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Abstract The mobile robot market is experiencing rapid growth, playing a pivotal role in various human-centric environments like restaurants, offices, hotels, hospitals, apartments, and factories. However, current differential-driven mobile robots, employing conventional casters and wheel motors, encounter limitations in surmounting uneven surfaces and high steps due to constraints caused by wheel and caster dimensions. While some robots address these challenges by incorporating optimized wheel shapes and additional motors, this invariably leads to an increase in both size and cost. This research introduces an innovative solution; a novel caster-wheel mechanism designed to enhance the high-step overcoming capability of mobile robots without necessitating alterations to their overall size and structure. By incorporating a sub-wheel linked to a passive joint, the driving force is effeciently converted into a vertical force, thereby empowering the mobile robot to navigate obstacles 85% larger than its caster-wheel radius. Crucially, this innovative caster can be seamlessly manufactured and integrated, offering the potential for widespread adoption as a replacement for conventional casters. Validation through comprehensive simulations and experiments conducted on a prototype robot has been presented in this article, demonstrating its effectiveness even at a robot velocity of 0.1 m/s. This pioneering solution holds significant promise for diverse applications across various mobile robot configurations, presenting a compelling avenue for further exploration and implementation in the field.

Abstract In general, sanding robots that move as if drawing a line along a surface are mainly used when sanding objects with a large area; however, they require a long working time, and it is difficult to secure a uniform sanded area. This study focuses on large-area sanding robots, such as those for ships, storage tanks, and tank lorries, and proposes an adaptive belt tension robot equipped with a 4-point supported belt mechanism capable of sanding variable curved surfaces. In addition, a sanding normal force prediction formula is proposed to describe the sanding performance of the contact surface. This equation consists of the concentrated load function due to the belt movement and the normal force due to the vertical and horizontal elongation of the belt. A video image analysis was performed to calculate the sanding area. Therefore, we determined whether the area was uniformly sanded. The dimensions of the test bench (W $$\times $$ × D $$\times $$ × H) were 1700 mm $$\times $$ × 1450 mm $$\times $$ × 900 mm. Experiments were performed using the proposed techniques on convex specimens with radii of 725, 1000, and 2100 mm. The sanding performance was improved by 43 $$\%$$ % compared with that of a general belt-sanding robot.

Abstract This paper introduces a novel design and static optimization for a two-degrees-of-freedom transformable wheel based on a geared linkage mechanism. Overcoming obstacles, including stairs, with small wheels is a major challenge in the field of mobile robotics research. Among various robots, the transformable wheel, which can change the shape of the wheel to overcome steps and optimize the path, was presented and has undergone many improvements. Nevertheless, problems such as asymmetry and structural strength remain. Therefore, the design of this paper aims to address the structural inefficiencies identified in the previous research model, which were attributed to the asymmetric placement of the linear motion guide. Through the implementation of this mechanism, the linear motion of the lobe can be segregated, enabling each input motor to share the workload effectively. The optimization process focus on determining the optimal linkage length under static conditions, resulting in improved structural characteristics and force distribution of linkage within the designated workspace. As a result, asymmetry of motion is eliminated, required intervention angle of the driving motor and stress of linkage was reduced by 36.24% and 8.35%, respectively.

Existing state-of-the-art stair climbing robots require precise control through many sensors and actuators to climb various stairs. In this study, we propose WAVES, a stair-climbing robot that can climb a variety of stairs with minimal electronic components and control. WAVES’ stair climbing ability is due to its soft part on the bottom, which adapts passively to the shape of the stairs. The soft parts were fabricated into a compliant mesh shape and could be freely deformed according to the shape of the stairs. We used the ratio of horizontal and vertical reaction forces that occur when the soft part is deformed as an index to determine stability, and the simulation results showed that the arc shape has the smallest horizontal reaction force ratio of 0.224 (honeycomb: 0.303, spoke: 0.276). Also, to determine the appropriate strength of the soft parts, we calculated the maximum compressive force that each section of the soft part should withstand. Based on the calculation results, we made the gap between arc patterns closer where the strong compressive force is applied. In conclusion, before applying soft parts to the robot, the diagonal length of the stairs it could climb was 328.7 mm–350 mm, but after applying soft materials, it can climb all stairs under 400 mm.

