In this study, a self-standing takeoff method was developed for a servo-driven flapping robot. This method does not use any additional mechanisms or external platforms to maintain the robot’s position before takeoff. In addition to its efficiency in terms of weight, this method is also relatively easy to implement. This takeoff method extends the function of the tail not only for longitudinal direction control during flight, but also as a base to support the standing posture of the flapping robot. The objective of this investigation was to determine the optimal parameters to be implemented in the self-standing takeoff algorithm. To enhance the probability of successful takeoff, an investigation was conducted into the various parameters that influence the self-takeoff process. The investigative process was initiated with a static experiment to determine the thrust generated by the flapping robot. Subsequently, the variables of the center flapping angle, timing adjustment, and initial flapping direction were examined. A series of indoor flight experiments were conducted to evaluate the self-standing takeoff performance of the flapping robot. The experiment tested two weighted robots, the first 43 g and the second 45 g (thrust/weight (T/W) ratios of 1.02 and 0.97, respectively). The results showed that the proposed takeoff method requires only a T/W ratio of 1.02 for takeoff, less than the 1.2 previously required.

Extended Reality, artificial intelligence, and big data technologies offer new opportunities for advancing rehabilitation diagnosis and training. This study presents a method for extracting behavioral features from a visual search task conducted in an immersive virtual reality environment. To identify motion patterns specific to individual patients, we employ a topological mapping approach based on Growing Neural Gas (GNG), which adapts its structure dynamically using node activation and error-based edge management. While GNG effectively captures spatial characteristics, it lacks the ability to model temporal relationships and is sensitive to hyperparameter settings. To address these limitations, we introduce a spatiotemporal topological clustering method, along with a hierarchical framework that enables segmentation at multiple levels of granularity. Furthermore, to evaluate feasibility, we conducted a visual search task with three patients, including one with USN, and performed a comparative analysis of their extracted motion features.

Birds are agile in locomotion and able to move quickly and easily from one place to another. When a bird is on the ground, and a threat approaches, the bird will fly away and escape. An ornithopter robot provides advantages in energy saving, maneuverability, and crash safety. Most flapping robots require an operator or assistance to take off. The goal of this study is to enable self-takeoff from the ground. The developed robot can generate thrust to its body by exceeding its own weight using a simple flapping mechanism and lightweight design. The result of the takeoff experiment showed that the ornithopter robot was able to self-takeoff from the ground without assistance.

This paper presents a method with dynamic density topological structure generation for low-cost real-time vertical ladder detection from 3D point cloud data. Dynamic Density Growing Neural Gas (DD-GNG) is proposed to generate a dynamic density of the topological structure. The density of the structure and the number of nodes will be increased in the targeted object area. Feature extraction model is required to classify suspected objects for being processed in the next time process. After that, rungs of the vertical ladder is processed using an inlier-outlier method. Thus, the ladder detection model represents the ladder with a set of nodes and edges. Next, affordance detection is processed for detecting the feasible grasped location. To validate the effectiveness of the proposed method, a series of experiments are conducted on a 4-legged robot with a non-GPU board for real-time vertical ladder detection and climbing to validate the effectiveness of the proposed method. Results show that our proposed method able to detect and track the ladder structure in real-time with a much lower computational cost. The affordance of the ladder provides safety information for robot grasping.

This paper presents the novel capabilities of a quadruped robot by performing horizontal-vertical-horizontal movement transition through vertical ladder without handrailing supporter. To overcome the proposed problem, we propose a multi-behavior generation model using independent stepping and pose control in the quadruped robot. The model is able to generate appropriate behavior depending on external (3D point clouds) and internal sensors (ground touch sensor, and Inertial Measurement Unit). Posture condition, safe movement area, possible touchpoint, grasping possibility, and target movement are the information that is analyzed from the sensors. There are four options developed in behavior generation, which are, Approaching, Body Placing, Stepping, and Grasping behavior. In order to prove the effectiveness of the proposed algorithm, the model was implemented on the computer simulation and the real application. Before being applied in the real robot, the proposed model is optimized in the computer simulation. Then, the optimized parameter is used for applying in the real robot. As a result, the robot succeeded to move through the ladder without handrail from lower stair to upper stair. From the analysis, the body placing behavior is the most important strategy in the proposed case.

In this paper, we propose a real-time spatial shape estimation method for an elastic rod. Our proposed method does not use any image sensor nor shape sensor, but does use a six-axis force/torque sensor placed near one end of the elastic rod. In the proposed shape estimation method, the occlusion problem never occurs principally because the shape of a flexible object will be estimated based on an elastic rod model. We utilize the discretized Kirchhoff elastic rod for shape estimation, which can be viewed as a serial chain of rigid bodies connected with three-degree-of-freedom rotational spring joints. We show that real-time spatial shape estimation is possible based on real-time sensing of force/torque information. The computational time of the proposed shape estimation algorithm is linear in the number of rigid-body partition. Moreover, the required calculations are very simple owing to deep understanding of robot manipulator kinematics. Thus we can compute the spatial rod shape in realtime. We show experimental results in order to validate our proposed method.

