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Abstract Many haptic guidance systems have been studied over the years; however, most of them have been limited to predefined guidance methods. Calculating guidance according to the operator’s motion is important for efficient human motor adaptation and learning. In this study, we developed a system that haptically provides guidance trajectory by sequential weighting between the operator’s trajectory and the ideal trajectory calculated from a predictive-vision system. We investigated whether motion completion with a predictive-vision system affects human motor accuracy and adaptation in time-constrained goal-directed reaching and ball-hitting tasks through subject experiments. The experiment was conducted with 12 healthy participants, and all participants performed ball-hitting tasks. Half of the participants get forceful guidance from the proposed system in the middle of the experiment. We found that the use of the proposed system improved the operator’s motor performance. Furthermore, we observed a trend in which the improvement in motor performance using this system correlated with that after the washout of this system. These results suggest that the predictive-vision system effectively enhances motor accuracy to the target error in dynamic and time-constrained reaching and hitting tasks and may contribute to facilitating motor learning.

Microinjection technology has been widely applied in various fields, including biology, medicine, and intracytoplasmic sperm injection (ICSI). In a typical ICSI environment, all tasks, such as determining the degree of extension, adjusting the depth of focus, finding polar bodies, and manipulating cells, rely only on visual information; therefore, the person performing ICSI should have particular skills. Consequently, ICSI is generally performed by embryologists specialized in embryo handling. However, with the recent growth in global demand for ICSI, there is a shortage of embryologists and lack of experience among embryologists, and a simple injection system that does not rely on skilled embryologists is required. In this study, we propose a micromanipulation interface that provides a surface tactile sensation with a fabric actuator based on the real-time image measurement of the degree of cell deformation to simplify our understanding of the cell state. The effectiveness of the proposed interface is verified through cell-puncture experiments conducted by novices and one expert.

Force-feedback devices enhance task performance in most robot teleoperations. However, their increased size with additional degrees of freedom can limit the robot’s applicability. To address this, an interface that visually presents force feedback is proposed, eliminating the need for bulky physical devices. Our telepresence system renders robotic hands transparent in the camera image while displaying virtual hands. The forces applied to the robot deform these virtual hands. The deformation creates an illusion that the operator’s hands are deforming, thus providing pseudo-haptic feedback. We conducted a weight comparison experiment in a virtual reality environment to evaluate force sensitivity. In addition, we conducted an object touch experiment to assess the speed of contact detection in a robot teleoperation setting. The results demonstrate that our method significantly surpasses conventional pseudo-haptic feedback in conveying force differences. Operators detected object touch 24.7% faster using virtual hand deformation compared to conditions without feedback. This matches the response times of physical force-feedback devices. This interface not only increases the operator’s force sensitivity but also matches the performance of conventional force-feedback devices without physically constraining the operator. Therefore, the interface enhances both task performance and the experience of teleoperation.

Template matching is a common approach in bin-picking tasks. However, it often struggles in complex environments, such as those with different object poses, various background appearances, and varying lighting conditions, due to the limited feature representation of a single template. Additionally, during the bin-picking process, the template needs to be frequently updated to maintain detection performance, and finding an adaptive template from a vast dataset poses another challenge. To address these challenges, we propose a novel template searching method in a latent space trained by a Variational Auto-Encoder (VAE), which generates an adaptive template dynamically based on the current environment. The proposed method was evaluated experimentally under various conditions, and in all scenarios, it successfully completed the tasks, demonstrating its effectiveness and robustness for bin-picking applications. Furthermore, we integrated our proposed method with YOLO, and the experimental results indicate that our method effectively improves YOLO’s detection performance.

