Stacked screw machine sludge accumulation detection method and system based on sensorless torque estimation

Abstract

The invention relates to a method and a system for detecting sludge accumulation of a stacked screw machine based on sensorless torque estimation, and belongs to the technical field of sewage treatment equipment monitoring. According to the method, d-axis current and q-axis current are calculated through Clark and Parker transformation, and structural electromagnetic torque is constructed by combining the rotating speed of a permanent magnet synchronous motor predicted by a sliding-mode observer of a high-frequency injection method and combining an electromagnetic torque formula and structural parameters of the stacked screw machine. A sludge accumulation detection model is constructed based on the electromagnetic torque obtained through multiple observation and calculation of the sliding mode observer, and then a dynamic threshold value model of sludge accumulation is constructed to judge the sludge deposition condition. According to the method, the sludge accumulation in the stacked screw machine is judged through the sludge accumulation detection calculation model and the standard for dynamically judging the sludge deposition, the sludge component change is reflected through the self-adaptive factors, the application range of the machine for treating the sludge is widened, and the accuracy is improved.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment equipment monitoring technology, specifically relating to a method and system for detecting sludge accumulation in a screw press based on sensorless torque estimation. Background Technology

[0002] The main body of the screw press is a crucial transmission link. It consists of stacked fixed and moving rings with a spiral shaft running through it. As the spiral shaft rotates, it pushes the sludge from the inlet to the outlet. During this process, the gap between the fixed and moving rings gradually decreases from the inlet to the outlet, increasing the compressive pressure on the sludge and gradually squeezing out water, ultimately achieving solid-liquid separation. The dried sludge is discharged from the outlet, while the separated water flows out from the drain. The rotation of the spiral shaft is the core component driving the material through compression and dewatering. If the material contains a large amount of fiber, silt, or other impurities, these are prone to occur in narrow gaps (at the outlet) or between the spiral blades and the rings (fixed and moving rings), leading to poor dewatering or even blockage, increasing the motor load. To maintain speed, the motor increases torque. Manually observing sludge deposition is time-consuming and inefficient, while using sensors is costly. Therefore, a sensorless method for detecting sludge accumulation in the screw press is proposed.

[0003] By establishing a mathematical model for detecting sludge accumulation in screw presses, this method is more cost-effective than traditional torque sensors. It enables the detection of sludge inside the screw press and can also predict the next sludge accumulation time, which is of great significance for improving machine efficiency and extending machine life. Summary of the Invention

[0004] The purpose of this invention is to provide a method and system for detecting sludge accumulation in a screw press based on sensorless torque estimation. This invention is lower in cost and faster to implement than traditional torque sensors, while improving the intelligence level of the screw press. The sludge accumulation detection calculation model and the standard for dynamically judging sludge deposition enable the judgment of sludge accumulation inside the screw press. By using an adaptive factor to reflect changes in sludge composition, the applicability of the machine to sludge processing is increased, and the accuracy is improved.

[0005] To achieve the above objectives, the technical solution of this invention is: a method for detecting sludge accumulation in a screw press based on sensorless torque estimation. This method calculates the d-axis and q-axis currents using the Clark and Park transform, predicts the permanent magnet synchronous motor speed using a sliding mode observer combined with the high-frequency injection method, constructs the structural electromagnetic torque using the electromagnetic torque formula and the screw press structural parameters, builds a sludge accumulation detection model based on the electromagnetic torque calculated from multiple observations by the sliding mode observer, and then constructs a dynamic threshold model for sludge accumulation to determine the sludge deposition status.

[0006] Furthermore, the high-frequency injection method is a structure-adaptive high-frequency injection method based on the relevant parameters of the screw press.

[0007] Furthermore, the structure-adaptive high-frequency injection method is expressed as follows:

[0008]

[0009] in, The voltage amplitude of the high-frequency signal is adaptive, and the voltage amplitude of the high-frequency injection signal is dynamically adjusted according to the real-time operating conditions of the screw press. For high-frequency injection adaptive frequency, the frequency of the high-frequency injection signal is dynamically adjusted based on the motor current change rate and the structural parameters of the screw press. The frequency is the normalized value of the q-axis current change rate, reflecting the dynamic characteristics of the load. For adaptive weights; This refers to the running time of the screw press.

