Powered orthosis for lower limb movements assistance and rehabilitation

This paper presents two rehabilitation approaches of the lower limb: passive and active. The passive one ensures repetitive motions of the limb without any effort delivered by the wearer. Within the active one, a human–exoskeleton interaction approach is proposed. It allows us to provide a knee joint torque support, adapted according to the intention and ability of the wearer, for assistance-as-needed. The wearer׳s intention is estimated using a realistic model of the muscles actuating the knee joint. The identification process concerns the inertial parameters of the shank-foot-exoskeleton and the musculotendinous parameters. Experiments were conducted online on a healthy subject and have shown satisfactory results in terms of tracking error, intention detection and passive-rehabilitation/active-assistance.     

基于柔性气压驱动器的可穿戴式腰部助力机器人研究

针对老龄化社会对于康复和看护助力搬运的需要,提出了用气压驱动器实现轻量、柔性助力、穿戴舒适的可穿戴式腰部助力机器人.机器人采用无外骨骼的结构设计,可以给护理人员在提升重物和静态保持作业时输出腰部所需助力,降低下腰痛（Low back pain,LBP）致病风险.通过对重物搬运作业中穿戴者竖脊肌表面肌电信号（Surface electromyography,sEMG）评估、基于测力平台最大搬举重量测试、静态弯腰负重作业下人体重心（Center of gravity,COG）移动轨迹等相关实验,验证了助力有效性.     

A generalized control framework of assistive controllers and its application to lower limb exoskeletons

Various control methods have been studied for the natural assistance of human motions by exoskeletal robots, i.e., wearable robots for assisting the human motions. For example, impedance control and compliance control are widely used for controlling interaction forces between a human and a robot. When an accurate measurement of the human muscular force is available (e.g., electromyography), a direct use of the estimated human joint torque is possible in the control of an assistive robot. The human motions in a daily living, however, are so complex that they are constituted by multiple phases, such as walking, sitting, and standing, where the walking can be further categorized into multiple sub-phases. Therefore, a single control method cannot be the best option for all the motion phases; a switch in the control algorithms may be necessary for assisting human movements in multiple motion phases. In this paper, a generalized control framework is proposed to incorporate the various assistive control methods in one general controller structure, which consists of Feedforward Disturbance Compensation Control, Reference Tracking Feedback Control, Reference Tracking Feedforward Control, Model-based Torque Control. The proposed control framework is designed taking into consideration of the linearity of each control algorithm, and thus it enables the continuous and smooth switching of assistive control algorithms, and makes it possible to analyze the stability of the overall control loop. The proposed method is implemented into a lower-limb exoskeleton robot and is verified by experimental results.     

Level-ground walking for a bipedal robot with a torso via hip series elastic actuators and its gait bifurcation control

Recent studies have shown that a bipedal robot with a torso supported by springs on the hip can have a stable passive gait on a slope, while such a robot walking on level ground is a new challenge and has rarely been studied. This research adds actuators in series with the springs to form series elastic actuators on the hip and applies a state machine as controller to achieve stable walking on level ground. During walking, hip series elastic actuators support the torso from the legs as well as complement the energy to the system via elastic potential energy. The state machine uses the landing impact of the swing leg and the actuation durations as events to make the robot switch between successive active and passive walking processes. Because this simple scheme makes full use of the dynamics of the robot, it can lead to an efficient and natural gait. By means of numerical simulation, in addition to the stable period-1 gait, we found a variety of gait bifurcation phenomena, including the period-doubling bifurcation, the Neimark–Sacker bifurcation, the Neimark–Sacker-2 bifurcation, the period-X bifurcation, and the Neimark–Sacker-X bifurcation, among which many types have never been reported in previous studies. We also show that the unstable period-1 gait embedded in the bifurcation gait can be stabilized by applying the Ott–Grebogi–Yorke method. Not only can the gait bifurcation be suppressed, but also higher gait performance can be achieved.     

Mechanisms for actuated assistive hip orthoses

Mobility is often a central problem for people having muscle weaknesses. The need for new devices to assist walking and walk related activities is therefore growing. Lower limb actuated orthoses have already proven their positive impact with paraplegic patients and are potentially promising for assisting people with weak muscles. However, the transfer from the existing systems of mobilization towards assistance implies several technical challenges as the seamless integration and the reduction of power consumption. In this paper two assistive orthoses which use different types of actuation mechanisms are presented and discussed. The first one is based on a ball screw and an excavator-like mechanism while the second one is based on a double differential actuation. Their technical capabilities are compared and contextualized for diverse activities. Objective characteristics such as the range of motion of the devices, the transparency, the maximal torque that they can provide or the RMS torque during cyclic trajectories are compared to point out which device is better adapted for specific situations.     

Modeling of natural sit-to-stand movement based on minimum jerk criterion for natural-like assistance and rehabilitation

Designing a sit-to-stand (STS) assistive system that mimics the normal transfer is important for improving the quality of life for elderly and mobility impaired people while reducing the burden on the caregivers. This paper presents a robotic-based STS assisting system that can provide assistance at the shoulder and the buttock. The minimum jerk criterion is used to model the natural STS motion. Anthropometry and characteristics of the natural STS motion are used to increase the simplicity and applicability of the STS motion model. This model can generate the shoulder and hip trajectories during STS. This enables the system to provide assistance either at the upper trunk or at the upper trunk and the hip simultaneously without inducing abnormal motion kinematics. The assisting system is used to assist subjects with different heights using the trajectories generated by the proposed motion model. In addition, the proposed trajectory is compared to the one that is resulted from a commercial lifter. The results show that the proposed method can accurately replicate the natural STS motion and results in a lower interaction force. Moreover, the subjects are more satisfied when they are assisted using the proposed method as indicated by the results of the post-experiment questionnaire.