A Tele-Operated Display With a Predictive Display Algorithm

Tele-operated display systems with head mounted displays (HMD) are becoming popular as visual feedback systems for tele-operation systems. However, the users are suffered from time-varying bidirectional delays caused by the latency and limited bandwidth of wireless communication networks. Here, we develop a tele-operated display system and a predictive display algorithm allowing comfortable use of HMDs by operators of tele-operation systems. Inspired by the kinematic model of the human head-neck complex, we built a robot neck-camera system to capture the field of view in any desired orientation. To reduce the negative effects of the time-varying bidirectional communication delay and operation delay of the robot neck, we developed a predictive display algorithm based on a kinematic model of the human/robot neck-camera system, and a geometrical model of a camera. Experimental results showed that the system provide predicted images with high frame rate to the user

A Wearable Control Interface for Tele-operated Robots

Department of Mehcanical EngineeringThis thesis presents a wearable control interface for the intuitive control of tele-operated robots, which aim to overcome the limitations of conventional uni-directional control interfaces. The control interface is composed of a haptic control interface and a tele-operated display system. The haptic control interface can measure user???s motion while providing force feedback. Thus, the user can control a tele-operated robot arm by moving his/her arm in desired configurations while feeling the interaction forces between the robot and the environment. Immersive visual feedback is provided to the user with the tele-operated display system and a predictive display algorithm. An exoskeleton structure was designed as a candidate of the control interface structure considering the workspace and anatomy of the human arm to ensure natural movement. The translational motion of human shoulder joint and the singularity problem of exoskeleton structures were addressed by the tilted and vertically translating shoulder joint. The proposed design was analyzed using forward and inverse kinematics methods. Because the shoulder elevation affects all of the joint angles, the angles were calculated by applying an inverse kinematics method in an iterative manner. The proposed design was tested in experiments with a kinematic prototype. Two force-controllable cable-driven actuation mechanisms were developed for the actuation of haptic control interfaces. The mechanisms were designed to have lightweight and compact structures for high haptic transparency. One mechanism is an asymmetric cable-driven mechanism that can simplify the cable routing structure by replacing a tendon to a linear spring, which act as an antagonistic force source to the other tendon. High performance force control was achieved by a rotary series elastic mechanism and a robust controller, which combine a proportional and differential (PD) controller optimized by a linear quadratic (LQ) method with a disturbance observer (DOB) and a zero phase error tracking (ZPET) feedforward filter. The other actuation mechanism is a series elastic tendon-sheath actuation mechanism. Unlike previously developed tendon-sheath actuation systems, the proposed mechanism can deliver desired force even in multi-DOF systems by modeling and feedforwardly compensating the friction. The pretension change, which can be a significant threat in the safety of tendon-sheath actuation systems, is reduced by adopting series elastic elements on the motor side. Prototypes of the haptic control interfaces were developed with the proposed actuation mechanisms, and tested in the interaction with a virtual environment or a tele-operation experiment. Also, a visual feedback system is developed adopting a head mounted display (HMD) to the control interface. Inspired by a kinematic model of a human head-neck complex, a robot neck-camera system was built to capture the field of view in a desired orientation. To reduce the sickness caused by the time-varying bidirectional communication delay and operation delay of the robot neck, a predictive display algorithm was developed based on the kinematic model of the human and robot neck-camera system, and the geometrical model of a camera. The performance of the developed system was tested by experiments with intentional delays.clos

Dynamic Mobile Manipulation via Whole-Body Bilateral Teleoperation of a Wheeled Humanoid

Humanoid robots have the potential to help human workers by realizing physically demanding manipulation tasks such as moving large boxes within warehouses. We define such tasks as Dynamic Mobile Manipulation (DMM). This paper presents a framework for DMM via whole-body teleoperation, built upon three key contributions: Firstly, a teleoperation framework employing a Human Machine Interface (HMI) and a bi-wheeled humanoid, SATYRR, is proposed. Secondly, the study introduces a dynamic locomotion mapping, utilizing human-robot reduced order models, and a kinematic retargeting strategy for manipulation tasks. Additionally, the paper discusses the role of whole-body haptic feedback for wheeled humanoid control. Finally, the system's effectiveness and mappings for DMM are validated through locomanipulation experiments and heavy box pushing tasks. Here we show two forms of DMM: grasping a target moving at an average speed of 0.4 m/s, and pushing boxes weighing up to 105\% of the robot's weight. By simultaneously adjusting their pitch and using their arms, the pilot adjusts the robot pose to apply larger contact forces and move a heavy box at a constant velocity of 0.2 m/s

Torque control of a double tendon-sheath actuation mechanism in varying sheath configuration

Tendon-sheath actuation mechanism has been researched due to its extremely simple and light cable routing structure. However, the slide-based force transmission mechanism causes friction, which disturbs precise force control. To overcome such disadvantage, friction compensation algorithms in tendon-sheath actuation systems have been studied. However, the torque control of double tendon-sheath mechanism has not been achieved yet without a torque feedback. In this research, a double-tendon sheath actuation mechanism with series elastic elements and tight sheath routing method is introduced to achieve feedforward torque control. The performance of proposed mechanism is verified with experiments

