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The learning and inference efficiencies of an artificial neural network represented by a cross-point synaptic memristor array can be achieved using a selector, with high selectivity (I

This article proposes a compact ankle exoskeleton with a multiaxis parallel linkage mechanism. By applying torques to the ankle joint, it can generate dorsi- and plantar-flexion motions. The design variables of the mechanism were analyzed and optimized to accommodate up to 12 N·m of torque within a thickness constraint of 40 mm. The parallel linkage structure of the proposed mechanism requires that moving mechanical parts must be thin and located at the front of the shank. Using the data from foot pressure sensors, the device can recognize the gait phases. The output torque and angle data were collected to evaluate the performance of the device.

Abstract Spiking neurons communicate with other neurons using sparse and binary signals in a human brain, so they can achieve real-time processing of the information with ultra-low power consumption[1,2]. Thereby, spiking neurons are essential elements for building an energy-efficient biomimetic spatiotemporal system. Recently, to emulate the behavior of biological neuron, many researches for memristive device-based neurons with peripheral circuits (i.e., sense-amplifier or reset circuit)[3] and complementary metal-oxide-semiconductor (CMOS) neurons with capacitors have been reported[4]. Most of the reported memristive device-based neurons required a high operation voltage (>1.2 V) for emulating integrate function of a biological neuron. In addition, complementary metal-oxide-semiconductor-based neurons could not achieve high neuronal density due to using a capacitor in emulating integrate function. In this study, therefore, we propose an electrochemical metallization cell based memristive neuron chip fabricated with 28-nm CMOS process having a low operation voltage ( Acknowledgement This research was supported by National R&D Program through the National Research Foundation of Korea(NRF) funded by Ministry of Science and ICT(2021M3F3A2A01037733). Reference Mead, C. Neuromorphic Electronic Systems. Encycl. Comput. Neurosci. 78, 1979–1979 (2015). Douglas, R. Neuromorphic Analogue VLSI. Annu. Rev. Neurosci. 18, 255–281 (1995). Tuma, T., Pantazi, A., Le Gallo, M., Sebastian, A. & Eleftheriou, E. Stochastic phase-change neurons. Nat. Nanotechnol. 11, 693–699 (2016). Aamir, S. A., Müller, P., Hartel, A., Schemmel, J. & Meier, K. A highly tunable 65-nm CMOS LIF neuron for a large scale neuromorphic system. Eur. Solid-State Circuits Conf. 2016-Octob, 71–74 (2016). Figure 1

This letter proposes a multifunctional ankle exoskeleton to safely expand the mobility. By applying torque to the ankle in dorsiflexion and plantarflexion, the exoskeleton prevents foot drop and foot slip and helps the ankle to push off the ground. The exoskeleton includes a remote center-of-motion (RCM) mechanism, a linear actuation module, and fastening modules. The RCM mechanism, which has two degrees of freedom, is designed to be aligned with the talocrural and subtalar axes of the ankle. A key feature of the RCM mechanism is a three-dimensional combination of two four-bar linkage mechanisms that have the linear motion and rotational motion, respectively. Only the talocrural axis is actively actuated for dorsiflexion and plantarflexion of the ankle, whereas the subtalar axis is passively released to allow the unconstrained motion by the user. The active axis is driven by a linear actuation mechanism comprising a ball-screw and a brushless dc motor. The device can be separated into fastening modules and actuation module and weighs only 869 g/leg without the battery. The results of ground and treadmill tests indicate that the peak torque and average positive mechanical power delivered by the exoskeleton are approximately 20 N·m and 6.21 W, respectively.

Several research groups have developed and studied powered ankle exoskeletons to improve energetics of healthy subjects and the mobility of elderly subjects, or to reduce asymmetry in gaits induced by strokes. To achieve optimal effect, the timing of assistive torque has been proved to be of crucial importance. Previous studies estimated the onset timings mostly by extrapolating the time horizon from past gait events observed with sensors. Such methods have inherently limited performance when subjects are not walking at steady frequencies. To overcome such limitation and allow the use of exoskeletons in various scenarios in a daily life, we propose to estimate the gait phase as a continuous variable progressing over a gait cycle, hence allowing immediate response to frequency changes rather than iteratively correcting it after each cycle. Our method uses recurrent neural networks to estimate gait phases out of an inertial measurement unit (IMU) every 10 ms. By replacing foot sensors with an IMU we can obtain rich enough information to estimate gait phase continuously as well as avoid physical damage in sensors from ground impacts. Our preliminary tests with 2 healthy subjects showed qualitatively positive outcomes regarding the gait phase estimation and the assistive torque control.

