Limitless Measurement, Drive Systems and Machine Controllers
Optimal MSR Solutions
Every machine gives individual demands to its measurement, drive and machine controllers systems. Often, standard solutions only fit halfway and frequently the machine’s possibilities are reduced to the one’s of commercial devices. But this reduces the opportunities of the market! Application specific measurement, drive and machine controllers solutions are often cheaper and better than standard products.
Switzerland has a strong industry and a diverse trade: precision instruments, top technology in measuring systems, specialized mechanical engineering, etc. Despite high price levels, our products are in demand worldwide because Swiss technology is known for its excellent quality. This is our strength and perhaps our most important competence in the future.
Quality means that a product is better than it needs to be – better than the competition. However, quality also includes those features that go beyond the elementary target function of the product and in some cases generate a considerable additional benefit. Today, these are often network functionalities (for example capacitive touch screens), adaptive functions (for example in control technology), etc. However, these are superficial features. Of course, it is also about the core of the product. Today, for example, it is expected that even highly dynamic drives start up smoothly, that measuring systems provide static values in addition to the actual measured value, which, for example, provide information about measurement uncertainties or measurement errors, that control loops quickly and accurately compensate for setpoint changes or disturbances, and so on.
Many manufacturers use standard products for measurement, control and regulation (MCR) in their systems, for example a PLC (Programmable Logic Controller). These are relatively expensive and limited in functionality, but often do the job well enough. But what do you do if the results are not satisfactory, if the measurement takes too long or is too inaccurate, if the motor control does not achieve the required dynamics or reaction speed, if the controller either settles too slowly or tends to instability? One solution is to get the next most expensive standard instrument and try it with that. Or just: You have an application-specific solution developed. Although this causes a not inconsiderable initial outlay, in the end it is significantly cheaper per device than the standard product and solves the measurement, control and/or regulation problem in the desired optimum quality. The company Stettbacher Signal Processing AG (SSP) in Dübendorf near Zurich develops exactly such systems. It specializes in electronic measurement, machine control and drive systems technology, as well as all relevant technologies for the integration. Their customers often are companies that previously failed with standard solutions.
Here are some examples:
- A customer requires a measuring system with 16 measuring channels that sample exactly synchronously in time and deliver 500,000 measured values per second per channel. Certain patterns are to be searched for in these data streams, and if they occur, the signal section containing the pattern is to be delivered to a higher-level computer. Picture 1 shows the core of the solution developed by SSP. The circuit board is compact, double-sided, and meets mil-spec requirements. It contains analog signal conditioning and AD converters for 16 channels, signal analysis in an FPGA, and a computer module for post-processing, device control and communication via Ethernet.
- A customer builds installations with many coupled drives that work synchronously but execute different movements. A control clock of 14 kHz was required, independent of the number of drives, as well as inputs with 24 bit resolution for up to 12 industrial sensors, which can be used individually or in combination to form the feedback of the control loop. SSP designed a modular system for this purpose (Picture 2). Picture 3 shows a section of the specifically developed mainboard with power supplies and measurement circuits.
- A customer requires a drive system with special requirements for control technology and dynamics. For this purpose, SSP developed a server amplifier with a fast digital connection to the higher-level machine control. The drive system (Picture 4) has its own micro controller, which implements the current control loop including 3-phase current measurement and vector modulation for a synchronous motor of 1.5 kW. To comply with the standards on mains feedback, the server amplifier is equipped with a PFC (Power Factor Corrector).
- A customer orders a compact handheld measuring device that records series of measurements with several 1000 measuring points via an integrated sensor. The evaluation of the data is complex and uses, among other things, spectral transformations. SSP chooses a modern low-power micro controller, which is responsible for the entire device and power management, performs the measurements, handles the signal processing and finally controls an LCD display. Also, a battery controller is provided and a USB interface.
The practical examples illustrate that even unusual requirements far beyond the capabilities of standard devices can be met very well with application-specific solutions. All of the examples are also geared to quality and additional benefits, which, given the available hardware options, causes practically no additional costs. Also, the often expressed assumption that application-specific developments are only worthwhile with large quantities is not correct. Of some of the examples shown, not much more than ten units are produced per year. But what can be said for sure: If there were only standard MCR devices, the examples presented would never have found their way onto the market.