Synchronous fault-tolerant control method for rotating speed of double-servo motor system

Abstract

The invention discloses a dual-servo motor system rotating speed synchronization fault-tolerant control method, which belongs to the technical field of motor control, and comprises the following steps: collecting state information of dual servo motors and constructing a multi-dimensional state vector; performing fusion processing on the multi-dimensional state vectors through a signal fusion processor to obtain a motor health degree evaluation index; analyzing the health degree evaluation index of the motor, selecting different control modes according to an analysis result, and controlling the double-servo motor by adopting a corresponding control algorithm according to the selected control modes; in the control execution process, fault detection is carried out on the motor state, and when a fault symptom is detected, a fault-tolerant control strategy is started. The method has the beneficial effects that the operation state of the dual-servo motor can be comprehensively monitored by constructing the multi-dimensional state vector and adopting a signal fusion processing technology, the motor health degree evaluation index is established, and quantitative evaluation and intelligent analysis of the system state are realized.

Description

Technical Field

[0001] The present invention relates to the technical field of motor control, and in particular to a speed synchronization fault-tolerant control method for a dual-servo motor system. Background Art

[0002] Dual servo motor systems play a vital role in modern industrial automation, widely used in applications requiring high synchronization accuracy, such as CNC machine tools, printing equipment, textile machinery, and packaging production lines. In these applications, two or more servo motors must maintain a high degree of synchronization to ensure machining accuracy, product quality, and production efficiency. As the manufacturing industry evolves towards higher precision and higher efficiency, the demands on the synchronization control accuracy, response speed, and system reliability of dual servo motor systems are becoming increasingly stringent.

[0003] However, the existing dual-servo motor synchronization control technology still has many shortcomings in practical applications. Although the traditional master-slave control and cross-coupling control methods can achieve good synchronization effects under normal working conditions, when one of the motors fails, it often causes the entire system to shut down, seriously affecting production continuity and economic benefits. In addition, the existing technology lacks an effective fault prediction mechanism and cannot provide early warning and intervention before a fault occurs. The fault detection method is relatively simple and mainly relies on simple threshold judgment, which makes it difficult to accurately identify the fault type and assess the severity of the fault. At the same time, the control strategy is relatively rigid and cannot dynamically adjust the control parameters and control mode according to the real-time status of the system and the fault situation, which limits the system's adaptability and fault tolerance under complex working conditions. Summary of the Invention

[0004] In view of the above-mentioned problems, the present invention is proposed.

[0005] Therefore, the technical problem solved by the present invention is that when one of the motors fails, the entire system will be shut down, and the fault detection means are relatively simple.

[0006] To solve the above technical problems, the present invention provides the following technical solution: a method for synchronous fault-tolerant control of the speed of a dual servo motor system, comprising the following steps:

[0007] Collect the state information of the dual servo motors and construct a multi-dimensional state vector;

[0008] Performing fusion processing on the multi-dimensional state vector by a signal fusion processor to obtain a motor health assessment index;

[0009] By analyzing the motor health evaluation index, different control modes are selected according to the analysis results, and corresponding control algorithms are used to control the dual servo motors according to the selected control modes;

[0010] During the control execution process, the motor status is detected for faults, and the fault-tolerant control strategy is activated when fault signs are detected.

[0011] As a preferred solution of the speed synchronization fault-tolerant control method of a dual servo motor system described in the present invention, wherein: the state information includes speed, torque, current, temperature and vibration signals;

[0012] Wherein, the multidimensional state vector is expressed as:

[0013] X=[ω1,ω2,τ1,τ2,i1,i2,Temp1,Temp2,V ib1 ,V ib2 ] T ;

[0014] Where X is the multidimensional state vector, ω1, ω2 are the speeds of the first motor and the second motor, τ1, τ2 are the torques of the first motor and the second motor, i1, i2 are the currents of the first motor and the second motor, and T emp1 ,T emp2 is the temperature of the first motor and the second motor, V ib1 ,V ib2 are the vibration signals of the first motor and the second motor.

[0015] As a preferred solution of the dual servo motor system speed synchronization fault-tolerant control method described in the present invention, the step of calculating the motor health evaluation index includes:

[0016] A Kalman filter is used to filter the multidimensional state vector, and an optimal estimation is performed based on the collected state information to obtain a filtered state estimation vector.

[0017] The speed deviation, torque deviation and current deviation between the dual servo motors, as well as the temperature deviation and vibration deviation of the dual servo motors relative to the preset reference value are calculated respectively through the filtered state estimation vector;

[0018] Normalize all deviation values, multiply each normalized deviation value by the corresponding weighting coefficient, and then perform weighted summation to obtain the motor health assessment index;

[0019] The calculation formula of the motor health evaluation index H is expressed as:

[0020]

[0021] Where α1, α2, α3, α4, and α5 are weighted coefficients of speed deviation, torque deviation, current deviation, temperature deviation, and vibration deviation, respectively; Δω, Δτ, Δi, and ΔT are weighted coefficients of speed deviation, torque deviation, current deviation, temperature deviation, and vibration deviation, respectively; emp , ΔV ibThey are respectively the rotational speed deviation value, torque deviation value, current deviation value, temperature deviation value relative to the reference value, and vibration deviation value relative to the reference value between the two servo motors; ω nom , τ nom , i nom , T emp,max , V ib,max They are respectively the rated rotational speed, rated torque, rated current, maximum allowable temperature, and maximum allowable vibration value;

[0022] Among them, the constraint conditions are:

[0023] <00,00126>

[0024] In the formula, j is the summation index variable.

[0025] The beneficial effect of this preferred technical solution is that through the Kalman filter and weighted fusion calculation, the multi-dimensional state information is converted into a single health index, realizing the quantitative evaluation of the system state, which is convenient for subsequent intelligent decision-making and control mode selection.

