scholarly journals Control of Thruster-Assisted, Bipedal Legged Locomotion of the Harpy Robot

2021 ◽  
Vol 8 ◽  
Author(s):  
Pravin Dangol ◽  
Eric Sihite ◽  
Alireza Ramezani
Keyword(s):  
Constraint Satisfaction ◽  
Legged Locomotion ◽  
Ground Contact ◽  
Bipedal Robot ◽  
Gait Stability ◽  
External Perturbations ◽  
Environmental Interactions ◽  
Frontal Dynamics ◽  
Reference Trajectories ◽  
High Computational Complexity

Fast constraint satisfaction, frontal dynamics stabilization, and avoiding fallovers in dynamic, bipedal walkers can be pretty challenging. The challenges include underactuation, vulnerability to external perturbations, and high computational complexity that arise when accounting for the system full-dynamics and environmental interactions. In this work, we study the potential roles of thrusters in addressing some of these locomotion challenges in bipedal robotics. We will introduce a thruster-assisted bipedal robot called Harpy. We will capitalize on Harpy’s unique design to propose an optimization-free approach to satisfy gait feasibility conditions. In this thruster-assisted legged locomotion, the reference trajectories can be manipulated to fulfill constraints brought on by ground contact and those prescribed for states and inputs. Unintended changes to the trajectories, especially those optimized to produce periodic orbits, can adversely affect gait stability and hybrid invariance. We will show our approach can still guarantee stability and hybrid invariance of the gaits by employing the thrusters in Harpy. We will also show that the thrusters can be leveraged to robustify the gaits by dodging fallovers or jumping over large obstacles.

scholarly journals Walking Trajectory Optimization With Rotation of the Feet for a Planar Bipedal Robot With Four-Bar Knees

2012 ◽  
Author(s):  
Arnaud Hamon ◽  
Yannick Aoustin
Keyword(s):  
Knee Joint ◽  
Trajectory Optimization ◽  
The Other ◽  
Bipedal Robot ◽  
Double Support ◽  
Walking Gait ◽  
Parametric Optimization Problem ◽  
Four Bar Linkage ◽  
Reference Trajectories ◽  
Support Phase

The design of a knee joint is a key issue in robotics and biomechanics to improve the compatibility between prosthesis and human movements and to improve the bipedal robot performances. We propose a novel design for the knee joint of a planar bipedal robot, based on a four-bar linkage. The dynamic model of the planar bipedal robot is calculated. We design walking reference trajectories with double support phases, single supports with a flat contact of the foot in the ground and single support phases with rotation of the foot around the toe. During the double support phase, both feet rotate. This phase is ended by an impact on the ground of the toe of one foot, the other foot taking off. The single support phase is ended by an impact of the swing foot heel, the other foot keeping contact with the ground through its toe. For both gaits, the reference trajectories of the rotational joints are prescribed by polynomial functions in time. A parametric optimization problem is presented for the determination of the parameters corresponding to the optimal cyclic walking gaits. The main contribution of this paper is the design of a dynamical stable walking gait with double support phases with feet rotation, impacts and single support phases for this novel bipedal robot.

scholarly journals A Control Framework for Anthropomorphic Biped Walking Based on Stabilizing Feedforward Trajectories

2016 ◽  
Author(s):  
Siavash Rezazadeh ◽  
Robert D. Gregg
Keyword(s):  
Stable Limit Cycle ◽  
Humanoid Robots ◽  
Stable Limit ◽  
Dynamic Walking ◽  
Bipedal Robots ◽  
Bipedal Robot ◽  
External Perturbations ◽  
Control Framework ◽  
Zero Moment ◽  
The Stability

Although dynamic walking methods have had notable successes in control of bipedal robots in the recent years, still most of the humanoid robots rely on quasi-static Zero Moment Point controllers. This work is an attempt to design a highly stable controller for dynamic walking of a human-like model which can be used both for control of humanoid robots and prosthetic legs. The method is based on using time-based trajectories that can induce a highly stable limit cycle to the bipedal robot. The time-based nature of the controller motivates its use to entrain a model of an amputee walking, which can potentially lead to a better coordination of the interaction between the prosthesis and the human. The simulations demonstrate the stability of the controller and its robustness against external perturbations.

scholarly journals Rules to limp by: joint compensation conserves limb function after peripheral nerve injury