Abstract This study proposes a variable-stiffness mechanism for non-pneumatic tires such that can actively adapt to various environments. Non-pneumatic tire is a compliant wheel structure that offers superior robustness and adaptability compared to pneumatic tires. However, the tire designed for certain terrain exhibits relatively high rolling resistance and inadequate suspension. To address these problems, a stiffness-adjustable wheel (SAW) that can modify the force applied to the contact surface is introduced in this study. In addition, the shape of SAW is optimized to maintain a desirable range of stiffness under different conditions. The optimization is conducted with experimental method, because nonlinear response of material and interference between components make it difficult to predict the characteristic of the wheel at large deformation. The SAW has potential for application in various mobile platforms to provide adequate stiffness for a variety of terrains and driving conditions.

Abstract Navigation in terrains mixture of rigid support and granular media is associated with slippage. It is important to find the optimal path because slippage implies the possibility of a mobile robot being stuck in the sand. This research introduce concept of effective distance which consider effect of slippage to present a path planning algorithm. Effective distance is a conceptual distance that the mobile robot traverse to reach next node, and it is calculated based on traversable difficulty. Traversable difficulty varies with the slope angle, and the revolution speed of the angled spoke-based wheel (ASW) is estimated using meta-model. The meta-model is achieved empirically. Experiments have done in testbench which can implement slope angle and terrain types. Effectiveness of this algorithm was verified through simulation. For the simulations three cost determination methods, namely, the effective distance with varying revolution speed of the ASW, the effective distance with fixed revolution speed of the ASW, and actual distance were examined in four different scenarios. The effective distance with varying revolution speed of the ASW has maximum $$135.94\%$$ 135.94 % longer total actual distance. However, it results minimum $$44.72\%$$ 44.72 % shorter total effective distance.

Abstract This paper presents the analysis of ropes’ bending on three-dimension edges by ascending robots. A rope ascending robot (RAR) is a type of exterior wall-working robot that utilizes a synthetic rope to traverse the outer surface of a building. Rope-based façade cleaning robots demonstrate effective performance in well-structured buildings. However, in unstructured buildings, the rope used by these robots may become entangled or caught on various structures, presenting a significant challenge for their operation. If the rope becomes caught on a structure, the robot will be unable to move to its intended position. In more severe cases, the rope may become damaged, leading to potential failure or even a fall of the robot. Therefore, solving this problem is crucial for safe and efficient robot operation. Consequently, this study defines the issue of the rope becoming caught on a structure as a rope-locking problem and analyzes it by categorizing it based on the dimensions of contact between the rope and the edge. To address the varying tension experienced in different areas, the rope was divided into micro units and subjected to a three-dimensional analysis to resolve the rope-locking problem. Additionally, the analysis was verified by experiments.

Indoor service robots have been widely introduced in the fields of cleaning, delivery, education, guidance, and healthcare, etc. in indoor environments. The mobility of an indoor service robot is essential to expanding its applications. However, the mobility of existing indoor service robots is highly limited by surrounding indoor environments. For example, a stair is one of the major obstacles that restrict the reachable areas of indoor service robots. Even though many studies have been performed to develop reliable and fast stair-climbing robots based on legged, tracked, wheel-legged and wheel-linkage mechanisms, a market-dominant stair-climbing robot remains unsolved. This review investigates the efforts of engineers devoted to stair-climbing robots. To this end, the locomotion mechanisms of stair climbing robots are classified and their sensing method are summarized. In this review, we also propose useful criteria for evaluating the stair-climbing ability of an indoor service robot. By virtue of these criteria, the stair-climbing performance of existing robots are qualitatively compared. We hope this review helps develop the reliable and fast stair-climbing robots and the reasonable criteria for their performances.

During the operation of a nuclear power plant (NPP), the waste reactor vessel closure head (RVCH) that is replaced owing to design or manufacturing defects is buried in a designated area or temporarily stored in a radiation shielding facility within the NPP. In such cases, storing it for extended periods proves a challenge owing to space constraints in the power plant and a safety risk associated with radiation exposure; therefore, dismantling it quickly and safely is crucial. However, not much research has been done on the dismantling of the RVCH in an operational power plant.This study proposes a dismantling process based on the radioactive contamination level measured for the Kori #1 RVCH, which is currently being discarded and stored, and examines the decontamination and cutting according to this process. In addition, the amount of secondary waste and dismantling cost are evaluated, and the dismantling effect of the reactor closure head is analyzed.