Abstract Robotic teleoperation is highly valued for its ability to remotely execute tasks that demand sophisticated human decision-making or that are intended to be carried out by human operators from a distance. However, when using the internet as a communication framework for teleoperation, high latency, and fluctuations make accurate positioning and time-dependent tasks difficult. To mitigate the negative effects of time delay, this paper proposes a teleoperation system that uses cross reality (XR) as a predictive display of the outcome of operators’ intended actions and develops a time-delay aware shared control to fulfill the intention. The system targets a liquid pouring task, wherein a white ring that indicates the intended height of the liquid surface is overlayed onto the beaker in a delayed camera image to close the visual feedback loop on the leader side. Simultaneously, the shared control automatically completes the pouring action to track the intended liquid height. The performance of the proposed system is validated based on liquid pouring experiments performed by human subjects. When compared with direct control, the absolute error rate decreased significantly for a constant round-trip time delay of 0.8 s and 1.2 s, similarly for a time-varying delay of 0.4 s and 0.8 s. Moreover, when the time-varying delay was 0.8 s, operators achieved significantly higher accuracy while maintaining comparable operation time. These results indicate that our proposed system improves operability even in the presence of time-varying delays in communication networks.

In recent years, there has been extensive utilization of actuators driven by artificial muscles in wearable devices. However, the muscle distribution configurations of most wearable devices have been specifically designed and are difficult to generalize. Consequently, wearable devices that allow direct installation of actuators onto existing clothing are better suited for a wider range of application scenarios. This letter presents the development and evaluation of Funabot-Suit, a human muscle configuration inspired wearable assist device that employs McKibben artificial muscles to induce natural kinesthetic perception in the wearer’s torso. By integrating thin McKibben muscles into an existing motion capture suit, the Funabot-Suit is capable of generating four fundamental motions: forward and backward bending, and left and right twisting. The suit’s performance was assessed through experiments involving three subjects who wore the suit while standing and seated, with the subjects reporting the direction of their kinesthetic perception. The subjects also rated the perceived ease of kinesthetic perception direction on a five-point scale. Our results demonstrate that the Funabot-Suit successfully induces kinesthetic perceptions for the wearer, with a one hundred percent detection ratio for accurate responses in the command direction across all subjects and positions. We observed variations in the sensitivity of left–right and up-down sensations, which can be attributed to the positioning of artificial muscles and individual differences.

Remote teleoperation has shown significant advancements since the first teleoperation system was proposed by Goertz in the 1940s. In recent years, the research on shared control methodologies in which the robot assists the operators in accomplishing the desired tasks has gained extensive attention. One such important task in teleoperation is object grasping. In this paper, we propose a shared control framework to enhance the teleoperated grasping performance. The proposed framework is built upon a virtual reality device-based direct teleoperation system. In this framework, a template matching-based object point cloud compensation is introduced for multi-angle grasping pose generation. Then, the feasible grasping candidates are selected considering joint constraints-aware manipulability. Finally, the grasping assistance is achieved by trajectory blending with dynamic authority adjustment. To validate the performance of the proposed framework, we carried out experimental evaluations. The output results indicate improved grasping performance in terms of reduced task completion time, linear trajectory, and workload.

Current remote-control interfaces are difficult to operate intuitively while viewing the entire remote display and require familiarity with the operation. The space within an individual’s reach, called the peri-personal space (PPS), assists them in planning their physical movements. Hence, manipulating objects outside one’s PPS is more difficult than doing so inside it. Therefore, this study aimed to develop an interface that creates the illusion of an operator’s finger being transferred to a remote display and transfers the PPS to the virtual finger in the display. To transfer the PPS to a manipulated object, it is necessary to enhance the user’s sense of agency and ownership toward the manipulated target by ensuring it is similar in shape and motion to the user’s body. Long-term input testing confirmed that by transferring the PPS to a virtual finger, there is no significant difference, as suggested by a t-test between the coefficients of the learning curves outside and inside the PPS. Furthermore, when users learned to manipulate the virtual finger outside the PPS under conditions that impaired their sense of agency, even after two weeks of learning, the PPS was not continuously transferred to the virtual finger for more than seven minutes from the start of the virtual finger operation. The experimental results demonstrated that the interface enabled the display located outside the PPS to be operated with the same degree of operability as inside the PPS from the start of the operation, even with a short learning period.

