The Minitact is a device for wandering in known large interiors. It avoids common obstacles: people arrested, chairs, tables, half-opened doors photocopiers etc., to stand in the wide corridors, to wander freely in supermarkets, to manage queues efficiently, to have landmarks in the grand halls. The floor should be flat or the position of the stairs should be known. It is not a soil sensor protecting the person from an unknown height difference. Indoor walking on known ground can be done without cane, in situation of unknown ground inside or outside, the use of the white cane is essential. It is then necessary to move towards devices of the type Tom Thumb associating the control of the ground with the cane and the anticipation of the obstacles and the protection in height.
The device emits a vibration when an obstacle is in the protective cone of the device. There are two types of smooth (far) and granular (near) vibration. The protective cone of the device is cylindrical with symmetry of revolution around its axis (looks like a duffel). The appliance is equipped with a three-position switch. The central position of the switch is the off position.
When the switch is in the middle, the unit is stopped regardless of the orientation of the unit. To start it, push the switch forward (long and very long range) or pull it backwards (short and very short range).
Device in very short range, switch up and back. The short-range cylinder is 70 cm long and 5 cm wide. These values are indicative, they can vary up to 20% from one device to another and depending on the color of the obstacle, the cylinder being thinner and shorter on the black surfaces. The vibration is granular (or intermittent producing about 10 shakes per second).
Device in short range, switch down and back. The short-range cylinder is 2 m long and 10 cm wide. These values are indicative, they can vary up to 20% from one device to another and depending on the color of the obstacle, the cylinder being thinner and shorter on the black surfaces. The vibration is smooth (or continuous) between 0.7m and 2m and granular (or intermittent) less than 0.7m (distance from the very short range)
Device in long range, switch down and forward. The long-range cylinder is 4m long and 50cm wide in a corridor (shoulder width a little above average). These values are indicative, they can vary up to 20% from one device to another and depending on the color of the obstacle, the cylinder being thinner and shorter on the black surfaces. The cylinder is also thinner when there is an obstacle than on one side (unlike a corridor). The vibration is granular between 0 and 2m and smooth between 2 and 4m.
Device in very long range, switch up and forward. The short-range cylinder is 6 m long and 1 m wide (almost twice the average shoulder width). These values are indicative, they can vary up to 20% from one device to another and depending on the color of the obstacle, the cylinder being thinner and shorter on the black surfaces. The cylinder is also thinner when there is an obstacle than on one side, but remains more than 60 cm wide and therefore protects the shoulders sufficiently. The vibration is granular between 0 and 2m and smooth between 2 and 6m.
Low battery signal
Three consecutive vibrations regularly on the ignition of the device. Rechargeable batteries should not be used (correct operation is no longer guaranteed even if the unit may appear to work at the beginning of use of some models of rechargeable batteries).
Principles of use
Fields of application of the ranges:
Very long range: in a large hall, it is used to determine which are the main axes, if the space is clear enough to advance in very long range, do not hesitate to use it. From the moment the space is almost completely clear at the long range, only the very long range will be able to find the axis of passage. If this vibrates almost all the time in very long range, to advance in long range in the directions where one found a very narrow passage in very long range.
Long range: It is used in the majority of situations of interiors, only in very narrow places, or in circumvent where there is little space is reduced in short range.
Short range: It is used in very narrow passages at low speed.
Very short range: It is used in the management of queues and in dense crowds stopped. It can also be used to check that a seat is empty.
Keeping the device:
Take the device in its guiding hand (right for the right-handed ones), relax and relax the joints. Bring the device back to the center of the body at the belly button. The device should not touch the belly, there must be space for a fist between the belly and the device. The thumb is placed on the top of the device.
The device is not tilted in the same way depending on the range. The rule is as follows, we point the device to the ground so that it vibrates, it is raised to the limit of the non-vibration, with some degrees of security above so that during the movements of steps the beam does not meet inadvertently soil. In very long range it will be horizontal, in long range it will be slightly pointed down, in short at about 30 ° down, in very short range it is not useful to point it to the ground because it do not touch it, keep the device horizontal.
An inclination with respect to the horizontal can not be maintained spontaneously in duration. The wrist naturally tends to rise and the device will point more and more in height, until touching the ceiling in extreme cases. To avoid this it is necessary to point down to touch the ground and reassemble the device so as to remove the vibration and maintain this orientation (with a small margin of safety not to touch the ground at the slightest movement of the wrist). call this operation to refer to the ground. It is necessary from time to time to take the reference to the ground to ensure the correct orientation of the device. It also helps to better detect low obstacles.
The Minitact must be held by hand, and the axis of the device must be in contact with the palm of the hand so that the rotation is done only by the wrist. It must not be held with two fingers.
The movement of the wrist is a flexion / extension movement and not a rotational movement (like that of a key in a lock). Sweeping in motion must be flexible and symmetrical (equal on both sides). To be effective, there must be good body dissociation. Indeed, only moves the wrist and not the arm, let alone the shoulders.
The amplitude of the scan depends on the chosen scope and the context. The different contexts are:
- No vibrations whatever the direction (a)
- Vibration on one side (right or left) (b)
- Vibration on the right and left of a direction without vibration (c)
- Vibration in all directions (d)
In general (except search direction of passage) one sweeps in the free zone before either and stops the sweep when the apparatus begins to vibrate. There is no point in prolonging the sweep in the vibrating areas.
In the case (a) we must increase the range to try to have benchmarks by the device, do not find vibration in very long range in an interior is exceptional. In a situation of absence of vibration it is necessary to make a sweep wide enough to try to find lateral references.
