Analysis and Control of Excitation, Field Weakening and Stability in Direct Torque Controlled Electrically Excited Synchronous Motor Drives

Direct torque control (DTC) is a new control method for rotating field electrical machines. DTC controls directly the motor stator flux linkage with the stator voltage, and no stator current controllers are used. With the DTC method very good torque dynamics can be achieved. Until now, DTC has been applied to asynchronous motor drives. The purpose of this work is to analyse the applicability of DTC to electrically excited synchronous motor drives. Compared with asynchronous motor drives, electrically excited synchronous motor drives require an additional control for the rotor field current. The field current control is called excitation control in this study. The dependence of the static and dynamic performance of DTC synchronous motor drives on the excitation control has been analysed and a straightforward excitation control method has been developed and tested. In the field weakening range the stator flux linkage modulus must be reduced in order to keep the electro motive force of the synchronous motor smaller than the stator voltage and in order to maintain a sufficient voltage reserve. The dynamic performance of the DTC synchronous motor drive depends on the stator flux linkage modulus. Another important factor for the dynamic performance in the field weakening range is the excitation control. The field weakening analysis considers both dependencies. A modified excitation control method, which maximises the dynamic performance in the field weakening range, has been developed. In synchronous motor drives the load angle must be kept in a stabile working area in order to avoid loss of synchronism. The traditional vector control methods allow to adjust the load angle of the synchronous motor directly by the stator current control. In the DTC synchronous motor drive the load angle is not a directly controllable variable, but it is formed freely according to the motor’s electromagnetic state and load. The load angle can be limited indirectly by limiting the torque reference. This method is however parameter sensitive and requires a safety margin between the theoretical torque maximum and the actual torque limit. The DTC modulation principle allows however a direct load angle adjustment without any current control. In this work a direct load angle control method has been developed. The method keeps the drive stabile and allows the maximal utilisation of the drive without a safety margin in the torque limitation.

Comparisons between two economically valuable forest species (Eucalyptus grandis and Pinus taeda) in relation to seed behaviour under controlled deterioration

The objectives of this work were to analyze seed behaviour under controlled deterioration and estimate viability equations for forest species Eucalyptus grandis and Pinus taeda. Desired moisture content levels were achieved from initial values after either rehydration over water or drying over silica gel, both at 25 ºC. Seed sub samples with 8 moisture contents each for E. grandis (1.2 to 18.1%, initial value of 11.3%) and P. taeda (1.5 to 19.5%, initial value of 12.9%) were sealed in laminate aluminium-foil packets and stored in incubators maintained at 40, 50 and 65 ºC. The seeds from these species exhibited true orthodox and sub-orthodox storage behaviour, respectively, however E. grandis showed higher seed storability, probably due to a different seed chemical composition. Lowest moisture content limits estimated for application of the viability equations at 65 ºC were 4.9 and 4.1 mc for E. grandis and P. taeda, on equilibrium with ±20% RH. The viability equation estimated quantified the response of seed longevity to storage environment well with K E = 9.661 and 8.838; C W = 6.467 and 5.981; C H = 0.03498 and 0.10340; C Q = 0.0002330 and 0.0005476, for E. grandis and P. taeda, respectively.

Electrically driven fertilizer applicator controlled by fuzzy logic

The present study shows the development, simulation and actual implementation of a closed-loop controller based on fuzzy logic that is able to regulate and standardize the mass flow of a helical fertilizer applicator. The control algorithm was developed using MATLAB's Fuzzy Logic Toolbox. Both open and closed-loop simulations of the controller were performed in MATLAB's Simulink environment. The instantaneous deviation of the mass flow from the set point (SP), its derivative, the equipment´s translation velocity and acceleration were all used as input signals for the controller, whereas the voltage of the applicator's DC electric motor (DCEM) was driven by the controller as output signal. Calibration and validation of the rules and membership functions of the fuzzy logic were accomplished in the computer simulation phase, taking into account the system's response to SP changes. The mass flow variation coefficient, measured in experimental tests, ranged from 6.32 to 13.18%. The steady state error fell between -0.72 and 0.13g s-1 and the recorded average rise time of the system was 0.38 s. The implemented controller was able to both damp the oscillations in mass flow that are characteristic of helical fertilizer applicators, and to effectively respond to SP variations.

