Technical solutions for sensing elements and their integration to construct remote operation devices to assist disabled people

Mobility is an important component of modern life. Unfortunately there are people, who are deprived of the ability to move. Some of them became disabled as a result of an incident or a disease, such as Alzheimer’s disease. Others were doomed to be immobilized from the very birth. However, in modern world of high technologies it became possible for the disabled to feel themselves almost like normal people with the help of modern control systems, electronic devices, robotic arms, well-equipped wheelchairs and other technical solutions. This research paper is devoted to construction of modern assisting devices for people who are unable to move their limbs. A lot of new technological appliances have been developed to fulfill everyday needs of the disabled and guarantee security. The following research deals with the principles of measurement and instrumentation, emphasizes the significant role of modern control systems and examines recent achievements in engineering and computer programming, aiming to improve the life of people who cannot move their upper and lower limbs. It also examines a wide spectrum of sensors, implemented to various assistive devises.
Introduction of modern technical devices into the everyday existence of disabled people is highly productive and has a wide range of advantages. Firstly, it reduces the working hours of the nursing staff and saves time and money. Saved money can be paid for the robots and other assistive appliances, which often appear to be more useful than the whole nursing staff. In this way, introduction of modern technical solutions for disabled people is highly beneficial from an economic point of view.
In addition, new control systems and assistive devices greatly improve the quality of life of severely disabled patients. What is more, with the help of all these systems the disabled become more self-sufficient and independent. It naturally motivates scientists to perfect the existing technologies. Though many devices can’t completely substitute the assistance of a real person, they evidently save time of serving the disabled.

Robotic Arms
In present days a lot of technological devices, aiming to serve disabled people, are being developed in progressive countries. In Britain, for example, scientists are elaborating a robotic arm, which is an exact duplicate of a human hand. It means that people who can’t move their extremities will be able to fetch necessary things, food and drinks with the help of this robot. The producers used high technologies, modern materials and advanced computer programming, and hope to finish the prototype arm in a year. The authors expect this assisting device to accomplish success, and plan ultimately to develop an advanced robot that copes with a wider variety of assignments for the disabled. Although the duplicate of a human hand skillfully performs more than twenty movements, disabled people claim that no robot can replace the elastic extremity of a human being. The innovation of this robot is application of air muscles instead of electric motors to enable the hand to move.
Air muscles enhance the range of movements the robotic hand is able to do. The construction is based on remote control and camera systems, which make it possible to perform a number of simple tasks that will be useful for people who need daily assistance (Kawamura 1995, 145).
In addition, the robot possesses true commercial potential, as it not only assists disabled people, but also helps to cope with the infirmities of age. Originally the robotic arm was constructed as an attachment to a wheelchair. Modern scientists, however, moved further, and succeeded in making a separate robotic arm with flexible internal angles, although it has no sensors. Its arms are capable to carry nearly four kilograms. The robot moves by shifting from one docking place to another. Those places fulfill the dual function of both reinforcing and powering the robot.
Another robotic device for the disabled was constructed in Japan. This one is able to climb the stairs with its ten legs. It successfully carries a person weighting not more than sixty kilograms. The robot is supplied with a system of modern sensors, which will be further discussed in this report in detail.
The automatic robots-manipulators, attached to wheelchairs or walls, help people with disabilities to eat, brush teeth, shave and perform other simple tasks to fulfill daily living needs. Sensors are important elements of most technological devices for disabled people. British scientists succeeded in creating fast and effective sensors, which guarantee security for users of wheelchairs, robots and other assistive appliances. One of the most important demands for sensors is maintenance of continuous work in various conditions. That is why scientists should take into consideration all possible changes in temperature, wire vibration, etc.

Sensors
Security is an ability of a sensor to perform required functions within a certain period of time. In other words, sensors help the device to function duly (Fraden 2003, 78).
