Factory automation and overall efficiency justifiably receive a lot of focus, not only for the upside benefit realizable from even small increases in output, but also from the equally important potential to reduce or eliminate the severe costs of equipment downtime.
Rather than rely on advancements in the discernment of available statistical data to predict maintenance needs or simply on better-trained technicians, true real-time analysis and control through advances in sensing and wireless transmission is now possible.
Accurate processes are progressively dependent on the effective and reliable function of motors and related machinery. Inequity, faults, movable fixtures, and other irregularities in the equipment classically render into a tremor, which then reduces accuracy and safety.
When these issues are not addressed, there can be performance, safety and productivity problems. Even minor changes in apparatus rapidly interpret into gaugeable misplaced efficiency.
Procedure measurement and condition-based projective preservation are well-established methods for evading efficiency loss, however, they are complex. Current methods have limits, chiefly when it comes to monitoring the vibration statistics and detecting sources of error.
Figure 1: Automation of Process Control and Maintenance Within a Factory Setting; High Value Target for Wireless Sensing Networks.
Usual methods for the collection of data include mounted piezo-based sensors and handheld data collection tools. However, numerous limitations are associated with these processes especially when contrasted with the idyllic resolution of a whole recognition and examination system that can be entrenched on or in the machinery and act independently.
The examination of options in the direction of establishing a completely entrenched and self-sufficient sensing component can be fragmented into ten distinct issues, including making very repeatable measurements, precisely measuring the seized data, and appropriate certification and traceability.
Accurate and Repeatable Measurement
Current handheld tremor probes offer some application benefits, such as not necessitating any alteration to the end apparatus and the fact that they are comparatively highly combined, which, assuming their huge (brick) scope, permits adequate processing and storage.
However, one chief restraint is the absence of repeatability of the dimensions. Minor changes in the probe site will yield unreliable vibration outlines, making time comparisons imprecise. Thus, it is hard to assess if the observed vibration change is due to a genuine modification within the equipment, or just a variation in the measurement method.
Preferably, the sensor would be both dense and combined adequately to permit direct and enduring entrenching within the apparatus of attention, thus eradicating any apprehensions of measurement site modification.
Figure 2: Existing Manual Probe Methods for Equipment Vibration Shift Monitoring Lack Repeatability and Reliability.
Frequency and Scheduling of Measurements
Process monitoring is predominantly valuable in a manufacturing facility for expensive equipment, for instance, of the creation of sensitive electronic components. Small shifts in an assembly line, in this case, can lead to reductions in factor output and to end equipment critical specification shifts.
A clear restraint of the handheld probe method is the absence of real-time notice of bothersome tremor changes. The equivalent is factual for the majority of piezo-based devices, which are usually not integrated (transducer only in some cases), and send the data away for future examination. These instruments necessitate exterior interference and thus enable shifts to be missed. Alternatively, an independent sensor processing arrangement, which comprises a sensor, analysis, storage, and alarm capability, whilst remaining small enough for implanting, allows fast notification of vibration changes and classification of trends.
Understanding the Data
Present warning from an implanted sensor is only conceivable if incidence domain examination is utilized. Any given apparatus classically has several sources of tremor (bearing defects, imbalance, gear mesh). A complex waveform can be established from a time-based analysis, but this does not provide discernible information before FFT analysis.
However, by embedding the FFT analysis within the sensor, the user can be immediately notified of vibrational shifts, reducing product development time by up to 12 months.
Data Access and Transmission
While implanted sensing is idyllic to attain precise and real-time trend data, this does obscure the mission of transporting data to a distant process controller. Entrenched FFT analysis also noticeably presumes that the analog sensor data has been accustomed to and transformed to digital to allow basic data transmission.
However, most vibration sensor solutions are limited to analog output, leading to signal degradation during the broadcast. As the majority of industrial equipment which needs vibration monitoring occurs in loud, motile, unreachable, hazardous environments, there is an intense need to lessen the intricacy of interface wiring and to also undergo data analysis at the source to obtain the most precise depiction of the apparatus vibration. Wireless sensor nodes, therefore, enable immediate access and significantly simplify the distribution of the sensor system.
