Active DOF Research Articles

A Multi-Configuration Track-Legged Humanoid Robot for Dexterous Manipulation and High Mobility: Design and Development

Various applications (e.g., disaster response) put forward higher requirements for the capabilities of robots. However, to date, few platforms can be compatible with the required mobility, stability and dexterity. A major challenge is mobile stability may severely limit the variety of manipulation skills. To tackle the issue, this paper presents a new track-legged humanoid robot, Dexbot, aiming to achieve both dexterity and mobility simultaneously. Dexbot is composed of a versatile humanoid upper body and a track-legged mobile platform, with a total of 56 active DOFs and about 10 transformable configurations, allowing for precise manipulation and traversal of various complex environments. Additionally, it features a lightweight and highly integrated design, with notable dexterity, strength and mobility in its class. Herein, this paper reports a brief overview of each subsystem, focusing on the robotic structure, system architecture, and some applied strategies of capabilities development. Finally, some essential performances are demonstrated through a series of experiments.

A Fast Frequency Sweep approach for performance-based optimization of earthquake-resistant irregular large-scale buildings

Performance-Based Design (PBD) optimization of buildings subjected to seismic excitations has increasingly been applied to regular small-scale structural systems to minimize initial or life-cycle costs. Nonetheless, a comprehensive bibliographic survey reveals that studies dealing with irregular buildings are scarce, although they can present higher seismic vulnerability than regular buildings. Specifically, the PBD optimization of irregular buildings represented by large-scale finite element (FE) models, and considering dozens of discrete design variables, cannot be found to the best of the authors’ knowledge. Hence, this paper presents an original framework for the PBD optimization of irregular buildings subjected to seismic excitations, handling thousands of DOFs and dozens of discrete design variables. To relieve the computational burden, enabling the problem to be solved, a Model Order Reduction (MOR) strategy based on the Well-Conditioned Asymptotic Waveform Evaluation (WCAWE) approach is combined with a hybrid optimization algorithm, which integrates a local optimizer with a restart strategy. The former is employed to speed up the frequency-domain response, while the latter allows for tackling a non-convex and multimodal objective function with many discrete variables. The procedure is adaptatively devised to operate in a robust and fully black-box approach. The application case consists of a stiffness in-plane irregular H-shape building with 16,452 active DOFs and 34 discrete design variables. The proposed scheme largely reduces the computational burden, leading to speed-up factors (SUF) up to 19 times compared to direct frequency-domain solutions.

Synergy Estimation Method for Simultaneous Activation of Multiple DOFs Using Surface EMG Signals

Surface electromyography signals are routinely used for designing prosthetic control systems. The concept of synergy estimation for muscle control interpretation is being explored extensively. Synergies estimated for a single active degree of freedom (DoF) are found to be uncorrelated and provide better results when used for single movement classification; however, an increase of simultaneously active DoFs leads to complex limb movements and multiple DoF detection becomes a challenge. Synergy estimation is a non-convex optimization technique, to provide better estimation this paper proposes the use of regularized non-negative matrix factorization for the evaluation of synergistic weights in complex movements. The use of regularization constraint makes the overall problem bounded and provide smoothness. The proposed technique showed better accuracy when tested for activation of multiple DoF simultaneously at a significantly lower computational time, i.e., by 34%.

On-Line Learning for Planning and Control of Underactuated Robots With Uncertain Dynamics

We present an iterative approach for planning and controlling motions of underactuated robots with uncertain dynamics. At its core, there is a learning process which estimates the perturbations induced by the model uncertainty on the active and passive degrees of freedom. The generic iteration of the algorithm makes use of the learned data in both the planning phase, which is based on optimization, and the control phase, where partial feedback linearization of the active dofs is performed on the model updated on-line. The performance of the proposed approach is shown by comparative simulations and experiments on a Pendubot executing various types of swing-up maneuvers. Very few iterations are typically needed to generate dynamically feasible trajectories and the tracking control that guarantees their accurate execution, even in the presence of large model uncertainties.

Real Time Estimator to Perform Targeted Biopsies With a Free-Wrist Robot Despite Large Deformations of the Insertion Orifice.