Effect of companion ion on nitrate displacement through transport parameters analysis

Nitrate is the main form of nitrogen associated with water contamination; the high mobility of this species in soil justifies the concern regarding nitrogen management in agricultural soils. Therefore, the objective of this research was to assess the effect of companion cation on nitrate displacement, by analyzing nitrate transport parameters through Breakthrough Curves (BTCs) and their settings made by numerical model (STANMOD). The experiment was carried out in the Soil and Water Quality Laboratory of the Department of Biosystems Engineering, "Luiz de Queiroz" College of Agriculture in Piracicaba (SP), Brazil. It was performed using saturated soil columns in steady-state flow condition, in which two different sources of inorganic nitrate Ca(NO3)2 and NH4NO3 were applied at a concentration of 50 mg L-1 NO3-. Each column was filled with either a Red-Yellow Oxisol (S1) or an Alfisol (S2). Results are indicative that the companion ion had no effect on nitrate displacement. However, nitrate transport was influenced by soil texture, particle aggregation, solution speed in soil and organic matter presence. Nitrate mobility was higher in the Alfisol (S2).

Portable flow board for storage of fruits and vegetables in mini-chambers with controlled atmosphere

ABSTRACT A portable flow board system was developed in the present study with the aim to facilitate lab-scale experiments of controlled atmosphere (CA) with fruits and vegetables. This sturdy flow board combines ease fabrication, low cost and gas economy. Its functionality is provided by manifolds and gas mixers. Each gaseous component is supplied by a gas cylinder through a differential valve of adjusted pressure control, generally at 6 kPa, and forced through 13 standardized restrictors coupled to each manifold output. Controlled atmospheres are then formed with one, two or three gases in 13 gas mixers affixed to the flow board base, which are further conducted through flexible tubes to storage mini-chambers that can also be used to study metabolic consumption and production of gaseous components. The restrictors used in the flow gaseous components were manufactured from microhematocrit test-type capillary glass tubes following the hot forming method under continuous air flow. The portable flow board showed to be low cost and simple post-harvest equipment that allows preparing controlled atmospheres in open systems with stable composition and flow, in a manner similar to traditional flow boards with control of gas escape by barostats.

Loss Modelling of Three-Level Inverters controlled with Space Vector Modulation Technique

The objective of this master’s thesis is to investigate the loss behavior of three-level ANPC inverter and compare it with conventional NPC inverter. The both inverters are controlled with mature space vector modulation strategy. In order to provide the comparison both accurate and detailed enough NPC and ANPC simulation models should be obtained. The similar control model of SVM is utilized for both NPC and ANPC inverter models. The principles of control algorithms, the structure and description of models are clarified. The power loss calculation model is based on practical calculation approaches with certain assumptions. The comparison between NPC and ANPC topologies is presented based on results obtained for each semiconductor device, their switching and conduction losses and efficiency of the inverters. Alternative switching states of ANPC topology allow distributing losses among the switches more evenly, than in NPC inverter. Obviously, the losses of a switching device depend on its position in the topology. Losses distribution among the components in ANPC topology allows reducing the stress on certain switches, thus losses are equally distributed among the semiconductors, however the efficiency of the inverters is the same. As a new contribution to earlier studies, the obtained models of SVM control, NPC and ANPC inverters have been built. Thus, this thesis can be used in further more complicated modelling of full-power converters for modern multi-megawatt wind energy conversion systems.

Postoperative topical analgesia of hemorrhoidectomy with policresulen and cinchocaine: a prospective and controlled study

OBJECTIVE: To evaluate the effects of topical policresulen and cinchocaine in the postoperative pain behavior of open hemorrhoidectomy.METHODS: We conducted a prospective, double-blinded, controlled study. The control group received the usual guidelines with oral medications. The topical treatment group received, in addition, the application of the ointment and was comprised of two subgroups (policresulen + cinchocaine, and placebo). Pain intensity was recorded with the visual analogue scale.RESULTS: 43 patients were operated on: control group - n = 13, one excluded; placebo - n = 15; and policresulen + cinchocaine - n = 15. The mean age was 45.98 years and 37.2% were men. The average pain intensity was 4.09 (immediate postoperative), 3.22 (hospital discharge), 5.73 (day 1) , 5.77 (day 2), 5.74 (day 3), 5.65 (day 7), 5.11 (day 10), 2.75 (day 15) and 7.70 (first bowel movement), with no difference between groups in all periods.CONCLUSION: This study showed no reduction in pain after hemorrhoidectomy with the use of topical policresulen and cinchocaine.

