Wearable Exoskeleton Systems: Design, control and applications
2: InnotecUK, UK
3: Department of Engineering, Arizona State University, AZ, USA
Wearable exoskeletons are electro-mechanical systems designed to assist, augment, or enhance motion and mobility in a variety of human motion applications and scenarios. The applications, ranging from providing power supplementation to assist the wearers to situations where human motion is resisted for exercising applications, cover a wide range of domains such as medical devices for patient rehabilitation training recovering from trauma, movement aids for disabled persons, personal care robots for providing daily living assistance, and reduction of physical burden in industrial and military applications. The development of effective and affordable wearable exoskeletons poses several design, control and modelling challenges to researchers and manufacturers. Novel technologies are therefore being developed in adaptive motion controllers, human-robot interaction control, biological sensors and actuators, materials and structures, etc. In this book, the authors report recent advances and technology breakthroughs in exoskeleton developments. It will be of interest to engineers and researchers in academia and industry as well as manufacturing companies interested in developing new markets in wearable exoskeleton robotics.
Inspec keywords: synchronisation; medical robotics; wearable robots; assisted living
Other keywords: synchronisation; assisted living; robot design; Ekso Bionics; wearable robotics; robot control; medical applications
Subjects: Prosthetic and orthotic control systems; Robotics; General and management topics
- Book DOI: 10.1049/PBCE108E
- Chapter DOI: 10.1049/PBCE108E
- ISBN: 9781785613029
- e-ISBN: 9781785613036
- Page count: 406
- Format: PDF
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Front Matter
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Section 1 - Review and overall requirements
Section 1 - Review and overall requirements
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The first section consisting of four chapters focuses on an overview of lower limb wearable robots, the development of soft-robotic systems, and their user requirements. Specifically, Chapter 1 gives an overview of lower limb wearable systems and explores the promises and challenges when developing these new types of inherently safe exoskeleton systems. Chapter 2 reviews the current medical- and non-medical (or service-based) exoskeletons being developed in R&D projects funded in Europe. Chapter 3 defines and explains the new field of soft, wearable robots including lower limb exosuits, covering systems to assist the elbow and hand, and devices that can be implanted into the body. Last, Chapter 4 focuses on the user requirements for developing lower limb exoskeletons with a case study focusing on XoSoft, a lower limb exoskeleton using soft robotic technology.
1 Lower-limb wearable robotics
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It is an exciting time in wearable robotics with new devices for spinal cord injury, gait assistance, rehabilitation, strength enhancement, manufacturing, construction, and recreation. This review will focus on lower limb wearable robotic systems that include orthoses, prostheses, and exoskeletons. The promises and challenges of these systems will be described. A review of some of the exciting systems will be presented.
2 Review of exoskeletons for medical and service applications: ongoing Research in Europe on Wearable Robots, with focus on lower extremity exoskeletons
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This chapter presents an overview of European research projects that are involved with research and development of wearable robots, with an emphasis on exoskeletons for the legs. The structure and goals of public European Research funding are explained, the general directions of the recent research in wearable robots are summarized, and a more detailed overview of a selection of the larger European R&D projects in this field is provided. It covers exoskeletons for assistive use as well as for training, for medical as well as for service applications.
3 Soft wearable robots
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This chapter focuses on the recent and growing efforts in the field of soft wearable robotics and discusses how this technology can be used in a variety of contexts. This rapidly emerging field will not replace traditional exoskeletons but offers new possibilities to augment the performance of healthy individuals but also restore function for impaired individuals with residual capacity, i.e. where only small to moderate levels of assistance is needed to improve function ability (e.g. walking, grasping). The application requirements for soft wearable robots are fundamentally different than those for rigid exoskeletons, necessitating fundamental technological development in areas of actuation, human interfaces, sensing, control and system integration.
4 Exploring user requirements for a lower body soft exoskeleton to assist mobility
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Understanding the requirements of potential users is crucial to the successful design of wearable exoskeleton systems. Considering user requirements throughout the design process optimises the likelihood of user uptake and facilitates adherence to the use of wearable systems. This chapter describes the application of a user-centred design approach to the development of a soft lower body assistive exoskeleton for individuals with mild to moderate mobility impairment. Examples of the identification and characterisation of user groups, the use of qualitative and quantitative research methods to explore user requirements, and the implications of user requirements for soft exoskeleton technologies are presented.
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Section 2 - Design and control of exoskeletons
Section 2 - Design and control of exoskeletons
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Creating wearable robotic systems requires unique robot designs and controllers. While industrial manipulators and mobile robots have been extensively studied for over a half century, exoskeleton robots are relative new, with a very short history of less than two decades and there are still many challenges in design and control to be solved. Some major challenges, as the editors foresee, details of include the mechanism design to facilitate and ease physical human-robot interaction, the development and selection of sensors for motion and human motion intention detection, novel actuators with reduced inertia and impedance to make the exoskeletons safe and sufficiently comfortable for short-term and long-term use, and controllers that facilitate the interaction between the wearer and the exoskeleton, among others. In this section, we included four chapters to address separately the above issues.
