for household espresso coffee machines. A controller, a sensor, an actuator and a user interaction unit are built on the basis of an ordinary coffee machine to form a customized brewing system; the sensor includes a weighing Heavy module, thermal resistance, thermocouple, pressure gauge; actuator includes solid state relay and step-down module; user interaction unit is used for user to set coffee brewing mode, user can choose initial brewing temperature, temperature gradient mode and pressure mode, And whether to intervene in large flow; the controller drives the actuator through model-based feedforward and feedback control, and adjusts the brewing temperature, pressure and flow curve according to the coffee brewing mode set by the user; the controller passes test modeling and simulation The method calculates the controller parameters; on the basis of general coffee machine program control, the invention improves the brewing quality of espresso coffee by controlling the parameters of the brewing process, so that users can adjust the taste by themselves to meet the needs of customized brewing.

Description

A customized brewing system and method suitable for household espresso machines

technical field

The invention belongs to the technical field of coffee machines, and in particular relates to a customized brewing system and method suitable for household espresso machines.

Background technique

Espresso is a high-pressure brewed coffee. Hot water flows through the roasted and ground coffee at a pressure of about 9 bar, and through mechanical washing and dissolution, the substances in the coffee powder are brewed into the hot water to form an espresso drink.

After nearly a century of continuous improvement, the espresso machine has matured in production technology and mechanical design. Coffee machines generally include water tanks, boilers, pumps, brewing heads, powder bowls and other parts. The cold water in the water tank is drawn into the boiler under the action of the pump for heating. When the coffee machine is working, the pump is turned on, and the hot water in the boiler flows out of the boiler under the drive of the pump and reaches the brewing head. At the brewing head, the hot water flows through the water separator into several small uniform streams, which flow through the coffee grounds contained in the powder bowl. The boiler is generally equipped with a pressure relief valve. When the pipeline pressure is greater than the rated pressure, the pressure relief valve opens to maintain a constant pressure in the pipeline. Household coffee machines are generally small in size, use a vibrating pump, and are equipped with a small water storage boiler or a rapid heating boiler.

The single-chip microcomputer program control system is widely used in coffee machines, and there is a trend of intelligent development, which is reflected in the emergence and development of intelligent functions such as brewing monitoring, precise control and quality optimization. Coffee machine parameters such as temperature, pressure, coffee liquid volume, boiler liquid level, etc. are monitored, and the temperature and pressure in high-end coffee machines and large coffee machines are also controlled by PID closed-loop.

Coffee quality is very sensitive to brewing parameters such as temperature and pressure. Temperature affects coffee flavor by affecting the solubility and molecular kinetic energy of various substances in coffee, and pressure affects coffee flavor by affecting scouring force. Household coffee machines are generally equipped with small boilers or fast-heating boilers. Due to the small heat capacity, the temperature of the boiler fluctuates greatly during the brewing process. At present, there are some temperature control modules for boiler temperature control, mainly using simple PID feedback controllers, which have low precision for temperature control in the brewing stage.

The taste indicators of coffee, such as bitterness, sourness, and concentration, can have huge differences under different brewing parameters, and the taste preferences of users are not uniform. There is no recognized perfect taste indicator for espresso coffee. When brewing coffee of different types and particle sizes, the taste effect that users hope to achieve is not necessarily the same. The brewing process of household espresso machines is fixed, which cannot meet the diverse needs of consumers for customizing brewed espresso.

Therefore, by establishing a mathematical model of the coffee machine boiler, designing a feed-forward and feedback controller can improve the control effect, and on this basis make it possible for users to customize brewing.

Contents of the invention

The object of the present invention is to provide a customized brewing system and method suitable for domestic espresso coffee machines in view of the deficiencies in the prior art.

