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Lower Extremity Exoskeletons and Active Orthoses Challenges and Stateoftheart

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Exoskeletons and orthoses: classification, blueprint challenges and futurity directions

Journal of NeuroEngineering and Rehabilitation volume six, Article number:21 (2009) Cite this article

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Abstract

For over a century, technologists and scientists have actively sought the evolution of exoskeletons and orthoses designed to augment human economy, strength, and endurance. While there are however many challenges associated with exoskeletal and orthotic design that have yet to exist perfected, the advances in the field accept been truly impressive. In this commentary, I first allocate exoskeletons and orthoses into devices that act in series and in parallel to a man limb, providing a few examples within each category. This nomenclature is and then followed by a word of major design challenges and future research directions critical to the field of exoskeletons and orthoses.

Introduction

The current series of the Journal of NeuroEngineering and Rehabilitation (JNER) is defended to recent advances in robotic exoskeletons and powered orthoses. The articles in this special issue cover a wide spectrum of embodiments, from orthotic devices to assist individuals suffering from limb pathology to limb exoskeletons designed to augment normal, intact limb part.

To set up the phase for this special issue, I classify exoskeletons and orthoses into four categories and provide design examples within each of these. I hash out devices that act in series with a human being limb to increment limb length and displacement, and devices that act in parallel with a homo limb to increment homo locomotory economy, augment joint strength, and increase endurance or force. For each exoskeletal type, I provide a pattern overview of hardware, actuation, sensory, and control systems for a few characteristic devices that have been described in the literature, and when available, draw the results of any quantitative evaluation of the effectiveness of the devices in performing their intended tasks. Finally, I stop with a discussion of the major design challenges that have nevertheless to be overcome, and possible future directions that may provide resolutions to these design difficulties.

For the purposes of this commentary, exoskeletons and orthoses are defined as mechanical devices that are essentially anthropomorphic in nature, are 'worn' by an operator and fit closely to the body, and work in concert with the operator's movements. In general, the term 'exoskeleton' is used to describe a device that augments the performance of an able-bodied wearer, whereas the term 'orthosis' is typically used to describe a device that is used to assist a person with a limb pathology.

It is maybe worth noting that the term "exoskeleton" has come to describe systems that are comprised of more than just a passive protective and supporting vanquish, as its usage in biology would suggest. "Exoskeleton" within our research community is taken to include mechanical structures, every bit well every bit associated actuators, visco-rubberband components, sensors and command elements.

Serial-limb exoskeletons

Elastic elements in the body, such as ligaments and tendons, have long been known to play a critical role in the economy and stability of motion [i–vii]. Humans and other animals utilise these tissues to reduce impact losses while storing substantial quantities of energy when striking the ground, and to provide propulsion during terminal stance in walking, running and jumping. Such biological strategies have inspired designers of running track surfaces and wearable devices such as shoes and exoskeletons.

Previous studies take shown that a compliant running track can meliorate performance by increasing running speed by a few percent and may too reduce the risk of injury [8]. In another written report on elastic running surfaces, the authors establish a range of compliant basis surface stiffnesses that improved metabolic running economy [9]. Similarly, previous studies have shown that vesture mechanisms in series with the biological leg can reduce the metabolic cost of running by lowering touch losses and by providing energy return. A running shoe called the Springbuck, designed with a carbon composite elastic midsole, was shown to better shock absorption and metabolic economy at moderate running speeds (see Effigy 1a); [ten, 11]. Although metabolic economy improved when runners used this elastic shoe rather than a conventional shoe design without an elastic midsole, the advantage was found to be small (~2%). Elastic exoskeletons in serial with the human leg accept been developed that shop and release far greater strain energy than the running track surface of [8] or the Springbuck shoe [x, 11] (~five Joules/step for track and shoe versus ~80 Joules/step for rubberband exoskeletons), and therefore it was believed that such exoskeletons would augment human running speed and economy. Notable inventions in this exoskeletal grade are the PowerSkip and the SpringWalker shown in Figure 1b and 1c, respectively http://www.powerskip.de; [12]. Nevertheless, although these devices conspicuously augment jumping summit, they have not been shown to better pinnacle running speed nor running economy. In fact, in a study conducted past the U.S. Army Research Establish of Environmental Medicine (ARIEM) in Natick, Massachusetts, the SpringWalker increased metabolic cost by twenty% compared to locomotion without the device [Personal Advice: Peter Frykman]. For this study, mass was added to the field of study's dorsum equal to the SpringWalker mass.