5 Design and control of spherical shoulder exoskeletons for assistive applications
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The shoulder complex is the most complex joint in human's four limbs and this poses a big challenge in the exoskeleton design to achieve a mechanism able to generate the desired motion while structurally complying with human anatomy. This chapter presents a novel design of an exoskeleton shoulder mechanism and its control. The new design is a hybrid mechanism that consists of two revolute joints connected together via a double parallelogram linkage (DPL). By virtue of a DPL, a remote center of rotation can be established for a spherical mechanism with threedegree-of-rotations. In the chapter, the working principle of the shoulder mechanism is described. The kinematics of the mechanism is analyzed. Mechanism design and exoskeleton control are also presented.
6 Calibration platform for wearable 3D motion sensors
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With the development of microelectromechanical system technologies, wearable motion sensors (WMSs) have played an increasingly significant role in the design of exoskeletons, where the WMSs are used for motion detection, orientation estimation, or position estimation. For these applications, the accuracy of the WMSs will affect the overall performance of the exoskeletons. The purpose of this chapter is to present an evaluation platform for assessing the accuracy of WMSs, assisting to develop or choose proper WMSs for exoskeletons. The presented evaluation platform is an instrumented gimbal with three rotation axes. Each axis is equipped with a DC motor and an absolute encoder. Thus, each axis can be controlled independently, and the rotation angle around each axis can be output accurately. In addition, each axis can rotate continuously via the equipped electrical slip rings. One of the major advantages of the instrumented gimbal is that it can be used for accurate motion analysis without needing any additional equipment. In order to verify the function of the platform, validation experiments were conducted, including a static accuracy test, and dynamic accuracy test with and without magnetic disturbances. Results show that the designed gimbal has good potential for evaluating the orientation of WMSs under different conditions.
7 Control and performance of upper- and lower extremity SEA-based exoskeletons
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In the last years compliant actuators have become extremely popular in the field of wearable robotics, due to their ability to realize safe human-robot interfaces. One of the most well-known example of a compliant actuator is the series elastic actuator (SEA), consisting of an elastic element (e.g. a spring) in series with a stiff actuator; such actuation architecture is considered to be the simplest design solution to realize compliant, compact, and light-weight actuators for wearable robots; in addition, from the control perspective, SEA architecture allows for simple force or torque control in addition to position control. In this chapter, three wearable robots for upperand lower-limb rehabilitation and assistance, developed at The BioRobotics Institute of Scuola Superiore Sant'Anna, are described. The three devices have similar SEA-based actuation units, integrating commercial electromagnetic motors and custom torsional springs, with constant stiffness and linear torque-deformation characteristics. Closed-loop torque control performance show that the systems can be highly transparent when controlled under zero-torque modality, i.e. the interaction with the human is minimal and the actuators do not hinder the user's movement, and bandwidths and output torques are compatible with the human movements to be assisted.
8 Gait-event-based synchronization and control of a compact portable knee—ankle—foot exoskeleton robot for gait rehabilitation
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This chapter presents the mechanical design and control of a knee-ankle-foot exoskeleton robot, which is compact, modular and portable for stroke patients to carry out overground gait training. A novel compact series elastic actuator (SEA) is developed for safe human-robot interactions. In order to control this portable knee-ankle-foot robot, a novel human-robot synchronization method using gait event information is proposed. This method includes two steps. Firstly, seven gait events in one gait cycle are detected in real time with a hidden Markov model (HMM); secondly, an adaptive oscillator is utilized to estimate the stride percentage of human gait using any one of the gait events. Synchronous reference trajectories for the robot are then generated with the estimated stride percentage. The proposed synchronization method is implemented in the robot and tested in 15 healthy subjects. The results of the experiments reveal that our approach is efficient in achieving human-robot synchronization. It shows that this method has the advantages of simple structure, flexible selection of gait events and fast adaptation.
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Section 3 - Devices
Section 3 - Devices
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In this section, a variety of different types of exoskeletons are described, with details of the designs, how they were built, and tested with users. The exoskeletons have been created for different types of markets such as spinal cord injuried persons, medical rehabilitation devices, user assistance exoskeletons, military, industrial, and recreation systems. A good description of commercial devices can be found at www.exoskeletonreport.com and www.wearablerobotics.com.
9 Real-time gait planning for a lower limb exoskeleton robot
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This chapter presents a medical robot exoskeleton developed to assist spinal cord injury patients to walk independently, focusing on real-time gait planning. The exoskeleton robot is built with actuators at the hip and knee joints, and a pair of crutches to help paraplegic patients maintain balance during walking. A real-time gait planning strategy is developed to allow the users to walk stably in a natural manner. This gait planning treats the human-machine coupling system as a quadruped robot and adjusts and corrects gait before each step according to real-time responses of multiple sensors. Taking into account of the kinematic model of people wielding crutches, this gait planning strategy provides a larger stability margin for the system. Results of experiments are presented to illustrate the effectiveness of the proposed gait planning method.