[0010] Furthermore, the specific construction method of the structure-adaptive high-frequency injection method is as follows:

[0011] Obtain the structural parameters of the screw press, including the inner diameter of the rings, the diameter of the screw shaft, and the total number of rings. The rings include fixed rings and moving rings. The formula for designing the ring gap is as follows:

[0012]

[0013] The pitch of the helical shaft. To fix the inner diameter of the ring, Moving ring inner diameter, The diameter of the helical shaft, This is a cyclic correction factor. The total number of ring plates, The helix angle of the helix axis;

[0014] By incorporating the structural parameters of the screw press into a high-frequency signal modulation strategy, a frequency adaptive strategy model is constructed as follows:

[0015]

[0016] in, To inject adaptive frequency at high frequencies, For high-frequency injection frequency, This is the frequency adjustment coefficient. This is the rated current of the permanent magnet synchronous motor. The length of the condensation section. The length of the dehydration section. For the q-axis current under the Clark and Park transformations, Indicates load changes;

[0017] The amplitude of the high-frequency injected signal is adjusted according to the deviation between the current torque and the normal torque, and the change in the helix angle. The adaptive model for the high-frequency signal amplitude is constructed as follows:

[0018] =

[0019] in, For adaptive voltage amplitude of high-frequency signals, This represents the fundamental voltage amplitude of the high-frequency signal. Amplitude adjustment coefficient, This is the current actual torque. This refers to the torque under normal operating conditions. This is the rated torque. To design the helix angle;

[0020] To improve the performance of the high-frequency injection method, the third harmonic weight varies with the gap; the larger the gap, the larger the weight. Simultaneously, it gradually increases over time until it stabilizes to avoid initial impact. Therefore, a high-frequency adaptive weighting model is constructed:

[0021]

[0022] in, For adaptive weights, The inertial time established for harmonics, For design gaps, This refers to the running time of the screw press.

[0023] The final representation of the structure-adaptive high-frequency injection method is as follows:

[0024]

[0025] in, For adaptive voltage amplitude of high-frequency signals; Inject adaptive frequency for high frequency; For adaptive weights.

[0026] Furthermore, the d-axis current and q-axis current are calculated using the Clark and Park transformations, as follows:

[0027] The three-phase current of the permanent magnet synchronous motor is measured by a current sensor. , , Calculate the d-axis current and q-axis current using the following formulas:

[0028]

[0029] in, For the d-axis current under Clark and Park transformations, For the q-axis current under the Clark and Park transformations, It is an electrical angle.

[0030] Furthermore, by combining the permanent magnet synchronous motor speed predicted by the sliding mode observer using the high-frequency injection method, and combining the electromagnetic torque formula with the structural parameters of the screw press, the structural electromagnetic torque is constructed as follows:

[0031] Based on the calculation of d-axis and q-axis currents, the current error formula is defined as follows:

[0032] ,

[0033] in, , To estimate the current, It is the d-axis electromotive force component. It is the q-axis electromotive force component;

[0034] The dynamic equations of the sliding mode observer are further obtained as follows:

[0035]

[0036] Further estimates of the back electromotive force are as follows:

[0037] ,

[0038] in, and It is the dq-axis voltage, obtained from the inverter output voltage via a Clarke transform. resistance, It is a stator inductor. It is the synovial gain. and The back electromotive force is the estimated value, and sign is the sign function.

[0039] Rotor position and speed estimation:

[0040] ,

[0041] in, For rotor position estimation, For speed estimation;

[0042] The structure-adaptive high-frequency injection voltage signal obtained based on the structure-adaptive high-frequency injection method is injected into the voltage of the permanent magnet synchronous motor. The high-frequency current response is bandpass filtered and demodulated to obtain the position error signal. The injected signal is mixed with the measured current, and after passing through a low-pass filter (LPF), the position error signal is extracted.

[0043]

[0044] in, It is a high-frequency current response component. Proportional to the rotor position deviation, used to correct the position output of the sliding mode observer. For the screw press running time, Inject adaptive frequency for high frequency;

[0045] The corrected rotor position was further obtained:

[0046]

[0047] in, Correct gain;

[0048] Electric angular velocity is calculated using differentiation:

[0049]

[0050] Calculate the flux linkage of the permanent magnet:

[0051]

[0052] Calculate electromagnetic torque:

[0053] +

[0054]

[0055] in, For electromagnetic torque, This represents the number of pole pairs in a permanent magnet synchronous motor. For structural coefficients, This refers to the amount of sludge processed per unit time. The viscosity coefficient of the sludge. The length of the concentration section of the screw press. The length of the dewatering section of the screw press. The gap between the ring plates of the screw press. For design gaps, This refers to the helix angle of the screw shaft of the screw press.