Microinjection technology is widely used in biotechnological processes such as gene manipulation and microinsemination. Generally, microinjection is performed under an optical microscope while viewing the video of the targets in real-time. In the microinjection process, multiple oocytes must be placed in the same droplet, for which the injection must be performed multiple times. Furthermore, the target must be observed at different magnifications during injection and the oocyte transfer operation. Hence, the operators are required to change the magnification and light intensity repeatedly. These tasks are complicated and are a burden for the operators. Thus, the accuracy, reproducibility, and productivity of microinjection depend on the operator’s skill level. In this study, to reduce the burden on the operator and simplify the operation of microinjection, we propose a micromanipulation system that enables both wide-range and high-resolution video presentation with free viewpoint selection. The proposed micromanipulation system is based on a view-expansion microscope system with simultaneous multi-view imaging using a galvanometer mirror and a high-speed vision system. We verify the effectiveness of the proposed system by evaluating the resolution of images presented to the operator and through the experiments involving moving microbeads performed by inexperienced subjects. The experimental results indicate that our micromanipulation system streamlines the task of micromanipulation by eliminating the need to change the objective lens.

Robot-assisted minimally invasive surgery (RMIS) has been shown to be effective in improving surgeon capabilities, providing magnified 3D vision, highly dexterous surgical tools, and intuitive human-robot interfaces for high-precision tool motion control. Robotic surgical tools (RST) are a critical component that defines the performance of an RMIS system. Current RSTs still represent a high cost, with few commercially available options, which limits general access and research on RMIS. We aim to take advantage of recent progress in biocompatible 3D printing and contribute to the development of RMIS technologies, presenting an open platform for low-cost, biocompatible, and customizable RSTs. The proposed design concept consists of a 3-DOF end-effector with a decoupled wrist mechanism, a tool interface module, and a tool drive unit. We validated our end-effector design using Finite Element Analysis (FEA) to confirm that stress generated by high grip forces is maintained below the material yield stress. Validation experiments showed that the proposed RST could provide up to 10N grip forces and up to 3N pulling forces. The proposed control framework exhibited a mean absolute positioning tracking error of approximately 0.1 rad. Finally, we also demonstrated the use of the proposed RST in two surgical training tasks: pick-and-place and stitching. The designs and software control framework are open-access and freely available for customization and fast development at https://github.com/jcolan/OpenRST.

In recent years, the demand for effective intracytoplasmic sperm injection (ICSI) for the treatment of male infertility has increased. The ICSI operation is complicated as it involves delicate organs and requires a high level of skill. Several cell manipulation systems that do not require such skills have been proposed; notably, several automated methods are available for cell rotation. However, these methods are unfeasible for the delicate ICSI medical procedure because of safety issues. Thus, this study proposes a microscopic system that enables intuitive micropipette manipulation using a haptic device that safely and efficiently performs the entire ICSI procedure. The proposed system switches between field-of-view expansion and three-dimensional image presentation to present images according to the operational stage. In addition, the system enables intuitive pipette manipulation using a haptic device. Experiments were conducted on microbeads instead of oocytes. The results confirmed that the time required for the experimental task was improved by 52.6%, and the injection error was improved by 75.3% compared to those observed in the conventional system.

Abstract The use of intracytoplasmic sperm injection (ICSI), an assisted reproductive technique (ART), is increasing widely. ICSI is currently performed by specially skilled embryologists. However, with the increasing demand for ART, the shortage of skilled embryologists has become a problem. Therefore, we propose an immersive micromanipulation system that requires no special skills for efficient and accurate micromanipulation. Our proposed system is composed of a real-time three-dimensional (3D) imaging microscope and 3D operation interfaces. The 3D operation interfaces are stationary pen-type or wearable glove-type interfaces. In this system, an operator wearing a head-mounted display (HMD) and using 3D operation interfaces is immersed in a virtual micromanipulation space. The operator can move the pipettes by 3D operation interface and freely change the viewpoint. We verified that the proposed system improves the speed and accuracy of operating a pipette through two types of experiments with subjects.

