Method for monitoring the fail-safe function of a sensor in an electric motor

Abstract

The invention relates to a system and a method for monitoring the fault-free function of at least one first rotational speed sensor (S1) and one second rotational speed sensor (S2) on an electric machine (M), in a particularly redundant and diverse manner, wherein the number of revolutions (n) is used to accurately determine and monitor the rotor position, and wherein: a first product (P 2 ) of a first current count value (Z1) of a first output signal (A1) of the first sensor (S1) and a maximum count value (Z2max) of the second output signal (A2) is formed. a ) and forms a second product (P ) of a second current count value (Z2) of a second output signal (A2) of a second sensor (S2) and a maximum count value (Z1max) of a first output signal (A1) b ), and ‑loops checking two products (P a ,P b ) are equal and, if the check is negative, a fault message (F) is generated. This results in the positions of the two sensors in a common value system and they can be directly compared with one another. The rotor position can therefore be determined and monitored precisely.

Description

Technical Field

[0001] The invention relates to a method for monitoring the fault-free function of at least one first sensor and one second sensor, the two sensors operating independently of one another, the two sensors being operated to determine the rotational speed of an electric machine, the rotational speed in turn being used to determine the rotor position of the electric machine in a fail-safe manner, the first sensor providing a first output signal and the second sensor providing a second output signal.

[0002] The present invention also relates to a servo drive system, comprising a motor, a first sensor, a second sensor, and an automation controller, the automation controller having a user program, wherein the user program is designed to perform fault-free function monitoring of the first sensor and the second sensor, wherein the two sensors are designed to determine the rotational speed of the motor, wherein the rotational speed is in turn used to determine the rotor position in a fault-proof manner, wherein the first sensor provides a first output signal and the second sensor provides a second output signal. Background Art

[0003] The demands on motion control tasks in automation technology are increasing, becoming more diverse and complex. Siemens AG currently has the servo drive system "SIMATIC Micro-Drive" available on the market, which provides a perfect digital entry. Especially in safety-related applications, the speed, motor current, and torque of the motor used must be monitored. It must meet safety functions such as STO, SS1, SLT, SLS, and SSM. The above safety functions are specified in IEC61508 and IEC 13849. In addition, SIL2 and Cat.3 levels are also mentioned.

[0004] In order to limit the torque or reliably determine the rotor position, speed monitoring is required. With such monitoring, the speed is monitored by comparing two sensors with each other. In the known device "Automatic Door Control System Manual (SystemhandbuchAutomatische Türsteuerung), SIDOOR ATE530S COATed / ATE531S COATED / ATE531S, Edition 11 / 2019", the following monitoring is used to determine the safe rotor position: The actual speed is compared with the speed of the corresponding motor calculated using the fundamental model. In addition, synchronization messages are exchanged regularly with the pulse speed meter. The algorithm ensures that the speed of the sensor is also monitored (in addition to the function) by the mathematical model of the motor, so that angle and speed faults can be identified.

[0005] The problem with traditional monitoring methods is that usually the two sensors work in different reference systems and cannot be easily compared to each other. For example, an incremental encoder usually has 100 strokes per revolution, which results in 400 edges per revolution with four scans, while a Hall encoder has, for example, 6 segments per electrical revolution. Therefore a motor with two pairs of poles will have 2x6 segments and thus 12 segment changes per mechanical revolution.

[0006] EP 0 742 505 A2 discloses a device for safety-related monitoring of a shaft of a machine, in which two incremental encoder systems determine the rotor position and compare their magnitudes with one another in order to detect faults.

[0007] DE 10 2010 053 098 A1 discloses a method for monitoring a rotor position encoder having two sensors, namely a motor current sensor and a rotational speed sensor, wherein a fault is inferred from the magnitudes thus measured.

[0008] DE 10 2006 046 286 A1 discloses a method for a movement monitoring motor, in which the movement of the motor is safely monitored via two redundant rotational speed sensors. Summary of the invention

[0009] The object of the present invention is to provide a method which is not as complex as the known methods and which is also relatively fast, ie the method must be easy to implement in a program.

[0010] This object is achieved by a method having the feature combination of the invention.

[0011] The invention is based on converting the input information of usually two different sensors (of a variety) into an abstract value system that is common to both sensors or signals. For example, if there is an incremental encoder for the first sensor on the one hand and a Hall encoder for the second sensor on the other hand, the instantaneous value of the first sensor can be multiplied by the counting range of the second sensor and the instantaneous value of the second sensor can be multiplied by the counting range of the first sensor, thereby obtaining the positions of both sensors in a common value system and being able to compare them directly with one another.

[0012] Preferably, the maximum count value is determined during initial commissioning using an initialization run, which means that the motor is driven so that it performs exactly one revolution and the rotation pulses or step changes of a full revolution are counted in the associated computing unit.

