Smart Stair-Climbing Wheelchair Using Tri-Wheel Mechanism For Disabled And Elderly

Abstract

The proposed system consists of a wheel chair the benefits and modification to facilitate climbing of stairs through its special designed features. The purpose of this work aims at developing an automatic Stair-Climbing Wheelchair, a mechanism for climbing upstairs and down stairs stairs for physically disabled people. A Stair-Climbing Wheelchair is a chair that moves upstairs and downstairs. It has speciality to maximize comfort, ease the usage and attractiveness in the home, which is a safe and affordable solution to conquer the challenges that disabled people experience on the stairs. A unique mechanism for climbing stairs, used here is a tri-wheel mechanism, due to its simplicity and ease of design. The tri-wheel mechanism can be easily fabricated, thereby reducing the total cost of fabrication of wheelchair. The tri-wheel mechanism for stair-climbing wheelchair makes it easy to move up and down on stairs. The smart wheelchair is designed to assist disabled and elderly people leading to a higher quality, more independent lifestyle.

Introduction

Wheelchair is a machine used by disabled and elderly people to enhance their moveableness. There are variety of wheelchairs available in the market. Some are manual while some are electrically powered wheelchair. The choice of wheelchair depends upon the physical and mental ability of the user. These typical Wheelchair has restrictions against architectural barriers on its way. Although as per PWD 1995 act it is mandatory to provide an accessible environment in every public building[1] but numerous buildings in India are designed without considering accessibility for physically challenged and wheel chair users.

There exists few models such as escalators and elevators, used to go up and down the stairs but these, are not explicitly for the physically handicapped. For an instance, a physically handicapped cannot use the escalator the only option available to him/her is the use of the elevator. There also exist scenarios where both elevators and escalators cannot be used due to limitations in architecture. The drawbacks in the existing systems are:

1. Elevators occupy more space. Therefore, implementation in places where sufficient space is not available becomes tough.
2. The existing systems consume more power for operation. Despite of using of sensors in escalators for power saving, still the power consumption is high.
3. If these are not operated properly, they can be dangerous
4. Healthy people develop the habit of depending upon elevators; therefore, the physical activity reduces.
5. In elevators, people get struck for hours between floors when the power goes out and there is no back up for the power supply.
6. It involves risk while operating these in wooden houses and buildings.

Ibot is one such technology which costs around $29000 . A manual Stair-climbing wheelchair can be a low cost solution for the user and can enhance the mobility solution to access most of the buildings. The people with physical disability not only have less living space, but also the quality of life is seriously affected and it also brings big burden to their family. it is still very difficult to overcome these obstacles, which is inconvenient for those people who use wheelchairs. So most of the time these disabled or elderly people can only stay at home, and lack of activities outside may influence on their physiology and psychology. This device can also prevent the wheelchair from overturning backward, and improve the security and comfort of the wheelchair. Locking system is added which is used to lock the wheelchair while climbing up and down stairs, making sure it can only move in one direction, and protect the wheelchair from slipping down.

Design process

Walking mechanism design

The walking mechanism is a very important part of the stair-climbing wheelchair; it directly impacts on the stability, safety and comfort of the wheelchair, so all kinds of factors must be considered to choose the walking mechanism. According to the analysis about the advantages and disadvantages between different types of climbing wheelchairs, the following concepts were observed Planetary wheel mechanism has a great advantages among the stair-climbing wheelchairs ,which not only has a simple and compact structure, flexible movement, good stability, small fluctuation range of gravity centre, but also combines the advantages of moving on the ground and climbing stairs. Therefore planetary wheel mechanism is chosen as the walking mechanism in our design.

Planetary wheel mechanism stair-climbing wheelchair

The planetary wheel mechanism is constituted by several small wheels that are equally distributed on a tie bar with shapes like “Y” or “+”. The small wheels can revolve on its axis, and it can also make a revolution around the central shaft. Every small wheel revolves on its own axis, when the wheelchair moves on the ground; and every small wheel revolves round the central axis, when the wheelchair goes up or down stairs. The wheelchair moves by means of a Geared Dc motor. Moreover, to help a paralyzed person to move freely was not only our main concern but also help him to climb stairs is our main motive. Here, planetary wheels refers to tri wheel mechanism. Ordinary planetary wheel structure is when the central shaft drives the central gear; the central gear will drive the planetary gear and the planetary wheels to make the wheelchair go forward. When the wheelchair climbs stairs, the planet wheel is locked by the resistance; the whole planetary structure is derived by the central shaft rolling and completes the process of climbing. In this case, planetary gears will bear great torque and impact and will break easily.

Proposed Mechanism

The proposed mechanism’s operation in barrier free environments, that is relatively flat areas, is based on the use of 2 wheels much the same as a standard powered wheelchair. The front wheels are independently powered and the rear wheels are free-wheeling casters. By independently controlling the front wheels steering is achieved .The wheels used in barrier free mode are 2 wheels of a 3 wheel cluster. By rotating the wheel cluster stairs can be negotiated regarding cluster based operation. . For providing heating and cooling therapy, Peltier element is used. This device has two sides, and when a DC electric current flows through the device, it brings heat from one side to the other, so that one side gets cooler while the other side gets cooler while the other gets hotter.

