Integrated design of a lower limb rehabilitation mechanism using differential evolution

In the last years, one degree of freedom mechanisms has been incorporated into rehabilitation machines. Their designs usually involve kinematic synthesis leaving aside their complex dynamic nature. An integrated methodology to design a one degree of freedom eight-bar mechanism for lower limb rehabilitation is presented in this paper. The methodology simultaneously considers kinematic synthesis, structure shape design, and dynamic performance. A non-linear constrained dynamic optimization problem is proposed where the design objective relates the accuracy in the prescribed movement and the energy consumption reduction. This problem is solved by using different differential evolution variants for finding the most suitable synergistic solution. The results show that the obtained design can follow the path with 52.13% less energy consumption compared to a design that does not consider such integration. This also results in less control effort, and hence the velocity regulation accuracy is improved. The three-dimensional printed prototype illustrates the obtained solution.