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To overcome the limitations of a traditional soft hip exosuit directly driven by Bowden cables or winding belts at two points, in this article, we propose a new soft hip exosuit design concept based on series-wedge-structures for energy-efficient walking and running during daily activities for elderly individuals. The series-wedge-structure is designed to improve the comfort of the wearer–exosuit interface and to passively adapt to the user's body curvature, with no hindrance during movement. The design and function, including the series-wedge-structure belt, series elastic cable drive actuator, and control scheme, are described. The presented soft exosuit, which is lightweight (1.4 kg) and comfortable, provides assistive torque for hip flexion by folding series-wedge-structures driven by Bowden cables. The series-wedge-structure-based hip exosuit adopts single actuation coupled to the Bowden cable pull mechanism with a series elastic actuator to drive both hip flexions based on the out-of-phase nature of the human legs during walking and running. The exosuit performance test results show that the proposed exosuit improves the comfort of the wearer–exoskeleton interface by minimizing the shear force and maximizing the exosuit–skin interaction force contact area. Three healthy subjects walked at a fixed speed of 1.25 m/s and ran at a fixed speed of 2.2 m/s while wearing the proposed exosuit with/without assistance and without wearing the exosuit to evaluate the biomechanical and physiological effects of the proposed exosuit assistance on locomotion. The metabolic rate with exosuit assistance was reduced by 10.9% for walking and by 6.2% for running compared with not wearing the exosuit.

Exoskeletons have recently emerged as a promising technology that has the potential to allow people with limited mobility to utilize their joints and boost their strength. They have proved to be vital technologies in the medical field for helping patients navigate rehabilitation and daily activities of living. Not only have exoskeletons been designed for medical purposes, but they have also been integrated into the workplace for injury prevention and the military for added strength. The two reports presented in this portfolio offer different perspectives on the exoskeleton industry. The technical project focused on the design aspect of exoskeletons, as my group created our own novel soft upper exoskeleton design for Amyotrophic Lateral Sclerosis (ALS) patients. This project showcased the benefits of exoskeletons and a design that has the potential to aid patients with neuromuscular diseases. In contrast, my STS paper focused on the social implications of exoskeletons and their impact on the disability community and the workplace. This paper highlights the risks and adoption barriers of exoskeletons, including user concerns that have negatively impacted the commercialization of these technologies. Most commercially available upper limb exoskeletons in the medical field are rigid. Although they have produced promising results, they come with disadvantages. Typically, they are bulky, placing a heavy load on the users’ joints which can cause discomfort and additional risks. Soft exoskeletons have recently emerged, presenting an alternative to rigid devices that are more practical to implement into everyday life due to their malleable nature. The goal of our technical project was to create a soft upper limb exoskeleton for ALS patients to assist them with daily activities of living. ALS is a progressive neurodegenerative disease that affects the brain and spinal cord, resulting in the brain losing the ability to initiate and control muscle movements (The ALS Association, 2021). There is no cure for ALS patients to regain this ability, and many of them require joint support so we thought our design would be a suitable solution for their needs (National Institute of Neurological Disorders and Stroke, n.d.). Our main goal was to provide one degree of freedom in the elbow, specifically flexion/extension, to enable patients to raise and lower their forearm while lifting a lightweight object such as a book or glass of water. The device is fabricated with primarily soft components along with a Bowden cable actuator, Arduino Mega microcontroller, Inertial Measurement Unit (IMU) sensor, and an Electromyography (EMG) sensor. While our design is not ready to be commercially available, it has the potential to aid patients with neuromuscular diseases. Although exoskeletons have proved to restore limb functionality and have promising results with injury prevention, their use has been very limited in everyday life. There are many risks and challenges associated with designing exoskeletons due to the design and testing parameters weighing heavily on the targeted user. This makes it difficult to create a one-size-fits-all design due to the diversity of potential users and variability of intended tasks. As a result, there is a significant lack of standardized testing metrics, which have contributed to adoption barriers that have limited their use in the medical industry and workplace. My STS research paper explores the relationships between the designers of exoskeletons and their users to uncover the disconnect between them. Furthermore, I explored the development of exoskeletons over time, existing testing metrics, and design challenges. Through my research, I showed that exoskeletons are not meeting user needs, as supported by the findings of subjective analyses which have uncovered concerns with safety, ease of use, and cost due to a lack of testing metrics. As engineers it is crucial to recognize that the devices created can have unintended consequences that may negatively affect users. To prevent such consequences, it is essential to not only focus on the technical aspects but also on the social implications of the device. It was extremely beneficial to research user concerns about exoskeletons in the medical field while collaborating with my group to create our own soft upper limb exoskeleton design. Doing both at the same time allowed me to gain a comprehensive understanding of exoskeleton design and user concerns. Conducting the research of the adoption barriers enabled me to support my group with creating a soft upper limb exoskeleton that was able to achieve our technical goals, while also including features that users are looking for. We focused on making our design flexible, low cost, and easy to use based on the findings I highlighted in my STS paper. By addressing these issues, we were able to create an exoskeleton that has the potential to improve the quality of life for ALS patients. Working on both projects simultaneously has demonstrated the value in considering user concerns in the design process.