Sensors are able to guide disabled people in wheelchairs back home. Moreover, with the help of sensors, users of electric wheelchairs are alerted of obstacles in their way. Advanced sensors are also used to inform the staff in case of emergency on the location of the wheelchair, so as to take measures without hesitation. Sensor systems contain parameters of the vehicle, which makes it easy to define the location of the wheelchair with the help of radio modem. The deviation between expected and real positions of the wheelchair is not more than five meters. This system is capable to guide the user of the wheelchair back home in case he has gone astray. All these functions are highly important as they guarantee security for disabled people and increase their mobility. Nonetheless, it should be mentioned here, that principles of measurement and instrumentation are very important in the construction of a powered wheelchair, especially if it is implemented with some kind of an assistive device. Errors in estimation, precision and accuracy may lead to disastrous consequences. Each measurement with any measuring instrument requires precise estimation, so as to avoid errors. Engineers cope with this dilemma by choosing middle measurement.
Thus, if to express this opinion from mathematical point of view, it should be said that with a measuring instrument demarcated in hundredths of an inch implies possible error of 0,005 inch (Morris 1988, 167).
That is why the exactitude of a measurement depends on the instrument itself and on the precision of its scale. The quality of measurement also depends on how correctly the numbers were rounded off. The accuracy of measurement should always be taken into account. Thus, the length of a robotic arm will define the maximum possible error rate and the exactitude of measurement. As a rule, the length varies according to the body size of a user.

Rehabilitation robotics
Another assistive device worth mentioning in this research is a robot for people with genetic disabilities or spinal cords disorders (Honzic 2003, 56). It is to be mentioned that this robot has a significant advantage over other similar devices, as it highly increases abilities to maneuver and pick up objects. The robot relates to the category of rehabilitation robots and is called ARDIS, which is deciphered as Assistive Robot for DISabled. These robots perform assignments for severely disabled people. They were constructed to function like prosthetic appliances of upper limbs, except that they are not exactly joined with the body. In this regard such robots can be used to perform a great number of manipulations, which disabled people fail to do. Moreover, they have less power and size demands in comparison with traditional prosthesis.
There are three types of these rehabilitation robots:
? Uncomplicated appliances, which are capable to do elementary everyday tasks, such as feeding and turning the pages. Improved technologies, however, allow them to cope with more complicated tasks, such as putting on make-up, brushing teeth, cleaning, etc.
? Workstation robots represent a collection of motionless assistive appliances, which are specifically designed to meet user requirements in their everyday activities.
? The group of rehabilitation robots also includes wheelchair robots, which increase mobility and operation of wheelchairs. They represent an arm, attached to the powered vehicle for disabled people. This arm helps the disabled fetch drinks, eat, switch off lights, open doors, etc. The structure of the robotic arm is very flexible, as it has rotatory shoulder, elbow and wrist. The arm is able to pick up relatively small objects on the floor, table and other surfaces.
Rehabilitation robot has two elements of control, which influence the way of functioning: the interface between the disabled individual and the robot, and the interface between the robot and the objects. It limits the variety of operations that can be performed.
The device is controlled by means of a standard joystick, which is not as convenient as modern technology of using voice electronic device and gesture recognition. Wheelchair is operated by two disconnected devices, which control the robotic arm and the vehicle itself. Such a system complicates the utilization of the wheelchair, as a person has to operate these two devices in turns.
If a person wants to pick up an object, he has to operate the gripper itself and the wheelchair to approach the object. Nonetheless scientists are planning to improve the device by making the wheelchair move automatically in the direction of the chosen object, if the user intends to reach it. In this way the system of sensors is supposed to ensure the safety of travel towards the object. It will be possible to navigate the wheelchair almost autonomously in its working space. This construction is especially useful to people who can’t move their limbs. The vehicle is implemented with sonars, used to measure the distance, and a camera with 360 degree field of vision. This panoramic camera is capable to follow a moving person. It preserves the vehicle from collision. A panoramic vision is much more advantageous than cylindrical one. People with motor disabilities have to cope with various problems when moving in areas intended for healthy people. Semi-autonomous navigation means that the variety of problems can be solved by the wheelchair in collaboration with its user. The user gives commands to the wheelchair, such as selection of a moving person that is to be followed, or the direction of movement. Everything a person needs to do is to touch the screen or give a voice instruction.
What are the advantages of rehabilitation robots? Rehabilitation robots help disabled people feel independent and cope with simple tasks. Assistive robots for disabled can be productively used for practical purposes in cluttered surroundings, where omnidirectional wheelchair will surely come in handy. The construction consists of the end-effector control, which makes it easy to perform required tasks. The velocity of the wheelchair is also controlled.
