Intelligent drive

Translation of description of equivalent WO 2005124488 A1

Intelligent drive

The invention relates to electric actuators for controlling axes within technical processes according to the preamble of claim 1.

An electrical automation system or an electrical machine may include, among many almost wear-free electrical components and a large amount of wear-prone mechanical components such as gearboxes, timing belts, brakes and guides. It is primarily tries the increasing wear by monitoring the characteristic variables occurring during operation to prevent. From the prior art it is therefore known from measured values, which are derived from the instantaneous operating state of an electric drive, close to the mechanical load. For example, the temperature of the windings of an electric motor are used to detect a load increase and if necessary to limit the motor current on or off the drive. Error is detected by means of a limit value monitoring or a threshold monitoring.

The disadvantage of this method is that an exception is active only when the error has already occurred. This has the consequence that the underlying mechanical or electrical component may already have been stressed beyond the dimensions and thus the wear progresses rapidly with frequent repetition of the error.

The patents DE 196 14 748 C2 and DE 42 21 841 Cl deal with a failure diagnostic method and a monitoring control system for the monitoring of multiple devices. The latter document shows a control device for centralized monitoring and deviations of the operating data of the monitored devices are detected and processed. The former document discloses a relatively complex network with process computer node, diagnostic computers, control process computers and a variety of other peripherals for the treatment of errors, especially for use even with electric drive systems. Due to the complexity of both devices is quite complex and thus costly solutions arise.

The object of the invention is now to provide an inexpensive, decentralized, preventive fault diagnosis FTIR electric drives, the fault diagnosis is designed to ensure the early detection of an impending breakdown.

The invention relates to an electric drive with a controller, an electric motor and a control device with detection and monitoring of thresholds achsrelevanter, electrical / mechanical operating state variables from which the control device an additional monitoring with analysis of the operating state variables for the early detection of possible deviations from target values ​​and preparation of the analytical result includes. The analysis can be permanent and / or intermittently carried out depending on the operating state -untersuchter size.

The drive can be both a centralized and a decentralized eingebundener in a work process drive, which transfers to be driven axes by means of a translation or directly the torque of its output drive. The controller or drive amplifier may comprise the current, velocity or position control and an inverter or converter. The controller monitored with sensors, the threshold required for proper operation variables, such as the maximum permissible winding temperature and the maximum permissible speed.

The additional monitoring with permanent or intermittent analysis of the operating state variables for the early detection of possible deviations from target values ​​and preparation of the analytical result ensures an axis-specific error detection. This is not that a master controller (PLC, NC) performs the analysis, but the control device of the actuator itself. A transmission of high frequency changes Operating state variables by means of a limited bandwidth in the bus (eg fieldbus) is dispensed with, because now high-performance and low-cost CPUs are translated to realize the powerful controller directly in the drive. This Konfrolleinrichrung processes the amount of data immediately after their detection and forwards only the result of data analysis via a bus to the next higher instances on. This saves bandwidth on the one hand and relieves the CPU of the process control.

The fact that the additional monitoring (eg dazμ parallel) is active regardless of the Threshold, imminent faults themselves can already be detected before the threshold monitoring responds. It is thus ensured a pro-active monitoring, which can prevent a response of the threshold monitoring and an associated failure of the process through appropriate messages and related countermeasures. An early response by the operator or the controller, for example in bearing damage, decreased stiffness, increased friction, increased game, load fluctuations, sluggishness, terminals and dirt is thus possible. Of course, another drive-side or output-side electrical and / or mechanis be detected misstatements of the supplementary supervision. All measured values ​​are supplied to the analyzing apparatus and analyzed as needed.

