Ningbo Yu

Gesture-based telemanipulation of a humanoid robot for home service tasks

Humanoid robots can be of great assistance to accomplish dexterous manipulation tasks for the impaired and elderly people, but diversity of the environments and complexity of autonomous algorithms still keep as challenging obstacles. In this paper, we proposed a gesture-based telemanipulation scheme to control the NAO humanoid robot. Taking advantage of the Leap Motion Controller, an intuitive and straightforward way for human-robot interaction has been realized. The NAO robot is telemanipulated to accomplish locomotion, dexterous manipulation and composite tasks, and validated by various experiments. This provides a promising technique for service robotics to deliver assistance for activities of daily living at home or in caring agencies, which could be of greatly help for the impaired and elderly people in an aging society.

Fusion of Haptic and Gesture Sensors for Rehabilitation of Bimanual Coordination and Dexterous Manipulation.

Disabilities after neural injury, such as stroke, bring tremendous burden to patients, families and society. Besides the conventional constrained-induced training with a paretic arm, bilateral rehabilitation training involves both the ipsilateral and contralateral sides of the neural injury, fitting well with the fact that both arms are needed in common activities of daily living (ADLs), and can promote good functional recovery. In this work, the fusion of a gesture sensor and a haptic sensor with force feedback capabilities has enabled a bilateral rehabilitation training therapy. The Leap Motion gesture sensor detects the motion of the healthy hand, and the omega.7 device can detect and assist the paretic hand, according to the designed cooperative task paradigm, as much as needed, with active force feedback to accomplish the manipulation task. A virtual scenario has been built up, and the motion and force data facilitate instantaneous visual and audio feedback, as well as further analysis of the functional capabilities of the patient. This task-oriented bimanual training paradigm recruits the sensory, motor and cognitive aspects of the patient into one loop, encourages the active involvement of the patients into rehabilitation training, strengthens the cooperation of both the healthy and impaired hands, challenges the dexterous manipulation capability of the paretic hand, suits easy of use at home or centralized institutions and, thus, promises effective potentials for rehabilitation training.

Augmented virtual stiffness rendering of a cable-driven SEA for human-robot interaction

Human-robot interaction U+0028 HRI U+0029 is fundamental for human-centered robotics, and has been attracting intensive research for more than a decade. The series elastic actuator U+0028 SEA U+0029 provides inherent compliance, safety and further benefits for HRI, but the introduced elastic element also brings control difficulties. In this paper, we address the stiffness rendering problem for a cable-driven SEA system, to achieve either low stiffness for good transparency or high stiffness bigger than the physical spring constant, and to assess the rendering accuracy with quantified metrics. By taking a velocity-sourced model of the motor, a cascaded velocity-torque-impedance control structure is established. To achieve high fidelity torque control, the 2-DOF U+0028 degree of freedom U+0029 stabilizing control method together with a compensator has been used to handle the competing requirements on tracking performance, noise and disturbance rejection, and energy optimization in the cable-driven SEA system. The conventional passivity requirement for HRI usually leads to a conservative design of the impedance controller, and the rendered stiffness cannot go higher than the physical spring constant. By adding a phase-lead compensator into the impedance controller, the stiffness rendering capability was augmented with guaranteed relaxed passivity. Extensive simulations and experiments have been performed, and the virtual stiffness has been rendered in the extended range of 0.1 to 2.0 times of the physical spring constant with guaranteed relaxed passivity for physical humanrobot interaction below 5 Hz. Quantified metrics also verified good rendering accuracy.

A bilateral rehabilitation method for arm coordination and manipulation function with gesture and haptic interfaces

Disabilities after neural injury such as stroke bring tremendous burden to the patients, families and society. Besides the conventional constrained-induced training with the paretic arm, bilateral rehabilitation training involves both the ipsilateral and contralateral sides of the neural injury, fits well the fact that both arms are needed in common activities of daily living (ADLs), and can promote good functional recovery. In this work, a bilateral rehabilitation training method is proposed and implemented with the Leap Motion sensor and omega.7 haptic interface. The Leap Motion sensor detects the motion of the healthy hand, and the omega.7 device, according to the cooperative task paradigm, assists the paretic hand as much as needed with active force feedback to accomplish the manipulation task. A virtual scenario has been built up, and the motion and force data enables visual and audio feedback in real time as well as further analysis of the functional capabilities of the patient. This task-oriented bimanual training paradigm encourages active involvement of the patients into rehabilitation, strengthens cooperation of both the healthy and impaired hands, challenges the dexterous manipulation capability of the paretic hand, suits easy home use, and thus, promises effective rehabilitation therapy.

