scholarly journals Variable-time-interval trajectory optimization-based dynamic walking control of bipedal robot

Robotica ◽  
2021 ◽  
pp. 1-21
Author(s):  
Erman Selim ◽  
Musa Alcı ◽  
Mert Altıntas
Keyword(s):  
Trajectory Optimization ◽  
Equilibrium Points ◽  
Walking Robots ◽  
Computational Time ◽  
Underactuated System ◽  
Time Interval ◽  
Dynamic Walking ◽  
Cost Of Transport ◽  
Variable Time ◽  
Computational Load

Abstract Bipedal robots by their nature show both hybrid and underactuated system features which are not stable and controllable at every point of joint space. They are only controllable on certain fixed equilibrium points and some trajectories that are periodically stable between these points. Therefore, it is crucial to determine the trajectory in the control of walking robots. However, trajectory optimization causes a heavy computational load. Conventional methods to reduce the computational load weaken the optimization accuracy. As a solution, a variable time interval trajectory optimization method is proposed. In this study, optimization accuracy can be increased without additional computational time. Moreover, a five-link planar biped walking robot is designed, produced, and the dynamic walking is controlled with the proposed method. Finally, cost of transport (CoT) values are calculated and compared with other methods in the literature to reveal the contribution of the study. According to comparisons, the proposed method increases the optimization accuracy and decreases the CoT value.

scholarly journals Research of Trajectory Optimization Approaches in Synthesized Optimal Control

Symmetry ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 336
Author(s):  
Askhat Diveev ◽  
Elizaveta Shmalko
Keyword(s):  
Optimal Control ◽  
Equilibrium Point ◽  
Trajectory Optimization ◽  
Stable Equilibrium ◽  
Equilibrium Points ◽  
Control Object ◽  
Symbolic Regression ◽  
Optimal Location ◽  
Stable Equilibrium Point ◽  
Stabilization System

This article presents a study devoted to the emerging method of synthesized optimal control. This is a new type of control based on changing the position of a stable equilibrium point. The object stabilization system forces the object to move towards the equilibrium point, and by changing its position over time, it is possible to bring the object to the desired terminal state with the optimal value of the quality criterion. The implementation of such control requires the construction of two control contours. The first contour ensures the stability of the control object relative to some point in the state space. Methods of symbolic regression are applied for numerical synthesis of a stabilization system. The second contour provides optimal control of the stable equilibrium point position. The present paper provides a study of various approaches to find the optimal location of equilibrium points. A new problem statement with the search of function for optimal location of the equilibrium points in the second stage of the synthesized optimal control approach is formulated. Symbolic regression methods of solving the stated problem are discussed. In the presented numerical example, a piece-wise linear function is applied to approximate the location of equilibrium points.

scholarly journals Influence of Topographic Characteristics on the Adaptive Time Interval for Diffusion Wave Simulation

Water ◽  
2019 ◽  
Vol 11 (3) ◽  
pp. 431
Author(s):  
Pin-Chun Huang ◽  
Kwan Lee ◽  
Boris Gartsman
Keyword(s):  
Flood Control ◽  
Temporal Distribution ◽  
Living Environment ◽  
Mitigation Measures ◽  
Computational Time ◽  
Time Interval ◽  
Flood Warning ◽  
Urgent Task ◽  
Research Findings ◽  
Flood Warning Systems

Frequent flash floods in recent years have resulted in a major impact on the living environment, urban planning, economic system and flood control facilities of residents around the world; therefore, the establishment of disaster management and flood warning systems is an urgent task, required for government units to propose flood mitigation measures. To conserve the numerical accuracy and maintain stability for explicit scheme, the Courant–Friedrich–Lewy (CFL) condition is necessarily enforced, and it is conducted to regulate the relation between the numerical marching speed and wave celerity. On the other hand, to avoid the problem of flow reflux between adjacent grids in executing 2D floodplain simulation, another restriction on time intervals, known as the Hunter condition, was devised in an earlier study. The objective of this study was to analyze the spatial and temporal distribution of these two time-interval restrictions during runoff simulations. Via a case study of the Komarovsky River Basin in Russia, the results show that at the beginning of a storm, the computational time interval is restricted by the CFL condition along the upstream steep hillsides, and the time interval is subject to the Hunter condition in the mainstream during the occurrence of the main storm. The reason of a reduction in computational efficiency, which is a common problem in conducting distributed routing, was clearly explained. To relax the time-interval restrictions for efficient flood forecasting, the research findings also indicate the importance of integrating modified hydrological models proposed in recent studies.

