Energetic and Dynamic Analysis of Multifrequency Legged Robot Locomotion With an Elastically Suspended Load

2013 ◽  
Vol 9 (2) ◽  
Author(s):  
Xingye Da ◽  
Jeffrey Ackerman ◽  
Justin Seipel
Keyword(s):  
Natural Frequency ◽  
Average Power ◽  
Legged Locomotion ◽  
Suspended Load ◽  
Experimental Results ◽  
Energetic Cost ◽  
Legged Robot ◽  
Multiple Frequency ◽  
Robot Locomotion ◽  
Suspended Loads

Elastically suspended loads can reduce the energetic cost and peak forces of legged robot locomotion. However, legged locomotion frequently exhibits multiple frequency modes due to variable leg contact times, body pitch and roll, and transient locomotion dynamics. We used a simple hexapod robot to investigate the effect of multiple frequency components on the energetic cost, dynamics, and peak forces of legged robot locomotion using a high-speed motion tracking system and the fast Fourier transform (FFT). The trajectories of the robot body and the suspended load revealed that the robot was excited by both a body pitching frequency and the primary locomotion frequency. Both frequency modes affected the dynamics of the legged robot as the natural frequency of the elastic load suspension was varied. When the natural frequency of the load suspension was reduced below the primary locomotion and body pitching frequencies, the robot consumed less average power with an elastically suspended load versus a rigidly attached load. To generalize the experimental results more broadly, a modified double-mass coupled-oscillator model with experimental parameters was shown to qualitatively predict the energetic cost and dynamics of legged robot locomotion with an elastically suspended load. The experimental results and the theoretical model could help researchers better understand locomotion with elastically suspended loads and design load suspension systems that are optimized to reduce the energetic cost and peak forces of legged locomotion.

Energy Efficiency of Legged Robot Locomotion With Elastically-Suspended Loads Over a Range of Suspension Stiffnesses

2012 ◽  
Author(s):  
Jeffrey Ackerman ◽  
Xingye Da ◽  
Justin Seipel
Keyword(s):  
Energy Efficiency ◽  
Simple Model ◽  
Energy Cost ◽  
Legged Locomotion ◽  
Experimental Results ◽  
Legged Robot ◽  
Robot Locomotion ◽  
Cost Of Locomotion ◽  
Energy Cost Of Locomotion ◽  
Suspended Loads

Elastically suspending a load from humans and animals can increase the energy efficiency of legged locomotion and load carrying. Similarly, elastically-suspended loads have the potential to increase the energy efficiency of legged robot locomotion. External loads and the inherent mass of a legged robot, such as batteries, electronics, and fuel, can be elastically-suspended from the robot chassis with a passive compliant suspension system, reducing the energetic cost of locomotion. In prior work, we developed a simple model to examine the effect of elastically-suspended loads on the energy cost of locomotion from first principles. In this paper, we present experimental results showing the energy cost of locomotion for a simple hexapod robot over a range of suspension stiffness values. Elastically-suspended loads were shown to reduce the energy cost of locomotion by up to 20% versus a rigidly-attached load. We compare the experimental results to the theoretical results predicted by the simple model.

Actuated Slip Model of Human Running With an Elastically-Suspended Load

2013 ◽  
Author(s):  
Karna Potwar ◽  
Jeffrey Ackerman ◽  
Justin Seipel
Keyword(s):  
Human Body ◽  
Suspended Load ◽  
The Body ◽  
Stride Frequency ◽  
Energetic Cost ◽  
Slip Model ◽  
Inverted Pendulum Model ◽  
Suspension Stiffness ◽  
Human Running ◽  
Suspended Loads

An elastically-suspended load can reduce the peak forces acting on the body and the energetic cost of human walking compared to a rigidly-attached load. However, limited knowledge exists on how elastically-suspended loads affect the biomechanics of human running. We develop a variant of an Actuated SLIP (Spring Loaded Inverted Pendulum) model to analyze human running with an elastically-suspended load. This model consists of a suspended load attached to the body mass of an Actuated SLIP model with approximate human parameters. The model enables the investigation of the coupled dynamics of the load and the human body and shows that the stride frequency of running is affected by the load suspension stiffness. The model also shows that the peak forces of the load acting on the body are reduced compared to a rigidly-attached load when the load suspension stiffness is minimized. However, the energetic cost of running with an elastically-suspended load is shown to increase compared to a rigidly-attached load. Further, the peak forces and the energetic cost of running are maximized when the natural frequency of the load suspension is tuned near the stride frequency. This model could lead to a better understanding of human running with elastically-suspended loads and may enable the design of load suspension systems that are optimized to reduce stress on the human body while running with a load.

scholarly journals Getting grip in changing environments: the effect of friction anisotropy inversion on robot locomotion

2021 ◽  
Vol 127 (5) ◽  
Author(s):  
Halvor T. Tramsen ◽  
Lars Heepe ◽  
Jettanan Homchanthanakul ◽  
Florentin Wörgötter ◽  
Stanislav N. Gorb ◽  
...  
Keyword(s):  
Energy Efficient ◽  
Legged Locomotion ◽  
Hexapod Robot ◽  
Friction Anisotropy ◽  
Anisotropic Friction ◽  
Walking Behavior ◽  
Robot Locomotion ◽  
Computational Morphology ◽  
Anisotropic Structures ◽  
Walking Environment

AbstractLegged locomotion of robots can be greatly improved by bioinspired tribological structures and by applying the principles of computational morphology to achieve fast and energy-efficient walking. In a previous research, we mounted shark skin on the belly of a hexapod robot to show that the passive anisotropic friction properties of this structure enhance locomotion efficiency, resulting in a stronger grip on varying walking surfaces. This study builds upon these results by using a previously investigated sawtooth structure as a model surface on a legged robot to systematically examine the influences of different material and surface properties on the resulting friction coefficients and the walking behavior of the robot. By employing different surfaces and by varying the stiffness and orientation of the anisotropic structures, we conclude that with having prior knowledge about the walking environment in combination with the tribological properties of these structures, we can greatly improve the robot’s locomotion efficiency.