10 Soft wearable assistive robotics: exosuits and supernumerary limbs
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The intrinsic soft nature of compliant supernumerary limbs and exosuits makes them appealing candidates for assisting human movements, with potential applications in healthcare, human augmentation and logistics. In the following chapter, we describe the technology used in exosuits and supernumerary limbs for assistance of activities of daily living, with emphasis on aiding grasping and flexion/ extension of the elbow joint. We discuss the mechanical design principles of such devices, detail the control paradigms that can be used for intention-detection and present the design and evaluation of cutaneous interfaces used for force feedback rendering. Tests on healthy and impaired subjects highlight that exosuits and supernumerary limbs are potential cost-effective and intrinsically safe solutions for increasing the capabilities of healthy subjects and improving the quality of life of subjects suffering from motor disorders.
11 Walking assistive apparatus for gait training patients and promotion exercise of the elderly
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This chapter presents authors development work on walking assistant exoskeletons for gait training of patients and promotion exercise of the elderly. The first exoskeleton is a whole leg assisting device using a special parallel link mechanism. For gait training of motor palsy patients, a weight bearing lifter was attached, and an impedance control was tuned by using frequency entertainment. For the elderly, a torque controller taken into account the dynamics of both a user and the apparatus with real time acceleration data is developed. The second exoskeleton is a whole body assisting suit was developed by adding arm assistance to the whole leg apparatus. By assisting not only legs but also swinging arms, an increased cerebral activity of all areas can be expected via rehabilitation with the whole body exoskeleton. Finally, we developed a close-fitting type exoskeleton assisting only ankle joint, which leads to a product RE-Gait® in 2016. By utilizing the structure of bi-articular muscle and physiological phenomenon of stretch reflex, the user's leg can be raised assisting only ankle joint. Experiments with by hemiplegic patients are enclosed, which show that abduct variation of the hip joint is decreased while the stride length is increased by using the device.
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Section 4 - Commercialization issues
Section 4 - Commercialization issues
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This section focuses on commercialization issues for wearable exoskeletons. For this, there are many business, management, finance and commercial details which need to be considered to ensure the research results achieved in developing technically innovative prototypes so that they can be taken forward to realize commercially viable products. Many of these relate to business decisions such as how the R&D team can be morphed into a commercialization team where instead of focusing on technical innovation, the attention turn to design for manufacturing, marketing and after sales activities. It is not the intention to focus on these issues here but instead to ensure the technical innovations will be able to satisfy regulatory requirements and hence have the potential for commercialization.
12 Regulatory issues for exoskeletons
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The chapter presents the safety standards which apply to wearable exoskeleton robots. Wearable robots are either regulated as machines or as medical electrical equipment. The machine regulations are formulated to comply with the Machinery Directive and the harmonised ISO 13482 safety standard has been recently published to present the safety requirements for personal care robots and which includes physical assistant robots. Medical exoskeletons are regulated under the Medical Device Directive and apply to patients needing medical help in carrying out human motion tasks. Both machine and medical regulations of wearable robots are described.
13 Test methods for exoskeletons—lessons learned from industrial and response robotics
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Exoskeletons are devices that can assist the human wearer's limbs to provide functional, normal, or amplified human capabilities. Research on exoskeletons has dramatically increased recently. However, measurements of these devices have yet to show long-term safety and other effects on humans. Safety standards now allow, through risk assessment, both manufacturing and wearable robots to be used, although performance standards for both systems are still lacking. Much can be learned from industrial and response robot safety and performance research and standards activities that can cross over into the exoskeleton arena. For example, ongoing research to develop standard test methods to assess performance of manufacturing robots and emergency response robots can inspire similar test methods for exoskeletons. This chapter first lists exoskeleton performance metrics and standards for collaborative industrial robots, response robots, and also physical assistance robots (i.e., exoskeletons). Then, it describes measurements ofjoint axis rotation location using an industrial robot simulating a human arm, as well as mobile manipulator and response robot test method developments that could also apply to exoskeletons. These methods and others are then integrated into recommendations for exoskeleton test methods.
14 Ekso Bionics
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Ekso Bionics designs and develops commercial exoskeletons for the healthcare, industrial, military, and consumer markets. Our exoskeleton systems work in conjunction with the operator to enhance strength, endurance, and mobility. These systems serve multiple markets and can be used both by persons with physical disabilities and by able-bodied users as well. We have sold, rented, or leased devices that enable individuals with neurological conditions affecting gait [e.g., spinal cord injury (SCI) or stroke] to rehabilitate and to walk again; allow industrial and construction workers to perform heavy duty work with increased efficiency and reduced strain; and permit soldiers to carry heavy loads for long distances while mitigating lower back, knee, and ankle injuries.
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Back Matter
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