Haptic feedback is critical for many surgical tasks, and it replicates force reflections at the surgical site. To meet the force reflection requirements, we propose a force sensor with an optical fiber Bragg grating (FBG) for robotic surgery. The force sensor can calculate three directional forces of an instrument from the strain of three FBGs, even under electromagnetic interference. A flexible ring-shape structure connects an instrument tip and fiber strain gages to sense three directional force. And a stopper mechanism is added in the structure to avoid plastic deformation under unexpected large force on the instrument tip. The proposed sensor is experimentally verified to have a sensing range from -12 N to 12 N, and its sensitivity was less than 0.06 N.

There are many important factors in developing an exoskeleton for assisting human locomotion. For example, the weight should be sufficiently light, the assist torque should be high enough to assist joint motion, and the assistance timing should be just right. Understanding how these design parameters affect overall performance of a complex human-machine system is critical for the development of these types of systems. The present study introduces an assistance timing controller that regulates assistance timing such that peak joint velocity and peak assistance power are offset by a reference value for our hip-type exoskeleton. This is followed by measuring the manner in which various assistance timing references affect an important metric for performance, namely metabolic cost. The results indicate that net metabolic cost exhibits a concave up pattern with the most reduction of 21%, when compared to walking without the exoskeleton, at 0% assistance timing reference. The study also examines assistance timing's effect on gait parameters; increase in assistance timing reference increases step length, decreases cadence, and increases walk ratio (i.e. step length/cadence ratio) during treadmill walking.

This paper presents a novel flexible sliding thigh frame for a gait enhancing mechatronic system. With its two-layered unique structure, the frame is flexible in certain locations and directions, and stiff at certain other locations, so that it can fît well to the wearer's thigh and transmit the assisting torque without joint loading. The paper describes the basic mechanics of this 3D flexible frame and its stiffness characteristics. We implemented the 3D flexible frame on a gait enhancing mechatronic system and conducted experiments. The performance of the proposed mechanism is verified by simulation and experiments.

This paper presents a novel self-aligning knee mechanism for walking assistance devices for the elderly to provide physical gait assistance. Self-aligning knee joints can assist in flexion/extension motions of the knee joint and compensate the knee's transitional movements in the sagittal plane. In order to compensate the center of rotation, which moves with the flexion/extension motion of the human knee joint, a self-aligning knee joint is proposed that adds redundant degrees of freedom (i.e., 2-DoF) to the 1-DoF revolute joint. The key idea of the proposed mechanism is to decouple joint rotations and translations for use in lower-extremity wearable devices. This paper describes the mechanical design of this self-aligning knee mechanism and its implementation on a wearable robot and in preliminary experiments. The performance of the proposed mechanism is verified by simulations and experiments.

The common requirements of rough terrain mobile robots are long-term operation and high mobility in rough terrain to perform difficult tasks. In rough terrain, excessive wheel slip could cause an increase in the amount of dissipated energy at the contact point between the wheel and ground or, even more seriously, the robot could lose all mobility and become trapped. This paper proposes a traction control algorithm that can be independently implemented to each wheel without requiring extra sensors and devices compared with standard velocity control methods. The proposed traction algorithm is analogous to the stick-slip friction mechanism. The algorithm estimates the slippage of wheels by angular acceleration change, and controls the increase or decrease state of torque applied to wheels Simulations are performed to validate the algorithm. The proposed traction control algorithm yielded a 65.4% reduction of total slip distance and 70.6% reduction of power consumption compared with the standard velocity control method.