[0026] As a preferred scheme of a rotational speed synchronization fault-tolerant control method for a dual servo motor system described in the present invention, wherein: the control modes include a precision synchronization mode, a fault-tolerant operation mode, and an emergency protection mode. When selecting different control modes, the selection rules are:

[0027] When H ≤ 0.3 and the rotational speed difference between the two servo motors is less than 0.5% of the reference rotational speed, select the precision synchronization mode;

[0028] When H ≤ 0.3 and the rotational speed difference between the two servo motors is greater than or equal to 0.5% of the reference rotational speed, select the fault-tolerant operation mode;

[0029] When 0.3 < H ≤ 0.8, select the fault-tolerant operation mode; <000013,9>

[0030] When H > 0.8, select the emergency protection mode.

[0031] The beneficial effect of this preferred technical solution is that the most suitable control mode is automatically selected according to the motor health evaluation index and the rotational speed difference, avoiding the single control strategy of the traditional method, and enabling the system to adopt the optimal control scheme according to the actual situation.

[0032] As a preferred scheme of a rotational speed synchronization fault-tolerant control method for a dual servo motor system described in the present invention, wherein: the precision synchronization mode adopts a cross-coupling control algorithm, and the specific steps include:

[0033] Respectively obtain the deviation between the actual position signal of the first motor and the second motor and their respective position commands, and obtain the position error of the first motor and the position error of the second motor;

[0034] Subtracting the second motor position error from the first motor position error to obtain a coupling error signal;

[0035] Performing a proportional-integral operation on the coupling error signal, wherein the proportional component is obtained by multiplying the coupling error by a proportional gain coefficient, and the integral component is obtained by integrating the coupling error and then multiplying it by the integral gain coefficient, and the two components are added to obtain a coupling control amount;

[0036] The coupling control amount is added to the output of the independent position controller of the first motor in a positive form, and is added to the output of the independent position controller of the second motor in a negative form to form their respective final control instructions.

[0037] The beneficial effects of this preferred technical solution are: by adopting a cross-coupling control algorithm and compensating for the position errors, the synchronization error between the dual motors can be effectively suppressed, and high-precision synchronization control can be achieved under normal working conditions.

[0038] As a preferred solution of the dual servo motor system speed synchronization fault-tolerant control method described in the present invention, wherein: the fault-tolerant operation mode adopts a single-machine enhanced control algorithm, and the specific steps include:

[0039] According to the comparison of the state information of the first motor and the second motor, the motor in good health is selected as the enhanced control object, and the motor in poor health is maintained under basic control;

[0040] Adjusting parameters of the controller of the enhanced control object, increasing the proportional gain coefficients of its position controller and speed controller by 20-50%, reducing the time constant of the control system by 30-80%, and adjusting the integral gain coefficient and the differential gain coefficient to maintain system stability;

[0041] Calculate the compensation amount based on the degree of performance loss of the motor in poor health;

[0042] The adjusted controller output is superimposed on the compensation amount to generate an enhanced control instruction for the enhanced control object.

[0043] The beneficial effects of this preferred technical solution are: by performing parameter enhancement and compensation control on healthy motors, they can be enabled to undertake more work tasks, compensate for the performance loss of faulty motors, and ensure the system's ability to continue operating in a faulty state.

[0044] As a preferred solution of the dual servo motor system speed synchronization fault-tolerant control method described in the present invention, the emergency protection mode adopts a safety shutdown algorithm, and the specific steps include:

[0045] Set the downtime of the dual servo motors from current speed to zero speed to 3-10 seconds;

[0046] During the first 40% of the downtime, a maximum allowable deceleration is applied to the dual servo motors to perform linear deceleration control, reducing the speed of the dual servo motors from the current speed value to 30% of the rated speed;

[0047] During the middle 30% of the downtime, a quadratic curve deceleration control law is applied to the dual servo motors, and the deceleration value changes in a decreasing manner according to a quadratic function relationship, reducing the speed of the dual servo motors from 30% of the rated speed to 5% of the rated speed;

[0048] During the last 30% of the downtime, an exponential decay deceleration control law is applied to the dual servo motors to reduce the speed of the dual servo motors from 5% of the rated speed to zero speed at a deceleration value that is less than 10% of the maximum allowable deceleration;

[0049] When the speed of the dual servo motors drops to zero, the motor power supply is disconnected, the mechanical brake device is activated, the system status flag is set to a safety lock state, and the sound and light alarm device is activated to send out a fault warning signal.

[0050] The beneficial effects of this preferred technical solution are: adopting multi-stage deceleration control and complete safety protection measures to ensure that the system can shut down safely and smoothly in the event of a serious fault, avoiding equipment damage and safety accidents.

[0051] As a preferred solution of the dual servo motor system speed synchronization fault-tolerant control method described in the present invention, the step of performing fault detection on the motor state includes:

[0052] Analyze the state information of the dual servo motors to obtain the frequency characteristic parameters and energy distribution characteristic parameters of the signals;

[0053] A reference database containing normal operating modes and abnormal operating modes is established, and the extracted frequency characteristic parameters and energy distribution characteristic parameters are compared and analyzed with the standard modes in the reference database. The fault characteristics are identified based on the matching results.

[0054] The beneficial effects of this preferred technical solution are: through frequency characteristics and energy distribution analysis combined with database matching, different types of faults can be accurately identified, thereby improving the accuracy and reliability of fault detection.

[0055] As a preferred solution of the dual servo motor system speed synchronization fault-tolerant control method described in the present invention, the steps of the fault-tolerant control strategy include:

[0056] determining a faulty motor and a healthy motor among the first motor and the second motor according to the fault detection result;

[0057] Calculate the load that needs to be transferred based on the remaining operating capacity of the faulty motor, and gradually transfer the load of the faulty motor to the healthy motor;

[0058] A virtual reference axis is established as a unified position and speed reference, so that the healthy motor can track the virtual reference axis. At the same time, the compensation amount is calculated according to the operating deviation of the faulty motor and added to the control instruction of the healthy motor to compensate for the speed deviation and position deviation of the faulty motor.