Developing a variable time-interval continuous verification method for ensemble flood forecasts

2020 ◽  
Author(s):  
Schalk Jan van Andel
Keyword(s):  
Flood Event ◽  
False Alarms ◽  
Time Interval ◽  
Forecast Verification ◽  
Time Intervals ◽  
Verification Method ◽  
Variable Time ◽  
Equal Interval ◽  
Flood Warning ◽  
Variable Duration

<p>Most continuous verification metrics for hydrometeorological forecasts are based on equal interval forecasts and observations (e.g. daily, 6-hourly, etc.). For some purposes of verification, however, it might be more beneficial to have variable time intervals that take into account the duration of events, e.g. rainfall or flood event (or discharge exceeding a flood warning threshold). Such verification, however, is challenged by defining the length of the non-event intervals for scoring correct rejections and false alarms, needed for continuous verification.  The work presented here suggests how to approach this challenge and presents verification results of a continuous forecast verification method that take into account variable duration of events.</p>

Adding an Upper Body to Passive Dynamic Walking Robots by Means of a Bisecting Hip Mechanism

2007 ◽  
Vol 23 (1) ◽  
pp. 112-123 ◽  
Author(s):  
Martijn Wisse ◽  
Daan G. E. Hobbelen ◽  
Arend L. Schwab
Keyword(s):  
Upper Body ◽  
Walking Robots ◽  
Dynamic Walking ◽  
Passive Dynamic Walking

scholarly journals Versatile Locomotion Planning and Control for Humanoid Robots

2021 ◽  
Vol 8 ◽  
Author(s):  
Junhyeok Ahn ◽  
Steven Jens Jorgensen ◽  
Seung Hyeon Bang ◽  
Luis Sentis
Keyword(s):  
Trajectory Optimization ◽  
Control Method ◽  
Biped Robot ◽  
Humanoid Robots ◽  
Integer Program ◽  
Whole Body ◽  
Walking Robots ◽  
Planning And Control ◽  
Floating Base ◽  
And Control

We propose a locomotion framework for bipedal robots consisting of a new motion planning method, dubbed trajectory optimization for walking robots plus (TOWR+), and a new whole-body control method, dubbed implicit hierarchical whole-body controller (IHWBC). For versatility, we consider the use of a composite rigid body (CRB) model to optimize the robot’s walking behavior. The proposed CRB model considers the floating base dynamics while accounting for the effects of the heavy distal mass of humanoids using a pre-trained centroidal inertia network. TOWR+ leverages the phase-based parameterization of its precursor, TOWR, and optimizes for base and end-effectors motions, feet contact wrenches, as well as contact timing and locations without the need to solve a complementary problem or integer program. The use of IHWBC enforces unilateral contact constraints (i.e., non-slip and non-penetration constraints) and a task hierarchy through the cost function, relaxing contact constraints and providing an implicit hierarchy between tasks. This controller provides additional flexibility and smooth task and contact transitions as applied to our 10 degree-of-freedom, line-feet biped robot DRACO. In addition, we introduce a new open-source and light-weight software architecture, dubbed planning and control (PnC), that implements and combines TOWR+ and IHWBC. PnC provides modularity, versatility, and scalability so that the provided modules can be interchanged with other motion planners and whole-body controllers and tested in an end-to-end manner. In the experimental section, we first analyze the performance of TOWR+ using various bipeds. We then demonstrate balancing behaviors on the DRACO hardware using the proposed IHWBC method. Finally, we integrate TOWR+ and IHWBC and demonstrate step-and-stop behaviors on the DRACO hardware.

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