Abstract The development of the maritime industry has led to a corresponding increase in maritime accidents. Maritime accidents are major events that are costly to recover and can cause casualties. Moreover, individuals who are brought to the scene for recovery or rescue are at risk. To tackle this issue, the wheel mechanism of a water rescue robot, i.e., the angled spoke paddling wheel (ASPW), has been studied. The purpose of this study is to optimize the paddle design parameters of the ASPW using the Taguchi method. Experiments are conducted by creating paddles with various combinations of design parameters using $${\textbf{L}}_9$$ L 9 ( $$3^4$$ 3 4 ) orthogonal arrays. The objective function is determining the optimal combination of paddle design parameters that will produce the greatest thrust force at the same RPM. Sensitivity analysis of each design parameter is conducted by calculating the signal-to-noise ratio from the experimental results. The pitch angle is found to be the most sensitive parameter. An additional experiment is conducted based on the results of the sensitivity analysis. The results show that the optimal design parameters are a pitch angle of $$0^{\circ }$$ 0 ∘ , rectangular end shape, X-axis curvature of 37.5 mm, and Y-axis curvature of 25 mm. The paddle with this combination of design parameters have a maximum thrust force of 64.74 gf at 120 RPM and exhibit up to an 18.27% improvement in performance compared with the initial paddle before optimization.

Abstract Stair climbing is one of the most important capabilities of mobile robots. Therefore, stair-climbing mobile robots have become a field of study and diverse stair-climbing mobile robots have been developed. Although tri-wheel-based stair-climbing robotic platforms were developed to overcome the challenges posed by stair climbing, they have shown limitations such as impact during locomotion and damage owing to friction with the nosing of the stairs. In this study, several tail mechanisms were proposed and designed to solve the limitations of tri-wheel-based stair-climbing robots. A comparative analysis of the tail mechanisms was performed through dynamic simulations based on various performance indices. It was observed that the tail mechanism improved the stability and stair-climbing performance of the tri-wheel-based stair-climbing robots. The experimental verification confirmed the reliability of the comparative analysis results based on the simulation. These findings can be used to design mobile stair-climbing robots.

Abstract This paper presents the design optimization of a linkage-based wheel mechanism with two degrees of freedom, for stable step climbing. The mechanism has seven rotational joints and one prismatic joint. Kinematic and dynamic analyses of the mechanism were performed. The design was optimized in terms of linkage length and architecture to better manipulate the mechanism in its workspace, which was defined here by the targeted step size, as well as to ensure stability while climbing stairs. Optimization by genetic algorithm was performed using MATLAB. The optimized mechanism exhibited enhanced torque transmission from the input torque to the exerted for at the lobe of the wheel. Compliance control of the transformation will be addressed in the future.

Abstract A novel detachment method is presented for flexible substrates from glass carrier wafers using a CO2 point laser. In a conventional laser lift‐off process, laser‐induced illumination and thermal stress degrade device performance. In this approach, a point laser is applied on the edge of the flexible substrate, where electrical components do not exist, and thus, no performance degradation occurs during the laser process. In addition, the carrier surface properties are modified to control the adhesion force between the flexible substrate and the glass carrier. A spin‐on‐dielectric layer (SOD) is utilized, and Ar ion bombardment is performed on SOD. The point laser detachment method is demonstrated in flexible thin‐film transistors, and no change is observed in the electrical characteristics before and after detachment from the carrier wafer.

