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Comprehensive safety
Published in Eduard Fosch-Villaronga, Robots, Healthcare, and the Law, 2019
Jatsun, Savin, and Yatsun (2016) presented at RAAD 2016 a motion control algorithm for exoskeleton push recovery in the frontal plane, which could be useful to ensure stability during the gate life-cycle. Maybe in the future, it would be a requirement for creators to incorporate safety balance algorithms similar to the zero-moment point (ZMP) applied by the Atlas humanoid robot from Boston. These techniques have lately been used to address the dynamic balance in humanoid robots successfully. Although exoskeletons are not humanoid robots, balance and stability are crucial.
Humanoid Robots
Published in Osita D. I. Nwokah, Yildirim Hurmuzlu, The Mechanical Systems Design Handbook, 2017
Miomir Vukobratović, Branislav Borovać, Dragoljub Šurdilović, Dragan Stokić
The above mostly relates to refining the trajectory of the zero-moment point, especially when the gait passes from the single-support to the double-support phase. It is then that the introduction of the semi-rigid foot, in contrast to its rigid version, offers the possibility of a more faithful representation of the perturbation state of the humanoid robot to prevent the robot instantaneously reaching its foot edge — the case that has been considered up to now.
Real-time walking step timing adaptation by restricting duration decision for the first footstep
Published in Advanced Robotics, 2020
Marcos R. O. A. Maximo, Carlos H. C. Ribeiro, Rubens J. M. Afonso
Two of the most successful models are the linear inverted pendulum model (LIPM) [1] and the centroidal dynamics [2]. The Zero Moment Point (ZMP) [3] is the point at which the net moment of the inertial and gravity forces has no horizontal components, such concept plays an important role with respect to gait stability. If the ZMP can be forced to remain within the convex hull of the contact points between the robot and the ground, i.e. the support polygon of the robot, then dynamic stability can be shown to be guaranteed1 [3]. This concept has been successfully employed in the design of controllers for several humanoid robots, among which Nao [4], DARwIn-OP [5], HRP-2 [6], ASIMO [7], and Atlas [8].
Simultaneous bipedal locomotion based on haptics for teleoperation
Published in Advanced Robotics, 2019
D. Kasun Prasanga, Kazuki Tanida, Kouhei Ohnishi, Toshiyuki Murakami
In the Zero Moment Point ZMP-based walking, the stability of the motion of the biped robot is guaranteed if the center of pressure is maintained inside the support polygon. A typical cart table model is shown in Figure 3. An object of mass m is moving on top of a massless table. The table’s base is comparatively smaller than the top surface, so that it will fall by turning unless the object has acceleration [31]. The following equation can be obtained by taking the moments around the origin.
Motion analysis of a multi-joint system with holonomic constraints using Riemannian distance
Published in Advanced Robotics, 2022
Masahiro Sekimoto, Suguru Arimoto
To evaluate the dynamic features of walking, basic physical quantities, such as mechanical energy, work, power, ground-reaction force, and joint torque are conventionally adopted in robotics [1–7], and physiology [8, 9]. The notion of zero moment point (ZMP) [10] has been actively studied by biped-robot researchers as a key technique to evaluate the risk of falling. In addition, the orbital energy [6] and capture point [7] have been employed to evaluate the stability during the support foot exchange. Unlike the evaluation of falling, a stable limit cycle of robot motion has been studied to evaluate gait repeatability in passive dynamic walking [11, 12]. The limit cycle corresponds to the natural robot gait on a shallow slope. These findings have facilitated level-ground walking with minimal power injection from actuators [13, 14]. In these studies, the transportation cost, which was defined as (used energy)/(weight × traveled distance), was adopted to compare the gait efficiency. In powered exoskeleton and prosthetic walking [15–17], ground reaction force, joint torque, joint power, and electromyogram (EMG) signals have been employed to evaluate the body weight support. In addition, metabolic costs (oxygen uptake, carbon dioxide output, and heart rate) have been analyzed to evaluate the gait energy efficiency [18, 19]. The aforementioned evaluation quantities have also been used in pure human walking studies [8, 9]. From the perspective of walking efficiency, the pendular movements of human body segments have long garnered the interest of physiologists. The total mechanical energy of the trunk at a certain speed (5 km/h) fluctuated slightly, and the kinetic and potential energies changed synchronously in opposite directions (p. 493 in [8]). In human walking with head-supported loads, the pendulum-like transfer between the potential and kinetic energies of the center-of-mass (COM) during each step has contributed to the decrease in work [20]. As another approach, rocker behaviors obtained by rolling contacts of the sole stance have contributed to shock absorption at ground contact and COM forward motions [9]. As far as the authors surveyed, employing the proximity to the inertia movement is quite unique in both robot and human walking. This quantity can also be used to evaluate the collaborative human-machine motion, as seen in powered exoskeletons and prosthetic walking. Note that this quantity does not correspond to the evaluation of the zero-driving motion under gravity, unlike the pendulum-like energy transfer.