Abstract The currently available exoskeleton for assisting the paraplegic patient in walking usually adapts a pre-programmed gait that involves the patient following an exoskeleton lead. The system allows the patient to hold a pair of canes in order to keep balance, and does not contribute to keeping balance without the patient’s action. This paper proposes an algorithm based on the zero moment point (ZMP) to modify the gait generated through human walking synergy for paraplegic patients who make use of the exoskeleton system and hold their canes. The proposed ZMP will enable the paraplegic patient to keep balance during walking and also reduce the burden in maintaining balance. First, a pair of cane is used as an interface to control the user’s walking and then, the synergy between legs and canes is used to synchronize the user’s walking intention during the exoskeleton movement. The walking synergy is extracted from the able-bodied subject walking with a pair of canes and analyzed using principal component analysis (PCA). In order to improve the walking stability, the hip joint angle on stance leg during walking was modified based on ZMP. Furthermore, a nonlinear inverted pendulum (NIP) model was utilized in order to generate a gait with a fully stretched knee joint angle that is similar to human gait. The proposed method was verified via the Gazebo simulation using a walking robot to simulate a patient wearing an exoskeleton. The experiment results show that the walking stability was highly improved after gait modification.

There is a growing need for robots that can be remotely controlled to perform tasks of one’s own choice. However, the SoA (Sense of Agency: the sense of recognizing that the motion of an observed object is caused by oneself) is reduced because the subject of the robot motion is identified as external due to shared control. To address this issue, we aimed to suppress the decline in SoA by presenting auditory feedback that aims to blur the distinction between self and others. We performed the tracking task in a virtual environment under four different auditory feedback conditions, with varying levels of automation to manipulate the virtual robot gripper. Experimental results showed that the proposed auditory feedback suppressed the decrease in the SoA at a medium level of automation. It is suggested that our proposed auditory feedback could blur the distinction between self and others, and that the operator attributes the subject of the motion of the manipulated object to himself.

Abstract In this paper, toward robotic gait assistance, we investigate the feasibility of a cane-type assistive mobile robot accompanying the user autonomously through a clinical pilot experiment. As widely known, gait ability is important for all people to keep their quality of life. However, for people having weakened lower limbs such as elderly people, their postural sway during walking could be insuppressible and cause falling. To support the gait motion of elderly people, our group has been developing a series of hand-holding cane robots named Intelligent Cane. Such assistive robots are expected to remove barriers to the independent lives of elderly people. Recently, we have focused on the potential of a companion robot that follows the user ahead and can be touched or grasped for bracing whenever the user needs it. In order to demonstrate proof of our concept through an experiment with a motion capture system, we propose a user companion strategy that enables our cane robot to keep a constant relative distance between the robot and the user walking on a treadmill. We evaluate the accuracy of the user companion in an experiment where a user walks on a treadmill. Then, we conduct a clinical experiment with three healthy subjects walking on with the treadmill with our cane robot as a pilot study. Through the clinical experiment, we evaluate a postural stabilization effect of physical interaction with the robot and discuss the feasibility of our robotic gait assistance methodology.

Abstract Recently, wearable extra robotic limbs that aim to enhance the functionality and capability of human operators as extra arms or fingers have become an active research subject among robotics researchers. Improving the operability of the extra robotic limbs is required for the human operators, an approach for which is to induce robotic embodiment. In this paper, we focus on the update of sense of self-location which is the key aspect of embodiment and contributes to the body representation update, and we elucidate dominant factors which induce the embodiment of an extra robotic thumb (ERT). The experiments are conducted to compare the performance of the reaching task of the ERT under three separately given conditions, of which two are somatosensory feedbacks: (1) tactile and position feedback from the fingertips and (2) tactile and position feedback from the human face, and one is a non-somatosensory feedback: (3) auditory feedback. As a result, we confirmed that the somatosensory feedback from finger tips has a large contribution for the update of sense of self-location.