[0013] Furthermore, it is advantageous if, after the fault message has been triggered, a further check is carried out to determine whether counting pulses cannot be achieved during an adjustable time period when an incremental encoder is used as the first sensor, or whether a stepwise change cannot be achieved when a Hall sensor is used as the second sensor, and if the check result is positive, a message is generated regarding a sensor wire failure or a sensor failure.

[0014] In order to specifically identify sporadic errors, the first product and the second product are each continuously accumulated in the first infinite counter or the second infinite counter, and the first infinite counter is periodically checked to see if it is equal to the second infinite counter. If it is determined that they are not equal, a fault message about sporadic interference is output. This embodiment has the following advantages.

[0015] A simple implementation, no longer needs to record individual Hall sectors precisely, reversal of direction and retention of direction no longer work, complete failure of individual lines or sensors is immediately identified, intermittent interruptions or short circuits can be noticed by the difference in the infinite counter and are identified when the limit value is exceeded, individual missing lines or Hall sectors distort the infinite counter and are identified when the limit value is exceeded. The significant advantage of infinite counting is that practically all faults can be manifested in the damage of the rigid coupling of the sensor, which in turn also distorts the infinite sum. Therefore, for the identification of faults, considering the infinite counter or infinite sum is the ideal method.

[0016] In order to derive a common value system, the first output signal is standardized according to the method to the common value system, thereby providing a first standard value, and the second output signal of the second sensor is also standardized to the same value system, thereby providing a second standard value, wherein the standard value is cyclically formed with the aid of a first quotient of a first current count value of the first output signal and a first maximum count value of the first output signal and a second quotient of a second current count value of the second output signal and a second maximum count value of the second output signal.

[0017] The above-described method steps are preferably executed in a user program of the automation controller.

[0018] Furthermore, in this method, the motor is supplied with energy via a converter which is in turn controlled by an automation controller. A safe rotor position is an essential basis for determining a given motor torque and thus a safe force output. In order to ensure this safety, a fail-safe determination of the rotor position is necessary.

[0019] The above method steps describe the precise determination and monitoring of the rotor position.

[0020] The object is also achieved by a servo drive system, which includes a motor, a first sensor, a second sensor, and an automation controller, wherein the automation controller has a user program, wherein the user program is configured to perform a monitoring of the fault-free function of the first sensor and the second sensor, wherein both sensors are designed to determine the rotational speed of the motor, wherein the rotational speed is in turn used to determine the rotor position of the motor in a fault-proof manner, wherein the first sensor provides a first output signal and the second sensor provides a second output signal, and the user program executes the method according to the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings illustrate an embodiment of the present invention. In the drawings:

[0022] Figure 1 A flowchart of the method is shown, and

[0023] Figure 2 A servo drive system is shown. DETAILED DESCRIPTION

[0024] Figure 1 A flowchart 20 of the method according to the invention is shown. At the beginning of the program, in the initialization phase 21, the counting pulses Z i It is read by the first sensor S1, and the step-by-step change S i is read in by the second sensor S2. In an initialization phase 21, the motor M is controlled by program technology so that it performs exactly one revolution, so that a maximum count pulse can be obtained for the first maximum count value Z1max of the first sensor S1 and for the second maximum count value Z2max of the second sensor S2.

[0025] In a further method step, namely count value reading 22, count pulses Z of the first counter Z1 or of the second sensor S2 are read in cyclically. i Or segmented change S i , and hereby forms a first product P of the first current count value Z1 of the first output signal A1 and the maximum count value Z2max of the second output signal A2 a , and also forms a second product P of the second current count value Z2 of the second output signal A2 and the maximum count value Z1max of the first output signal A1 b In the program section equality check 23, the first product P is checked cyclically. a and the second product P b If the check result is negative, a fault message F is generated in the section output fault message 24.

[0026] In the additional section monitoring time start 25 , after the fault message F has been triggered, it can be further checked whether, during the adjustable time period t pDuring this time, when using an incremental encoder as the first sensor S1, the pulses Z are counted i Is it not possible, or is it possible to change S in stages when using a Hall sensor as the second sensor S2? i If the check is positive, a sensor wire failure or sensor failure message SLA is generated.

[0027] In program section addition 26, the first product P is added a The first infinite counter EZ1 is formed by cyclic addition, and the second infinite counter EZ2 is formed by cyclic addition of the second product PD. Then, in a further equality check 27, it is periodically checked whether the first infinite counter EZ1 is equal to the second infinite counter EZ2, and if it is determined that it is not equal, a fault message about the sporadic interference SPO is output.

