Mechanical and Kinematics Design Methodology of a New Wheelchair with Additional Capabilities

Abstract

Since wheelchairs appeared, only minor changes have occurred with regard to their basic design. An important change was the design of the powered wheelchairs, and it is unquestionable that they greatly improve the mobility of the handicapped. Nevertheless, architectural barriers still exist in many cities and buildings, and it is expensive and time consuming, if not impossible, to eliminate all of them. A new advance in mobility assistance came with the development of wheelchairs capable of negotiating architectural barriers. The first commercial models were based on a single-section track mechanism (SUNWA Co. Ltd). A disadvantage of these tracked systems is that the entire track is forced to rotate on the edge of the first step when initiating descent. This is a difficult and dangerous operation. An evolution of this mechanism principle has been the use of low pressure tyres for ascending and descending stairs. These systems exploiting their ability to produce high grip forces on the edge of the obstacles improving the mobility and efficiency in barrier free locomotion (Uchida et al., 1999), Other designs based on wheels improve the efficiency in barrier free environments but needs additional mechanisms to overcome the architectural barriers. A commonly used solution is to group two, three or four wheels in a rolling cluster. The simplest models are little platforms to carry light wheelchairs (The Wheelchair Lift Company). A negative aspect of this solution is the necessity of an assistant. To operate the system without assistants, a more complex control system is required The problem can be solved by adding another cluster While the mechanical solution is quite simple, the systems are very sophisticated since it relies on dynamic control to maintain the upright position. The main disadvantages of these designs are the high actuating cluster torque, high number of wheels that must be driven and braked, difficulty to add a steering mechanism, and a dramatic increasing in weight, size, and cost. Solutions based on legs improve the movement of the robots in highly unstructured environments To enhance motion capabilities wheels are incorporated. These vehicles are referred to as high-mobility robots since they combine the efficiency in