Figure 1
figure 1

Shoes and exoskeletons that act in series with the human being lower limb. Examples are the Springbuck shoe [10, xi], the PowerSkip exoskeleton http://www.powerskip.de, and the SpringWalker exoskeleton [12] shown in 1a, 1b, and 1c, respectively.

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Parallel-limb exoskeletons for load transfer

Hither we discuss exoskeletons that human action in parallel with the human being lower limb for load transfer to the ground. Possibly an in-serial leg exoskeleton like the SpringWalker (Effigy 1c) increases the metabolic cost of running because the limb length of the human being plus machine is substantially increased, thereby increasing both the piece of work at the hip to protract the leg during the aeriform phase and the overall energetic demand to stabilize movement, overcoming any potential reward of extending limb length. Additionally, with an in-series leg exoskeleton device, the ground reaction forces are even so borne by the homo leg. In contrast, with a parallel mechanism, body weight could be transferred through the exoskeleton directly to the footing, decreasing the loads borne past the biological limbs and lowering the metabolic demands to walk, run, and hop. Furthermore, such a parallel exoskeleton would not increase limb length, thereby not increasing the overall energetic demand to stabilize movement.

The earliest mention of such a parallel exoskeleton is a set of United States patents granted in 1890 to Nicholas Yagn [xiii, 14]. His invention, shown in Figure 2a, comprises long leaf springs operating in parallel to the legs, and was intended to broaden the running abilities of the Russian Ground forces. Each leg spring was designed to engage at pes strike to effectively transfer the trunk'southward weight to the ground and to reduce the forces borne by the opinion leg during each running opinion period. During the aerial phase, the parallel leg leap was designed to undo in guild to allow the biological leg to freely flex and to enable the foot to clear the basis. Although Yagn's mechanism was designed to augment running, in that location is no record that the device was always built and successfully demonstrated.

Effigy ii
figure 2

Exoskeletons that act in parallel with the man lower limb for load transfer to the ground. Examples are Yagn'south running aid [14], MIT's hopping exoskeleton [15, sixteen], and Kazerooni's load-conveying exoskeleton [xviii, 19] shown in 2a, 2b, and 2c, respectively.

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The MIT Biomechatronics Group recently built an elastic exoskeleton similar to Yagn's design. However, its intended application was not for running augmentation, but for lowering the metabolic demands of continuous hopping [15, xvi]. The exoskeleton, shown in Effigy 2b, comprises fiberglass leafage springs that bridge the entire leg, and is capable of transferring body weight straight to the basis during the stance menstruation. In distinction to Yagn's exoskeleton, the MIT device does non include a clutch to undo the exoskeletal leaf jump during the aerial phase since such a clutching command was accounted unnecessary for hopping. Without accounting for the added weight of each exoskeleton, wearing the exoskeleton reduced internet metabolic power for continuous hopping by an average of 24% compared to normal hopping [16]. When hoppers utilized external parallel springs, they decreased the mechanical work performed by the legs and substantially reduced metabolic demand compared to hopping without wearing an exoskeleton. Since the biomechanics of hopping are like to that of running, it seems plausible that the effects of wearing an exoskeleton during hopping could predict the biomechanical and metabolic effects of wearing an exoskeleton during running, and that substantial energetic advantages might be achieved while running with a highly rubberband, parallel leg exoskeleton. Clearly, for the goal of augmenting human running performance, lightweight and highly elastic leg exoskeletons that human action in parallel with the man leg provide a research surface area of critical importance.

Parallel-limb exoskeletons have also been advanced to augment the load-carrying capacity of humans [17–32]. This blazon of leg exoskeleton could do good people who appoint in load carrying by increasing load chapters, lessening the likelihood of leg or back injury, improving metabolic locomotory economy, and/or reducing the perceived level of difficulty. One such exoskeletal design is shown in Figure 2c, or the Berkeley Lower Extremity Exoskeleton (BLEEX) developed past Professor Kazerooni. One of the distinguishing features of this exoskeleton is that it is energetically autonomous, or carries its own power source. Indeed, its developers claim it as the first "load-bearing and energetically autonomous" exoskeleton [17].

