​Zefang Shen; Garry Allison; Lei Cui
 J. Mech. Des. 2018; 140(9):092302-092302-12
doi: 10.1115/1.4040486

Exoskeletons are wearable robots developed to assist the wear’s motion. In rehabilitation, such devices can help patients relearn natural motion after surgery, spinal cord injury, stroke, etc. Compared with conventional rehabilitation, exoskeleton-based rehabilitation can provide highly stable and repetitive movements. However most current devices are bulky and heavy, which limits their application in clinical settings. In this paper, we propose a method to design compact and lightweight planar linkages for exoskeletons with multiple output joints, while requiring only one actuator. Candidate linkages are generated and then evaluated to obtain the optimal design of the linkages. Applying this method, we have developed an index finger exoskeleton and a leg exoskeleton for rehabilitation, both of which are compact and portable. Their simplicity in design also increase the affordability for exoskeleton devices, which can facilitate applications outside clinical settings.

​Dielectric elastomers (DEs) may be a more energy efficient, lightweight, and low-cost solution for many emerging mechatronics applications when compared against established actuation technologies (e.g. solenoids or pneumatic cylinders). DE actuators (DEA) are also highly scalable, have low power consumption, and offer high flexibility. The presented work proposes a systematic tool for quasi-static performance prediction of circular out-of-plane DEAs. The method is based on extracting material characteristics (in terms of a stress-strain behavior) from a set of training data. This is then used to calculate the force-displacement characteristic for arbitrary geometries. The method is validated using two different prediction scenarios: blocking force and stroke of various geometries. The prediction errors for stroke and blocking force are not larger than 8.3% and 3.1%, respectively. Additionally, this work demonstrates that the stroke output mainly depends on the electrode ring width, and that it increases linearly. Also, it is shown that the force scales linearly with the average electrode ring circumference. These two parameters can be individually used to tailor DEA stroke and force output. The proposed method can then be used by designers to adopt DEAs for certain applications without the need for complicated FE models or prototyping.