An efficient adaptive fuzzy hierarchical sliding mode control strategy for 6 degrees of freedom overhead crane

The paper proposes a new approach to efficiently control a three-dimensional overhead crane with 6 degrees of freedom (DoF). Most of the works proposing a control law for a gantry crane assume that it has five output variables, including three positions of the trolley, bridge, and pulley and two swing angles of the hoisting cable. In fact, the elasticity of the hoisting cable, which causes oscillation in the cable direction, is not fully incorporated into the model yet. Therefore, our work considers that six under-actuated outputs exist in a crane system. To design an efficient controller for the 6 DoF crane, it first employs the hierarchical sliding mode control approach, which not only guarantees stability but also minimizes the sway and oscillation of the overhead crane when it transports a payload to a desired location. Moreover, the unknown and uncertain parameters of the system caused by its actuator nonlinearity and external disturbances are adaptively estimated and inferred by utilizing the fuzzy inference rule mechanism, which results in efficient operations of the crane in real time. More importantly, stabilization of the crane controlled by the proposed algorithm is theoretically proved by the use of the Lyapunov function. The proposed control approach was implemented in a synthetic environment for the extensive evaluation, where the obtained results demonstrate its effectiveness. © 2022 by the authors. Licensee MDPI, Basel, Switzerland

Consistency of control performance in 3d overhead cranes under payload mass uncertainty

The paper addresses the problem of effectively and robustly controlling a 3D overhead crane under the payload mass uncertainty, where the control performance is shown to be consistent. It is proposed to employ the sliding mode control technique to design the closed-loop controller due to its robustness, regardless of the uncertainties and nonlinearities of the under-actuated crane system. The radial basis function neural network has been exploited to construct an adaptive mechanism for estimating the unknown dynamics. More importantly, the adaptation methods have been derived from the Lyapunov theory to not only guarantee stability of the closed-loop control system, but also approximate the unknown and uncertain payload mass and weight matrix, which maintains the consistency of the control performance, although the cargo mass can be varied. Furthermore, the results obtained by implementing the proposed algorithm in the simulations show the effectiveness of the proposed approach and the consistency of the control performance, although the payload mass is uncertain. © 2020 by the authors. Licensee MDPI, Basel, Switzerland

Theoretical basis for reasonable population distribution in Tho Chu archipelago

Tho Chu archipelago is one of administrative units of Kien Giang province, Hon Nhan- one of its islands - is selected to become A1 base point of baseline for Vietnam territorial waters. If Tho Chau district is established, it will contribute to identifying sovereignty of Vietnam Southwest sea area following the United Nations Convention on the Law of the Sea, creating favourable conditions for islands’ socio-economic development, developing culture, enhancing effects of administration work and life quality of population in this island, firmly protecting sea border, securing island and sea sovereignty… However, the establishment of Tho Chu district appears in the context of streamlining administrative apparatus and limitation of capital for infrastructure construction in district level. This article focuses on the analysis of some factors affecting a reasonable population distribution in order to meet the requirement of building the Tho Chu into a district-level administrative unit in Kien Giang province

Ectopic Pregnancy Located at Pelvic Wall and Liver: Two Uncommon Case Reports From Vietnam and Mini-Review Literature

INTRODUCTION AND IMPORTANCE: Abdominal ectopic pregnancy (AEP) located at hepatic region and pelvic-wall ectopic pregnancy (EP) are rare entities, that provoking a potentially life-threatening condition. Due to insufficient data, a proper management of non-specific types remains a challenge for all gynecologists worldwide. CASE PRESENTATION: Two child-bearing age women were hospitalized due to delayed menstruation and a urine pregnancy test was positive without a determination of intrauterine pregnancy. The first EP case was located at the pelvic wall which identified incidentally during laparoscopy for a presumed tubal ectopic pregnancy on ultrasonography throughout. The second EP case was found at the hepatic region due to intermittent pain rising from the right upper quadrant region and serial ultrasonic findings. In our management, both cases were successfully assessed by laparoscopy and laparotomy without requiring further intervention, respectively. CLINICAL DISCUSSION: An accurate diagnosis of EP location at liver and pelvic wall is totally difficult since its uncommon location. An initial assessment should be based on clinical symptoms and the treatment remains controversial. The surgical management including laparotomy and laparoscopy depends on clinical evaluation, experience of surgeon, and interdisciplinary team. Thus, these abnormal sites of ectopic pregnancy ought to take into consideration for all gynecologists in an emergency condition with a major hemorrhage. CONCLUSIONS: In reproductive age women, primary EP at liver and pelvic wall should be considered with high index of suspicion if intrauterine pregnancy is totally excluded. Timely diagnosis, rational management by surgical excision, and a multidisciplinary team can reduce substantially adverse outcomes

FIELD TEST ON CLEANING OF OIL POLLUTION ON NHATRANG BEACH OF VIETNAM

Joint Research on Environmental Science and Technology for the Eart

“I can't get it out of my mind” - Why, how, and when crisis rumination leads entrepreneurs to act and pivot during crises

Why do some entrepreneurs pivot their business models in a crisis, while others are more passive? Integrating Conservation of Resources theory with work on crisis rumination, we developed a micro-level model to explain why entrepreneurs who are under strain due to a crisis, as indicated by experiencing crisis rumination, adopt an active approach – i.e., using active coping and engaging in pivoting. Moreover, prevention-focused entrepreneurs who are habitually more sensitive to losses are especially stimulated by crisis rumination to pivot to prevent (further) resource losses. We tested our model in an experiment and an eight-month longitudinal study with entrepreneurs during an inflation crisis