A wirelessly powered four-channel neurostimulator was developed for applying selective Functional Electrical Stimulation (FES) to four peripheral nerves to control the ankle and knee joints of a rat. The power of the neurostimulator was wirelessly supplied from a transmitter device, and the four nerves were connected to the receiver device, which controlled the ankle and knee joints in the rat. The receiver device had functions to detect the frequency of the transmitter signal from the transmitter coil. The stimulation site of the nerves was selected according to the frequency of the transmitter signal. The rat toe position was controlled by changing the angles of the ankle and knee joints. The joint angles were controlled by the stimulation current applied to each nerve independently. The stimulation currents were adjusted by the Proportional Integral Differential (PID) and feed-forward control method through a visual feedback control system, and the walking trajectory of a rat’s hind leg was reconstructed. This study contributes to controlling the multiple joints of a leg and reconstructing functional motions such as walking using the robotic control technology.

This study proposes a visual sensing system to investigate the self-propelled motions of droplets. In the visual sensing of self-propelled droplets, large field-of-view and high-resolution images are both required to investigate the behaviors of multiple droplets as well as chemical reactions in the droplets. Therefore, we developed a view-expansive microscope system using a color camera head to investigate these chemical reactions; in the system, we implemented an image processing algorithm to detect the behaviors of droplets over a large field of view. We conducted motion tracking and color identification experiments on the self-propelled droplets to verify the effectiveness of the proposed system. The experimental results demonstrate that the proposed system is able to detect the location and color of each self-propelled droplet in a large-area image.

Abstract This paper addresses a reference gait speed generator for limit-cycle-based bipedal gait of humanoid robots in order to achieve secure and efficient acceleration and deceleration without falling down at respective gait speeds. The reference gait speed generator is hard to be developed by analytical approaches due to the necessity of barren work for identifying the respective basins of attraction. We challenge this issue by designing virtual dynamics among a robot, a virtual leader point, and a goal, and adapting it according to a falling risk of the robot. The virtual dynamics, which has settling and acceleration times as design parameters, gives the reference speeds derived from states of the robot and the leader point to a gait speeds controller. In the dynamics, the robot’s mass is optimized virtually to maximize efficiency while ensuring stability stochastically by using a selection algorithm for locomotion. Even when there were obstacles or an up slope in traveling courses of simulations, the robot achieved the autonomous traveling from the start to the goal securely. Specific resistance was also kept small in comparison with local-stability-based walking. The proposed method makes the limit-cycle-based bipedal gait more practical and contributes toward replacing the major method that ensures stability of every step.

Abstract In recent years, there has been great interest in the possibility of using artificial limbs as an extension of the human body as well as replacement of lost limbs. In this paper, we develop a sixth finger system as an extension of the human body. We then investigate how an extra robotic thumb, that works as a sixth finger and gives somatosensory feedback to the user, modifies the body schema, and also affecting the self-perception of existing limbs. The sixth robotic finger is controlled with the thumb of the opposite hand, and contact information is conveyed via electrostimulation to the tip of the thumb controlling the movement. We conducted reaching task experiments with and without visual information to evaluate the level of embodiment of the sixth robotic finger and the modification of the self-perception of the finger controlling the system. The experimental results indicate that not only the sixth finger is incorporated into the body schema of the user, but also the body schema of the controlling finger is modified; ability of the brain to adapt to different scenarios and geometries of the body is also implied.