How are improvements in healthcare being pursued? How can a textile-based soft exoskeleton be used to maintain the activities of daily living (ADL) of patients with amyotrophic lateral sclerosis (ALS)? The creation of fully soft, upper-limb exoskeletons for rehabilitation of patients with neuromuscular disorders, such as ALS, is an emerging field of study and industry. Of the millions debilitated by these diseases, few can use such robots due to insufficient research. The research team designed a fully soft wearable robotic device that will be able to assist patients with ALS. With IMU and EMG sensors, a cable actuator, and computer programming, the team developed such a device. How do interest groups, advocacies, and others strive to lessen the racial disparities in healthcare in the United States? Public health agencies report health data and fund health services. To fight for health equity, advocacies in health, civil rights and racial justice have established community health centers, free clinics, and demonstration projects. Insurance companies, hospitals and professional associations have influenced such efforts, in part to protect their own interests. In the US, racial disparities in healthcare reflect systemic inequalities that contribute to comparable disparities in education, housing, and criminal justice. Despite improvements in some communities within the US there are still millions without the necessary healthcare they need.

This article presents a robotic needle positioning approach with a novel 4-DoF parallel positioner, two back-driveable 2-channel linear/rotational driver, and a machine–body interface. Being more compact and flexible, Ni–Ti alloy wire-based Bowden cable transmission is introduced to connect the positioner and the drivers. For this new mechanism, forward and inverse kinematics are derived, and the workspace is analyzed. The mechanism’s maximum incidence angle is 45 $^{\circ }$ , and the stroke of the slider is 41 mm. The structural size of one positioner is $\varnothing$ 70 mm × 45 mm. The compact size and lightweight of the positioner make it readily mountable on the skull or attached to other parts of the body. We fabricated a 3D printed proof-of-concept prototype of the system and tested its performance. The open-loop positioning accuracy of the slider and rotor is within $\pm$ 1 mm and from $-0.8^{\circ }$ to 1.5 $^{\circ }$ , respectively. The trajectory tracking error of the system is within 1.71 mm. The stiffness of the positioner in the x - and y -directions can be calculated as 9.03 and 11.91 N/mm, respectively. Finally, an image-guided navigation framework based on electromagnetic tracking demonstrates the feasibility of the proposed system on a phantom study.

Tendon-sheath actuators (TSAs), similar to Bowden cable-based series elastic actuators (SEAs), have a wide range of applications in robots. However, when applying them to manipulators, force sensors cannot be mounted due to limited space. Therefore, this paper proposes a new method for compliant control based on a dual encoder, and the existing transmission model was improved by considering the joint torque. To validate the proposed method, experimental setups composed of a motor, a tendon-sheath component, a robotic joint, force sensors, and position sensors are established. The transmission processes are interpreted clearly through a position control mode. Parameter identifications without external disturbance force are conducted to acquire the ideal transmission model, and the error value between the experiment data and the fitted curve is measured. The availability of the presented scheme is verified by compliant control experiments, including collision detection and hand guiding, and the frequency characteristics of the actuator are analyzed. The results show that the function can be realized without force and torque sensors during the whole process.