[0056] Furthermore, before constructing a sludge accumulation detection model based on the electromagnetic torque calculated from multiple observations using a sliding mode observer, and subsequently a dynamic threshold model for sludge accumulation, it is necessary to build an adaptive weighting factor to accommodate various types of sludge.

[0057]

[0058]

[0059] in, This is the initial attenuation amplitude coefficient. The decay rate coefficient, The sensitivity coefficient for processing volume is determined when the processing volume increases. The lower limit constant of decay, Basic offset constant, and Let be the adaptive factor, where It is a time-structure adaptive factor. It is the processing volume-structure benchmark factor.

[0060] Furthermore, a sludge accumulation detection model is constructed based on the electromagnetic torque calculated from multiple observations using a sliding mode observer, thereby establishing a dynamic threshold model for sludge accumulation, as detailed below:

[0061] Several sets of observations obtained by combining multiple observations from the sliding mode observer By using regression analysis, the inherent basic torque value under the basic operating conditions, which is unaffected by operating parameters, is extracted, thus obtaining the torque value under the basic operating conditions. Therefore, the sludge accumulation detection model is constructed as follows:

[0062]

[0063] in It is the torque value under basic operating conditions. The torque value under basic operating conditions refers to the torque value of the machine under conditions without sludge accumulation and with the processing capacity Q per unit time as the baseline value. This refers to the torque under normal operating conditions.

[0064] Based on calculations , combined and The dynamic threshold calculation model for sludge accumulation is constructed as follows:

[0065]

[0066] in, The appropriate warning torque for sludge accumulation. This represents a high and dangerous torque due to sludge accumulation.

[0067] Furthermore, it also includes integrating the code implementing the method into the chip of the screw press control cabinet, feeding back the predicted torque under normal operating conditions and the calculated dynamic threshold to the chip of the control cabinet, and then controlling the nozzles to perform cleaning through the chip of the control cabinet. Whether the nozzles are turned on or off is based on the following judgment: when No cleaning required, when Then perform light cleaning, when Then perform intensive cleaning and maintenance.

[0068] The present invention also provides a sludge accumulation detection system for screw presses based on sensorless torque estimation, including a memory, a processor, and computer program instructions stored in the memory and executable by the processor. When the processor executes the computer program instructions, it can implement the steps of the method described above.

[0069] Compared with the prior art, the present invention has the following beneficial effects:

[0070] (1) This invention adds structural parameters of the screw press by high frequency injection method and constructs a high frequency injection method with structural self-adaptation. It can not only accurately analyze the sludge inside the screw press, but also has a lower cost than traditional torque sensors and is faster to implement. At the same time, it improves the intelligence level of the screw press.

[0071] (2) This invention establishes a sludge accumulation detection calculation model and a standard for dynamically judging sludge deposition, which realizes the judgment of sludge accumulation inside the screw press. It adapts to changes in sludge composition through adaptive factors, increases the applicability of the machine to sludge treatment, and improves accuracy.

[0072] (3) The integrated nozzle self-control system of the present invention realizes the self-cleaning of the screw press and improves the service life of the machine. Attached Figure Description

[0073] Figure 1 This is a flowchart of the present invention;

[0074] Figure 2 This is a structural diagram of the screw press of the present invention; in the diagram, 1-control cabinet, 2-flocculation dosing tank, 3-working area, 4-permanent magnet synchronous motor;

[0075] Figure 3 This is a cross-sectional structural diagram of the screw press of the present invention;

[0076] Figure 4 This is a structural diagram of the spray pipe for the screw press of the present invention; in the diagram, 5-spray pipe, 6-spray head;

[0077] Figure 5 This is a cross-sectional view of the screw press of the present invention; in the figure, 7 - screw shaft;

[0078] Figure 6 This is a partial enlarged view of the screw press of the present invention; in the figure, 8-moving ring, 9-fixed ring. Detailed Implementation

[0079] The technical solution of the present invention will now be described in detail with reference to the accompanying drawings.

