scholarly journals A Bio-Inspired Compliance Planning and Implementation Method for Hydraulically Actuated Quadruped Robots with Consideration of Ground Stiffness

Sensors ◽  
2021 ◽  
Vol 21 (8) ◽  
pp. 2838
Author(s):  
Xiaoxing Zhang ◽  
Haoyuan Yi ◽  
Junjun Liu ◽  
Qi Li ◽  
Xin Luo
Keyword(s):  
Harmonic Oscillation ◽  
Ground Surface ◽  
Legged Locomotion ◽  
Soft Ground ◽  
Quadruped Robots ◽  
In Series ◽  
Reaction Forces ◽  
Implementation Method ◽  
The Stability ◽  
Natural Dynamics

There has been a rising interest in compliant legged locomotion to improve the adaptability and energy efficiency of robots. However, few approaches can be generalized to soft ground due to the lack of consideration of the ground surface. When a robot locomotes on soft ground, the elastic robot legs and compressible ground surface are connected in series. The combined compliance of the leg and surface determines the natural dynamics of the whole system and affects the stability and efficiency of the robot. This paper proposes a bio-inspired leg compliance planning and implementation method with consideration of the ground surface. The ground stiffness is estimated based on analysis of ground reaction forces in the frequency domain, and the leg compliance is actively regulated during locomotion, adapting them to achieve harmonic oscillation. The leg compliance is planned on the condition of resonant movement which agrees with natural dynamics and facilitates rhythmicity and efficiency. The proposed method has been implemented on a hydraulic quadruped robot. The simulations and experimental results verified the effectiveness of our method.

scholarly journals Passive Dynamic Bounding Control using Symmetry Condition Control Laws

2019 ◽  
pp. 451-457
Author(s):  
P. Murali Krishna ◽  
R. Prasanth Kumar
Keyword(s):  
Fixed Points ◽  
Initial Conditions ◽  
Legged Locomotion ◽  
Zero Energy ◽  
Additional Energy ◽  
Control Laws ◽  
Quadruped Robots ◽  
Existence And Stability ◽  
The Stability ◽  
Bounding Gait

Legged locomotion is preferred over the wheeled locomotion as it can be used both for flat and rough terrains. Quadruped robots are preferred since they can offer better stability with considerable reliability. In recent years, passive dynamics has been used to obtain near zero-energy bounding gaits. Although theoretically such gaits consume no energy, in practice some additional energy is required to overcome losses. Existence and stability of such gaits have been thoroughly studied in literature for quadruped models with the assumption that the mass distribution and stiffness in the front and back legs are symmetric. Fixed points found using Poincare map indicate touchdown angle-liftoff angle symmetry between front and back legs. This property can be used to search for fixed points with ease. However, the range of initial conditions where the bounding gait is stable is highly limited. Control laws based on symmetry conditions observed are proposed in this paper to improve the stability region. One such control law based on body-fixed touchdown angles theoretically allows redesign of quadruped robot with physical cross coupling between legs to achieve inherent stability without leg actuation.

scholarly journals Stability-Guaranteed and High Terrain Adaptability Static Gait for Quadruped Robots

Sensors ◽  
2020 ◽  
Vol 20 (17) ◽  
pp. 4911
Author(s):  
Qian Hao ◽  
Zhaoba Wang ◽  
Junzheng Wang ◽  
Guangrong Chen
Keyword(s):  
Impedance Control ◽  
Stability Margin ◽  
Planning Method ◽  
Legged Robots ◽  
Gait Planning ◽  
Quadruped Locomotion ◽  
Quadruped Robots ◽  
Adjustment Strategy ◽  
Compliant Behavior ◽  
The Stability

Stability is a prerequisite for legged robots to execute tasks and traverse rough terrains. To guarantee the stability of quadruped locomotion and improve the terrain adaptability of quadruped robots, a stability-guaranteed and high terrain adaptability static gait for quadruped robots is addressed. Firstly, three chosen stability-guaranteed static gaits: intermittent gait 1&2 and coordinated gait are investigated. In addition, then the static gait: intermittent gait 1, which is with the biggest stability margin, is chosen to do a further research about quadruped robots walking on rough terrains. Secondly, a position/force based impedance control is employed to achieve a compliant behavior of quadruped robots on rough terrains. Thirdly, an exploratory gait planning method on uneven terrains with touch sensing and an attitude-position adjustment strategy with terrain estimation are proposed to improve the terrain adaptability of quadruped robots. Finally, the proposed methods are validated by simulations.