Abstract Recent years, there has been an increase in the number of high-rise buildings, and subsequently, the interest in external wall cleaning methods has similarly increased. While a number of exterior wall cleaning robots are being developed, a method to detect contaminants on the exterior walls is still required. The exteriors of most high-rise buildings today take the form of a window curtain-wall made of translucent glass. Detecting dust on translucent glass is a significant challenge. Here, we have attempted to overcome this challenge using image processing, inspired by the fact that people typically use just the ‘naked eye’ to recognize dust on windows. In this paper, we propose a method that detects dust through simple image processing techniques and estimates its density. This method only uses processing techniques that are not significantly restricted by global brightness and background, making it easily applicable in outdoor conditions. Dust separation was performed using a median filter, and dust density was estimated through a mean shift analysis technique. This dust detection method can perform dust separation and density estimation using only an image of the dust on a translucent window with blurry background.

In this study, the unscented Kalman filter-based method was introduced as a new technique for position estimation of the two-degree-of-freedom façade cleaning robot known as the Dual Ascender Robot (DAR). While other façade cleaning robots use a winch, the DAR uses an ascender, resulting in rope slip inside the ascender. Rope slip does easily cause errors in length data, so DARs cannot be easily controlled based on length data as in the case of most façade cleaning robots. Therefore, the DARs estimate the length data and use it through position estimation to overcome the rope slip for control. DARs use a rope length-based sensor fusion method for position estimation. This method employs position data based on both length data and angle data to estimate the position; however, it is difficult to use for long periods of time owing to the increased error that accumulates with time. Therefore, the use of position data based on angle data is proposed herein via application of the unscented Kalman filter. This unscented Kalman filter-based method is tested to confirm that the positional estimation performance is improved relative to that achieved via the previously used method. The performance improvements are compared in terms of accuracy and repeatability using the double ball bar method, and the errors in accuracy and repeatability are found to be reduced by approximately 2-3 times.

This study presents a novel shape-morphing wheel that enables to not only traverse flat ground quickly in a circular configuration but also overcome obstacles like steps effectively in a transformed configuration. The proposed wheel mechanism has two degrees-of-freedoms (DOFs) to change its wheel radius and the tilting angle of its lobe simultaneously in response to obstacles of various sizes. The kinematic requirements for the 2-DOF shape-morphing wheel mechanism are first defined. Then, the proper mechanisms for the proposed wheel mechanism are exhaustively searched. As a result, five mechanisms are selected in combination with four-bar mechanism to synchronize the motions of wheel lobes. From the kinematic viewpoints including the singularity, transformation range and interference, the characteristics of selected mechanisms are analyzed extensively, and a novel 2-DOF shape-morphing wheel mechanism has been successfully constructed.

In this paper, a robust design of a screw wheel is presented, based on the Taguchi method to accelerate a screw-based crawling robot. Screw-based crawling robots have been studied before, but their application is limited because of their limited speed. To solve this problem, robust design is applied for the screw wheel geometry driving on granular surfaces, such as desert sand, which has not been studied before. Each of the four parameters determining the screw wheel geometry and two user conditions were set at three levels, and the Taguchi method was applied through the $L_{9}(3^{4})$ orthogonal array. The experimentally optimized parameters were as follows: the slope angle was 35°, the height of the blade was 14 mm, the number of spirals was one, and the blade had a semicircular cross-section. A verification experiment was conducted with the optimized model to verify the Taguchi method’s validity. In conclusion, the robust design using the Taguchi method is suitable for solving the speed problem of a screw-based crawling robot on a granular surface.

In this paper, a mechanism for overcoming high obstacles is proposed to broaden the application range of the exterior wall cleaning robot. The proposed one-degree-of-freedom wheel mechanism can overcome high obstacles by the rotation of a wheel with two different spoke lengths. To implement the inclined tilted wheel (ITW), two design variables were studied - a spoke assembly angle and a wheel shaft assembly angle. At the critical assembly angles of $\varphi = 45^{\circ }$ and $\theta = 135^{\circ }$ , the characteristics of the generated wheel trajectory does not invade the upper and lower space of the robot. From the trajectory, the space efficiency can be secured for thrust unit cleaning device. And the same contact characteristics can get with the existing wheel on the surface. To secure the orientation stability after overcoming a high obstacle, the reaction force analysis at each caster was performed. Through the analysis results, the orientation stability was secured without the distance compensation at the gantry during or after overcoming obstacles. To verify the obstacle-overcoming ability of the ITW, a 6m - high - test bench and a 0.3m - high - obstacles was manufactured. With a scenario defining an angular position of ITW, the ability of overcoming obstacle was confirmed in the test. In addition, the scenario was supplemented for stable overcoming to avoid a collision against obstacles through additional experiments.

