Wireless route planner for a programmable wheelchair

A large number of people with activity limitations and functional disabilities resulting from cerebral stroke, arthritis, multiple sclerosis, loss of lower extremity, paraplegia, and orthopedic impairment rely on manually driven wheelchairs for their primary means of local transportation. Over a long period of time, the repetitive hand action of pushing rear wheels often leads to shoulder muscle, tendon and joint fatigue with the possibility of injury. The condition is aggravated by travel over rough terrain since forces are transmitted through hand, wrist, and elbow to the shoulder during the relaxation phase of the work-stroke. The purpose of this paper is to provide mathematical requirements for route planner software in a wireless connection between a wheelchair user and an Internet server. Using a mobile Java-based device, the user uploads a request to an Internet server for the thoroughfare to a street location. The server has access to a database developed from high-definition cameras mounted on automobiles and tricycles and that contains topographic information on the course. At a start of an iterative process, the server considers the shortest passage on a map and accesses a database to ascertain topographic data on street slopes at discrete points along the path. Providing reference, a space curve that satisfies mathematical conditions of smoothness is chosen. Undulation and bank angles as well as the curvature at a point along the space curve are calculated in terms of inertial coordinates. Although the undulation angle appears in bounded functions, its temporal derivative does not. Importance is then given to curvature of a point on the space curve. Propensity to slide is associated with bank angle. Equations of motion that incorporate undulation and bank angles and curvature are integrated from initial values taken from the route, particularly those of wheel azimuth and level plane position. Wheel attitude, center of mass position, and terrain forces are then found. If the forces exceed comfortable limits, sudden jolts and unstable side-slips would nullify the choice of space curve and another would be selected. The iterative process continues until safe passage results. We thereby obtain a mathematical correspondence between allowable terrain forces and points on a physical route. The final and acceptable path is downloaded to the mobile device.