692 research outputs found
Natural ZMP trajectories for biped robot reference generation
The control of a biped humanoid is a challenging
task due to the hard-to-stabilize dynamics. Walking reference
trajectory generation is a key problem. Linear Inverted
Pendulum Model (LIPM) and Zero Moment Point (ZMP)
Criterion based approaches in stable walking reference
generation are reported. In these methods, generally, the ZMP
reference during a stepping motion is kept fixed in the middle of
the supporting foot sole. This kind of reference generation lacks
naturalness, in that, the ZMP in the human walk does not stay
fixed, but it moves forward under the supporting foot. This paper
proposes a reference generation algorithm based on the LIPM
and moving support foot ZMP references. The application of
Fourier series approximation simplifies the solution and it
generates a smooth ZMP reference. A simple inverse kinematics
based joint space controller is used for the tests of the developed
reference trajectory through full-dynamics 3D simulation. A 12
DOF biped robot model is used in the simulations. Simulation
studies suggest that the moving ZMP references are more energy
efficient than the ones with fixed ZMP under the supporting foot.
The results are promising for implementations
Integration of vertical COM motion and angular momentum in an extended Capture Point tracking controller for bipedal walking
In this paper, we demonstrate methods for bipedal walking control based on the Capture Point (CP) methodology.
In particular, we introduce a method to intuitively derive a CP
reference trajectory from the next three steps and extend the
linear inverted pendulum (LIP) based CP tracking controller
introduced in [1], generalizing it to a model that contains
vertical CoM motions and changes in angular momentum.
Respecting the dynamics of general multibody systems, we
propose a measurement-based compensation of multi-body
effects, which leads to a stable closed-loop dynamics of bipedal walking robots. In addition we propose a ZMP projection method, which prevents the robots feet from tilting and ensures the best feasible CP tracking. The extended CP controller’s performance is validated in OpenHRP3 [2] simulations and compared to the controller proposed in [1]
Humanoid robot orientation stabilization by shoulder joint motion during locomotion
Arm swing action is a natural phenomenon that emerges in biped locomotion. A shoulder torque reference generation method is introduced in this paper to utilize arms of a humanoid robot during locomotion. Main idea of the technique is the employment of shoulder joint actuation torques in order to stabilize body orientation. The reference torques are computed by a method which utilizes proportional and derivative actions. Body orientation angles serve as the inputs of this system. The approach is tested via simulations with the 3D full-dynamics model of the humanoid robot SURALP (Sabanci University Robotics Research Laboratory Platform). Results indicate that the method is successful in reducing oscillations of body angles during bipedal walking
Asymptotically Stable Walking of a Five-Link Underactuated 3D Bipedal Robot
This paper presents three feedback controllers that achieve an asymptotically
stable, periodic, and fast walking gait for a 3D (spatial) bipedal robot
consisting of a torso, two legs, and passive (unactuated) point feet. The
contact between the robot and the walking surface is assumed to inhibit yaw
rotation. The studied robot has 8 DOF in the single support phase and 6
actuators. The interest of studying robots with point feet is that the robot's
natural dynamics must be explicitly taken into account to achieve balance while
walking. We use an extension of the method of virtual constraints and hybrid
zero dynamics, in order to simultaneously compute a periodic orbit and an
autonomous feedback controller that realizes the orbit. This method allows the
computations to be carried out on a 2-DOF subsystem of the 8-DOF robot model.
The stability of the walking gait under closed-loop control is evaluated with
the linearization of the restricted Poincar\'e map of the hybrid zero dynamics.
Three strategies are explored. The first strategy consists of imposing a
stability condition during the search of a periodic gait by optimization. The
second strategy uses an event-based controller. In the third approach, the
effect of output selection is discussed and a pertinent choice of outputs is
proposed, leading to stabilization without the use of a supplemental
event-based controller
Quasi optimal sagittal gait of a biped robot with a new structure of knee joint
The design of humanoid robots has been a tricky challenge for several years. Due to the kinematic complexity of human joints, their movements are notoriously difficult to be reproduced by a mechanism. The human knees allow movements including rolling and sliding, and therefore the design of new bioinspired knees is of utmost importance for the reproduction of anthropomorphic walking in the sagittal plane. In this article, the kinematic characteristics of knees were analyzed and a mechanical solution for reproducing them is proposed. The geometrical, kinematic and dynamic models are built together with an impact model for a biped robot with the new knee kinematic. The walking gait is studied as a problem of parametric optimization under constraints. The trajectories of walking are approximated by mathematical functions for a gait composed of single support phases with impacts. Energy criteria allow comparing the robot provided with the new rolling knee mechanism and a robot equipped with revolute knee joints. The results of the optimizations show that the rolling knee brings a decrease of the sthenic criterion. The comparisons of torques are also observed to show the difference of energy distribution between the actuators. For the same actuator selection, these results prove that the robot with rolling knees can walk longer than the robot with revolute joint knees.ANR R2A
Running synthesis and control for monopods and bipeds with articulated
Bibliography: p. 179-20
Implementation and simulation a model predictive control for motion generation of biped robot
This paper dealing with the problem of generation motion of biped robot, to solve this problem, was introduces a new method of implementation a biped robot walking pattern generation byusing a Model Predictive control (MPC) First, the basic of biped robots’ motion was reviewed and was discussed the elements of motion controller. The dynamics of a biped robot is modeled as a running cart on a table which gives a convenient representation for generation ZMP trajectory. After reviewing approach of 3D Linear Inverted Pendulum Model, a pattern generator was designed, lastly in MATLAB/Simulink and using Model Predictive Control Toolbox (MPCT) which provides functions, an app, and Simulink blocks was used for designing and simulating a motion generator based on model predictive controllers (MPC).
The results of simulation are shown that we can realize such controller for generating trajectory of Center of Mass and Zero Moment point by using the MPC. The smooth trajectory of CoM is generated and the resulted ZMP follows the reference with good accuracy
A Dynamics and Stability Framework for Avian Jumping Take-off
Jumping take-off in birds is an explosive behaviour with the goal of
providing a rapid transition from ground to airborne locomotion. An effective
jump is predicated on the need to maintain dynamic stability through the
acceleration phase. The present study concerns understanding how birds retain
control of body attitude and trajectory during take-off. Cursory observation
suggests that stability is achieved with relatively little cost. However,
analysis of the problem shows that the stability margins during jumping are
actually very small and that stability considerations play a significant role
in selection of appropriate jumping kinematics. We use theoretical models to
understand stability in prehensile take-off (from a perch) and also in
non-prehensile take-off (from the ground). The primary instability is tipping,
defined as rotation of the centre of gravity about the ground contact point.
Tipping occurs when the centre of pressure falls outside the functional foot. A
contribution of the paper is the development of graphical tipping stability
margins for both centre of gravity location and acceleration angle. We show
that the nose-up angular acceleration extends stability bounds forward and is
hence helpful in achieving shallow take-offs. The stability margins are used to
interrogate simulated take-offs of real birds using published experimental
kinematic data from a guinea fowl (ground take-off) and a diamond dove (perch
take-off). For the guinea fowl the initial part of the jump is stable, however
simulations exhibit a stuttering instability not observed experimentally that
is probably due to absence of compliance in the idealised joints. The diamond
dove model confirms that the foot provides an active torque reaction during
take-off, extending the range of stable jump angles by around 45{\deg}.Comment: 21 pages, 11 figures; supplementary material:
https://figshare.com/s/86b12868d64828db0d5d; DOI: 10.6084/m9.figshare.721056
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