The object of the present invention is achieved through the following technical solutions: the present invention implements brewing control on the domestic small boiler espresso machine and the instant boiler espresso machine, thereby realizing customized brewing. The system of the present invention includes a coffee machine body, a controller, a sensor, an actuator and a user interaction unit;

The sensor includes a weighing module, a thermal resistance sensor, a thermocouple sensor and a pressure gauge; the weighing module is used to measure the weight of the coffee liquid flowing out from the coffee machine; the thermal resistance sensor is used to measure the boiler temperature of the coffee machine The thermocouple sensor is used to measure the temperature of the coffee liquid at the outlet of the coffee machine; the pressure gauge is used to measure the outlet pressure of the vibration pump of the coffee machine;

The actuator includes a solid-state relay and a bidirectional rectification step-down module; the solid-state relay is used to switch the heating wire to control the heating power of the boiler; the step-down module is used to control the power of the vibration pump to adjust the brewing pressure ;

The controller drives the solid-state relay and the step-down module through model-based feed-forward and feedback control, and regulates the brewing temperature, pressure and flow curve according to the coffee brewing mode set by the user; the controller is modeled and simulated through testing method to find the controller parameters;

The test modeling includes measuring the boiler transfer function and the control characteristics of the pump; the boiler is regarded as a two-input and one-out link, with flow and heating power as input and boiler temperature change rate as output, and the discrete transfer is obtained through system identification experiments Function model; the control characteristic of the pump refers to the relationship between the flow, pressure and the output of the controller (the input of the step-down module); since the flow control is realized by reducing the working voltage of the pump, for convenience, it can be considered that the output of the controller is related to the The power of the pump is proportional; use powder cakes of different thicknesses as constant flow resistance, measure the relationship between flow and pressure under different pump powers within the normal flow range, and obtain the control characteristic curve of the pump;

In order to reduce the difficulty of adjusting parameters in the design of feed-forward feedback controller, the simulation method is used to obtain the initial parameters, and then the parameters are fine-tuned in combination with the coffee machine; the static gain of the boiler transfer function model is used to design the static feed-forward link of temperature control, and the pump’s The control characteristic curve determines the feedforward amount of pressure control; based on the primary real data, use the test model to obtain the temperature change caused by the controller output change, and superimpose to obtain the simulation output; the feedback controller can be obtained through the controller simulation design parameter value;

The user interaction unit is used for the user to set the coffee brewing mode and display the measured value curve; the user can select the initial brewing temperature, temperature gradient mode and pressure mode, and whether to intervene in the large flow, and set the brewing that meets their own needs parameter.

Further, the weighing module is fixed at the coffee outlet, such as a cantilever parallel beam load cell with a measuring range of 1 kg can be selected to weigh the cup filled with coffee, and subtract the weight of the empty coffee cup to obtain the coffee weight; The density is relatively close to that of water, and is basically fixed. The coffee volume can be obtained by converting the coffee weight information; the coffee flow rate can be obtained by performing differential calculations on the measured values at two moments before and after the coffee volume;

The thermal resistance sensor can be used to measure the temperature of the boiler with high precision, generally reaching 0.1°C, which is convenient for application in temperature control; Close to the boiler; the shell of the thermal resistance should be as small as possible to reduce the temperature measurement lag; in order to connect with the controller, the thermal resistance generally needs to be equipped with a transmission module;

The thermocouple sensor is used to measure the temperature of the coffee liquid at the outlet of the coffee machine, and the thermal response speed is fast; the shell of the thermocouple should be as small as possible to reduce the hysteresis of temperature measurement, and the shell should meet the requirements of food hygiene; in order to be connected with the controller, the thermocouple Generally need to match the transmission module;

The pressure gauge is used to measure the outlet pressure of the vibration pump of the coffee machine; it should have the function of digital remote transmission; for a general 9bar coffee machine, the range of the pressure gauge can be 0-1.6MPA; when installing the pressure gauge, pay attention to the water pump of the coffee machine For vibration problems, the pipeline connected to the pressure gauge should have a pressure-bearing function.