Wheelchairs with computer control systems
Speaking about modern technological devices for disabled people, it is important to mention that a lot of wheelchairs nowadays are also equipped with a notebook, which contains data on motor control, sensor system and electronic appliances, attached to the wheelchair.
A lot of electric wheelchairs are also based on digital control system. Such a construction simplifies the navigation of the vehicle (Franklin and others 1994, 230).
Here, it is important to illustrate this control system, giving a real example. Thus, a world-wide known Professor Stephen Hawking suffers from a severe motor neuron disease, which makes him unable to move limbs and use voice. Such people especially need improved wheelchairs and new voice recognition systems. Professor is confined to a wheelchair, which was once implemented with a DOS-based computing system and a voice electronic device. Recently Professor has been supplied with a computer, which has only one button. This new tool somehow predicts what the next actions or intentions of the user will be. In comparison with his former computing system, this one has much more advantages. Although his former computing system had a range of essential capabilities, it was deprived of things that modern people take for granted. It reduced the speed and effectiveness of computer systems. The new technical solution, however, not only works at high speeds, but also has access to the Internet which will surely improve the life of disabled people. Producers hope to make this new computer device as affordable as possible. This technical solution is supposed to enable people with mobility impairments to perform additional and more complicated tasks. With the help of Internet they will be able to communicate, work and study. This new software is available for severely disabled people as well.

Scheme of the wheelchair sensor and control system

Why is it important to develop new control systems and widen the range of functions of assistive appliances for disabled people? There is not a shadow of doubt that a user of a wheelchair, for example, should be skillful in operating it. He should behave properly and pay attention to the surroundings in order to avoid unnecessary injuries and crashes into walls and passersby. There is always a threat to hurt oneself and people around. On the other hand if to deprive disabled people of social life and limit their freedom, it will surely cause apathy and inappropriate behavior from their side. Lack of mobility can be extremely traumatic. That is why it is important to improve technical solutions for disabled people. Thus, standard wheelchairs are supplied with sensors, motor control, speed measurement and joystick. However, modern wheelchairs are equipped with a number of additional appliances as well. They include ultrasonic detectors of obstacles, system of navigation within the house and escort driving outdoors. Escort driving provides information on the vehicle’s direction and helps to keep a chosen distance.
Speaking about modern devices for disabled people, it is important to describe the ultrasonic ranging system in detail. This circular construction consists of five ultrasounds and a sensor, fastened to the forepart of the vehicle. The disconnected circle allows entering the wheelchair. The ultrasounds discover obstacles within the area of several meters in front of the wheelchair (Mazo 2004). It is to be mentioned that such ultrasonic systems are frequently used in wheelchair constructions, though their practical application is rather confined. The matter is that they mostly discover large obstacles, which a person is able to notice himself.
For this reason ultrasonic systems are often combined with highly sensitive sensors, which are designed to satisfy needs of users and modernize the detection of obstacles. These additional sensors are needed to provide secure driving. There are three vertical lines, projected by the sensor and a camera to spot those lines (Miller and Slack 1995, 77).
Scientists of Toronto University Department of Intelligent Assistive Technology presented a new collision avoidance system for wheelchairs operated by disabled people. The systems are supposed to increase mobility and make disabled people feel more self-confident and independent. The innovation of this system is the use of Canesta sensor instead of a laser one. It possesses a range of advantages, including three dimensions, ability to create images and minor power demands (Hoey 2004, 24). It is an improved version of ordinary collision sensors. Thus, sensors will bring the wheelchair to a stop in case there is a threat of collision, and will offer alternative direction. Such sensors are able to detect obstacles and safely avoid them in various situations.
Technical solutions for people with upper limb disabilities
Modern control systems combine traditional and improved control principles, based on computer and design technologies (Golten and Verwer 1991, 63). They provide a wide range of opportunities for disabled people. People suffering from upper limb impairment are now capable to drive a car with the help of new hand control system. This system allows a driver to operate the car by pressing buttons with fingertips. The button transmits a signal to a control box by means of electric wires. This modern control system is intended for people who are unable to drive with both hands. The system is attached to the steering wheel, which simplifies its use. It can be detached at any time in case it is no longer needed. Car switches are illuminated by infrared controls that enable the driver to see in the dark. The serviceable life of the battery is not less than a year.
