Swing Characteristics and Vibration Feature of Tower Cranes under Compound Working Condition

The swing behaviour of tower cranes under compound working conditions is closely related to construction safety and structural health. This paper presents dynamic models and simulated them for parameter analysis to understand tower cranes’ dynamic characteristics and vibration features under compound working conditions. The parameters contain payload mass, rope length, lifting acceleration, slewing acceleration, luffing acceleration, and initial angle. For the lifting-luffing coupling motion (LLCM) and lifting-slewing coupling motion (LSCM) of the tower crane, the D’Alembert principle provides a theoretical basis for the derivation of system dynamics equations. The spatial swing angle description of the crane payload includes the time-domain response and frequency-domain response, which uses a dynamic model. The result shows that the mass has little effect on the spatial swing angle. The value of the lifting acceleration is stable at 0.004 m/s2 to 0.01 m/s2. Peak value (PV), root mean square value (RMS), root mean square frequency (RMSF), and frequency standard deviation (RVF) present the best sensitivity to changes in the spatial swing angle response. When PV of angles θ and β increases by tens of thousands of times in the LLCM, PV can reflect the phenomenon of angle divergence. The skewness value (SV) increases by 3422% at the severe swing angle performance in the LSCM. The swing angle regularity with the compound working conditions can provide theoretical guidance for eliminating structural vibration.

Simulation of Crane Trolley Motion Control to Reduce Load Sway

the work aims to develop a method for controlling a crane trolley, providing a decrease in the swinging of the load on the rope at a given positioning accuracy and minimum time for moving the load. Computer simulation of the trolley controlled movement with a load on a rope was carried out within the "Universal Mechanism" software. The 2D computer model includes a trolley with a pulley, a rope with a hook, and a load. T-force represents the wind force effect. The control system (CS) contains three blocks that ensure the movement of the trolley with limited speed and acceleration, the positioning accuracy of the trolley, limiting the deviation and acceleration of a load. List of requirements for the crane CS comprises six issues. The simulation results illustrate the satisfactory performance of the proposed method. The swing angle and trolley positioning accuracy can be controlled within the acceptable range and the external wind disturbance on the load can be successfully suppressed. The optimal parameters of the proportional-differential corrective control, which ensure the minimum travel time of the trolley with limited oscillation of the load, have been determined. The optimal values of the control parameters depend on the inertial characteristics of the load. The maximum permissible values of speed, acceleration, and positioning errors of the trolley limit from above the optimal values of the control parameters.

Research on Simulation Calculation of the Safety of Tight-Lock Coupler Curve Coupling

Once a train breaks down on a busy railway line, it will affect the whole traffic network. However, when a rescue locomotive is hooked up to the broken train for towing it to the next station, it is common that coupling dislocation occurs, which results in damages to couplers and the driver’s cab. To ensure the safety of the trains during the coupling, it becomes crucial to determine whether they can be linked safely and automatically under different line conditions. In this paper, position and pose of the rescue locomotive and the broken train on the line are calculated by geometric analytical calculation method, which determines the position relation of their couplers. Then a so-called “coupling characteristic triangle” was proposed to determine whether trains can be safely and automatically linked on the railway line. The triangles are constructed by the peak points of the couplers head of the front vehicle and the rear one and border lines of secure coupling area on the couplers. By judging the shape of the triangle, it can directly judge whether their couplers can be connected successfully. The method has been applied to check the safety of the trains during coupling on the Nanchang urban railway Line 4. The results show that the maximum swing angle of the coupler reaches 17.3957° in the straight–curve section with a radius of 325 m. At this time, coupling is most difficult, and trains need to be connected manually through the tractor; all the calculation results are verified in the actual line. By comparing different calculation methods for judging coupling safety, it is shown that the method proposed in this paper is accurate, efficient, and users can judge coupling safety more intuitively.

A New Payload Swing Angle Sensing Device and Its Accuracy

Measuring the swing angle of a crane load is a relatively well-known but unsatisfactorily solved problem in technical practice. This measurement is necessary for the automatic stabilization of load swing without human intervention. This article describes a technically simple and new approach to solving this problem. The focus of this work is to determine the accuracy of the measuring device. The focus of this work remains on the design, the principle of operation of the equipment, and the determination of accuracy. The basic idea is to apply the strain gauge on an elastic, easily deformable component that is part of the device. One part of the elastic component is fixedly connected to the frame; the other part is connected to the crane rope by means of pulleys close to the rope. In this way, the bending of the elastic component in proportion to the swing angle of the payload is ensured.