[0080] This invention provides a method for detecting sludge accumulation in a screw press based on sensorless torque estimation. The method calculates the d-axis and q-axis currents using the Clark and Park transform, predicts the speed of the permanent magnet synchronous motor using a sliding mode observer with high-frequency injection, constructs the structural electromagnetic torque by combining the electromagnetic torque formula with the structural parameters of the screw press, and builds a sludge accumulation detection model based on the electromagnetic torque calculated by multiple observations of the sliding mode observer. Finally, a dynamic threshold model for sludge accumulation is constructed to determine the sludge deposition status.

[0081] The following is a detailed implementation process of the present invention.

[0082] like Figure 1 As shown, this embodiment provides a sensorless torque estimation method for detecting sludge buildup in a screw press, including the following steps:

[0083] (1) The screw shaft 7 propels the sludge forward. The gap between the rings determines the drainage effect. The inner diameter of the rings, the diameter of the screw shaft, and the total number of rings (fixed rings 9 and moving rings 8) are obtained in the screw press. The formula for designing the gap between the rings is as follows:

[0084]

[0085] The pitch of the helical shaft is in mm. The inner diameter of the fixed ring is in mm. Inner diameter of the moving ring, in mm. The diameter of the helical shaft is in mm. This is a cyclic correction factor, with a value range of 0.95-1.05. This represents the total number of rings (fixed rings and moving rings). The helix angle on the helical axis is expressed in degrees (°).

[0086] (2) The three-phase current i of the initial patch-type permanent magnet synchronous motor 4 is measured by a current sensor. a i b i c .

[0087] (3) Structural parameters such as helix angle and annular gap are incorporated into the high-frequency signal modulation strategy to make the high-frequency injection method more adaptable to the working characteristics of the screw press. The frequency adaptive strategy model is constructed as follows:

[0088]

[0089] in, The high-frequency injection adaptive frequency is dynamically adjusted based on the motor current change rate and the screw press structural parameters. The frequency is the normalized value of the q-axis current change rate, reflecting the dynamic characteristics of the load. This is the high-frequency injection frequency, ranging from 500 to 800 Hz. This is the frequency adjustment coefficient, with a value ranging from 0.1 to 0.5. This is the rated current of the motor, in amperes (A). This refers to the length of the concentration section, in mm. This refers to the length of the dehydration section, in mm. Figure 2 The working area 3 of the screw press is divided into a concentration section and a dewatering section. The flocculant dosing tank 2 is used to add flocculant, so that the wastewater to be treated mixes with the flocculant to form flocs, which then enter the working area. The control cabinet 1 is used to control the operation of the entire screw press and is equipped with a chip for controlling the operation of the screw press.

[0090] (4) The amplitude of the high-frequency injected signal is adjusted according to the deviation between the current torque and the normal torque, and the change in the helix angle. When the torque deviation is large, the injection amplitude is increased to improve the signal-to-noise ratio; when the helix angle changes, it is adjusted by the tangent function to reflect the influence of structural changes on the load. The adaptive model of the high-frequency signal amplitude is constructed as follows:

[0091] =

[0092] in, This refers to the adaptive voltage amplitude of the high-frequency signal (which dynamically adjusts the voltage amplitude of the high-frequency injection signal based on the real-time operating conditions of the screw press). This is the base voltage amplitude of the high-frequency signal, ranging from 30 to 80, in units of V. The amplitude adjustment coefficient ranges from 0.2 to 0.8. The actual torque is in N. . Torque under normal operating conditions, unit: N . Rated torque, unit . The design helix angle is expressed in degrees (°).

[0093] (5) Due to the limitations of the traditional high-frequency injection method, single-frequency injection causes periodic disturbances, reduces accuracy in a specific speed range, and has a significant impact from changes in motor parameters. To improve the performance of the high-frequency injection method, a third harmonic adaptive weight is designed, which means that the weight of the third harmonic changes with the gap; the larger the gap, the larger the weight. Simultaneously, it gradually increases over time until it stabilizes to avoid initial impact. Therefore, a high-frequency signal frequency adaptive weight model is constructed:

[0094]

[0095] in, The adaptive weights for the third harmonic. The inertial time established for harmonics, in seconds. Design gap, unit mm. The running time of the screw press is in seconds.