BLEEX features three degrees of freedom (DOF) at the hip, one at the genu, and iii at the talocrural joint. Of these, four are actuated: hip flexion/extension, hip abduction/adduction, knee flexion/extension, and ankle flexion/extension. Of the non-actuated joints, the talocrural joint inversion/eversion and hip rotation joints are spring-loaded, and the ankle rotation articulation is gratis-spinning [18]. The kinematics and actuation requirements of the exoskeleton were designed by assuming behavior similar to that of a 75 kg human and utilizing clinical gait assay data for walking [18, 19].

Interesting features of the kinematic design of the exoskeleton include a hip "rotation" joint that is shared betwixt the ii legs of the exoskeleton, and therefore, does not intersect with the wearer's hip joints. Similarly, the inversion/eversion joint at the ankle is non co-located with the human joint, but is ready to the lateral side of the foot for simplicity. The other five rotational DOF'southward of the exoskeleton coincide with the joints of the wearer [18].

The exoskeleton is actuated via bidirectional linear hydraulic cylinders mounted in a triangular configuration with the rotary joints, resulting in an effective moment arm that varies with joint bending. BLEEX consumes an average of 1143 Watts of hydraulic power during level-ground walking, equally well as 200 Watts of electrical ability for the electronics and command. In dissimilarity, a similarly sized, 75 kg human being consumes approximately 165 W of metabolic power during level-basis walking [xviii, xix].

BLEEX was designed with linear hydraulic actuators since they were the "smallest actuation option available" based on their "high specific power (ratio of actuator power to actuator weight)" [18]. Nevertheless, a farther study determined that electrical motor actuation significantly decreased power consumption during level walking in comparing to hydraulic actuation [20]. The weight of the implementation of the electrically-actuated joint, even so, was approximately twice that of their hydraulically-actuated articulation (four.1 kg vs. two.1 kg).

The command scheme of the BLEEX seeks to minimize the apply of sensory data from the human/exoskeleton interaction, and instead, utilizes mainly sensory information from the exoskeleton. Similarly to a bipedal robot, the exoskeleton can balance on its own, but the human wearer must provide a forward guiding forcefulness to straight the system during walking. The control system utilizes the information from eight encoders and xvi linear accelerometers to determine angle, angular velocity, and angular acceleration of each of the viii actuated joints, a foot switch, and load distribution sensor per foot to determine ground contact and strength distribution between the feet during double opinion, eight single-axis forcefulness sensors for use in force control of each of the actuators, and an inclinometer to decide the orientation of the haversack with respect to gravity [18].

In club to achieve their goal of being energetically autonomous with such an actuator selection, pregnant effort was invested in developing a hybrid hydraulic-electric portable power supply [21].

In terms of operation, users wearing BLEEX can reportedly support a load of up to 75 kg while walking at 0.9 m/south, and can walk at speeds of upward to 1.three m/s without the load. A second generation of the Berkeley exoskeleton is currently in testing. The new device is approximately half the weight of the original exoskeleton (~14 kg [22]), in part due to the implementation of electric actuation with a hydraulic manual arrangement. A laboratory spin-off company called Berkeley Bionics (Berkeley, CA) has been formed in order to market the exoskeleton applied science.

Parallel-limb exoskeletons for torque and piece of work augmentation

Here we hash out exoskeletons that act in parallel with the human joint(s) for torque and work augmentation. Many parallel-limb exoskeletons accept been developed to augment joint torque and work [33–58]. In stardom to the load-carrying exoskeletons mentioned in the concluding section, this type of exoskeletal and orthotic device does not transfer substantial load to the ground, but simply augments joint torque and work. This type of leg exoskeleton could improve walking and running metabolic economy, or might be used to reduce articulation pain or increase articulation strength in paralyzed or weak joints.

Ane such exoskeletal design is shown in Figure 3a. At the University of Tsukuba in Japan, Professor Yoshiyuki Sankai and his team accept been developing an exoskeleton concept that is targeted for both functioning-augmenting and rehabilitative purposes [49, 50]. The leg structure of the full-body HAL-5 exoskeleton powers the flexion/extension joints at the hip and knee via a DC motor with harmonic drive placed directly on the joints. The ankle flexion/extension degree of freedom is passive. The lower-limb components interface with the wearer via a number of connections: a special shoe with ground reaction force sensors, harnesses on the dogie and thigh, and a broad waist belt.

Figure three
figure 3

Exoskeletons that act in parallel with man joint(southward) for torque and work augmentation. Examples are the HAL five exoskeleton [49, 50] and the MIT active ankle-foot orthosis [52] shown in 3a and 3b, respectively.