Analisis biomekanika free throw basket sesuai kaidah Dave Hopla

Penelitian ini bertujuan untuk menganalisis gerakan free throw sesuai dengan kaidah Dave Hopla. Metode penelitian ini menggunakan eksperimen dengan teknik tes dan pengukuran. Total sampel berjumlah 5 atlet PPLP Basket Kota Semarang yang telah mengisi inform consent dan menyetujui prosedur penelitian. Hasil penelitian ini didapatkan rata rata waktu pada tahap persiapan sebesar 0,53 ± 0,13 detik dengan sudut ayunan sebesar 120°. Gerakan awalan sudut lengan 90° dan rata rata waktu 0,25 ± 0,04 detik dengan sudut fleksi lutut sebesar 99,04 ± 0,04 derajat. Data pada tahap pelaksanaan untuk waktu yang diperoleh sebesar 0,29 ± 0,07 detik dengan sudut fleksi lengan sebesar 55,74 ± 5,54 derajat sedangkan pada tahap akhir dengan rata rata waktu 0,24 ± 0,04 detik dengan jarak shooting 3,64 ± 4,64 meter. Kesimpulan dalam penelitian ini menunjukkan bahwa gerakan free throw sudah sesuai dengan kaidah dari Dave Hopla. Hasil free throw juga menunjukkan bahwa shooting precision pada kategori Cukup. Keterbatasan dalam penelitian ini yaitu jumlah sampel yang sedikit terkendala pembatasan social pada masa pandemic Covid-19. Penelitian selanjutnya diharapkan bahwa kaidah Dave Hopla dapat dijadikan sebagai rujukan dalam melakukan free throw untuk efektivitas dan efisiensi gerakan serta akurasi shooting.Biomechanical Analysis of Basketball Free Throw According to The Rules of Dave HoplaAbstractThis aims of this study was to analyze the free throw motion according to Dave Hopla's rules. This research method uses descriptive quantitative with survey tests and measurements. The total sample consisted of 5 PPLP Basket athletes in Semarang who had filled the informed consent and approved the research procedure. The results of this study found an average time in the preparation phase was 0.53 ± 0.13 seconds with a swing angle of 120°. The prefix movement of the arm angle was 90° and an average time was 0.25 ± 0.04 seconds with a knee flexion angle of 99.04 ± 0.04 degrees. The data at the implementation phase for the time obtained were 0.29 ± 0.07 seconds with an arm flexion angle was 55.74 ± 5.54 degrees while in the follow through phase an average time was 0.24 ± 0.04 seconds with a shooting distance of 3.64 ± 4.64 meters.The conclusion of this study showed that the free throw motion is in accordance with Dave Hopla's rules. The free throw result also showed that the shooting precision is in the Moderate category. The limitation in this study was the sample size is slightly constrained by social restrictions during the Covid-19 pandemic. Further research is expected that Dave Hopla's rule can be a reference in making effective and efficient free throws.

Dynamical behavior of coal shearer under the influence of multiple factors in slant-cutting conditions

Aiming at the problem of severe vibration and abnormal wear and tear of various components in coal shearer under slant-cutting conditions, a non-linear dynamics model with 13 degrees of freedom for a coal shearer under slant-cutting conditions is developed using vibration mechanics and multi-body dynamics theory, and the characteristics of the slide shoes-middle groove contact, the ranging arm-haulage unit connection with gaps and the guidance sliding boots-pin rail multi-surface contact with gaps are described based on three-dimensional fractal theory and Hertz contact theory. Based on Huco's law, the ranging arm and the hydraulic rod are assumed to be flexible beams, the rigidity characteristics of the ranging arm itself, the connection characteristics of the haulage unit and the fuselage are described, a drum correction load with a traction speed correction factor is proposed as the external excitation of the system, and the model is solved and analyzed. The research results show that the change of traction speed has a greater influence on the vibration swing angle and displacement of the front drum, front ranging arm and front walking unit, and the vibration swing angle and displacement of the three increase with the increase of traction speed, while the change of coalface hardness coefficient has less influence on the vibration displacement of the key components of the coal shearer. Under the working parameters of v = 3 m/min and f = 3, the swing angle and displacement of the front ranging arm and front drum fluctuate in the ranges of − 0.4–0.1 rad and – 15–15 mm respectively; the vibration acceleration is – 300–300 rad/s2 and – 200–200 mm/s2 respectively, the main vibration frequencies are 16.63 Hz and 12.14 Hz respectively, and finally the results are verified by experimental methods.