The advantage of the temperature control of the solid-state relay is that it is easy to be driven by a single-chip microcomputer, and the actuator is a linear link; the solid-state relay is generally a thyristor circuit, so it should be noted that the switching frequency of the input signal cannot be too high. For general coffee machine temperature control, you can choose The control frequency is 2Hz; for general household coffee machine vibration pump power regulation, a two-way rectification step-down module must be used to drive the water pump to work normally.

Further, the acquisition of the boiler transfer function specifically includes:

Before conducting the identification experiment, first determine the approximate time constant of the system; input a heating power square wave signal with a period of 200 seconds and an amplitude of 20% into the system, record the temperature change, and calculate the transition time of the system step response T;

In order to simplify the identification experiment, the two inputs are identified separately. When identifying the relationship between one input and the output, the other input remains constant; when identifying the transfer function from heating power to temperature change rate, a fully extracted powder cake can be used as Constant flow resistance to keep flow constant;

The input signal of the identification experiment adopts a periodic square wave signal, the signal period is greater than 2T, the signal amplitude is about 20%, and the signal time length is about 25 minutes;

Consider the ARX model as the system model, and use the least squares method to identify the system model. Before the model identification, low-pass filtering and de-averaging are performed on the measured values; the appropriate model order and pure lag order are selected to obtain the transfer of the system function.

Further, when the controller detects that the current flow rate exceeds the flow limit, it indicates that the brewing powder is too little, the grinding is too coarse, or there is a powder pressing defect, and a major error has occurred in the brewing; in order to make the coffee as thick as possible, the control The device gives up the pressure set point control and switches to the flow overriding control state. The flow overriding control uses a PI controller to reduce the flow rate below the upper limit of the flow rate.

Further, through temperature control, heating up brewing, constant temperature brewing and cooling down brewing can be realized. The temperature control adopts the control method of static feed-forward plus PID feedback, and feed-forward is carried out for the flow rate and temperature change rate set value; through pressure control , It can realize brewing in different pressure modes. The pressure control adopts the control method of static feedforward and PI feedback, and performs feedforward for the pressure setting value.

Further, the setting range of the initial brewing temperature is 90°C to 110°C, and the temperature gradient mode includes brewing at reduced temperature, brewing at constant temperature and brewing at elevated temperature, and the set value curve of the controller is generated according to the mode set by the user, Realize customized brewing; when brewing at low temperature, the set value of the temperature change rate controller is -0.15°C/s; when brewing at constant temperature, the set value of the temperature change rate controller is 0°C/s; The setting value of the change rate controller is 0.15°C/s; for common 9bar household coffee machines, the pressure modes selected by the user include 9bar, 8bar and 7bar; when the user selects 9bar for brewing, the pump of the coffee machine works at full power; when When the user chooses 8bar brewing, the pressure is controlled by the set value of 8bar when brewing coffee; when the user chooses 7bar brewing, the coffee machine pump works at a lower power; Intervene, and due to reasons such as too coarse powder, too little powder or powder pressing error, etc., when the measured flow rate exceeds the upper limit, the controller enters the flow override control state and reduces the flow rate to below the flow upper limit.

Further, the controller communicates with the user interaction unit via bluetooth or wirelessly; the user interaction unit includes selection buttons for setting the initial brewing temperature, temperature gradient mode and pressure mode, and whether to intervene in large flow, It also includes editable text boxes for setting coffee brewing volume and flow upper limit, and a drawing area for displaying the current boiler temperature, outlet temperature, brewing flow rate, brewing pressure, and coffee volume real-time curves, so that users can understand brewing dynamics.

A custom brewing method suitable for domestic espresso machines, comprising the following steps:

Boiling water stage control: After the controller receives the instruction to start making coffee, it will control the temperature of the boiling water stage, so that the boiler temperature reaches the set initial brewing temperature, and keeps it stable for a period of time, so that the hot water temperature reaches a uniform , and prevent the transient change of temperature from interfering with the temperature control of the brewing stage; when the temperature remains stable for a period of time near the set value, it enters the brewing stage;

Brewing stage control: including boiler temperature change rate and pressure setting value control; determine the temperature change rate setting value and pressure setting value according to the mode set by the user; drive the solid state relay and the pressure reduction module to regulate the brewing temperature and pressure pressure;

When the brewed coffee volume reaches the set value, a cup of coffee is made and the brewing is stopped.

