Prototype for Knee-load Relief through Ischiatic Support

Objective: The objective of this work was to develop a passive exoskeleton prototype for the relief of knee-load employing ischiatic body weight support. Methods and materials: A functional prototype was developed and tested with three volunteers to analyze its potential effectiveness and effects on gait kinematics. The performance of the prototype was assessed using motion capture and pressure mapping systems, and a testing bench for the study of ischiatic body weight. Results and discussion: The results of the tests indicate that the prototype allows reducing the load supported by the knees and does not have a significant effect on the kinematics of the hip and knee joints. The process allowed the designers to identify possibilities of improvement mainly on reducing the restrictions imposed by the prototype to the motion of the ankles, especially on the midstance of the support phase. Conclusions: The passive exoskeleton prototype developed for ischiatic body weight support allows setting different percentages of knee-load relief. The prototype does not have a significant effect on the kinematics of the hip and knee joints. Nevertheless, improvements must be performed to reduce the restrictions to the motion of the ankles.

Design, Manufacturing, and Control of a Pneumatic-Driven Passive Robotic Gait Training System for Muscle-Weakness in a Lower Limb

We designed and manufactured a pneumatic-driven robotic passive gait training system (PRPGTS), providing the functions of body-weight support, postural support, and gait orthosis for patients who suffer from weakened lower limbs. The PRPGTS was designed as a soft-joint gait training rehabilitation system. The soft joints provide passive safety for patients. The PRPGTS features three subsystems: a pneumatic body weight support system, a pneumatic postural support system, and a pneumatic gait orthosis system. The dynamic behavior of these three subsystems are all involved in the PRPGTS, causing an extremely complicated dynamic behavior; therefore, this paper applies five individual interval type-2 fuzzy sliding controllers (IT2FSC) to compensate for the system uncertainties and disturbances in the PRGTS. The IT2FSCs can provide accurate and correct positional trajectories under passive safety protection. The feasibility of weight reduction and gait training with the PRPGTS using the IT2FSCs is demonstrated with a healthy person, and the experimental results show that the PRPGTS is stable and provides a high-trajectory tracking performance.

Economical and preferred walking speed using body weight support apparatus with a spring-like characteristics

Background A specific walking speed minimizing the U-shaped relationship between energy cost of transport per unit distance (CoT) and speed is called economical speed (ES). To investigate the effects of reduced body weight on the ES, we installed a body weight support (BWS) apparatus with a spring-like characteristics. We also examined whether the 'calculated' ES was equivalent to the 'preferred' walking speed (PWS) with 30% BWS. Methods We measured oxygen uptake and carbon dioxide output to calculate CoT values at seven treadmill walking speeds (0.67–2.00 m s− 1) in 40 healthy young males under normal walking (NW) and BWS. The PWS was determined under both conditions on a different day. Results A spring-like behavior of our BWS apparatus reduced the CoT values at 1.56, 1.78, and 2.00 m s− 1. The ES with BWS (1.61 ± 0.11 m s− 1) was faster than NW condition (1.39 ± 0.06 m s− 1). A Bland-Altman analysis indicated that there were no systematic biases between ES and PWS in both conditions. Conclusions The use of BWS apparatus with a spring-like behavior reduced the CoT values at faster walking speeds, resulting in the faster ES with 30% BWS compared to NW. Since the ES was equivalent to the PWS in both conditions, the PWS could be mainly determined by the metabolic minimization in healthy young males. This result also derives that the PWS can be a substitutable index of the individual ES in these populations.