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Abstract Background Walking and running are the most common means of locomotion in human daily life. People have made advances in developing separate exoskeletons to reduce the metabolic rate of walking or running. However, the combined requirements of overcoming the fundamental biomechanical differences between the two gaits and minimizing the met...
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... the average radius of the springs is 0.19 m, the average exoskeleton rotational stiffnesses are 40, 72, 108, 137 Nm rad −1 , within the range of hip joint quasi-stiffness during the late stance phase of walking [27]. The detailed component mass of the exoskeleton is presented in Table 1. ...Citations
... Despite this, reductions achieved by assisting the hip joint still appear to be lower than those achieved with ankle exoskeletons [9][10][11][12][13]. More research is needed to better understand the relationships between energetic benefits and assistance levels at the hip [6,[14][15][16]. ...
This study focused on designing and evaluating a bilateral semi-rigid hip exoskeleton. The exoskeleton assisted the hip joint, capitalizing on its proximity to the body’s center of mass. Unlike its rigid counterparts, the semi-rigid design permitted greater freedom of movement. A temporal force-tracking controller allowed us to prescribe torque profiles during walking. We ensured high accuracy by tuning control parameters and series elasticity. The evaluation involved experiments with ten participants across ten force profile conditions with different end-timings and peak magnitudes. Our findings revealed a trend of greater reductions in metabolic cost with assistance provided at later timings in stride and at greater magnitudes. Compared to walking with the exoskeleton powered off, the largest reduction in metabolic cost was 9.1%. This was achieved when providing assistance using an end-timing at 44.6% of the stride cycle and a peak magnitude of 0.11 Nm kg−1. None of the tested conditions reduced the metabolic cost compared to walking without the exoskeleton, highlighting the necessity for further enhancements, such as a lighter and more form-fitting design. The optimal end-timing aligns with findings from other soft hip exosuit devices, indicating a comparable interaction with this prototype to that observed in entirely soft exosuit prototypes.
... Previous research on exoskeleton has often assisted the lower limb joint that generates the greatest positive mechanical power during either the ground contact [3,6] or swing phases [7,8] of level-ground hopping and running. Positive rather than negative mechanical power is targeted because producing force from concentric muscle contractions is less efficient than from eccentric muscle contractions. ...
... Similarly, when running without exoskeletal assistance at 2.0-3.25 m s −1 , the MTUs surrounding the ankle, knee and hip joint account for 42-47%, 19-21% and 32-39% of the total positive power over a stride, respectively [9]. Thus, several passive-elastic exoskeletons have been designed to assist at the ankle joint during the ground contact phase of hopping and running [3,6,10] or at the hip joint during the swing phase of running [7,8]. For example, Farris and colleagues showed that hopping in place at 2.5 Hz with a passive, ankle-only exoskeleton with linear (LN) springs reduced metabolic power by 13% [3,4]. ...
... The hip joint also provides a large proportion (32-39%) of the total average positive power during the swing phase when running on level ground at 2.25-3.25 m s −1 but does not significantly contribute to positive power during the stance phase [9]. While previous research has shown that passive-elastic assistive devices can reduce the metabolic cost of running by 6.5-8% through hip flexion assistance during the swing phase using tension springs [7,8,29], a passive-elastic, full-leg exoskeleton that acts during the stance phase with compression springs may not significantly contribute to positive hip power. Therefore, minimizing the exoskeleton moment arm about the hip might allow the exoskeleton to assist the ankle and knee during the stance phase without interfering with hip joint mechanics. ...