Although many lifting assist devices (LADs) have already been launched to the commercial market, and diverse types of LADs are under development with the recent advances in robotics technology, such LADs are not yet widely used in industrial fields. One of the main reason is the lack of versatility of fully passive type LADs and relatively high power consumption of fully active type LADs. In this study, our goal was to design a LAD that is not only more versatile than fully passive type LADs but also more energetically efficient than fully active type LADs. We analyzed the biomechanics of the lifting movement and developed a bi-articular elastic tendon mechanism based on our results. This conceptual mechanism was realized via a physical LAD operated by a series elastic actuator with a Bowden cable transmission. In this paper, we introduce our LAD and control strategy for assisting with lifting movements. Our LAD is capable of adjusting the output force behavior and assisting with lifting tasks at a low mechanical power consumption. Our preliminary testing suggests that our LAD reduces the muscle activation levels of the erector spinae and rectus abdominis muscles during a lifting task.

Few applications such as cutting shrubs and trees with prickles lead to damage to the hands while cutting it conventionally. The research has been undertaken for ease of rose plucking. A distance operated manipulator is designed and manufactured to overcome the issue of cutting roses by conventional way. The working of the tool is controlled by a lever operated mechanism. By a Bowden cable, the lever is connected to a brake caliper. The force applied by fingers at the lever is amplified at the point of application due to mechanical advantage. The end-effector consists of a gripper-cum-cutter. When the lever is operated, the stem of the rose is first gripped and then shearing of stem takes place. This unique feature of mechanism results into safe harvesting. Due to its simplest construction, it is a beneficial method. Trials have demonstrated the effective use of manipulator for rose plucking.

In this paper, a cable-driven series elastic actuator (SEA) is proposed to improve the flexibility of the exoskeleton robot. This actuator combines SEA and Bowden cable to realize the compliant actuation of exoskeleton joints, which has the contraction performance similar to biological muscles. The torsion spring based on the flexure hinge is introduced into the design of SEA’s elastic element to reduce the mass and structural complexity of SEA. Then, the dynamic model of the cable-driven SEA is established and the PD controller is designed which is optimized by the linear quadratic regulator method. Finally, the performance of the actuator is evaluated. The results of sinusoidal tracking experiments show that the tracking performance is better with a frequency of 0.5 Hz and a torque of 1 Nm, and the root-mean-squared error (RMSE) is 0.0588 Nm, while the RMSE is 0.1960 Nm in the experiments with a frequency of 1 Hz and a torque of 1.6 Nm.

Exoskeletons with a Bowden cable for power transmission have the advantages of a concentrated mass and flexible movement. However, their integrated motor is disturbed by the Bowden cable’s friction, which limits the performance of the force loading response. In this paper, we solve this problem by designing an outer-loop feedforward-feedback proportion-differentiation controller based on an inner loop disturbance observer. Firstly, the inner loop’s dynamic performance is equivalent to the designed nominal model using the proposed disturbance observer, which effectively compensates for the parameter perturbation and friction disturbance. Secondly, based on an analysis of the stability of the inner loop controller, we obtain the stability condition and discuss the influence of modeling errors on the inner loop’s dynamic performance. Thirdly, to avoid excessive noise from the force sensors being introduced into the designed disturbance observer, we propose the feedforward-feedback proportion-differentiation controller based on the nominal model and pole configuration, which improves the outer loop’s force loading performance. Experiments are conducted, which verify the effectiveness of the proposed methods.

Wearable robots assist individuals with sensorimotor impairment in daily life, or support industrial workers in physically demanding tasks. In such scenarios, low mass and compact design are crucial factors for device acceptance. Remote actuation systems (RAS) have emerged as a popular approach in wearable robots to reduce perceived weight and increase usability. Different RAS have been presented in the literature to accommodate for a wide range of applications and related design requirements. The push toward use of wearable robotics in out-of-the-lab applications in clinics, home environments, or industry created a shift in requirements for RAS. In this context, high durability, ergonomics, and simple maintenance gain in importance. However, these are only rarely considered and evaluated in research publications, despite being drivers for device abandonment by end-users. In this paper, we summarize existing approaches of RAS for wearable assistive technology in a literature review and compare advantages and disadvantages, focusing on specific evaluation criteria for out-of-the-lab applications to provide guidelines for the selection of RAS. Based on the gained insights, we present the development, optimization, and evaluation of a cable-based RAS for out-of-the-lab applications in a wearable assistive soft hand exoskeleton. The presented RAS features full wearability, high durability, high efficiency, and appealing design while fulfilling ergonomic criteria such as low mass and high wearing comfort. This work aims to support the transfer of RAS for wearable robotics from controlled lab environments to out-of-the-lab applications., Frontiers in Robotics and AI, 7, ISSN:2296-9144