Eye-tracking systems for the disabled
The producer of EyeTech Digital Systems created a system, which represents a combination of a camera that follows the movements of eyes and voice dictation computer program. Originally this product was intended for people with motor disabilities, who can’t use computer or type with their hands (Johnson 2006).
In the course of time this software became a threat to existing computer systems, as eye-tracking devices proved to be useful for disabled and healthy people as well. This is a new kind of control system, which is quite easy to get used to. With the help of this program people with severe impairments become self-sufficient and less dependant. More and more people choose this system for a wide range of reasons. One of them is the reduction of price for such software, which makes it relatively affordable for common people.
Another problem is motor disabilities among children. Disabled children have no opportunity to develop in the way normal people do. For this reason, scientists attempt to create new technical gadgets, which will guarantee relatively happy childhood to such children. It should not be forgotten that not only adults may suffer from upper limb impairment. There are cases, when children become physically disabled too. Modern technical solutions help to partially overcome this problem. The specialists from the Oregon University Department of Computer and Information Science offered a software program EyeDraw intended for children, who can’t move their upper limbs. The program was designed to allow children with motor disabilities to draw pictures with the help of an eye tracker, so that they can develop their imagination and creative skills. The project contains several innovations, the most important of which is the possibility to cope with spatial assignments by means of eye-contact.
This new fundamental idea actually allows everyone to use this eye-drawing control system, even though the program was originally designed for disabled children. The central technique implies the possibility to perform such computer assignments as choosing icons on the desktop by delineating a square around them.
The eye tracker was designed to assist children with severe motor disabilities, and scientists have already proved that it is beneficial for children without impairments as well. Its effectiveness for disabled children, however, is still being observed. The way children draw pictures with pencils or computer mouse has contributed into the advancement of recent technology. This program also helps to understand the development of children’s drawing abilities step by step. It shows how children learn to control movements of their hand, gradually improving drawing skills. Drawing with eyes needs the same efforts and patience, as the traditional drawing with hands. Drawing with eyes needs specific techniques, such as quick short movements of eyes, called saccades. The line, which goes from the eye to the place where a child is looking, is called the gaze. A continuous gaze, fixed on one point is called the dwell.
This software capacitates people to operate the computer control system with eye movements. This capacity is of great importance for people with severe mobility impairments. The disabled have no opportunity to socialize with outer world, although most of them possess normal eyesight. The ability to control the movement of eyes is probably their only hope to contact with other people. In this regard, the eye-controlled computer system can greatly improve the quality of their life. New control system is able to interpret pupil shifting of the user and accomplish the required tasks. Not long ago people only learned to talk by means of computers. Now they are able to operate them with eyes. Researchers had to change the functional user interface in order to meet new requirements. The icons must not be too small, because eye shifting is not as accurate as hand one. A significant feedback for people, operating this computer, is that the icon changes its colour twice. It means that the computer has comprehended the task and is ready to accomplish it. Probably the only engineering task now is to solve the problem of jerk-like movements, made by our eyes. A lot of eye-controlled systems have been designed for the sake of disabled people’s well-being. Nonetheless it became a moving force for further improvement of this technologies and application of them in various spheres of human life. Such systems as Quick Glance and VisionKey are among the most advanced technologies nowadays. They provide operation of a computer by means of eye-typing. These technologies were appreciated by a great number of disabled people and helped them to lead a more normal life. The most efficient systems allow users to pronounce phrases by means of speech synthesizer, operate devices and turn pages in e-books. Typing is fulfilled by shifting eyes across a computer keyboard placed on the screen. Of course, the development of these systems is not finished yet, and they fail to accomplish a lot of tasks, which healthy people can easily do by means of crayons and paper. Nonetheless, this software program can successfully be used by disabled children, who should develop creativity and imagination. This is one of the new technical solutions, which help disabled children live and develop as normal people. A technical advantage of this program over other similar ones is the opportunity to look and examine the drawing within the process. The previous software gave users no chance to study the picture before it is completed. It shows that computer industry moves forward and improves the eye-tracking software, creating more and more opportunities to skillfully draw pictures.