In the case (b) if one is in very long range one can walk towards the vibration transition non vibration and graze the lateral obstacle without hitting the shoulders (the march of lateral security is of more than 25 cm). On the other hand for the long range it is necessary to take a margin of safety. It means not to advance just in the limit direction of non-vibration, but in a deviated direction frankly in the non-vibration. The beam of the device is fine, it does not necessarily leave enough space for the shoulders when there is an obstacle on one side. In short distance the direction of travel must be further shifted towards the non-vibration to ensure the passage of the shoulders. This discrepancy is acquired by the practice and the rubbing of the shoulders the first times.
In this case (c) if there is right and left vibration, it is possible to advance as long as we find a passage, even very fine (zero amplitude of the scan) in a precise direction. If one is in very long or long range the shoulders will be protected, if one is in short range, it will be necessary to sneak in the passage by setting aside (to present the body of profile).
In the case (d), it is necessary with the wrist only (and not global movements of the body) to seek the direction of a passage. Be careful, we tend to explore one side only. If there is no passage in the direction of travel, reduce the range (if it is long or very long) and repeat the search operation.
Detection of tables and chairs:
It is imperative to have taken a good reference to the ground, otherwise the beam will pass over the chairs and they will not be detected.
Intermediate range between short and very short distance:
For the short range, it is 1.5m horizontally, if in a particular context we wish to have a less anticipation, just tilt it down to take a reference to the ground and then the range will be reduced to less than one meter.
For the detection of rising stairs, the long range with a reference to the ground well taken indicates them reliably. This is not the case for the short-range where they are not detected with sufficient anticipation.
There is no method to detect descending stairs in an unknown environment. If the position of the stairs is approximately known, it can be detected by taking a reference to the ground.
The range to choose depends on the texture of the soil. The darker or brighter the floor, the longer the reach must be. That's why this type of detection can only work on stairs whose type of span has been checked beforehand. If you are looking for descending stairs you are in the vibration and therefore you do not detect any frontal obstacles. It is therefore a use that can only work on descending descents that are expected and sought.
The position used by default is the long range (switch down and forward). The beam width of 60cm makes it possible to find the passage even in case of minimal vibration silence in two obstacles.
When there is no passage in any direction, bring the switch backwards, it goes to 1.5 m range. Beware the width of the beam drops to 10 cm, if there is not a passage with a certain angular width we do not pass or just passing on the edge.
List of exercises:
Walk in the center of a corridor.
Long-range position (switch forwards and downwards). Center the Minitact and hold it roughly vertical (reference to the floor will be made later). To touch the walls on each side with vibration, and to go in the direction corresponding to the middle of the silence. Before leaving to mentally imagine the direction of the corridor, which will facilitate the holding of the straight line. In a corridor as there are obstacles on both sides it is necessary to walk in the direction of the center of the non-vibration. As long as there is no vibration, even a small one, there is room to go without setting aside in long and very long range.
At the end of the corridor the empty angular area will shrink. Enter the center of the narrowing, when it vibrates everywhere reduce the range to 1.5m (switch down and back) and continue to advance towards the center of the narrowing. The doors being glazed or dark they are later detected by the device, which means that in this way you converge towards the door.
Avoidance of a panel or wall recess:
Case N ° 1: the obstacle is isolated, there is absence of vibration on a wide angular zone laterally to the obstacle.
The margins of security to be learned are learned by several scenarios. When the avoidance is too wide, report it. If it is too short, the shoulders rub and the person does not become aware.
Work the recovery of the straight line after the deviation. Make sure that the return to the straight line is done gradually to the image of the initial deviation.
Case N ° 2: the obstacle is one of the sides of a passage.
In this case in long or very long range it is not necessary to find a space without wide vibration to pass.
Searching for a lateral passage
Monitor when space is wider on one side. Consider this widening of the passage to center in and gradually take the turn.
Representation of a vast place in very long range
When stationary put the switch forward and up (range 8 meters and width 1.5m). Look for areas without vibrations that are the major axes of passage. Make a mental representation of the place based on these axes. If the angular width of the passages is important move with this range, otherwise go back in range of 3.5 m, taking the direction of one of the axes of passage found with the range of 8 m.
Very narrow passage
When the long reach gives no more passage, go short and put on the side to pass.
Use the very short range to stand 30 cm from the front person just when the vibration appears. Go slowly, 30 cm is very short, we quickly hit the person in the swing before stopping. Point the camera down to remove the vibration. Repeat it horizontally from time to time to see if the person has not advanced.
Passing between the tables
Use the long range with a reference to the ground, if there is no passage, go short reduce the speed and see the ground reference (device is tilted down)
Searching for the trash: place a trash can (arriving at the height of the knees) in flat and clear ground. Long-range device, take a reference to the ground (point to get the vibration on the ground, just raise the device so as to remove the vibration), then sweep laterally without changing the top down of the device.
Exercises in situation:
Find the exit of a department store.
Fluidity of strolling in a library, slalom between rays.
Make a short trip with explanations to find the corresponding paths (ex: 2nd alley on the right, 1st on the left and 1st right).
Find barriers or balconies to understand why the Minitact vibrates and no longer vibrates, depending on the position of the bars. Sweeping of the hand in front of you in horizontal and vertical.
Stand in front of a window where there is nothing behind (eg a bay window), then a window where there are objects (eg a glass door of a desk) and explained the why of how.
Find the dark colored doors in a hallway.
Run along a wall, stand near the wall. The visually impaired person must, thanks to his device, avoid the person in front of him. This exercise is not easy because it must be able to begin to differentiate what is on the side and what is in front of him in a fine way.
Entry into increasingly narrow passages in shops.
Work the turns at the end of shelves in a shop.
Slalom, between chairs or tables in a cafeteria.