In the context of keyhole surgery, and more particularly of uterine biopsy, the fine automatic movements of a surgical instrument held by a robot with 3 active DOF’s require an exact knowledge of the point of rotation of the instrument. However, this center of rotation is not fixed and moves during an examination. This paper deals with a new method of detecting and updating the interaction matrix linking the movements of the robot with the surgical instrument. This is based on the method of updating the Jacobian matrix which is named the “Broyden method”. It is able to take into account body tissue deformations in real time in order to improve the pointing task for automatic movements of a surgical instrument in an unknown environment.

A Padé-based fast frequency sweep approach for irregular large-scale building models subjected to seismic excitation

Buildings with vertical or in-plane irregularities are often required for architectural purposes. From the seismic behavior perspective, such conditions usually demand a complete dynamic analysis instead of applying static equivalent lateral forces. Furthermore, a refined building’s finite element model (FEM) can also be needed, leading to time-expensive computational solutions in the time domain. Despite cheaper, solving the system matrices repetitively over a broad frequency range in the frequency domain is an issue for large-scale systems too. Thus, this paper presents an efficient scheme, based on model order reduction (MOR), for computing frequency sweeps with fine increments of irregular buildings described by the FEM. In opposite to the standard Krylov-related MOR and SVD-based techniques, the Pade-based procedure employed herein can tackle any form of frequency dependency, as long as the high-order derivatives are obtained. For illustration purposes, a stiffness in-plane irregular H-shape building with 16452 active DOFs is solved using the MOR scheme for controlled and uncontrolled scenarios. Speed-up factors (SUF) up to 25 times can be reached for both cases when compared to direct frequency-domain solutions.

Influence of Compliant Joints in Four-Legged Robots

Legged animals are capable of rapid movements, are efficient from the energy point of view and are able to adapt gaits to environmental conditions. Motions like walking, trotting, galloping and jumping, are difficult to evaluate and replicate due to their being consequence of tricky interaction of different systems (like the musculoskeletal system and the central and peripheral nervous systems, including also the influence of the environment). In this paper, we analyzed the behaviour of a four-legged robot constituted by 1 active DOF in each leg (using commercial servomotors) and 1 passive DOF in each knee and in spine (using springs). Our objective is to increase the motion performances of the robot varying the stiffness of the springs. The results obtained from the simulation underline how the stiffness of the spine influences the performance of the robot by increasing the speed and reducing the energy requested by the servomotors.

Design and control of a wearable lower-body exoskeleton for squatting and walking assistance in manual handling works

Several manual-handling works (e.g. load-lifting, carrying, carpet-laying, etc.) involve repetitive lower limb movements (RLLM) such as squatting, kneeling, or walking which are notable risk factors for work-related musculoskeletal disorders of the lower-limb and lumbar spine. Wearable exoskeletons can augment workers’ strength and minimize muscular activation in RLLM, thus enhancing efficiency and improving workers health. In this paper, we present the design and control of a wearable lower-body exoskeleton to assist RLLM. The design of the exoskeleton is anthropomorphic with six-degrees of freedom (6-DoF) on each leg: 1-active and 1-passive DoF on the hip-joint, 1-active and 1-passive DoF on the knee-joint, and 2-passive DoFs on the ankle-joint. The active DoFs are actuated by bi-directional brushless DC motors to permit sagittal movements. The exoskeleton controller is designed hierarchical with a low-level linear quadratic gaussian (LQG) torque controller, a middle-level user-input torque estimator based on dual extended Kalman filter (EKF), and a novel high-level supervisory algorithm for movement detection and synchronization of the exoskeleton with the user. Initial evaluation of the prototype is conducted on five healthy participants recruited to perform repetitive load-lifting and carrying manual-handling tasks. Electromyogram sensors are placed at the participants’ right Vastus Intermedius and right Gastrocnemius to extract muscle activity signals. Results show that the exoskeleton could provide torque assistance by amplifying participants’ input joint torques and could minimize muscular activation in the two muscles by more than 36% respectively in all movement tasks.

