Robotic orthoses have potential to assist people having difficulty in walking due to their neurological disorders. However, it is important to design lighter orthoses since additional weight and inertia from the device cause discomfort to the wearer and even instability during walking in some extreme cases. To address this problem, a robotic orthosis with a cable differential mechanism is proposed in this paper. It is designed to assist stroke patients with hemiplegia. It has 2 active degrees of freedom at the hip and knee joints and one passive degree of freedom at the ankle. A cable differential mechanism is used to transmit the torques generated by the actuators, which are located near the pelvis of the wearer to reduce the inertial effect. The cable differential mechanism allows for the actuators to share the load with each other, which results in decrease of the maximum required torques by the actuators. Therefore, smaller actuators are possible to be used for further reduction of the weight. The proposed robotic orthosis with a cable differential mechanism, which is called “COWALK-Mobile 2,” is implemented and evaluated.

Simultaneous communications over parallel channels is a prominent scheme in modern wireless system. Intuitive multi-channel solution allocates one independent RF chain (including LNA, low-noise amplifier) to each separate channel, causing high implementation cost. Alternatively, low-cost RF uses one single LNA to cover all parallel channels and save implementation cost. Nevertheless, such structure introduces challenges in the control of shared LNA gain (as well as channel power allocation), especially when adapting to independent fadings across parallel channels. Under shared-LNA strucutre, and to maximize energy efficiency, this paper proposes a sub-gradient framework that optimizes both shared-LNA gain and channel power values under multiple system constraints, including Tx power, ADC saturation, baseband SNR, and LNA gain. We discuss algorithm properties including convergence performance, step size selection, and solution accuracy. Simulation results confirm that, optimized energy efficiency through our algorithm can outperform intuitive strategies by 20% to 160%. Finally, impacts of various system parameters are studied as well.

While compliance control scheme is done for the wearable robot combined with the linear actuator and sensor on it as intended by the user, oscillations occur due to the joint kinematical mechanism. In this paper, the cause of oscillation on the knee joint is analyzed in detail. Also, it is shown that the moment arm is varied with joint angle, it is confirmed that sensed pressure is changed by the variation. In addition, for canceling the oscillation, torque sensor - using the method to move its force/pressure sensor position from the cylinder to the joint, and a wire-pulley system that adjusts the moment arm with a mechanical impedance compensation are proposed. Finally, simulations and experiments are done for demonstrating oscillation reduction by using the DSME wearable robot.

In this study, we evaluated a fast training algorithm to decode human hand configuration from sEMG signals on the forearms of five subjects. Eight skin surface electrodes were placed on the forearm of each subject to detect the sEMG signals corresponding to four different hand configurations and relax state. The preamplifier, which has 100 - 10000 times amplification gain and a 15 - 500 Hz bandpass filter, was designed to amplify the signals and eliminate noise. In order to enhance the performance of the classifier, feature extraction using class information was developed. The randomly assigned non-update learning method guarantees high speed classifier learning. The algorithm has been verified by experiments with five subjects.

Trotting on irregular terrain is a difficult task as undesirable impulse force by collision between robot foot and an obstacle makes the robot unstable. To cope with the problem, in this paper, variable impedance control algorithm changing leg impedance parameters according to the change of finite trot states is proposed. The state of quadruped trot is divided into five phases and the impedance parameters are changed to generate adequate response to the contact force in each locomotion phase. Simulation of trotting on irregular terrain with half-ellipsoidal trajectory has been performed with the control groups. The simulation has verified that the proposed control method shows outstanding performance and better stability for trotting on the highly irregular terrain.

This paper proposes a new hybrid structure for the practical MIMO receiver. The receiver operates in a QRMLD mode by default and achieves near-optimal performance. On the other hand, when the communication environment is not so favorable for a QR-MLD, it switches to a QR-MMSE mode and saves the mobile computing power. Using a common structure of QR decomposition from both receivers and the novel QR-MMSE un-biasing technique, this hybrid receiver can be implemented with great simplicity.

This correspondence proposes a control method for biped robots walking on a geometrically uneven surface with irregular protrusions. The focus is to maintain robot stability in leg and foot motions in order to adapt the foot to uneven terrains. Under the assumption that contact sensors are evenly installed at the foot soles, the geometric information under the landing foot is represented by a terrain matrix, whose elements represent the height of protruded cones. The control strategy of a landing phase (LP) is to form a large polygon with the contact points between the foot and the ground, based on the current zero-moment point (ZMP) and the locations of contact points during the transition from the LP to the stable double-support phase. The center of the polygon formed by the contact points at the end of the LP is to be used as the ZMP when the trajectory for the next step is generated. The gravity-compensated inverted-pendulum-mode-based trajectory is modified based on the newly located ZMP position and is interpolated to remove any trajectory discontinuity and to ensure a smooth transition. A series of computer simulations of a 28-degree-of-freedom (DOF) biped robot with a six-DOF environment model using SimMechanics shows that a stable compliant locomotion on uneven surfaces is successfully achieved with the proposed method.

