A method for rapid identification of elevator encoder faults

Abstract

This invention discloses a method for rapid identification of elevator encoder faults. During closed-loop vector control (FVC), encoder fault judgment logic is added. Based on the following combination of conditions: Condition A, the flux linkage position error calculation module, is triggered when the error between the flux linkage position angle calculated by the encoder sampling and the flux linkage position angle estimated by the flux linkage observer exceeds a set threshold Value1; Condition B, the speed change rate calculation module, is triggered when the absolute value of the motor speed calculated from the encoder position angle decreases at a rate exceeding a set threshold Value2; Condition C, the current change rate calculation module, is triggered when the amplitude of the comprehensive vector value of the three-phase motor current increases at a rate exceeding a set threshold Value3. If the triggering state remains active after a confirmation time for different condition combinations, an encoder fault is determined, and the motor control is switched online from FVC to SVC control to prevent elevator entrapment accidents in case of a fault.

Description

Technical Field

[0001] This invention relates to the field of elevator control technology, and more specifically to a method for rapid identification of elevator encoder faults. Background Technology

[0002] Elevators, as vertical transportation tools in building systems, provide convenience for people's lives and travel. As special equipment, elevators involve various aspects such as safety, leveling accuracy, and comfort. Open-loop vector control (SVC) without speed feedback has not been chosen as an option for driving elevator traction motors; currently, all elevators use closed-loop vector control (FVC) technology with encoder speed feedback. However, in FVC control, if the encoder fails, the entire motor control fails, and the elevator will stop. If the encoder fails during elevator operation, vector control cannot execute correctly, the motor loses torque or even provides counter-torque, causing the elevator to stall and run away, the inverter to experience overcurrent or even explode, ultimately leading to the elevator stopping between two floors and causing a passenger entrapment accident.

[0003] An obvious solution is to automatically switch to sensorless open-loop vector control (SVC) when the elevator stops due to encoder failure, allowing the car to be moved back to the door level for passengers, thus resolving the entrapment issue. However, this method has two drawbacks: firstly, the elevator experiences an abrupt stop, causing discomfort for passengers; secondly, encoder failure can easily lead to elevator stalling and overspeeding during FVC control, potentially causing the speed governor or safety brakes to activate, or the inverter to burn out due to overcurrent. These hardware failures prevent the elevator from automatically resuming operation, making entrapment accidents difficult to avoid.

[0004] For example, Chinese patent application publication number CN109787522A discloses an online switching method between FVC and SVC. This method uses a main controller to control the activation of either the SVC or FVC controller. The main controller switches the control mode based on the actual operating state of the motor. However, this application does not explain the specific switching logic of the main controller. In the elevator industry, closed-loop vector control (FVC) is required throughout the entire process to ensure elevator comfort. Under normal elevator conditions, online switching between FVC and SVC has no practical significance for elevator operation. Furthermore, because SVC control performance is difficult to achieve smooth start-up, good running comfort, and high leveling accuracy, long-term operation cannot guarantee elevator safety. Therefore, SVC is only used as a temporary operating mode after encoder failure. That is, only when the elevator encoder fails should FVC be switched online to SVC for temporary operation, allowing the elevator to reach the elevator door zone, open the door to let people in, and then stop, thus avoiding the elevator suddenly stopping and trapping people. This is the problem that needs to be solved in the elevator industry.

[0005] However, accurately diagnosing encoder faults online is a challenge. Misjudgments of encoder faults can cause the elevator to unexpectedly enter SVC mode, resulting in it stopping at the door zone, or fail to detect a fault, leading to an abrupt stop and passenger dissatisfaction. Therefore, accurate encoder fault diagnosis is crucial. Another issue is the need for high real-time encoder fault detection due to the online switching from FVC to SVC. When the encoder is functioning correctly, the elevator operates in FVC control mode; when a fault occurs, it operates in SVC control mode. During the period before the system detects the encoder fault, the elevator remains in FVC control mode, effectively rendering FVC ineffective. Prolonged failure during this period can cause the elevator to run away unnecessarily. Therefore, real-time, rapid encoder fault detection capabilities are essential.