Furthermore, before the control of the brewing stage, it is judged according to the user’s setting whether pre-soaking is required. The way of pre-soaking is to open the outlet valve and turn off the pump, so that the residual hot water in the pipeline flows into the powder cake without pressurization, and the The puff is wetted, causing it to expand and become more impact resistant; after the pre-infusion, the pump is turned on and the brew phase control begins.

Furthermore, when the user sets the intervention on the large flow, when the controller detects that the current flow exceeds the flow upper limit, it indicates that the brewing powder is too little, the grinding is too coarse, or there is a powder pressing defect, and there is a major error in brewing ;In order to make the coffee thicker as much as possible, the controller should give up the pressure setting value control, switch to the flow overriding control state, and reduce the flow rate to below the upper limit of the flow rate.

The beneficial effects of the present invention are: a controller, a sensor, an actuator, and a user interaction unit are built on the basis of an ordinary coffee machine to form a customized brewing system; the controller drives a solid-state relay and The step-down module regulates the brewing temperature, pressure and flow curve according to the coffee brewing mode set by the user; the controller obtains the controller parameters through test modeling and simulation methods; through the establishment of the mathematical model of the coffee machine boiler, the design of the feedforward The feedback controller can improve the control effect; the user can choose the initial brewing temperature, temperature gradient mode and pressure mode, and whether to intervene in the large flow, and set the brewing parameters that meet their needs; the present invention is based on the general coffee machine program control , through the parameter control of the brewing process, the quality of espresso brewing is improved, so that users can adjust the taste by themselves to meet the needs of customized brewing.

Description of drawings

Figure 1 is the implementation steps of customized brewing;

Fig. 2 is the control strategy of the controller;

Figure 3 is an example of custom brewing.

Detailed ways

In order to facilitate the understanding of those skilled in the art, the specific implementation steps of the present invention will be further described below in conjunction with the drawings and embodiments.

The specific implementation of the present invention can be divided into four parts: measurement and control system construction, system test modeling, simulation parameter adjustment and user interaction unit design, as shown in FIG. 1 .

The first part is the construction of the measurement and control system. The measurement and control system is composed of sensors and actuators; the sensors include weighing modules, thermal resistance sensors, thermocouple sensors and pressure gauges; the weighing modules are used to measure the weight of the coffee liquid flowing out from the coffee machine; the thermal resistance The sensor is used to measure the boiler temperature of the coffee machine; the thermocouple sensor is used to measure the temperature of the coffee liquid at the outlet of the coffee machine; the pressure gauge is used to measure the outlet pressure of the vibrating pump of the coffee machine; the actuator includes a solid state relay and a bidirectional rectification and pressure reduction module; the solid state relay is used to switch the heating wire to control the heating power of the boiler; the pressure reduction module is used to control the power of the vibrating pump to adjust the brewing pressure;

The weighing module is fixed at the coffee outlet. For example, a cantilever parallel beam load cell with a measuring range of 1 kg can be selected to weigh the cup containing coffee, and subtract the weight of the empty coffee cup to obtain the coffee weight; It is relatively close and basically fixed. The coffee volume can be converted through the coffee weight information; the coffee flow can be obtained by differential calculation of the measured values at two moments before and after the coffee volume;

The thermal resistance sensor can be used to measure the temperature of the boiler with high precision, generally reaching 0.1°C, which is convenient for application in temperature control; Close to the boiler; the shell of the thermal resistance should be as small as possible to reduce the temperature measurement lag; in order to connect with the controller, the thermal resistance generally needs to be equipped with a transmission module;

The thermocouple sensor is used to measure the temperature of the coffee liquid at the outlet of the coffee machine, and the thermal response speed is fast; the shell of the thermocouple should be as small as possible to reduce the hysteresis of temperature measurement, and the shell should meet the requirements of food hygiene; in order to be connected with the controller, the thermocouple Generally need to match the transmission module;

The pressure gauge is used to measure the outlet pressure of the vibration pump of the coffee machine; it should have the function of digital remote transmission; for a general 9bar coffee machine, the range of the pressure gauge can be 0-1.6MPA; when installing the pressure gauge, pay attention to the water pump of the coffee machine For vibration problems, the pipeline connected to the pressure gauge should have a pressure-bearing function.