[0059] The beneficial effects of this preferred technical solution are: through the combination of load redistribution and virtual axis compensation, a fault-tolerant control solution is implemented, which can maintain the basic functions and performance of the system when a fault occurs.

[0060] As a preferred solution of the method for synchronous fault-tolerant control of the speed of a dual servo motor system described in the present invention, when the faulty motor resumes normal operation, the method further includes the following steps:

[0061] Detect the operating status of the faulty motor and determine that it has returned to normal when its health assessment index returns to the preset range and the operation is stable;

[0062] Adjust the speed of the faulty motor and set the speed difference of the dual servo motors to within 2% of the reference speed;

[0063] Adjust the position of the faulty motor based on speed synchronization so that the position deviation with the healthy motor is controlled within 5 degrees;

[0064] In the reverse order of load transfer, transfer the load transferred to the healthy motor back to the faulty motor, with the transfer speed controlled at 5-10% per second;

[0065] When the load redistribution is completed, the dual servo motor synchronous control is restarted.

[0066] The beneficial effect of this preferred technical solution is that it can ensure that the faulty motor can smoothly rejoin the synchronous control after recovery, avoiding system shock and instability during the recovery process.

[0067] Beneficial effects of the present invention:

[0068] By constructing a multi-dimensional state vector and adopting signal fusion processing technology, it is possible to comprehensively monitor the operating status of the dual servo motors, establish a motor health assessment index, and achieve quantitative evaluation and intelligent analysis of the system status. By using multi-angle signal analysis technology to extract frequency characteristic parameters and energy distribution characteristic parameters, and combining them with a reference database for pattern matching, it is possible to accurately identify different types of faults, improve the accuracy and reliability of fault detection, and achieve early detection and warning of faults.

[0069] Based on the motor health assessment index and system operating status, the system automatically selects precise synchronization mode, fault-tolerant operation mode, or emergency protection mode, avoiding the single-minded nature of traditional control methods and enabling the system to adopt the optimal control strategy based on actual conditions. When a fault is detected, the fault-tolerant control strategy enables healthy motors to take on more work tasks, compensating for the performance loss of the faulty motor, avoiding overall system downtime caused by single-machine failures, and improving system availability and production continuity. When the faulty motor returns to normal, the progressive resynchronization method enables the restored motor to smoothly rejoin synchronous control, including steps such as speed synchronization, position calibration, and load redistribution, ensuring a smooth transition to normal system operation and avoiding shock and oscillation during the recovery process. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0071] Figure 1 The present invention provides an overall flow chart of a method for synchronous fault-tolerant control of the speed of a dual-servo motor system according to an embodiment of the present invention.

[0072] Figure 2 An embodiment of the present invention provides a motor health evaluation index calculation process for a dual servo motor system speed synchronization fault-tolerant control method. DETAILED DESCRIPTION

[0073] To make the above-mentioned objects, features, and advantages of the present invention more clearly understood, the following detailed description of the specific embodiments of the present invention is given in conjunction with the accompanying drawings. It is obvious that the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in this field without creative work should fall within the scope of protection of the present invention.

[0074] Example 1, reference Figures 1 and 2 , is an embodiment of the present invention, which provides a speed synchronization fault-tolerant control method for a dual servo motor system, comprising the following steps:

[0075] S1. Collect the state information of the dual servo motors and construct a multi-dimensional state vector.

[0076] Status information includes speed, torque, current, temperature and vibration signals;

[0077] Wherein, the multidimensional state vector is expressed as:

[0078] X=[ω1,ω2,τ1,τ2,i1,i2,Temp1,Temp2,V ib1 ,V ib2 ] T ;

[0079] Where X is the multidimensional state vector, ω1, ω2 are the speeds of the first motor and the second motor, τ1, τ2 are the torques of the first motor and the second motor, i1, i2 are the currents of the first motor and the second motor, and T emp1 ,T emp2 is the temperature of the first motor and the second motor, V ib1 ,V ib2 are the vibration signals of the first motor and the second motor.

[0080] S2. Performing fusion processing on the multi-dimensional state vector through a signal fusion processor to obtain a motor health assessment index.

[0081] The steps of calculating the motor health evaluation index include: filtering the multidimensional state vector using a Kalman filter, performing optimal estimation based on the collected state information, and obtaining a filtered state estimation vector;

[0082] In the embodiment of the present application, it is assumed that the collected original multidimensional state vector is:

[0083] X raw =[1500,1502,25.2,25.0,8.5,8.7,45,47,0.2,0.3];

[0084] The filter state estimation vector is expressed as:

[0085] X f filtered=[1500.1,1501.8,25.1,25.1,8.6,8.6,45.2,46.8,0.22,0.28];

[0086] The speed deviation, torque deviation and current deviation between the dual servo motors, as well as the temperature deviation and vibration deviation of the dual servo motors relative to the preset reference value are calculated respectively through the filtered state estimation vector;

[0087] Calculate various deviations based on the filtered state estimate vector:

[0088] The speed deviation is Δω=|1500.1-1501.8|=1.7rpm;

[0089] The torque deviation is Δτ = |25.1-25.1| = 0 N·m;

[0090] The current deviation is Δi=|8.6-8.6|=0A;

[0091] Temperature deviation is ΔT emp =max(|45.2-40|,|46.8-40|)=6.8℃(reference temperature 40℃);

[0092] Vibration deviation is ΔV ib =max(|0.22-0.1|,|0.28-0.1|)=0.18m / s 2 (reference vibration 0.1m / s 2 ).

[0093] Normalize all deviation values.

