Dynamic Characteristics Analysis of Two-Beam Laser Welding Robot for Fulselage Panels

Industrial robotics is becoming increasingly popular in the field of manufacturing automation. Two-beam laser welding robot which is a proprietary industrial robot of great importance to improve the welding quality of stringer-skin T-shape structure. In the process of two-beam laser cooperative welding, the robot constantly adjusts its own posture, and the position and posture of each joint would change simultaneously, which leads to the change of the natural frequency, and other dynamic characteristics of the welding robot. Based on the finite element method (FEM), the modal analysis of the robot joints in the range of motion ability and the range of motion in the process of two beam laser welding are studied, which can provide the basis for the design and accurate control of the robot with high degree of freedom (DOF). The dynamic characteristics of the whole robot in different positions and attitudes is carried out, which includes two parts, one is importance ranking of 18 joints of the robot through orthogonal test according to the range of each joint movement. The other is obtaining a plurality of time points in one welding cycle, and performing a modal analysis of the robot at each time point on the basis of the robot joints in the range of motion during the process of two-beam laser welding, the optimal number of time nodes are attained and the test workload could be reduced. The approach described herein provides a theoretical basis for robotics design and control optimization.

Mathematical simulation of the processes of two-beam laser controlled thermal-splitting of quartz glass

The paper presents the results of modeling the processes of controlled thermal cracking of quartz glass under the parallel action of two infrared laser beams of different geometries on the material: with maximum intensity in the center and with zero intensity in the center (annular section). To calculate the temperature distribution in the material, the method of Green's functions was used, which allows us to obtain a well-interpreted solution for almost any type of function of surface heat sources. Further, taking into account the quasi-static approach, using the methods of the classical theory of thermoelasticity, thermoelastic microstresses were calculated, both on the surface and in the depth of the material. It is established that the simultaneous use of these two types of laser exposure makes it possible to control the temperature field more efficiently, and create prerequisites for the most stable formation of a microcrack. The simulation results show that with a bi-beam effect, the micromechanical stresses necessary for the formation of a microcrack are realized in shorter time intervals, both on the surface and in the depth of the material, which allows increasing the processing speed by up to 30 %. Strengthening control over the process of controlled thermal cracking can significantly reduce the percentage of defects and improve the quality of the resulting microeletronics products.

Total Harmonic Distortion of a Piezoelectric MEMS Loudspeaker in an IEC 60318-4 Coupler Estimation Using Static Measurements and a Nonlinear State Space Model

We propose a method to evaluate the Total Harmonic Distortion generated by a cantilever-based PZT loudspeaker inside an IEC 60318-4 coupler. The model is validated using experimental data of a commercial loudspeaker. Using the time domain equations of the equivalent electrical circuit of the loudspeaker inside the coupler and a state space formulation, the acoustic pressure response is calculated and compared to the measurement of the manufacturer. Next, the stiffness, transduction and capacitance nonlinear functions are evaluated with a Double-Beam Laser Interferometer (DBLI) and a nanoindenter on test devices and on the commercial loudspeaker. By introducing the nonlinear functions into the model as amplitude-dependent parameters, the THD generated by the loudspeaker is calculated and compared to the value provided by the manufacturer. The good agreement between the measurement and the simulation could allow for a rather quick simulation of the performance of similarly designed loudspeakers at the early stage of the design, by only estimating the static linearity of the main nonlinearity sources.

Characterization of dissimilar aluminum-copper material joining by controlled dual laser beam

Laser technology has many advantages in welding for the manufacture of EV battery packs. Aluminum (Al) and copper (Cu) are welded using a dual laser beam, suggesting the optimum power distribution for the core and ring beams. Due to the very high reflectance of Cu and Al exposed to near-infrared lasers, the material absorbs a very small amount of energy. Compared to single beam laser welding, dual beam welding has significantly improved surface quality by controlling surface solidification. The study focused on the quality of weld surface beads, weld properties and tensile strength by varying the output ratio of the core beam to the ring beam. Optimal conditions of Al6061 were a 700 W core beam, a 500 W ring beam and 200 mm/s of weld speed. For the C1020P, the optimum conditions were a center beam of 2500 W, a ring beam of 3000 W and a welding speed of 200 mm/s. In laser lap welding of Al-Al and Al-Cu, the bead width and the interfacial bead width of the joint increased as the output increased. The penetration depth did not change significantly, but small pores were formed at the interface of the junction. Tensile tests were performed to demonstrate the reliability of the weld zone, and computer simulations provided analysis of the heat distribution for optimal heat input conditions.

ASSESSMENT OF THE THREAT OF COLLISION OF AN UNMANNED VEHICLE WITH OTHER VEHICLES BY LASER LOCATION INFORMATION

The problems of using two-beam Laser Locators (LL) on Unmanned Vehicles (UV) are analyzed. The article discusses the solution to the problem of automatic assessment of the possibility of collision of a UV with other traffic participants based on information generated by the LL. LL performs controlled scanning of the road surface at a given distance from the vehicle. To generate the error signal in the tilt angle control loop, a special filtering of the correction sequence is applied. Such filtering eliminates numerous outliers and forms a sample of correction values that do not lead to abrupt changes in the road sensing range. The modeling of the system is performed, the adequacy of which is due to the results of the conducted field experiments with a real LL. It is shown that the threat of collision arises if the vehicle speed is in a certain (dangerous) interval, the boundaries of which are functions of the following arguments: – the angle between the tangents to the trajectories of the UV and the vehicle during the LL measurements “angle-angle-range”; – distances between the UV and the vehicle at the same time interval. Tasks solved: – estimates of the angle and distances between the UV and the vehicle based on the current LL measurements “angle-angle-range”; – determination of the boundaries of the dangerous range of vehicle speeds at known UV speeds and dimensions of the UV and vehicle; – estimation of the vehicle speed according to LL measurements “angle-angle-range”. Simulation methods were used to determine the accuracy of estimates of the boundaries of the vehicle speeds dangerous range, which made it possible to create an algorithm for warning about a possible collision.

THE LASER TECHNOLOGY FOR EARTHQUAKE'S FORECAST AND FOR DIFFERENT APPROACHES OF SEISMIC HAZARD ASSESSMENT

Historically, the first laser-deformograph was developed by group of Geophysical Observatory of the Tavria National University named after I. Vernadsky (formerly Simferopol State University named after M.V. Frunze) and started to work in 1981. This laser complex allowed to carry out the measurements of the Earth’s long time deformation. The measuring volume of the observatory was located in an adit (depth of about 20 meters), which connects the right rangefinder post with the main battery structure and has a series of sealed baffles (doors, hatches) that isolate it from external influences. In the capacity of the main tools for studying oscillatory processes in the environment, the Geophysical Observatory used two-beam laser interferometers of the Michelson type with spaced beams, which have very high metrological characteristics and use the wavelength of a frequency-stabilized laser as a reference. Engineering support of the interferometric complexes’ functioning in the Geophysical Observatory was carried out by: F.N. Pankov, A.V. Buklersky, V.I. Tokarev [5].