The advantage of the temperature control of the solid-state relay is that it is easy to be driven by a single-chip microcomputer, and the actuator is a linear link; the solid-state relay is generally a thyristor circuit, so it should be noted that the switching frequency of the input signal cannot be too high. For general coffee machine temperature control, you can choose The control frequency is 2Hz; for general household coffee machine vibration pump power regulation, a two-way rectification step-down module must be used to drive the water pump to work normally.

The second part models the system test, measuring the boiler transfer function and pump control characteristics.

The boiler is regarded as a two-input and one-out link, with the flow rate and heating power as the input and the boiler temperature change rate as the output, and the discrete transfer function model is obtained through the system identification experiment; before the identification experiment, the approximate time constant of the system is first determined ;Input a heating power square wave signal with a period of 200 seconds and an amplitude of 20% into the system, record the temperature change, and obtain the transition time T of the system step response; in order to simplify the identification experiment, the two inputs are separately Identification, when identifying the relationship between one input and output, the other input remains constant; when identifying the transfer function from heating power to temperature change rate, a fully extracted powder cake can be used as a constant flow resistance to keep the flow constant; identification experiment The input signal adopts a periodic square wave signal, the signal period is greater than 2T, the signal amplitude is about 20%, and the signal time length is about 25 minutes; consider the ARX model as the system model, and use the least square method to identify the system model. Before the model identification, first Perform low-pass filtering and de-average processing on the measured value; select the appropriate model order and pure lag order to obtain the transfer function of the system.

The control characteristic of the pump refers to the relationship between the flow, pressure and the output of the controller (the input of the step-down module); since the flow control is realized by reducing the working voltage of the pump, for convenience, it can be considered that the output of the controller and the power of the pump It is directly proportional; use powder cakes of different thicknesses as constant flow resistance, measure the relationship between flow and pressure under different pump powers within the normal flow range, and obtain the control characteristic curve of the pump.

The third part is simulation tuning. In order to reduce the difficulty of adjusting parameters in the design of feed-forward feedback controller, the initial parameters are obtained by simulation method, and then the parameters are fine-tuned in combination with the coffee machine.

As shown in Figure 2, during the process of making a cup of coffee, the behavior of the controller is divided into the following stages: After receiving the instruction to start making coffee, it first controls the stage of boiling water so that the boiler temperature reaches the set initial brewing temperature, and keep it stable for a period of time, so that the temperature of hot water can be uniform, and prevent the transient change of temperature from interfering with the temperature control in the brewing stage. When the temperature remains stable for a period of time near the set value, it enters the brewing stage. First judge whether presoaking is required according to user settings. The method of presoaking is to open the outlet valve, close the pump, and let the residual hot water in the pipeline flow into the powder cake without pressurization, soaking the powder cake, causing it to expand and become more impact resistant. After the prepreg is completed, the pump is turned on, and the control of the brewing stage starts, which mainly includes the control of the boiler temperature change rate and the set value of the pressure. Determine the temperature change rate setpoint and pressure setpoint according to the mode set by the user. If the user has set the compensation function for large flow, when the controller detects that the current flow exceeds the flow limit, it indicates that the brewing powder is too little, the grinding is too coarse, or there is a powder pressing defect, and there is a major error in brewing. In order to make the coffee as thick as possible, the controller should give up the pressure set point control and switch to the flow override control state. When the brewed coffee volume reaches the set value, a cup of coffee is made and the brewing is stopped. For automated brewing, the controller should take over the switching of the pump, outlet valve, etc.

