A human foot with high degrees of freedom (DOF) that has multi-DOF toe joints and a two-DOF ankle provides multiple benefits, such as increased stride length and walking speed, impact mitigation, and enhanced balancing. However, creating such mechanisms for legged robots has been challenging due to increased complexity, heavy weight, and vulnerability to impact. In this paper, a novel leg and toe mechanism inspired by human biomechanics, featuring a one-DOF knee joint, two-DOF ankle joint, and one-DOF toe joint, is developed. All actuators are located at the proximal part of the thigh frame to minimize the distal mass. High payload timing belts and unique linkage mechanisms are utilized in the transmission to achieve high backdrivability and high joint stiffness. Actuation torques are intentionally coupled inspired by human anatomy, enduring the high propulsive force to the ground for dynamic movements, such as jumping. The implemented leg and toe mechanisms weigh 8.16 kg, and the height from the ground to the hip center is 786 mm. The proposed mechanism has been proven to be effective through force test and distance jump experiments.

We introduce StaccaToe, a human-scale, electric motor-powered single-leg robot designed to rival the agility of human locomotion through two distinctive attributes: an actuated toe and a co-actuation configuration inspired by the human leg. Leveraging the foundational design of HyperLeg’s lower leg mechanism, we develop a stand-alone robot by incorporating new link designs, custom-designed power electronics, and a refined control system. Unlike previous jumping robots that rely on either special mechanisms (e.g., springs and clutches) or hydraulic/pneumatic actuators, StaccaToe employs electric motors without energy storage mechanisms. This choice underscores our ultimate goal of developing a practical, high-performance humanoid robot capable of human-like, stable walking as well as explosive dynamic movements. In this paper, we aim to empirically evaluate the balance capability and the exertion of explosive ground reaction forces of our toe and co-actuation mechanisms. Throughout extensive hardware and controller development, StaccaToe showcases its control fidelity by demonstrating a balanced tip-toe stance and dynamic jump. This study is significant for three key reasons: 1) StaccaToe represents the first human-scale, electric motor-driven single-leg robot to execute dynamic maneuvers without relying on specialized mechanisms; 2) our research provides empirical evidence of the benefits of replicating critical human leg attributes in robotic design; and 3) we explain the design process for creating agile legged robots, the details that have been scantily covered in academic literature.

This paper presents an adjustable knee joint for a wearable robot for the elderly, to provide physical gait assistance. In order to compensate for the translational and rotational movements of the knee in the sagittal plane as well as aligning the frontal plane, the proposed knee joint is implemented with a rolling joint, two aligning passive joints, four-bar linkage, and a sliding mechanism. Because the sliding mechanism, four-bar linkage, and rolling joint exist between the actuator and the joint mechanism, the rotation angle of the actuator and the flexion angle of the rolling joint do not change equally due to the kinematic characteristics. In order to define the flexion angle change of the rolling joint with respect to the change to the actuator angle in the flexion/extension motion of knee, the design parameters and flexion model are proposed in this paper. The proposed artificial knee joint effectively delivers the torque required for assistance while adapting to the joint motion of the wearer. This paper describes the mechanical design of this knee mechanism and its implementation on a wearable robot and in preliminary experiments. The performance of the proposed mechanism was verified by simulations and experiments. Finally, preliminary experiments were performed to demonstrate the possibility of reducing the metabolic cost of using a knee assist.

