Mechatronic system for neuro-motor disabled persons: computer simulation.

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

Abstract: The paper presents a mechatronic system for the rehabilitation of locomotor disabled persons. The system is based on a basic gait training at which there were added several sub-systems necessary for a complex and full recovery. The complete system will be realized by a team of interdisciplinary trained researchers and will be totally developed in the next two years. The system design and development were based on the latest achievements of human movement science, mechanism theory, medical science and IT. A complete and thorough simulation of the system was performed as a starting milestone of this project.

Key words: Locomotory rehabilitation, movement science.

1. INTRODUCTION

The locomotor disabilities are amongst the most frequent consequences of the strokes. Every year, in USA only, more than 700 000 people are the victims of a stroke, amongst the survivors over two thirds suffering of motor disabilities.

The social and the material costs are huge, and most of the times the patients lives are changing dramatically.

The users of the system can be founded in very large domains starting with the health system (hospitals, rehabilitation centers), and finishing with the persons with disabilities themselves (Hesse et al., 2000). The modern rehabilitation methods were used only in the last period at a small level, due to a lack of equipments. The use of the gait trainers, as a new method appeared like an alternative to the classical rehabilitation [1-3]. The results are similar to the classical methods (Hesse & Uhlenbrock, 2000). A consistent difference appeared with the use of the mechatronic gait simulation systems. In this moment there are only a few systems operating (in Germany, Switzerland, USA, etc) [1-5].

The system we propose is a step forward from the latest of its kind. Our goal is to realize a fully integrated mechatronic system in order to fulfill completely the tasks demanded by the full recovery of the patients in various disability phases.

This implies a complete knowledge of the tasks to be fulfilled, followed by an integrated design, manufacturing and functioning of the main sub-systems: mechanical, electronic, measurement, control (Mauritz, 2002).These are the main aims of our research and they are the original contribution in this field. The next steps consist in integrating two very important sub-systems: the patient self-control feed-back sub-system (PSFS) and the virtual reality sub-system (VRS).

2. SYSTEM DESCRIPTION

The system has several important parts: mechanical, electronic, measurement, control. The mechanical part (main rig) is presented as a CAD view in figure 1. It is composed of: 1--the patient positioning frame; 2--the feet driving module; 3--hand guiding system; 4--oscillating lift mechanism.

[FIGURE 1 OMITTED]

The feet driving mechanism presented as a CAD view in figure 2 is composed of: 1--the feet rest plates with built-in safety device; 2--the double-crank mechanism. The system has 2 original toes and heel independent sliders used to replicate the correct walking positions of the feet.

[FIGURE 2 OMITTED]

The electronic, measurement and, control parts of the system are designed to match the requirements requested.

3. SYSTEM FUNCTIONING, CHARACTERISTICS, FUNCTIONING AND MEASURED PARAMETERS

The patient wears a parachute like harness and is lift from the wheelchair and translated to the training position (Tong &

Optionally, for the case of total paralyzed patients, the knees and the pelvis are linked to supplementary guides. The hands may also be positioned to a hands guiding system. The feet are driven to follow the physiological walking traces. The main characteristics of the gait trainer are:

* power supply: 230V@50Hz, max 750W

* main rig dimensions: 2500x600x250 mm;

* positioning frame dimensions: 100x2500x2

* net weight: 200Kg;

* step length: 18-40

* frequency: 10-30 steps/m

The functioning of the system

* the patient wearing a parachute like is lift from the wheelchair and is translated to the training position;

* the feet are linked to their corresponding plates;

* particular adjustments are made;

* optionally, for the case of tota knees and the pelvis are linked to supplementary guides;

* hands may also be positioned to the hands guiding system

* the feet are driven to produce walking movements.

The parameters to be measured are:

* ground reaction forces;

* body segments accelerations;

* muscular response due to electrical stimulation.

The parameters that can be tuned are: the pacient height displacement, the force on the feet rest plates, the length and hight of the pace, the walking speed (Uhlenbrock et al., 1997).

4. COMPUTER SIMULATION

The computer simulation was made with a specialized software package: FIGURE Biological Modeler and ADAMS.

The simulation input data were:

* body mass: 77Kg;

* body height: 1,78m

* human body compose

The joints considered in the simulation and their degrees freedom are:

--ankle: 1 rotation; --elbow: 1 rotation; --knee: 1 rotation --shoulder: 3 rotation --hip: 3 rotations; --lower neck: 2 rotations --lumbar: 3 rotation; --upper neck: 2 rotations.

The results of the computer simulation are presented in figures 3 and 4. The three force components: [F.sub.x]--force component along the walk direction, [F.sub.y]--force component perpendicular on the walk direction and [F.sub.z]--force component along the gravity direction.

The walk cycle starts with the swing phase and during the walk cycle it can be seen that [F.sub.z] has the largest value with two peaks (268 %BW at 38% of the walk cycle and 177 %BW at 71% of the walk cycle).

The first peak, which is larger, corresponds to the heel strike while the second occurs at the beginning of toe support (single foot support). [F.sub.x] has a similar behaviour but at half values than [F.sub.z]. [F.sub.y] has a lesser influence as it could be predicted. Figure 4 shows the hip flexion-extension variation in a walk cycle. It can be seen that the variation is almost sinusoidal with a magnitude of 40[degrees].

5. CONCLUSIONS

The presented gait trainer will allow paralyzed subjects to practice the gait-like movement without overstressing therapists. The device simulates the phases of gait, supports the subjects weight according to their abilities, and controls the body movement in the vertical and horizontal directions.

[FIGURE 3 OMITTED]

[FIGURE 4 OMITTED]

The kinematics of the lower limbs produces with the gait trainer is similar to the normal walk. The forces appearing at the hip and knee show similar patterns to those reported by many biomechanics studies [1-5].

Gait movements on the trainer are highly symmetrical and impact free. The gait trainer enables severely paralyzed patients the repetitive practice of a physiologic walking movement.

Video analysis of gait and the kinesiological EMG will be used to assess the pattern of movement and the corresponding muscle activity. Walking on the gait trainer is characterized by a symmetrical, sinusoidal movement. In summary, the new gait trainer generates physiological gait-like movement which is important for the restoration of walking ability.

7. REFERENCES

Hesse S; Uhlenbrock D; Werner C; Bardeleben A (2000). A mechanized Gait Trainer for restoring gait in nonambulatory subjects. Arch Phys Med Rehabil, 81.

Hesse S; Uhlenbrock D (2000). A mechanized Gait Trainer for restoration of gait. J Rehab Res Dev ; 37(6):701-708

Mauritz KH (2002). Gait training in hemiplegia. Eur J Neurol. May;9 Suppl 1:23-9; dicussion 53-61.

Tong K.; Granat M.H. (1999). A practical gait analysis system using gyroscopes. Medical Engineering & Physics 21, 87-94

Uhlenbrock D; Sarkodie-Gyan T;Reiter F; Konrad M; Hesse S (1997). Development of a servo-controlled Gait Trainer for the rehabilitation of non-ambulatory patients. Biomed. Technik. 42:196-202