Kinematic Analysis of a Novel Couple-Adaptive Underactuated Finger Mechanism

This paper presents the design of finger mechanism with one active DOF that combines underactuation mechanism and spring elements. The three phalanges of human finger can not only rotate simultaneously with a certain ratio before touching the grasped object, but can also envelop the object successively even if some of them are blocked, called the Couple-Adaptive feature. To realize this function in the finger mechanism, a novel underactuated four-bar mechanism is proposed in this paper. The kinematics model has been derived based on a vector analysis. The simulations of kinematic analysis show that this underactuated finger mechanism has anthropomorphic motion and grasping feature. And its workspace indicates that this prosthetic finger could complete most of grasping tasks.

Mechanical Bed for Investigating Sleep-Inducing Vibration.

In running cars or trains, passengers often feel sleepy. Our study focuses on this physiological phenomenon. If a machine can reproduce this phenomenon, it is feasible to put a person, such as an insomnia patient or an infant, to sleep without any harmful effects. The results of our previous study suggest that low-frequency vibration induces sleep. This report describes a new mechanical bed for inducing sleep and discusses the effects of different vibration conditions. The new bed has two active DOFs in the vertical and horizontal directions to examine the anisotropy of sensation. The bed includes three main parts: a vertical driver unit, a horizontal driver unit, and a unique 2-DOF counterweight system to reduce driving force and noise. With regard to motion accuracy, the maximum motion error in the vertical direction lifting 75 kg load was only 0.06 mm with a 5.0 mm amplitude of a 0.5 Hz sinusoidal wave. The results of excitation experiments with 10 subjects showed a significant difference in sleep latency between the conditions with vibration and without vibration. Furthermore, the average latency with insensible vibration (amplitude = 2.4 mm) was shorter than that with sensible vibration (amplitude = 7.5 mm). These results suggest the ability of appropriate vibration to induce sleep.

Functional Design of a Powered Elbow Orthosis Toward its Clinical Employment

This paper presents the design and preliminary evaluation of a novel version of the robotic elbow exoskeleton NEUROExos, designed for the in-clinic treatment of stroke survivors in acute and subacute phases. The robotic design implements a novel series elastic actuation system, a 4-degree-of-freedom (DoFs) passive mechanism for the anatomical axis alignment, and one active DoF with remote cable-driven actuation. The low-level control system allows two working modalities: a torque control and a joint position control. The high-level control system employs a finite-state machine that allows the setting and execution of these modalities during rehabilitation exercises. Preliminary pilot tests based on passive exercises, with three chronic post-stroke patients, demonstrated the effectiveness of the proposed approach in assessing joint rigidity and its usability within a rehabilitation clinic.

Effects of head and tail as swinging appendages on the dynamic walking performance of a quadruped robot

SUMMARYWe designed a quadruped robot with a one-degree-of-freedom (1-DOF)-pitch head, a 1-DOF-roll tail, and 14 active DOFs in total, which are controlled via a central pattern generator (CPG) based on a Hopf oscillator. Head and tail movements are coupled to the leg movements with fixed phase differences. Experiments show that tail swinging in roll can equilibrate feet–ground reaction forces (GRF), reducing yaw errors and enabling the robot to maintain its direction when trotting. Head swing in pitch has the potential to increase flight time and stride length of the swinging legs and increase the robot's forward velocity when running in bounds.

水力学的骨格を利用した繊毛アクチュエータ駆動型柔軟移動ロボット

This study proposes a new flexible mobile robot which is driven by ciliary actuator using fluid power. The proposed robot is capable of adaptive body shape change according to terrains. Moreover, the terrain will not be damaged because the ciliary actuators are flexible. This paper describes the components and performance of the proposed robot. The robot body has active DOFs of body width and direction. The prototype robot successfully climbed a vertical composite pipe which combines 160 mm and 200 mm in diameter. This robot also performed wireless climbing of a vertical pipe.