When mobile robots perform the mission in the rough terrain, the traversability depended on the terrain characteristic is useful information. In the traversabilities, wheel-terrain maximum friction coefficient can indicate the index to control wheel-terrain traction force or whether mobile robots to go or not. This paper proposes estimating wheel-terrain maximum friction coefficient. The existing method to estimate the maximum friction coefficient is limited in flat terrain or relatively easy driving knowing wheel absolute velocity. But this algorithm is applicable in rough terrain where a lot of slip occurred not knowing wheel absolute velocity. This algorithm applies the tire-friction model to each wheel to express the behavior of wheel friction and classifies slip-friction characteristic into 3 major cases. In each case, the specific algorithm to estimate the maximum friction coefficient is applied. To test the proposed algorithm`s feasibility, test bed(ROBHAZ-6WHEEL) simulations are performed. And then the experiment to estimate the maximum friction coefficient of the test bed is performed. To compare the estimated value with the real, we measure the real maximum friction coefficient. As a result of the experiment, the proposed algorithm has high accuracy in estimating the maximum friction coefficient.

This paper introduces a wearable device which performs function of swinging chair with worn status on the legs. The users with the proposed device can sit in anyplace and experience the stable swing motion. The device is designed to maintain the stability within the stable swing region while moving back and forth by external forces or user intension. The coupled motion between ankle and knee provides the users concave swing motion in chair mode, while the joints passively follows the motion of the legs in normal gait mode. The key feature of this stable motion is a CAM-drive implemented around the ankle frame and connected to the knee joint by wires. With any directional motion of the ankle joint, the knee joint rotate only one direction to lift up the body of the user. So it can move following concave equilibrium line. We verified the payload of the device is more than 70 kg in computer-aided stress simulation as well as in experiments.

This paper introduces a novel surgical robot for single-incision laparoscopic surgeries. The robot system includes the cone-type remote center-of-motion (RCM) mechanism and two articulated instruments having a flexible linkage-driven elbow. The RCM mechanism, which has two revolute joints and one prismatic joint, is designed to maintain a stationary point at the apex of the cone shape. By placing the stationary point on the incision area, the mechanism allows a surgical instrument to explore the abdominal area through a small incision point. The instruments have six articulated joints, including an elbow pitch joint, which make the triangulation position for the surgery possible inside of the abdominal area. The presented elbow pitch structure is similar to the slider-crank mechanism but the connecting rod is composed of a flexible leaf spring for high payload and small looseness error. We verified the payload of the robot is more than 10 N and described preliminary experiments on peg transfer and suture motion by using the proposed surgical robot.

In this paper, we investigate a human exposure to wireless power transfer system operating at 1.8 MHz and 6.78 MHz. A method comprising a finite element method and a finite difference time domain is used for the numerical analysis of human exposure. The SARs of the Korean human body model are evaluated in relation to the different positions and orientation of wireless power transfer system. We discuss the numerical computation results along with the Non-Ionizing Radiation Protection (ICNIRP) guideline.

In this paper, we introduce a remote center-of-motion (RCM) mechanism with a conical shape for laparoscopic surgeries that involve a single incision. The mechanism, which has two revolute joints and one prismatic joint, is designed to maintain a stationary point at the apex of the conical shape. By aligning the stationary point with the incision area, the mechanism allows a surgical instrument to explore the abdominal area through a small incision point. We have previously analyzed the reachable workspace of this mechanism. Here, we arrange two RCM mechanisms on a single conical structure but separated in space to avoid mutual interference, so as to enable the entire system to manipulate two surgical instruments through a single incision point without colliding. We describe the operational principle of this system, in addition to comparisons of various RCM mechanisms and the kinematics for parameter design and motion control. Finally, we describe preliminary experiments on peg transfer and suture motion by using the proposed RCM mechanism.

This paper proposes a linkage-driven manipulator having linear ultrasonic motors inside of an elongated shaft. The manipulator can be divided into a driving rod module and wrist joint module. The driving rod module consists of several ultrasonic motors and driving rods. Flexible leaf springs between the ultrasonic motors and the driving rods enable synchronized motion of the driving rod by compensating mechanical clearance and different characteristics of ultrasonic motors. Two driving rods operate 2-DOF wrist module by linear motion. The wrist joint module is composed by two non-closing rotation joints, serially connected sliders and intermediate linkages, and designed to rotate from +60° to −60° in yaw and pitch directions respectively. The wrist parameters are determined by parametric studies of the motion range and torque characteristic, and the effect of the flexible leaf spring is studied by simulation. Experiments are performed in order to evaluate the velocity-force characteristic of the rod module.