Methodology

The methodology section outline the plan and method that how the study is conducted. There are two main parts in this chapter which are basic stair-climbing wheelchair design and optimization design. And the design framework is given below :

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Planetary wheels system optimization

Ordinary planetary wheel structure is when the central shaft drives the central gear; the central gear will drive the planetary gear and the planetary wheels to make the wheelchair go forward. When the wheelchair climbs stairs, the planet wheel is locked by the resistance; the whole planetary structure is derived by the central shaft rolling and completes the process of climbing. In this case, planetary gears will bear great torque and impact and will break easily. One idea is got from the car clutch, which is used to control the engine and the wheels transmission separation and combination. Depress the clutch,driving device of the engine is disconnected from the wheels, the power of the engine cannot pass to the wheels; release the clutch, the engine driving device is connected with the wheels, the power of the engine can then pass to the wheels.

Seat backrest System

Most wheelchairs are oblique during the process of climbing up and down stairs, the user will feel uncomfortable, it can easily turnover, which poses a big safety risk. In order to overcome this problem, a seat backrest adjusting device is designed for our wheelchair, so before the wheelchair climbs up and down stairs, this device will adjust an angle for the seat and backrest to make sure the seat of the wheelchair keeps level with the ground all the time.

It consists of a round handle (5), helical gear shaft (4), helical gear shaft (8) and the worm and gear mechanism (7), (10). The working principle for the seat and backrest system is: the user through the handle controls the helical gear shaft rotation, helical gear shaft will transfer torque to helical gear and drives the worm rotation, finally the worm transfer torque to the main shaft, and makes the seat backrest system adjust to any angle.

Locking system design

When the stair-climbing wheelchair climbs stairs, there is danger of falling down the stairs, in order to protect the user and avoid this kind of situation to happen we installed a ratchet mechanism locking system on the central axis. When the wheelchair goes up and down stairs, people can screw the handle to lock the wheelchair and thus prevent the wheelchair from slipping down stairs.

Storage battery selection

The batteries can be roughly divided into physical and chemical batteries. Moreover, batteries of a chemical type which can be repeatedly charged are called rechargeable batteries. There are various types of rechargeable batteries: lead-acid battery used for automobiles, nickel cadmium rechargeable battery called a small rechargeable battery, nickel metal hydride battery, lithium ion rechargeable battery, etc. lead acid battery has been chosen because of the following reasons:

• Lead-acid battery has the advantage of long service life, low price, and can store a large current discharge.
• It has a small volume and light weight.
• The selected motor needs 24V storage battery.

Tri wheel

The tri-star is a novel wheel design originally by Lockheedin 1967[9] in which three wheels are arranged in an upright triangle with two on the ground and one above them, as shown in Figure 1. If either of the wheels in contact with the ground gets stuck, the whole system rotates over the obstruction[10]. A Tri-Star wheel consists of a three spoked wheel and three leaf wheels. The three leaf wheels attached on the end of each of the spoke wheels. All these wheels are powered, which imply that, at rest, each Tri-Star wheel will have exactly two leaf wheels in contact with the ground surface. On the flat surface, the leaf wheels will simply turn giving a smooth and relatively efficient grip.

[Tri wheel working mechanism

The tri-wheel function will be same as l the lever it climbs stairs due to the rolling action of wheels.

This wheel design is very simple, it consists of three wheels, each wheel in mount shafts are mounted the almost like vertices of the fashion. These set of wheels can handle problems related to different types of surfaces like surface with sand and mud. It allows traveling over obstructions like rocks, holes, in rolling action and the third wheel remains idle. When an obstruction occurs, the lower front wheel will stop moving forward, but the driving axle remains in motion and the top wheel will now come into action as a wheel usually lands on top of obstruction and rest of assembly will move over the obstacle. The same process repeats until the required destination is reached.

CONCLUSION

In our work, we designed a novel stair-climbing wheelchair, that can help to overcome problems related to uneven or inclined terrain, stairs and obstacles. All parts of the wheelchair are designed in Autocad. There is no any system which makes physical disabled people fully independent. Various control system could be used to control and cope with different typee of physical disabilities. This paper serves a summary of current state-of-the-art smart wheelchairs. Various technologies are available which are used to operate and control the wheel mechanism of wheelchair. This information is gathered to publicize status of existing types of smart powered wheelchair so that the improvement can be incorporated into it.

References

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9. https://en.wikipedia.org/wiki/Tri-star_(wheel_arrangement)#cite_note-US3348518-1
10. US patent 3348518A, Forsyth, Robert W & Forsyth, John P, 'Amphibious star-wheeled vehicle', issued 1967-10-24, assigned to Lockheed Corp
11. Pothamsetty Kasi V Rao, “Design of stair-climbing wheelchair using tri-wheel mechanism” International Journal of Mechanical and Production Engineering Research and Development (IJMPERD) ISSN (P): 2249-6890; ISSN (E): 2249-8001 Vol. 8, Issue 4, Aug 2018, 717-726