Simulink block library Function Chart: essential features - all rights reserved - Dr. Geitner ETI/TU Dresden

The software tool Function Chart block library has been developed for the design, simulation, code generation and the description of event-driven systems especially in the fields of mechatronics, mechanical and electrical engineering. It is an add-on block set for MATLAB/Simulink. Its essential features are:

• Function Chart is an open system with block-oriented design and the possibility to generate C-code for real-time applications. It may be handled like standard Simulink blocks, i.e. there is no special window and no additional run of a compiler in case of simulations or of a function chart coder in case of a real-time application.
• With regard to the graphical presentation, i.e. the block icons, it is intended to approach the VDI / VDE guideline 3684 "Description of event-driven motion processes by function charts". This guideline has been worked out by the GMA committee 4.12 "Motion control of machine tools and processing machines" and is published by Beuth Berlin.
• Examples for important unavoidable variances of the graphical presentation of the library Function Chart in comparison with guideline 3684 are the connection of the KB block ( comment block) with the output of a state block (originally on the right side of a state block, e.g. ZA), the general graphical marker of the action direction via arrows (originally for upward action direction only) and the connection of events to event blocks via "goto" blocks (originally event names without squared brackets and not within a block). The comment block is able to transmit parameters of different definition but no mathematical equation in contrast to the guideline.
• There are no limitations with reference to the nesting of branching and junction in a function chart, i.e. parallel and alternativebranches may be arbitrarily nested according to the syntax.
• There are no limitations with reference to the creation of sub function charts (subsystems). Consequently large function charts may be arbitrarily divided for screen-compatible programming of the motion processes. Please note however that the block icons containing these subsystems will not have any specific block icon. For this case it is recommended to choose a text for good recognition (display command in block mask menu).
• The state numbers are freely selectable as natural numbers from 1 to 9999 without zero. There is no connection between the internal Simulink automatic block numbering and the freely selectable state numbers.
• The definition of a function chart number and a state number makes it possible to handle several function charts simultaneously. Optionally in different function charts the same state numbers may be applied. Natural numbers from 1 to 9 without zero can be chosen as function chart numbers.
• Comment blocks ( KB as a sender) and Variable blocks ( FUP_V as a receiver) serve as interfaces between function charts and motion cells (drives) - without any graphical connection. The transmitted control variables may be numerical or logical ones. Unlike state numbers these variables are valid between different functioncharts and process models on demand, if the same names are used.
• The continuous programming of the functionality by means of S-functions and MEX-files on the basis of C-code as well as the economic usage of standard blocks guarantee minimum run times.
• Function Chart enables the handling of motion errors as transitions from normal operation to separate error sub function charts without any graphical connection. Starting from any normal state it is possible that a transition to one of several error handling sequences may be made. The graphical clearness will not worsen. If an error signal is initiated all normal operation states of the paticular function chart get inactive while the common error state ZF gets active for that moment. Afterwards one of several prepared error handling states gets active, which depends on the pre-error states and the Boolean equations. Re-entry points to the normal operation can be selected freely according to the technological reqirements.
• A system check-up is possible by displaying active states. Optionally the AZFx block performs the display of all active states of a function chart or the DA block shows the active states of a selected number of states in different function charts.
• Function Chart implies extensive automatic design support. Based on a browser each block offers help text with due regard to the intended purpose and the use limitations. Easy block parameter setting errors cause an acoustic signal and the display of an error text. Structure errors, such as defined variable names and related accesses, defined state numbers and related Boolean error equations, dead ends or competitive signal transmission may be detected and displayed with add-on software tools.
• Real-time code generation may be done as easy as it is prepared for Simulink itself. No special window, no special function chart coder is necessary. If a PC based motion control is to be performed, it is merely necessary to use MATLAB Compiler and add-on software Simulink Coder (formerly RTW, Real-Time Workshop) as well as xPC-Target (formerly RealLink/32) as target support package and hardware driver library. Existing xPC-Target make-files may be used without modification. Function Chart library registration is the only condition.
• Run time savings are possible by use of compiler switches for block parameter setting errors. This is useful at the end of a development cycle. The user can also influence the necessary memory hardware for real-time operation by specification of the maximum number of parallel states and parallel function charts as well as the transmitted variables.
• The software provides help for error search in technological cycles and for easy explorations of technological variants. At early design cycles and for selected errors event generation may be replaced by on-line switches. Alternative paths and switches for variants enable the comparison of different technological cycles for simulation and real-time operation. Both operation modes may work using on-line switch generated events in order to enable the stepping mode totally or partially. State variables and events may be scanned not only at simulation but also at real-time operation.