Wheel robots have been widely used in indoor. An indoor room consists of various floor-types such as wood, carpet, marble and so on. The various floor-types cause odometry error and energy loss due to slip. Floor-type identification which allows a robot to detect changing floor-types and to adapt control and motion planning has been needed to solve this problem. In this paper, we propose sensing method for wheel robot to identify floor-types by using impedance variation. The impedance variation measures a voltage variation of a side brush motor depending on floor-types. The original side brush function is to sweep the dust in the vacuum cleaning robot. This approach does not require any sensors and estimates floor-types from the impedance variation. We present and analyze experimental data collected on three different floor-types: wood, marble and carpet. As a result, we verify the fact that the floor-types can be identified by the proposed method.

Many mobile robots have been developed in the various application fields, such as building inspection and security, military reconnaissance, space and undersea exploration, and warehouse services (Muir & Neuman, 1987). Mobile robots are designed with the specific locomotive mechanisms according to the environment of the application field. The various locomotive mechanisms used in mobile robots can be classified into three types: wheeled, tracked, and legged type (Kim, 1999) (Lee et al, 2000). Each locomotion type has its inherent advantages and disadvantages as described below. The wheeled mobile robots (WMRs) weigh less than robots of the other locomotive types and have other inherent advantages, such as high energy efficiency, low noise level, etc (Muir & Neuman, 1987). In comparison with legged mobile robots, the WMRs have a simpler driving part and a plain control strategy, but they have the poor adaptability to the terrain. Tracked mobile robots have the merit of easy off-road travelling. However, they usually have a heavier driving part and need more power for turning motions, in comparison with mobile robots with other locomotive types. Additionally, tracked mobile robots are usually too noisy to be utilized for in-door applications. Legged mobile robots can easily adapt to the unstructured environments, such as off-road environments, but require more actuators to stabilize themselves than mobile robots in the other two categories. As the locomotion mechanisms are complex and need more complicated control algorithms, legged mobile robots have poor mobility on the plane surfaces. Various types of mobile robots that are capable of climbing up stairs have been developed but, until now, most of the mobile robots developed have tracked-type locomotive mechanisms (Kohler et al., 1976) (Maeda et al., 1985) (Yoneda et al., 1997) (Iwamoto & Yamamoto, 1985) (Iwamoto & Yamamoto, 1990). For the purpose of developing a robot capable of traversing the stairs, Estier (Estier et al., 2000) proposed a WMR with three 4-bar linkage mechanisms, by applying the concept of the instantaneous centre of rotation. To explore Mars, Volpe (Volpe et al., 1997) developed a WMR named Rockey 7, which is capable of climbing up steps about 1.5 times as large as the wheel diameter. O pe n A cc es s D at ab as e w w w .ite ch on lin e. co m

This paper proposes a traction control algorithm which can be independently implemented to each wheel without extra sensors and devices compared with standard speed control. The algorithm estimates stick-slip of wheels based on estimation of angular acceleration so that the traction force induced by torque of wheel converses between maximum static friction and kinetic friction. Simulations are performed to verify the validity of the algorithm. The proposed traction control algorithm obtained 40.5% reduction of total slip distance and 48.4% reduction of dissipated work on the contact point compared with standard speed control. Furthermore, the algorithm does not require complex wheel-soil interaction model and optimization of robot kinematics.

In this paper, we propose a vision-based simultaneous localization and map-building (SLAM) algorithm using compressed extended Kalman filter (CEKF). SLAM addresses the problem of locating a mobile robot in unknown environments. Extended Kalman filters (EKF) are widely used to solve this problem. However, this filter is very time consuming. To reduce the computational complexity, we apply a CEKF to stereo images while compensating for some of the limitation shown in previous implementations of CEKF. Moreover, we estimate the full DOF, its position and pose, of the mobile robots which is required when operating in the outdoor environment. Outdoor experiments have been conducted to test the effectiveness of the proposed SLAM algorithm.