Design and analysis of a wrist-hand manipulator for rehabilitation of upper limb dexterous function

Dexterous distal arm functions are crucial for execution of activities of daily living (ADLs). However, it remains difficult for patients with neurological deficits, such as stroke, to recover the lost manipulation capabilities. In this paper, a modular approach has been proposed to design a wrist-hand manipulator to be employed in the rehabilitation training of the upper limb dexterous function. Consisting of the installation module, the forearm module, the in-parallel wrist module, and the hand module, the end-effector based manipulator encourages the patient to voluntary coordinate motion of individual joints of the upper limb. Further, it is compact, stiff, and can be easily installed on desk, wall or other systems. Various hand modules can be attached on the manipulator for patients of different paretic levels. Parameter optimization has been performed for the in-parallel wrist module about workspace capability and manipulability. Condition number over the entire workspace is taken as the manipulability measure. Finally, the design and optimization parameters are validated by kinematic simulation with MATLAB/Simulink SimMechanics toolbox.

Active mass-offloading with cable-driven SEA for tailored support to lower limb rehabilitation

Walk training with body weight support (BWS) can motivate mild and moderate patients after neural injury to actively control their gait and balance, and thus leads to intensive participation and promises effective recovery of the patients. We are building an active BWS system that allows patients to move in the three dimensional Cartesian space and provides well-controlled supportive force against gravity. Nevertheless, the dynamic load can still be challenging for the patients. In this work, a mass-offloading method has been designed with respect to the cable-driven series elastic actuator (SEA) in the BWS system to virtually remove partial body mass. The acceleration signal of the subject is measured and fed back into the mass-offloading controller, which determines the required dynamic force from the actuator. Then, a nonlinear sliding mode controller regulates the force output of the cable-driven series elastic actuator. Thus, tailored body weight support and mass-offloading are provided to assist the subject with voluntary walking and balance control. Simulation experiments have validated the feasibility and efficacy of the mass-offloading method for the BWS system.

Impedance control of a cable-driven series elastic actuator with the 2-DOF control structure

Series elastic actuators (SEAs) are growingly important in physical human-robot interaction (HRI) due to their inherent safety and compliance. Cable-driven SEAs also allow flexible installation and remote torque transmission, etc. However, there are still challenges for the impedance control of cable-driven SEAs, such as the reduced bandwidth caused by the elastic component, and the performance balance between reference tracking and robustness. In this paper, a velocity sourced cable-driven SEA has been set up. Then, a stabilizing 2 degrees of freedom (2-DOF) control approach was designed to separately pursue the goals of robustness and torque tracking. Further, the impedance control structure for human-robot interaction was designed and implemented with a torque compensator. Both simulation and practical experiments have validated the efficacy of the 2-DOF method for the control of cable-driven SEAs.

A haptic shared control algorithm for flexible human assistance to semi-autonomous robots

Autonomous as well as teleoperated robots find wide applications in various environments. Their capability to accomplish complex and dynamic operations can be significantly improved by fusing human intelligence with autonomous algorithms. In this paper, we propose a haptic shared control algorithm to provide flexible human assistance for semi-autonomous mobile robots. Through the admittance and impedance models, the haptic shared controller smoothly puts together human operator inputs with robot autonomy. Further, the level of autonomy is fully determined by the operator with the grasp motion. A decomposed design has been taken for the autonomous controller of the mobile robot. The algorithm was implemented on the haptic interface omega.7 together with a QBot mobile robot, and its feasibility and efficacy have been validated by experiments.

A haptic shared control approach to teleoperation of mobile robots

In robot teleoperation, the fusion of human manual control and robot autonomy can greatly improve its ability to accomplish dynamic and complex operations and tasks. In this paper, an innovative haptic shared controller has been proposed for teleoperation of mobile robots. The robot autonomy and human intervention are both taken into account, and further, passivity from human operation to robot motion is guaranteed by the design of the impedance and admittance models. The control algorithm has been implemented on a versatile haptic interface omega.7, taking advantage of its force feedback capability that allows composite realization of impedance as well as admittance models, and the QBot mobile robot. Teleoperation experiments with omega.7 and the QBot robot has validated the algorithm.

Passivity guaranteed stiffness control with multiple frequency band specifications for a cable-driven series elastic actuator

Abstract Impedance control and specifically stiffness control are widely applied for physical human-robot interaction. The series elastic actuator (SEA) provides inherent compliance, safety and further benefits. This paper aims to improve the stiffness control performance of a cable-driven SEA. Existing impedance controllers were designed within the full frequency domain, though human-robot interaction commonly falls in the low frequency range. We enhance the stiffness rendering performance under formulated constrains of passivity, actuator limitation, disturbance attenuation, noise rejection at their specific frequency ranges. Firstly, we reformulate this multiple frequency-band optimization problem into the H ∞ synthesis framework. Then, the performance goals are quantitatively characterized by respective restricted frequency-domain specifications as norm bounds. Further, a structured controller is directly synthesized to satisfy all the competing performance requirements. Both simulation and experimental results showed that the produced controller enabled good interaction performance for each desired stiffness varying from 0 to 1 times of the physical spring constant. Compared with the passivity-based PID method, the proposed H ∞ synthesis method achieved more accurate and robust stiffness control performance with guaranteed passivity.