Standardization of pulmonary ventilation technique using volume-controlled ventilators in rats with congenital diaphragmatic hernia

OBJECTIVE: To standardize a technique for ventilating rat fetuses with Congenital Diaphragmatic Hernia (CDH) using a volume-controlled ventilator.METHODS: Pregnant rats were divided into the following groups: a) control (C); b) exposed to nitrofen with CDH (CDH); and c) exposed to nitrofen without CDH (N-). Fetuses of the three groups were randomly divided into the subgroups ventilated (V) and non-ventilated (N-V). Fetuses were collected on day 21.5 of gestation, weighed and ventilated for 30 minutes using a volume-controlled ventilator. Then the lungs were collected for histological study. We evaluated: body weight (BW), total lung weight (TLW), left lung weight (LLW), ratios TLW / BW and LLW / BW, morphological histology of the airways and causes of failures of ventilation.RESULTS: BW, TLW, LLW, TLW / BW and LLW / BW were higher in C compared with N- (p <0.05) and CDH (p <0.05), but no differences were found between the subgroups V and N-V (p> 0.05). The morphology of the pulmonary airways showed hypoplasia in groups N- and CDH, with no difference between V and N-V (p <0.05). The C and N- groups could be successfully ventilated using a tidal volume of 75 ìl, but the failure of ventilation in the CDH group decreased only when ventilated with 50 ìl.CONCLUSION: Volume ventilation is possible in rats with CDH for a short period and does not alter fetal or lung morphology.

Safety and tolerability of controlled-release oxycodone on postoperative pain in patients submitted to the oncologic head and neck surgery

Objective: To evaluate the safety and tolerability of controlled-release oxycodone in the treatment of postoperative pain of head and neck oncologic resections.Methods: We conducted a prospective, observational and open study, with 83 patients with moderate to severe pain after head and neck oncological operations. All patients received general anesthesia with propofol, fentanyl and sevoflurane. Postoperatively, should they have moderate or severe pain, we began controlled-release oxycodone 20 mg 12/12 b.i.d on the first day and 10 mg b.i.d. on the second. We assessed the frequency and intensity of adverse effects, the intensity of postoperative pain by a verbal numeric scale and the use of rescue analgesia from 12 hours after administration of the drug and between 7 and 13 days after the last oxycodone dose.Results: The most common adverse events were nausea, vomiting, dizziness, pruritus, insomnia, constipation and urinary retention, most mild. No serious adverse events occurred. In less than 12 hours after the use of oxycodone, there was a significant decrease in the intensity of postoperative pain, which remained until the end of the study. The rescue medication was requested at a higher frequency when the opioid dose was reduced, or after its suspension.Conclusion: Controlled release oxycodone showed to be safe and well tolerated and caused a significant decrease in post-operative pain.

Induction of labor with titrated oral misoprostol solution versus oxytocin in term pregnancy: randomized controlled trial

PURPOSE: To evaluate the effectiveness and the safety of orally administered misoprostol in comparison to intravenously infused oxytocin for labor induction in term pregnant women. METHODS: Between 2008 and 2010, a total of 285 term pregnant women whom were candidate for vaginal delivery were assessed for eligibility to enter the study. Twenty five patients were excluded for different reasons; and 260 included women were randomly assigned to one of the two groups according to the method of treatment, misoprostol or oxytocin. The misoprostol group received 25 µg every 2 hours for up to 24 hours for induction. The oxytocin group received an infusion of 10 IU which was gradually increased. The time from induction to delivery and induction to the beginning of the active phase and successful inductions within 12, 18, and 24 hours were recorded. The trial is registered at irct.ir, number IRCT2012061910068N1. RESULTS: Failure of induction, leading to caesarean section was around 38.3% in the oxytocin group and significantly higher than that of the misoprostol group (20.3%) (p<0.001). Despite the more prevalent failure in the oxytocin group, the mean time intervals from induction to active phase and labor of this group were both significantly less than the misoprostol group (10.1±6.1 and 13.2±7.7 versus 12.9±5.4 and 15.6±5.1 hours respectively, both p-values were <0.05). Maternal and fetal complications were comparable between groups except gastrointestinal symptoms which were encountered more frequently in the misoprostol (10.9 versus 3.9%, p=0.03). CONCLUSIONS: Misoprostol is a safe and effective drug with low complications for the induction of labor. Failure is seen less with misoprostol and caesarean sections are less frequently indicated as compared to oxytocin.

