Search

DE-102012106581-B4 - System and procedure for controlling an actuator

DE102012106581B4DE 102012106581 B4DE102012106581 B4DE 102012106581B4DE-102012106581-B4

Abstract

Comprehensive actuator-sensor fusion system, at least one real sensor (108,212) connected to an actuator (104,205) and generating real sensor signals, generating at least one virtual sensor (110) virtual sensor signals that define an estimated position of the actuator, based on signals used to control the actuator (104, 205), and a processor for merging the real sensor signals and the virtual sensor signals in order to detect a failure of the actuator (104,205) and/or of at least one real sensor (108,212), wherein the processor is configured to collect periodic corrections and/or absolute values of the periodic corrections applied to the virtual sensor (110) and to compare the collected periodic corrections or absolute values of the periodic corrections with a limit in order to detect deterioration of the actuator (104,205) and/or the real sensor (108,212), and to apply a memory factor (k ff ) at predetermined time intervals (t ff ) to the accumulating periodic corrections or absolute values of the periodic corrections, such that the accumulating periodic corrections or absolute values of the periodic corrections are periodically reduced by a certain proportion of their current values.

Inventors

  • Fancis P. Mullin

Assignees

  • ABB SCHWEIZ AG

Dates

Publication Date
20260513
Application Date
20120720
Priority Date
20120626

Claims (8)

  1. A system for actuator-sensor fusion comprising at least one real sensor (108, 212) connected to an actuator (104, 205) and generating real sensor signals, at least one virtual sensor (110) generating virtual sensor signals that define an estimated position of the actuator based on signals used to control the actuator (104, 205), and a processor for fusion of the real sensor signals and the virtual sensor signals to detect a failure of the actuator (104, 205) and/or the at least one real sensor (108, 212), wherein the processor is configured to collect periodic corrections and/or absolute values of the periodic corrections applied to the virtual sensor (110) and to compare the collected periodic corrections or absolute values of the periodic corrections with a limit to detect deterioration of the actuator (104, 205) and/or the real sensor. (108,212) to determine, and to apply a memory factor (k ff ) at predetermined time intervals (t ff ) to the accumulating periodic corrections or absolute values of the periodic corrections, so that the accumulating periodic corrections or absolute values of the periodic corrections are periodically reduced by a certain proportion of their present values.
  2. System according to Claim 1 , characterized in that the processor is configured to return to operation of the actuator (104,205) using the at least one virtual sensor (110) after a detected failure of the at least one real sensor (108,212).
  3. System according to Claim 1 or 2 , characterized in that the processor models the at least one virtual sensor and collects historical tracking data representative of control signals sent to the actuator (104,205).
  4. System according to one of the preceding claims, characterized in that the processor is configured to fuse the real sensor signals and the virtual sensor signals by comparing a position of the actuator (104, 205) indicated by the real sensor signals and a position of the actuator (104, 205) indicated by the virtual sensor signals in order to detect a difference in the displayed position of the actuator (104, 205) and to indicate a failure of the actuator (104, 205) and/or of the at least one real sensor (108, 212) due to exceeding a difference limit by the difference in the displayed position.
  5. Actuator-sensor fusion method, the method comprising: monitoring at least one real sensor (108,212) connected to an actuator (104,205) using a processor to generate real sensor signals that indicate a detected position of the actuator, monitoring at least one virtual sensor (110) using a processor to generate virtual sensor signals that define an estimated position of the actuator, fusing the real sensor signals and the virtual sensor signals using a processor to detect a failure of the actuator (104, 205) and/or the at least one real sensor (108, 212), collecting periodic corrections applied to the virtual sensor (110) and comparing the collected periodic corrections and/or the absolute values of the periodic corrections with a limit to detect deterioration of the actuator (104, 205) and/or the at least one real sensor (108, 212), and applying a memory factor (k ff ) at predetermined time intervals (t ff ) to the accumulating periodic corrections or absolute values of the periodic corrections, such that the accumulating periodic corrections or The absolute values of the periodic corrections are periodically reduced by a certain proportion of their current values.
  6. Procedure according to Claim 5 , furthermore, encompassing a return to the operation of the actuator (104,205) using the at least one virtual sensor (110) after a detected failure of the at least one real sensor (108,212).
  7. Procedure according to Claim 5 or 6 , furthermore, encompassing a modeling of at least one virtual sensor and a collection of historical tracking data representative of control signals sent to the actuator (104,205).
  8. Procedure according to one of the Claims 5 until 7 , wherein the fusion of the real sensor signals and the virtual sensor signals comprises: comparing a position of the actuator (104,205) indicated by the real sensor signals and a position of the actuator indicated by the virtual sensor signals, determining a difference in the indicated position of the actuator (104,205) and indicating a failure of the actuator (104,205) and/or of the at least one real sensor (108,212) due to the difference in the indicated position exceeding a difference limit.