Temperature, pressure, and flow measurements are low-pass filtered before being applied to the control algorithm to calculate the controller output. The setting value of the temperature control in the boiling water stage is specified by the initial brewing temperature specified by the user, and the function is to make the boiler hot water reach the predetermined temperature before starting to brew coffee. Through the control of the set value of the temperature change rate, it is possible to realize heating up brewing, constant temperature brewing and cooling down brewing. The set value control of the temperature change rate adopts the control method of static feedforward and PID feedback. The fixed value is feed-forward. Brewing in different pressure modes can be realized through the control of the set value of the pressure. The control method of the set value of the pressure adopts the control method of static feed-forward plus PI feedback, and the feed-forward is performed on the set value of the pressure. Flow override control adopts PI controller. The controller output is the sum of feedforward and feedback. Among them, the feedback part only works when the controlled parameters have reached a stable state, so as to prevent the drastic changes of the controlled parameters in the early stage of the coffee machine brewing stage from interfering with the operation of the controller. The feedback part of the controller adopts position type PID, and cuts off the integral when the error is large or the integral action is too strong.

The static gain of the boiler transfer function model obtained through test modeling is used to design the static feedforward link of temperature control, and the parameter values of the PID feedback controller are obtained through controller simulation design. When adjusting parameters in simulation, based on a real temperature data, in each control cycle, first read the real temperature measurement value, and then calculate the temperature change caused by the controller output change according to the identified heating channel transfer function model , add the two to get the temperature measurement value during simulation, which is used to calculate the controller output, and so on.

Use the control characteristics of the pump to determine the amount of feedforward for the pressure control. According to the control characteristic curve of the pump measured by the coffee machine test model, when the flow rate is fixed at the ideal flow rate, the output of the flow controller has a roughly linear relationship with the pressure, and the feedforward amount of the pressure control can be designed according to this relationship. The design of PI feedback controller for pressure control is relatively simple, and the control target can be achieved by using weaker proportional and integral functions. When debugging the PI controller, it is necessary to prevent the impact of the controller output oscillation on the powder cake.

The fourth part is the design of the user interaction unit. The user interaction unit is used for the user to set the coffee brewing mode and display the measured value curve, so as to set the demand for customized brewing and monitor the actual control effect.

Users can choose the initial brewing temperature, temperature gradient mode and pressure mode, and whether to intervene in large flow. The initial brewing temperature setting range is 90 to 110°C, and the temperature gradient mode includes cooling brewing, constant temperature brewing and warming brewing cook. According to the mode set by the user, the set value curve of the controller is generated to realize customized brewing. When brewing at low temperature, the set value of the temperature change rate controller is -0.15°C/s; when brewing at constant temperature, the set value of the temperature change rate controller is 0°C/s; The fixed value is 0.15°C/s. For the common 9bar home coffee machine, the user-selectable pressure modes include 9bar, 8bar and 7bar. When the user chooses 9bar brewing, the pump of the coffee machine works at full power; when the user chooses 8bar brewing, the pressure is controlled by the set value of 8bar when brewing coffee; when the user chooses 7bar brewing, The machine pump works at a lower power. When the user chooses to intervene in the large flow rate, and the flow measurement value exceeds the upper limit due to reasons such as too coarse grinding, too little powder, or powder pressing errors, the controller enters the flow override control state and reduces the flow rate below the flow limit .

The user interaction unit can be made in the form of mobile APP, etc., and the controller communicates with the user interaction unit through bluetooth or wireless. In addition to the selection buttons for setting the initial brewing temperature, temperature gradient mode and pressure mode, and whether to intervene on large flow, the user interaction unit also includes editable text boxes for setting coffee brewing volume, flow upper limit, etc., and user interface In the drawing area that displays the current boiler temperature, outlet temperature, brewing flow rate, brewing pressure, and coffee volume real-time curves, so that users can understand the brewing dynamics.

Figure 3 is a case of customized brewing. By setting the temperature mode, the temperature of the boiler can be controlled to remain unchanged, rise and fall, and have an impact on quality indicators such as sourness, taste, and concentration.