Smartphone supported upper limb prosthesis

Abstract State of the art upper limb prostheses offer up to six active DoFs (degrees of freedom) and are controlled using different grip patterns. This low number of DoFs combined with a machine-human-interface which does not provide control over all DoFs separately result in a lack of usability for the patient. The aim of this novel upper limb prosthesis is both offering simplified control possibilities for changing grip patterns depending on the patients’ priorities and the improvement of grasp capability. Design development followed the design process requirements given by the European Medical Device Directive 93/42 ECC and was structured into the topics mechanics, software and drive technology. First user needs were identified by literature research and by patient feedback. Consequently, concepts were evaluated against technical and usability requirements. A first evaluation prototype with one active DoF per finger was manufactured. In a second step a test setup with two active DoF per finger was designed. The prototype is connected to an Android based smartphone application. Two main grip patterns can be preselected in the software application and afterwards changed and used by the EMG signal. Three different control algorithms can be selected: “all-day”, “fine” and “tired muscle”. Further parameters can be adjusted to customize the prosthesis to the patients’ needs. First patient feedback certified the prosthesis an improved level of handling compared to the existing devices. Using the two DoF test setup, the possibilities of finger control with a neural network are evaluated at the moment. In a first user feedback test, the smartphone based software application increased the device usability, e.g. the change within preselected grip patterns and the “tired muscle” algorithm. Although the overall software application was positively rated, the handling of the prosthesis itself needs to be proven within a patient study to be performed next. The capability of the neural network to control the hand has also to be proven in a next step.

Herbert: Design and Realization of a Full-Sized Anthropometrically Correct Humanoid Robot

In this paper we present the development of a new full-sized anthropometrically correct humanoid robot Herbert. Herbert has 33 DOFs: 1) 29 active DOFs (2 × 4 in the legs, 2 × 7 in the arms, 4 in the waist and 3 in the head); 2) 4 passive DOFs (2 × 2 in the ankles). We present the objectives of the design and the development of our system, the hardware (mechanical, electronics) as well as the supporting software architecture that encompasses the realisation of the complete humanoid system. Several key elements, that have to be taken into account in our approach to keep the costs low while ensuring high-performance, will be presented. In realising Herbert we applied a modular design for the overall mechanical structure. Two core mechanical module types make up the main structural elements of Herbert: 1) small compact mechanical drive modules; and 2) compliant mechanical drive modules. The electronic system of Herbert, which is based on two different types of motor control boards and an FPGA module with a central controller, is discussed. The software architecture is based on ROS with a number of sub nodes used for the controller. All these supporting components have been important in the development of the complete system. Finally, we present results showing our robot’s performances: demonstrating the behaviour of the compliant modules, the ability of tracking a desired position/velocity as well as a simple torque controller. We also evaluate our custom communication system. Additionally, we demonstrate Herbert balancing and squatting to show its performance. Moreover, we also show the simplicity of the higher level supporting software framework in realising new behaviours. All in all, we show that our system is compact and able to achieve comparable human performances and has human proportions while being low cost.

1A1-U02 部分スライドローラを用いた横移動も可能なローラコンベアの開発(生産システム・生産機器メカトロニクス)

Conveyers are widely used in transportation and manufacturing fields. In case that a conveyed object requires changing its traveling direction, conventional systems used moving flippers, jack-up sliders, etc. Other systems using omnidirectional wheels or rollers with other actuators are also proposed. In contrast, a method using special roller mechanism is proposed in this paper. The mechanism called Partially Sliding Roller (PSR) has one active (or passive) rolling DOF and one semi-passive sliding DOF along rolling axis. Several PSRs can not only transport object but also shift actively to rolling axis direction with the passive DOF. The idea of PSR followed by models of proposed conveyer mechanism and brief experiments to evaluate the method are described.

Achieving Jumping Functions of a Bipedal Robot with Knee and Toe Spring Mechanisms

This paper proposes a model for characterizing the jumping motion of a bipedal robot with knee and toe spring mechanisms. The bipedal robot has seven active DoFs for its body and legs, and two passive DoFs for its toes. The mathematical model of the robot is based on the ZMP (zero moment point) method and Newton's laws of motion to obtain the trajectory of the center of mass, the velocity of the center of mass and the flight height. The results show that the knee and toe spring mechanisms play important roles for the jumping motion. The calculated ZMP trajectory before take-off agrees with the experimental observations. In addition, the predicted flight height with the proposed model is about 8% in error compared with the measured value. That is, the models developed are in close agreement with the experimental results and are useful for analyzing the characteristics of the jumping robot.