Numerous current sensor resolutions are lone axis piezo transducers, which provide no directionality data which limits full understanding of the apparatus tremor outline. The absence of direction means that low noise sensors are needed to allow the essential judgment. The accessibility of multiaxis MEMS-based sensors allows a substantial rise in the capability to segregate the tremor source.
Location and Distribution of Sensors
The placement of sensors is vital and also highly reliant on the type of apparatus, atmosphere, and equipment lifecycle. As probes are expensive, probe points are often limited to only one, making the location even more important.
Furthermore, this results in noteworthy further development time to establish the best placement or limits in the quantity and value of data. Integrated sensor probes can, therefore, allow the placement of numerous probes, reducing development time/cost.
Adaption to Life Cycle Shifts
While a handheld monitoring system approach can possibly be tailored to changes (periodicity, amount of data, etc.) over time, providing that same life cycle based customization in an embedded sensor needs upfront attention during the design and deployment to allow the required tunability.
The transducer element, regardless of technology, is, of course, important, but typically more critical is the sensor conditioning and processing wrapped around the transducer. The signal/sensor conditioning and processing is not only specific to the unique equipment, but also to the life cycle of the equipment.
This translates to several important considerations in the design of the sensor. First, earlier analog-to-digital conversion (at the sensor head, versus off equipment) allows for configuration/tuning in-system. The ideal sensor would provide a simple programmable interface that would simplify the equipment setup through quick baseline data capturing, programming of alarms, manipulation of filtering and experimentation with different sensor locations.
With existing simple sensors, to the extent that any of this is configurable at equipment setup, some compromise in sensor settings must be made to accommodate changes in maintenance concerns over the life of the equipment. For instance, should the sensor be configured for early life, when equipment faults are less likely; or end of life, when faults are not only likely but potentially more detrimental?
The preferred approach is an in-system programmable sensor that allows configurability to changes in life cycle. For instance, relatively infrequent monitoring (for lowest power consumption) during early life, followed by reconfiguration to frequent (user programmed period) monitoring once a shift (warning threshold) has been observed, in addition to the continuous monitoring for, and interrupt-driven notification of, user programmed alarm thresholds.
Identification of Performance Shifts/Trends
Acclimatizing the instrument to variations in apparatus life cycle relies on an understanding of baseline equipment response. Basic analog sensors can permit this, if the operator takes measurements, does an analysis offline, and stockpiles this data offline, correctly marked to the exact equipment and probe site. Baseline FFT stowage at the sensor head eliminates potentially misdirected data.
Data Traceability and Documentation
A proper vibration investigation program may analyze 100s of locations by either a handheld probe or entrenched sensor. Thousands of records may, therefore, be obtained, requiring appropriate location and time mapping. To ensure accuracy, the sensor should, therefore, have an exclusive serial number and embedded storage.
Many current transducers, such as piezo-based, have no in-system self-test, reducing assurance in the reliability of data. However, self-testing is possible with some MEMS-based sensors, as they have an entrenched digital self-test competence.
Analog Devices ADIS16229 is capable of all of the benefits outlined in the ten vital concerns discussed, featuring a 512-point real value FFT, an embedded frequency domain processing and storage to allow the identification of vibrational sources over time. The device allows configurable spectral alarm bands and windowing selections.
Figure 3: MEMS-Based Sensor Node (ADIS16229) with 928 MHz RF Link to Gateway Controller (ADIS16000).
Figure 4: Six Remote Sensor Nodes Autonomously Detect/Collect/Process Data and Wirelessly Transmit to a Central Controller Node.
The MEMS sensor delivers a self-test mode to deliver unceasing assurance in functionality and data integrity. The device is fully entrenched and computerized, allowing situation close to the vibration cause and initial detection of minor signals, evading data inconsistencies due to alterations in location/coupling.
An 862 MHz/928 MHz exclusive wireless protocol interface permits the sensor node to be remotely situated and maintained by a distinct gateway node which delivers a typical SPI interface to any system controller device.
These sensors can enable a more universal distribution of vibration sensing by minimizing the barricades to the implementation of this critical tool, which formerly was restricted to a minority of highly skilled engineers with years of analytical knowledge. Such fully combined sensors offer the chance for radically lower maintenance costs.
This information has been sourced, reviewed and adapted from materials provided by Mouser Electronics.
For more information on this source, please visit Mouser Electronics.