The above describes the technical principles of the present invention in conjunction with specific embodiments. These descriptions are only for explaining the principles of the present invention, and cannot be construed as limiting the protection scope of the present invention in any way. Based on the explanations herein, those skilled in the art can think of other specific implementation modes of the present invention without creative efforts, and these modes will all fall within the protection scope of the present invention.

Claims (10)

1. A customized brewing system suitable for household espresso coffee machines, characterized in that it includes a coffee machine body, a controller, a sensor, an actuator and a user interaction unit; The sensor includes a weighing module, a thermal resistance sensor, a thermocouple sensor and a pressure gauge; the weighing module is used to measure the weight of the coffee liquid flowing out from the coffee machine; the thermal resistance sensor is used to measure the boiler temperature of the coffee machine The thermocouple sensor is used to measure the temperature of the coffee liquid at the outlet of the coffee machine; the pressure gauge is used to measure the outlet pressure of the vibration pump of the coffee machine; The actuator includes a solid state relay and a pressure reduction module; the solid state relay is used to switch the heating wire to control the heating power of the boiler; the pressure reduction module is used to control the power of the vibration pump to adjust the brewing pressure; The controller drives the solid-state relay and the step-down module through model-based feed-forward and feedback control, and regulates the brewing temperature, pressure and flow curve according to the coffee brewing mode set by the user; the controller is modeled and simulated through testing method to find the controller parameters; The test modeling includes measuring the boiler transfer function and the control characteristics of the pump; the boiler is regarded as a two-input and one-out link, the flow rate and heating power are input, the boiler temperature change rate is output, and the boiler transfer function is obtained through the system identification experiment. Function model; use powder cakes of different thicknesses as constant flow resistance, measure the relationship between flow and pressure under different pump powers within the normal flow range, and obtain the control characteristic curve of the pump; Use the simulation method to obtain the initial parameters of the feedforward feedback controller design, and then fine-tune the parameters combined with the coffee machine; use the static gain of the boiler transfer function model to design the static feedforward link of the temperature control, and use the control characteristic curve of the pump to determine the pressure control. Feed-forward amount; based on one real data, use the test model to obtain the temperature change caused by the controller output change, and superimpose to obtain the simulation output; The user interaction unit is used for the user to set the coffee brewing mode and display the measured value curve; the user can select the initial brewing temperature, temperature gradient mode and pressure mode, and whether to intervene in the large flow, and set the brewing that meets their own needs parameter. 2. A customized brewing system suitable for household espresso machines according to claim 1, wherein the weighing module is fixed at the coffee outlet to weigh the cups filled with coffee, and the empty cups are weighed. The coffee weight is obtained by subtracting the weight of the coffee cups; the coffee volume is obtained by converting the coffee weight information; the coffee flow is obtained by differential calculation of the measured values at two moments before and after the coffee volume; the thermal resistance sensor is used to measure the temperature of the boiler, and the thermal resistance is installed on the When the boiler is on, use heat-conducting glue and keep it as close as possible to the boiler; the shell of the thermal resistance should be as small as possible to reduce the temperature measurement lag; the thermocouple sensor is used to measure the temperature of the coffee liquid at the outlet of the coffee machine, and the shell of the thermocouple should be as small as possible To reduce temperature measurement hysteresis, and the shell should meet food hygiene requirements; the pressure gauge is used to measure the outlet pressure of the vibrating pump of the coffee machine, and should have digital remote transmission function, and the pipeline connected to the pressure gauge should have pressure bearing function. 