Bovden poteg je pogosto uporabljen za prenos sil pri nosljivih robotih. Slaba stran takega prenosa je trenje, ki se pojavi ob njegovem upogibu. Z namenom zmanjšanja tega trenja smo razvili model, ki je opisan tekom diplomske naloge. S primerjavo meritev z in brez mehanske izboljšave smo ugotovili, da lahko z uporabo majhnih škripcev za preusmeritev Bovden potega opazno zmanjšamo silo trenja. Bowden cables are often used for transferring forces of wearable robots. The downside of such transfer is friction that appears upon bending of Bowden cables. We have developed a model to counteract such friction and have discussed it throughout this thesis. By comparing measurements with and without the mechanical solution we have determined, that when using pulleys to change the position of the Bowden cable, the friction force has been significantly reduced.

Robotic exoskeletons are a trending topic in both robotics and rehabilitation therapy. The research presented in this paper is a summary of robotic exoskeleton development and testing for a human hand, having application in motor rehabilitation treatment. The mechanical design of the robotic hand exoskeleton implements a novel asymmetric underactuated system and takes into consideration a number of advantages and disadvantages that arose in the literature in previous mechanical design, regarding hand exoskeleton design and also aspects related to the symmetric and asymmetric geometry and behavior of the biological hand. The technology used for the manufacturing and prototyping of the mechanical design is 3D printing. A comprehensive study of the exoskeleton has been done with and without the wearer’s hand in the exoskeleton, where multiple feedback sources are used to determine symmetric and asymmetric behaviors related to torque, position, trajectory, and laws of motion. Observations collected during the experimental testing proved to be valuable information in the field of augmenting the human body with robotic devices.

The mechanical assistance provided by exoskeletons could potentially replace, assist, or rehabilitate upper extremity function in patients with mild to moderate shoulder disability to perform activities of daily living. While many exoskeletons are “active” (e.g. motorized), mechanically passive exoskeletons may be a more practical and affordable solution to meet a growing clinical need for continuous, home-based movement assistance. In the current study, we designed, fabricated, and evaluated the performance of a wearable, passive, cable-driven shoulder exoskeleton (WPCSE) prototype. An innovative feature of the WPCSE is a modular spring-cam-wheel system that can be custom designed to compensate for any proportion of the shoulder elevation moment due to gravity over a large range of shoulder motion. The force produced by the spring-cam-wheel system is transmitted over the superior aspect of the shoulder to an arm cuff through a Bowden cable. The results from mechanical evaluation revealed that the modular spring-cam-wheel system could successfully produce an assistive positive shoulder elevation moment that matched the desired, theoretical moment. However, when measured from the physical WPCSE prototype, the moment was lower (up to 30%) during positive shoulder elevation and higher (up to 120%) during negative shoulder elevation due primarily to friction. Even so, our biomechanical evaluation showed that the WPCSE prototype reduced the root mean square (up to 35%) and peak (up to 33%) muscular activity, as measured by electromyography, of several muscles crossing the shoulder during shoulder elevation and horizontal adduction/abduction movements. These preliminary results suggest that our WPCSE may be suitable for providing movement assistance to people with shoulder disability.

The high energy cost of walking in individuals with cerebral palsy (CP) contributes significantly to reduced mobility and quality of life. The purpose of this study was to develop and clinically evaluate an untethered ankle exoskeleton with the ability to reduce the metabolic cost of walking in children and young adults with gait pathology from CP. We designed a battery-powered device consisting of an actuator-and-control module worn above the waist with a Bowden cable transmission used to provide torque to pulleys aligned with the ankle. Special consideration was made to minimize adding mass to the body, particularly distal portions of the lower-extremity. The exoskeleton provided plantar-flexor assistance during the mid-tolate stance phase, controlled using a real-time control algorithm and embedded sensors. We conducted a device feasibility and a pilot clinical evaluation study with five individuals with CP ages five through thirty years old. Participants completed an average of 130 minutes of exoskeleton-assisted walking practice. We observed a 19 ± 5% improvement in the metabolic cost of transport (p = 0.011) during walking with untethered exoskeleton assistance compared to how participants walked normally. These preliminary findings support the future investigation of powered ankle assistance for improving mobility in this patient population.