Passive, full-leg exoskeletons that act in parallel with the legs can reduce the metabolic power of bouncing gaits like hopping. However, the magnitude of metabolic power reduction depends on the spring stiffness profile of the exoskeleton and is presumably affected by how users adapt their lower-limb joint mechanics. We determined the effects of using a passive, full-leg exoskeleton with degressive (DG), linear (LN) and progressive (PG) stiffness springs on lower-limb joint kinematics and kinetics during stationary, bilateral hopping at 2.4 Hz. We found that the use of a passive, full-leg exoskeleton primarily reduced the muscle-tendon units (MTUs) contribution to overall joint moment and power at the ankle, followed by the knee, due to the average exoskeleton moment arm around each joint. The greatest reductions occurred with DG springs, followed by LN and PG stiffness springs, probably due to differences in elastic energy return. Moreover, the relative distribution of positive joint power remained unchanged when using a passive, full-leg exoskeleton compared with unassisted hopping. Passive, full-leg exoskeletons simultaneously assist multiple lower-limb joints and future assistive devices should consider the effects of spring stiffness profile in their design.
... Compared with active variable stiffness actuators, this stiffness adjustment method greatly reduces the weight of the joint and can be well applied to the lightweight requirements of SRLs worn on the human body [9]. According to the driving mode, pVSJ can be classified into an active pVSJ [10][11][12][13] and a passive pVSJ [14][15][16]. There are more studies on human-robot interaction safety and torque control in the active pVSJ. ...
... Passive pVSJ is mainly applied in fields such as assistance and gravity compensation. In assistance, the pVSJ is used to adapt to [16] or imitate [15] the movement of a certain part of the human body. For example, the joint stiffness increases to provide support assistance when the upper limb of the human body enters the support phase. ...
Supernumerary robotic limbs(SRLs) are new type of wearable robots. In order to achieve safe and stable operations for the SRLs, a tendon-driven passive variable stiffness joint(pVSJ) integrated into the shoulder joint of the SRLs is presented, which can output different stiffness and improve the safety of human-robot interaction. The stiffness change of the pVSJ is achieved by winding a tendon around pulleys to drive the flexible element to stretch. In the non-operating state, the stiffness characteristics of the pVSJ can be changed by adjusting the pre-tension of the flexible element, the winding method of the tendon, and replacing the flexible element. A mathematical model is established for the tendon-driven pVSJ to reveal its stiffness characteristics. The model is verified through quasi-static experiments. The experimental results show that there is an obvious hysteresis phenomenon during low torque loading. The hysteresis range is 20.8%-32.5%. The angular range of the loading hysteresis of the pVSJ is negatively related to the spring preload, spring stiffness, the number of working branches, and it is positively related to the rope diameter. The unloading process basically conformed to the theoretical model, with a maximum relative error of 3.4%. Therefore, the exact stiffness output can be achieved by first increasing and then decreasing the joint torque to reach the target torque.
... In addition, Eqs. (24) and (25) were verified by simulation. ...
... Furthermore, the results of this study may be useful in the design of an unpowered hip exoskeleton 24, 25 that uses the spring stiffness. This device, like the model in this study, exerts flexion torque during hip extension and extension torque during hip flexion due to the spring stiffness 24,25 . However, studies have been limited to younger adults, and it is unclear whether this device can be adapted for rehabilitation of the elderly to prevent falls. ...
Excessive hip flexion torque to prioritize leg swings in the elderly is likely to be a factor that reduces their propulsive force and gait stability, but the mechanism is not clear. To understand the mechanism, we investigated how propulsive force, hip flexion torque, and margin of stability (MoS) change when only the hip spring stiffness is increased without changing the walking speed in the simple walking model, and verified whether the relationship holds in human walking. The results showed that at walking speeds between 0.50 and 1.75 m/s, increasing hip spring stiffness increased hip flexion torque and decreased the propulsive force and MoS in both the model and human walking. Furthermore, it was found that the increase in hip flexion torque was explained by the increase in spring stiffness, and the decreases in the propulsive force and MoS were explained by the increase in step frequency associated with the increase in spring stiffness. Therefore, the increase in hip flexion torque likely decreased the propulsive force and MoS, and this mechanism was explained by the intervening hip spring stiffness. Our findings may help in the control design of walking assistance devices, and in improving our understanding of elderly walking strategies.