This paper proposes a real-time feature extraction and segmentation method for a 3D point cloud. First of all, we apply Growing Neural Gas with Utility (GNG-U) to the point cloud for learning a topological structure. However, the standard GNG-U cannot learn the topological structure of 3D space environment and color information simultaneously. To this end, we then modify the GNG-U algorithm by using a weight vector. we propose a surface feature extraction and segmentation method by efficiently utilizing the topological structure. Our segmentation method is based on a region growing method whose similarity value uses the inner value of two normal vectors connected by the topological structure. We show experimental results of the proposed method and discuss the effectiveness of the proposed method.

This paper describes an air-coupled ultrasound system by using DIO-2000. The system is aimed to use for inner muscle evaluation in rehabilitation process. The system evaluates inner muscle with low constrain than conventional method which measured by using MR image, X-ray CT and contacted ultrasound system. Our air-coupled ultrasound system measures transmitted ultrasound wave with very low power through human abdominal region by employing a pulsar-receiver with high sensitive preamplifier, and wave detection method based on fuzzy inference finds transmitted wave from noisy wave. The fuzzy inference is derived from characteristics of transmitted wave. In the experiment, we evaluate the accuracies of wave detection method for human body.

In this paper, we investigate the position control of spherical ultrasonic motor (SUSM). The generated torque of SUSM is influenced by the phase difference and the driving frequency of applied AC voltages. Therefore, the control strategy is classified into three types: (a) variable phase and fixed frequency, (b) fixed phase and variable frequency, and (c) variable phase and frequency. We formulate the position control rules for SUSM based on the above three types of control variables, and investigate the performances experimentally.

Some recent studies have addressed a class of human-machine coordination employing ldquovirtual fixtures,rdquo which are computer-generated walls or guides presented through haptic devices for assisting precise path tracing and for preventing the entry to specified regions. This paper presents the concept and control algorithms of a new class of virtual fixtures that is based on simulated plasticity. The plasticity-based virtual fixtures act as hard walls as long as the user's force is smaller than a predetermined yield force, but the user can deviate from the fixtures by intentionally producing a force larger than the yield force. As a characteristic of plasticity, the proposed virtual fixtures do not store elastic energy; the reaction force from the fixture almost always opposes the user's motion to decelerate the motion. Thus, the plasticity-based virtual fixtures are expected to be useful in some applications where safety is an utmost priority. This paper presents control algorithms for realizing the concept of plasticity-based virtual fixtures, addressing technical challenges in treating discontinuous nature of plasticity in discrete-time systems. The algorithms were demonstrated through experiments using impedance-type and admittance-type haptic devices.

This paper presents an approach for producing virtual fixture based on simulated plasticity, which can be used for assisting precise manual manipulations performed by human users through haptic interfaces. The fixture acts as a guide to help path-tracing tasks and as a wall for preventing a tool from entering a specified region, but the user can move against the fixture by intentionally producing a force larger than a predetermined yield force. The advantage of the proposed virtual fixture is that it is always passive and it acts as a hard fixture when the user's force is smaller than the yield force. The algorithm was demonstrated through experiments using an impedance-type haptic interface.

Modeling of friction force is cumbersome because of its discontinuity at zero velocity. This paper presents a set of discrete-time friction models for the purpose of haptic rendering and virtual environment construction. These models allow friction to be treated as an admittance-type or impedance-type element of a virtual environment. They are derived from implicit Euler integration of Coulomb-like discontinuous friction and linear mass-spring-damper dynamics, and have closed-form expressions. They include rate-dependent friction laws, and their extension to multidimensional cases is easy in most practical cases. The validity of the models is demonstrated through numerical examples and implementation experiments

Friction force is cumbersome in numerical simulations due to its discontinuity at zero velocity. Fixed-step simulation techniques are especially desirable for control purposes, such as haptic friction rendering and friction compensation. Previous techniques have difficulties especially in numerical robustness and extensibility to multidimensional cases. This paper proposes two discrete-time friction models that can be used in fixed-step simulations. They can be used in multidimensional space, and can capture arbitrary velocity-dependent friction phenomena. The first one is a discrete-time discontinuous model. This model determines the friction force so that the velocity reaches zero in finite time by using the values of the mass and the timestep size. The second one is a discrete-time continuous model, which is a serial coupling of the discontinuous model and a linear viscoelastic element. This model is useful for haptic rendering because it is formulated as a velocity-input, force-output system. The second model can be extended into a more sophisticated friction model, which exhibits a hysteresis behavior in the presliding regime. Results of numerical simulations and an experiment are presented.

Human-machine cooperative systems have been proposed. Most of them consider carrying, positioning and assembling tasks. Precise tracking tasks are also required in factories. However, an assist system for tracking task has not been studied well. In this paper, we aim to realize the human-machine system that assists a tracking task. In order to achieve the goal, the virtual friction field is proposed. Isotropic and anisotropic friction fields are presented and they are applied to the rotating object which should be tracked. The tracking task experiments are carried out and it is shown that the virtual guide of the friction improves the tracking performance effectively.