This paper presents a three-degrees-of-freedom (DOF) gravity compensation mechanism for the waists of cooperative robots whose centers of mass change according to the arm poses. It comprises 2-DOF and 1-DOF gravity compensation mechanisms in series, and is capable of natural and agile motions such as bobbing and weaving. The 2-DOF mechanism for the upper part of the waist acts as a universal joint. To compensate for the gravity of this 2-DOF motion, a simple and robust link mechanism with one compressive spring is proposed. Moreover, for the complete gravity compensation regardless of the arm poses, a three-dimensional (3D) parallel link structure that maintains the upper body parallel to the ground is introduced. The 1-DOF gravity compensation mechanism, which provides the motions of the hip and thigh, also has a parallelogram structure to maintain the waist parallel to the ground. The implemented 3-DOF waist mechanism can compensate for up to 23 kg and its own weight. It has an adjusting mechanism that can easily calibrate the amount of compensation in case the weight of the upper body changes. The large workspace enables the upper body to move in any direction in a 3D space without singularity. Therefore, the robot with this waist can touch the ground to pick up objects on the ground as well as reach an object at a height of 2145 mm.

This paper presents a dexterous three degree-of-freedom (3-DOF) wrist mechanism with a large range of motion and uniform manipulability without singular points throughout the entire range of motion. It has a 2-DOF spherical pure rolling joint surrounded by two pairs of actuating wires, the motions of which directly represent the quaternion values of the joint; this joint is therefore named the quaternion joint. Based on this property, it has simple and clear forward and inverse kinematics and high manipulability. By adding a 1-DOF rotation joint at the distal end of the quaternion joint, it can be extended to a 3-DOF joint mechanism. To precisely approximate the spherical pure rolling motion in a confined central space, a novel parallel mechanism composed of three identical supporting linkages was introduced. Unlike conventional parallel mechanisms, it has a compact and simple structure with no interference among the supporting linkages. Because the wrist mechanism is a tendon-driven mechanism, and is thus suitable for lightweight manipulators, it is mounted to a low-inertia manipulator with high stiffness and strength, namely, LIMS2-AMBIDEX, which is an improved version of the authors' previous research. The basic concept and thorough theoretical analysis of the wrist mechanism are described herein, and the simulations and experiments conducted for a quantitative validation are presented.

In this paper, a dual-arm robot system for high-speed manipulations, which is named LIMS2-AMBIDEX and is developed to compete in the IROS2018 Robotic Challenge, is presented. It has two seven-degrees-of-freedom (DO$F$) lightweight arms, a three-DOF head, and a one-DOF gripper to manipulate foldable objects. Because all the heavy actuators are placed at the shoulder, it has remarkably low mass beyond the shoulder (2.63 kg), which guarantees an inherent safety at high speeds. Utilizing tension-amplification mechanisms, the high stiffness and strength are achieved, and thus it has the control performance comparable to conventional industrial manipulators. A unique three-DOF wrist mechanism, whose motions directly represent the quaternion values of the joint orientation, can manipulate objects without singular points in the entire range of motion. In order to utilize the object's inertia during rapid manipulation, the gripper was specially designed: it has a one-DOF finger to grasp the upper rib of the foldable fan and two supporting forks to grasp the bottom rib stably. For real-time performance and increased scalability, a software framework was developed based on Robot Operating System (ROS). The real-time capability is achieved by using the real-time development framework Xenomai and the high-speed communication protocol EtherCAT. As most of the algorithms are implemented in the distributed nodes using ROS, it is convenient to expand, improve, and replace the algorithms. Consequentially, the entire motion of the Fan Robotic Challenge Phase I Modality B required 1.05 s, which is substantially faster than a similar manipulation by most humans.

This paper presents an adjustable knee mechanism for walking assistance devices for the elderly to provide physical gait assistance. The adjustable knee mechanism can assist in flexion/extension motions of the knee joint and compensate for the transitional movements of the knee in the sagittal plane as well as aligning the frontal plane. In order to compensate for the center of rotation, the proposed adjustable knee mechanism is implemented by connecting several rolling cams with unique and precisely calculated contact geometries. The key idea of the proposed mechanism is to realize linear motion and accurate torque transmission by a pulley method using the rolling joint in which the distance of the center between the rolling cams is changed. The proposed articulated joint can effectively deliver the torque required for assistance while adapting to the joint motion of the wearer. This paper describes the mechanical design of this knee mechanism and its implementation on a wearable robot and in preliminary experiments. The performance of the proposed mechanism was verified by simulations and experiments.