[0094] Among them, it is important to know that the system rated parameter is set to the rated speed ω nom =1500rpm, rated torque τ nom =30N·m, rated current i nom =10A, maximum allowable temperature T emp,max =80℃, and the maximum permissible vibration V ib,max =1.0m / s 2 After the normalized deviation is calculated, it is expressed as:

[0095] Normalized speed deviation: 1.7 / 1500=0.00113;

[0096] Torque normalization deviation: 0 / 30=0;

[0097] Current normalization deviation: 0 / 10=0;

[0098] Temperature normalized deviation: 6.8 / 80=0.085;

[0099] Vibration normalized deviation: 0.18 / 1.0=0.18.

[0100] Multiply each normalized deviation value by the corresponding weighting coefficient, and then perform weighted summation to obtain the motor health assessment index;

[0101] Among them, the calculation formula of the motor health assessment index H is expressed as:

[0102]

[0103] Where α1, α2, α3, α4, and α5 are weighted coefficients of speed deviation, torque deviation, current deviation, temperature deviation, and vibration deviation, respectively; Δω, Δτ, Δi, and ΔT are weighted coefficients of speed deviation, torque deviation, current deviation, temperature deviation, and vibration deviation, respectively; emp , ΔV ibare the speed deviation, torque deviation, current deviation, temperature deviation relative to the reference value, and vibration deviation relative to the reference value between the two servo motors; ω nom , τ nom ,i nom , T emp,max , V ib,max They are rated speed, rated torque, rated current, maximum allowable temperature, and maximum allowable vibration value;

[0104] The constraints are:

[0105]

[0106] Where j is the summation indicator variable.

[0107] The set constraints are: α1+α2+α3+α4+α5=0.3+0.2+0.2+0.15+0.15=1; then substituted into the formula, and the final output is the motor health assessment index H=0.040089;

[0108] Since the H value is close to 0, it indicates that the overall health of the system is good, the main deviations come from slight anomalies in temperature and vibration, and the speed synchronization performance is excellent.

[0109] S3. Analyze the motor health evaluation index, select different control modes according to the analysis results, and control the dual servo motors using corresponding control algorithms according to the selected control modes.

[0110] The control modes include precision synchronization mode, fault-tolerant operation mode and emergency protection mode. When selecting different control modes, the selection rules are as follows:

[0111] When H≤0.3 and the speed difference between the two servo motors is less than 0.5% of the reference speed, select the precision synchronization mode;

[0112] The precise synchronization mode uses a cross-coupling control algorithm, and the specific steps include:

[0113] Obtaining deviations between actual position signals of the first motor and the second motor and their respective position commands, respectively, to obtain a first motor position error and a second motor position error;

[0114] Subtracting the second motor position error from the first motor position error to obtain a coupling error signal;

[0115] Performing a proportional-integral operation on the coupling error signal, wherein the proportional component is obtained by multiplying the coupling error by a proportional gain coefficient, and the integral component is obtained by integrating the coupling error and then multiplying it by the integral gain coefficient, and the two components are added to obtain a coupling control amount;

[0116] The coupling control amount is added to the output of the independent position controller of the first motor in a positive form, and is added to the output of the independent position controller of the second motor in a negative form to form their respective final control instructions.

[0117] In this embodiment, if the calculated H=0.040089 and the current speed difference is |1500.1-1501.8|=1.7 rpm, the reference speed is 1500 rpm, and the speed difference percentage is 1.7 / 1500×100%=0.113%. Therefore, the precise synchronization mode is executed as follows:

[0118] Actual position signal acquisition: first motor position command θ 1cmd =180.0°, the actual position of the first motor θ 1actual =179.8°, the second motor position command θ 2cmd =180.0°, actual position of the second motor θ 2actual =180.3°;

[0119] Position error calculation: first motor position error e1 = 180.0° - 179.8° = 0.2°, second motor position error e2 = 180.0° - 180.3° = -0.3°;

[0120] Coupling error signal generation: Coupling error signal e couple =e1-e2=0.2°-(-0.3°)=0.5°;

[0121] Proportional integral operation: proportional gain coefficient Kc = 15, integral gain coefficient Kic = 8, integral term cumulative value ∫e coupldt =0.12°·s (historical accumulation), proportional component P couple =15×0.5°=7.5V, integral component I couple =8×0.12°·s=0.96V, coupling control value u couple =7.5+0.96=8.46V;

[0122] Control command superposition: the first motor independent controller outputs u 1i =25.2V, the second motor independent controller output u 2i =24.8V, the final control instruction of the first motor u 1f =25.2+8.46=33.66V, the final control command of the second motor: u 2f =24.8-8.46=16.34V;

[0123] After cross-coupling control, it is expected that the position error of the dual servo motors will be reduced and the synchronization accuracy will be improved in the next control cycle.

[0124] When H ≤ 0.3 and the rotational speed difference between the two servo motors is greater than or equal to 0.5% of the reference rotational speed, select the fault-tolerant operation mode;

[0125] When 0.3 < H ≤ 0.8, select the fault-tolerant operation mode;

[0126] The fault-tolerant operation mode adopts a single-machine enhanced control algorithm. The specific steps include:

[0127] Based on the comparison of the respective status information of the first motor and the second motor, obtain the motor with better health status as the enhanced control object, and the motor with poor health status maintains the basic control;

[0128] Adjust the parameters of the controller of the enhanced control object, increase the proportional gain coefficients of its position controller and speed controller by 20 - 50%, and at the same time reduce the time constant of the control system by 30 - 80%, and adjust the integral gain coefficient and differential gain coefficient to maintain the stability of the system;

[0129] Calculate the compensation amount according to the performance loss degree of the motor with poor health status;

[0130] Superimpose the output of the adjusted controller and the compensation amount to generate an enhanced control command for the enhanced control object.

[0131] In this embodiment, when the fault-tolerant operation mode is executed, first, the status score of the first motor: rotational speed stability 85%, torque fluctuation 5%, comprehensive score 80%; the status score of the second motor: rotational speed stability 75%, torque fluctuation 12%, comprehensive score 63%. Therefore, select the first motor as the enhanced control object.