This paper introduces a device for enhancing detection of surface undulation through active touch. This device, which we call a “tactile contact lens,” is composed of a sheet and numerous pins arranged on one side of the sheet. Experimental results show that a small bump on a surface can be detected more accurately through this device than by bare finger and than through a flat sheet. A mathematical analysis of this phenomenon suggests two possible explanations for this phenomenon. One lies in the lever-like behavior of the pins. The pins convert the local inclination of the object surface into the tangential displacement of the skin surface. The second is the spatial aliasing effect resulting from the discrete contact. Due to this effect, the temporal change in the skin surface displacement is efficiently transduced into the temporal change in the skin tissue strain. The results of this analysis are then discussed in relation to other sensitivity-enhancing materials, tactile sensing mechanisms, and tactile/haptic display devices.

Magnetorheological (MR) fluids are materials that change their rheological behavior in the presence of an applied magnetic field. Devices using MR fluids have an ability to provide high torque, low inertia, be a safe device and have a simple interface. We have developed an MR-fluid actuator, which consists of an input component, an output component and an MR-fluid clutch between the two. In this paper, we investigate the dynamic characteristics of an MR-fluid actuator and aim to improve its response. Transient magnetic analyses are examined and experimental results are shown in the case of the proposed approaches. Finally, we realize a much faster MR-fluid actuator.

Homogeneous electrorheological (ER) fluid damper reduce the vibration in robot joints due to the elasticity of the drive system. Also, it enlarges servo stiffness in direct-drive motor system. However, conventional research into ER fluids is based on parallel electrodes with ER fluids between them while ER fluids are used in a shear mode. Since a high voltage is required for use of ER fluids with parallel electrodes, problems of cost, safety and wiring to moving part for practical applications are of concern. In order to solve some of the above problems, we have proposed a one-sided pattern electrode, which is an electrode in a pattern arranged on only one of the two surfaces of a pair of electrodes, with an insulator arranged on the other surface. We experimentally verify the manifestation of ER effects in a homogeneous ER fluid. Moreover, the effect of disk gap upon viscosity change was investigated. The proposed configuration leads to new damping devices for robots and mechatronics systems.

Magnetorheological (MR) fluids are substances that respond to an applied magnetic field with a change in their theological behavior. Though they are functionally similar to electrorheological (ER) fluids, MR fluids exhibit much higher yield strengths for the applied magnetic fields than ER fluids for the applied electric fields. The devices using MR fluids have an ability to provide high-torque, low-inertia, a safe device and simple interface. In this study, we report on an actuator developed using the MR fluid, which consists of an input part, an output part and an MR fluid clutch between them. First, the basic experiments are examined to investigate the characteristics of the actuator. Next, the torque control system of the MR-fluid actuator is proposed. Finally, the closed-loop control experiments were carried out and it is confirmed that the torque-feedback control is effective for improving the response properties of MR actuators.

Force information is often required for tele-operation systems and virtual reality. Conventional force displays are active systems with actuators. This, however, is inherently active, so that it may become a danger. Consequently, passive force display is an effective method for assuring safety. The authors developed a brake using ER (electrorheological) fluid and passive force display using ER brakes. They discuss two degree of freedom passive force display and basic control experiments.

In industrial robots, each joint is driven through a reduction gear unit such as a harmonic drive gear. The elasticity of the drive systems cannot be ignored when the high-speed and precise motion control is required for robots. Due to the elasticity of the drive systems, vibratory behaviors are caused, and the control performances of robot systems deteriorate. In this study, we develop a new actuator that consists of an AC servomotor, a harmonic drive gear and an electrorheological (ER) damper. The ER damper can change the damping coefficient by applying an electric field. Since the gap between electrodes of the ER damper is 80 /spl mu/m only the voltage of 160 V is needed for the electric field of 2 kV/mm. The ER damper consumes little electric power. The actuator is installed on a one-link robot arm. The mathematical model of the robot arm is derived, and the eigenvalues of the robot system are analyzed. Experiments were carried out, and the effectiveness of the actuator is confirmed.

Since a direct-drive (DD) motor system does not have the reduction gear, its structure is simple and has stiffness. In the DD motor system, the disturbance torque directly influences the control accuracy. The high servo stiffness is effective and important for reducing the influence of the disturbance torque. However, the high servo control often makes the system vibratory or unstable. Therefore, the servo gain must be lowered for assuring stability, and the influence of the disturbance becomes serious. In this study, the DD motor system using an electro-rheological (ER) fluid damper is developed. By applying the ER damper to the DD motor system, the gain margin of the control system is improved, so it is possible to realize the high servo control. Finally, it is experimentally shown that the proposed system is effective for high-speed and high-precision control.

A semiclosed-loop control which utilizes the signal of an encoder mounted on a servomotor is adopted in the control of industrial robots. In this method, the position of the end-effector is not controlled very accurately. Therefore, we aim to apply a closed-loop control which uses the positional signal measured directly at the end-effector. Because of the flexibility of the driving system, however, it is very difficult to control the arm based on this method. In this study, a robot arm is developed which has a variable damper using an electrorheological fluid (ER fluid). It is shown that the ER damper is very effective for precise position control based on a closed-loop control method.