The system for verticalization and aiding the motion (SVAM) that has been built can be numbered among the orthotic robots. As far as the operational use is concerned, the system has a form of a robot, whose movements are transmitted to the patient’s limbs by means of special catches. The main function of the system is to enforce the movement of the lower limbs of the user in a manner similar to a regular human gait. Additionally, the system is to provide the user with the ability of taking some obstacles, including going up and down the regular stairs, as well as sitting on standard furniture and getting up from it. Importance of the problem is shown by statistics. There are 17,1% of handicapped women and 15.4% of handicapped men in Poland. Majority of them are country people which makes their access to health service even more difficult. Additionally 62% of all handicapped has strongly limited ability to perform basic every day activities. There are 1,3mln people in Poland who are disabled to large extent. Motor diseases refer to 46% of all handicapped people and they are the second as to their importance after blood system diseases health problems of those people. Every 15th handicapped person is not able to walk on his own 500 m distance as well as climb the stairs to the 1st floor.
It has been assumed that the device realizes movements of the user’s leg according to determined programs. At the present stage of development, the other elements of the gait, i.e. unloading the leg which is shifted and keeping one’s dynamic balance is left to the user, who is equipped with additional orthopaedic devices, e.g. crutches (Fig.1).
Even though the basic purpose of the device is to restore lost motor functions of the disabled and to reduce the negative medical effects resulting from immobility of the limbs, another important function of the system will be minimization of a risk of additional injuries of the user. The system should eliminate all the possible hazards and prevent realization of any movements if they pose a threat to the patient’s health. In the case of the contemporary mechatronic machines, the safety systems are closely integrated with the systems realizing the main function. It is advantageous when both systems use the same actuators and measuring systems, as much as possible.
The task of the SVAM is to make it possible for a person with impaired motor functions of the legs to keep a vertical position, to walk using the system as well as to stand up and sit down. Users of the system can be both a person that lost the use of his legs (the device realizes then programmed gait functions),as well as a person whose gait is only aided. In both cases, the load-bearing structure of the SVAM realizes a function of a manipulator displacing the user’s legs according to the preset function. In the case when the system takes over performance of the gait, the motion is realized according to a preset trajectory reconstructing the gait of a person with certain anthropometric parameters that have been preset. In the case when an aided gait is to be realized, the system operates as a follow-up system with a position or force feedback. The basic function of the load-bearing structure is realization of motion of the limbs reconstructing the kinematics of the user’s motor organs as precisely as possible. The motion is realized by transmitting movements of the actuators to the user’s limbs by means of the elements of the load-bearing structure (Fig.2). Additional functions of the load-bearing structure are:
• Transmitting the weight of the device to the ground,
• Transmitting the weight of the user to the ground,
• Keeping the user inside the structure of the SVAM,
• Providing a fastening for other elements of the SVAM.
Because the system SVAM is of a special kind, a problem of ensuring security of the user is superior with respect to its main function. In order to realize this assumption, it was accepted that the control system of the device that has been designed is to make it a self-optimizing system. So, the control system has been created in such a way that it aims at an appropriate objective of action of the device, depending on the situation when the user finds himself in:
• launching, realization and supervision of the motor functions, provided the conditions ensure a safe moving for the patient.
• protecting user’s health and life, should a hazard occur.
The system has a modular structure, which simplifies any further modifications and development of the device, especially including additional measuring systems. Modules related to the mechanical sub-system of the device and the battery are interconnected by the supply bus and the communication bus (Fig.3). External modules, i.e. the remote control and controllers processing the measuring signals related to the crutches, have their own battery supply and employ radio communication with the central unit.
The driving modules including the articulations are interconnected by means of couplers with the length adjustable to individual anatomic characteristics of the user. The system is fastened to the trunk by means of a clamping ring called a hip belt, which is a kind of a mechanical interface. Motion of the legs is forced by the foot modules connected with the user’s feet. Rotary motion at the hip and knee articulations (corresponding to the natural joints of the user) is realized by drive modules, which are custom actuators. They are built-in few sizes adapted to a population. The system that has been designed this way is consistent with the latest trends in prosthetics, which assume creation of series of types of complicated modules(e.g. joints) and coupling them with relatively inexpensive elements adjusted to the measurements of the user. Such approach simplifies personalization of the devices aiding the disabled, and at the same time cuts the related costs.
Functional tests of the system are carried on with manikin employed (Fig.4). Their results are used to improve details of mechanical structure as well as to modify control algorithms, particularly movement profiles. The system for verticalization and aiding the motion SVAM is an opportunity to stand up and walk for many of handicapped.
List of published works related to the task:
Fig. 1. Usable structure of the device
Fig. 2. View of mechanical structure of the robot and 3D model of the drive system
Fig. 3. Components of the control system of SVAM
Fig. 4. The first steps of the system