[0132] The original proportional gain Kp = 20, the adjusted proportional gain Kp new = 20 × 1.35 = 27 (increased by 35%);

[0133] The original time constant T = 0.05s, the adjusted time constant T new = 0.05 × 0.6 = 0.03s (decreased by 40%);

[0134] The performance loss of the second motor is 37% (100% - 63%), the speed compensation amount is 1500 × 0.37 = 555rpm, and the torque compensation amount is 25 × 0.37 = 9.25N·m.

[0135] Enhanced control command generation: The basic control output of the first motor is 30V, and the control command after superimposing the compensation is 30 + 12.8 = 42.8V (including speed and torque compensation).

[0136] When H > 0.8, select the emergency protection mode;

[0137] The emergency protection mode uses a safety shutdown algorithm, the specific steps include:

[0138] Set the downtime of the dual servo motors from current speed to zero speed to 3-10 seconds;

[0139] During the first 40% of the downtime, a maximum allowable deceleration is applied to the dual servo motors to perform linear deceleration control, reducing the speed of the dual servo motors from the current speed value to 30% of the rated speed;

[0140] During the middle 30% of the downtime, a quadratic curve deceleration control law is applied to the dual servo motors, and the deceleration value changes in a decreasing manner according to a quadratic function relationship, reducing the speed of the dual servo motors from 30% of the rated speed to 5% of the rated speed;

[0141] During the last 30% of the downtime, an exponential decay deceleration control law is applied to the dual servo motors to reduce the speed of the dual servo motors from 5% of the rated speed to zero speed at a deceleration value that is less than 10% of the maximum allowable deceleration;

[0142] When the speed of the dual servo motors drops to zero, the motor power supply is disconnected, the mechanical brake device is activated, the system status flag is set to a safety lock state, and the sound and light alarm device is activated to send out a fault warning signal.

[0143] In this embodiment,

[0144] Assuming the system is abnormal, H = 0.85; therefore:

[0145] Stop time setting: the current speed is 1500rpm, the stop time is set to 6 seconds, the time distribution is 2.4s for rapid deceleration, 1.8s for buffered deceleration, and 1.8s for precise stop;

[0146] Then in the first stage (0-2.4s): deceleration is applied -200rad / s 2 (maximum allowable deceleration), speed change, 1500rpm→471rpm (about 30% of rated speed);

[0147] In the second stage (2.4-4.2s): quadratic curve deceleration is used: a(t) = -200 × (1-0.8 × (t-2.4) / 1.8) 2 , speed changes from 471rpm to 75rpm (approximately 5% of rated speed);

[0148] The third stage (4.2-6.0s): exponential decay deceleration: a(t) = -20×e -2×(t-4.2) , the speed changes from 75rpm to 0rpm.

[0149] Finally, at 6.0s, the motor power is disconnected; at 6.1s, the mechanical brake is activated; at 6.2s, the safety lock flag is set; at 6.3s, the sound and light alarm is activated, issuing an alarm of "system failure, equipment has been safely shut down."

[0150] S4. During the control execution process, the motor state is detected for faults, and the fault-tolerant control strategy is started when fault signs are detected.

[0151] The steps for detecting motor faults include A1 to A2:

[0152] A1: Analyze the status information of the dual servo motors to obtain the frequency characteristic parameters and energy distribution characteristic parameters of the signals;

[0153] In this embodiment, taking the printing device as an example, during the operation of the precision synchronization mode of the printing device, the system continuously collects the status information of the dual servo motors for analysis. Taking the first motor as an example, the vibration sensor collects a vibration signal of 2 seconds at a sampling frequency of 1000 Hz, and obtains an original time domain signal sequence containing 2000 data points [0.22, 0.21, 0.23, 0.22, 0.24, 0.20, 0.25, ...]. The time domain signal is preprocessed to reduce spectral leakage, and then a 2048-point fast Fourier transform is performed to convert the time domain signal into a frequency domain representation. The analysis results show that a clear main frequency peak is detected at 50 Hz with an amplitude of 0.15 m / s 2 , which corresponds to the fundamental frequency vibration of the motor; side frequency components are found at 48Hz and 52Hz, with amplitudes of 0.02 and 0.03m / s respectively 2 ; In the high frequency range of 200-500Hz, the average amplitude is 0.01m / s 2 .

[0154] According to the frequency domain analysis results, the key frequency characteristic parameters are extracted. The main frequency amplitude characteristic parameter is defined as the maximum amplitude at the main frequency of 0.15m / s 2; The sideband energy ratio characteristic parameter is calculated as the ratio of the sideband component energy to the main frequency energy, that is, (0.02+0.03) / 0.15=0.33; the high frequency band energy ratio characteristic parameter is the ratio of the total energy of the high frequency band to the total energy of the entire frequency band, which is 0.067. At the same time, the system divides the entire spectrum into three intervals: low frequency band (0-100Hz), medium frequency band (100-300Hz) and high frequency band (300-500Hz), and calculates the energy distribution of each frequency band respectively. By integrating the spectrum density function, the energy of the low frequency band, medium frequency band and high frequency band are 0.025J, 0.008J and 0.003J respectively, and the total energy is 0.036J. The energy distribution characteristic parameters are obtained as follows: low frequency energy accounts for 69.4%, medium frequency energy accounts for 22.2%, and high frequency energy accounts for 8.3%. The same analysis method is used for the second motor to obtain a main frequency amplitude of 0.18m / s 2 , sideband energy ratio 0.50, high-frequency energy ratio 0.111, and energy distribution ratio are 64.0%, 24.0%, and 12.0% respectively.

[0155] A2: Establish a reference database containing normal operating modes and abnormal operating modes, compare and analyze the extracted frequency characteristic parameters and energy distribution characteristic parameters with the standard modes in the reference database, and identify fault characteristics based on the matching results.