This study aimed to optimize the rope winch of a façade-cleaning robot, a system that travels vertically using the friction between ropes and pulleys. However, position errors can be caused by various factors during locomotion. This adversely affects the robot’s position accuracy. To solve this problem, an experiment was conducted to secure the repeatability of the robot position by optimizing it using the Taguchi method. Subsequently, an error compensation was designed by predicting slip errors of the rope, and accordingly the positional accuracy was determined through feedforward and feedforward + PI control. The experimental optimization confirmed that optimal repeatability can be obtained using a pressure module with the force of 45 N and an axial groove pitch angle of 6° of a pulley. The position accuracy was improved using an error prediction model based on weights, travel distances, and controllers. For a travel distance of 3.0 m, the position error could be reduced to 55%–81% and 72%–89% through feedforward control and feedforward + PI control, respectively, compared with that of the open-loop. The observations of this study could facilitate the control of the position of façade-cleaning robots and aid in the improvement of position accuracy.

As the number of high-rise buildings is increasing, more methods of exterior-wall cleaning are being developed. There are a few models based on artificial intelligence that determine the type and level of contamination primarily by moving the cleaning area. In this study, we propose an system using YOLOv3 algorithm, color-detection, to install on façade cleaning robot and brightness-discrimination. There are three types of contaminant-detection parameters: size, color, and brightness, and these parameters are subjected to a robust optimization process to maintain a constant detection rate under different conditions. The three parameters are determined via Taguchi method with signal to noise ratio and noise factors. An environment for algorithm testing is established, and artificial contamination is implemented on the specimen. A field test with the detection algorithm shall be performed in the near future.

This paper proposes a three-degree-of-freedom manifold composed of three linear actuators. The proposed mechanism consists of a workspace suitable for facade cleaning and can compensate for the horizontal position from disturbances in a gondola-based exterior-wall cleaning. We design a cleaning manipulator that can ensure a constant cleaning area by compensating for the disturbance in each direction. The position, velocity kinematic, and Jacobian-based singularity analysis are presented, and kinematic variables are defined to extend a singularity-free workspace. In addition, optimization is performed based on an index that demonstrates the mechanical properties of the manipulator. The result shows how the manipulator compensates for the disturbances as well as the features of the optimization model. This study can be applied to robot manipulators for facade cleaning in the future.

This paper presents a rope winch with high position repeatability using a differential gear mechanism. This winch is easy to apply to existing buildings using synthetic fiber ropes, which are generally used by building exterior maintenance workers, and can be widely utilized as a winch of a gondola or climbing robot. Multiple pulleys are used to achieve high payloads, and differential gear mechanisms are used to distribute the torque across each pulley evenly. Uniform torque distribution minimizes slipping on each pulley, which reduces the power loss due to friction. This is proven through an analysis using the capstan equation and an experiment on a test bench. In addition, a criterion for the position repeatability of the winch is designed, and its results show that one pressure roller achieves optimal performance when the roller at the free end is pressed to 37 N. Extensive experiments were carried out on the final model of the winch, and position repeatability of under 50 mm deviation per 10 m was achieved through stable torque distribution under various payloads.

Steps are frequently encountered while mobile robots move in indoor environments; thus, the ability to overcome a step is essential to indoor mobile robots. In this study, a new adaptive transformable wheel is conceptually proposed to effectively overcome steps of different sizes. The center trajectory of the proposed wheel is optimally designed to minimize its fluctuations while the robot overcomes a step. For this purpose, a kinematic analysis of the proposed wheel is performed to identify the points that its center must pass while the robot overcomes a step. The center trajectory is optimized with an objective function to evaluate the mobile stability of the proposed wheel under kinematic constraints to avoid undesired interferences between the wheel and the step. Extensive simulations with different steps verify that the optimal trajectory ensures stable and effective overcoming of steps. The experiment using the prototype of mobile robot equipped with the proposed wheel verifies the smoothness of resulting trajectory of wheel center.

