Mechatronic aided walk--a comparative study.

Seiciu, Petre Lucian ; Laurian, Tiberiu ; Filipoiu, Ioan Dan 等

1. INTRODUCTION

Bipedal walking is one of the most important features of humans. The vital importance of the feet is obvious: no feet, no gait. The poorer the functional performance of the feet, the lower the functional performance of the gait. The feet's architectural design and its consequent biomechanical function is responsible for our distinctive erect manner of gait--walking on two feet with a stride (Font-Llagunes & Kovecses 2009; Lei et al. 2006).

The designing and assembling of the mechatronic system for assisting the rehabilitation of locomotory disabled patients (MS) was presented in several papers (Filipoiu et al., 2007; Seiciu et al., 2008; Seiciu et al., 2009). The experiments made on MS lead the authors to the conclusion that a more thorough study of the walking is needed in order to improve the MS functioning (Seiciu et al., 2008). The main goal is an improved design of the feet driving system, since this is the most complex feature of the MS, mainly due to the feet complex movement.

The present study shows the experimental measurements using the same subjects in normal walking (NW) and in mechanically aided walking (MAW). It is, emphasized that changes at the feet level have consequences far distal, from ankle to hip in all kinematic parameters.

2. MATERIALS AND METHODS

One male subject (age 24 years; height 183 cm; weight 80 Kg) took part in this experiment. The subject performed several walking trials. Two walking situations were studied: NW using a conventional treadmill and MAW using the MS. Each trial took 20 seconds.

Kinematic data were collected at 200Hz using Biometrics goniometers (Biometrics Ltd, Gwent, United Kingdom) placed at lower limb joints (ankle, knee and hip--see fig. 1). Raw kinematic data was filtered by applying a 50 Hz low-pass filter.

One angular displacement (Flexion-Extension) was recorded for the ankle and the knee and two angular displacements (Flexion-Extension and Abduction-Adduction) were recorded for the hip joint. Angular velocities and accelerations were derived from joint displacements (Seiciu, 2009; Hardy 1987). The knee abduction-adduction measurements were excepted because of lack of mobility while using the MS.

[FIGURE 1 OMITTED]

3. RESULTS

From the kinematic point of view there are many similarities and a few differences between NW and MAW.

The similarities between NW and MAW are:

* The knee flexion-extension measurements (fig. 2a) have almost the same amplitude and phase.

* The hip abduction-adduction measurements (fig. 2d) have almost the same amplitude and phase.

The differences between NW and MAW are:

* The hip flexion-extension measurements (fig. 2c) present a significant amplitude variation.

* The angular movement amplitude for flexion-extension is variable for all MAW measurements while, as expected, the NW angular amplitude is almost constant (fig. 2a, 2b and 2c).

* The ankle flexion-extension measurements (fig. 2b) present the largest variation both in amplitude and phase.

The authors propose a new method to assess the gait quality. This method implies the following:

* The differences between NW and MAW can be observed and measured.

* The differences are observable for all the leg joints. This paper concentrates on the gait differences at the hip joint (as seen in fig. 2d).

* The analyzed differences are defined by: angle deviation ([sigma][phi]) and pitch deviation ([sigma]t). The angle deviation can have positive or negative values. The pitch deviation can be in advance or delay.

[FIGURE 2 OMITTED]

* For an accurate analysis these deviations are calculated for each step (denoted with index n). For improved accuracy the calculation can be done for a large number of steps.

With these values, we can determine the absolute deviations:

--Absolute pitch deviation (APD):

[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] (1)

--Absolute pitch deviation (AAD):

[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] (2)

where n is the number of measured gait cycles and [[phi].sub.max] is the maximum angular amplitude of the joint.

APD is calculated by taking into account the pitch deviations for all gait cycles, while AAD is calculated by taking into account the angular deviation at the same moment relative to each gait cycle.

For a more profound analysis one can use the means of non-linear analysis such as the Lyapunov exponent or the system entropy. The most used method is the calculation of the Lyapunov exponent, which requires a large number of cycles and therefore being more time consuming.

The method presented in this paper implies the calculation of angular and pitch deviations and is a fast way of assessing locomotory disorders. The required data is obtained for two types of gait: normal walking (NW) and mechanical aided walk (MAW). This method does not require the use of a complicated mathematical model and is not time consuming.

4. CONCLUSION

The mechatronic system is fit for locomotory rehabilitation though several improvements have to be done in order to achieve a MAW similar to NW.

In NW measurements the variability of joint angular displacement amplitude was significantly greater than in MAW case. The lack of mobility at metatarsophalangeal articulations, in MAW, leads to increased amplitude in ankle flexion-extension.

Understanding how mechanical aided walk influences gait parameters and postural stability is helpful mainly in locomotory rehabilitation (gait disorder and joint degeneration prevention) but also in other connected domains such as high performance sport.

This method does not exclude the non-linear analysis which is necessary for more detailed studies.

This is only a preliminary study, further measurements performed on numerous subjects being intended for the future.

5. REFERENCES

Font-Llagunes, J.M. & Kovecses, J., (2009). Dynamics and energetics of a class of bipedal walking systems. Mechanism and Machine Theory, 44(11), 1999-2019

Filipoiu, I. D.; Seiciu P. L.; Laurian, T. & Carutasu, N. (2007). SIMESIM--The Mechatronic System For Neuro-Motor Disabled Persons, In.: DAAM International Scientific Book 2007, Katalinic, B. (Ed.), pp. 387-398, DAAAM International Publishing, ISBN: 3-901509-60-7, Vienna

Hardy A.E. (1987). Assessment of foot movement. The Journal of Bone and Joint Surgery. Vol. 69-B, No. 5, p. 838

Lei, R., David, H. & Laurence, K., (2006). Computational Models to Synthesize Human Walking. Journal of Bionic Engineering, 3(3), 127-138

Seiciu, P. L., Laurian, T., Filipoiu, I. D., Parvu, F. (2008), New Design Aspects of a Locomotory Rehabilitation Mechatronic System, The 19th INTERNATIONAL DAAAM SYMPOSIUM, "Intelligent Manufacturing & Automation: Focus on Next Generation of Intelligent Systems and Solutions", 22-25th October 2008

Seiciu, P. L., Laurian, T., Bucur D. (2009). A Comparative Kinetic Study on the Non-Conformal Footwear Walk. EWOMS'09 European Workshop on Movement Science, Ed: D. Araujo, J. Cabri and J. Barreiros. p.98