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The HAL-v system utilizes a number of sensing modalities for control: peel-surface EMG electrodes placed below the hip and above the knee on both the anterior (front) and posterior (back) sides of the wearer's torso, potentiometers for articulation angle measurement, ground reaction strength sensors, a gyroscope and accelerometer mounted on the haversack for torso posture estimation. These sensing modalities are used in ii control systems that together determine user intent and operate the conform: an EMG-based system and a walking design-based organization. Reportedly, it takes 2 months to optimally calibrate the exoskeleton for a specific user [22].

HAL-5 is currently in the process of being readied for commercialization. Modifications from previous versions include upper-body limbs, lighter and more meaty power units, longer battery life (approximately 160 minutes continuous operating fourth dimension), and a more cosmetic shell. The full weight of the full-trunk device is 21 kg. Cyberdyne (Tsukuba, Japan, http://www.cyberdyne.jp), a company spun off from Sankai'due south lab, is responsible for the commercialization of the product.

The ability of HAL to meliorate operation by increasing the user's capacity to elevator and press large loads has been demonstrated http://world wide web.cyberdyne.jp. An operator wearing HAL can lift up to twoscore kg more than they tin can manage unaided. Additionally, the device increases the user's 'leg press' capability from 100 to 180 kg. Still, to date no peer-reviewed, quantitative results take been published highlighting the effectiveness of the exoskeleton's lower-limb components for the improvement of locomotory role.

A second instance of a parallel-limb orthosis that augments joint torque and work is shown in Figure 3b. The MIT Biomechatronics Group adult a powered talocrural joint-human foot orthosis [52] to assistance drop-foot gait, a deficit affecting many persons who have experienced a stroke, or with multiple sclerosis or cerebral palsy, amongst others. The device consists of a modified passive talocrural joint-foot orthosis with the add-on of a series rubberband actuator (Body of water) that is controlled based on basis force and angle sensory information. Using the SEA, the device varies the impedance of the talocrural joint during controlled plantar flexion in stance, and assists with dorsiflexion during the swing phase of walking.

In clinical trials, the MIT active ankle-foot orthosis (AFO) was shown to ameliorate the gait of drop-foot patients by increasing walking speed, reducing the instances of "pes slap", creating meliorate symmetry with the unaffected leg, and providing assistance during powered plantar flexion. Subjects' feedback was as well favorable. The AFO is relatively meaty and consumes a minor amount of ability (10W average electrical ability consumption), and current piece of work at iWalk, LLC http://www.iwalkpro.com, a spin-off company from MIT, is focused on developing an energetically autonomous, portable version of the device.

Parallel-limb exoskeletons that increase human endurance

Throughout the human body hundreds of muscles exert forces to stiffen and move the limbs and trunk. During exhaustive exercise, only a small portion of these muscles fatigue. For a repetitive anaerobic activity, a parallel-limb exoskeleton could be designed to redistribute the circadian work load over a greater number of muscles for the purpose of delaying the onset of fatigue. In such a strategy, springs within the exoskeleton could be stretched by muscles that would non ordinarily fatigue if the practise were conducted without the machinery. The energy stored by the exoskeleton could and then be used to aid those muscles that would typically fatigue, possibly improving endurance capacity.

To examination whether information technology is indeed possible for an exoskeleton to amplify endurance using this strategy, researchers [59] conducted an experiment on six human subjects each wearing a simple exoskeleton comprised of two springs that connected each wrist to a waist harness (see Effigy 4a). The springs were in equilibrium when both elbows were fully flexed with the wrists positioned at chest height. With this mechanism, a subject area performed the post-obit cyclic activity until consummate exhaustion using a given spring stiffness. From a sitting position, a subject fully extended his arms to grasp a pull-upwardly bar directly overhead, stretching the arm springs. With the assistance of the stretched springs, the subject field lifted his body upwards with his arms until his chin cleared the bar. Then the subject stood on the seat of a chair, released the bar, and sat down on the chair. Note that the cycle did not include lowering the torso with the arms after pulling up. Using this approach, energy was simply stored in the springs by extending the arms upward. Each subject area performed the experiment five times with a given spring stiffness using a total of five different spring stiffnesses. The order in which spring stiffnesses were used was randomized to rule out any sequential effects. In addition, each subject was required to apply the same time to sit down downwards after pulling up so that the time in which the arms were non being used during each bike did not change. Betwixt experiments, a field of study was given two to three days of rest.