[0156] Based on a large amount of historical operating data and technical specifications provided by equipment manufacturers, a comprehensive reference database including normal operating modes and various abnormal operating modes has been established. The standard characteristic range of normal operating mode is determined based on statistical analysis: the main frequency amplitude range is set to 0.10-0.20m / s 2 , covering 95% of normal operating conditions; the sideband energy ratio range of 0.20-0.40 reflects the normal mechanical transmission characteristics; the high-frequency energy ratio range of 0.05-0.10 corresponds to normal surface roughness and assembly accuracy; the energy distribution ratio ranges are 65%-75% for low frequency, 20%-25% for medium frequency, and 5%-15% for high frequency. These ranges are based on 6 months of continuous monitoring data from 300 similar devices.

[0157] The feature library of abnormal operation modes contains characteristic signatures of various typical fault modes. The characteristic identification of bearing fault modes is that the sideband energy ratio is greater than 0.60, the high-frequency energy ratio is greater than 0.15, and significant peaks appear at specific frequency points (such as the inner ring fault frequency of 162Hz, the outer ring fault frequency of 108Hz, and the rolling element fault frequency of 67Hz); the unbalanced fault mode is characterized by a main frequency amplitude exceeding 0.25m / s 2The rotation frequency and its frequency multiple components increase significantly, and the phase difference between the left and right motors exceeds 90°; the loose fault mode is characterized by low-frequency energy accounting for more than 80%, obvious subharmonic components, and the time domain waveform presents obvious impact characteristics; the winding fault mode is manifested in the spectrum of the current signal as an abnormal increase in the 2nd frequency component.

[0158] The feature parameters extracted in step A1 are matched and compared with the reference database, and then the matching degree is calculated using the weighted Euclidean distance algorithm. For the first motor, the main frequency amplitude is 0.15m / s 2 The results were in the middle of the normal range, with a 95% match. The sideband energy ratio of 0.33 was within the normal range, with a 90% match. The high-frequency energy ratio of 0.067 was close to the normal median, with a 85% match. The energy distribution ratio deviated slightly from the normal pattern, with a 92% match. The overall match, calculated as the weighted average of the matching degrees of each indicator, was 90.5%, far exceeding the set normal threshold of 85%. Therefore, the first motor was determined to be in a normal state.

[0159] The matching analysis for the second motor shows different results. The main frequency amplitude is 0.18m / s 2 The data remained within the normal range, with a match of 88%. However, the sideband energy ratio of 0.50 exceeded the upper limit of the normal range of 0.40. Through abnormal pattern matching, this was found to be close to the characteristic threshold of 0.60 for bearing failure, reducing the match to 60%. The high-frequency energy ratio of 0.111 exceeded the upper limit of 0.10, consistent with the early signs of bearing wear, with a match of 55%. The low-frequency energy ratio of 64.0% was slightly below the lower limit of 65%, with a match of 70%. The overall match was 68.25%, below the normal threshold. Further comparison with the abnormal pattern library revealed a 75% match with the early bearing failure pattern, but not yet reaching the 90% threshold for immediate intervention. Based on this, the second motor was identified as having suspected early bearing failure characteristics, and monitoring was strengthened, but the current operating mode was maintained.

[0160] The steps of the fault-tolerant control strategy include: determining the faulty motor and the healthy motor among the first motor and the second motor according to the fault detection result; calculating the load amount to be transferred according to the remaining operating capacity of the faulty motor, and gradually transferring the load of the faulty motor to the healthy motor;

[0161] In this embodiment, it is assumed that during subsequent operation, the fault characteristics of the second motor further deteriorate, the sideband energy ratio increases from 0.50 to 0.68, and the high-frequency energy ratio increases from 0.111 to 0.158. The matching degree with the bearing fault mode reaches 92%, exceeding the 90% immediate intervention threshold, and then the fault-tolerant control strategy is automatically initiated. Based on the fault detection results and the comparative analysis of the dual motor states, the second motor is identified as the faulty motor and the first motor as the healthy motor. The various characteristic parameters of the first motor remain within the normal range, and the comprehensive matching degree remains above 90%, with the ability to bear additional loads. Although the second motor detects signs of bearing failure, basic parameters such as current and torque are still within the controllable range, and its remaining operating capacity is estimated to be approximately 65% ​​of the normal state.

[0162] The load required to be transferred is calculated based on the remaining operating capacity of the faulty motor. Under normal operating conditions, the two motors each carry 50% of the total load, meaning each motor carries a torque load of 15 N·m. Since the second motor's remaining operating capacity is 65%, its safe load capacity is reduced to 15 × 0.65 = 9.75 N·m, and the load required to be transferred is 15 - 9.75 = 5.25 N·m. The system adopts a phased, gradual load transfer strategy to avoid sudden load changes that could impact the system. In the first phase, 30% of the required load is transferred, namely 5.25 × 0.30 = 1.58 N·m, reducing the load on the second motor to 13.42 N·m and increasing the load on the first motor to 16.58 N·m. In the second phase, another 60% of the load is transferred, reducing the load on the second motor to 11.85 N·m and increasing the load on the first motor to 18.15 N·m. The third stage completes 90% of the load transfer, and finally the second motor bears a load of 10.28N·m and the first motor bears a load of 19.72N·m.

[0163] A virtual reference axis is established as a unified position and speed reference, so that the healthy motor can track the virtual reference axis. At the same time, the compensation amount is calculated according to the operating deviation of the faulty motor and added to the control instruction of the healthy motor to compensate for the speed deviation and position deviation of the faulty motor.

[0164] Specifically, in order to achieve accurate synchronous compensation control, the system establishes a virtual reference axis as a unified position and speed reference. The position instruction of the virtual reference axis is set to θ according to the printing process requirements. virtual(t)=1500×2π×t / 60+θ0, corresponding to a constant speed of 1500rpm. The first motor uses an enhanced PID controller to track the virtual reference axis. The control parameters of the position loop, speed loop, and current loop are adjusted to 1.3 times the original parameters to improve its dynamic response capability and load bearing capacity. At the same time, the deviation between the second motor and the virtual reference axis is continuously monitored and the real-time compensation amount is calculated. When it is detected that the position of the second motor lags the virtual reference axis by 0.8°, the system calculates the position compensation amount Δθ comp =0.8°; when the speed deviation is detected to be -3rpm, the speed compensation is calculated as Δω comp =3rpm.