2013 ◽  
Vol 9 (5) ◽  
pp. 20130484 ◽  
Author(s):  
Jay M. Bauman ◽  
Young-Hui Chang
Keyword(s):  
Peripheral Nerve ◽  
Nerve Injury ◽  
Peripheral Nerve Injury ◽  
Legged Locomotion ◽  
Rodent Models ◽  
Joint Angles ◽  
External Perturbations ◽  
Extensor Muscles ◽  
Level Function ◽  
Neuromechanical Control

Locomotion persists across all manner of internal and external perturbations. The objective of this study was to identify locomotor compensation strategies in rodent models of peripheral nerve injury. We found that hip-to-toe limb length and limb angle was preferentially preserved over individual joint angles after permanent denervation of rat ankle extensor muscles. These findings promote further enquiry into the significance of limb-level function for neuromechanical control of legged locomotion.

START, STOP AND TRANSITION OF VELOCITIES OF AN UNDER-ACTUATED BIPEDAL ROBOT WITHOUT REFERENCE TRAJECTORIES

2004 ◽  
Vol 01 (02) ◽  
pp. 349-374 ◽  
Author(s):  
CHRISTOPHE SABOURIN ◽  
OLIVIER BRUNEAU ◽  
JEAN-GUY FONTAINE
Keyword(s):  
Control Strategy ◽  
The Other ◽  
Dynamic Walking ◽  
Bipedal Robot ◽  
Maximum Torque ◽  
On Line ◽  
Real Robot ◽  
The One ◽  
Technological Limitations ◽  
Reference Trajectories

In this paper, we propose a control strategy allowing us to perform the transition of velocities included in [0 m/s; 1 m/s] for the dynamic walking of a virtual under-actuated robot (RABBIT) without reference trajectories. This strategy of control enables us to carry out the transition from stop towards walking and the reverse process. The interest of this method is that, on the one hand, the intrinsic dynamics of the system are exploited by using a succession of active and passive phases and, on the other hand, the control strategy is very simple to implement on-line. Moreover, we apply this method by taking into account the technological limitations related to experimentation on the real robot such as dry and viscous frictions, maximum torque, and maximum power.

Stress fields in granular material and implications for performance of robot locomotion over granular media

2015 ◽  
Vol 8 (1) ◽  
pp. 2005-2009
Author(s):  
Diandong Ren ◽  
Lance M. Leslie ◽  
Congbin Fu
Keyword(s):  
Mechanical Properties ◽  
Granular Material ◽  
Granular Media ◽  
Rotation Frequency ◽  
Legged Locomotion ◽  
Working Environment ◽  
Navier Stokes ◽  
Maximum Speed ◽  
Sigmoid Curve ◽  
Multi Body

 Legged locomotion of robots has advantages in reducing payload in contexts such as travel over deserts or in planet surfaces. A recent study (Li et al. 2013) partially addresses this issue by examining legged locomotion over granular media (GM). However, they miss one extremely significant fact. When the robot’s wheels (legs) run over GM, the granules are set into motion. Hence, unlike the study of Li et al. (2013), the viscosity of the GM must be included to simulate the kinematic energy loss in striking and passing through the GM. Here the locomotion in their experiments is re-examined using an advanced Navier-Stokes framework with a parameterized granular viscosity. It is found that the performance efficiency of a robot, measured by the maximum speed attainable, follows a six-parameter sigmoid curve when plotted against rotating frequency. A correct scaling for the turning point of the sigmoid curve involves the footprint size, rotation frequency and weight of the robot. Our proposed granular response to a load, or the ‘influencing domain’ concept points out that there is no hydrostatic balance within granular material. The balance is a synergic action of multi-body solids. A solid (of whatever density) may stay in equilibrium at an arbitrary depth inside the GM. It is shown that there exists only a minimum set-in depth and there is no maximum or optimal depth. The set-in depth of a moving robot is a combination of its weight, footprint, thrusting/stroking frequency, surface property of the legs against GM with which it has direct contact, and internal mechanical properties of the GM. If the vehicle’s working environment is known, the wheel-granular interaction and the granular mechanical properties can be grouped together. The unitless combination of the other three can form invariants to scale the performance of various designs of wheels/legs. Wider wheel/leg widths increase the maximum achievable speed if all other parameters are unchanged.

Genetic and Environmental Interactions Affecting Weaning Weights of Hereford Calves

1966 ◽  
Vol 25 (3) ◽  
pp. 779-782 ◽  
Author(s):  
G. O. Harwin ◽  
J. S. Brinks ◽  
H. H. Stonaker
Keyword(s):  
Environmental Interactions
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