Siemens – LMS controls engineering is an engineering discipline that deals with designing and implementing control systems to achieve a desired overall system behavior. It is the backbone of “smart” products. In its basic form, a control system lets you measure a performance factor in the product using sensors. Based on this measurement data, you can adjust the behavior of product to regulate the performance factor towards a desired objective.
The first step is to understand the requirements. You can design a control system that can meet multiple objectives, but it is important to understand the different objectives and the interactions. How fast should a product react to change in the system? What about a change in external conditions?
You need to get a big picture view. Some of the requirements could set performance goals, which have to be optimized, while others serve as constraints to be satisfied. Some of these requirements can be competing against each other and the design should carefully trade off between competing requirements.
Then we draw out a boundary diagram of the system architecture. What are the components of the system that can be measured by sensors, and which system properties can be changed by actuation to satisfy the requirements? At this point, we do a requirement feasibility analysis to see if the existing sensors and actuators can actually meet the system objectives. Such analysis is mostly done today using system simulation with computer models. Examining the analysis results, we can see if the conceptual system architecture is really possible. If yes, we start a detailed design.
We start by dividing the controller into units according to the required functions. When designing an engine control system, for example, we have to make sure that we are delivering the required torque. To do this, you design a torque management function that “measures” the torque demand through the driver accelerator pedal input. Then this is translated into appropriate airflow and spark-timing actuations to deliver the demanded torque at the engine crank shaft.
In parallel, you look at the fuel management function that seeks to minimize fuel consumption while delivering the required fuel to generate torque. The emission control and thermal management functions also impose constraints on how the airflow, spark timing and fuel system are actuated to ensure that exhaust emissions are minimized and the engine operates in an efficient temperature range. It is a bit like completing a 10,000 piece jigsaw puzzle.
To realize the control system within the overall architecture, we start to define the interfaces and populate the various system functions to fulfill requirements. Today, computer models of the controller units are built to virtualize the functions. The units and their interfaces are rendered graphically to assist the engineers in rapidly evolving design processes. In parallel, we design and implement test cases to make sure that the control system works and meets requirements. more> http://tinyurl.com/nme6utm
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