Control of a hovering quadrotor UAV subject to periodic disturbances

Quadrotor is a rotary-wing UAV, which has a simple structure but highly nonlinear dynamics. Controlling a hovering quadrotor subject to external disturbances is a crucial task in many applications. In this paper, periodic disturbances have been tackled and novel disturbance observers (DOB) have been developed to estimate the total disturbance acting on the vehicle. It is especially difficult to reject periodic disturbances in low as well as in high frequency region due to the bandwidth limitations of the low-pass filter utilized in conventional DOB. As the cutoff frequency of the low-pass filter is critical, increased bandwidth reduces the robustness which degrades the disturbance rejection performance in the presence of noise. In addition to the low-pass filter, the new structure also consists of a bank of band-pass filters and a high-pass filter. Since the total disturbance acting on the vehicle is compensated by the proposed DOB, PD controllers with feedforward terms are utilized for stabilizing both position and attitude dynamics. Simulation results show the improved robustness obtained by the proposed method

Nonlinear adaptive control of an aerial manipulation system

This paper presents the nonlinear adaptive control of a quadrotor endowed with a 2 degrees of freedom (DOF) manipulator. By considering the quadrotor and the robot arm as a combined system, complete modeling of the aerial manipulation system (AMS) has been presented using the Euler-Lagrange method. A hierarchical nonlinear control scheme which consists of outer and inner control loops has been utilized. Model Reference Adaptive Controller (MRAC) is designed for the outer loop where the required command signals are generated to force the quadrotor to move on a reference trajectory in the presence of uncertainties and reaction forces coming from the manipulator. For the inner loop, the attitude dynamics of the quadrotor and the dynamics of the 2-DOF robotic arm are considered as a fully actuated 5-DOF unified part of the AMS. Nonlinear adaptive control has been utilized for the low-level controller where the changes in inertias and the masses have been tackled along with the reaction forces acting on the attitude part of the AMS. The proposed technique has been validated through simulations in two different scenarios

The Extent of the Impact of the Displacement Crisis and Its Reflections on the Psychological Health and Behavioral Status on Secondary Stage of Displaced Students in Kurdistan Region- Iraq

The current study aimed at identifying the extent of the impact of the displacement crisis and its reflections on the psychological health and behavioral status on secondary stage of displaced students by an intended sample of displaced students in the northern Iraqi city of Dohuk. The sample of study included 700 secondary school male and female students from 12 to 18 years old, displaced from areas under the control of ISIS such as Al-Mosul, Falluja, Ramadi and Biji, in addition,  85 male and female teachers in the displaced schools, and 50 parents (mothers, fathers and relatives such as uncles). To achieve the goal of the study, both researchers prepared three questionnaires, one for students, the second for teachers. Moreover, a questionnaire answered by the students’ parents, whether they were mothers and fathers or family members. Study tends to use different approaches according to different contexts to serve study purposes.As the study begins with a theoretical background about psychological health and the behavioral status, and it uses both analytical and descriptive approaches. Both approaches were merged in some places, particularly when analyzing the results of the questionnaires and explaining the status of the interviews. he results of the study showed the negative effects on the psychological and behavioral conditions of the students, as the prevalence of psychological trauma is different intensity among them, as a result of their witnesses of severe forms of violence, ranging from watching clashes and missiles through television and social media sites, to the cases of death of a family member in front of their eyes, as a result of violence action, and the number of students who feel depressed, frightened and pessimism from the future. They think about leaving Iraq. The impact of these shocks ranges from the incoherence of some of them besides their losing their relationships with their friends, and even sometimes they think about leaving their country, in addition to the increase of their violence and aggression, their disobeying rules whether at school or at home, as well as the weakness of many moral values. This matter creates violent reactions for the educators and those who care for the students at school and at home, in addition to the weakness of their economical status and poverty. The study recommends building a strategic plan based on the Human Rights Agreement which guarantees the displaced students’ rights in learning, and it emphasizes on the necessity of building parallel remedial programs that guarantee the continuity of offering support at school and at home

Control of a hovering quadrotor UAV subject to periodic disturbances

Quadrotor is a rotary-wing UAV, which has a simple structure but highly nonlinear dynamics. Controlling a hovering quadrotor subject to external disturbances is a crucial task in many applications. In this paper, periodic disturbances have been tackled and novel disturbance observers (DOB) have been developed to estimate the total disturbance acting on the vehicle. It is especially difficult to reject periodic disturbances in low as well as in high frequency region due to the bandwidth limitations of the low-pass filter utilized in conventional DOB. As the cutoff frequency of the low-pass filter is critical, increased bandwidth reduces the robustness which degrades the disturbance rejection performance in the presence of noise. In addition to the low-pass filter, the new structure also consists of a bank of band-pass filters and a high-pass filter. Since the total disturbance acting on the vehicle is compensated by the proposed DOB, PD controllers with feedforward terms are utilized for stabilizing both position and attitude dynamics. Simulation results show the improved robustness obtained by the proposed method

Effect of Chemical Solutions on Some Mechanical Properties of (Fe + Cu/UPE)

This research includes the preparation of polymeric composites by (Hand lay-up method) of unsaturated polyester resin as a matrix material and (iron, copper) particles as strengthening materials with different weight ratios (5%, 10%, 15%, 20%). The hardness and impact strength properties are studied before and after immersion in (NaOH) solution and (HCl) solution at a normality of (0.3N) and for a period of one immersion (30 days). The results showed that the hardness and impact values increased with the increase in the percentage of iron and copper before immersion, after immersion, that hardness and impact strength values increased with increasing the iron and copper ratio of the compounds For all samples, but their value was lower than in normal conditions. And also these values in the (HCL) solution were lower than the (NaOH) solution

