Temporal Optimality of a Via-Posture on Trajectory during Sit-to-Stand and Back-to-Sit Movements

The purpose of this study was to examine the hypothesis that the minimum angle-jerk with via-point model could account for the temporal consistency of kinematics in sit-to-stand (STS) and back-to-sit (BTS) movements. The positions of bony landmarks on the subjects during the tasks were recorded using a Vicon motion analysis system to yield the angular displacement and position of the center of mass (COM) of a three-link rigid body model in the sagittal plane. Minimum angle-jerk and minimum jerk trajectories with a via-point were computed for joint angle and COM, respectively. Five to six candidate points were selected as the via-point from the measured trajectory based on the separate kinematic events. The results show the optimal angular trajectories using the via-points (via-angles) before the seat-off for STS, and at around the seat-contact for BTS resembles the measured angular trajectories well, indicating that the posture at the via-point was temporally optimal to produce the minimum angle-jerk trajectory for both movements. It is hypothesized that the multi-joint angular patterns during STS and BTS movements were organized to pass through the via-point, namely the via-posture along the minimum angle-jerk trajectory.

Center of gravity transfer velocity during sit-to-stand is closely related to physical functions regarding fall experience of the elderly living in community dwelling

This study examines the difference of the center of gravity (CG) velocity during sit-to-stand (STS) movement between the elderly with and without fall experience. Fifteen elderly without fall experience (age: 75.7 ± 4.8 yr), with one fall experience (age: 75.7 ± 5.0 yr), and two or more fall experiences (age: 75.7 ± 4.8 yr) participated in the measurement of 10m maximal walking speed, functional reach, one-legged standing duration with vision, maximal isometric knee extension, hip flexion, ankle extension and toe flexion muscle strengths, fall risk assessment and ADL questionnaire, and CG velocity during STS movement. No significant differences were found in muscle strength, walking and balance tests (F 0.078). The group with two or more fall experiences was significantly higher than the other groups in the fall risk assessment, and lower than the group without fall experience in ADL (F = 8.5 and 6.1, p = 0.001 and 0.005). Meanwhile, significant differences were found in the maximal and mean CG velocity during STS movement among all groups. The group without fall experience was the greatest, and the group with fall experience was less than half (F = 9.0 and 11.1, p = 0.001

A Procedure for the Design of Novel Assisting Devices for the Sit-to-Stand

The Sit-to-Stand （STS） is an activity most people perform numerous times daily. Standing up deals with the transition from two stabilized postures, namely seated to standing, with movement of all body segments except the feet. During the STS the body＇s Center of Gravity （COG） is moved upward from a sitting position to a standing position without losing balance and requiring a good coordination of many muscles. Three main phases of the STS movement can be recognized. One begins to stand up by inclining the upper body forward, which moves body mass toward the feet in order to maintain balance after lift-off. Prior to leaving the chair, hip and knee extensor muscles are activated to provide antigravity support for these joints, this action is commonly referred to as ＂weight shift＂. Finally; after leaving the chair, the leg and trunk joints are straightened to achieve upright stance. The STS task can be considered of major importance for impaired and elderly people to achieve minimal mo- bility and independence. In this paper we detail a procedure for the design of assisting devices to be used for the STS. In par- ticular, an experimental procedure is described firstly to track and record point trajectories and the orientation of the trunk during the STS. This analysis is then used to get information for the design of assisting devices. A proposal and simulation results are presented for a novel mechatronic system. In particular, for the case under study experimental tests are used to drive the actua- tion system for the reported simulation. A functional mechatronic scheme is then proposed to control the device during its operation.

Functional Design for Customizing Sit-To-Stand Assisting Devices

Standing up refers to the transition from the seating to the standing postures to perform a movement that involves several body segments and requires both voluntary action and equilibrium control during an important displacement of the body Centre of Gravity （COG）. This task can be considered very important for people with reduced mobility to achieve minimal independence in Activity of Daily Living （ADL）. In this paper, we propose solutions for the homecare of persons with reduced mobility, describing a functional design to customize assisting devices for the Sit-to-Stand （STS）. In particular, the support mechanism that generates the requested motion and sustains the body of a person can be synthesized ad-hoc according to the experimental data of the subject. Experimental tests carried out during the Sit-To-Stand are used to track and record point trajectories and the orientation of the trunk of an individual, and they are used to design a 1-DOF mechanism able to reproduce the assigned rigid-body motion. A four-bar linkage has been synthesized according to the desired features. Simulation results are reported to illustrate the engineering soundness of the proposed mechatronic solution.

Design and Control of an Assistive Device for the Study of the Post-stroke Sit-To-Stand Movement

Every year more than 5 million people worldwide become hemiplegic as a direct consequence of stroke. This neurological deficiency, often leads to a partial or a total loss of standing up abilities and/or ambulation skills. In order to propose new supporting solutions lying between the wheelchair and the walker, this paper presents a technological strategy for designing an assistive device for a biomechanical study of the Sit-To-Stand movement （STS）. The control algorithms are implemented in TwinCAT runtime environment. The communi- cation between the component and the control computer is ensured via the EtherCAT fieldbus. The aim of this architecture lies in the fact that it allows a quick development of a research prototype with the same safety issues found on an industrial machine. An experimental test of the STS strategy is presented and discussed in order to evaluate the strategy.

ANFIS-based Sensor Fusion System of Sit-to-stand for Elderly People Assistive Device Protocols

This paper describes the analysis and design of an assistive device for elderly people under development at the EgyptJapan University of Science and Technology（E-JUST） named E-JUST assistive device（EJAD）.Several experiments were carried out using a motion capture system（VICON） and inertial sensors to identify the human posture during the sit-to-stand motion.The EJAD uses only two inertial measurement units（IMUs） fused through an adaptive neuro-fuzzy inference systems（ANFIS） algorithm to imitate the real motion of the caregiver.The EJAD consists of two main parts,a robot arm and an active walker.The robot arm is a 2-degree-of-freedom（2-DOF） planar manipulator.In addition,a back support with a passive joint is used to support the patient s back.The IMUs on the leg and trunk of the patient are used to compensate for and adapt to the EJAD system motion depending on the obtained patient posture.The ANFIS algorithm is used to train the fuzzy system that converts the IMUs signals to the right posture of the patient.A control scheme is proposed to control the system motion based on practical measurements taken from the experiments.A computer simulation showed a relatively good performance of the EJAD in assisting the patient.