Ankle inversion–eversion compliance is an important feature of conventional prosthetic feet, and control of inversion, or roll, in active prostheses could improve balance for people with amputation. We designed a tethered ankle–foot prosthesis with two independently actuated toes that are coordinated to provide plantar-flexion and inversion–eversion torques. A Bowden cable tether provides series elasticity. The prosthesis is simple and lightweight, with a mass of 0.72 kg. Strain gauges on the toes measure torque with less than 1% root mean squared (RMS) error. Benchtop tests demonstrated a step response rise time of less than 33 ms, peak torques of 250 N $\cdot$ m in plantarflexion and $\pm$ 30 N $\cdot$ m in inversion–eversion, and peak power above 3 kW. The phase-limited closed-loop torque bandwidth is 20 Hz with a chirp from 10 to 90 N $\cdot$ m in plantarflexion, and 24 Hz with a chirp from $-$ 20 to 20 N $\cdot$ m in inversion. The system has low sensitivity to toe position disturbances at frequencies of up to 18 Hz. Walking trials with an amputee subject demonstrated RMS torque tracking errors of less than 5.1 N $\cdot$ m in plantarflexion and less than 1.5 N $\cdot$ m in inversion–eversion. These properties make the platform suitable for testing inversion-related prosthesis features and controllers in experiments with humans.

This letter presents the Passive Return Electro-Hydrostatic Actuator (PREHydrA), an actuator for use in wearable robotics. It eliminates conventional hydraulic systems’ fluid supply and valves, potentially making it lighter, more efficient, and simpler. It also avoids the configuration-dependent friction of Bowden cable transmissions. A physical port-based network model was created of the PREHydrA that predicts force tracking with a maximum error of about 4 N. Closed loop output force control was used in experiments to obtain a mean absolute tracking error below 4 N for force references from 300 N amplitude at 0.5 Hz to 20 N amplitude at 10 Hz. These forces, frequencies, and corresponding velocities (up to 0.47 m/s) demonstrate that the PREHydrA's performance is sufficient for many wearable applications.

Wearable robots can assist motor-impaired individuals in activities of daily living, but weight is paramount for usability. Proximally placed actuators and remote actuation systems (RAS) minimize weight on users' extremities. State-of-the-art RAS employ pneumatics, hydraulics, or Bowden cables, which all have considerable limitations. Here, we present a novel Bowden-cable-based bidirectional RAS featuring high power-to-mass and power-to-volume ratios, easily accessible components, and compact mechanical design. A rack-and-pinion mechanism reduces the force transmitted through the Bowden cables, permitting use of extremely compliant sheaths. The feed-forward friction compensation model, integrated bending angle sensor, and series elastic elements ensure accurate force control across all bending angles of the Bowden cables and the user's full range of motion. As a proof-of-concept, an RAS was designed for a hand exoskeleton with a maximal output force of 150 N. With a power-to-volume and a power-to-mass ratio of 127 kW/m3 and 56 W/kg at the output, and of 2.0 kW/m3 and 1.6 W/kg for the entire system, it outperforms other state-of-the-art RAS. With the implemented speed- and current-limiting, the system operates for at least 2 h continuously. It is water- and dustproof, meeting hygienic and practical demands. Importantly, this novel system can be scaled to the requirements of various applications in wearable robotics., IEEE Robotics and Automation Letters, 3 (3), ISSN:2377-3766