[0096] (6) The amplitude and frequency of the injected high-frequency signal are dynamically adjusted according to the load torque and speed of the screw press to improve the position estimation accuracy at low speeds and during sudden load changes. Combining steps (3), (4) and (5), the structure adaptive high-frequency injection method is obtained as follows:

[0097]

[0098] (7) Sliding mode observers (SMOs) are typically used to estimate the back electromotive force of a motor, thereby estimating the speed and rotor position. Combining this with the high-frequency injection method aims to improve the estimation accuracy at low speeds; therefore, the method for calculating the q-axis current is as follows:

[0099]

[0100] in, The current along the d-axis under the Clark and Park transformations, in amperes (A). The current is the q-axis current under the Clark and Park transformations, in amperes (A). It is an electrical angle.

[0101] (8) The current error formula is defined by (7) as follows:

[0102] ,

[0103] in, , To estimate the current, It is the d-axis electromotive force component. It is the q-axis electromotive force component;

[0104] (9) The dynamic equations of the sliding mode observer obtained from (8) are as follows:

[0105]

[0106] in: and It is the dq-axis voltage, obtained from the inverter output voltage via a Clarke transform. resistance, It is a stator inductor. This is the slug gain, and sign is the sign function. and This is the estimated back electromotive force.

[0107] ,

[0108] (10) The rotor position and speed estimation formulas are obtained from the back electromotive force obtained in (9):

[0109] ,

[0110] (11) The structure-adaptive high-frequency injection voltage signal is obtained from step (6) and injected into the motor voltage (e.g., into the d-axis voltage). The high-frequency current response is bandpass filtered and demodulated to obtain the position error signal. The injected signal is mixed with the measured current and then low-pass filtered (LPF) to extract the position error:

[0111]

[0112] in, It is a high-frequency current response component. It is proportional to the rotor position deviation and is used to correct the position output of the sliding mode observer.

[0113] (12) Combining (10) and (11), the corrected rotor position is obtained:

[0114]

[0115] in, The gain is adjusted, typically by a value of 0.1-0.5.

[0116] Electric angular velocity is calculated using differentiation:

[0117]

[0118] (13) Using (9) and (12), calculate the permanent magnet:

[0119]

[0120] (14) The electromagnetic torque is calculated using the back electromotive force from (13) as follows:

[0121] +

[0122]

[0123] in, Electromagnetic torque, unit , This represents the number of pole pairs in a permanent magnet synchronous motor. The flux linkage of the permanent magnets in the system is measured in W. b , This represents the q-axis current, measured in amperes (A). This is the structural coefficient. The sludge treatment capacity is expressed in kg / h. This represents the sludge viscosity coefficient.

[0124] (15) Combining (14) to obtain several groups Because different types of sludge are being treated, adaptive weighting factors are constructed to accommodate the accumulation of various types of sludge, as follows:

[0125]

[0126]

[0127] Where Q represents the sludge treatment rate per unit time, in kg / h. This is the initial attenuation amplitude coefficient. The decay rate coefficient ( and When the machine is first started, the ring gap and lubrication status are in an unstable state, requiring a higher torque threshold to avoid false alarms; as the running time increases, the system tends to stabilize, and the threshold gradually decreases. (Unit:) , The throughput sensitivity coefficient (as throughput increases, the base torque increases accordingly, but the growth trend gradually flattens out (logarithmic characteristic), reflecting the scale effect in sludge treatment: doubling the throughput does not require doubling the torque threshold), is expressed in m³ / h. The lower limit constant of decay, The basic offset constant (representing equipment no-load operation and mechanical losses) is in units of t represents the continuous running time, in hours (h).

[0128] (16) Combined with (14) to obtain several groups By using regression analysis, the inherent basic torque value under the basic operating conditions, which is unaffected by operating parameters, is extracted, thus obtaining the torque value under the basic operating conditions. Therefore, the sludge accumulation detection model is constructed as follows:

[0129]

[0130] in, This refers to the torque value under basic operating conditions. The torque value under basic operating conditions means the torque value of the machine under conditions of no sludge accumulation and with the throughput Q per unit time as the baseline. , The torque value is under normal operating conditions, in units of... .

[0131] (17) Combining the normal torque from step (16) with (15) to obtain the dynamic function and The dynamic threshold calculation model is constructed as follows:

[0132]

[0133] in, For moderate warning torque of sludge accumulation, unit , For the high dangerous torque caused by sludge accumulation, unit .

[0134] (18) The code implementing the method is integrated into the chip of the control cabinet of the screw press. The predicted torque under normal operating conditions and the calculated dynamic threshold are fed back to the chip of the control cabinet. Then, the chip of the control cabinet causes the liquid in the spray pipe 5 to clean the screw press through the nozzle 6. Whether the nozzle is turned on or off is determined based on the following: when No cleaning required, when Then perform light cleaning, when Then perform intensive cleaning and maintenance.