Contrôle de la stabilité des remblais par la mesure des déplacements horizontaux

1974 ◽  
Vol 11 (1) ◽  
pp. 182-201 ◽  
Author(s):  
René Marche ◽  
Robert Chapuis
Keyword(s):  
Factor Of Safety ◽  
Soft Clay ◽  
Ground Surface ◽  
Soft Layer ◽  
The Stability ◽  
Horizontal Displacements

The horizontal displacements measured at the toe of eight embankments are analyzed as a function of the factor of safety. The embankments are built on layers of soft clay. Only the undrained stage is studied.When the factor of safety of the embankments is higher than about 1.4, the horizontal displacements on the ground surface, at the toe of the embankment seem to follow an elastic law which is highly dependent on the ratio of the thickness of the soft layer to the width of the embankment. When the factor of safety is lower than about 1.4, the horizontal displacements do not follow an elastic law, they increase considerably. Consequently, it is suggested that the horizontal displacements be precisely measured at the toe of embankments during construction. These measurements are simple and sensitive to the approach of failure, they can be efficiently used to control the stability of embankments. This study also gives some information concerning the variation of horizontal displacements versus depth.

Modification of the contact area of a standard force platform and runway for small breed dogs

2014 ◽  
Vol 27 (04) ◽  
pp. 257-262 ◽  
Author(s):  
J. Y. W. Kim ◽  
T. C. Garcia-Nolan ◽  
S. Y. Kim ◽  
K. Hayashi ◽  
P. L. Hitchens ◽  
...  
Keyword(s):  
Reaction Force ◽  
Force Plate ◽  
Force Platform ◽  
Standard Size ◽  
Plate Size ◽  
Propulsion Force ◽  
In Series ◽  
Reaction Forces ◽  
Wood Frame ◽  
Clinically Significant

SummaryObjectives: To develop a platform that used standard size force plates for large breed dogs to capture ground reaction force data from any size dog.Methods: A walkway platform was constructed to accommodate two force plates (60 cm x 40 cm) positioned in series to a variety of smaller sizes. It was constructed from a custom wood frame with thick aluminium sheet force plate covers that prevented transfer of load to the force plate, except for rectangular windows of three different dimensions. A friction study was performed to ensure plates did not translate relative to one another during gait trials. A prospective, observational, single crossover study design was used to compare the effect of force platform configuration (full plate size [original plate], half plate size [modified plate]) on ground reaction forces using eight adult healthy Labrador Retriever dogs.Results: Slippage of the steel plate on the force plate did not occur. Peak propulsion force was the only kinetic variable statistically different between the full size and half sized platforms. There were no clinically significant differences between the full and half force platforms for the variables and dogs studied.Discussion and conclusion: The modified force platform allows the original 60 x 40 cm force plate to be adjusted effectively to a 30 x 40 cm, 20 x 40 cm and 15 x 40 cm sized plate with no clinically significant change in kinetic variables. This modification that worked for large breed dogs will potentially allow kinetic analysis of a large variety of dogs with different stride lengths.

Ground reaction force and hoof deceleration patterns on two different surfaces at the trot

2006 ◽  
Vol 3 (4) ◽  
pp. 209-216 ◽  
Author(s):  
Pia Gustås ◽  
Christopher Johnston ◽  
Stig Drevemo
Keyword(s):  
Ground Reaction Force ◽  
Reaction Force ◽  
Force Plate ◽  
Ground Surface ◽  
Ground Reaction Forces ◽  
Triaxial Accelerometer ◽  
Loading Rates ◽  
Sand Surface ◽  
Reaction Forces ◽  
Force Data

AbstractThe objective of the present study was to compare the hoof deceleration and ground reaction forces following impact on two different surfaces. Seven unshod Standardbreds were trotted by hand at 3.0–5.7 m s− 1 over a force plate covered by either of the two surfaces, sandpaper or a 1 cm layer of sand. Impact deceleration data were recorded from one triaxial accelerometer mounted on the fore- and hind hooves, respectively. Ground reaction force data were obtained synchronously from a force plate, sampled at 4.8 kHz. The differences between the two surfaces were studied by analysing representative deceleration and force variables for individual horses. The maximum horizontal peak deceleration and the loading rates of the vertical and the horizontal forces were significantly higher on sandpaper compared with the sand surface (P < 0.001). In addition, the initial vertical deceleration was significantly higher on sandpaper in the forelimb (P < 0.001). In conclusion, it was shown that the different qualities of the ground surface result in differences in the hoof-braking pattern, which may be of great importance for the strength of the distal horse limb also at slow speeds.

