In the previous study, a visually servoed paired structured light system (ViSP) which is composed of two sides facing each other, each with one or two lasers, a 2-DOF manipulator, a camera, and a screen has been proposed. The lasers project their parallel beams to the screen on the opposite side and 6-DOF relative displacement between two sides is estimated by calculating positions of the projected laser beams and rotation angles of the manipulators. To apply the system to massive civil structures such as long-span bridges or high-rise buildings, the whole area should be divided into multiple partitions and each ViSP module is placed in each partition in a cascaded manner. In other words, the movement of the entire structure can be monitored by multiplying the estimated displacements from multiple ViSP modules. In the multiplication, however, there is a major problem that the displacement estimation error is propagated throughout the multiple modules. To solve the problem, propagation error minimization method (PEMM) which uses Newton-Raphson formulation inspired by the error back-propagation algorithm is proposed. In this method, a propagation error at the last module is calculated and then the estimated displacement from ViSP at each partition is updated in reverse order by using the proposed PEMM that minimizes the propagation error. To verify the performance of the proposed method, various simulations and experimental tests have been performed. The results show that the propagation error is significantly reduced after applying PEMM.
Currently, the maintenance or inspection of large structures is labor-intensive, so it has a problem of the large cost due to the staffing professionals and the risk for hard to reach areas. To solve the problem, the needs of wall-climbing robot are emerged. Infra-based wall-climbing robots to maintain an outer wall of building have high payload and safety. However, the infrastructure for the robot must be equipped on the target structure and the infrastructure isn’t preferred by the architects since it can injure the exterior of the structure. These are the reasons of why the infra-based wall-climbing robot is avoided. In case of the non-infra-based wall-climbing robot, it is researched to overcome the aforementioned problems. However, most of the technologies are in the laboratory level since the payload, safety and maneuverability are not satisfactory. For this reason, aerial vehicle type wall-climbing robot is researched. It is a flying possible wallclimbing robot based on a quadrotor. It is a famous aerial vehicle robot using four rotors to make a thrust for flying. This wall-climbing robot can stick to a vertical wall using the thrust. After sticking to the wall, it can move with four wheels installed on the robot. As a result, it has high maneuverability and safety since it can restore the position to the wall even if it is detached from the wall by unexpected disturbance while climbing the wall. The feasibility of the main concept was verified through simulations and experiments using a prototype.
To inspect structural conditions, structural displacement is needed to be monitored at any time. Therefore, our previous
study proposed a ViSP (Visually Servoed Paired structured light system) which is composed of two sides facing with
each other, each with a camera, a screen, and one or two lasers controlled by a 2-DOF manipulator. In this system, the
relative translational and rotational displacement between two sides can be estimated by calculating positions of the
projected laser beams on the screens and the rotation angles of the manipulators. To validate the performance of the
system, the various experimental tests with a two-story structural model were performed. The estimated results were
compared with the results from a laser displacement sensor which can be considered as a reference. The results show that
the presented system has potential of estimating the response of the structures with high accuracy in real time.
An efficient design analysis method for cantilevered beam-type piezoelectric energy harvesters was developed for the
prediction of the electric power output, based on the finite element method and the design optimization of piezoelectric
materials. The optimum topology of a piezoelectric material layer could be obtained by a newly developed topology
optimization technique for piezoelectric materials which utilized the electromechanical coupling equations, MMA
(method of moving asymptotes), and SIMP (solid isotropic material with penalization) interpolation. Using the design
optimization tool, several cantilevered beam-type piezoelectric energy harvesters which fluctuated in the region of vortex
shedding were developed, that consisted of two different material layers - piezoelectric and aluminum layers. In order to
obtain maximum electric power, the exciting frequency of the cantilevered energy device must be tuned as close to the
natural frequency of the beam as possible. Using the method, the effects of geometric parameters and several
piezoelectric materials (PZT, PVDF, and PZT fiber composites) attached to the beam device on power generation were
investigated and the electric characteristics were evaluated. The three kinds of material coefficients such as elasticity,
capacitance, and piezoelectric coupling are interpolated by element density variables. Then, the shape and size design
optimizations for the cantilevered beam geometries with an optimum piezoelectric topology have been performed for a