[0006] Open circuit detection for conventional incremental ABZ encoders is often achieved through hardware detection circuits. For example, Chinese patents CN114935715A and CN114910822A describe methods for detecting open circuits in incremental encoders. However, on the one hand, encoder faults are not limited to open circuits; they may also include fixed faults, cross-short circuits, circuit oscillations, and other issues, which are difficult to detect using hardware detection circuits. On the other hand, while hardware open circuit detection can be used for incremental ABZ encoders, other encoders, especially analog encoders such as Sin-Cos encoders, cannot be detected using purely hardware-based testing circuits. Especially during elevator operation, the encoder's output signal is constantly changing, making it even more difficult to confirm the correct state of analog encoders. Software identification methods are also challenging and time-consuming. During this detection period, maintaining FVC (Frequency Controlled Variable Voltage) may lead to inverter overcurrent or elevator overrunning, failing to meet the requirement of online switching to SVC (Signal Controlled Variable Voltage) operation after encoder failure. Summary of the Invention

[0007] The purpose of this invention is to provide a method for rapid identification of elevator encoder faults, and to realize the online switching from closed-loop vector control (FVC) to open-loop vector control (SVC) under fault conditions. This allows the elevator to continue running in SVC to the elevator door zone level position to release people even when the encoder is faulty. The whole process does not involve the experience of sudden stop or elevator closure, and will not lead to the accident of people being trapped in the elevator.

[0008] The objective of this invention can be achieved through the following technical solutions:

[0009] A method for rapid fault identification of elevator encoders includes:

[0010] During closed-loop vector control (FVC), encoder fault detection logic is added;

[0011] Based on the following combination of conditions:

[0012] Condition A: The flux linkage position error calculation module calculates the error between the flux linkage position angle calculated by the encoder and the flux linkage position angle estimated by the flux linkage observer. It is triggered when the error exceeds the set threshold Value1.

[0013] Condition B: The speed change rate calculation module is triggered when the absolute value of the motor speed calculated from the encoder position angle decreases beyond the set threshold Value2.

[0014] Condition C: The current change rate calculation module is triggered when the rate of increase of the comprehensive vector value of the three-phase current of the motor exceeds the set threshold Value3.

[0015] By using different combinations of conditions and different delay confirmation times, the more conditions that are triggered, the shorter the confirmation time. If the condition combination remains in the triggered state after the confirmation time has elapsed, it is determined to be an encoder malfunction.

[0016] As a further aspect of the present invention, different delay confirmation times include:

[0017] If only condition A or condition B is triggered, the delayed confirmation time is T1.

[0018] If conditions A and B are triggered simultaneously, the delay confirmation time is T2, where T1 > T2;

[0019] Where T1 is 10ms, T2 is 2ms, and condition C is an auxiliary condition;

[0020] If condition C is triggered simultaneously during the process of triggering condition A or condition B, the required confirmation time will be reduced accordingly, and the delayed confirmation time will be half of T1 or T2.

[0021] As a further aspect of the present invention: the flux linkage observer estimation module in the flux linkage position error calculation module is a hybrid flux linkage estimation model that combines the voltage model and current model of the electric motor;

[0022] The flux linkage observer estimation module estimates the flux linkage position using the motor's current and voltage response, then compares it with the flux linkage position obtained by the encoder, and uses the error between the two to determine whether the encoder is in an abnormal state.

[0023] As a further aspect of the present invention: after an encoder failure, the elevator immediately switches online from closed-loop vector control (FVC) to open-loop vector control (SVC) without stopping the elevator;

[0024] The elevator stops after reaching the nearest floor door area.

[0025] As a further aspect of the present invention: a rapid fault identification device for elevator encoders, comprising:

[0026] A flux linkage position error calculation module is used to calculate the error between the flux linkage position angle calculated by the encoder sampling and the flux linkage position angle estimated by the flux linkage observer.

[0027] A speed change rate calculation module, which is used to calculate the motor speed from the encoder position angle;

[0028] A current change rate calculation module is used to calculate the rate of increase of the comprehensive vector value of the three-phase current of the motor.

[0029] The combined condition judgment module is used to quickly determine encoder faults online based on the output data from the magnetic flux position error calculation module, the speed change rate calculation module, and the current change rate calculation module.

