In this paper, we proposed an IMU-based locomotion mode identification (LMI) system for ankle-foot prostheses. Specifically, an IMU sensor was mounted on the heel to collect the foot's dynamic information during walking. Then processing the dynamic data can estimate the foot trajectory for calculating the inclination grade of the terrain. It is noteworthy that our environment is constructed according to the inclination grade for ergonomics. For example, when the inclination angle ranges from 3 degrees to 11 degrees, the environment should be a ramp. On the other hand, when walking on different terrains, people prefer to move their feet around the ground's exterior. It is helpful for people to get the required foot clearance and, at the same time, minimize the energy needed for transporting the lower limbs. Therefore, with the estimated inclination grade, the presented method can precisely predict/identify the locomotion mode. Experimental results show that the average accuracy can reach 98.4% in five daily locomotion modes, including level-ground walking, stair ascending/descending, and upslope/downslope walking. © 2023 SPIE.

Due to low power consumption and fast response, magnetorheological (MR) dampers are widely used in various engineering applications. To enhance the performances, efforts have been made to increase the field dependent force with the same power consumption. However, the fluid viscous force is also increased significantly, which is undesirable in practical use. To tackle this problem, the focus of this paper is to design and test a new MR damper with micro-grooves for performance enhancement. First, the detailed design of the proposed MR damper is provided. A prototype of the new MR damper is fabricated. Silicon steel circular rings with thickness of 0.25 mm are installed around the damper piston to form two-layer micro-grooves. Experimental results of the two MR dampers without and with micro-grooves are then compared. The advantages of MR damper with micro-grooves over the one without micro-grooves are validated. The damping force and controllable force range of MR damper with micro-grooves are larger than the one without micro-grooves. When designing MR damper, making micro-grooves can also decrease the increment of fluid viscous force while keeping the same increase of field dependent force. With micro-grooves, the field dependent force is increased by 92.7% with the same power consumption, while the fluid viscous force is increased by 43%. Copyright © 2020 ASME.

In this paper, the dynamic model of swing phase of the lower limb exoskeleton is firstly established. Based on the proposed model, system identification experiments at each joint are conducted to determine unknown parameters and joint friction torques by tracking desired reference signals. The experimental data are processed by the least squares method. Another validation experiment is taken to verify the accuracy of the estimated model. Both linear and nonlinear controllers are designed. The linear controller is a proportional-derivative (PD) controller, and the nonlinear controller is a PD controller with gravity and friction torque compensation. Experiments show that the transient response of the tracking performance of the nonlinear controller is significantly better than that of the linear controller. © 2019 IEEE.