The effect of soy dietary supplement and low dose of hormone therapy on main cardiovascular health biomarkers: a randomized controlled trial

PURPOSE: To assess the effects of a soy dietary supplement on the main biomarkers of cardiovascular health in postmenopausal women compared with the effects of low-dose hormone therapy (HT) and placebo.METHODS: Double-blind, randomized and controlled intention-to-treat trial. Sixty healthy postmenopausal women, aged 40-60 years, 4.1 years mean time since menopause were recruited and randomly assigned to 3 groups: a soy dietary supplement group (isoflavone 90mg), a low-dose HT group (estradiol 1 mg plus noretisterone 0.5 mg) and a placebo group. Lipid profile, glucose level, body mass index, blood pressure and abdominal/hip ratio were evaluated in all the participants at baseline and after 16 weeks. Statistical analyses were performed using the χ2 test, Fisher's exact test, Kruskal-Wallis non-parametric test, analysis of variance (ANOVA), paired Student's t-test and Wilcoxon test.RESULTS: After a 16-week intervention period, total cholesterol decreased 11.3% and LDL-cholesterol decreased 18.6% in the HT group, but both did not change in the soy dietary supplement and placebo groups. Values for triglycerides, HDL-cholesterol, glucose level, body mass index, blood pressure and abdominal/hip ratio did not change over time in any of the three groups.CONCLUSION: The use of dietary soy supplement did not show any significant favorable effect on cardiovascular health biomarkers compared with HT. Clinical Trial Registry: The trial is registered at the Brazilian Clinical Trials Registry (Registro Brasileiro de Ensaios Clínicos - ReBEC), number RBR-76mm75.

Conservative Treatment of Stress Urinary Incontinence: A Systematic Review with Meta-analysis of Randomized Controlled Trials

We performed a systematic review and meta-analysis of randomized controlled trials that studied the conservative management of stress urinary incontinence (SUI). There were 1058 results after the initial searches, from which 37 studies were eligible according to previously determined inclusion criteria. For the primary outcomes, pelvic floor muscle training (PFMT) was more efficacious than no treatment in improving incontinence-specific quality of life (QoL) scales (SMD = [1]1.24SDs; CI 95% = [1]1.77 to [1]0.71SDs). However, its effect on pad tests was imprecise. Combining biofeedback with PFMT had an uncertain effect on QoL (MD = [1]4.4 points; CI 95% = [1]16.69 to 7.89 points), but better results on the pad test, although with elevated heterogeneity (MD = 0.9g; 95%CI = 0.71 to 1,10g); group PFMT was not less efficacious than individual treatment, and home PFMT was not consistently worse than supervised PFMT. Both intravaginal and superficial electrical stimulation (IES and SES) were better than no treatment for QoL and pad test. Vaginal cones had mixed results. The association of IES with PFMT may improve the efficacy of the latter for QoL and pad test, but the results of individual studies were not consistent. Thus, there is evidence of the use of PFMT on the treatment of SUI, with and without biofeedback.

Curving simulation and stability of a creep-controlled wheelset for high speed rail-vehicles

Higher travel speeds of rail vehicles will be possible by developing sophisticated top performance bogies having creep-controlled wheelsets. In this case the torque transmission between the right and the left wheel is realized by an actively controlled creep coupling. To investigate hunting stability and curving capability the linear equations of motion are written in state space notation. Simulation results are obtained with realistic system parameters from industry and various controller gains. The advantage of the „creep-controlled wheelset" is discussed by comparison the simulation results with the dynamic behaviour of the special cases „solid-axle wheelset" and „loose wheelset" (independent rotation of the wheels). The stability is also investigated with a root-locus analysis.

A Design Methodology for the Compensation of Positioning Deviation in Gantry Manipulators

This work presents recent results concerning a design methodology used to estimate the positioning deviation for a gantry (Cartesian) manipulator, related mainly to structural elastic deformation of components during operational conditions. The case-study manipulator is classified as gantry type and its basic dimensions are 1,53m x 0,97m x 1,38m. The dimensions used for the calculation of effective workspace due to end-effector path displacement are: 1m x 0,5m x 0,5m. The manipulator is composed by four basic modules defined as module X, module Y, module Z and terminal arm, where is connected the end-effector. Each module controlled axis performs a linear-parabolic positioning movement. The planning path algorithm has the maximum velocity and the total distance as input parameters for a given task. The acceleration and deceleration times are the same. Denavit-Hartemberg parameterization method is used in the manipulator kinematics model. The gantry manipulator can be modeled as four rigid bodies with three degrees-of-freedom in translational movements, connected as an open kinematics chain. Dynamic analysis were performed considering inertial parameters specification such as component mass, inertia and center of gravity position of each module. These parameters are essential for a correct manipulator dynamic modelling, due to multiple possibilities of motion and manipulation of objects with different masses. The dynamic analysis consists of a mathematical modelling of the static and dynamic interactions among the modules. The computation of the structural deformations uses the finite element method (FEM).