Model-based design tools write control software for industrial equipment
Approached by a wind turbine manufacturer about a year ago, engineers at Rockwell Automation were asked, “Can you get ControlLogix to run C code?” Meanwhile, Matlab and Simulink software from The MathWorks Inc. was generating C, C++, VHDL and Verilog code from models, which would be run on PC-based control systems.
Approached by a wind turbine manufacturer about a year ago, engineers at Rockwell Automation were asked, “Can you get ControlLogix to run C code?” Meanwhile, Matlab and Simulink software from The MathWorks Inc. was generating C, C++, VHDL and Verilog code from models, which would be run on PC-based control systems. Following a few months of integration and negotiation between the companies, The MathWorks developed a tool to transform its model-based designs into code for programmable logic controllers (PLCs) called Simulink PLC Coder.
The MathWorks software is used to design, simulate, test and validate complex mechatronic systems built on PC-based controls. Development involves creating models that capture electrical, mechanical, controls and process parameters in block diagrams and algorithms that show the interrelationships. As the models are run, the software creates plots and captures data that generates code for algorithms, and also generates code for test cases. This lets machine builders test and validate system design before generating executable code for a specific hardware platform, such as microcontrol units (MCUs) and field programmable gate arrays (FPGAs).
The MathWorks doesn’t handle the executable code portion of the process. “We don’t produce compilers,” said Tom Erkkinen, Simulink PLC Coder product manager for The MathWorks, “so we needed Rockwell to get us to the hardware. PLCs are a unique animal, but given our software architecture, it was fairly easy to leverage our coder for a new language. That means it’s not a version 1 coder. Its roots go back to 1992.”
The hardware, in this case, is ControlLogix PACs using RSLogix 5000 software. Simulink PLC Coder takes the Matlab or Simulink algorithms and generates IEC 61131 structured text (ST). RSLogix 5000 takes ST and produces an executable for the PLC. “It also produces 'hooks’ that link back to the algorithms, which show that the model matches the executable code generated, as well as [produces] code for test cases,” said Weber. “Once in RSLogix, I can compare test case results. Now I know that what I implemented matches my model.”
Benefits of such model-based design include:
Speeds design, testing, improvement, implementation, deployment, and upgrade of any PLC-based machine, cutting out many duplicative steps along the way.
Preserves engineering and intellectual assets as information flows from individuals or departments involved with design, simulation, testing, and engineering/operations;
Saves money by identifying and addressing design flaws or coding errors earlier in the process.
Builds in validation steps as design progresses, especially useful for high-speed machine applications;
Lets machine builders do design iterations in hours rather than days;
Eliminates documentation time, as the software automatically generates documentation;
Allows library creation for faster designs later, or improvements on current design more quickly and simply (matrix multiplication can be done in one or two lines of code in Matlab versus 100 or 200 lines of code in C or ST);
Can port model-based simulations to other targets in other languages (such as C and HDL) using related tools;
The Rockwell/MathWorks agreement is the latest in a series of Rockwell Automation software supplier partnerships. Other partnership companies include Dassault Systemes and ePlan.
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