Exoskeleton robots can help workers prevent musculoskeletal discords (known as industrial exoskeletons) and speed up recovery from human joint injuries (known as rehabilitation exoskeletons). Safety and comfort are basic requirements for industrial and rehabilitation exoskeletons. To ensure safety, the exoskeleton should control the human-robot interaction force within a certain range. To achieve comfort, the exoskeleton should strive to provide assistive forces close to the user’s expectations. Therefore, precise control of the interaction force is a requirement for exoskeleton actuators. In addition, the sensors on an exoskeleton are also closely related to its comfort. Commonly used sensors, such as multi-dimensional force sensors, electromyography sensors (containing metal electrodes) and inertial sensors, all have hard shells made of metal or plastic. When these hard shells come into contact with human skin or even press on the skin, they will cause discomfort.

In this Research Topic, we focus on the work related to elastic actuators (and their control) and flexible sensors that can improve the safety and comfort of exoskeleton robots. Elastic actuators can achieve force/impedance rendering fidelity by introducing springs as the force-sensing elements. However, when springs and related structures are added, the weight and size of elastic actuators are usually much larger than simple motors. Therefore, the design of lightweight elastic actuators remains a challenge. In addition, the trade-off between force fidelity and bandwidth is also an issue in the control of elastic actuators. Utilizing flexible sensors for human-robot interaction has become a popular approach in the field of exoskeletons. For example, fabrics with sensing functions are made into wearable sensors for human-robot interaction. However, the performance of flexible sensors, for example in terms of robustness, still needs to be improved.

The scope of this Research Topic is the new design and control of elastic actuators as well as novel flexible sensors for exoskeleton robots. Accordingly, specific themes for this Research Topic include but are not limited to:

- Design of new elastic actuator for exoskeleton robots.

- Modeling and control approach of elastic actuators.

- Novel force-sensing elements design for elastic actuators.

- Design of new type flexible sensors for exoskeleton robots.

- Theories and modeling of complex nonlinear phenomena relating to flexible sensors.

- Novel assistive strategy based on force control for exoskeleton robots.

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Elastic Actuators and Flexible Sensors for Exoskeleton Robots