[0135] The present invention also provides a sludge accumulation detection system for screw presses based on sensorless torque estimation, including a memory, a processor, and computer program instructions stored in the memory and executable by the processor. When the processor executes the computer program instructions, it can implement the steps of the method described above.

[0136] The above are preferred embodiments of the present invention. Any changes made to the technical solution of the present invention that do not exceed the scope of the technical solution of the present invention shall fall within the protection scope of the present invention.

Claims

1. A sensorless torque estimation based sludge build-up detection method for a piling machine, characterized in that, The d-axis current and q-axis current are calculated by Clark and Park transformation, the permanent magnet synchronous motor speed is predicted by combining the high-frequency injection method with the sliding mode observer, the structural electromagnetic torque is constructed by combining the electromagnetic torque formula with the structure parameters of the screw machine, the sludge accumulation detection model is constructed based on the electromagnetic torque calculated by multiple observations of the sliding mode observer, and then the dynamic threshold model of sludge accumulation is constructed to judge the sludge deposition.

2. A sensorless torque estimation based sludge build-up detection method for a screw press according to claim 1, wherein, The high-frequency injection method is a structural adaptive high-frequency injection method constructed based on the related parameters of the screw machine.

3. A sensorless torque estimation based sludge build-up detection method for a screw press according to claim 2, wherein, The structural adaptive high-frequency injection method is expressed as follows: wherein, is the adaptive voltage amplitude of the high-frequency signal, which dynamically adjusts the voltage amplitude of the high-frequency injection signal according to the real-time working condition of the screw stacking machine; is the adaptive frequency of the high-frequency injection, which dynamically adjusts the frequency of the high-frequency injection signal based on the motor current rate of change and the structural parameters of the screw stacking machine, the frequency being the normalized value of the q-axis current rate of change, reflecting the dynamic characteristics of the load; is the adaptive weight; is the running time of the screw stacking machine.

4. A sensorless torque estimation based sludge build-up detection method for a screw press according to claim 2 or 3, characterized in that, The structural adaptive high-frequency injection method is specifically constructed as follows: The structure parameters of the screw machine are obtained, including the inner diameter of the ring piece, the diameter of the spiral shaft, and the total number of ring pieces, and the ring piece includes a fixed ring and a movable ring. is the helical axis pitch, is the fixed ring inner diameter, is the moving ring inner diameter, is the helical axis diameter, is the ring type correction coefficient, is the total number of ring segments, is the helix angle of the helical axis; The structure parameters of the screw machine are incorporated into the high-frequency signal modulation strategy, and the frequency adaptive strategy model is constructed as follows: wherein, is a high frequency injection adaptive frequency, is a high frequency injection frequency, is a frequency regulation coefficient, is a permanent magnet synchronous motor rated current, is a concentration section length, is a dewatering section length, is a q-axis current under Clarke and Park transformation, denotes a load change; The amplitude of the high-frequency injection signal is adjusted according to the deviation of the current torque from the normal torque and the change of the spiral angle, and the high-frequency signal amplitude adaptive model is constructed as follows: = wherein, is an adaptive voltage amplitude of the high frequency signal, is a basic voltage amplitude of the high frequency signal, is an amplitude adjustment coefficient, is a current actual torque, is a normal operating condition torque, is a rated torque, is a design helix angle; To improve the performance of the high-frequency injection method, the third harmonic weight changes with the change of the gap, the larger the gap, the larger the weight; at the same time, it gradually increases with time to avoid initial impact, so the high-frequency signal frequency adaptive weight model is constructed as follows: wherein, is an adaptive weight, is an inertia time established for harmonics, is a design gap, is a run time of the supercoiling machine; The structural adaptive high-frequency injection method is finally expressed as follows: wherein, is an adaptive voltage amplitude for the high frequency signal; is an adaptive frequency for the high frequency injection; is an adaptive weight.

5. A sensorless torque estimation based sludge build-up detection method for a screw press according to claim 2, wherein, The d-axis current and q-axis current are calculated by Clark and Park transformation, and the specific process is as follows: Three-phase currents of the permanent magnet synchronous motor are measured by current sensors , , , the d-axis current and the q-axis current are calculated, and the calculation formula is as follows: wherein, is the d-axis current under the Clarke and Park transformation, is the q-axis current under the Clarke and Park transformation, is the electrical angle.