Kinematic analysis of a 5 DOF upper-limb exoskeleton with a tilted and vertically translating shoulder joint

In this paper, an upper-limb exoskeleton with a tilted and vertically movable shoulder joint is proposed. By analyzing the biomechanics of the shoulder, the motion of the upper limb is approximated by including one degree of freedom (DOF), namely vertical translation of the glenohumeral joint, in addition to the three DOFs that are conventionally employed to analyze the motion of the shoulder. Also, the shoulder joint is tilted to avoid singularity problems in the workspace; by tilting the shoulder joint, the singularity position was placed outside of the normal range of motion. This configuration was analyzed using forward and inverse kinematics methods. Because the shoulder elevation affects all the joint angles, the angles were calculated by applying an inverse kinematics method in an iterative manner. The performance of the proposed upper-limb exoskeleton and analysis methods have been verified by simulations

Torque Control of a Series Elastic Tendon-sheath Actuation Mechanism

Tendon-sheath actuation mechanisms can provide compact and lightweight tendon routing. However, torque control of a tendon-sheath actuation system is challenging because of variable friction with respect to the sheath configuration. Model-based feedforward friction compensation algorithms have been developed to accurately deliver desired torque, but it is difficult to apply such algorithms to multi-degrees of freedom (DOFs) systems because of changes in sheath configurations that in turn alter the base tension and friction parameters. In this article, we develop a series elastic tendon-sheath actuation mechanism that allows feedforward torque control in multi-DOFs systems. The mechanism features series elastic elements on the motor side to reduce base tension changes and enable accurate input torque control. Friction is compensated by a feedforward controller with a modeled friction parameter to transmit desired torque to the distal joint under varying sheath configurations. The performance of the proposed series elastic tendon-sheath actuation mechanism is demonstrated in experiments using a control interface for a tele-operation system

Kinematic Analysis of a 5-DOF Upper-Limb Exoskeleton With a Tilted and Vertically Translating Shoulder Joint

In this paper, an upper-limb exoskeleton with a tilted and vertically movable shoulder joint is proposed. By analyzing the biomechanics of the shoulder, the upper limb for the shoulder and the elbow was approximated to five degrees of freedom (DOFs) by including the vertical translation of the glenohumeral joint of the shoulder, in addition to the 3 DOFs of the shoulder and 1 DOF of the elbow, which are conventionally used to analyze the motion of the shoulder. The shoulder joint was tilted to avoid singularity problems in the workspace, i.e., by tilting the shoulder joint, the singularity position was placed outside of the normal range of motion. This configuration was analyzed using forward and inverse kinematics methods. Because the shoulder elevation affects all of the joint angles, the angles were calculated by applying an inverse kinematics method in an iterative manner. The performance of the proposed upper-limb exoskeleton and analysis methods was verified by simulations and experimentsclose0

Simulation analysis on friction compensation of a double tendon-sheath actuation system

Tele-operation systems have been developed to perform tasks in extreme environments which cannot be easily accessed by human. However, non-intuitive control interfaces using only a keyboard or a joystick and wireless communication issues have prohibited the wide application of the tele-operation systems. In this work, an intuitive operation interface using inertial measurement units (IMUs) and a haptic glove was proposed to control a six degrees of freedom (DOFs) robot arm in remote place. Using the measured joint angles by the IMUs, the wrist position of the human arm was obtained by forward kinematics, which was used to calculate the robot joint angles by inverse kinematics. Considering workspace of the robot and human arms, robot joint angles were selected from many feasible solutions by the inverse kinematics. Also, the robot hand was controlled by the measured finger joint angles from the haptic glove, which also delivered vibration to the fingers according to the grasp force of the robot hand. As a tele-communication method, the 3GPP (3rd Generation Partnership Project) Long Term Evolution (LTE) network and a virtual private network (VPN) were utilized. The performance of the proposed system was verified by experiments

Performance verification of a kinematic prototype 5-DOF upper-limb exoskeleton with a tilted and vertically translating shoulder joint

In this paper, the performance of the 5-DOF upper-limb exoskeleton with a tilted and vertically translating shoulder joint, which was proposed in our previous work, is verified by simulations and experiments. In this design, one vertical prismatic joint was added for the vertical translation of the shoulder, and the shoulder joint was tilted to avoid the singularity problem. Based on the kinematic analysis in our previous work, the manipulability analysis was performed to determine the tilting angles and to check whether the singularity problem was appropriately addressed by the proposed design. The natural motion enabled by the added vertical translation was experimentally verified. For the experiments, an unactuated prototype of the proposed exoskeleton system was designed and manufactured. The experiment was focused on the decrease of the load on user's shoulder with a vertically translating shoulder joint. The three axis forces at the shoulder joint were compared with those of conventional upper-limb exoskeleton whose shoulder joint was fixed. The simulation and experimental results show that the proposed upper-limb exoskeleton design is suitable for supporting natural motions of the upper-limb