For temporary, strong deviations of the detected movement state variables of the allowable values, the analysis means of additional monitoring may make a preliminary decision as to whether a response to the threshold monitoring is required or whether it is only a temporary and harmless for the assembly threshold being exceeded, for example by statistical methods. This reduces unnecessary downtime and reduces costly production downtime. The invention thus enables that largely all axis diagnostic operations are done locally in the drive. Machine-related diagnoses, however, can be performed in the control in consideration of the axis-related diagnostic messages.

captured by means of electrical signals from sensors operating state variables of a signal processing are preferably subjected, in particular by means of a signal filter before the Threshold. This avoids false alarms due to corrupted 'or interference-prone readings, which would recognize the Threshold as detected errors. The sensors may be sensors for detecting movement relevant conditions (acceleration, speed) but also of non-motion related conditions, such as structure-borne sound waves or static loads, act.

Particularly preferably, the detected by sensors electrical signals of the operating state variables in the time and / or frequency range are analyzed by the additional monitoring. analysis can be used to, inter alia, the FFT (Fast Fourier Transformation), KKF (cross-correlation function), AKF (auto-correlation function). An analysis such as the current value of a motor driving by a belt an axis, by transforming the current curve in the frequency domain by means of FFT, so can equenzen draw conclusions on newly forming resonant vibrations compared with reference values ​​due to changes in mechanical Resonanzf. This new resonance vibrations may be due to a decrease in belt tension, which is indicated to the operator accordingly. This averaging is performed for a long time before the belt can slip off or tear, so that an early error detection is assured in any case.

Most preferably, the target values ​​may be recorded by the drive and are stored in the drive as reference values. application-specific

Setpoints with detection of edge parameters as friction conditions, Translations by gear and tolerance bands for each operating parameters are thus be stored in the drive. Advancing wear of components can be prevented by comparing the actual values ​​with the reference values ​​in the time and / or frequency domain.

Quite extraordinarily Favour the analysis includes a long-term monitoring of operating state variables. In particular, long-term monitoring, including tolerance bands or limits. This avoids errors by brief load fluctuations. Statistical evaluations such as averaging, allowing an evaluation of the tendency curve of a measured variable, with error messages occur only when the tolerances are exceeded by the mean. A false alarm by to early response of the threshold monitoring can be avoided.

Conveniently the operating state variables associated error messages are generated. Thus, a clear conclusion on the cause of the error with a detailed error analysis and if necessary guarantees with instructions for error correction without it for evaluating the error description requires highly qualified personnel. A savings in personnel costs for operating personnel is in turn connected.

If it is the operation of state variables to movement-sizes, such as an angle parameter for detecting the Motorachslage, or the engine speed and / or indirectly with the movement related variables such as the amount of motor winding temperature, the size of the motor current or the amount of DC voltage is, then includes the analysis essentially only the evaluation of the already present in a carrier formed from servo motors drive system metrics. Thus, no additional sensors for detecting additional state data is required. From the measured value of the motor current in connection with the measured value for the engine speed, for example, to draw conclusions about an increased friction when driving a load can be drawn without additional sensors. With additional sensors such as strain gages, load cells, Borne sound sensors and accelerometers could be further enhance the diagnostic capabilities and ease of use when needed. If the analysis results included by means of a drive from or related to the drive control device (display device, with or without input device) are shown, then a decentralized error handling directly at the point of failure is possible. Using wireless interfaces can also portable displays or PDAs, laptops, etc. for fault indication and / or corrective action may be used. '₍

Advantageously, an inventive drive is integrated within at least a technical process, and communicates with at least one computer, wherein the drive means of a data bus or the field bus is connected to the computer and to this particular reports the analytical results.

This allows a choice between a decentralized and / or centralized error handling or a combination thereof. Multiple drives comprehensive, complex applications can thus be realized. A modular design is possible and the resulting clear topology facilitates handling and maintenance of the system. As data come all known in the art field buses in question also Fast Ethernet and SERCOS. Disorders relating to mechanical and electrical components of the drive should preferably be recorded, processed and evaluated in the drive itself. Disturbance to a driven by the drive device (such as a tool) should be collected and processed in the drive. Preferably, these disorders should be then evaluated by the controller, as necessary, the diagnostic results of several actuators are required for fault detection. The same applies to faults in conjunction with a precisely worked or processed by the process workpiece or object. Every time so if a failure affected several drives or could be caused by several drives, the computer (composite) should participate as a parent instance in the diagnosis. It can detect all error messages of all drives, analyze and maintain statistics and Troubleshooting Automatically Initiates inform the operating personnel.