Redundant kinematics and workspace centering control of AssistOn-Gait overground gait and balance trainer

We present the redundant kinematics and workspace centering control of AssistOn-Gait, an overground gait and balance trainer designed to deliver pelvis-hip exercises to correct compensatory movements arising from abnormal gait patterns. AssistOn-Gait consists of an impedance controlled pelvis-hip exoskeleton module, supported by a motion controlled holonomic mobile platform. The exoskeleton module possesses 7 active degrees of freedom to independently control the rotation of the each hip in the sagittal plane along with the pelvic tilt, pelvic rotation and the horizontal, vertical and lateral displacements of the pelvis. The holonomic mobile base can track the movements of patients on flat surfaces, allowing patients to walk naturally, start/stop motion, vary their speed, sidestep to maintain balance and turn to change their walking direction. The kinematics of AssistOn-Gait is redundant, as the exoskeleton module spans all the degrees of freedom covered by the mobile platform. The device features dual layer actuation, since the exoskeleton module is designed for force control with good transparency, while the mobile base is designed for motion control to carry the weight of the patient and the exoskeleton. The kinematically redundant dual layer actuation enables the mobile base of the system to be controlled using workspace centering control strategy without the need for any additional sensors, since the patient movements are readily measured by the exoskeleton module. The workspace centering controller ensures that the workspace limits of the exoskeleton module are not reached, decoupling the dynamics of the mobile base from the exoskeleton dynamics. Consequently, AssistOn-Gait possesses virtually unlimited workspace, while featuring the same output impedance and force rendering performance as its exoskeleton module

Trajectory control of a quadrotor using a control allocation approach

A quadrotor is an underactuated unmanned aerial vehicle with four inputs to control the dynamics. Trajectory control of a quadrotor is a challenging task and usually tackled in a hierarchical framework where desired/reference attitude angles are analytically determined from the desired command signals, i.e. virtual controls, that control the positional dynamics of the quadrotor and the desired yaw angle is set to some constant value. Although this method is relatively straightforward, it may produce large and nonsmooth reference angles which must be saturated and low-pass filtered. In this work, we show that the determination of desired attitude angles from virtual controls can be viewed as a control allocation problem and it can be solved numerically using nonlinear optimization where certain magnitude and rate constraints can be imposed on the desired attitude angles and the yaw angle need not be constant. Simulation results for both analytical and numerical methods have been presented and compared. Results for constrained optimization show that the flight performance is quite satisfactory

Bacteriocin-mediated inhibition of some common pathogens by wild and mutant Lactobacillus species and in vitro amplification of bacteriocin encoding genes

Lactobacilli are the most common probiotics used in food and other industries because of their capability of producing bacteriocins. Bacteriocins are compounds that are used to kill pathogenic microorganisms. As most bacteria have become resistant to synthetic antibacterial tools, the importance of using probiotics as antibacterial agents has increased. This work was done to check the bacteriocin effect on some common pathogens and the influence of mutation on the bacteriocin activity of Lactobacilli was also investigated. Four strains were isolated, identified from meat and pickles samples via culturing methods, staining, biochemical tests, and ribotyping. Preliminary tests, including Gram staining and catalase test, were done for the confirmation of Lactobacillus species. All strains were gram-positive and catalase-negative. Antibacterial activity was checked against Pseudomonas aeruginosa, Staphylococcus aureus, Bacillus thuringiensis, Escherichia coli, and Salmonella enteritis via agar well diffusion method. The mutations were done using ethidium bromide and the influence of wild and mutants were also checked. Interestingly, mutants developed more virulence than wild ones. It was also observed that they all were sensitive to pepsin. Protein estimation was done via Bradford method. Ribotyping of GCU-W-PS1 revealed 99 % homology with Lactobacillus plantarum and GCU-W-MS1 to Lactobacillus curvatus (99 % homology). Curvacin A, sakacin P, and plantaricin A genes were also amplified using specific primers. Gene sequence showed the presence of curvacin A gene in GCU-W-MS1. It was concluded that lactic acid bacteria could be used as antibacterial tools against common pathogens

Effect of age on some renal function tests, uric acid, and gamma glutamyl transferase (GGT) in sample of Iraqi men over 40 years

Background: The prevalence of some aging markers that is part of metabolic syndrome elements are increasing worldwide, and the renal function is a major goal of this syndrome. Aim: To correlate the age with some renal function tests (blood urea and serum creatinine), serum uric acid (S.UA) and serum gamma glutamyl transferase (S.GGT).Material and methods: This study involve 127 men apparently healthy (≥ 40 years old) were analyzed for blood urea, serum creatinine, uric acid and gamma glutamyl transferase by the spectrophotometer methods by use the previously prepared kits from linear chemicals company.. Results: The mean age of men was (55.535±10.738)years. The men under study were divided into four groups according to age: 46 men (36.22%) their age range were ≥40 years, 33 cases (25.984%), 28 case (22.047%) and 20 others (15.748%) were (50-59), (60-69) and (≥70) years respectively. The mean ± Std. Deviation of variables in study were B. urea (42.387±3.682) mg/dl, S. creatinine (1.004±0.158) mg/dl, S.UA (6.216±0.829) mg/dl, and S.GGT (28.844±7.741) U/l. Older age was significantly associated with increased in B. urea and S. creatinine, while no significant association was found between age and S.UA and S.GGT in Iraqi men at (P ≤0.05 for all factors).Conclusions: older men are more liable to have higher B. urea and S. creatinine, with no relation between age and the levels of both uric acid and GGT in serum of Iraqi men under study