[0030] As a further aspect of the present invention: the flux linkage position error calculation module includes a flux linkage observer estimation module and an encoder sampling calculation module;

[0031] The flux linkage observer estimation module is used to estimate the flux linkage angle;

[0032] The encoder sampling and calculation module is used to calculate the flux linkage angle based on the rotor angle obtained by the encoder.

[0033] As a further aspect of the present invention, it also includes a motor vector controller, which is electrically connected to the combination condition judgment module;

[0034] The motor vector controller is used to receive judgment data from the combined condition judgment module and switch between the elevator's closed-loop vector control (FVC) mode and open-loop vector control (SVC) mode.

[0035] As a further aspect of the present invention, it also includes a motor, and by processing the three-phase current of the motor, the flux linkage position is estimated using a hybrid flux linkage estimation model that combines the motor voltage model and the current model.

[0036] As a further aspect of the present invention: if the motor is a synchronous motor, the flux linkage position angle is the same as the rotor's magnetic pole angle. If the motor is a synchronous motor, the flux linkage position angle is the same as the rotor's magnetic pole angle. The flux linkage position angle calculated by the encoder can be directly obtained by the encoder.

[0037] The beneficial effects of this invention are as follows: This invention can quickly and accurately identify all fault types of all encoders, and the judgment time can be reduced to the millisecond level. Once an encoder fault occurs, the elevator can immediately switch from closed-loop vector control (FVC) to open-loop vector control (SVC) online without stopping, and stop after running to the nearest floor door zone. Passengers in the car will not feel any sudden stop of the elevator. At the same time, it can prevent elevator runaway, inverter overcurrent and other faults after encoder failure, as well as corresponding entrapment events. Attached Figure Description

[0038] The invention will now be further described with reference to the accompanying drawings.

[0039] Figure 1 This is a block diagram of the encoder fault judgment logic of the present invention.

[0040] Figure 2 This is the magnetic flux observer model of the present invention.

[0041] Figure 3 This is a flowchart of the combinational logic judgment of the present invention.

[0042] In the diagram: 1. Magnetic flux position error calculation module; 101. Magnetic flux observer estimation module; 102. Encoder sampling calculation module; 2. Velocity change rate calculation module; 3. Current change rate calculation module; 4. Combination condition judgment module; 5. Motor vector controller; 6. Motor; 7. Encoder. Detailed Implementation

[0043] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] This invention provides a method for rapid fault identification of elevator encoders, enabling online switching from closed-loop vector control (FVC) to open-loop vector control (SVC) under fault conditions.

[0045] Specifically, such as Figure 1 As shown, the encoder fault identification system includes: a magnetic flux position error calculation module 1, a speed change rate calculation module 2, and a current change rate calculation module 3;

[0046] The results calculated by the above modules are judged by the combination condition judgment module 4. When the results exceed the reasonable range, i.e., exceed the threshold, it can be judged that the encoder data acquisition is wrong. The judgment result is input to the motor vector controller 5, so as to perform the corresponding control mode switching process.

[0047] Specifically, the flux linkage position error calculation module 1 includes a flux linkage observer estimation module 101 and an encoder sampling calculation module 102. The flux linkage observer estimation module 101 estimates the flux linkage angle θ. r The encoder sampling calculation module 102 calculates the flux linkage angle θ1 from the rotor angle obtained from the encoder 7, and the flux linkage position error calculation module 1 calculates θ. r The error E between θ1 and θ1 θ When the error E θ If the combined condition judgment module 4 determines that the condition exceeds the set threshold Value1, condition A is triggered.

[0048] Here, when motor 6 is a synchronous motor, the flux linkage position angle is the rotor's magnetic pole angle. Therefore, angle θ1 can be completely calculated by the encoder 7 through sampling. The flux linkage angle θ1 estimated by the flux linkage observer estimation module 101 is... r To utilize a hybrid flux estimation model combining the voltage and current models of motor 6, the observer does not rely on encoder 7, but instead uses the motor's currents ia, ib, ic and voltages Ua, Ub, Uc to estimate the flux position.