The purpose of this paper is to provide a practical introduction to a mobile robot developed for rescue operations. The robot has a variable single-tracked mechanism for the driving part, making it inherently able to overcome indoor obstacles such as stairs. In this research, the robot is given the capacity of obstacle negotiation as a hardware attachment in order to realize autonomous navigation that is well matched to an original target, rescue operation. There are three driving modes to choose from, and the robot recognizes the forward environment once and estimates whether or not any obstacles are there. Experimental results show that the robot moves in opposition to several obstacles, reflecting the proposed algorithm ultimately.

Piezoelectric motors have been used in many applications where excellent controllability and fine position resolution are required or magnetic field noise should be eliminated. However, the piezoelectric motor has two major drawbacks. One is difficulty in maintaining constant vibration amplitude with temperature rise and wear, and the other is heat generation induced by dielectric and mechanical losses. A piezoelectric motor that can overcome these problems is proposed. It is operated using momentum exchange between a bimorph and a rotor. To maximize the motor's steady state velocity and static torque, a guideline is established using two bimorph models. The guideline is then partially validated by comparison between simulation and experiment results. There was no heat generation in several hours of testing.

Autonomous mobile robot increasingly expands its functionality into various applications where the long-term autonomous capability is necessary. These applications, warehouse service, building inspection, exploration of unknown terrains and military reconnaissance, require the mobile robot to correspond with the command of remote operators or environments. To meet this requirement, automatic recharging station can be used for a robot not to be taken offline. However, the range of docking error is wide by various homing algorithms and kinds of sensors. This paper describes a new docking mechanism developed to compensate entry error of robot in homing and to maintain robust state in the process of recharging battery without actuators and sensors. The proposed mechanism is self-adjustable to position and orientation of robot and reconfigures its states by driving force of mobile robot without any active energy elements. The geometric parameters are determined to avoid mechanical interference in docking procedure and specifications of springs are obtained from optimization which maximizes the grip force with constraint induced at each docking process. The docking mechanism can compensate for ±5cm lateral offset error and ±30° orientation error of mobile robot and holds it over 20N load after docking is finished.Copyright © 2006 by ASME

The purpose of this project is to develop a mobile robot for hazardous terrain exploration. The exploration of hazardous terrain requires the development of a passive mechanism adaptable to such terrain and a sensing system for obstacle avoidance, as well as a remote control. We designed a new mobile robot, the Ronahz 6-wheel robot, which uses a passive mechanism that can adapt to hazardous terrains and building stairways without any active control. The suggested passive linkage mechanism consists of a simple four-bar linkage mechanism. In addition, we install a stereo vision system for obstacle avoidance, as well as a remote control. Wide dynamic range CCD cameras are used for outdoor navigation. A stereo vision system commonly requires high computational power. Therefore, we use a new high-speed stereo correspondence algorithm, triangulation, and iterative closest point (ICP) registration to reduce computation time. Disparity maps computed by a newly proposed, high-speed method are sent to the operator by a wireless LAN equipment. At the remote control site, a three-dimensional digital map around a mobile robot is built by ICP registration and reconstruction process, and this three-dimensional map is displayed for the operator. This process allows the operator to sense the environment around the robot and to give commands to the mobile robot when the robot is in a remote site.Copyright © 2004 by ASME

Piezoelectric motors have been used in many applications where excellent controllability and fine position resolution are required and/or magnetic-field noise should be eliminated. However, the piezoelectric motor has two major drawbacks, difficulty in maintaining vibration amplitude constantly with temperature rise and wear and heat generation induced by dielectric and mechanical losses. In this article, a new piezoelectric motor that can overcome these problems is proposed. The proposed piezoelectric motor is operated using momentum exchange between four bimorphs and a rotor. In order to maximize the steady-state velocity and static torque of the proposed motor, a guideline is established using two bimorph models. The guideline is partially verified by comparison between simulations and experiments. There was no heat generation in a few hours of operation in experiments.