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SUMMARYA multimodal actuator was proposed to achieve a more agile power-assisted exoskeleton in uncertain complex walking environments. A power-assisted knee exoskeleton prototype based on a multimodal actuator was constructed. With this multimodal actuator, several modes of operation in the power-assisted knee exoskeleton during a motion cycle are actuated, including series elastic actuation, stiff position control, and energy storage and release. Also, a control strategy for power-assisted knee exoskeleton motion control based on a state machine is developed. The ability of the power-assisted knee exoskeleton to follow human motion was tested, and the results showed that the angle error of the knee exoskeleton followed the human motion is not more than 0.4˚, and the response time error of the knee exoskeleton followed the human motion is not more than 0.2 s.

The lower extremity rehabilitation exoskeleton based on pneumatic muscle actuator was introduced. The gait experiments were implemented, and the biomechanics of human walking were outputted for the design and control of lower rehabilitation exoskeleton. The experiment platform was built based on DSPACE system and the fuzzy adaptive PID controller was applied for the control of lower rehabilitation exoskeleton. The experiment results showed that adding the pre-feedback control based on fuzzy adaptive PID can significantly reduce the time that the system, and the experiment of swing control also showed that a high level of coordination between the user swing motion and the exoskeleton leg.

An elastic actuator is proposed for meeting the knee power-assisted exoskeleton effective drive demand under different walking pattern. The actuator can achieve different motion of power-assisted knee exoskeleton through the motor driving the screw nut, series with spring and combing with the corresponding brake pads, and the motion modes are analyzed. The kinematics equations of elastic actuator were established, and the effects of spring stiffness and damping for the properties of elastic actuator are studied. The prototype of actuator is designed and tested, and braking force and motion following experiments are implanted. The results of experiments showed that the elastic actuator can realize effective braking force and favorable motion following. The study of multi-mode elastic actuator provides important theoretical basis for the understanding of motion mechanism of bionic actuator.

A convenient assembly method for the virtual modular robot is put forward, proposed assembly method does not need the designers to specify explicitly constraint relation of components but rather establish them automatically according to the defined assembly information and the matching algorithm of connectors. The key technology of the assembly method is studied, a hierarchical representation of robot component is proposed to express necessary assembly and simulation information, the 3D picking method of model is realized by introducing a picking ray which takes the viewpoint as a starting point and goes through the clicked point to compensate lack of depth information, as well as the fast matching algorithm based on square area comparison is set up to quickly determine assembly point. Finally, this assembly method is realized with the key technology solved and an application example is given to show its effect.

With the continuous development of society in the recent years, rail traffic has been getting great development and application. As key components of rail traffic, the reliability of metro door system makes great influences on people's safely taking subway. However, in the traditional post maintenance or planned maintenance methods, there are a series of shortcomings like high cost, time consuming, low efficiency, weak pertinence, inappropriate maintenance and so on. So the traditional maintenance method cannot meet the requirements of the real-time monitoring of the running state of the door system. Monitoring the working states of metro door system in real time and predicting faults have a more realistic significance of research. Therefore, a set of remote monitoring system for the running state of the train door system was developed by using LabVIEW. Firstly, the overall design scheme was proposed, and the characteristic parameters that can fully characterize the running state of door system were determined. Secondly, the improved hardware structure of the system were designed in detail in order to realize the function of on-line monitoring and fault diagnosis of the whole door system. Then, related sensors and data acquisition device were reasonably selected and installed and a data acquisition platform for the parameters of the working state of the door system was set up to reasonably collect the parameters that can fully describe the running state of the door system. In order to achieve good remote communication requirements, the remote online monitoring software system of door system was designed based on B/S and C/S mode. Systems of data acquisition and remote monitor of working states for metro door system were lastly developed to easily view data or diagnose faults for engineers, especially for remote experts. Experiments showed that the running performance of both data acquisition and remote monitoring was quite good, which met the initial requirements of the project. At the same time, the system could provide the feedback of the working state of the door system and the maintenance suggestion before the happening of failure, and the incidence of failure could be greatly reduced, in addition, the corresponding historical data could also be viewed, which had a certain engineering application.

A multimodal actuator is proposed to fulfil the different walking patterns of a power-assisted knee exoskeleton. With this actuator, the exoskeleton leg can realize several modes of operation, including series elastic actuation, stiff position control and energy storage and release. The energy amplification characteristics of the multimodal actuator in the series elastic mode are analysed. A dynamics model was established to study how series elasticity and the equivalent mass of transmission influence a power source, such as an electric motor. The results, in both simulation and experiment, show that series elasticity can amplify actuator power output, and the power output of a multimodal actuator is greater when the equivalent mass of the transmission mechanism is smaller. This research into multimodal actuator energy amplification supplies important insights into the design of artificial systems that can more closely approximate the performance of biological systems.

In this paper, we presented a multimodal elastic actuator which combining the motor, spring, brake and clutch that produces several modes of operation. The operation modes including stiff position control, series elastic actuation as well as the possibility to store and release energy were analyzed. A prototype of multimodal elastic actuator was constructed, dynamics equations of elastic actuator were established, and hopping movements with harmonic excitation were studied. Hopping movement was analyzed using receding horizon policy, the elastic actuator was controlled with preloaded hopping, and the hopping simulations with different ground trajectories were studied. The hopping movement simulation study of multimode elastic actuator provides important theoretical basis for the understanding of motion mechanism of bionic actuator and control implementation of hopping movement.

Stair climbing under backpack load condition is a challenging task. Understanding muscle activation patterns of lower limb during stair climbing with load furthers our understanding of the factors involved in joint pathology and the effects of treatment. At the same time, stair climbing under backpack load requires adjustments of muscle activations and increases joint moment compared to level walking, which with muscle activation patterns are altered as a result of using an assistive technology, such as a wearable exoskeleton leg for human walking power augmentation. Therefore, the aim of this study was to analyze lower limb muscles during stair climbing under different backpack load. Nine healthy volunteers ascended a four-step staircase at different backpack load (0 kg, 10 kg, 20 kg, 30 kg). Electromyographic (EMG) signals were recorded from four lower limb muscles (gastrocnemius, tibialis anterior, hamstring, rectus femoris). The results showed that muscle activation amplitudes of lower limb increase with increasing load during stair climbing, the maximum RMS of gastrocnemius are greater than tibialis anterior, hamstring and rectus femoris whether stair climbing or level walking under the same load condition. However, the maximum RMS of hamstring are smaller than gastrocnemius, tibialis anterior and rectus femoris. The study of muscle activation under different backpack load during stair climbing can be used to design biomechanism and explore intelligent control based on EMG for a wearable exoskeleton leg for human walking power augmentation.