[0028] In order to derive a common value system, in a standardization step 22a, a first standard value υ1 is formed, i.e., a first quotient of a first current count value Z1 of a first output signal A1 and a first maximum count value Z1max of a first output signal A1, and a second standard value υ2 is formed, i.e., a second quotient of a second current count value Z2 of a second output signal A2 and a second maximum count value Z2max of a second output signal A2.

[0029] according to Figure 2 , shows a servo drive system μD. It includes a motor M, a first sensor S1, a second sensor S2, and an automation controller CPU with a user program AP. The user program AP is configured to perform a fault-free function monitoring of the first sensor S1 and the second sensor S2, wherein the two sensors S1, S2 are designed to obtain a rotational speed n of the motor M, wherein the rotational speed n is in turn used to determine the rotor position of the motor M in a fail-safe manner.

[0030] The first sensor S1 provides a first output signal A1 and the second sensor S2 provides a second output signal A2. The first sensor S1 and the second sensor S2 are integrated in the motor M. The plug-in leads ST are plugged in via the terminal box AK and they establish a connection between the converter UR and the motor M. The converter UR is coupled to the automation controller CPU via a communication line. The count pulses Z of the first sensor S1 are i is led to the automation controller CPU via the first sensor line SL1, and the segmented change S i The signal is passed from the converter UR via a second sensor line SL2 to the automation controller CPU.

[0031] The automation controller CPU has a user program AP in which it evaluates the first current count value Z1 and the second current count value Z2 according to the method. If a fault occurs during the counter evaluation, the automation controller CPU generates a fault message F or a message about a sensor line failure SLA or a fault message about a sporadic fault SPO by means of the user program AP.

Claims

1. A method for monitoring the fault-free function of at least one first sensor (S1) and one second sensor (S2), the first sensor and the second sensor operating independently of one another, wherein: The first sensor (S1) is operated as an incremental encoder to determine the rotational speed (n) of an electric motor (M), and the second sensor (S2) is operated as a Hall sensor to determine the rotational speed (n) of the electric motor (M), wherein the rotational speed (n) is in turn used to determine the rotor position of the electric motor (M) in a fail-safe manner, wherein the first sensor (S1) provides a first output signal (A1) as a read-in count pulse (Z i ) and the second sensor (S2) provides a second output signal (A2) as the read-in step change (S i ), It is characterized in that - the count pulses (Z) read in which form the first output signal (A1) i ) and a first product (P a ),and - the stepwise variation (S) of the read-in forming the second output signal (A2) i ) and the second product (P b ), wherein the maximum count values ​​(Z1max, Z2max) are determined during initial commissioning using an initialization run, wherein the motor is driven such that it performs exactly one revolution, and - Loop to check two products (P a , P b ) are equal, and - If the result of the check is negative, a fault message (F) is generated.

2. The method according to claim 1, wherein: After the fault message (F) is triggered, a further check is performed: within an adjustable time period (t P ), when using an incremental encoder as the first sensor (S1), the counting pulse (Z i ) is not possible, or when a Hall sensor is used as the second sensor (S2), the stepwise change (S i ) cannot be achieved, and if the check result is positive, a sensor wire failure or sensor failure message (SLA) is generated.

3. The method according to claim 1 or 2, wherein: The first product (P a ) and the second product (P b ) are respectively continuously accumulated in a first infinite counter or a second infinite counter (EZ1, EZ2), and the first infinite counter (EZ1) is periodically checked to see whether it is equal to the second infinite counter (EZ2), and if it is determined that they are not equal, fault information about sporadic interference (SPO) is output.

4. The method according to any one of claims 1 to 3, wherein: Provide a first standard value (υ1) and a second standard value (υ2), wherein by - a first quotient of the first current count value (Z1) of the first output signal (A1) and a first maximum count value (Z1max) of the first output signal (A1); and - a second quotient of the second current count value (Z2) of the second output signal (A2) and a second maximum count value (Z2max) of the second output signal (A2) cyclically forms a standard value (υ1, υ2).

5. The method according to any one of claims 1 to 4, wherein: The steps of the method are executed in a user program (AP) of an automation controller (CPU).

6. The method according to claim 5, wherein: A converter (UR) supplies energy to the motor (M) and is in turn controlled by the automation controller (CPU).

7. A servo drive system (μD), comprising: Motor (M), The first sensor (S1), The second sensor (S2), Automation controller (CPU), The automation controller has a user program (AP), wherein the user program (AP) is configured to perform a monitoring of the fault-free function of the first sensor (S1) and the second sensor (S2), wherein the two sensors (S1, S2) are designed to determine the rotational speed (n) of the motor (M), wherein the rotational speed (n) is in turn used to determine the rotor position of the motor (M) in a fail-safe manner, wherein the first sensor (S1) provides a first output signal (A1) and the second sensor (2) provides a second output signal (A2), It is characterized in that the user program (AP) is configured to execute the method according to any one of claims 1 to 6.

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