Thermo-osmotic energy conversion (TOEC) technology, developed from membrane distillation, is an emerging method that has the potential of obtaining electricity efficiently from a low-grade heat source but faces the difficult problem of pump power loss. In this study, we build a novel TOEC system with a multistage architecture that can work without pump assistance. The experiment system, made of cheap commercial materials, can obtain a power density of 1.39 ± 0.25 W/m 2 , with a heating temperature of 80 °C, and its efficiency increased linearly with the total stage number. A theory calculation shows that a 30-stage system with a specific membrane and a working pressure of 5.0 MPa can obtain an efficiency of 2.72% with a power density of 14.0 W/m 2 . By a molecular dynamics simulation, it is shown that a high-performance membrane has the potential to work at 40 MPa. This study proves that TOEC technology is a practical and competitive approach to covert low-grade thermal energy into power efficiently.
As the population ages, increasingly more individuals experience ankle disabilities caused by stroke and cerebral palsy. Studies on parallel robots for ankle rehabilitation have been conducted under this circumstance. This paper presents a novel parallel ankle rehabilitation robot with the key features of a simple configuration and actuator nonredundancy. The mechanical design is determined, and a prototype is built. Additionally, inverse position solution is addressed to calculate the workspace of the parallel robot. Jacobian matrices mapping the velocity and force from the active joint space to the task space are derived, and kinetostatic performance indices, namely, motion isotropy, force transfer ratio, and force isotropic radius are defined. Moreover, the inverse dynamic model is presented using the Newton–Euler formulation. Dynamic evaluation index, i.e., dynamic uniformity, is proposed according to the derived Jacobian matrix and inertia matrix. Based on the workspace analysis, the parallel robot demonstrates a sufficient workspace for ankle rehabilitation compared with measured range of motion of human ankle joint complex. The results of the kinetostatic and dynamic performance analysis indicate that the parallel robot possesses good motion isotropy, high force transfer ratio, large force isotropic radius, and relatively uniform dynamic dexterity within most of the workspace, especially in the central part. A numerical example is presented to simulate the rehabilitation process and verify the correctness of the inverse dynamic model. The simplicity and the performance of the proposed robot indicate that it has the potential to be widely used for ankle rehabilitation.
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