The Effect of Anterior-Posterior Shear on the Wear of CHARITÉ Total Disc Replacement

An in vitro study of the wear rates of the CHARITÉ lumbar total disc replacement (TDR). To investigate the effect of anterior-posterior shear on the in vitro wear rates of the CHARITÉ lumbar TDR. Current standards prescribe only 4-degrees of freedom (DOF) inputs for evaluating the in vitro wear of TDRs, despite the functional spinal unit incorporating 6 DOF. Anterior-posterior shear has been highlighted as a significant load, particularly in the lumbar spine. A previous study investigated the effect of an anterior-posterior shear on the ProDisc-L, finding that wear rates were not significantly different from 4-DOF wear tests. Six CHARITÉ lumbar discs were mounted in a 5 active DOF spine wear simulator and tested under 4-DOF (ISO18192) conditions. Six further CHARITÉ lumbar discs were tested under 5-DOF conditions, consisting of 4-DOF conditions plus an anterior-posterior shear displacement of +2/-1.5 mm. The displacement was decreased and then increased by a factor of 2 to investigate the effect of the magnitude of displacement. Micro-computed tomographic scans of the discs were taken before and after wear testing, and the height loss of the discs was calculated. These were compared with the same measurements taken from explanted CHARITÉ discs, micro-computed tomography scanned at another institution. Wear rates for 4 DOF (12.2 ± 1.0 mg/MC) were not significantly different from 4-DOF tests on the ProDisc-L. Wear rates were significantly increased (P < 0.01) for "standard" 5-DOF conditions (22.3 ± 2.0 mg/MC), decreased 5 DOF (24.3 ± 4.9 mg/MC), and increased 5 DOF (29.1 ± 7.6 mg/MC). The height loss of the explants and in vitro tested discs were not significantly different (P > 0.05). The addition of anterior-posterior shear to wear testing inputs of the CHARITÉ lumbar TDR increases the wear rate significantly, which is in direct contrast to the previous 5-DOF testing on the ProDisc. This study highlights the importance of clinically relevant testing regimens, and that test inputs may be different for dissimilar design philosophies.

Design of a Hand Exoskeleton Rehabilitation Device

As stroke is one of the most morbidity disease, some rehabilitation devices has been developed to solve the problem, but there isn’t maturation in hand. This paper presents a new hand exoskeleton rehabilitation device to improve the result of rehabilitation and help doctors to perfect theory about hand rehabilitation. We set 8 DOF in this three fingers device, with 2 active DOF and 1 coupled DOF in index or middle finger, 1 active DOF and 1 passive DOF in thumb. The 5 active DOF is driven by motors. The transmission consists of screw nut and multi-link mechanism. We control the device through a typical secondary control system. As this device is designed to help patients not only regain the range of flexion/extension but also complete some typical simple grasping movements. To substantiate the feasibility, an experiment has been carried out. Finally, Suggestions for improvement are given.

Design of a Gravity-Balanced General Spatial Serial-Type Manipulator

A novel methodology for the design of a gravity-balanced serial-type spatial manipulator is presented. In the design, gravity effects of the system can be completely compensated at any configuration. The gravity balance of the n-DOF manipulator is achieved by the suspensions of only n zero-free-length springs, where each spring is individually fitted between a primary link and its adjacent auxiliary link. No spring has to be installed across the spatial manipulator from a far remote link to ground such that the motion interference among the springs and the links can be prevented. Besides, since the embedded auxiliary links along the primary links of the manipulator form a series of spatial parallelogram revolute-spherical-spherical-revolute modules, the active DOFs of the system remain the same as the primary manipulator and the range of motion of the manipulator will not be hindered. As a result, the n-DOF manipulator can serve the general function of an articulated serial-type manipulator in kinematics. The simulated results of a 6DOF gravity-balanced manipulator modeled on ADAMS shows that the static equilibrium as well as the kinematics of the system can be successfully accomplished by this proposed methodology.