In this paper we proposed a practical robust controller which has simple structure, more easy tuning factor, and control forms having direct relation with control performance. This robust control is designed using the motor side dynamics directly. The design procedure consists of three parts. A model based computed torque control part to decrease stead-state errors, a feedback based control part to increase control accuracy, and robust control part to maintain the tracking performance using the nonlinear H-infinity control. The designed robust control is applied to a 6 DOF robot manipulator with joint flexibilities. The proposed robust controller has better tracking performance and advantage in its application.

Flexible joint robot manipulators can be decomposed into two cascaded subsystems, a series connection of robot link dynamics and joint dynamics. For these flexible manipulators, we propose the robust controller using a recursive design method. The recursive design procedures are constructive and contain two steps. First, a fictitious robust controller for the robot link dynamics is designed as if the link dynamics had an independent control. As the fictitious control, a nonlinear Hinfincontrol using the energy dissipation is designed in the sense of L2-gain attenuation from the disturbance caused by uncertainties to performance. Second, a real robust control is designed recursively by using a Lyapunov's second method. The designed robust control is applied to a 2 DOF robot manipulator with joint flexibilities.

This paper proposes a robust back-stepping control method for flexible joint robot manipulators to overcome parameter uncertainty. In the first step, a virtual control is designed for the rigid link dynamic by the nonlinear H-infinity method. In second and third steps, the other virtual control and real control are designed using the saturation-type nonlinear control based on the Lyapunov’s second method. In each step, the designed robust inputs satisfy the L2-gain, which is equal to or less than — in the input-output sense of the closed loop system. In contrast with the previous researches, the proposed control method does not need the information of the acceleration and desire jerk of the links for the feedback control law. The performance robustness of the proposed control is verified through a series of computer simulations of a 2-DOF robot manipulator with joint flexibility.

In this paper, we propose a new parallel mechanism of biped robots, each of its legs is composed of two 3-DOF parallel platforms linked serially. The thigh possesses three active linear actuators with a constraint bar and seven passive joints, the shank has two linear actuators to operate pitch and roll motion at the ankle and a rotational actuator for the pitch at the knee. To generate locomotion trajectory for the proposed robot, we adopt the genetic algorithm for minimizing energy consumption. For the fast convergence and efficiency, the RCGA (real coded genetic algorithms) is used. A trajectory is represented by 4-th order polynomials whose coefficients are chromosomes. Equality conditions reflect the start and end position of swing leg and the repeatability condition for stable walking is used with inequality conditions to describe kinematics constraints for swing motion and ZMP (zero moment point) conditions. To demonstrate the effectiveness and performance of the proposed structure and trajectories, computer simulations were executed using SimMechanicsreg

During the communication and interaction with a human using motions or gestures, a humanoid robot needs to not only look like a human but also behavior like a human to avoid confusions in the communication and interaction. Among human-like behaviors, arm motions of the humanoid robot are essential for the communication with people through motions. In this work, a mathematical representation for characterizing human arm motions is first proposed. The human arm motions are characterized by the elbow elevation angle that is determined using the position and orientation of human hands. That representation is mathematically obtained using an approximation tool, response surface method (RSM). Then, a method to generate human-like arm motions in real time using the proposed representation is presented. The proposed method was evaluated to generate human-like arm motions when the humanoid robot was asked to move its arms from a point to another point including the rotation of hand. An example motion was performed using the KIST humanoid robot, MAHRU

In this paper, we propose optimal trajectories of biped robots to move a staircase up and down using genetic algorithms and computed-torque controller to be dynamically stable. Firstly, in order to minimize the total energy efficiency, the real-coded genetic algorithm (RCGA) which of operators are composed of the reproduction, crossover and mutation is used. Constraints are divided into equalities and inequalities: equality constraints consist of position conditions at the start and end of stride period and repeatability conditions related to each joint angle and angular velocity. Next, inequality constraints include the collision avoidance conditions of swing leg at the face and edge of a stair, the knee joint conditions with respect to the singular avoidance, and the zero moment point condition with respect to the stability into the going direction. Finally, in order to approximate the walking gait, each joint angle trajectory is defined as a 4th order polynomial of which coefficients are chromosomes. In the computer simulation used 6 degree of freedom biped robot model that consists of seven links, we analyze the energy efficiency of proposed optimal trajectories about the following cases: walking on ground, ascending stairs, and descending stairs.