The reduced workspace in endonasal endoscopic surgery (EES) hinders the execution of complex surgical tasks such as suturing. Typically, surgeons need to manipulate non-dexterous long surgical instruments with an endoscopic view that makes it difficult to estimate the distances and angles required for precise suturing motion. Recently, robot-assisted surgical systems have been used in laparoscopic surgery with promising results. Although robotic systems can provide enhanced dexterity, robot-assisted suturing is still highly challenging. In this paper, we propose a robot-assisted stitching method based on an online optimization-based trajectory generation for curved needle stitching and a constrained motion planning framework to ensure safe surgical instrument motion. The needle trajectory is generated online by using a sequential convex optimization algorithm subject to stitching kinematic constraints. The constrained motion planner is designed to reduce surrounding damages to the nasal cavity by setting a remote center of motion over the nostril. A dual concurrent inverse kinematics (IK) solver is proposed to achieve convergence of the solution and optimal time execution, in which two constrained IK methods are performed simultaneously; a task-priority based IK and a nonlinear optimization-based IK. We evaluate the performance of the proposed method in a stitching experiment with our surgical robotic system in a robot-assisted mode and an autonomous mode in comparison to the use of a conventional surgical tool. Our results demonstrate a noticeable improvement in the stitching success ratio in the robot-assisted mode and the shortest completion time for the autonomous mode. In addition, the force interaction with the tissue was highly reduced when using the robotic system.

Endoscopic endonasal surgery (EES) is a minimally invasive technique for removal of pituitary adenomas or cysts at the skull base. This approach can reduce the invasiveness and recovery time compared to traditional open surgery techniques. However, it represents challenges to surgeons because of the constrained workspace imposed by the nasal cavity and the lack of dexterity with conventional surgical instruments. While robotic surgical systems have been previously proposed for EES, issues concerned with proper interface design still remain. In this paper, we present a cooperative, compact, and versatile bimanual human-robot interface aimed to provide intuitive and safe operation in robot-assisted EES. The proposed interface is attached to a robot arm and holds a multi-degree-of-freedom (DOF) articulated forceps. In order to design the required functionalities in EES, we consider a simplified surgical task scenario, with four basic instrument operations such as positioning, insertion, manipulation, and extraction. The proposed cooperative strategy is based on the combination of force based robot control for tool positioning, a virtual remote-center-of-motion (VRCM) during insertion/extraction tasks, and the use of a serial-link interface for precise and simultaneous control of the position and the orientation of the forceps tip. Virtual workspace constraints and motion scaling are added to provide safe and smooth control of our robotic surgical system. We evaluate the performance and usability of our system considering reachability, object manipulability, and surgical dexterity in an anatomically realistic human head phantom compared to the use of conventional surgical instruments. The results demonstrate that the proposed system can improve the precision, smoothness and safety of the forceps operation during an EES.

Peripheral nerve disconnections cause severe muscle atrophy and consequently, paralysis of limbs. Reinnervation of denervated muscle by transplanting motor neurons and applying Functional Electrical Stimulation (FES) onto peripheral nerves is an important procedure for preventing irreversible degeneration of muscle tissues. After the reinnervation of denervated muscles, multiple peripheral nerves should be stimulated independently to control joint motion and reconstruct functional movements of limbs by the FES. In this study, a wirelessly powered two-channel neurostimulator was developed with the purpose of applying selective FES to two peripheral nerves—the peroneal nerve and the tibial nerve in a rat. The neurostimulator was designed in such a way that power could be supplied wirelessly, from a transmitter coil to a receiver coil. The receiver coil was connected, in turn, to the peroneal and tibial nerves in the rat. The receiver circuit had a low pass filter to allow detection of the frequency of the transmitter signal. The stimulation of the nerves was switched according to the frequency of the transmitter signal. Dorsal/plantar flexion of the rat ankle joint was selectively induced by the developed neurostimulator. The rat ankle joint angle was controlled by changing the stimulation electrode and the stimulation current, based on the Proportional Integral (PI) control method using a visual feedback control system. This study was aimed at controlling the leg motion by stimulating the peripheral nerves using the neurostimulator.

