Design and development of stairs climbing trajectory for lower limb assistive device

Senior citizens who faced musculoskeletal deterioration and patients who have recovered from stroke often left with substantial level of mobility disorder. They face difficulties while performing daily activities such as stairs climbing. In order to cope with the issues, a lower limb assistive device is proposed to assist them to perform stairs climbing activity independently. Hence, the objective of this project is to build a lower limb assistive device that follow stairs climbing trajectory of a normal person and to test the accuracy of the device. The device is limited two degree of freedom which is the hip and knee. In order to build a lower limb assistive device for stairs climbing trajectory, two main problems are concerned. The first problem is the accuracy of the proposed trajectory derived using trajectory generation of human gait to climb stairs. The motion of stairs climbing may not smooth and the user may fall from stairs or lose balancing if the accuracy that follows the stairs climbing trajectory is not accurate. Before the device is built, the stairs climbing trajectory must be study. The stairs climbing trajectory is derived into cubic polynomial function and the minimum torque required to perform this action is calculated. Experimental tests such as software simulation and lab test will be applied on the proposed trajectory to show the performance of the proposed stairs climbing trajectory in term of accuracy. In the lab test, a prototype is built in order to compare accuracy of the proposed trajectory derived using trajectory generation from human stair climbing gait and the human behavior to climb stairs compare the deviation. As a result, the proposed trajectory derived using trajectory generation, which is the cubic polynomial function is able to achieve the accuracy of the assistive device up to 88.5% when compared to the normal gait of human behavior to perform stairs climbing motion.