... Furthermore, there has not been much advancement in heavy-load-carrying techniques since Antiquity, including holding objects in the hands, hanging packs from the shoulders, and balancing burdens on the head [3][4][5]. Different powered exoskeletons [6][7][8][9][10][11][12] and unpowered exoskeletons [13][14][15][16][17][18] have also been created as a result of technological advancement. The most comprehensive and cost-effective method is still a backpack. ...
Backpack transportation is everywhere in daily life. Suspended-load backpacks (SUSBs) based on forced vibration have attracted lots of attention because of their ability to effectively reduce the cost on the body during motion. The smaller the natural frequency of SUSBs, the better the cost reduction. The natural frequency is determined by the elastic components of SUSBs. It is currently common to use rubber ropes and pulleys as elastic components. In the first part of this paper, we propose a pre-compression design for SUSBs, which has a simple structure and breaks through the limitation of rubber material. To make the natural frequency small enough, rubber ropes and compression springs require sufficient space. This leads to the current SUSBs being large and, therefore, not suitable for children to carry. Inspired by biology, here we propose a new design strategy of pre-rotation with pre-rotation spiral springs as elastic components. The pre-rotation design not only has the advantages of avoiding the inconvenience of material aging and the ability to adjust the downward sliding distance of the backpack but also greatly saves the space occupied by the elastic components, which can be adopted by small SUSBs. We have developed a theoretical model of the pre-rotation SUSBs and experimentally confirmed the performance of the pre-rotation SUSBs. This work provides a unique design approach for small SUSBs and small suspended-load devices. And the relative motion between the components inside the SUSB has a huge potential to be used by triboelectric nanogenerators for energy scavenging.
... Despite these encouraging simulation findings, the majority of exoskeletons developed to date have primarily focused on providing assistance in the sagittal plane, neglecting frontal hip assistance [7][8][9][10][11][12][13][14][15]. Notably, no single study has experimentally demonstrated a metabolic reduction with frontal hip assistance [16,17]. ...
Background: During walking, humans exert a substantial hip abduction moment to maintain balance and prevent pelvic drop. This significant torque requirement suggests that assisting the frontal hip muscles could be a promising strategy to reduce the energy expenditure associated with walking. A previous musculoskeletal simulation study also predicted that providing hip abduction assistance through an exoskeleton could potentially result in a large reduction in whole-body metabolic rate. However, to date, no study has experimentally assessed the metabolic cost of walking with frontal hip assistance.
Methods: In this case study involving a single subject (N = 1), a tethered hip exoskeleton emulator was used to assess the feasibility of reducing metabolic expenditure through frontal-plane hip assistance. Human-in-the-loop optimization was conducted separately under torque and position control to determine energetically optimal assistance parameters for each control scheme.
Results: The optimized profiles in both control schemes did not reduce metabolic rate compared to walking with assistance turned off. The optimal peak torque magnitude was found to be close to zero, suggesting that any hip abduction torque would increase metabolic rate. Both bio-inspired and simulation-inspired profiles substantially increased metabolic cost.
Conclusion: Frontal hip assistance does not appear to be promising in reducing the metabolic rate of walking. This could be attributed to the need for maintaining balance, as humans may refrain from relaxing certain muscles as a precaution against unexpected disturbances during walking. An investigation of different control architectures is needed to determine if frontal-plane hip assistance can yield successful results.
... Specifically, hip extensors (e.g., hamstrings, gluteus maximus) assist with the deceleration of the thigh during the swing phase of walking and accelerating at the beginning of stance; these muscles help stabilize the body to lower extremity forces [38,41,42]. The hip flexors (e.g., rectus femoris, iliopsoas, sartorius) actively progress the thigh forward during the swing phase and passively aid leg deceleration during the second half of stance [41,43]. Due to the importance of the hip for walking, using a passive exoskeleton or exosuit to perturb the hip motion by adding a force that is not naturally produced by the body offers a promising avenue to induce adaptative changes. ...