In recent years, the use of microinjections has increased in life science and biotechnology fields; specific examples include artificial insemination and gene manipulation. Microinjections are mainly performed based on visual information; thus, the operator needs high-level skill because of the narrowness of the visual field. Additionally, microinjections are performed as the operator views a microscopic image on a display; the position of the display requires the operator to maintain an awkward posture throughout the procedure. In this study, we developed a microscopic image display apparatus for microinjections based on a view-expansive microscope. The prototype of the view-expansive microscope has problems related to the variations in brightness and focal blur that accompany changes in the optical path length and amount of reflected light. Therefore, we propose the use of a variable-focus device to expand the visual field and thus circumvent the above-mentioned problems. We evaluated the observable area of the system using this variable-focus device. We confirmed that the observable area is 261.4 and 13.9 times larger than that of a normal microscope and conventional view-expansive microscopic system, respectively. Finally, observations of mouse embryos were carried out by using the developed system. We confirmed that the microscopic images can be displayed on a head-mounted display in real time with the desired point and field sizes.

This paper aims to determine an optimal structure for a quadruped robot, which will allow the robot’s joint torque sum to be minimised. An animal’s characteristic limb length ratio is a vital part of its overall morphology and the one that enables it to travel easily through its environment. For the same reason, a robot’s structure needs to be suitably designed for locomotion in its working environment. Joint torques are necessary to maintain the posture of the robot and to accelerate joint angles during walking motion, hence, minimisation of joint torques reduces energy consumption. We performed a numerical simulation in which we analysed the joint torques for various limb lengths and slope angles in order to determine the optimal structure of a robot walking on a slope. Our investigation determines that the optimal Ratio of Rear Leg Length (RRL) can be derived by the use of a simulation designed to determine the physical structure of quadruped robot. Our analysis suggests that joint torque will increase as the slope angle becomes steeper if the rear legs of the robot are shorter than its forelegs, and that joint torque will decrease as the slope angle declines if the robot’s forelegs are shorter than its rear legs. Finally, experimental results validated our simulation analysis.

Bipedal walking ability, which is mainly composed of mechanical stability and moving efficiency, is one of the most important issues in the field of humanoid robots. An effective use of the arms is expected to improve the walking ability under the constraints from limited body. Multiple usages of the arms are required to adapt the robot to various walking conditions because each usage possesses different utility, respectively. We propose two strategies for arm-swing to enhance stability and efficiency. Both the strategies use the selection algorithm for locomotion (SAL) that determines the optimal locomotion for the various walking conditions. One strategy is a use/compensation of moment of swing-leg by hip-rotation/arm-swing. This strategy, called Ro-SAL, selects a rotation rate of hip depending upon a falling risk. Another strategy is a support of the center of gravity (COG) tracking. This strategy, called Su-SAL, employs a predictive control, and a support weight that determines weights of input and output in the predictive control is also selected depending upon the falling risk. From simulation results, we validate that Ro-SAL is effective in a stable state and a state with internal model error, while Su-SAL is effective in states with external force and environmental complexity.

We investigate the effect of appearance variations on the detectability of vibration feature extraction with pixel-level digital filters for high-frame-rate videos. In particular, we consider robust vibrating object tracking, which is clearly different from conventional appearance-based object tracking with spatial pattern recognition in a high-quality image region of a certain size. For 512 × 512 videos of a rotating fan located at different positions and orientations and captured at 2000 frames per second with different lens settings, we verify how many pixels are extracted as vibrating regions with pixel-level digital filters. The effectiveness of dynamics-based vibration features is demonstrated by examining the robustness against changes in aperture size and the focal condition of the camera lens, the apparent size and orientation of the object being tracked, and its rotational frequency, as well as complexities and movements of background scenes. Tracking experiments for a flying multicopter with rotating propellers are also described to verify the robustness of localization under complex imaging conditions in outside scenarios.