Visual Aids Based on Ultrasonic Sensors …
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2 Theoretical Aspects of Patient Mobility with Low Vision
After losing the ability to perceive information in the environment, the mobility of
patients with low vision or blindness is mostly affected and poses a major disadvantage to them in the development of rehabilitation procedures. The cycle of walking,
posture, its stability and balance components, other dynamic activities (running,
climbing/descending steps) are altered, altered by the lack of the fixation point of
the visual system and the binoculars used in the binocular view. Patients with visual
impairments require visual aids to improve their posture, gait, or other activities
involving the locomotive system, and they are designed and developed each time in
relation to anthropometric dimensions and patient needs. In general, continuous adaptation with additional energy and effort to distances or performing dynamic activities was observed in subjects with visual disabilities [3]. As shown in experimental
research systems based on “the touch-walking model of human can be described by
the following formulas:
⎧
⎨
⎩
J ¨
β = M + M d
M = K 1 · u c
M d = −K 2 · ˙
β
(1)
where J is the moment of inertia of the blind along the yaw axis, M the kinetic
moment that the blind applied to himself when turning, M d damping torque on the
yaw degrees of freedom, β the angle of the traveling direction of the blind, u c the
controlled quantity that output by controller, K 1 the scale factor between the kinetic
moment and the controlled quantity, K 2 the damping factor” [4]. In this system, the
transfer function is computed between the input u c and output intakes, represented
by the angle β of the direction of displacement of the patient and is respectively
expressed by the relationship (2) according to the same experimental determinations
[4].
G(s) =
β(s)
u c (s)
(2)
Also, in order to be able to analyze the data gathered from the registration modules,
it is indicated the use of the sigmoid function which presents an important characteristic, especially for studies on the stability of the human body. Thus, the movement
of the human body around its equilibrium position can be described by a linear variation, and outside its function the function has a nonlinear argument and a variance
that tends exponentially toward a unitary value (see Fig. 1) [5].
The posture of patients with low vision will change from the posture of a person
with a good view, but will show a personalized variation in relation to the body
mass center (COM), the only difference being the longer duration of the required
distance [6]. What is remarkable is the fact that from the experimental research it was
245
2 Theoretical Aspects of Patient Mobility with Low Vision
After losing the ability to perceive information in the environment, the mobility of
patients with low vision or blindness is mostly affected and poses a major disadvantage to them in the development of rehabilitation procedures. The cycle of walking,
posture, its stability and balance components, other dynamic activities (running,
climbing/descending steps) are altered, altered by the lack of the fixation point of
the visual system and the binoculars used in the binocular view. Patients with visual
impairments require visual aids to improve their posture, gait, or other activities
involving the locomotive system, and they are designed and developed each time in
relation to anthropometric dimensions and patient needs. In general, continuous adaptation with additional energy and effort to distances or performing dynamic activities was observed in subjects with visual disabilities [3]. As shown in experimental
research systems based on “the touch-walking model of human can be described by
the following formulas:
⎧
⎨
⎩
J ¨
β = M + M d
M = K 1 · u c
M d = −K 2 · ˙
β
(1)
where J is the moment of inertia of the blind along the yaw axis, M the kinetic
moment that the blind applied to himself when turning, M d damping torque on the
yaw degrees of freedom, β the angle of the traveling direction of the blind, u c the
controlled quantity that output by controller, K 1 the scale factor between the kinetic
moment and the controlled quantity, K 2 the damping factor” [4]. In this system, the
transfer function is computed between the input u c and output intakes, represented
by the angle β of the direction of displacement of the patient and is respectively
expressed by the relationship (2) according to the same experimental determinations
[4].
G(s) =
β(s)
u c (s)
(2)
Also, in order to be able to analyze the data gathered from the registration modules,
it is indicated the use of the sigmoid function which presents an important characteristic, especially for studies on the stability of the human body. Thus, the movement
of the human body around its equilibrium position can be described by a linear variation, and outside its function the function has a nonlinear argument and a variance
that tends exponentially toward a unitary value (see Fig. 1) [5].
The posture of patients with low vision will change from the posture of a person
with a good view, but will show a personalized variation in relation to the body
mass center (COM), the only difference being the longer duration of the required
distance [6]. What is remarkable is the fact that from the experimental research it was