[0049] In a specific embodiment, such as Figure 2 As shown, the design of the magnetic flux observer 101 in this embodiment is as follows:

[0050] By analyzing the three-phase current The samples were obtained through Clark 3-2 coordinate transformation. The rotor position angle calculated using the flux linkage observer 101 is used for... Transformation ;

[0051] Will Input into the current flux model The current flux linkage model is passed through The transformation yields the current flux linkage model. Quantity;

[0052] Furthermore, voltage models for different components With current models of different components The compensation amount is obtained by taking the difference and adjusting it with a PI controller. Input into voltage flux model In the middle, the stator flux linkage voltage model will be used. through Transformation ,use Obtain the rotor flux linkage model Then the rotor flux linkage model through coordinate transformation Then, the rotor position angle can be determined. ;

[0053] Among them, the above-mentioned as well as Coordinate transformations all utilize rotor position angles The angle is calculated entirely by the current and voltage model and compared with the rotor flux position angle θ1 collected by encoder 7. The reasonableness and duration of the error between the two are used to determine whether the encoder is in an abnormal state.

[0054] Here, the combined condition judgment module 4 judges when the error E θ Condition A is triggered when the set threshold Value1 is exceeded. The threshold Value1 is the allowable flux linkage angle deviation value. According to the vector control method, if the angle deviation exceeds 45 degrees, the actual current will be too large and the torque current will be too small. If it exceeds 90 degrees, the correct torque cannot be generated. If the threshold is too small, it is easy to cause malfunction. Preferably, Value1 is selected as 30 degrees here.

[0055] Condition A is the estimated rotor position angle. The deviation of the rotor flux linkage position angle θ1 acquired by the encoder from the set value may be due to encoder malfunction or an estimation error. Inaccurate; to avoid erroneous actions, the estimated value needs to be adjusted. Apply appropriate filtering and delay condition A to exclude estimated values. The possibility of inaccuracy is obvious. If the delay confirmation time is too long, the motor vector controller 5 may easily lead to overcurrent or stall if it continues to use the closed-loop vector control FVC mode in the case of encoder failure. Therefore, the delay trigger time T1 of condition A is set to 10ms. This time ensures the accuracy of encoder failure judgment and can guarantee online switching to open-loop vector control SVC without stopping the elevator.

[0056] As another way to judge encoder failure, the speed change rate calculation module 2 is used. During the actual normal operation of the elevator, the elevator's running speed curve and acceleration / deceleration values ​​are controlled. As a system with a large inertia, the speed change rate dv / dt, i.e., the acceleration / deceleration value, will not exceed a certain limit value. When the elevator's deceleration exceeds this limit value, and the elevator brake is not activated, the actual deceleration of the elevator cannot reach this value. The most likely cause is encoder failure. Therefore, the following principle is used to judge encoder failure: the absolute value of the motor speed calculated from the encoder position angle decreases and the rate of change exceeds the set threshold Value2, which is triggered and denoted as condition B.

[0057] Preferably, the threshold Value2 here is the allowable acceleration / deceleration (or angular acceleration / deceleration) value, which is twice the maximum deceleration in the deceleration curve when the elevator is running normally. When condition B is triggered, in order to prevent misjudgment, it is necessary to perform a delayed judgment. Similarly, the delay confirmation time of condition B is set to T1, that is, 10ms.

[0058] When either condition A or condition B is triggered individually, the delay confirmation time reaches 10ms. During this delay confirmation time, the FVC control mode is still in effect, but due to encoder failure, the motor is out of control. After 10ms, the system switches to SVC control mode, and passengers in the elevator car experience a noticeable jolt. It is necessary to further reduce this delay confirmation time. Using combined conditions can improve the accuracy of encoder failure judgment and shorten the delay confirmation time. That is, when conditions A and B are triggered simultaneously, the delay confirmation time is shortened to T2, where T1>T2. Preferably, T2 is 2ms. This ensures the accuracy of encoder failure judgment and reduces the jolt in the car when switching to SVC.

[0059] Considering that after an encoder failure, continuing closed-loop vector control (FVC) will inevitably be accompanied by an increase in motor current, the current change rate can be used as an auxiliary judgment condition. Set condition C: The current change rate calculation module 3 is triggered when the rate of increase of the comprehensive vector value of the three-phase current of the motor exceeds the set threshold Value3. When condition A and / or condition B are detected to be triggered, and condition C is triggered at the same time, the confidence of the encoder failure is further improved, and the required delay confirmation time is reduced accordingly. Typically, the delay confirmation time is half of the original time.