Bowden cables are frequently used as remote transmissions on wearable devices because of their light weight, simplicity, and flexibility of design. However, a Bowden cable suffers from inefficiency, nonlinear backlash, and cable tension variation due to the bending of the cable housing and friction losses, leading to deteriorating force control performance, and a wearers comfort level and augmentation effectiveness. In this paper, to enhance wearable device performance and to overcome the above drawbacks, we propose a novel high-performance, cable-drive module with rolling cable transmissions (RoCT) that can efficiently transmit motion and mechanical power from an input to an output via an inner cable/rope. The RoCT is compact, modular, lightweight, extremely stiff, highly backdrivable, and is freely rotatable and translatable during manipulation. It maintains the cable tension regardless of the transmission angle between the input and output. The configuration of the proposed tethered cable-drive module, the working principle of the rolling cable transmission, and its properties, are introduced. Mechanical designs based on the working principle are also provided. Finally, as one of the applications of the proposed module, a tethered ankle exoskeleton system and its experimental results demonstrating the properties of the proposed transmission are presented.

The presence of strong magnetic fields in the magnetic resonance imaging (MRI) environment limits the integration of robotic rehabilitation systems in the MRI process. The tendency to improve imaging quality by the amplification of magnetic field strength further tightens the bidirectional compatibility constraints on MRI-compatible rehabilitation devices. We present the design, control and characterization of MRI-VisAct– a low-cost, Bowden-cable-actuated rotary series viscoelastic actuator that satisfies the bidirectional compatibility requirements to the maximum extent. Components of MRI-VisAct that are placed in the magnet room are built using nonconductive, diamagnetic MRI-compatible materials, while ferromagnetic or paramagnetic components are placed in the control room, located outside the MRI room. Power and data transmission are achieved through Bowden cables and fibre optics, respectively. This arrangement ensures that neuroimaging artefacts are minimized, while eliminating safety hazards, and device performance is not affected by the magnetic field. MRI-VisAct works under closed-loop torque control enabled through series viscoelastic actuation. MRI-VisAct is fully customizable; it can serve as a building block of higher-degrees-of-freedom MRI-compatible robotic devices.

Weight, size and torque control for hand exoskeleton robots are challenging due to lack of small and compact bidirectional torque actuators. In this paper, an asymmetric Bowden-cable-driven series elastic actuator (ABLE-SEA) for hand exoskeleton robots was proposed based on the fact that the required torques for finger movements are asymmetric. Compared to series elastic actuator and transmission system that were designed separately, the elastic elements of ABLESEA were placed in transmission parts to connect series elastic actuator with transmission system, which makes system compact. ABLE-SEA is 71 mm × 19.5mm × 20mm in dimension and weighs 30g except motor which is placed remotely. The dynamic model of ABLE-SEA was established, and feedback proportional-derivative (PD) control plus a feed-forward term was used to track the reference torque for the ABLE-SEA. The reference torque tracking test at different frequencies was performed at the developed prototype. Meanwhile, the peak torque of ABLE-SEA was tested. The experimental results verified that the torque bandwidth of the proposed series elastic actuator could reach 4Hz, and the peak torque of ABLE-SEA could reach 0.3Nm, which meet the design requirement.

The research and development of wearable robotic devices has been accelerated by off-board control and actuation systems. While off-board robotic actuation systems provide many benefits, the impedance at the robotic joint is often high. High joint impedance is undesirable for wearable devices like exoskeletons, as the user is unable to move their joint without actively controlled motion from the motors. We propose that the impedance can be reduced substantially in off-board robotic actuation systems by minimizing the reflected inertia from the motor. We have developed a model and optimization-based methodology for selecting a motor and set of mechanical design parameters that minimize reflected inertia. This methodology was implemented in the design of an off-board knee exoskeleton as a case study. A grey-box model was developed that incorporates biomechanical knee trajectories, an experimentally determined human-device interface stiffness model, Bowden cable stiffness and friction, and a motor model. A constrained optimization routine was developed that uses the model and a library of 157 candidate servo motors to select the actuator and mechanical design parameters that minimize reflected inertia at the exoskeleton joint. We found that 86 of the motors were able to carry out the necessary torque-velocity trajectories to achieve the prescribed exoskeleton joint torques and limb motions. The optimal motor was the Kollmorgen C133A - one of the largest in the library of candidate servo motors and required a 2.25 cm actuator pulley at the knee joint and a 17.5 cm cable sheave at the motor output. This methodology can be adapted by exoskeleton designers to develop more backdriveable exoskeletons and improve experimental capabilities. All code developed for the case study is open-source and freely available online.