[0165] The superposition of compensation is achieved through feedforward compensation, which converts the position compensation and speed compensation into corresponding torque compensation and then superimposes them into the control command of the first motor. Position compensation torque Tpos comp =Kp comp × 0.8°=2.4N·m (where Kp comp =3 is the position compensation gain); the speed compensation torque is Tvel comp =Kv comp ×3rpm=1.2N·m (where Kv comp = 0.4 is the speed compensation gain). The final control command for the first motor is its basic PID control output plus a load compensation of 5.25 N·m and a deviation compensation of 3.6 N·m, for a total control output increase of 8.85 N·m. This virtual axis tracking and dynamic compensation mechanism allows the enhanced control capability of the first motor to maintain the overall synchronization accuracy of the dual-motor system even when the second motor's performance degrades. This reduces the original ±0.5° synchronization error to an acceptable range of ±1.2°, ensuring that printing quality is not significantly affected.

[0166] Monitoring of the fault-tolerant control strategy after implementation showed stable operation under fault conditions. The first motor operated stably under enhanced control mode, keeping temperature rise within a safe range. The second motor's fault symptoms were effectively controlled under reduced load, preventing further deterioration.

[0167] Finally, when the faulty motor returns to normal operation, the following steps are also included:

[0168] Detect the operating status of the faulty motor and determine that it has returned to normal when its health assessment index returns to the preset range and the operation is stable; adjust the speed of the faulty motor and set the speed difference of the dual servo motors to within 2% of the reference speed; adjust the position of the faulty motor on the basis of speed synchronization so that its position deviation from the healthy motor is controlled within 5 degrees; transfer the load transferred to the healthy motor back to the faulty motor in the opposite order of load transfer, and control the transfer speed at 5-10% per second; when the load redistribution is completed, restart the dual servo motor synchronous control.

[0169] In this embodiment, when the signs of the bearing failure of the second motor gradually improve, continuous monitoring shows that the sideband energy ratio of the second motor drops from 0.68 to 0.35, and the high-frequency energy ratio drops from 0.158 to 0.08, both returning to the preset range, and the matching degree with the normal mode is restored to 88%. At the same time, the health assessment index of the second motor drops from 0.75 at the time of failure to 0.12, meeting the preset recovery standard of less than 0.3, and after 30 minutes of continuous stable operation without abnormal fluctuations, it is determined that the second motor has returned to normal.

[0170] First, the speed of the second motor was adjusted, gradually increasing from the current 1485 rpm to the target speed of 1500 rpm. Through closed-loop speed control, the second motor's speed steadily reached 1498 rpm within 8 seconds. The difference from the first motor's speed of 1500 rpm was 2 rpm, representing 0.13% of the reference speed of 1500 rpm, far less than the required 2%. Position synchronization was then adjusted. The second motor's current position was 178.5 degrees, while the first motor's position was 180.0 degrees, resulting in a position deviation of 1.5 degrees, meeting the synchronization requirement of less than 5 degrees. Through position compensation control, the position deviation was reduced to 0.3 degrees within 5 seconds.

[0171] Load redistribution was performed in the reverse order of the initial transfer, at a rate of 8% per second. The first stage involved transferring a portion of the previously transferred 90% load back to the second motor. The entire load redistribution process took 15 seconds, during which the system maintained synchronization accuracy within ±0.8 degrees. Once load redistribution was complete, the system automatically exited fault-tolerant operation and re-initiated standard dual-servo motor synchronization, ensuring synchronization accuracy returned to a normal level of ±0.3 degrees, fully restoring pre-fault operation.

[0172] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for synchronous fault-tolerant control of the speed of a dual servo motor system, characterized in that: It includes the following steps: Collect the state information of the dual servo motors and construct a multi-dimensional state vector; Perform fusion processing on the multi-dimensional state vector through a signal fusion processor to obtain a motor health assessment index; Analyze the motor health assessment index, select different control modes according to the analysis results, and control the dual servo motors using corresponding control algorithms according to the selected control modes; During the execution of the control, detect faults in the motor state, and start a fault-tolerant control strategy when a fault symptom is detected.

2. A dual servo motor system speed synchronization fault-tolerant control method according to claim 1, characterized in that: The state information includes rotational speed, torque, current, temperature, and vibration signals; Among them, the multi-dimensional state vector is expressed as: X=[ω1,ω2,τ1,τ2,i1,i2,Temp1,Temp2,V ib1 ,V ib2 ] T ; Where X is the multidimensional state vector, ω1, ω2 are the speeds of the first motor and the second motor, τ1, τ2 are the torques of the first motor and the second motor, i1, i2 are the currents of the first motor and the second motor, and T emp1 ,T emp2 is the temperature of the first motor and the second motor, V ib1 ,V ib2 are the vibration signals of the first motor and the second motor.

3. A dual servo motor system speed synchronization fault-tolerant control method as claimed in claim 2, characterized in that: The calculation steps of the motor health assessment index include: Use a Kalman filter to filter the multi-dimensional state vector, perform optimal estimation through the collected state information, and obtain a filtered state estimation vector; Based on the filtered state estimation vector, calculate the rotational speed deviation, torque deviation, and current deviation between the dual servo motors, as well as the temperature deviation and vibration deviation of the dual servo motors relative to the preset reference values respectively; Normalize all deviation values, multiply each normalized deviation value by the corresponding weighting coefficient, and then perform weighted summation to obtain the motor health assessment index; Among them, the calculation formula of the motor health assessment index H is expressed as: Where α1, α2, α3, α4, and α5 are weighted coefficients of speed deviation, torque deviation, current deviation, temperature deviation, and vibration deviation, respectively; Δω, Δτ, Δi, and ΔT are weighted coefficients of speed deviation, torque deviation, current deviation, temperature deviation, and vibration deviation, respectively; emp , ΔV ib are the speed deviation, torque deviation, current deviation, temperature deviation relative to the reference value, and vibration deviation relative to the reference value between the two servo motors; ω nom , τ nom ,i nom , T emp,max , V ib,max They are rated speed, rated torque, rated current, maximum allowable temperature, and maximum allowable vibration value; The constraint condition is: In the formula, j is the summation index variable.