Vibration Characteristics of Rotating Thin Disks—Part I: Experimental Results

2012 ◽  
Vol 79 (4) ◽  
Author(s):  
Ramin M. H. Khorasany ◽  
Stanley G. Hutton
Keyword(s):  
Frequency Response ◽  
Natural Frequency ◽  
Linear Theory ◽  
Lateral Force ◽  
Vibration Characteristics ◽  
Experimental Results ◽  
Rotating Disks ◽  
Critical Speeds ◽  
Applied Forces ◽  
Thin Disks

Analysis of the linear vibration characteristics of unconstrained rotating isotropic thin disks leads to the important concept of “critical speeds.” These critical rotational speeds are of interest because they correspond to the situation where a natural frequency of the rotating disk, as measured by a stationary observer, is zero. Such speeds correspond physically to the speeds at which a traveling circumferential wave, of shape corresponding to the mode shape of the natural frequency being considered, travel around the disk in the absence of applied forces. At such speeds, according to linear theory, the blade may respond as a space fixed stationary wave and an applied space fixed dc force may induce a resonant condition in the disk response. Thus, in general, linear theory predicts that for rotating disks, with low levels of damping, large responses may be encountered in the region of the critical speeds due to the application of constant space fixed forces. However, large response invalidates the predictions of linear theory which has neglected the nonlinear stiffness produced by the effect of in-plane forces induced by large displacements. In the present paper, experimental studies were conducted in order to measure the frequency response characteristics of rotating disks both in an idling mode as well as when subjected to a space fixed lateral force. The applied lateral force (produced by an air jet) was such as to produce displacements large enough that non linear geometric effects were important in determining the disk frequencies. Experiments were conducted on thin annular disks of different thickness with the inner radius clamped to the driving arbor and the outer radius free. The results of these experiments are presented with an emphasis on recording the effects of geometric nonlinearities on lateral frequency response. In a companion paper (Khorasany and Hutton, 2010, “Vibration Characteristics of Rotating Thin Disks—Part II: Analytical Predictions,” ASME J. Mech., 79(4), p. 041007), analytical predictions of such disk behavior are presented and compared with the experimental results obtained in this study. The experimental results show that in the case where significant disk displacements are induced by a lateral force, the frequency characteristics are significantly influenced by the magnitude of forced displacements.

A Simple Analytical Tool for Legged Robot Design

2012 ◽  
Author(s):  
Zhuohua Shen ◽  
Justin Seipel
Keyword(s):  
Analytical Solutions ◽  
Inverted Pendulum ◽  
Legged Locomotion ◽  
Robot Design ◽  
Slip Model ◽  
Legged Robot ◽  
Biologically Relevant ◽  
Analytical Approximations ◽  
Energy Conserving ◽  
Spring Loaded Inverted Pendulum

Although legged locomotion is better at tackling complicated terrains compared with wheeled locomotion, legged robots are rare, in part, because of the lack of simple design tools. The dynamics governing legged locomotion are generally nonlinear and hybrid (piecewise-continuous) and so require numerical simulation for analysis and are not easily applied to robot designs. During the past decade, a few approximated analytical solutions of Spring-Loaded Inverted Pendulum (SLIP), a canonical model in legged locomotion, have been developed. However, SLIP is energy conserving and cannot predict the dynamical stability of real-world legged locomotion. To develop new analytical tools for legged robot designs, we first analytically solved SLIP in a new way. Then based on SLIP solution, we developed an analytical solution of a hip-actuated Spring-Loaded Inverted Pendulum (hip-actuated-SLIP) model, which is more biologically relevant and stable than the canonical energy conserving SLIP model. The analytical approximations offered here for SLIP and the hip actuated-SLIP solutions compare well with the numerical simulations of each. The analytical solutions presented here are simpler in form than those resulting from existing analytical approximations. The analytical solutions of SLIP and the hip actuated-SLIP can be used as tools for robot design or for generating biological hypotheses.

Biologically inspired motion synthesis method of two-legged robot with compliant feet

Robotica ◽  
2011 ◽  
Vol 29 (7) ◽  
pp. 1049-1057 ◽  
Author(s):  
Teresa Zielinska ◽  
Andrzej Chmielniak
Keyword(s):  
Central Pattern Generator ◽  
Coupled Oscillators ◽  
Synthesis Method ◽  
Pattern Generator ◽  
Experimental Results ◽  
Human Gait ◽  
Legged Robot ◽  
Biologically Inspired ◽  
Reference Pattern ◽  
Periodic Signals

SUMMARYThis work presents biologically inspired method of gait generation. It uses the reference to the periodic signals generated by biological central pattern generator. The coupled oscillators with correction functions are used to produce leg joint trajectories. The human gait is the reference pattern. The features of generated gait are compared to the human walk. The spring-loaded foot design is presented together with experimental results.

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