In this paper, we propose a gait transition algorithm between walking and running for fast movement of a biped robot. Firstly, considering that walking and running differ in the oscillations of the body and legs that occur during each step or stride, the transitionary trajectory is constructed by the transformations of the velocities of hip link, the step height and stride of the feet, and the duration of the step using interpolating polynomials. And in order to increase the compliance about the environment and to absorb the impact force in the landing event, the impedance controller is designed for walking and running biped robot. The effectiveness and the performance of the proposed gait patterns are shown in computer simulations with a 19-DOF biped robot and a 6-DOF elastic pad model.

Relationships between impedance parameters and scaling factors are derived using absolute stability and passivity. For this, the teleoperation system is represented as a two-port model with a. hybrid matrix. Design procedure of the impedance parameters for the absolute stability of the teleoperator under the time delay is proposed. The validity of the proposed control scheme is demonstrated by experiments with a 1-dof master/slave system connected through the Internet.

In this paper the authors illustrate the development of a semi-autonomous robot for colonoscopy. In particular they focus on two problems: the generation of an effective and reliable advancement in the colon, and the possibility to steer the robot in order to overcome acute intestinal bends. Both problems are present also during traditional colonoscopy, but they can be solved with an external pushing action produced by the endoscopist. The main feature of this work is the attempt to replicate the effects of external forces (generated by the medical doctors) by using just internal actions (generated by the robotic devices). The robotic solutions and the mechanisms illustrated in this paper could be in principle integrated in an "all inside" device, with electrical wires and service tubes, but without structural cables or rigid tails which are currently used for the advancement and orientation of traditional colonoscopes.

Biped robots are expected to walk on many different and previously unknown terrains, and thus they may walk on a slippery surface with low friction with no information on the surface a priori. Any fall-down due to unexpected slipping could cause costly damage to the robot and thus should be avoided. The paper proposes a reflex control method for biped robots to quickly recover their posture from a slip soon after a detection of the slip. Computer simulations with a 12-DOF biped robot and a 6-DOF environment model that consists of nonlinear dampers, and linear and nonlinear springs, show that the proposed method is very effective in preventing a fall-down of biped robots on a slippery surface.

This paper proposes a control method for biped robot locomotion based on impedance control and impedance modulation. Both legs are controlled by the impedance control, where the desired impedance at the hip and the swing foot are specified. The impedance parameters are changed depending on the gait phase of the biped robot. To reduce the magnitude of impact and to guarantee a stable footing at foot landings on the ground, the damping coefficient of the impedance of the landing foot is increased drastically and the reference trajectory of the landing foot is reset at its initial contact with the ground. A series of computer simulations of a 12-degree-of-freedom (DOF) biped robot with a 6-DOF environment model which consists of nonlinear and linear compliant spring-and-dampers, shows that the proposed control method works well and is superior to position-oriented control methods such as the computed-torque control method in impact regulation during foot landings and adaptation to some ground irregularity.

This paper proposes an online trajectory modification scheme for biped robots to cope with uncertainty of their environment. The trajectory of the base link in the vertical direction is modified depending on the magnitude of zero moment point deviation from its safety boundary such that appropriate angular moment is generated to maintain stable walking. The modified trajectory then gradually returns to the original trajectory using a 3rd- or 5th-order interpolation polynomial. We expand the gravity-compensated inverted pendulum mode to generate the base-link trajectory not only for single support phases but also double support phases. In the simulations to evaluate the proposed scheme, an impedance controller is used to control a 6-DOF biped robot and the environment of the biped robot is assumed to consist of nonlinear and linear compliant contact models. The simulation results show that the proposed online trajectory modification scheme effectively enhances the stability of locomotion.

Robust control is designed for nonlinear uncertain systems, which can be decomposed into two cascaded subsystems, that is, a series connection of two nonlinear subsystems. For such a system, a recursive design is used to include a second subsystem in robust control. The recursive design procedure is constructive and contains two steps. First, a fictitious robust controller for the first subsystem is designed as if the subsystem had an independent control. As the fictitious control, nonlinear H/sub /spl infin// control using the energy dissipation is designed in the sense of L/sub 2/-gain attenuation from the disturbance caused by uncertainties to performance. Second, the actual robust control is designed recursively by Lyapunov's second method. The designed robust control is applied to a robotic system with actuators, in which physical control inputs are not the torque to robot links but electrical signals to actuators.

Proposes an impedance control method with impedance modulation strategy for biped robot locomotion. The constrained leg as well as the free leg is controlled by the impedance control. To reduce the magnitude of an impact with the ground and guarantee a stable footing when a foot contacts with the ground, the paper proposes to increase the damping of the leg drastically and to modify the reference trajectory of the leg. Computer simulations with a 3-DOF environment model with a combination of a nonlinear and linear compliant contact model show that the proposed controller is superior to computed-torque controllers in the impact regulation and stability robustness in locomotion.