Figure 4
figure 4

Exoskeletons that act in parallel with a man limb for endurance augmentation. An instance is the MIT climbing exoskeleton [59] shown in 4a. Every bit shown in 4b, when the stiffness of the mechanism was optimally tuned, endurance was increased from ane.5-fold to 2.5-fold across the six human subjects evaluated. The mean number of cycles to exhaustion (), or the endurance, normalized by the mean value at zero stiffness (), is plotted in Fig. 4b versus the dimensionless arm jump stiffness (K). K is defined as the measured stiffness of the added spring (k) multiplied by the maximum distance the spring was stretched (Xm), and divided past the subject's torso weight (Due west). For each subject, a cubic spline curve passes through the mean of the normalized cycle values (± SE) at each of the five stiffness values. Endurance is maximized around K ~0.25 for each subject field.

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The experimental results are shown in Effigy 4b. The endurance was maximized effectually K ~0.25 for each subject field. Farther, the endurance with an exoskeleton increased by ane.v-fold to 2.5-fold compared to the endurance when no exoskeleton aid was employed. Using a mathematical model of the human arm and exoskeleton, researchers [59] related overall muscle efficiency to exoskeletal stiffness. The model predicted that muscle efficiency was maximized at the same dimensionless stiffness where endurance reached its maximum (K~0.25 in Effigy 4b), suggesting that the endurance changes were a consequence of changes in the efficiency with which the body performed the required work for each bike.

At that place are many applications for this class of exoskeleton. For case, a crutch was constructed with an orthotic elbow spring to maximize the endurance of physically-challenged persons in climbing stairs and slopes [sixty]. When the crutch user flexes both elbows to place the crutch tips onto the next stair tread, orthotic elbow springs compress and store energy. This stored energy then assists the crutch user during elbow extension, helping to lift the body up the next step, and delaying the onset of bicep and tricep muscle fatigue. In futurity developments, robotic exoskeletons and powered orthoses could be put forth that actively vary impedance to optimally redistribute the torso's work load over a greater muscle book, maximizing the efficiency with which the body is able to perform mechanical work and significantly augmenting human endurance.

Blueprint challenges and future directions

Although great progress has been made in the century-long effort to pattern and implement robotic exoskeletons and powered orthoses, many design challenges still remain. Remarkably, a portable leg exoskeleton has all the same to be developed that demonstrates a meaning decrease in the metabolic demands of walking or running. Many complicated devices have been developed that increase consumption, such as the SpringWalker [12] and the MIT load-carrying exoskeleton [27–29].

There are many factors that continue to limit the performance of exoskeletons and orthoses. Today's powered devices are often heavy with limited torque and power, making the wearer's movements hard to augment. Electric current devices are frequently both unnatural in shape and noisy, factors that negatively influence device cosmesis. Given electric current limitations in actuator technology, continued research and development in artificial muscle actuators is of critical importance to the field of habiliment devices. Electroactive polymers have shown considerable promise every bit artificial muscles, simply technical challenges all the same remain for their implementation [61, 62]. These challenges include improving the actuator'due south durability and lifetime at high levels of functioning, scaling up the actuator size to meet the force and stroke needs of exoskeletal/orthotic devices, and advancing efficient and meaty driving electronics. Although difficulties remain, electroactive polymer muscles may offer considerable advantages to wearable robotic devices, allowing for integrated joint impedance and motive force controllability, noise-complimentary operation, and anthropomorphic device morphologies. An improved understanding of musculus and tendon part during homo movement tasks may shed light on how artificial muscles should ideally adhere to the exoskeletal frame (monoarticular vs. polyarticular actuation) and be controlled to produce enhanced biomimetic limb dynamics. For case, neuromechanical models that capture the major features of human walking (e.g. [63, 64]) may better agreement of musculoskeletal morphology and neural control and lead to coordinating improvements in the blueprint of economical, stable and low-mass exoskeletons for human walking augmentation.

Another factor limiting today's exoskeletons and orthoses is the lack of straight information commutation betwixt the human wearer'south nervous system and the wearable device. Continued advancements in neural engineering volition be of disquisitional importance to the field of vesture robotics. Peripheral sensors placed inside muscle to measure the electromyographic bespeak, or centrally-placed sensors into the motor cortex, may be used to assess motor intent past future exoskeletal control systems [65, 66]. Neural implants may take the potential to exist used for sensory feedback to the nerves or brain, thus allowing the exoskeletal wearer to have some form of kinetic and kinematic sensory data from the wearable device [67].

