Natural Machine Logic, a Design Tool for Safety Functions

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Natural Machine Logic is the theory and practice of process logic for machine control that relates live physical events to each other rather than relating data from numbered locations in memory. Natural Machine Logic (NML) describes and monitors the temporal relationships between critical process events in continuous time. As a system of hardware logic, it is an alternative to computation, software and microprocessors. NML is appropriate for process controllers in which emergency stops act to prevent harm to personnel or equipment. It is safe, fast, and secure, because it does not rely upon run-time software, but reacts to the elemental process events. There are no delays due to data movements and comparisons. There are no interruptions, as NML logic elements are directly connected between sensors and control actuators. It responds quickly and surely because its logic elements are dedicated and in parallel, so it is never busy doing anything else. It needs fewer parts, so its control functions are less subject to component failure. It is compatible with microprocessor technology and can function independently for safety in parallel with systems designed to collect and manage data. NML has high integrity against cyber attacks. Critical functions can be pre-configured locally in sophisticated logic elements isolated from the operating system and from the internet.

Computation is limited to expressions of static state with the operators AND (conjunction), NOT (negation), OR (disjunction), (and their combinations) and STORE (for memory).

NML provides a sense of time to machine controllers through the sophisticated operators CREATES (assigns cause), THEN (determines sequence), AGAIN (signifies repetition), BEGINS, ENDS, ANDTHEN (determines sequence and conjunction overlap), PULSE (signifies the beginning of a change), and WHILE (concurrency). The behavior of a real-time process is much easier to describe using these dynamic operators in NML and simpler to control with the corresponding sophisticated hardware logic elements. The computational operators and their elements are in the static space domain, where the only means of access is the linear sequential method. The dynamic operators and logic elements added in NML operate in the time domain and react as change occurs in a parallel-concurrent way. NML includes temporal logic for the time domain, a temporal algebra as a design tool, and a methodology to convert a process narrative into hardware controllers, as set forth in the reference materials.

NML safety control, and mission- and time-critical functions can be configured and reconfigured in field-programmable logic arrays (FPGAs) within machine controllers by using a smart-phone app. As an alternative to computation, NML is just the thing for pre-software economies.

Synthesis of Dynamic Digital Controllers and the Case for Natural Logic,
Logic Synthesis of a 100MHz Quadrature Decoder using Natural Logic, a Cool Runner CPLD and Free EDA Software, IEEE IWLS 2000
Synthesis of a Solution to the Yale Shooting Problem, IEEE IWLS 2001
Natural Logic of Space and Time, a preview of which is available at:


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  • Name:
    Charles Moeller
  • Type of entry:
  • Profession:
  • Charles is inspired by:
    Problems I see in the work environment.
  • Software used for this entry:
    Xilinx XPLA, NL5
  • Patent status: