System and Method for Monitoring a Failsafe Function of Sensors in a Motor

Abstract

A system and method for redundantly monitoring faultless functioning of first and second rotational speed sensors on an electric motor, where the rotational speed is to precisely determine and monitor a rotor position, where a first product is formed from a first current count of the first output signal of the first sensor and a maximum count of the second output signal, a second product is formed from a second current count of the second output signal of the second sensor and a maximum count of the first output signal, the two products are cyclically checked for equality and, in when the check is negative, an error message is generated, where the method provides the position of both sensors in a common values system and the positions can be directly compared with one another such that precise determination and monitoring of the rotor position becomes possible.

Claims

1.-8. (canceled)

9. A method for monitoring failsafe operation of at least one first and one second sensor, which operate independently of each other, the at least one first and second sensors being operated to ascertain a rotational speed of an electric motor, the rotational speed being subsequently utilized for failsafe rotor position determination of the electric motor, and the at least one first sensor supplying a first output signal and the second sensor suppling a second output signal, the method comprising: forming a first product of a first current count value of the first output signal and a maximum count value of the second output signal; forming a second product of a second current count value of the second output signal and a maximum count value of the first output signal; checking cyclically the first and second products for equality; and generating a fault indication when the check is negative.

10. The method as claimed in claim 9, wherein the maximum count values are ascertained with an initialization run during an initial operation.

11. The method as claimed in claim 9, wherein after triggering of the fault indication, the method further comprising: performing a check to determine whether, over an adjustable period with an incremental encoder as the first sensor, counting pulses or with a Hall sensor as the second sensor, segment changes fail to materialize; and generating an indication for a sensor cable failure or a sensor failure when the check is positive.

12. The method as claimed in claim 10, wherein after triggering of the fault indication, the method further comprising: performing a check to determine whether, over an adjustable period with an incremental encoder as the first sensor, counting pulses or with a Hall sensor as the second sensor, segment changes fail to materialize; and generating an indication for a sensor cable failure or a sensor failure when the check is positive.

13. The method as claimed in claim 9, wherein the first product and the second product are each added up continuously in a first or second endless counter and the first endless counter is periodically checked for equality with the second endless counter and, when an inequality is found, a fault indication of a sporadic malfunction is output.

14. The method as claimed in claim 10, wherein the first product and the second product are each added up continuously in a first or second endless counter and the first endless counter is periodically checked for equality with the second endless counter and, when an inequality is found, a fault indication of a sporadic malfunction is output.

15. The method as claimed in claim 11, wherein the first product and the second product are each added up continuously in a first or second endless counter and the first endless counter is periodically checked for equality with the second endless counter and, when an inequality is found, a fault indication of a sporadic malfunction is output.

16. The method as claimed in claim 9, wherein the first output signal is standardized to a shared value system to provide a first standard value and the second output signal of the second sensor is standardized to the shared value system to provide a second standard value; and wherein the first and second standard values are cyclically formed via (i) a first quotient of the first current count value of the first output signal and the first maximum count value of the first output signal and (ii) a second quotient of the second current count value of the second output signal and the second maximum count value of the second output signal.

17. The method as claimed in claim 10, wherein the first output signal is standardized to a shared value system to provide a first standard value and the second output signal of the second sensor is standardized to the shared value system to provide a second standard value; and wherein the first and second standard values are cyclically formed via (i) a first quotient of the first current count value of the first output signal and the first maximum count value of the first output signal and (ii) a second quotient of the second current count value of the second output signal and the second maximum count value of the second output signal.

18. The method as claimed in claim 11, wherein the first output signal is standardized to a shared value system to provide a first standard value and the second output signal of the second sensor is standardized to the shared value system to provide a second standard value; and wherein the first and second standard values are cyclically formed via (i) a first quotient of the first current count value of the first output signal and the first maximum count value of the first output signal and (ii) a second quotient of the second current count value of the second output signal and the second maximum count value of the second output signal.

19. The method as claimed in claim 12, wherein the first output signal is standardized to a shared value system to provide a first standard value and the second output signal of the second sensor is standardized to the shared value system to provide a second standard value; and wherein the first and second standard values are cyclically formed via (i) a first quotient of the first current count value of the first output signal and the first maximum count value of the first output signal and (ii) a second quotient of the second current count value of the second output signal and the second maximum count value of the second output signal.

20. The method as claimed in claim 9, wherein the method is executed in a user program of an automation controller.

21. The method as claimed in claim 20, wherein an inverter supplies the electric motor with energy and the inverter is in turn controlled by the automation controller.

