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Hexapods and Machining Technology
Published in Helmi Youssef, Hassan El-Hofy, Non-Traditional and Advanced Machining Technologies, 2020
The hexapod is a modern technology breakthrough that bridges the gap between robots and machine tools of multi-axis mechanisms that use either orthogonal or rotational movements. The current paradigm in design and manufacturing of hexapods involves integration of numerous hardwares and sophisticated software to create a unique product of extremely high rigidity and accuracy. The objective of this integrated product is to enhance quality and reliability, and to reduce the cost and overall cycle time through the dramatic departure from conventional mechanism design. As development and refinements continue, it is believed that the hexapod will eventually proliferate. A hexapod provides significant benefits to the end-user, since it offers many new attributes for the manufacturing processes.
Human-robot interaction and robots for human society
Published in Arkapravo Bhaumik, From AI to Robotics, 2018
Over the last decade, hexapod rovers has been a raging trend in robot design, R-Hex [130], Mondo Spider, Stiquito and more recently the Erle Spider have left both the hobbyist and the seasoned roboticist spell bound. The anthropomorphic motivation are from lizards and spiders, however instead of strictly adhering to a circular symmetry, designs as Stiquito and R-Hex have employed lateral arrangements of the legs. The R-Hex, as shown in Figure 7.22 and its variations the AQUA project for explorations in oceans and lakes are a novelty of design for scouting unfriendly and unchartered environments. These are a promising improvement over wheeled robots as they do not get stuck in a muddy patch or sand pockets, can walk their way up a sand dune, ramp or stairs and can navigate rugged, broken ground rapidly. Other than surveying, such a hexapod can also be used for surveillance, search and rescue and sensing in remote locations and unforgiving terrains as arid desert or marshy landscape. The R-Hex project was developed with collaboration from five American and one Canadian university and was funded by DARPA and other US agencies. The R-Hex design, with 6 degrees of freedom, a motor for each of the six legs, maneuverability on both land and water and a speed of 2.7 m/s on land, may well be the next best bet for surveying far off planets.
Mathematical Models of Robot Motion
Published in Jitendra R. Raol, Ajith K. Gopal, Mobile Intelligent Autonomous Systems, 2016
The walking problem can be divided into two aspects: (i) the balance control and (ii) the walking sequence control. In balance control, a feedback-force system at each robot’s foot can be implemented to calculate the ZMP and then feed it into the incremental fuzzy PD controller to decrease the ZMP error [1]. The controller’s aim is to adjust the lateral robot’s position to maintain the ZMP point always inside of the support area. The walking sequence control of a biped robot is determined by controlling the hip and foot trajectories [1]. In order to achieve the stable dynamic walking, the change between simple supports walking phase and double supports walking phase should be smooth. One can use the cubic polynomials algorithms to control the sagittal motion to guarantee a smooth change between the walking phases [1]. The robot’s stability at dynamic walking can then be achieved by applying the ZMP criterion in the incremental fuzzy PD controller to guarantee the balance control at walking [1]. The system that acts like two coupled pendula is a simple planar mechanism with two legs that can make walk a robot stably down a slight slope with no other input or control. The stance leg would act like an inverted pendulum, and the swing leg would act like a free pendulum attached to the stance leg at the hip. For a sufficient mass at the hip, the system will have a stable limit cycle. The limit cycle is nominal trajectory that repeats itself and will return to this trajectory even if perturbed slightly. An extension of the two-segment passive walker includes knees that would provide natural ground clearance without any need for additional mechanisms. A hexapod walking robot is a mechanical vehicle that walks on six legs, and since a robot can be statically stable on three or more legs, a hexapod robot has greater flexibility in its movement. The merit is that when it becomes partially disabled it will be able to walk. Since all the six legs of the robot are not needed for stability, the other legs can be used to reach new foot placements or manipulate a payload.
Robust optimization of multi-scenario many-objective problems with auto-tuned utility function
Published in Engineering Optimization, 2021
Typical scenarios are simulated and evaluated in parallel to optimize the control for the intended use of Szabad(ka)-II (multi-scenario property). To the best of the authors' knowledge, there are no specific and applicable definitions for the hexapod robot control problems. The quality description is multi-objective, since the goodness is divided into simpler elements, which are established by common sense and empirical experience: the sum of the gear torques , the acceleration of the robot body , the angular acceleration of the robot body , the consumed electric energy per metre , and the reciprocal of the average walking velocity ( should be minimized). Table 3 in Section 3.3 of the online supplemental data describes these five objective functions in detail.
Design, development, and control of a tough electrohydraulic hexapod robot for subsea operations
Published in Advanced Robotics, 2018
I. Davliakos, I. Roditis, K. Lika, Ch.-M. Breki, E. Papadopoulos
The design, development, and control for an 18 DOF electrohydraulic subsea hexapod robot were presented. The HexaTerra hexapod is designed for trenching and exploration tasks, able to overcome obstacles, slopes, drag, and currents. The leg design was obtained using optimization techniques. A dynamic model of the hexapod was developed using a Lagrangian approach, incorporating a ground model for estimating ground reactions. The electrohydraulic design was based on a worst-case scenario and was implemented with a constant pressure supply driving proportional valves, mounted on a custom manifold design. The components were selected taking into account the leg kinematics and system dynamics, resulting in minimum size, and cost.