Simple Leg Placement Strategy for a One Legged Running Model

2012 ◽  
Author(s):  
Timothy Sullivan ◽  
Justin Seipel
Keyword(s):  
Stance Phase ◽  
Energy State ◽  
Center Of Mass ◽  
Mass Movement ◽  
Legged Locomotion ◽  
Energy Conserving ◽  
Lower Torque ◽  
The Stability ◽  
Time Required ◽  
Torque Values

The Spring Loaded Inverted Pendulum (SLIP) model was developed to describe center of mass movement patterns observed in animals, using only a springy leg and a point mass. However, SLIP is energy conserving and does not accurately represent any biological or robotic system. Still, this model is often used as a foundation for the investigation of improved legged locomotion models. One such model called Torque Damped SLIP (TD-SLIP) utilizes two additional parameters, a time dependent torque and dampening to drastically increase the stability. Forced Damped SLIP (FD-SLIP), a predecessor of TD-SLIP, has shown that this model can be further simplified by using a constant torque, instead of a time varying torque, while still maintaining stability. Using FD-SLIP as a base, this paper explores a leg placement strategy using a simple PI controller. The controller takes advantage of the fact that the energy state of FD-SLIP is symmetric entering and leaving the stance phase during steady state conditions. During the flight phase, the touch down leg angle is adjusted so that the energy dissipation due to dampening, during the stance phase, compensates for any imbalance of energy. This controller approximately doubles the region of stability when subjected to velocity perturbations at touchdown, enables the model to operate at considerably lower torque values, and drastically reduces the time required to recover from a perturbation, while using less energy. Finally, the leg placement strategy used effectively imitates the natural human response to velocity perturbations while running.

scholarly journals Measurement of xylem water pressure using High-Capacity Tensiometer and benchmarking against Pressure Chamber and Thermocouple Psychrometer

2020 ◽  
Vol 195 ◽  
pp. 03014
Author(s):  
Roberta Dainese ◽  
Giuseppe Tedeschi ◽  
Thierry Fourcaud ◽  
Alessandro Tarantino
Keyword(s):  
Water Flow ◽  
Water Pressure ◽  
High Capacity ◽  
Ground Surface ◽  
Pressure Chamber ◽  
Rainwater Infiltration ◽  
Thermocouple Psychrometer ◽  
Earth Structures ◽  
Pressure Water ◽  
The Stability

The response of the shallow portion of the ground (vadose zone) and of earth structures is affected by the interaction with the atmosphere. Rainwater infiltration and evapotranspiration affect the stability of man-made and natural slopes and cause shallow foundations and embankments to settle and heave. Very frequently, the ground surface is covered by vegetation and, as a result, transpiration plays a major role in ground-atmosphere interaction. The soil, the plant, and the atmosphere form a continuous hydraulic system, which is referred to as Soil-Plant-Atmosphere Continuum (SPAC). The SPAC actually represents the ‘boundary condition’ of the geotechnical water flow problem. Water flow in soil and plant takes place because of gradients in hydraulic head triggered by the negative water pressure (water tension) generated in the leaf stomata. To study the response of the SPAC, (negative) water pressure needs to be measured not only in the soil but also in the plant. The paper presents a novel technique to measure the xylem water pressure based on the use of the High-Capacity Tensiometer (HCT), which is benchmarked against conventional techniques for xylem water pressure measurements, i.e. the Pressure Chamber (PC) and the Thermocouple Psychrometer (TP).

Reduced prosthetic stiffness lowers the metabolic cost of running for athletes with bilateral transtibial amputations

2017 ◽  
Vol 122 (4) ◽  
pp. 976-984 ◽  
Author(s):  
Owen N. Beck ◽  
Paolo Taboga ◽  
Alena M. Grabowski
Keyword(s):  
Lower Limb ◽  
Metabolic Cost ◽  
Ground Reaction Forces ◽  
Metabolic Rates ◽  
Distance Running ◽  
Cost Of Transport ◽  
Leg Stiffness ◽  
Metabolic Costs ◽  
In Series ◽  
Reaction Forces

