Passive DOF Research Articles

Hand Exoskeleton Design and Human-Machine Interaction Strategies for Rehabilitation.

Stroke and related complications such as hemiplegia and disability create huge burdens for human society in the 21st century, which leads to a great need for rehabilitation and daily life assistance. To address this issue, continuous efforts are devoted in human-machine interaction (HMI) technology, which aims to capture and recognize users' intentions and fulfil their needs via physical response. Based on the physiological structure of the human hand, a dimension-adjustable linkage-driven hand exoskeleton with 10 active degrees of freedom (DoFs) and 3 passive DoFs is proposed in this study, which grants high-level synergy with the human hand. Considering the weight of the adopted linkage design, the hand exoskeleton can be mounted on the existing up-limb exoskeleton system, which greatly diminishes the burden for users. Three rehabilitation/daily life assistance modes are developed (namely, robot-in-charge, therapist-in-charge, and patient-in-charge modes) to meet specific personal needs. To realize HMI, a thin-film force sensor matrix and Inertial Measurement Units (IMUs) are installed in both the hand exoskeleton and the corresponding controller. Outstanding sensor-machine synergy is confirmed by trigger rate evaluation, Kernel Density Estimation (KDE), and a confusion matrix. To recognize user intention, a genetic algorithm (GA) is applied to search for the optimal hyperparameters of a 1D Convolutional Neural Network (CNN), and the average intention-recognition accuracy for the eight actions/gestures examined reaches 97.1% (based on K-fold cross-validation). The hand exoskeleton system provides the possibility for people with limited exercise ability to conduct self-rehabilitation and complex daily activities.

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 an ergonomic robotic shoulder for wearable exoskeleton robot for rehabilitation

In this paper, we present an ergonomic robotic shoulder for upper limb exoskeleton. Most exoskeletons have been designed considering shoulder joint instantaneous center of rotation (ICR)—often termed as the center of glenohumeral joint—as fixed joint. In reality, shoulder joint ICR does move during shoulder abduction–adduction and vertical flexion–extension. The abduction–adduction causes shoulder joint ICR to move in the frontal plane, resulting from a combined motion of shoulder depression–elevation and horizontal translation, while vertical flexion–extension produces a movement of shoulder protraction–retraction. If these additional motions are not compensated in exoskeleton design, they can produce discomfort and/or pain to the robot’s wearer. While in most of the exoskeleton, shoulder joint articulation is considered as a 3-DOFs spherical joint, this research proposes a novel shoulder joint mechanism of robotic exoskeleton with two additional passive DOFs to provide ergonomic shoulder movement. The mechanisms in proposed robotic shoulder comprises of two sliders that allow above-mentioned passive movements of shoulder joint ICR. In this research, we demonstrated that the slider-1 enables shoulder joint ICR to move in the frontal plane with a quarter circular arc of 60 mm during abduction–adduction, while slider-2 allows movement of shoulder protraction–retraction as needed. Proposed mechanism has been designed to be used eventually in a 7 DOF modular robotic exoskeleton for upper limb rehabilitation. We have also applied computed torque control (CTC) to the designed shoulder. The performance of CTC shows stability and effectiveness.

Pilot testing of the spring operated wearable enhancer for arm rehabilitation (SpringWear)

BackgroundRobotic devices for neurorehabilitation of movement impairments in persons with stroke have been studied extensively. However, the vast majority of these devices only allow practice of stereotyped components of simulated functional tasks in the clinic. Previously we developed SpringWear, a wearable, spring operated, upper extremity exoskeleton capable of assisting movements during real-life functional activities, potentially in the home. SpringWear assists shoulder flexion, elbow extension and forearm supination/pronation. The assistance profiles were designed to approximate the torque required to move the joint passively through its range. These three assisted DOF are combined with two passive shoulder DOF, allowing complex multi-joint movement patterns.MethodsWe performed a cross-sectional study to assess changes in movement patterns when assisted by SpringWear. Thirteen persons with chronic stroke performed range of motion (ROM) and functional tasks, including pick and place tasks with various objects. Sensors on the device measured rotation at all 5 DOF and a kinematic model calculated position of the wrist relative to the shoulder. Within subject t-tests were used to determine changes with assistance from SpringWear.ResultsMaximum shoulder flexion, elbow extension and forearm pronation/supination angles increased significantly during both ROM and functional tasks (p < 0.002). Elbow flexion/extension ROM also increased significantly (p < 0.001). When the subjects volitionally held up the arm against gravity, extension at the index finger proximal interphalangeal joint increased significantly (p = 0.033) when assisted by SpringWear. The forward reach workspace increased 19% (p = 0.002). Nine subjects could not complete the functional tasks unassisted and only one showed improvement on task completion with SpringWear.ConclusionsSpringWear increased the usable workspace during reaching movements, but there was no consistent improvement in the ability to complete functional tasks. Assistance levels at the shoulder were increased only until the shoulder could be voluntarily held at 90 degrees of flexion. A higher level of assistance may have yielded better results. Also combining SpringWear with HandSOME, an exoskeleton for assisting hand opening, may yield the most dramatic improvements in functional task performance. These low-cost devices can potentially reduce effort and improve performance during task practice, increasing adherence to home training programs for rehabilitation.

