As a reinforcement technology that improves load-bearing ability and prevents injuries, assisted exoskeleton robots have extensive applications in freight transport and health care. The perception of gait information by such robots is vital for their control. This information is the basis for motion planning in assistive and collaborative functions. Here, a wearable gait recognition sensor system for exoskeleton robots is presented. Pressure sensor arrays based on laser-induced graphene are developed with flexibility and reliability. Multiple sensor units are integrated into an insole to detect real-time pressure at key plantar positions. In addition, the circuit hardware and the algorithm are designed to reinforce the sensor system with the capability of gait recognition. The experimental results show that the accuracy of gait recognition by the proposed system is 99.85%, and the effectiveness of the system is further verified through testing on an exoskeleton robot.

The practical long-term application of power-assisted exoskeleton robots requires lightweight, high-efficient, and high-control precision actuators. Based on the improvement of hardware design and control method, this article proposes a complete drive solution for the joint drive of exoskeleton robots and promotes the research of robot joint drive based on the pump-controlled hydraulic system. Specifically, a compact, backdrivable, and energy-efficient drive unit, lightweight electrohydrostatic actuator (LEHA) with a weight of 2.5 kg and a rated power of 340 W is designed first. Then, by combining the fifth-order high-precision dynamics model of LEHA and virtual decomposition control method, a high-performance controller with $L_{2}$ and $L_{\infty }$ stability is developed to realize the precise position trajectory tracking control of LEHA. Experimental results based on actual exoskeleton robot knee joints show that the proposed solution has high trajectory tracking performance over the frequency range of human body swing phase motion (0.5–1.5 Hz) and different loads (0–20 kg). Moreover, compared with the valve-controlled hydraulic power system with the same exoskeleton robot knee joint and wearer, test results show that the average efficiency increased by 18.13% after using LEHA under the swing phase test.

Flow mismatch, strong nonlinearity, and complex disturbance are the main challenges that electro-hydrostatic actuator (EHA) control faces. This article proposes a three-port piston pump to replace the two-port piston pump in traditional EHA to solve the flow mismatch problem caused by asymmetric cylinders. Then, for the complex disturbance problem in EHA control, an extended state observer and a nonlinear disturbance observer are designed to estimate matched and mismatched disturbances, respectively. On this basis, the virtual decomposition control method is adopted. The EHA is virtually decomposed into three subsystems, and the controllers of each subsystem are designed separately to realize the high-precision nonlinear control of the EHA. Next, the stability of the proposed control method and observer is proved. Finally, the proposed three-port pump, observer, and controller are systematically verified based on the simulation model and the EHA experimental platform. Simulation and experimental results show that the proposed three-port pump solves the flow mismatch problem without increasing the weight and volume of the EHA. The designed two observers can accurately estimate the matching and mismatching disturbances during the EHA operation. By combining designed observers and the virtual decomposition control method, the accuracy and robustness of EHA control can be greatly improved.

The hydraulic exoskeleton is one research hotspot in the field of robotics, which can take heavy load due to the high power density of the hydraulic system. However, the traditional hydraulic system is normally centralized, inefficient, and bulky during application, which limits its development in the exoskeleton. For improving the robot’s performance, its hydraulic actuating system should be optimized further. In this paper a novel hydraulic actuating system (HAS) based on electric-hydrostatic actuator is proposed, which is applied to hip and knee joints. Each HAS integrates an electric servo motor, a high-speed micro pump, a specific tank, and other components into a module. The specific parameters are obtained through relevant simulation according to human motion data and load requirements. The dynamic models of the HAS are built, and validated by the system identification. Experiments of trajectory tracking and human-exoskeleton interaction are carried out, which demonstrate the proposed HAS has the ability to be applied to the exoskeleton. Compared with the previous prototype, the total weight of the HAS in the robot is reduced by about 40%, and the power density is increased by almost 1.6 times.

Nonconvergence is a frequent problem for mixed lubrication modeling of reciprocating seals, which couples a finite element analysis (FEA) commercial software with the fluid–structure interaction (FSI) procedure. Local refinement of the contact zone helps convergence, but this is time-consuming and requires extra skills for the mesh procedure. This article presents a mixed lubrication model based on a developed multiple-grid method to investigate the combined seal at different system pressures. This method does not require local refinement of the sealing zone. The position of the start point of the sealing zone changes and is renewed after the film thickness computational procedure. To avoid resolving unreasonable equations during the iteration, the cavitation state was updated with the relaxation of the cavitation length rather than the cavitation index parameter. The frictional performance of the combined seal with a backup ring at different system pressures was analyzed and compared with the experiments. The results of the simulation agree with the experimental results.