Inverse dynamic tracking control of sitting and standing movement

Abstract

Sit-to-stand motion is one of the most basic movements of each person throughout his life and is done repeatedly. This motion is prerequisite for other movements like running and climbing that in many people is easy to do, and in some people it may be hard to do or even not done at all. One way of helping the elderly and disabled people to do this motion is designing a device to facilitate this motion without need of assistance by others. To design such a device, it is necessary to obtain the dynamic equations of the body and then apply the appropriate control system on it. Activities in this field can be divided into two categories: obtaining experimental data for this motion involves the angles of body segments and forces, and then providing the torque values associated with each actuator in the device mechanism to optimize the motion, and second, provide nonlinear control methods to bring the current state of the device to a desired state such as adaptive and robust control methods. Also, due to the different conditions of each individual relative to the others, such as how to sit, body anatomy, age, etc., it is necessary that the proposed device and control system properly operate in a variety of conditions. The main purpose of this study is to design a suitable control system for devices that designed for helping people to stand and sit correctly. We propose inverse dynamic tracking for controlling the system. This control method has not been used to control this move yet. With such a control system, one can control the posture of assistive devices, such as lower limb three-link exoskeletons, and standing assistance systems to achieve natural motion.