Design and control of an assistive exoskeleton with passive toe joint

Several exoskeletons with various configurations and degrees-of-freedoms (DOFs) have been introduced in the literature, but not many have addressed the optimal selection of the mechanism's DOFs. In the proposed system a semi-passive toe joint is introduced to achieve several advantages. The performance of the proposed novel passive toe joint is evaluated experimentally. In addition, the semi-passive abduction/adduction DOFs in the hip joint and eversion/inversion DOFs in ankle joint is proposed to facilitate turning while providing more comfort during normal walking. The effect of passive DoFs existence on the user comfortability is studied with the aid of three kinematic indices. In the proposed mechanism, a set of compact, low-backlash rotary series elastic actuators are designed and incorporated to actuate the joints. A novel torque control is also introduced and evaluated experimentally. Results show good performance of the robot in zero-force control and impedance control during swing phase of motion.

Biomechanical design of an agile, electricity-powered lower-limb exoskeleton for weight-bearing assistance

This paper proposes the design of an electricity-powered lower-limb exoskeleton called “Human Universal Mobility Assistance (HUMA)”. HUMA was developed as a research platform with the objective of providing its wearer with weight-bearing assistance for human strength/endurance augmentation. It has 12 degrees of active/spring passive/free passive freedom to assist human locomotion. The artificial leg has two electricity-powered degrees of freedom (DoFs) for hip/knee flexions/extensions, passive spring-installed two DoFs for ankle inversion/eversion and plantarflexion/dorsiflexion, and two free, passive DoFs for hip roll/yaw movements. HUMA has mechanical structures for active artificial hip and knee joints; the hip actuator is not directly connected to the robot’s leg system, but a universal joint is installed between the actuator and the leg system to allow a free coaxial hip yaw/roll DoF for the wearer. Therefore, the hip-actuating torque is transferred solely for hip flexion/extension. Its active artificial knee is structured by a four bar-based polycentric linkage, and is power=driven by an actuator in the middle of the robot’s thigh segment through the other four bar-based power transmission linkage. This powered knee structure yields several advantages related to (1) human–robot knee alignment during leg motion, (2) the expansion of the zone of voluntary knee stability, (3) the angle-dependent variable knee torque/velocity amplification ratio, and (4) a reduction in the total moment of artificial leg inertia. The exoskeleton was tested for dynamic gait by using assistive torques determined by a control algorithm. Experiments were conducted on the robot while it walked at 5 km/h (≈1.39 m/s) with/without a 20 kg load, as well as for a 10-km/h (≈2.78 m/s) run.

Unified recursive derivation and analysis of complex associated linkages with various links and type synthesis of complex robot mechanisms

It has been a significant and challenging issue to synthesize novel complex robot mechanisms to create the equipments/devices such as flexible hand-finger, flexible leg-feet, waist, the propeller generator of submarine or helicopter, artificial heart, flexible airfoil, and bionic mechanism. In this paper, an approach for recursively deriving the complex-associated linkages (ALs) with various links is proposed, and novel mechanisms with high complexity coefficient c are synthesized using derived ALs and the topology graph. First, the concepts of c and the various links Li with i connection joints are explained, and various kinematic pairs with multi-DoF are replaced with binary links L2 and connection joints J. Second, the unified recursive formulae are derived for solving c, Li (2 ≤ i) and the maximum number of Li as 0 ≤ c. Third, the 839 ALs with different groups of Li (2 ≤ i ≤ 8) as to 0 ≤ c ≤ 10 are derived utilizing the unified recursive formulae and a relative algorithm. The relations among c, AL, Li (2 ≤ i), redundant constraint, passive DoF and prescript DoF of the mechanisms are discovered. Finally, several examples are given to illustrate the approach of type synthesis of novel complex mechanisms using derived ALs and the topology graph. The recursively derived formulae and proposed approach are verified to be correct and effective.

Robotic System for MRI-guided Focal Laser Ablation in the Prostate.

