Focus on Technology

Project Examples  

Our projects cover a broad range, from signal processing, control engineering, through algorithm development, hardware and software design, drive technology to system integration, embedded systems and industrial applications. Here are some examples from our daily practice.

Model Based Control  

Heat transfer

Project Definition

The surface temperature of a metal body is to be regulated in order to accurately and quickly follow a desired profile. The heater and temperature sensor are located at separate positions within the body. This causes a delay of the measurement , a so-called dead time.

Challenge

The control of processes with dead time is difficult. Conventional control structures (such as PID controllers) tend to overshoot or even become instable. A precise control is only possible if moving very slowly. Control accuracy and control speed are contradictory in this case.

Control loop

Solution

A numerical model of heat propagation in the body was inserted into the control loop. This so-called estimator or predictor calculates the surface temperature after a certain time, based on the actual temperature measurement and the heating current. Therefor the predictor can look into the future and thus bridges the dead time of the process.

Temerature curve

Result

By using the predictor the controller can predict the behavior of the process and thus responds without delay. The contradiction between control accuracy and control speed is dissolved. The surface temperature can be tracked accurately and quickly according to the desired profile.

The figure shows the predicted temperature (red), the measured value (blue) and the controller output (black). It is apparent that the controller reduces the heat output due to the predicted value as soon as the estimated temperature reaches the setpoint. Thus, the temperature will settle at the desired value very quickly and without disturbing overshoot.

Measuring System  

Project Definition

A measuring system shall capture up to 16 parallel channels with a sampling rate of 500 kHz at a 16 bit resolution. After that the captured data has to be processed and evaluated in real time. The customer also wanted a graphical display with touch screen for data visualization, ethernet and a web server for remote configuration of the system.

Challenge

A normal PC is not able to process these data in real time. Usually an array of specialized digital signal processors (DSPs) is used to meet the required sampling rate and data volume as well as the real-time processing specification. However, a typical DSP does not have interfaces nor support for ethernet, display and touch screen. Furthermore the use of a DSP requires its own tools and the corresponding expertise.

Solution

Instead of a DSP, a commercially available computer module was used. These modules are compact, inexpensive and have an exceptional processing power, depending on the type. An FPGA was used to automatically read from the ADC, perform the time-critical digital pre-processing in parallel threads and provide the data blockwise to the module, where they are further processed.

The hard real-time capability of the module is achieved through the use of Linux with a real-time extension, such as RTAI. In addition, Linux already includes complete ethernet capability, and a wide variety of support for display, touch screen, web servers, etc.

Result

Through the use of the computer module, hardware to be designed became much simpler. The module runs all software tasks, including signal processing, data visualization and the provision of webpages over ethernet. The software development under Linux was very efficient, because the operating system already provides lots of useful features and services like hardware abstraction, drivers, internal communication mechanisms, and many more.

The real-time extension makes it possible to cleanly isolate and prioritize the real-time system components from the rest of the software. This leads to transparent and stable code. Summing up, the use of a commercially available computer module running Linux led to a very flexible, future-oriented and cost-effective solution.