3. A customized brewing system suitable for household espresso machines according to claim 1, wherein the acquisition of the boiler transfer function specifically includes: Before conducting the identification experiment, first determine the approximate time constant of the system; input a heating power square wave signal with a period of 200 seconds and an amplitude of 20% into the system, record the temperature change, and calculate the transition time of the system step response T; Identify the two inputs separately. When identifying the relationship between one input and the output, the other input remains constant; when identifying the transfer function from heating power to temperature change rate, use a fully extracted powder cake as a constant flow resistance to maintain Constant flow; The input signal of the identification experiment adopts a periodic square wave signal, the signal period is greater than 2T, the signal amplitude is 20%, and the signal time length is 25 minutes; Consider the ARX model as the system model, and use the least squares method to identify the system model. Before the model identification, low-pass filtering and de-averaging are performed on the measured values; the transfer function of the system is obtained by determining the model order and pure lag order. 4. A customized brewing system suitable for household espresso machines according to claim 1, wherein when the controller detects that the current flow exceeds the upper flow limit, it indicates a major error in brewing, and the controller Abandon the pressure set point control and switch to the flow overriding control state. The flow overriding control uses a PI controller to reduce the flow rate below the upper limit of the flow rate. 5. A custom-made brewing system suitable for household espresso machines according to claim 1, characterized in that, through temperature control, it can realize heating up brewing, constant temperature brewing and cooling down brewing, and the temperature control adopts static The control method of feedforward plus PID feedback is used to feedforward the set values of flow rate and temperature change rate; through pressure control, brewing in different pressure modes can be realized, and the pressure control adopts the control method of static feedforward plus PI The set value is fed forward. 6. A customized brewing system suitable for household espresso machines according to claim 1, wherein the setting range of the initial brewing temperature is 90 to 110°C, and the temperature gradient mode includes cooling brewing , Constant temperature brewing and warming up brewing, according to the mode set by the user, the set value curve of the controller is generated to realize customized brewing; when the temperature is down and brewing, the set value of the temperature change rate controller is -0.15°C/s; When brewing at constant temperature, the set value of the temperature change rate controller is 0°C/s; when brewing at elevated temperature, the set value of the temperature change rate controller is 0.15°C/s; for a regular 9bar household coffee machine, the pressure mode selected by the user Including 9bar, 8bar and 7bar; when the user selects 9bar for brewing, the pump of the coffee machine works at full power; when the user selects 8bar for brewing, the pressure is controlled by a set value of 8bar when brewing coffee; when When the user selects 7bar brewing, the coffee machine pump works at a lower power. 7. A customized brewing system suitable for household espresso machines according to claim 1, wherein the controller communicates with the user interaction unit via bluetooth or wireless; the user interaction unit includes It is used to set the initial brewing temperature, temperature gradient mode and pressure mode, and the selection buttons for whether to intervene in the large flow. It also includes editable text boxes for setting the coffee brewing volume and flow upper limit, and for displaying the current boiler temperature, outlet The drawing area for the temperature, brewing flow, brewing pressure, and coffee volume real-time curves, so that users can understand the brewing dynamics. 8. A custom-made brewing method suitable for household espresso coffee machines, comprising the following steps: Boiling water stage control: After the controller receives the instruction to start making coffee, it will control the temperature of the boiling water stage, so that the boiler temperature reaches the set initial brewing temperature, and keep it stable for a period of time before entering the brewing stage; Brewing stage control: including boiler temperature change rate and pressure setting value control; determine the temperature change rate setting value and pressure setting value according to the mode set by the user; drive the solid state relay and the pressure reduction module to regulate the brewing temperature and pressure pressure; When the brewed coffee volume reaches the set value, a cup of coffee is made and the brewing is stopped. 9. The customized brewing method according to claim 8, characterized in that before the control of the brewing stage, it is judged according to the user’s setting whether pre-soaking is required, and the way of pre-soaking is to open the outlet valve, turn off the pump, and let the pipeline Residual hot water flows into the pod without pressurization, soaking the pod, causing it to expand and become more shock-resistant; after pre-infusion, the pump is switched on and the brew phase control begins. 10. The customized brewing method according to claim 8, characterized in that, when the user sets the intervention on the large flow, when the controller detects that the current flow exceeds the flow limit, it indicates a major error in brewing, and the controller gives up Pressure setpoint control, switches to flow override control state, reduces flow below flow limit.