MRI-conditional robotic platforms have proved to be an effective approach for image guided interventions. In this study, a computer-assisted, pneumatically-actuated robot was designed, built, and tested for MRI-guided prostate cancer focal laser ablation (FLA). The robotic manipulator provides two active planar degrees of freedom (DoFs) by using a customized CoreXY frame, and one passive rotational DoF. A remote insertion mechanism improves the surgical workflow by keeping the patients inside the scanner during needle insertion. The robotic manipulator was tested in a 3T MR scanner to evaluate its MR compliance, and the results demonstrated that the signal-to-noise ratio (SNR) variation was less than 8%. The in-scanner template positioning accuracy test demonstrated that the manipulator achieves high targeting accuracy with a mean error of 0.46 mm and a standard deviation of 0.25mm. Phantom studies have shown that the needle insertion accuracy of the manipulator is within 2mm (Mean = 1.7mm, StD = 0.2mm).

The Coupler Surface of the RSRS Mechanism

Two degree-of-freedom (2-DOF) closed spatial linkages can be useful in the design of robotic devices for spatial rigid-body guidance or manipulation. One of the simplest linkages of this type, without any passive DOF on its links, is the revolute-spherical-revolute-spherical (RSRS) four-bar spatial linkage. Although the RSRS topology has been used in some robotics applications, the kinematics study of this basic linkage has unexpectedly received little attention in the literature over the years. Counteracting this historical tendency, this work presents the derivation of the general implicit equation of the surface generated by a point on the coupler link of the general RSRS spatial mechanism. Since the derived surface equation expresses the Cartesian coordinates of the coupler point as a function only of known geometric parameters of the linkage, the equation can be useful, for instance, in the process of synthesizing new devices. The steps for generating the coupler surface, which is computed from a distance-based parametrization of the mechanism and is algebraic of order twelve, are detailed and a web link where the interested reader can download the full equation for further study is provided. It is also shown how the celebrated sextic curve of the planar four-bar linkage is obtained from this RSRS dodecic.

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.

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.

20.18 Inverse-dynamics based assessment of walking using a robotic gait orthosis

This paper proposes the design of an electricity-powered lower-limb exoskeleton called “Human Universal Mobility Assistance (HUMA)”. HUMA was developed as a research platform with the objective of providing its wearer with weight-bearing assistance for human strength/endurance augmentation. It has 12 degrees of active/spring passive/free passive freedom to assist human locomotion. The artificial leg has two electricity-powered degrees of freedom (DoFs) for hip/knee flexions/extensions, passive spring-installed two DoFs for ankle inversion/eversion and plantarflexion/dorsiflexion, and two free, passive DoFs for hip roll/yaw movements. HUMA has mechanical structures for active artificial hip and knee joints; the hip actuator is not directly connected to the robot’s leg system, but a universal joint is installed between the actuator and the leg system to allow a free coaxial hip yaw/roll DoF for the wearer. Therefore, the hip-actuating torque is transferred solely for hip flexion/extension. Its active artificial knee is structured by a four bar-based polycentric linkage, and is power=driven by an actuator in the middle of the robot’s thigh segment through the other four bar-based power transmission linkage. This powered knee structure yields several advantages related to (1) human–robot knee alignment during leg motion, (2) the expansion of the zone of voluntary knee stability, (3) the angle-dependent variable knee torque/velocity amplification ratio, and (4) a reduction in the total moment of artificial leg inertia. The exoskeleton was tested for dynamic gait by using assistive torques determined by a control algorithm. Experiments were conducted on the robot while it walked at 5 km/h (≈1.39 m/s) with/without a 20 kg load, as well as for a 10-km/h (≈2.78 m/s) run.

Systematic development of vehicle suspensions having passive DOF and/or redundant constraint

This study provides a new systematic approach for the design of a mechanism having passive DOF and/or redundant constraints, with the specific application for the design of new vehicle suspensions. Suspension candidates having passive DOF are obtained by adding chains having passive DOF to the basic mechanisms that have neither passive DOF nor redundant constraint. In this way, we can handle those mechanisms that have passive DOF. Suspension candidates with redundant constraint can be obtained by transforming 2D planar mechanisms into 3D mechanisms having a similar motion pattern. The proposed algorithm has the advantage of effectively manipulating mechanisms that may have passive DOF and/or redundant constraints. Using this algorithm, we obtained 18 mechanisms that can be considered for the front suspension. To evaluate these suspensions, we analysed the kinematics of these candidates and performed dimensional synthesis for the desired toe and camber angle trajectories. In the results, we could identify some suspension candidates that have a smaller deviation from the desired values of toe and camber angle trajectories.