Standing motion assistance on a robotic walker based on the estimated patient's load

Abstract

This paper proposes a standing assistance control with a patient's load estimation for our robotic walker system. Our developing robotic walker realizes a standing assistance using its support pad which is actuated by novel assistance manipulator mechanisms on its body with four parallel linkages. Our system assists a standing motion using a remaining physical strength of patients maximally in order not to decrease their force generating capacity. For realizing this function, this paper proposes the following two topics. The first topic is an load estimation scheme of a patient who uses our assistance system. Our developed system measures a body motion and the applied force of a patient during standing assistance, and our system estimates the load of trunk, knee and ankle joint using a linkage model which approximates the human body. The second topic is a combination of force and position control. According to the estimated load of a patient during standing motion, our control system selects more appropriate control method from them and realizes the standing assistance using the physical strength of the patient. The performance of our system is verified by experiments using our prototype.

Smart walkers: an application-oriented review

“…For being able to execute any trajectory, two degrees of freedom (DOF) are needed in addition of the mobile part. 90 Keeping the orientation of the arms of the users constant simplifies the problem: only one DOF is required. 76,92 .…”

“…Some designers propose a braking system to ensure a support that does not move for the user, 88 others control only the forward direction of the SW in order to pull the user 88,89 and some others implemented more complete help with more complex movements. 90 The solution of only pulling users is not ideal because it does not fit with natural STS. However, this solution is simple and offers a first solution for assisting users.…”

“…In order to increase the provided help for users, some designers realised forearms or chest supports. 33,37,50,76,90 For this kind of support, three dimensions have to be considered (the position of one point and the orientation of the support surface). For being able to execute any trajectory, two degrees of freedom (DOF) are needed in addition of the mobile part.…”

“…The same team has proposed to assist STS not only with a following of trajectories but also with force control in order to prevent a too high knee torque. 90 When the mechanical design and the control of STS is done, the willing of changing of state remains to be determined. Hirata et al 88 used the distance between the SW and the trunk for detecting in which phase the user is.…”

A review of the functionalities of smart walkers

“…Recently, some studies [41][42][43] started to implement more complex movements to help in sit-to-stand. In order to implement such movements, sit-to-stand was first studied in the sagittal plane.…”