22. A servo drive system comprising an electric motor; a first sensor; a second sensor; an automation controller including a user program which, when executed by the automation controller, performs monitoring of failsafe operation of the first sensor and the second sensor; wherein the first and second sensors are configured to ascertain a rotational speed of the electric motor, the rotational speed being subsequently utilized for failsafe rotor position determination of the electric motor; wherein the first sensor supplies a first output signal and the second sensor supplies a second output signal; and wherein the user program is configured to: form a first product of a first current count value of the first output signal and a maximum count value of the second output signal; form a second product of a second current count value of the second output signal and a maximum count value of the first output signal; cyclically check the first and second products for equality; and generate fault indication when the check is negative.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The drawings show one exemplary embodiment of the invention, in which:

[0024] FIG. 1 shows a program flowchart of the method in accordance with the invention; and

[0025] FIG. 2 shows a schematic illustration of a servo drive system in accordance with the invention.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

[0026] With reference to FIG. 1, a program flowchart 20 for the inventive method is illustrated. Commencing from a program start, in an initialization phase 21, the counting pulses Z.sub.i are read from the first sensor S1 and the segment changes S.sub.i are read from the second sensor S2. In the initialization phase 21, the motor M is actuated by programming such that the motor M executes exactly one rotation. As a result, the maximum counting pulses for a first maximum count value Z1max of the first sensor S1 and for a second maximum count value Z2max of the second sensor S2 are ascertained.

[0027] In a further method step, i.e., the counter value reading-in 22, the counting pulses Z.sub.i or the segment changes S.sub.i of the first counter Z1 or the second sensor S2 are cyclically read-in and a first product P.sub.a of a first current count value Z1 of the first output signal A1 and a maximum count value Z2max of the second output signal A2 is formed and furthermore, a second product P.sub.b of a second current count value Z2 of the second output signal A2 and a maximum count value Z1max of the first output signal A1 is formed. In the program segment: equality check 23 the first product P.sub.a is cyclically checked for equality with the second product P.sub.b and for the case where the check is negative, a fault indication F is generated in the output fault indication 24 segment.

[0028] In an additional segment: start of monitoring time 25, after triggering of the fault indication F a further check is made to determine whether, over an adjustable period t.sub.p with an incremental encoder as the first sensor S1, counting pulses Z.sub.i or with a Hall sensor as the second sensor S2, segment changes S.sub.i fail to materialize and, for the case where the check is positive, an indication SLA for a sensor cable failure or a sensor failure is generated.

[0029] In a program segment: adding up 26, a first endless counter EZ1 is formed by cyclically adding up the first product P.sub.a and a second endless counter EZ2 is formed by cyclically adding up the second product PD. In a further equality check 27, the first endless counter EZ1 is then periodically checked for equality with the second endless counter EZ2, and for the case where an inequality is found, a fault indication of a sporadic malfunction SPO is output.

[0030] In order to derive the shared value system, in a standardization step 22a a first standard value y1 is formed in that a first quotient of the first current count value Z1 of the first output signal A1 and the first maximum count value Zlmax of the first output signal A1 and a second standard value y1 is formed in that 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 is formed.

[0031] With reference to FIG. 2, a servo drive system μD is illustrated. The servo drive system μD comprises an electric motor M, a first sensor S1, a second sensor S2, an automation controller CPU with a user program AP. The user program AP is configured to monitor failsafe operation of the first sensor S1 and the second sensor S2, with the two sensors S1, S2 being configured to ascertain a rotational speed n of the electric motor M, with the rotational speed n in turn being used for failsafe rotor position determination in the case of the electric motor M.

[0032] The first sensor S1 supplies a first output signal A1 and the second sensor S2 supplies a second output signal A2. The first sensor S1 and the second sensor S2 are integrated in the motor M. A plug-in cable ST is plugged in via a terminal box AK and establishes the connection between an inverter UR and the electric motor M. The inverter UR is coupled via communication cables to the automation controller CPU. The counting pulses Z.sub.i of the first sensor S1 are conducted to the automation controller CPU via a first sensor cable SL1 and the segment changes S.sub.i are conducted from the inverter UR to the automation controller CPU via a second sensor cable SL2.

[0033] The automation controller CPU has a user program AP in which the first current count value Z1 and the second current count value Z2 are evaluated in accordance with the method. If faults should occur during the counter evaluation then, with the aid of the user program AP, the automation controller CPU generates a fault indication F or an indication of failure of the sensor cable SLA or a fault indication of a sporadic malfunction SPO.

[0034] Thus, while there have been shown, described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the methods described and the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.