If the drive is freely programmable and / or configurable, at least with respect to the error detection, this allows for flexible adaptation of the error detection to the operating environment or the application to be realized. Unused functions can be disabled in order to save processing power. The programming interface can be designed so that no passing internal Antjiebsstrukturen is necessary to the user, thus is the manufacturer's interest to have not pass internals safeguarded.

If the analysis results are available in the context of remote maintenance, this facilitates automatic monitoring of a process. Axis-specific error may be at additional transmission of a drive or axis address accessed, for example, and can be easily recognized due to the additional information. The same personnel are thus quickly and easily instructed and necessary spare parts can be ordered independently of a site visit.

LIST OF REFERENCE NUMBERS

Human / Machine Interface

(Central) Calculator

Report generation

guard

controller

additional monitoring

Limit / Threshold

Measured value acquisition

motor

drive

Below a device with the inventive solution based Figure 1 is shown. Figure 1 includes a human / machine interface 1, a computer / computer network 2, a message generation 3, a protective device 4, a controller 5, an additional monitor 6, a limit / Threshold 7, a data acquisition 8, a motor 9. Numerals 3-9 thereby form the drive 10, reference numerals 1 and 2 external components.

The electric drive 10 with the controller 5, the electric motor 9 and a Konfrolleinrichtung (3 to 8) can be used for example to control a ball screw of a machine tool. The control device comprises a to limit / Threshold 7 additional inventive monitoring 6. Both monitoring units 7, 6 are to be monitored readings of the measured value acquisition 8. Here, there, for example, measured values ​​for detecting the speed of the motor shaft to the impulses of an angle sensor, involve readings for detecting the motor current and to the measured winding temperature. The measured values ​​can be in analog and / or digital form. While confined to compliance with prescribed limits for limit / Threshold 7, an additional monitoring is 6 made, are being analyzed and interpreted the acquired measurements for early detection of possible deviations from target values ​​by permanent or intermittent analysis. This is followed by a detailed treatment of the analysis result, so that the cause of an impending failure, such as a loose drive belts, increased friction, bearing damage, excessive play, reduced stiffness, load fluctuations, sluggishness, terminals, soiling the mechanical axis system, bearing damage by the message generation 3 to the operating unit 1 and / or the controller 2 can be reported in the form of detailed error or Störunge Common Problems and / or warnings, so that an operator can initiate a fix without exact knowledge of the system. This is particularly true for the case that in addition are available for reporting nor represents what actions to take for troubleshooting. It would also be conceivable the components 1 and 2 to integrate into the drive, if the application is suitable and sufficient computing power and space available.

After the data acquisition 8 the sensed electrical signals to signal conditioning could be subjected to before, these are supplied, for example, the threshold monitoring. 7 This serves to short-term disturbances caused on the signal lines, for example, by strong magnetic fields, hide and avoid an error message when an associated threshold value is exceeded. Ultimately thereby unwanted process failures are avoided.

The additional monitoring 6 may be variously configured, so that the detected by sensors electrical signals of the operating state variables in the time and / or frequency range are analyzed. An analysis in the frequency domain could for example include Fast Fourier Transformation (FFT) to make unwanted resonance vibrations locate. Similarly, a car could correlation function (ACF) are used to determine the speed with which change the readings on average over time. Further analysis by means of mathematical methods, such as the setting up of a cross-correlation function (KKF) etc. are possible and only limited by the computing power in the drive.

The additional monitoring 6 will usually comprise a data memory, which is used for storing desired values, which are recorded by the drive, for example, during an initialization or homing phase with a real load as reference values ​​and can be used in the analysis as benchmarks.

Also, the analysis of the additional monitor 6 may comprise a long-term monitoring of the individual measured values. For example, the DC link voltage and the motor current could be used to calculate the average power.

Each metric or specific measured value combinations can be assigned error messages, which then contribute in the event of a detected fault troubleshooting.