Mechanical Design and a Novel Structural Optimization Approach for Hexapod Walking Robots

This paper presents a novel model-based structural optimization approach for the efficient electromechanical development of hexapod robots. First, a hexapod-design-related analysis of both optimization objectives and relevant parameters is conducted based on the derived dynamical model of the robot. A multi-objective optimization goal is proposed, which minimizes energy consumption, unwanted body motion and differences between joint torques. Then, an optimization framework is established, which utilizes a sophisticated strategy to handle the optimization problems characterized by a large set of parameters. As a result, a satisfactory result is efficiently obtained with fewer iterations. The research determines the optimal parameter set for hexapod robots, contributing to significant increases in a robot’s walking range, suppressed robot body vibrations, and both balanced and appropriate motor loads. The modular design of the proposed simulation model also offers flexibility, allowing for the optimization of other electromechanical properties of hexapod robots. The presented research focuses on the mechatronic design of the Szabad(ka)-III hexapod robot and is based on the previously validated Szabad(ka)-II hexapod robot mode

Ex vivo loading of trussed implants for spine fusion induces heterogeneous strains consistent with homeostatic bone mechanobiology

A truss structure was recently introduced as an interbody fusion cage. As a truss system, some of the connected elements may be in a state of compression and others in tension. This study aimed to quantify both the mean and variance of strut strains in such an implant when loaded in a simulated fusion condition with vertebral body or contoured plastic loading platens ex vivo. Cages were each instrumented with 78 fiducial spheres, loaded between platens (vertebral body or contoured plastic), imaged using high resolution micro-CT, and analyzed for deformation and strain of each of the 221 struts. With repeated loading of a cage by vertebral platens, the distribution (variance, indicated by SD) of strut strains widened from 50 N control (4 ± 114 με, mean ± SD) to 1000 N (−23 ± 273 με) and 2000 N (−48 ± 414 με), and between 1000 N and 2000 N. With similar loading of multiple cages, the strain distribution at 2000 N (23 ± 389 με) increased from 50 N control. With repeated loading by contoured plastic platens, induced strains at 2000 N had a distribution similar to that induced by vertebral platens (84 ± 426 με). In all studies, cages exhibited increases in strut strain amplitude when loaded from 50 N to 1000 N or 2000 N. Correspondingly, at 2000 N, 59–64% of struts exhibited strain amplitudes consistent with mechanobiologically-regulated bone homeostasis. At 2000 N, vertically-oriented struts exhibited deformation of −2.87 ± 2.04 μm and strain of −199 ± 133 με, indicating overall cage compression. Thus, using an ex vivo 3-D experimental biomechanical analysis method, a truss implant can have strains induced by physiological loading that are heterogeneous and of amplitudes consistent with mechanobiological bone homeostasis