In recent years, as number of new building getting larger, there has been an increased interest in the cleaning of exterior walls. Accordingly, there is a growing interest in automatic cleaning robots that move around the outer building façade. These robots are also required to apply different cleaning methods to remove various contaminants on the outer wall of the building. However, current surface contaminant detection systems can either detect only a single type of contaminant, or are not compact enough for installation on mobile platforms that move around the outer façade. As cleaning workers are able to distinguish various contaminants with the naked eye, we aim to solve this problem by developing a machine-vision system using convolutional neural networks (CNNs) and image processing methods. As it is a compact system that uses only a camera to take pictures and a processor to process the images, it is suitable for applications involving mobile platforms. Object-type contaminants such as avian feces are handled by the YOLOv3 module using the object-detection algorithm. Area-type contaminants such as rusty stains are processed using the color-detection module using the HSV color space, median filter, and flood fill algorithm. Particle-type contaminants such as dust are handled by the grayscale module, converting images to grayscale images and then comparing the average brightness with a reference that is provided in advance. This proposed machine vision system will detect objects, areas, and particle-type contaminants with a single image and some reference images provided in advance.

We present a new deep learning framework for removing honeycomb artifacts yielded by optical path blocking of cladding layers in fiber bundle imaging. The proposed framework, HAR-CNN, provides an end-to-end mapping from a raw fiber bundle image to an artifact-free image via a convolution neural network (CNN). The synthesis of honeycomb patterns on ordinary images allows conveniently learning and validating the network without the enormous ground truth collection by extra hardware setups. As a result, HAR-CNN shows significant performance improvement in honeycomb pattern removal and also detailed preservation for the 1961 USAF chart sample, compared with other conventional methods. Finally, HAR-CNN is GPU-accelerated for real-time processing and enhanced image mosaicking performance.

Façade cleaning is very difficult and dangerous work for human workers. The automation of façade cleaning is considered a large market with significant potential, and it is also considered a market that needs to be replaced by a robotic solution. Several researchers have previously attempted to replace the façade cleaning task by a semi-automated device; however, there is no effective solution yet on the market. In this paper, we share our experiences involving the unmanned façade cleaning robot equipped on a gondola. The robot is composed of a two-degree of freedom robotic manipulator and a cleaning device. The cleaning device sprays a cleaning solution, brushes the solution, and retrieves the solution by suction with a squeegee. A robust controller is used to operate the robot manipulator in order to control the force and position of the cleaning device to the wall. The robot is tested on the 63-building, which is the most popular high-rise building in Korea, and the successful results are obtained with respect to the cleaning performance, with some problems requiring further improvements. From the field test, we find the potential to commercialize the robotic platform, as well as some information to improve the robot's performance. We believe that the information on the cleaning experiment may be helpful for field robot researchers.

As the demand and market for building maintenance are increasing, automated building façade cleaning has become essential. Robots are replacing human workers because cleaning work on high-rise buildings using gondolas can be dangerous. Several façade cleaning robots have been developed for climbing, and practical knowledge to clean the façade is being adopted in their cleaning devices. In this study, a passive linkage suspension mechanism and tri-star wheels are applied to solve the problems of unclean zones due to failures during overcoming obstacles and the problems through the use of additional actuators. Various mechanism models have been introduced and their performances have been compared based on dynamic simulation considering obstacle encounters.

Stairs are common obstacles in indoor environments and are difficult to overcome for robots. The speed of robot stair-climbing should be similar to that of humans for commercial products, but their speed remains limited. Additionally, the variety of dimensions of stairs is also a significant problem for robust stair-climbing by robots. In this paper, a curved spoke-based tri-wheel mechanism is proposed for fast and robust stair-climbing. The goal speed of stair-climbing is similar to the human speed for variously sized stairs. The proposed wheel system is composed of a tri-wheel mechanism with a curved spoke, wherein the dimensions of the mechanism are determined based on a kinematic analysis. Between the tri-wheels, a stopper mechanism acts to make the initial condition of the sequential stair-climbing the same as the initial starting condition. Static analysis to analyze the minimum friction coefficient is performed to verify the performance of the robot. Experiments based on the prototype are performed to verify the stair-climbing speed for variously sized stairs; the results indicate that fast and robust stair climbing performance is achieved. These findings can be used to design an indoor service robot for various applications.

