Design and Preliminary Validation of a Lower Limb Exoskeleton With Compact and Modular Actuation

Research on lower limb exoskeleton (LLE) for rehabilitation have developed rapidly to meet the need of the population with neurologic injuries. LLEs for rehabilitation include therapeutic LLEs that aim to restore walking ability for patients, and assistive LLEs that offer support on activities in daily life. A substantial part of them can serve both purposes. However, these devices are yet to reach the final goal of performing human-machine joint movement agilely and smartly. Control strategy plays an important role in achieving their designed goal. At present, control strategies face three major challenges: how to detect human intention, how to do motion control with given intentions, and how to optimize control parameters to suit different individuals. As a contribution, this paper offers an overview on the state-of-the-art control strategies for rehabilitation LLEs by classifying them into eight categories, each of which is presented with a technical summary and tabulated information of representative papers. Moreover, current approaches addressing the three challenges are discussed in a macroscopic perspective. Finally, it has been explored which requirements the future control strategies should meet for maximizing the performance of rehabilitation LLEs.

Section: A Trajectory Trackingmentioning

confidence: 99%

Review on Control Strategies for Lower Limb Rehabilitation Exoskeletons

Cao²,

Zhu

2021

“…An overview of the technical data of the PEA is summarized in Table 4. The selection of the motor and the HD, the design of the SD and other technical data of the PEA were introduced in detail in [52]. Fig.…”

Section: Mechanical Design Of Peamentioning

confidence: 99%

“…It includes the exoskeleton pelvis, two PEAs for bilateral hip joints and mechanical hard stops to constrain the joint motion of the hip. The prototype development of the PEA-driven exoskeleton was comprehensively illustrated in [52]. Fig.…”

Section: Mechanical Design Of Peamentioning

confidence: 99%

“…Firstly, similar benchtop trials but with PEs of greater stiffnesses can be conducted. Secondly, we will further conduct clinical trials of paraplegic patients (with a complete loss in walking ability) walking with the assistance of the PEA-driven LLE, based on the successful preliminary experimental validation of this LLE without the spring attached in [52]. It is important to improve the system effectiveness of the PEA.…”

Section: Potential Improvement For the Proposed Peamentioning

confidence: 99%

See 1 more Smart Citation

Analysis, Design, and Preliminary Evaluation of a Parallel Elastic Actuator for Power-Efficient Walking Assistance

Guan

et al. 2020

Self Cite

This paper introduces the analysis, design and preliminary evaluation of a self-integrated parallel elastic actuator (PEA) with an electric motor and a flat spiral spring in parallel to drive the hip joint of lower limb exoskeletons for power-efficient walking assistance. Firstly, we quantitatively analyze the reason why the parallel elasticity (PE) placed at the sagittal hip joint can reduce the motor power requirement during walking assistance, which contributes to the theory of PEA development and application. The design of the PEA is then introduced in detail. The novelty of the design is that the actuator is reduced in size by integrating the spring into the motor, and the requirement of spring stiffness is significantly reduced by placing the spring directly parallel to the motor shaft. Furthermore, both the simulation based on dynamic modeling and benchtop experiment are conducted preliminarily to evaluate the performance of the PEA with nine spring stiffnesses in a range from 0-5.29 mN•m/rad regarding two indexes including the average and maximum positive electrical power of the motor. Their results show that the two indexes become smaller when the PE is attached and decrease as the spring stiffness increases. When the PE with a stiffness of 5.29 mN•m/rad is attached, the actuator obtains the largest reduction rate of 11.99 and 16.84 % in the average (root mean square) and maximum positive electrical power of the motor in the simulation and 10.3 and 26.25 % in the experiment, respectively. Those results provide evidence for the applicability of the newly designed PEA in driving a lower limb exoskeleton with high power efficiency during walking assistance for paraplegic patients with complete loss in walking ability. INDEX TERMS Actuator design, compliant actuation, lower limb exoskeleton, parallel elastic actuator, power-efficient actuator. I. INTRODUCTION Traditional rigid actuators (RAs) (e.g. electric motors), as the key units of walking assistance devices such as lower limb exoskeletons (LLEs), consume a lot of power, leading to a high power requirement. An average power of nearly 600 W, for example, was required during level-ground walking at 1.3 m/s with the exoskeleton BLEEX actuated by motors [1]. Therefore, it is important to develop power-efficient actuators for walking assistance. The associate editor coordinating the review of this manuscript and approving it for publication was Yangmin Li .

“…These devices can help users practice repetitively and free physical therapists from heavy work [1]. In past decades, many kinds of wearable exoskeletons are designed to help patients rehabilitate from the jury [2,3,4]. As the exoskeleton is a typical human-machine interaction system, it is essential to design and develop control strategies to track the defined human gait safely and robustly.…”

Section: Introductionmentioning

confidence: 99%

Extended State Observer-Based Nonlinear Terminal Sliding Mode Control With Feedforward Compensation for Lower Extremity Exoskeleton

Long

Peng²

2022

This paper presents and experimentally demonstrates an extended state observer (ESO)based nonlinear terminal sliding mode control strategy with feedforward compensation (ESO-F-NTSMC) for lower extremity exoskeleton. Since the lower extremity exoskeleton (LEE) is a coupled humanexoskeleton coordination system, the internal or external disturbances and uncertainties affect its performance. A nonlinear terminal sliding mode control with feedforward compensation (F-NTSMC) is proposed to drive the lower extremity to shadow the target human gait trajectory. An ESO is employed to estimate the total disturbances including these caused by the chattering phenomenon in F-NTSMC. ESO-F-NTSMC can assure that the human gait trajectory tracking can converge to a bounded region smoothly and robustly. The phase identification-based human gait generation approach is also presented. The derivation process of the ESO-F-NTSMC is shown the and the Lyapunov-based stability analysis is conducted. To illustrate the proposed method's effectiveness, experiments are performed on three human subjects walking on the floor at a natural speed. The results demonstrate that the exoskeleton can actively collaborate with the user under the proposed method.