Abstract Background Asymmetric walking gait impairs activities of daily living in neurological patient populations, increases their fall risk, and leads to comorbidities. Accessible, long-term rehabilitation methods are needed to help neurological patients restore symmetrical walking patterns. This study aimed to determine if a passive unilateral hip exosuit can modify an induced asymmetric walking gait pattern. We hypothesized that a passive hip exosuit would diminish initial- and post-split-belt treadmill walking after-effects in healthy young adults. Methods We divided 15 healthy young adults evenly between three experimental groups that each completed a baseline trial, an adaptation period with different interventions for each group, and a post-adaptation trial. To isolate the contribution of the exosuit we compared a group adapting to the exosuit and split-belt treadmill (Exo-Sb) to groups adapting to exosuit-only (Exo-only) and split-belt only (Sb-only) conditions. The independent variables step length, stance time, and swing time symmetry were analyzed across five timepoints (baseline, early- and late adaptation, and early- and late post-adaptation) using a 3 × 5 mixed ANOVA. Results We found significant interaction and time effects on step length, stance time and swing time symmetry. Sb-only produced increased step length asymmetry at early adaptation compared to baseline (p
... Researchers have designed different passive energy storage structures for unpowered exoskeletons. Zhou et al. designed a wearable hip joint exoskeleton, using 3-D printing technology to create waist and thigh braces to adapt to the irregular surface of the human body, setting springs in front of the hip joint, to recover negative mechanical energy and release the stored energy to assist hip flexion [4]. Ben-David et al. designed a knee joint exoskeleton, the passive energy storage structure is designed with a spring in the front of the knee joint to store up energy when the knee flexing and release mechanical energy when the knee extends, increasing the height of vertical jumps [5]. ...
... Taking the existing passive lower extremity exoskeletons as a reference, three auxiliary solutions for the passive lower extremity exoskeletons are pre-set in this paper, namely setting a tension spring on the front side of the hip joint [4], and setting a compression spring on the back side of the knee joint [17] and a tension spring on the back of the ankle joint [6]. The mathematical models of each auxiliary scheme are built in OpenSim with the musculoskeletal system. ...
... This result is similar to the effect of most current experimental ankle plantarflexion devices [27][28][29][30]. However, it also be found that the hip assist scheme differs from most current experimental hip flexion devices [4,[31][32][33]. The major reason is that the metabolic base of weight-bearing walking is greater than that of natural walking. ...
This paper proposes the conceptual design method for a hybrid-actuated lower limb exoskeleton based on energy consumption simulation. Firstly, the human-machine coupling model is established in OpenSim based on the proposed three passive assistance schemes. On this basis, the method of simulating muscle driving is used to find out the scheme that can reduce the metabolic rate the most with 3 passive springs models. Then, an active-passive cooperative control strategy is designed based on the finite state machine to coordinate the operation of the power mechanism and the passive energy storage structure and improve the mobility of the wearer. In the end, a simulation experiment based on the human-machine coupled model with the addition of active actuation is proceeded to evaluate its assistance performance according to reducing metabolic rate. The results show that the average metabolic cost decreased by 7.2% with both spring and motor. The combination of passive energy storage structures with active actuators to help the wearer overcome the additional consumption of energy storage can further reduce the body's metabolic rate. The proposed conceptual design method can also be utilized to implement the rapid design of a hybrid-actuated lower limb exoskeleton.
... Gait joint kinematic changes were also present while wearing the exosuit, with more significant modifications after training. The exosuit loads potential energy during hip extension and returns it during flexion, assisting the subject during gait; as a result, changes in the hip joint angles were expected between the exosuit and no exosuit conditions [61]. The results support the purpose of the exosuit and enforced exploration training, showing an increase in maximum hip flexion between exosuit and no exosuit conditions during the swing phase ( Fig. 4(a),(d)). ...