Inspired by the springlike action of biological legs, running-specific prostheses are designed to enable athletes with lower-limb amputations to run. However, manufacturer’s recommendations for prosthetic stiffness and height may not optimize running performance. Therefore, we investigated the effects of using different prosthetic configurations on the metabolic cost and biomechanics of running. Five athletes with bilateral transtibial amputations each performed 15 trials on a force-measuring treadmill at 2.5 or 3.0 m/s. Athletes ran using each of 3 different prosthetic models (Freedom Innovations Catapult FX6, Össur Flex-Run, and Ottobock 1E90 Sprinter) with 5 combinations of stiffness categories (manufacturer’s recommended and ± 1) and heights (International Paralympic Committee’s maximum competition height and ± 2 cm) while we measured metabolic rates and ground reaction forces. Overall, prosthetic stiffness [fixed effect (β) = 0.036; P = 0.008] but not height ( P ≥ 0.089) affected the net metabolic cost of transport; less stiff prostheses reduced metabolic cost. While controlling for prosthetic stiffness (in kilonewtons per meter), using the Flex-Run (β = −0.139; P = 0.044) and 1E90 Sprinter prostheses (β = −0.176; P = 0.009) reduced net metabolic costs by 4.3–4.9% compared with using the Catapult prostheses. The metabolic cost of running improved when athletes used prosthetic configurations that decreased peak horizontal braking ground reaction forces (β = 2.786; P = 0.001), stride frequencies (β = 0.911; P < 0.001), and leg stiffness values (β = 0.053; P = 0.009). Remarkably, athletes did not maintain overall leg stiffness across prosthetic stiffness conditions. Rather, the in-series prosthetic stiffness governed overall leg stiffness. The metabolic cost of running in athletes with bilateral transtibial amputations is influenced by prosthetic model and stiffness but not height. NEW & NOTEWORTHY We measured the metabolic rates and biomechanics of five athletes with bilateral transtibial amputations while running with different prosthetic configurations. The metabolic cost of running for these athletes is minimized by using an optimal prosthetic model and reducing prosthetic stiffness. The metabolic cost of running was independent of prosthetic height, suggesting that longer legs are not advantageous for distance running. Moreover, the in-series prosthetic stiffness governs the leg stiffness of athletes with bilateral leg amputations.

Stability of a single tunnel in cohesive–frictional soil subjected to surcharge loading

2011 ◽  
Vol 48 (12) ◽  
pp. 1841-1854 ◽  
Author(s):  
Kentaro Yamamoto ◽  
Andrei V. Lyamin ◽  
Daniel W. Wilson ◽  
Scott W. Sloan ◽  
Andrew J. Abbo
Keyword(s):  
Upper Bound ◽  
Limit Analysis ◽  
Ground Surface ◽  
Soil Mass ◽  
Building Technology ◽  
Surcharge Loading ◽  
Large Size ◽  
Surcharge Load ◽  
The Stability ◽  
Frictional Soils

This paper focuses mainly on the stability of a square tunnel in cohesive–frictional soils subjected to surcharge loading. Large-size noncircular tunnels are quickly becoming a widespread building technology by virtue of the development of advanced tunneling machines. The stability of square tunnels in cohesive–frictional soils subjected to surcharge loading has been investigated theoretically and numerically, assuming plane strain conditions. Despite the importance of this problem, previous research on the subject is very limited. At present, no generally accepted design or analysis method is available to evaluate the stability of tunnels or openings in cohesive–frictional soils. In this study, a continuous loading is applied to the ground surface, and both smooth and rough interface conditions between the loading and soil are modelled. For a series of tunnel geometries and material properties, rigorous lower and upper bound solutions for the ultimate surcharge loading of the considered soil mass are obtained by applying recently developed numerical limit analysis techniques. The results obtained are presented in the form of dimensionless stability charts for practical convenience, with the actual surcharge loads being closely bracketed from above and below. As a handy practical means, upper bound rigid-block mechanisms for square tunnels have also been developed, and the obtained values of collapse loads were compared with the results from numerical limit analysis to verify the accuracy of both approaches. Finally, an expression that approximates the ultimate surcharge load of cohesive–frictional soils with the inclusion of shallow square tunnels has been devised for use by practicing engineers.

Lyapunov-stable control of mechatronic systems

2005 ◽  
Vol 219 (2) ◽  
pp. 173-185 ◽  
Author(s):  
O Enge ◽  
P Maißer
Keyword(s):  
Inverse Dynamics ◽  
Dynamic Control ◽  
Linear Feedback ◽  
Mechatronic Systems ◽  
Electromechanical Systems ◽  
Starting Point ◽  
Reaction Forces ◽  
The Stability ◽  
Lagrange Formalism ◽  
Stable Control

In this paper, a method for controlling mechatronic systems using inverse dynamics is proposed. The starting point is a unified mathematical approach to modelling electromechanical systems based on Lagrange formalism. This mathematical theory is used to represent such systems taking into account all interactions between their substructures. The concept of Lagrange formalism for electromechanical systems is given and the complete governing equations are presented. The Voronetz equations of a partially kinematically controlled electromechanical system (EMS) are derived. The corresponding reaction forces and voltages following from the Voronetz equations are determined. Using these reactions with small modifications, a so-called ‘augmented proportional-derivative (PD) dynamic control law’ is generated. This controller consists of a non-linear feedforward - based on inverse dynamics - and a linear feedback. The stability of the controller is proved using a Lyapunov function. The controller can also be applied to pure multibody systems or a sheer electrical system, both of which are borderline cases of mechatronic systems.

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