4. A dual servo motor system speed synchronization fault-tolerant control method as claimed in claim 3, characterized in that: The control modes include a precision synchronization mode, a fault-tolerant operation mode, and an emergency protection mode. When selecting different control modes, the selection rules are: When H ≤ 0.3 and the rotational speed difference between the dual servo motors is less than 0.5% of the reference rotational speed, select the precision synchronization mode; When H ≤ 0.3 and the rotational speed difference between the dual servo motors is greater than or equal to 0.5% of the reference rotational speed, select the fault-tolerant operation mode; When 0.3 < H ≤ 0.8, select the fault-tolerant operation mode; When H > 0.8, select the emergency protection mode.

5. A dual servo motor system speed synchronization fault-tolerant control method as claimed in claim 4, characterized in that: The precision synchronization mode adopts a cross-coupling control algorithm, and the specific steps include: Respectively obtain the deviation between the actual position signal of the first motor and the second motor and their respective position commands, and obtain the position error of the first motor and the position error of the second motor; Subtract the position error of the second motor from the position error of the first motor to obtain a coupling error signal; Perform proportional-integral operation on the coupling error signal. The proportional component is obtained by multiplying the coupling error by the proportional gain coefficient, and the integral component is obtained by integrating the coupling error and then multiplying by the integral gain coefficient. The two components are added to obtain a coupling control quantity; Superimpose the coupling control quantity onto the output of the independent position controller of the first motor in a positive form, and superimpose it onto the output of the independent position controller of the second motor in a negative form to form their respective final control commands.

6. A dual servo motor system speed synchronization fault-tolerant control method according to claim 5, characterized in that: The fault-tolerant operation mode adopts a single-machine enhancement control algorithm, and the specific steps include: Compare according to the state information of the first motor and the second motor respectively, and obtain the motor with better health status as the enhancement control object, and the motor with poor health status maintains the basic control; Adjusting parameters of the controller of the enhanced control object, increasing the proportional gain coefficients of its position controller and speed controller by 20-50%, reducing the time constant of the control system by 30-80%, and adjusting the integral gain coefficient and the differential gain coefficient to maintain system stability; Calculate the compensation amount based on the degree of performance loss of the motor in poor health; The adjusted controller output is superimposed on the compensation amount to generate an enhanced control instruction for the enhanced control object.

7. A dual servo motor system speed synchronization fault-tolerant control method according to claim 6, characterized in that: The emergency protection mode adopts a safety shutdown algorithm, and the specific steps include: Set the downtime of the dual servo motors from current speed to zero speed to 3-10 seconds; During the first 40% of the downtime, a maximum allowable deceleration is applied to the dual servo motors to perform linear deceleration control, reducing the speed of the dual servo motors from the current speed value to 30% of the rated speed; During the middle 30% of the downtime, a quadratic curve deceleration control law is applied to the dual servo motors, and the deceleration value changes in a decreasing manner according to a quadratic function relationship, reducing the speed of the dual servo motors from 30% of the rated speed to 5% of the rated speed; During the last 30% of the downtime, an exponential decay deceleration control law is applied to the dual servo motors to reduce the speed of the dual servo motors from 5% of the rated speed to zero speed at a deceleration value that is less than 10% of the maximum allowable deceleration; When the speed of the dual servo motors drops to zero, the motor power supply is disconnected, the mechanical brake device is activated, the system status flag is set to a safety lock state, and the sound and light alarm device is activated to send out a fault warning signal.

8. A dual servo motor system speed synchronization fault-tolerant control method according to claim 7, characterized in that: The steps for fault detection of motor status include: Analyze the state information of the dual servo motors to obtain the frequency characteristic parameters and energy distribution characteristic parameters of the signals; A reference database containing normal operating modes and abnormal operating modes is established, and the extracted frequency characteristic parameters and energy distribution characteristic parameters are compared and analyzed with the standard modes in the reference database. The fault characteristics are identified based on the matching results.

9. A dual servo motor system speed synchronization fault-tolerant control method according to claim 8, characterized in that: The steps of the fault-tolerant control strategy include: determining a faulty motor and a healthy motor among the first motor and the second motor according to the fault detection result; Calculate the load that needs to be transferred based on the remaining operating capacity of the faulty motor, and gradually transfer the load of the faulty motor to the healthy motor; A virtual reference axis is established as a unified position and speed reference, so that the healthy motor can track the virtual reference axis. At the same time, the compensation amount is calculated according to the operating deviation of the faulty motor and added to the control instruction of the healthy motor to compensate for the speed deviation and position deviation of the faulty motor.

10. A dual servo motor system speed synchronization fault-tolerant control method according to claim 9, characterized in that: When the faulty motor returns to normal operation, the following steps are also included: Detect the operating status of the faulty motor and determine that it has returned to normal when its health assessment index returns to the preset range and the operation is stable; Adjust the speed of the faulty motor and set the speed difference of the dual servo motors to within 2% of the reference speed; Adjust the position of the faulty motor based on speed synchronization so that the position deviation with the healthy motor is controlled within 5 degrees; In the reverse order of load transfer, transfer the load transferred to the healthy motor back to the faulty motor, with the transfer speed controlled at 5-10% per second; When the load redistribution is completed, the dual servo motor synchronous control is restarted.

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