Background: Ankle injuries can be detrimental due to their long-recovery times. A walking boot (WB) is the most prescribed treatment. However, they disrupt gait biomechanics, increasing the metabolic cost of walking and the risk of further injuries. Research question: Does the use of a hip exosuit minimize the adverse effects of wearing a WB, improving gait spatio-temporal parameters, and reducing energy expenditure? Methods: We investigated the effects of a passive hip exosuit and enforced exploration training in users wearing a WB. Subjects wore a WB to simulate the effects of ankle injuries during recovery. Results: The results indicate the benefits of wearing the hip exosuit and training. Metabolic cost reductions of 6.2 ± 1.5 % (p < 0.001) between the post-training and pre-training and 3.5 ± 2.8 % (p = 0.03) between the post-training and no exosuit conditions were found. Training with the exosuit resulted in positive gait modifications associated with gait retraining in patients with ankle injuries. The effects of enforced exploration training in gait kinematics wearing the exosuit resulted in an increased maximum hip flexion of 6.04 ± 3.56° (p = 0.01) and 6.59 ± 5.16° (p = 0.03) for the boot and free leg, respectively, compared to not wearing the exosuit. Spatiotemporal parameter modifications were adopted after training, resulting in metabolic reductions. Some subjects varied their step frequency, while others their step length and width. Significance: The outcomes from this study show the potential benefits that hip exosuits can have in clinical sports rehabilitation of ankle injuries wearing a WB.
... Recently, there has been a tremendous amount of effort devoted to developing assistive systems to reduce the metabolic cost of walking [4][5][6][7][8][9][10][11][12], to facilitate the carrying of objects [13,14], etc. There are active [4][5][6] and passive [7][8][9][10][11][12] walking assistance systems that are classified depending on the requirements for external power. ...
... Recently, there has been a tremendous amount of effort devoted to developing assistive systems to reduce the metabolic cost of walking [4][5][6][7][8][9][10][11][12], to facilitate the carrying of objects [13,14], etc. There are active [4][5][6] and passive [7][8][9][10][11][12] walking assistance systems that are classified depending on the requirements for external power. Whereas passive devices store and release energy using elastic elements, active devices use electric motors, hydraulic, pneumatics systems, etc., to generate forces and moments. ...
... Panizzolo et al. investigated a walking assistance system around the hip joint similar to the proposed optimal solution [8]. Zhou et al. developed a passive walking assistance system that assists the hip joint during walking and running [9]. The reason why walking assistance devices are concentrated on the ankle and hip joints to reduce the metabolic cost of walking is that the ankle and hip joints account for the largest share of the energy consumption during a gait cycle [22]. ...
Walking is a fundamental movement in daily life; however, many factors affect walking that may reduce the mobility of the people. Walking assistance devices can help with gaining mobility back for people who suffer from walking problems. In the present study, a computational method to determine the location and stiffness of the assistive walking systems was developed. The human walking model was created by using nine rigid bodies and eight revolute joints connecting them in the sagittal plane. The walking assistance system was considered as a tension spring with both ends attached to the human walking model. A coordinate system was defined along the distal–proximal direction of the human body. The position of the walking assistance system was determined by using four design variables, and the optimal position of the assistive walking system to reduce the total positive joint energy was found around the hip joint at a walking speed of 1.3 m/s. Hip joint moment and power were significantly affected by the walking assistance system, and the total positive joint energy was reduced by 8.8%. Because walking speed significantly affects walking kinematics and kinetics, the effect of walking speed on the optimal walking assistance device was investigated. The position of the device was kept the same, and the optimal stiffness and free length of the spring were found at different walking speeds. Two different cases were considered: a speed-specific design in which stiffness characteristics were separately optimized for each speed and a general design in which stiffness characteristics were optimized by considering all walking speeds. It was found that, in both cases, hip joint moment and power significantly reduced, and the speed-specific design produced a slightly larger reduction in total joint energy. The performance of the walking assistance systems in both cases were found to be higher at faster walking speeds.
