Anything technical could appear in this section

Excluding technical climbing.

 


  • The latest addition: Here is a tutorial showing how you can use the Maxima software package from gnu.org to derive formulas for complex electronic network properties, such as active filter transfer gain characteristics, driving point impedances, S-parameters, and so forth, using symbolic computation.

  • The Web provides lot of information about poor ways to estimate derivatives of a function from measured data. Classical methods based on exact polynomial fitting (such as the "method of central differences") have horrible noise sensitivity, while other methods with better noise response properties compromise on accuracy. Some experiments led to two new design approaches — both of which are actually old design approaches with a few important details worked out. To see exactly what that means, you will have to check the pages...

    • Background information about the problem, illustrating the difficulty of derivative estimation, and how seemingly good approaches fail to work well in practice.
    • An FFT-based design method that works exceptionally well, but at a price. The design process is complicated, with non-obvious manual tweaking of parameters. The results are attractive and very accurate, but they use about twice as much computation as other methods. If computation speed is not an issue, this could be a very good choice.
    • Further investigation produced an optimal design approach that is generally suitable for most ordinary cases where efficiency matters, but noise rejection requirements are not quite so extremely rigorous. Accuracy is close to the FFT-based designs, using about half of the computational effort. Or see a variant design that estimates the value of the second-derivative.
  • Which is better, PID control or state space control? Perhaps this begs the real question. This page discusses how you can have both!

  • This note describes a novel approach to additive synthesis "pink noise" using multiple non-white random generator stages. Though not the fastest known method, it is very close, with additional advantages of being simpler to program, particularly with fixed-point embedded processors, and much better spectral accuracy. This is is suitable for test signal generation and digital music applications.

  • Here is an alternative to the usual prematurely linearized models typiclly used to represent a hydraulic actuator for nonlinear control systems. I think this might be a significant improvement, but who will ever know, this has never been tried! (Most systems continue to use a classic model with constant, linear compression through full range up to absolute "hard limits" of travel. These questionable approximations can cause all kinds of unpleasant side effects when using the model for analysis and control purposes.)

  • How to determine a center point offset from a nominally circular element so that maximum and minimum deviations from this adjusted point are bounded as tightly as possible. This is known as "the zone circularity problem" and is one way to test whether a part is manufactured within tolerance.