This study presents a real-time algorithm for even distributing the torque burden on the parallel manipulator with an autonomous underwater vehicle (AUV) through the cooperation of the AUV and manipulator. For the redundant resolution of the underwater vehicle manipulator system (UVMS), we used the weighting matrix of the weighted pseudo inverse for kinematic and dynamic modeling. We made dynamic and kinematic modeling using the force distribution characteristics of parallel manipulators. Using the parallel manipulator's model, the weighting matrix was changed every second to share the manipulator torque with the AUV. The Taguchi method was used to reduce the calculation time for real-time calculation and to perform valve rotation operations with as little torque as possible even in an underwater environment where it is difficult to determine any cause of errors. To demonstrate the effectiveness of this algorithm, we experimented with valve rotation in water using the UVMS. Analysis of the experimental results revealed that the manipulator torque load was greatly reduced due to the AUV load distribution.

The maintenance of buildings has become an important issue with the construction of many high-rise buildings in recent years. However, the cleaning of the outer walls of buildings is performed in highly hazardous environments over long periods, and many accidents occur each year. Various robots are being studied and developed to reduce these incidents and to relieve workers from hazardous tasks. Herein, we propose a method of spraying high-pressure water using a pump and nozzle, which differs from conventional methods. The cleaning performance parameters, such as water pressure, spray angle, and spray distance, were optimized using the Taguchi method. Cleaning experiments were performed on window specimens that were contaminated artificially. The cleaning performance of the proposed method was evaluated using the image-evaluation method. The optimum condition was determined based on the results of a sensitive analysis performed on the image data. In addition, the reaction force due to high pressure and impact force on the specimens were investigated. These forces were not sufficient to affect the propeller thrust or cause damage to the building's surface. We expect to perform field tests in the near future based on the output of this research.

Lizards run quickly and stably in a bipedal gait, with their bodies exhibiting a lateral S-shaped undulation. We investigate the relationship between a lizard's bipedal running and its body movement with the help of a dynamic simulation. In this study, a dynamic theoretical model of lizard is assumed as a three-link consisting of an anterior and posterior bodies, and a tail, with morphometrics based on Callisaurus draconoides. When a lizard runs straight in a stable bipedal gait, its pelvic rotation is periodically synchronized with its gait. This study shows that the S-shaped body undulation with the yaw motion is generated by minimizing the square of joint torque. Furthermore, we performed the biomechanical simulation to figure out the relationship between the lizard's lateral body undulation and the bipedal running locomotion. In the biomechanical simulation, all joint torques significantly vary by the waist and tail' motions at the same locomotion. Besides, when the waist and tail joint angles increase, the stride length and duration of the model also increase, and the stride frequency decreases at the same running speed. It means that the lizard's undulatory body movements increase its stride and help it run faster. In this study, we found the benefits of the lizard's undulatory body movement and figured out the relationship between the body movement and the locomotion by analyzing the dynamics. In the future works, we will analyze body movements under different environments with various simulators.

Bio-inspiration is a good starting point of designing innovative mechanical systems, including robots [...]

This paper presents a switching PD-based sliding mode control (PD-SMC) method for the 6-degree-of-freedom (DOF) hovering motion of the underwater robot with tilting thrusters. Four thrusters of robot can be tilted simultaneously in the horizontal and vertical directions, and the 6-DOF motion is achieved by switching between two thruster configurations. Therefore, the tilting speed of thruster becomes the most essential parameter to determine the stability of hovering motion. Even though the previous PD control ensures stable hovering motion within a certain ranges of tilting speed, a PD-SMC is suggested in this paper by combining PD control with sliding mode control in order to achieve acceptable hovering performance even at the much lower tilting speeds. Also, the sign function in the sliding mode control is replaced by a sigmoid function to reduce undesired chattering. Simulations show that while PD control is effective only for tilting duration of 600 ms, the PD-based sliding mode control can guarantee the stable hovering motion of underwater robot even for the tilting duration of up to 1500 ms. Extensive experimental results confirm the hovering performance of the proposed PD-SMC method is much superior to that of PD method for much larger tilting durations.