Alternative control of a wheelchair for people with upper limb impairments
People, suffering from upper limb impairment, experience a number of inconveniences. Thus, many disabled people find it difficult to control a wheelchair. Recently a new way of a wheelchair control has been designed to assist people with upper limb disabilities to control an electric wheelchair without joystick. The new system is based on muscle control, which allows people with mobility impairments to safely navigate without manual contact. Electric wheelchairs are irreplaceable for people who cannot control a mechanical wheelchair without assistance. The idea of a free-hand control system came from the necessity to assist people, who cannot even use joystick to operate the wheelchair. It gradually became a promising technology, as an alternative way to manual control. The device reacts to biological signals, such as movement of muscles and eyes. Thus, this control system relies on bio-signal interfaces, which perform commands, identifying certain muscular constrictions. An advantage of this system is that it does not require the application of a laptop computer. It makes this device almost absolutely independent. In order to make a detailed analysis of this construction, it is important to show positive and negative sides of the new control system. First of all, it is to be said that this system is a forerunner of the tongue-controlled interface that will be discussed later. From scientific point of view, the functioning of this system is basically ideal, as everything a disabled person needs to do is to use muscles or just brain-waves. However, the idea of brain-computer interfaces is not perfect. Such devices appear to be too sensitive and react to intentional commands and background noise too. The noise includes sounds of swallowing, laughing or talking. However, this system is not suitable for operating a wheelchair, because of its sluggishness. It takes several seconds to bring the vehicle to a stop in case something prevents further movement. A bio-signal interface that reacts to eye movements also has a number of negative sides. Thus, the user of a wheelchair is unable to look in all directions while driving, as it may be dangerous. In this way, the control system, which is activated with the help of muscle constrictions, is the most appropriate variant. It allows a disabled person to direct the wheelchair wherever he wants. The system, however, has a number of disadvantages. One of them is that it does not work in noisy surroundings, although in the course of time this problem can be worked out. The price of such assistive devices depends on their constructions. Some of them are additionally equipped with video cameras, which make them less affordable. The sensors implemented to such devices are capable to detect mere raise of an eyebrow. The sensitivity may be increased or decreased, depending on the will of a user. Besides, there are no reasons for a person to be anxious about the strength of muscle constriction, because the system is capable to react to the slightest movements, which must be strong enough to surpass the threshold. It releases users from the necessity to continuously control the vehicle.
Voice recognition systems
A voice electronic device is another technical solution, which is intended to help disabled people feel themselves productive members of society. This technology recognizes words by separate phonemes. It does not mean that it will effectively identify each pronounced word, let alone non-standard speech.
As has been mentioned, modern wheelchairs, equipped with a good deal of assistive appliances can be very helpful to disabled people with upper and lower limb problems. In this regard, an advanced technology of Voice Recognition system makes people with disabilities more self-sufficient and almost wholly eliminates the need for nursing. This technology, however, is not appropriate for people with speech problems, such as Alzheimer’s disease, cerebral palsy and other severe disorders. For this reason, Integrated Wave Technologies, Inc. has created an improved Voice Recognition system, which allows identifying non-standard words. It is based on the program, which identifies the speaker and adapts to the peculiarities of his speech, even if it is impaired. In this way, it is also an ideal assistant for people without speech problems, as it is capable to recognize the spoken words more precisely and avoid mistakes in recognition. This Voice Recognition technology helps disabled people easily operate computers and other assisting gadgets. One more advantage of this technology is that it can be easily implemented to wheelchairs, TV sets and other commodities, which need voice control. Thus, these devices significantly reduce financial expenses, as they do not require Pentium processors.
The ideal characteristics of the voice device are supposed to be the following:
? Hand-free manipulation;
? Identification of non-standard words and only intentional instructions;
? Easy adaptation to laptop computers and other modern technical devices;
? Reasonable prices and affordability.
It is to be mentioned that in many cases efficient measurement activities measurement systems and instrumentation are very important in today’s world of high technologies. Measurement systems are applied to gather useful data on the conditions of systems that serve multiple purposes (Sydenham and others 1989, 90). Exploratory purpose means that measurement is supposed to guarantee complete comprehension of a new system or virtual reproduction of it. At first, scientists state a hypothesis, which provide information on the system, its sensors and appliances. And then this hypothesis is proved to be either true or false. Measurement is also used to control and rectify conditions.