6. A sensorless torque estimation based sludge build-up detection method for a screw press according to claim 5, wherein, The permanent magnet synchronous motor speed is predicted by combining the high-frequency injection method with the sliding mode observer, and the structural electromagnetic torque is constructed by combining the electromagnetic torque formula with the structure parameters of the screw machine, and the specific process is as follows: Based on the calculation of the d-axis current and q-axis current, the current error formula is defined as follows: , wherein , is the estimated current, is the d-axis electromotive force component, is the q-axis electromotive force component; The dynamic equation of the sliding mode observer is further obtained as follows: The back electromotive force is further estimated as follows: ， wherein, with is the d-q axis voltage, which is obtained by Clarke transformation of the inverter output voltage, resistances, is the stator inductance, is the flux linkage gain, and is the estimated back EMF, and sign is the sign function. Rotor position and speed estimation: ， wherein is a rotor position estimate, is a rotational speed estimate; The structural adaptive high-frequency injection voltage signal obtained based on the structural adaptive high-frequency injection method is injected into the permanent magnet synchronous motor voltage, the high-frequency current response is filtered and demodulated by a band-pass filter to obtain a position error signal, the injection signal is mixed with the measured current, and after low-pass filtering LPF, the position error signal is extracted: wherein, is a high frequency current response component, is proportional to the rotor position error for correcting the position output of the sliding mode observer, is the run time of the screw stacking machine, is the high frequency injection adaptive frequency; The corrected rotor position is further obtained as follows: wherein correction gain; The electrical angular velocity is calculated by differentiation: The flux of the permanent magnet is calculated: The electromagnetic torque is calculated: + wherein, is the electromagnetic torque, is the number of pole pairs of the permanent magnet synchronous motor, is the structural coefficient, is the sludge treatment capacity per unit time, is the sludge viscosity coefficient, is the length of the thickening section of the decanter, is the length of the dewatering section of the decanter, is the ring piece gap of the decanter, is the design gap, is the helix angle of the helical shaft of the decanter.

7. A sensorless torque estimation based sludge build-up detection method for a screw press according to claim 6, characterized in that, Before constructing the sludge accumulation detection model based on the electromagnetic torque calculated by multiple observations of the sliding mode observer, and then constructing the dynamic threshold model of sludge accumulation, an adaptive weight factor needs to be constructed to adapt to various types of sludge: wherein is an initial decay amplitude coefficient, is a decay rate coefficient, is a processing load sensitive coefficient, which is increased with increasing processing load, is a decay lower limit constant, is a base offset constant, and is an adaptation factor, wherein is a time-structure adaptation factor, is a processing load-structure reference factor.

8. A sensorless torque estimation based sludge build-up detection method for a screw press according to claim 7, characterized in that, The sludge accumulation detection model is constructed based on the electromagnetic torque calculated by multiple observations of the sliding mode observer, and then the dynamic threshold model of sludge accumulation is constructed, and the specific process is as follows: A plurality of groups of observations obtained in combination with a sliding mode observer Through regression analysis, the torque basic value in the basic working condition which is inherent and not affected by the operating parameters is stripped out to obtain the torque value in the basic working condition And a sludge accumulation detection model is constructed as follows: wherein is the torque value under the basic working condition, the torque value under the basic working condition refers to the torque value of the machine under the condition of no sludge accumulation and the processing capacity Q per unit time being a reference value; is the torque under the normal working condition; Based on the calculated , in combination With , the dynamic threshold calculation model of sludge accumulation is constructed as follows: wherein, is a warning torque for a medium sludge build-up, is a danger torque for a high sludge build-up.

9. A sensorless torque estimation based sludge build-up detection method for a screw press according to claim 8, characterized in that, Also included is that the code realizing the method is integrated into the chip of the control cabinet of the stacking machine, the predicted normal working condition torque size and the calculated dynamic threshold value are fed back to the chip of the control cabinet, and then the cleaning of the nozzle is controlled by the chip of the control cabinet. Whether the nozzle is opened or not is based on the following judgment: No cleaning is needed when Mild cleaning is performed when Strong cleaning and maintenance are performed when 10. A sensorless torque estimation based sludge build-up detection system for a screw press, characterized in that, The computer program instructions stored on the memory and capable of being executed by the processor, when the processor executes the computer program instructions, can realize the steps of the method of any one of claims 1-9.

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