Hitachi Europe Ltd’s European Design & Engineering Support Centre has been collaborating with Irvine, California-based Togai Infralogic Inc – also suppliers to VLSI Technology Inc (CI No1,971) – on a Fuzzy Logic tool set for its H8/300 and H8/500 single chip microcontrollers. The tool package includes a Fuzzy Compiler, Fuzzy Kernal and graphical development environment known as TilShell+. It is aimed at developers designing control systems for consumer electronic goods, motors, air conditioning systems. Fuzzy Logic enables systems to understand imprecise concepts like ‘a bit’, or ‘fairly’, unlike conventional logic which recognises that objects are members of a particular set or not. Hitachi reckons this makes it ideal for designing complex controllers such as engine control systems in cars that have to cope with a wide range of inputs like uphill and downhill gradients, changes in wind speed, road surface, engine performance and demands from the driver. Conventional methods would use look-up tables to map inputs to outputs as a series of points – a time-consuming and complicated process. Fuzzy logic, meantime, recognises that ‘if’ speed is very ‘and’ accelerator is light ‘then’ throttle is maximum. This simplifies programming, enabling designers to concentrate on system design rather than control theory. It also helps speed up development and produces much smoother overall control. Hitachi has adapted Togai’s Fuzzy tools specifically for its high performance 8-bit H8/300 and 16-bit H8/500 chip families. The chips feature up to 2Kb on-chip RAM, and up to 62Kb on-chip ROM or EPROM. They can operate at between 3V and 5V and are a compact 0.5 across by 0.05 high. About a million of each are shifted per month for use in single lens reflex cameras, engine control systems and mobile telephones. Hitachi’s Fuzzy Compiler will run on any 80386-compatible personal computer under Windows 3.0 or above.
Source files in MicroFPL
It takes source files in MicroFPL – a special programming language for defining a Fuzzy System – and then compiles them to an assembler level code for H8 microcontrollers. The Fuzzy System itself comprises three parts: variable definition; rule base definition; and connections. Variable definition involves specifying Fuzzy variables either as signed an unsigned bytes or fixed signed and unsigned bytes. The functions of each variable can be defined as a set of points or by using a mathematical equation. Users define the rules specifying how the input variables are to be tested so that output variables can be generated. Operators can be used with the variables to produce Fuzzy rules such as ‘IF temperature IS high AND old temperature is high THEN pump-control IS max cool’. The Rulebase is made up of a number of such rules and forms the heart of a Fuzzy system. Rules concerning the connections between various components are then implemented, such as CONNECT FROM Temperature TO Heatpump END. When files have been created using the MicroFPL definition, they are run through the compiler. The compiler produces a set of data tables to be used by the Fuzzy kernel. This uses the data to provide an output result that can be read by the user. The output is also ‘defuzzified’, or converted into the microcontroller’s language. TilShell+ provides the programmer with a graphical user interface for developing and modifying Fuzzy systems. It has a Project Editor that defines the system connections, specifying which are the input and output variables associated with which Fuzzy Rulebase; and Variable/Membership Function Editor -a graphical means of defining system variables. The Fuzzy Rulebase editor makes it easier to generate the Rulebase by using the system variables to prompt the programmer with options available. TilShell+ also features a description language that enables users to define a model of the system which can then be simulated. The system variables can then be viewed during simulation using a special watch window. There are two package options available for the H8/300 and H8/500. Fuzzy Development Kits for eac
h are for developing application code and small prototype systems and cost UKP1,200. The kits contain the MicroFPL Compiler, Fuzzy Interpreter and TilShell+. An Unlimited Copy Licence, which costs UKP8,000, is needed to market products created using the development kit.