This paper presents a high-force grip assist glove composed of soft and flexible materials. By using a new force distributing compliant structure, the proposed glove can assist high gripping force while adapting to human hand motion, which is difficult for conventional soft robotic gloves. The force distributing compliant structure is comprised of flexible frames, soft fabrics and belts, and can transmit a high force or moment to the distal end, even though the whole structure is flexible. Therefore, the proposed glove can assist gripping without a harmful load or misalignment on the human fingers. The palmar side of the glove is made of a thin and soft fabric and belts to facilitate the transfer of tactile sensation. The proposed assist glove enables the user to manipulate various objects owing to both the softness and high gripping force. The basic concept as well as thorough theoretical analysis about the force distributing compliant structures is described, and the experiments for quantitative validation of the developed assist gripper are presented.

This paper proposes a new concept called “a flexible exoskeleton” and presents the design of a wearable walking assistance device to provide physical gait assistance for the elderly. To overcome some limitations of previous wearable walking assistance devices, 3 novel mechanisms are proposed: 1) flexible thigh frames that withstand the designated load direction, 2) an adjustable flexible hip brace surrounding the wearer's body, and 3) slim and backdrivable actuators that minimize the maximum height and resistance. The proposed walking assistance device has reduced metabolic energy consumption by 13.2±4% compared with a free condition.

In this paper, a manipulator is proposed for safe human-robot interaction at high speed. The manipulator has both low mass and inertia and high stiffness and strength. It is basically a cable-driven manipulator; nevertheless, by using a unique lightweight tension-amplification mechanism, the manipulator retains high stiffness and strength. The joint stiffness, which is strongly related to the motion control performance, is amplified by the quadratic order. Both 1-degree of freedom (DOF) and 3-DOF joint mechanisms using the tension-amplification mechanism are presented and combined to develop a 7-DOF anthropomorphic manipulator named LIMS. The mass and inertia beyond the shoulder were 2.24 kg and 0.599 kg·m2, respectively, which are lower than those of a human. The stiffness of the developed elbow joint was 1410 N·m/rad, which is approximately seven times higher than that of a human. Considering the ratio of stiffness to inertia, the manipulator is expected to show a control performance that is comparable to those of conventional industrial manipulators. Comprehensive experiments, including joint stiffness tests and high-speed interaction tests, were conducted to verify the feasibility of the developed manipulator.

This paper presents a novel manipulator for human-robot interaction that has low mass and inertia without losing stiffness and payload performance. A lightweight tension amplifying mechanism that increases the joint stiffness in quadratic order is proposed. High stiffness is essential for precise and rapid manipulation, and low mass and inertia are important factors for safety due to low stored kinetic energy. The proposed tension amplifying mechanism was applied to a 1-DOF elbow joint and then extended to a 3-DOF wrist joint. The developed manipulator was analyzed in terms of inertia, stiffness, and strength properties. Its moving part weighs 3.37 kg, and its inertia is 0.57 kg·m2, which is similar to that of a human arm. The stiffness of the developed elbow joint is 1440Nm/rad, which is comparable to that of the joints with rigid components in industrial manipulators. A detailed description of the design is provided, and thorough analysis verifies the performance of the proposed mechanism.

This paper presents a 14-DOF robotic hand including 5 fingers and a wrist. The hand has a new tendon-driven mechanism which minimizes frictional loss and maximizes efficiency and backdrivability. In order to accomplish high efficiency and backdrivability as well as human-like payload and dexterity in a compact size, two novel mechanical concepts are proposed. Firstly, the actuators are placed according to the functions of fingers - high power grasping and precise manipulation - instead of positioning at each joint. For the high power grasping, 7 high payload motors are positioned in the forearm, and 5 small size motors are positioned in the palm for the precise manipulation. Secondly, a new tension decoupling mechanism is proposed to the 2-DOF wrist joint, which delivers wire motions of the forearm motors to the fingers without frictional loss or coupling with wrist motion. A total weight including the forearm is 1.59kg which is similar to human. The fingertip force is 15N which is sufficient for most of household work. High backdrivability enables the contact force sensing by measuring a motor current without additional sensors. A detectable minimum contact force was 0.735N. In order to enhance the contact force sensing capability, a friction compensation algorithm was applied, which resulted to the minimum contact force as 0.196N. Theoretical and experimental analyses are also performed.

