On Using a Support Vector Machine in Learning Feed-Forward Control

For mechatronic motion systems, the performance increases significantly if, besides feedback control, also feed-forward control is used. This feed-forward part should contain the (stable part of the) inverse of the plant. This inverse is difficult to obtain if non-linear dynamics are present. To overcome this problem, learning feed-forward control can be applied. The properties of the learning mechanism are of importance in this setting. In the paper, a support vector machine is proposed as the learning mechanism. It is shown that this mechanism has several advantages over other learning techniques when applied to learning feed-forward control. The method is tested with simulation

Phase correction for Learning Feedforward Control

Intelligent mechatronics makes it possible to compensate for effects that are difficult to compensate for by construction or by linear control, by including some intelligence into the system. The compensation of state dependent effects, e.g. friction, cogging and mass deviation, can be realised by learning feedforward control. This method identifies these disturbing effects as function of their states and compensates for these, before they introduce an error. Because the effects are learnt as function of their states, this method can be used for non-repetitive motions. The learning of state dependent effects relies on the update signal that is used. In previous work, the feedback control signal was used as an error measure between the approximation and the true state dependent effect. If the effects introduce a signal that contains frequencies near the bandwidth, the phase shift between this signal and the feedback signal might seriously degenerate the performance of the approximation. The use of phase correction overcomes this problem. This is validated by a set of simulations and experiments that show the necessity of the phase corrected scheme

Pruning Error Minimization in Least Squares Support Vector Machines

The support vector machine (SVM) is a method for classification and for function approximation. This method commonly makes use of an /spl epsi/-insensitive cost function, meaning that errors smaller than /spl epsi/ remain unpunished. As an alternative, a least squares support vector machine (LSSVM) uses a quadratic cost function. When the LSSVM method is used for function approximation, a nonsparse solution is obtained. The sparseness is imposed by pruning, i.e., recursively solving the approximation problem and subsequently omitting data that has a small error in the previous pass. However, omitting data with a small approximation error in the previous pass does not reliably predict what the error will be after the sample has been omitted. In this paper, a procedure is introduced that selects from a data set the training sample that will introduce the smallest approximation error when it will be omitted. It is shown that this pruning scheme outperforms the standard one

On-line nonparametric regression to learn state-dependent disturbances

A combination of recursive least squares and weighted least squares is made which can adapt its structure such that a relation between in- and output can he approximated, even when the structure of this relation is unknown beforehand.\ud This method can adapt its structure on-line while it preserves information offered by previous samples, making it applicable in a control setting. This method has been tested with compntergenerated data, and it b used in a simulation to learn the non-linear state-dependent effects, both with good success

De geschiedenis van de veterinaire verloskunde

Extraction, reposition, fetotomy (embryotomy) and even cesarean section have been part of human and animal obstetrics since ancient times. Destructive operations like craniotomy and embryotomy are the oldest type of obstetrical operations. At the end of the 18(th) century the subcutaneous fetotomy was developed. It remained the preferred fetotomy method in farm animals and horses till the beginning of the 20(th) century. Then the tubular fetotome was invented and the subcutaneous fetotomy was replaced by the percutaneous fetotomy. This obstetrical method was easy to learn and its results were excellent. However, the fetus had to be sacrificed. Therefore, after the introduction of antibiotics, the percutaneous fetotomy in cows was replaced by the cesarean section. In horses, the percutaneous fetotomy is still the preferred obstetrical method as foals die rapidly and a partial fetotomy (one or two cuts) is in the majority of cases sufficient to solve the obstetrical problem. Because of its minimal economic importance, obstetrics in small animals did not receive any attention till the end of the 19(th) century. In these animal species, cesarean section is the best solution in cases of serious obstetrical problems

Hard sphere colloidal dispersions: Mechanical relaxation pertaining to thermodynamic forces

The complex viscosity of sterically stabilized (hard) silica spheres in cyclohexane has been measured between 80 Hz and 170 kHz with torsion pendulums and a nickel tube resonator. The observed relaxation behaviour can be attributed to the interplay of hydrodynamic and thermodynamic forces. The validity of the Cox-Merz rule is checked

Microbe Hunters

Microbe Hunters by Paul de Kruif was first published in 1926 by Harcourt, Brace and Company, New York. It dramatically recounts the breakthrough discoveries of the fundamental elements of bacteriology. It features exciting profiles of Antony Leeuwenhoek, Lazzaro Spallanzani, Louis Pasteur, Robert Koch, Émile Roux, Emil Behring, Élie Metchnikoff, Theobald Smith, David Bruce, Ronald Ross, Battista Grassi, Walter Reed, and Paul Ehrlich. Their development of germ theory and its scientific proofs led to the first effective treatments for human diseases like anthrax, rabies, diptheria, malaria, sleeping sickness, syphilis, and yellow fever. They also made discoveries that saved the dairy, wine, beer, silk, and cattle industries. These determined experimenters proved time and again that tiny living beings only seen by microscope can have huge impacts on human life, and they emphatically demonstrated the value of science for modern civilization. A best seller in its time, the work is an enduring classic that has inspired many scientific careers. Paul de Kruif (1890–1971) was an American microbiologist and World War I veteran who turned to writing after his dismissal from the Rockefeller Institute for Medical Research because of his controversial opinions on current medical practice published in a book of essays. Among his other works, he also assisted Sinclair Lewis with the background of science for the novel Arrowsmith (1925). doi: 10.32873/unl.dc.zea.1503https://digitalcommons.unl.edu/zeabook/1147/thumbnail.jp

De doeltreffendheid van twee anti-misbruikmaatregelen in de Wet open overheid

Het wetsvoorstel Wet open overheid bevat twee anti-misbruik maatregelen. De Woo zal zijn losgekoppeld van de Wet dwangsom en er is een algemene anti-misbruik bepaling opgenomen: artikel 4:6 Woo. Na een uitvoerig betoog concludeer ik dat deze maatregelen niet zondermeer doeltreffend zijn. Er zijn namelijk andere, niet losgekoppelde wetten, die zich evenzo goed lenen voor oneigenlijk gebruik waardoor het probleem zich makkelijk kan verschuiven. Ook blijft er een financiële prikkel in de vorm van een proceskostenvergoeding bestaan. Verder heeft, sinds november 2014, de algemene anti-misbruik bepaling uit het Burgerlijk Wetboek (artikel 3.13 BW) zijn weg in het bestuursrecht gevonden. Na een uitgebreide analyse van de jurisprudentie concludeer ik dat het niet uitmaakt of er wel of niet een eigen anti-misbruik bepaling in de Woo komt. Laat je ‘m weg dan ontwikkelt de anti-misbruik jurisprudentie zich voort onder de noemer van artikel 3.13 BW. Kiezen we voor een bestuursrechtelijke anti-misbruik bepaling dan kan de draad worden opgepakt daar waar we nu gebleven zijn maar dan onder een andere noemer