Description

The present invention relates generally to actuators used in control processes in production plants. It relates in particular to a system and a method for controlling an actuator, wherein the positioning of actuators and the validation of the actuator's position sensor are controlled by combining or merging data from physical or real sensors with data from virtual sensors, both of which are used to monitor the actuators. While it is obvious that the approach of the present invention can be used in a wide variety of applications, the invention is described here with reference to actuators used in papermaking machines, for which the invention was developed and initially used. Systems with feedback control are known from the prior art as a means of controlling process variables in production facilities, for example, to position an actuator in a desired position. Feedback mechanisms and control algorithms are used to reduce a detected error signal to a minimum value. However, the prerequisite for control is that the feedback position is that of a fault-free state. DE 101 37 597 A1 describes a method for fault diagnosis on a clutch actuator. If sensors are used to monitor actuators, they are typically single-element feedback devices. Such sensors are capable of providing good feedback under either dynamic or near-static conditions, but usually not both. The level of precision and accuracy required for such sensors, especially those suitable for broadband operation, often exceeds what is commercially available at a practical cost for use in industrial control applications. If actuator sensors suddenly fail, the failures are generally simply detected, with the unfortunate result that the feedback from the failed sensor is completely unusable. Under these circumstances, the only course of action is to avoid any further action to control the actuator in order to prevent potentially catastrophic or permanent damage to system components, which would severely disrupt the operation of the machine in which the actuators are used. If the sensor's noise level is close to the signal level required for control, closed-loop control systems can introduce fluctuations into the controlled process. This phenomenon has been observed in papermaking machines, particularly with sensitive headbox control systems. The current solution to such fluctuation problems is to widen the dead zone, which reduces control accuracy and leads to shorter process response times. It has also been observed that very slow-developing drifts or errors, such as those emitted by progressively deteriorating sensor hardware, can be masked within the closed control loop, a typical characteristic of actuators with control systems. Such masked drifts or errors can render the control mechanism and/or typical alarm structures completely useless. A system and method for improved actuator control creates hybrid, soft, or smart sensors by merging information generated by at least one physical or real sensor with information generated by at least one virtual sensor. Virtual sampling can be performed by accumulating control signals and/or the absolute values of the control signals applied to an actuator, for example, by counting steps applied to a stepper motor, to effectively integrate the control signals and/or their absolute values. The accumulated control signals are converted into a corresponding position where the actuator would be based on the accumulated control signals. The resulting virtual position of the actuator, estimated as accurately as possible, is used together with the physically detected position of the actuator, estimated as accurately as possible, by the real sensor to form the hybrid, soft, or smart sensor. In this context, the terms "fused", "merge" or "fusion" refer to the use or combination of signals to form the hybrid sensor. The accumulating control signals can be subjected to minor periodic corrections to maintain or achieve a correlation between the virtual sensor and the real sensor over time, if possible. These corrections gradually reduce errors in the actuator position indicated by the virtual sensor. To mitigate accumulating numerical errors in the accumulating control signals and also to reduce the significance of events that occurred long ago, a displacement factor (k <sub>ff </sub>) can be applied at fixed time intervals (t<sub>ff</sub> ), thus reducing the accumulating control signals by a certain proportion of their current values. According to one aspect of the teachings of the present application, a system for merging a sensor for an actuator comprises at least one real sensor connected to an actuator and generating real sensor signals, and at least one virtual sensor generating virtual sensor signals based on signals used to control the actuator. A processor merges the real sensor signals and the virtual sensor signals to detect a malfunction of the actuator and/or the at least one real sensor. The processor can be configured