In this paper, we present a modeling and control method for a single-port access robot developed by our robotics group at the Samsung Advanced Institute of Technology. The surgical robot consists of a snake-like 6-degree-of-freedom (DOF) guide tube, two 7-DOF tools, a 3-DOF stereo camera, and a 5-DOF slave arm. The robot is capable of reaching various surgical sites inside the abdominal cavity from a single incision on the body. To estimate the workspace and control the guide tube to a desired location, we first obtain the forward kinematics model of the guide tube and then propose a Cartesian-level controller. The wire actuation mechanism for the tools exhibit nonlinear backlash behavior because of wire compliance and friction between the wire and Teflon-coated conduit. We compensate for the backlash in the tool joints by adding the backlash inverse with smoothing term as a feedforward term.

In robotic single-port surgery, it is desirable for a manipulator to exhibit the property of variable stiffness. Small-port incisions may require both high flexibility of the manipulator for safety purposes, as well as high structural stiffness for operational precision and high payload capability. This paper presents a new hyperredundant tubular manipulator with a variable neutral-line mechanisms and adjustable stiffness. A unique asymmetric arrangement of the tendons and the links realizes both articulation of the manipulator and continuous stiffness modulation. This asymmetric motion of the manipulator is compensated by a novel actuation mechanism without affecting its structural stiffness. The paper describes the basic mechanics of the variable neutral-line manipulator, and its stiffness characteristics. Simulation and experimental results verify the performance of the proposed mechanism.

In this paper, tension propagation analysis of a newly designed multi-DOF robotic platform for single-port access surgery (SPS) is presented. The analysis is based on instantaneous kinematics of the proposed 6-DOF surgical instrument, and provides the decision criteria for estimating the payload of a surgical instrument according to its pose changes and specifications of a driving-wire. Also, the wire-tension and the number of reduction ratio to manage such a payload can be estimated, quantitatively. The analysis begins with derivation of the power transmission efficiency through wire-interfaces from each instrument joint to an actuator. Based on the energy conservation law and the capstan equation, we modeled the degradation of power transmission efficiency due to 1) the reducer called wire-reduction mechanism, 2) bending of proximal instrument joints, and 3) bending of hyper-redundant guide tube. Based on the analysis, the tension of driving-wires was computed according to various manipulation poses and loading conditions. In our experiment, a newly designed surgical instrument successfully managed the external load of 1kgf, which was applied to the end effector of a surgical manipulator.

This paper presents a novel “layer jamming” mechanism that can achieve variable stiffness. The layer jamming mechanism exploits the friction present between layers of thin material, which can be controlled by a confining pressure. Due to the mechanism's hollow geometry, compact size, and light weight, it is well suited for various minimally invasive surgery applications, where stiffness change is required. This paper describes the concept, the mathematical model, and a tubular snake-like manipulator prototype. Various characteristics of layer jamming, such as stiffness and yield strength, are studied both theoretically and experimentally.

This paper introduces a new mechanism for achieving tunable stiffness, named layer jamming, and presents a hollow snake-like manipulator having tunable stiffness capability. The layer jamming mechanism is composed of multiple layers of thin Mylar film, and makes use of amplified friction between the films by applying vacuum pressure. In contrast to other tunable stiffness technology, such as particle jamming or field-activated materials (MR or ER fluids), layer jamming occupies a small volume and thus can be applied to small, light weight manipulators. The snake-like manipulator presented here is composed only of Mylar film and wires, and has highly flexible and under-actuated properties without application of a vacuum; however, it becomes highly stiff when a vacuum is applied. In this paper the characteristics of layer jamming are explored: its stiffness and breaking strength are obtained both theoretically and experimentally, and a prototype manipulator is developed and experimentally characterized.