Soft exosuits have advantages over their rigid counterparts in terms of portability, transparency and ergonomics. Our previous work has shown that a soft, fabric-based exosuit, actuated by an electric motor and a Bowden cable, reduced the muscular effort of the user when flexing the elbow. This previous exosuit used a gravity compensation algorithm with the assumption that the shoulder was adducted at the trunk. In this investigation, the shoulder elevation angle was incorporated into the gravity compensation control via inertial measurement units (IMUs). We assessed our updated gravity compensation model with four healthy, male subjects (age: $26.2 \pm 1.19$ years) who followed an elbow flexion reference trajectory which reached three amplitudes $(25^{\circ}, 50^{\circ}, 75^{\circ})$ and was repeated at three shoulder angles $(25^{\circ}, 50^{\circ}, 75^{\circ})$. To assess the performance of the exosuit; the smoothness, tracking accuracy and muscle activity were investigated during each motion. We found a reduction of biceps brachii activation (24.3%) in the powered condition compared to the unpowered condition. In addition, there was an improvement in kinematic smoothness (0.83%) and a reduction of tracking accuracy (26.5%) in the powered condition with respect to the unpowered condition. We can conclude that the updated gravity compensation algorithm has increased the number of supported movements by considering the shoulder elevation, which has improved the usability of the device.

Back injuries are the most prevalent work-related musculoskeletal disorders and represent a major cause of disability. Although innovations in wearable robots aim to alleviate this hazard, the majority of existing exoskeletons are obtrusive because the rigid linkage design limits natural movement, thus causing ergonomic risk. Moreover, these existing systems are typically only suitable for one type of movement assistance, not ubiquitous for a wide variety of activities. To fill in this gap, this paper presents a new wearable robot design approach continuum soft exoskeleton. This spine-inspired wearable robot is unobtrusive and assists both squat and stoops while not impeding walking motion. To tackle the challenge of the unique anatomy of spine that is inappropriate to be simplified as a single degree of freedom joint, our robot is conformal to human anatomy and it can reduce multiple types of forces along the human spine such as the spinae muscle force, shear, and compression force of the lumbar vertebrae. We derived kinematics and kinetics models of this mechanism and established an analytical biomechanics model of human-robot interaction. Quantitative analysis of disc compression force, disc shear force and muscle force was performed in simulation. We further developed a virtual impedance control strategy to deliver force control and compensate hysteresis of Bowden cable transmission. The feasibility of the prototype was experimentally tested on three healthy subjects. The root mean square error of force tracking is 6.63 N (3.3 % of the 200N peak force) and it demonstrated that it can actively control the stiffness to the desired value. This continuum soft exoskeleton represents a feasible solution with the potential to reduce back pain for multiple activities and multiple forces along the human spine., 8 pages, 13 figures

This paper presents the development and human interaction evaluation of a Bowden cable based wearable fingertip tactile display. This device is designed to be used in the field of virtual reality and teleoperation to render different types of tactile sensations such as grip force, slipping, roughness and softness through delivering normal force, skin stretch, tangential movement and vibration indication to the user. This paper evaluates the proposed device’s capability in delivering individual taxel actuation through user testing. A four taxel actuation system fixed to a mild steel skeleton is covered in silicone rubber to ensure wearer comfort. A secondary mechanism is developed to provide sliding and lateral skin stretch sensation to the user. In addition, an 8 mm diameter piezo vibration motor is used to deliver vibration to indicate slipping to the user. The force feedback system consist of four independently operable taxels positioned at 2mm center to center distance on the fingertip. Each taxel was actuated via a Bowden cable connected to a geared DC motor, mounted on a lower arm worn sleeve. A taxel discrimination experiment was done to validate human discrimination ability of each taxel and the results showed that a healthy human can distinguish each taxel with 87.45 % mean accuracy.

The exoskeleton of the upper limb is an external parallel kinematic chain to the human arm. The device is designed to apply a specific torque of interaction to the human body resulting from bilateral teleoperation or rehabilitation. Its task is to work comfortably with the human arm. This paper presents the structure of the developed device and the control system of its joints. The construction of the joints’ drive system was performed based on the Bowden cable transmission. Based on the Bowden cable flexibility, it is possible to control the generated drive torque following the serial elastic actuator concept. The article presents joint control methods minimizing the influence of friction in the closed-loop Bowden cable conduit system. We also present the methods of estimating the torque of interaction with the operator based on the ExoArm 7-DOF exoskeleton dynamics model.