Current exoskeletal/orthotic devices are besides limited past their mechanical interface. Today's interface designs frequently cause discomfort to the wearer, limiting the length of fourth dimension that a device tin be worn. Information technology is certainly an achievable goal to provide comfortable and effective mechanical interfaces with the man body. Contemporary external prosthetic limbs adhere to the human being body most commonly via a prosthetic socket that is custom fabricated to an individual's ain contours and anatomical needs. Although non a perfectly comfortable interface, today's prosthetic sockets notwithstanding allow amputee athletes to run marathons, compete in the Ironman Triathlons, and even climb Mount Everest. I strategy employed in the fabrication of modernistic prostheses is to digitize the surface of the residual limb, creating a three dimensional digital description of the residue limb contours. Once the amputee's limb has been scanned, their geometric data are sent to a computer aided manufacturing (CAM) facility where a new prosthetic socket is fabricated rapidly and at relatively low cost.

In the future such file-to-manufacturing plant rapid processes may be employed for the design and structure of exoskeletal and orthotic devices. In this framework, a three dimensional scanning process would produce a digital record of the human body's outer shape. This geometric information along with other anatomical information, such as information on tissue compliance and anatomically-sensitive areas, would be combined with force and endurance information from a concrete fitness diagnostic examination. Such anatomical and fitness data, combined with the wearer's augmentation requirements, would provide an individual's design specification profile. An exoskeleton, customized to fit the wearer'southward outer anatomical features and physiological demands, would then be designed equally a '2d peel'. Such a skin would be fabricated compliant in body regions having bony protuberances, and more than rigid in areas of loftier tissue compliance. The exoskeletal pare would be and so intimate with the human trunk that external shear forces practical to the exoskeleton would not produce relative move betwixt the exoskeletal inner surface and the wearer's own pare, eliminating peel sores resulting from device rubbing. Compliant bogus muscles, sensors, electronics and ability supply would exist embedded within the 3 dimensional construct, offering total protection of these components from ecology disturbances such as dust and moisture. One time designed, device construction would unite additive and subtractive fabrication processes to deposit materials with varied properties (stiffness and density variations) across the entire exoskeletal book using large scale 3-D printers and robotic artillery.

Exoskeletons and the time to come of mobility

During the 20thursday century, investments in homo-mobility technology primarily focused on wheeled devices. Relatively little investment was focused on the advancement of anthropomorphic exoskeletal technologies that let humans to movement bipedally at enhanced speeds and with reduced endeavour and metabolic toll. Information technology seems likely that in the 21st century more investments will be made to drive innovation in this important area. The fact that large automobile companies, such every bit Honda and Toyota, have recently begun exoskeletal inquiry programs is an indication of this technological shift. Perhaps in the latter one-half of this century, exoskeletons and orthoses will be as pervasive in order as wheeled vehicles are today. That would permit the elderly, the physically challenged and persons with normal intact physiologies to achieve a level of mobility not yet achieved. That would be a 24-hour interval in which the machine – that big, metal box with four wheels – is replaced with wearable, all-terrain exoskeletal devices, allowing city streets to be transformed from 20thursday century pavement to clay, trees and rocks. I can simply promise.

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Acknowledgements

This work was supported in office by the MIT Media Lab Consortia.

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  1. MIT Media Lab, Massachusetts Constitute of Technology, twenty Ames Street, Room 424, Cambridge, Massachusetts, Us

    Hugh Herr

  2. MIT-Harvard Segmentation of Wellness Science and Engineering science, Massachusetts Institute of Engineering science, 20 Ames Street, Room 424, Cambridge, Massachusetts, USA

    Hugh Herr

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Correspondence to Hugh Herr.

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The author is founder of iWalk, LLC, a company defended to the commercialization of vesture robotic technology for human augmentation.

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Herr, H. Exoskeletons and orthoses: classification, design challenges and time to come directions. J NeuroEngineering Rehabil 6, 21 (2009). https://doi.org/10.1186/1743-0003-half dozen-21

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Keywords

  • Wearable Device
  • Leaf Spring
  • Artificial Muscle
  • Residual Limb
  • Orthotic Device

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