This paper proposes a behavior selection mechanism and interactive learning method for a synthetic character. Synthetic character can decide its behavior by itself based on its own internal states (motivation, homeostasis, and emotion), and external sensor information. A behavior is selected by both probabilistic and deterministic methods. The probabilistic method uses the internal states and external sensor information, and the deterministic method which imitates animal's instinct, uses only external sensor information. Both methods are complementary to each other. A user can teach the synthetic character a desired behavior among many behaviors, and behaviors are grouped into analogous behavior sets. The learning algorithm includes the emotional parameters by which the training efficiency is affected. The performance of the synthetic character, Rity, developed with the proposed mechanism at RIT Lab., KAIST is demonstrated in a 3D virtual world.

Describes the implementation of an Internet-based personal robot with three control modes, and experimental results on the remote control between KAIST, Korea and UC Davis, USA. The idea is to control a personal robot at the remote site (KAIST) by using a simulator provided at the local site (UC Davis). However, if the information of the current absolute position of the robot at its remote site cannot be estimated, the simulator may be useless. The absolute position of the robot can be determined by comparing a reference map with sensor information from sonar sensors and an electronic compass. A user can use three control modes-direct control mode, supervisory control mode and job scheduling mode, and monitor the current status of the robot using a graphic user interface of the simulator implemented with Java.

Describes the implementation of an Internet-based personal robot with direct Internet control architecture which is insensitive to the inherent Internet time delay. The personal robot can be controlled by using a simulator provided at a local site. However, a large Internet time delay may make some control inputs distorted. Moreover, since it is affected by the number of the Internet nodes and loads, this delay is variable and unpredictable. The proposed control architecture guarantees that the personal robot can reduce the path error and the time difference between a virtual robot at the local site and a real robot at the remote site. Simulations and experimental results in the real Internet environment demonstrate the effectiveness and applicability of the Internet-based personal robot with the proposed Internet control architecture.

Most of navigation techniques with obstacle avoidance do not consider the robot orientation at the target position. These techniques deal with the robot position only and are independent of its orientation and velocity. To solve these problems this paper proposes a novel univector field method for fast mobile robot navigation which introduces a normalized two dimensional vector field. The method provides fast moving robots with the desired posture at the target position and obstacle avoidance. To obtain the sub-optimal vector field, a function approximator is used and trained by evolutionary programming. Two kinds of vector fields are trained, one for the final posture acquisition and the other for obstacle avoidance. Computer simulations and real experiments are carried out for a fast moving mobile robot to demonstrate the effectiveness of the proposed scheme.

An online map building evolutionary algorithm is proposed using multi-agent mobile robots with odometric uncertainty. The control algorithm for map building in each robot is identical and trained by an online evolutionary algorithm (EA). Each robot has configuration uncertainty which increases as it moves, and it perceives the surrounding environment information by the limited range sensors. It communicates with other robots and shares the information. The elementary behaviors are defined and they are used to build a map. EA is applied to the defined behavior set for optimizing the robot actions. To demonstrate the effectiveness of the proposed algorithm, computer simulations are conducted for various environments.

A real time vector field based path planning for an attack mode robot and a Petri net state diagram approach for the robot's role selection for robot soccer games are proposed in the paper. A robot soccer game has a dynamic environment as different robots intentionally affect the environment in unpredictable ways in a competitive setting. A soccer-playing robot has to take appropriate action according to its surroundings. The efficiency and applicability of the proposed controllers were demonstrated through real robot soccer games in MiroSot'97, held at KAIST Korea, June 1-5, 1997.