Abstract
We have implemented an IEC 61131-3 IL (Instruction List) and ST (Structured Text) compiler that will be part of an open source PLC. In doing so, several issues were found regarding the specification of the IL and ST languages, produced by the IEC (International Electrotechnical Commission ) standards body. The uncovered issues are discussed in this paper, and some changes to the standard are proposed. The architecture used in the compiler implementation is also outlined in the paper. © 2003 IEEE.

Abstract
This paper presents the implementation of fractional-order algorithms in the position/force hybrid control of robotic manipulators. The system performance and robustness is analyzed in the time and frequency domains. The effect of dynamic backlash and flexibility is also investigated.

Abstract
The variation in airborne pollen concentration of the Braga region (Portugal) was studied in springtime, during the flowering of Vitis vinifera. The data set was obtained for two consecutive years (1999 and 2000), using a Cour-type sampler. During this period, thirty-six taxa were observed in a total of 3,200 pollen grains m-3 of air (CPA). The main pollen types observed were Olea, Poaceae and Castanea, representing 74% of the pollen spectrum. The airborne pollen concentration (CPA) was significantly correlated with certain meteorological parameters. Pollen concentration was positively correlated with temperature and wind direction (East and Northeast) and negatively correlated with rainfall and number of rainy days.

Abstract
A forecast model for estimating the annual variation in regional wine production has been developed over the past decade for the main wine regions of northern Portugal. Annual wine production has been forecasted based on a hierarchical analysis, including a determination of potential production by measuring airborne pollen concentrations at flowering with Cour traps followed by an evaluation of the possible impact of postflowering conditions on limited crop production. For each region, airborne pollen concentrations, in conjunction with wine yield, account for up to 90 to 95% of the interannual variations in wine production. Ninety-seven to 99% of the annual variability in regional wine production can be explained by agropalynoclimatological forecast models that take into account a number of agronomic and weather conditions after flowering. The reliability and early-indication ability of these forecast models justify their use by institutions and economists in decision making, adoption of technical improvements, and fraud detection.

Abstract
The annual airborne pollen variation of the Porto region was studied from November 2001 to October 2002 using a Cour type sampler. A total of 170 × 106 grains m-2 belonging to 63 taxa was observed. The vegetation surrounding the sampling point includes ornamental, non-ornamental trees, shrubs and herbaceous species. The main pollen types were Cupressaceae, Gramineae, Hamamelidaceae, Pinaceae, Urticaceae, Quercus spp., Acer spp., Myrtaceae, Caryophyllaceae, Oleaceae, Betulaceae and Plantago spp. that represented 88% of the Porto pollen spectrum. Gramineae, Cupressaceae, Myrtaceae, Oleaceae, Pinaceae and Urticaceae pollen are found throughout the year. Concerning total pollen concentration, the distribution throughout the year is very irregular, with several annual peaks, with the maximum concentration registered between the end of March and the first two weeks of April and the lowest observed during autumn.

Abstract
This paper studies periodic gaits of multi-legged robot locomotion systems based on dynamic models. The purpose is to determine the system performance during walking and the best set of locomotion variables that minimizes the optimization indices. For that objective the prescribed motion of the robot is completely characterized in terms of several locomotion variables such as gait, duty factor, body height, step length, stroke pitch, foot clearance, leg links length, foot-hip offset, body and legs mass and cycle time. In this perspective, we formulate four performance measures of the walking robot namely, the foot locomobility index, the mean absolute power, the mean power dispersion and the mean power lost in the joint actuators per walking distance. A set of model-based experiments reveals the influence of the locomotion variables in the proposed indices. Copyright © 2002 IFAC.