Speaking about modern technical solutions for disabled people, it is important to discuss a tongue-computer interface, which is capable to help people cope with a wide range of tasks. It is a promising technology due to the fact that such interfaces are actually unseen and can be easily operated by people with severe mobility impairments. According to statistics a lot of disabled people have chosen this new system, based on tongue control, although it is not a high-speed device. Nevertheless, this device is equipped with nine sensors, which are accurate in measurement. The “Handbook of modern sensors” by J. Fraden clearly illustrates that accuracy is the most important characteristic of any sensor.
When speaking about the accuracy of a sensor, it is often implied inexactitude and errors in calculation as well. As a rule, the error of measurement means the size of maximum divergence between the readings of real and ideal sensors (Fraden 2003, 93).
The basic tongue-computer interfaces represent buttons, which are sensitive to pressure and located in the mouth above the tongue. That is why the system does not work while eating and communicating. For this reason, pressure sensors are not an appropriate option. Nonetheless a system with only nine sensors is affordable from commercial point of view. This control system is applicable to a vast variety of assistive devices for disabled people, such as powered wheelchairs and prosthetic appliances.
The technique of detection, applied to this construction, works according to Faraday’s law of induction for coils and contains a wide range of inductance methods. In order to accomplish success in assisting disabled people, the control system should be improved so as to meet user requirements. The ability to continuously wear this system is one of the ways to make it suitable for disabled people. It should also be invisible, so as to make it possible to wear it outdoors. This control system should be applicable not only to wheelchairs and prosthetic appliances, but also to computer systems and other devices. It is also preferable to increase the speed of operation. As for the measurement, it should be admitted that the approximate rate of errors makes 20%. For greater efficiency this rate should evidently be reduced.
Finally it is to be said that there is one more aspect of various assistive tools and devices for people with motor disabilities. This research was mostly devoted to modern types of wheelchairs implemented with robotic arms and other control systems. Although such modern devices obviously make life of disabled people easier, they have a range of drawbacks, which are worth mentioning. This research has proved that modern technical solutions are able to compensate for loss of movement and help people with disabilities partially accomplish their personal goals. Nonetheless, it is frequently very difficult for the disabled to get hold of rehabilitation devices. Even if a person with motor disabilities succeeds in obtaining an improved wheelchair, for instance, there is a threat that it will be impossible to efficiently operate it in inappropriate conditions. In addition, not many people can afford to purchase an assistive device, as most of them are very expensive. Transportation and additional repair expenses should also be taken into account.
Conclusion
Unfortunately, even in the world of high technologies, the number of chronically disabled people does not seem to reduce. Moreover, there is a considerable growth in the number of older population, which suffers from motor disabilities. This research paper analyzed the recent improvement of control systems and technical solutions, intended to assist people with motor disabilities. The paper paid much attention to modern wheelchair constructions with ultrasonic and infrared sensors, robotic arms, eye-tracking systems, voice recognition devices and other rehabilitation technologies. These assistive devices productively serve disabled people and fulfill their daily needs.

References
Bentley, J. 1988. Principles of Measurement Systems. Longmans Scientific and Technical, London.
Fraden, J. 2003. Handbook of modern sensors, Physics, Designs, and Applications, Springer.
Golten, J. and Verwer. 1991. A Control System Design and Simulation, McGraw-Hill Book Company.
Kuo, B. 1995. Automatic Control Systems, Prentice-Hall, Inc.
Morris, A. 1998. Principles of measurement and instrumentation, Prentice-Hall International.
Sydenham, Ph. et al. 1989. Introduction to Measurement Science and Engineering, Wiley.

Additional Resources
Hoey, Jessica et al. 2004. Obstacle avoidance wheelchair system. University of Toronto.
Honzik, Bohumil. 2003. Inverse Kinematics and Control of the Assistive Robot for Disabled. Brno University of Technology.
Johnson, Andrew. 2006. Product helps disabled people use computers. The Arizona Republic. October 26, http://ubceac.org/files/Let your eyes control your PC.pdf (accessed August 19, 2007).
Kawamura, K. 1995. Intelligent robotic systems in service of the disabled. Rehabilitation Engineering.
Miller, D., and Slack, M. 1995. Design and Testing of a Low-Cost Robotic Wheelchair Prototype, Autonomous Robots.
Mazo, Manuel. 2004. Wheelchair for physically disabled people with voice, ultrasonic and infrared sensor control. Autonomous Robots, Springer Netherlands, Volume 2 Number 3.