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.

We developed a robotic lower-limb exoskeleton for those who have weakened muscle due to aging and experience difficulty in walking or getting up without help. The exoskeleton covering both limbs from the feet to the waist has 6 electric actuators in the hip abduction/adduction, hip extension/flexion and knee extension/flexion joints. For users with volitional motion, delivering assistance power according to their intention is a challenging task. We propose an adaptive oscillator-based controller to assist users walk in the lower-limb exoskeleton. To adapt to changes in walking speed and environment, motion command from the controller is modulated by estimate walking speed and walking environment recognized as one of the following categories: level ground, stairs up/down and slope up/down. Experimental results demonstrate the feasibility of the proposed environment recognition method and the impact of assistance on the metabolic cost of walking on level and inclined treadmills.

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 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, 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.

In this paper, we present a global localization and local pose error compensation method in a known structured environment using magnetic landmarks. In previous our research, it was possible to compensate the pose error (xe, ye, qe) of a mobile robot correctly on the surface of structured environment with magnetic landmarks. In this work, we propose a methodology of arranging magnetic landmarks on the map such that properly arranged magnetic patterns ease the global localization of a mobile agent. Among total six patterns of magnetic-bar in square arrangement, five unique landmarks are obtained. Therefore, a heuristic pattern search method is applied to build the virtual map using five landmarks. In order to obtain the global pose information, the robot identifies the pattern of magnets, and obtains the current global pose information by comparing the measured neighboring patterns with the map information that is saved in advance. Experimental results show the effectiveness of the magnetic-pattern landmarks for the global localization and local pose control of a mobile robot.

Surface roughness is one of the most intractable physical properties and its sensing heavily depends on the application and the capability of the sensor. In this paper, a pen-type sensor is proposed for sensing surface roughness. The sensor with a rigid contact probe is able to measure 3D contact forces and the dynamic contact responses along the axial direction of the probe, which facilitate the roughness representation using parameters of roughness profile rather than complex, high level interpretation methods. Strain gauges and a force sensor are used for measuring contact forces and a PVDF sensor is used for the dynamic sensing. The sensor is a self-contained one, and it can transmit sensed data via Bluetooth to the host computer. As preliminary tests, experiments are performed on the measurement of the coefficient of friction and the response to dynamic stimuli of different surface patterns.

In this paper a hand-held sensor for surface texture perception is presented. The sensor with a metal contact probe is able to measure the roughness and frictional property of a surface, which are among the most important parameters for contact texture perception. Two strain gauges and a force sensor are employed to measure 3D-contact forces at the tip of the contact probe. The friction coefficient can be calculated by using the normal force and tangential one. A PVDF film is used for the dynamic sensing of contact stress in the axial direction of the contact probe. Measurement results are transmitted to a host computer via Bluetooth wireless communication link for further data processing. Design issues are discussed in details, and the preliminary experimental evaluations are performed.

In this paper, an anthropomorphic robot hand called SKKU Hand II is presented, which has a miniaturized fingertip tactile sensor. The thumb is designed as one part of the palm and provides the mobility of the palm. The fingertip tactile sensor, based on polyvinylidene fluoride (PVDF) and pressure variable resistor ink, is physically flexible enough to be deformed into any three-dimensional geometry. In order to detect incipient slip, a PVDF strip is arranged along the direction normal to the surface of the finger of the robot hand. Also, a thin flexible sensor to sense the static force as well as the contact location is fabricated into an arrayed type using pressure variable resistor ink. The driving circuits for the SKKU Hand II are embedded in the hand, and each driving circuit communicates with others using CAN protocol. In addition, a tactile sensing system is developed with miniaturized electronic hardwares such as charge amplifier, signal processing unit etc., and it is integrated into the robot hand. The SKKU Hand II is manufactured and feasibility of the hand and the fingertip tactile sensor is validated through preliminary experiments

In this paper, a fingertip tactile sensor is presented which can detect contact normal force as well as incipient slip. The sensor, based on polyvinylidene fluoride (PVDF), and pressure variable resistor ink, is physically flexible enough to be deformed into any three-dimensional geometry. In order to detect incipient slip, a PVDF strip is arranged along the direction normal to the surface of the finger of the robot hand. Also, a thin flexible sensor to sense the static force as well as the contact location, is fabricated into an arrayed type using pressure variable resistor ink. In addition, a tactile sensing system is developed with miniaturized electronic hardware such as charge amplifier, signal processing unit etc., and it feasibility is validated experimentally.