Enabling individuals who are living with reduced mobility of the hand to utilize portable exoskeletons at home has the potential to deliver rehabilitation therapies with a greater intensity and relevance to activities of daily living. Various hand exoskeleton designs have been explored in the past, however, devices have remained nonportable and cumbersome for the intended users. Here we investigate a remote actuation system for wearable hand exoskeletons, which moves weight from the weakened limb to the shoulders, reducing the burden on the user and improving portability. A push-pull Bowden cable was used to transmit actuator forces from a backpack to the hand with strict attention paid to total system weight, size, and the needs of the target population. We present the design and integration of this system into a previously presented hand exoskeleton, as well as its characterization. Integration of remote actuation reduced the exoskeleton weight by 56% to 113g without adverse effects to functionality. Total actuation system weight was kept to 754g. The loss of positional accuracy inherent with Bowden cable transmissions was compensated for through closed loop positional control of the transmission output. The achieved weight reduction makes hand exoskeletons more suitable to the intended user, which will permit the study of their effectiveness in providing long duration, high intensity, and targeted rehabilitation as well as functional assistance.

This paper presents the development of a low-cost Autonomous Emergency Braking System (AEBS) that can assist the driver or take over the electric car prototype for slowing down and breaking the car at the low-speed condition. An Actuator of AEBS is selected from DC motor that widely found on the market. The proposed AEBS is placed under the hood of the car. The AEBS will pull the brake pedal by using a Bowden cable. Ultrasonic sensor will be used for measuring the distance between the electric car and obstacle. On-off control will be developed for controlling the AEBS in breaking the electric car when the obstacle is approaching. After the AEBS prototype has been built, it will be employed in the electric car and tested for the automatic braking system. Based on the test results, the proposed AEBS can slow down and brake the car before colliding with the obstacle. The AEBS system will be activated when the distance between the car and the obstacle is less than 3.6 $\mathbf{m}$ . Based on the test result, AEBS can slow down and brake the electric car before colliding with the obstacle.

Currently, wrist passive stiffness and active range of motion, two clinically relevant properties, are assessed using devices designed for rehabilitation. As a result, these devices do not have sufficient torque output and range of motion for complete wrist biomechanical assessment. To address these limitations, we are developing an actuation module specifically for assessing wrist biomechanical properties. Our device employs a serial kinematic exoskeletal architecture to directly interact with and measure wrist flexion/extension and radial/ulnar deviation. A Bowden cable-based actuation scheme, locating the motors off-board, was adopted for increased device range of motion and torque output compared with previous wrist exoskeletons. Additionally, the device was designed to incorporate a rotational elastic element at each joint, creating series elastic actuators, for accurate torque control and direct torque measurement. In this work, we present the design and demonstration of a 1-DOF module of the device, which can interact with a user’s wrist in flexion/extension, providing an important first step towards the control, evaluation, and application of the 2-DOF device.

This paper introduces an approach that robotizes an ankle-foot orthosis (AFO). In particular, toward post-stroke gait rehabilitation, we robotize a double-bar AFO, which is widely used in rehabilitation facilities, by newly designing a modular joint, a pneumatic actuator, and a Bowden cable force-transmission system. Our modular joint system, called the Modular Exoskeletal Joint (MEJ), has a hollow shaft for simple attachment to an AFO's pivot. We designed MEJ to compactly house an encoder that is built in a bearing in a pulley. We adopted Bowden cables to transmit contraction forces from an actuator to the MEJ. As an actuation scheme, we developed the Nested-cylinder Pneumatic Artificial Muscle (NcPAM) system. Even though PAMs are mechanically compliant and lightweight, they can still generate a large force. Therefore, they can provide an ideal actuation system for exoskeletal robots. The nested-cylinder in NcPAM houses a cable-tensioning spring to properly maintain small cable tension for passive movements and a cable stopper to connect the PAM and the cable for properly transmitting the large force generated by PAM. We show the ankle-joint trajectory tracking performances of this integrated system using iterative learning control.