[0060] If conditions A and C are triggered simultaneously, the delay confirmation time will be reduced from the original T1 to T1 / 2, i.e., 5ms; if conditions A, B, and C are all triggered, the delay confirmation time will be reduced from the original T2 to T2 / 2, i.e. 1ms. In this case, because the judgment time is very short, the time from the encoder failure to the switch to SVC operation is only on the order of milliseconds, and passengers in the car can hardly feel the switching process.

[0061] The threshold Value3 is the maximum allowable rate of change of current. According to the acceleration / deceleration curve of the elevator, the acceleration will not change abruptly, and the acceleration torque (current) it provides will not change abruptly either. During normal operation of the elevator, the limit of the change of the effective value of current is that the change within 0.3s does not exceed the rated current of the motor (except when the motor is powered on and started). Preferably, considering the small malfunction and margin, Value3 is set to the value that the change of current within 0.1s does not exceed the rated current of the motor.

[0062] like Figure 3As shown, the flowchart of the combined condition judgment module 4 according to the above logic is shown. Through the combination of the above conditions, all fault forms of all encoders can be quickly and accurately judged. The judgment time can be reduced to the millisecond level. Once an encoder fault occurs, the elevator can immediately switch from closed-loop vector control (FVC) to open-loop vector control (SVC) without stopping. After running to the nearest floor door zone, it stops. Passengers in the car will not feel any sudden stop of the elevator. While reducing the discomfort of passengers in the car, it can prevent elevator runaway, inverter overcurrent and other faults after encoder failure, as well as corresponding entrapment events.

[0063] The foregoing has provided a detailed description of one embodiment of the present invention, but this description is merely a preferred embodiment and should not be construed as limiting the scope of the invention. All equivalent variations and modifications made within the scope of the claims of this invention should still fall within the patent coverage of this invention.

Claims

1. A method for fast recognition of elevator encoder failure, characterized in that, The application relates to an encoder fault judgment method and system for a closed-loop vector control (FVC) of an elevator. The method comprises: During the closed-loop vector control FVC, adding encoder fault judgment logic; Based on the following condition combinations: Condition A: a flux linkage position error calculation module, the error between the flux linkage position angle calculated by encoder sampling and the flux linkage position angle estimated by a flux linkage observer, when the error exceeds a set threshold Value1, triggering; Condition B: a speed change rate calculation module, the absolute value of the motor speed calculated by the encoder position angle, when the descending change rate exceeds a set threshold Value2, triggering; Condition C: a current change rate calculation module, the rising change rate of the amplitude of the comprehensive vector value of the three-phase current of the motor, when the rising change rate exceeds a set threshold Value3, triggering; 2. The method of claim 1, wherein, Through different condition combinations, different delay confirmation times are adopted, when the more conditions are triggered, the shorter the confirmation time is, and if the condition combination still remains in the triggered state after the confirmation time, the encoder is judged to be faulty. The different delay confirmation times comprise: If only condition A or condition B is triggered, the delay confirmation time is T1; If condition A and condition B are simultaneously triggered, the delay confirmation time is T2, wherein T1>T2; Wherein, T1 is 10 ms, T2 is 2 ms, and condition C is an auxiliary condition; 3. The method of claim 1, wherein, If condition C is triggered during the triggering process of the foregoing condition A or condition B, the required confirmation time is correspondingly reduced, and the delay confirmation time is half of T1 or T2. The flux linkage observer estimation module in the flux linkage position error calculation module is a hybrid flux linkage estimation model combined by a voltage model and a current model of the motor; 4. The method of claim 1, wherein, The flux linkage observer estimation module estimates the flux linkage position by using the current and voltage response of the motor, and compares the flux linkage position with the flux linkage position obtained by the encoder, so as to judge whether the encoder is in an abnormal state by the error between the two. After the encoder is faulty, the elevator is immediately switched from the closed-loop vector control FVC to the open-loop vector control SVC online without stopping; Wherein, the elevator stops after running to the nearest door area.

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