Real-Time Planning and Nonlinear Control for Quadrupedal Locomotion With Articulated Tails

2021 ◽  
Vol 143 (7) ◽  
Author(s):  
Randall T. Fawcett ◽  
Abhishek Pandala ◽  
Jeeseop Kim ◽  
Kaveh Akbari Hamed
Keyword(s):  
Real Time ◽  
Degrees Of Freedom ◽  
Center Of Mass ◽  
Hierarchical Control ◽  
Nonlinear Feedback ◽  
Nonlinear Controller ◽  
External Disturbances ◽  
Quadrupedal Locomotion ◽  
Control Scheme ◽  
High Level

Abstract The primary goal of this paper is to develop a formal foundation to design nonlinear feedback control algorithms that intrinsically couple legged robots with bio-inspired tails for robust locomotion in the presence of external disturbances. We present a hierarchical control scheme in which a high-level and real-time path planner, based on an event-based model predictive control (MPC), computes the optimal motion of the center of mass (COM) and tail trajectories. The MPC framework is developed for an innovative reduced-order linear inverted pendulum (LIP) model that is augmented with the tail dynamics. At the lower level of the control scheme, a nonlinear controller is implemented through the use of quadratic programming (QP) and virtual constraints to force the full-order dynamical model to track the prescribed optimal trajectories of the COM and tail while maintaining feasible ground reaction forces at the leg ends. The potential of the analytical results is numerically verified on a full-order simulation model of a quadrupedal robot augmented with a tail with a total of 20 degrees-of-freedom. The numerical studies demonstrate that the proposed control scheme coupled with the tail dynamics can significantly reduce the effect of external disturbances during quadrupedal locomotion.

scholarly journals Observer-based robust integral of the sign of the error control of class I of underactuated mechanical systems: Theory and real-time experiments

2021 ◽  
pp. 014233122110313
Author(s):  
Afef Hfaiedh ◽  
Ahmed Chemori ◽  
Afef Abdelkrim
Keyword(s):  
Real Time ◽  
Error Control ◽  
Degrees Of Freedom ◽  
Sliding Mode ◽  
Mechanical Systems ◽  
Class I ◽  
Control Input ◽  
Underactuated Mechanical Systems ◽  
Control Scheme ◽  
And Performance

In this paper, the control problem of a class I of underactuated mechanical systems (UMSs) is addressed. The considered class includes nonlinear UMSs with two degrees of freedom and one control input. Firstly, we propose the design of a robust integral of the sign of the error (RISE) control law, adequate for this special class. Based on a change of coordinates, the dynamics is transformed into a strict-feedback (SF) form. A Lyapunov-based technique is then employed to prove the asymptotic stability of the resulting closed-loop system. Numerical simulation results show the robustness and performance of the original RISE toward parametric uncertainties and disturbance rejection. A comparative study with a conventional sliding mode control reveals a significant robustness improvement with the proposed original RISE controller. However, in real-time experiments, the amplification of the measurement noise is a major problem. It has an impact on the behaviour of the motor and reduces the performance of the system. To deal with this issue, we propose to estimate the velocity using the robust Levant differentiator instead of the numerical derivative. Real-time experiments were performed on the testbed of the inertia wheel inverted pendulum to demonstrate the relevance of the proposed observer-based RISE control scheme. The obtained real-time experimental results and the obtained evaluation indices show clearly a better performance of the proposed observer-based RISE approach compared to the sliding mode and the original RISE controllers.

scholarly journals Solution for indoor positioning using WIFI networks

2019 ◽  
Vol 2 ◽  
pp. 1-8
Author(s):  
Carolina Aguilar Aravena ◽  
Luciene Stamato Delazari
Keyword(s):  
Real Time ◽  
Open Source Software ◽  
Exponential Growth ◽  
Center Of Mass ◽  
Indoor Positioning ◽  
High Availability ◽  
Wifi Networks ◽  
Positioning Systems ◽  
High Level ◽  
Level Of Agreement

<p><strong>Abstract.</strong> The use of Indoor Positioning Systems (IPS) has gained an exponential growth due to the high availability of infrastructure to carry out its development. In this context this work presents the development of an Open Source Software for indoor positioning with the use of WIFI networks, since in this type of environment the pedestrian needs a greater assistance for its location and navigation. The application was developed in Android Studio, with a database generated using the WIFI routers of the study area. In addition, the position of the user in real time is showed in a map. The positioning techniques used for this application were Proximity, Center of Mass and Trilateration. The results shows that it is possible to obtain a high level of agreement in the identification of building and floor. The results also show that it is possible to develop an indoor positioning application through WIFI networks.</p>

Application of non-linear H∞ control to the Tetrabot robot manipulator

1998 ◽  
Vol 212 (6) ◽  
pp. 459-465 ◽  
Author(s):  
I Postlethwaite ◽  
A Bartoszewicz
Keyword(s):  
Degrees Of Freedom ◽  
Robot Manipulator ◽  
Industrial Robot ◽  
External Disturbances ◽  
Six Degrees Of Freedom ◽  
Control Scheme ◽  
Non Linear ◽  
Modelling Uncertainties ◽  
Real Robot ◽  
Robotic Application

In this paper, an application of a non-linear H∞ control law for an industrial robot manipulator is presented. Control of the manipulator motion is formulated into a non-linear H∞ optimization problem, namely optimal tracking performance in the presence of modelling uncertainties and external disturbances. Analytical solutions for this problem are implemented on a real robot. The robot under consideration is the six-degrees-of-freedom GEC Tetrabot. Investigations are made into the selection of weights for the H∞ controller and it is shown how different selections of weights affect the Tetrabot performance. The authors believe this to be the first robotic application of nonlinear H∞ control. Comparisons of the proposed control strategy with conventional proportional-derivative and proportional-integral-derivative controllers show favourable performance of the Tetrabot under the new non-linear H∞ control scheme.

Robust Bipedal Locomotion Based on a Hierarchical Control Structure

Robotica ◽  
2019 ◽  
Vol 37 (10) ◽  
pp. 1750-1767 ◽  
Author(s):  
Jianwen Luo ◽  
Yao Su ◽  
Lecheng Ruan ◽  
Ye Zhao ◽  
Donghyun Kim ◽  
...  
Keyword(s):  
Center Of Pressure ◽  
Center Of Mass ◽  
Hierarchical Control ◽  
Middle Level ◽  
Smooth Transition ◽  
Whole Body ◽  
Joint Torques ◽  
Low Level ◽  
Hybrid Controller ◽  
High Level

SummaryTo improve biped locomotion’s robustness to internal and external disturbances, this study proposes a hierarchical structure with three control levels. At the high level, a foothold sequence is generated so that the Center of Mass (CoM) trajectory tracks a planned path. The planning procedure is simplified by selecting the midpoint between two consecutive Center of Pressure (CoP) points as the feature point. At the middle level, a novel robust hybrid controller is devised to drive perturbed system states back to the nominal trajectory within finite cycles without chattering. The novelty lies in that the hybrid controller is not subject to linear CoM dynamic constraints. The hybrid controller consists of two sub-controllers: an oscillation controller and a smoothing controller. For the oscillation controller, the desired CoM height is specified as a sine-shaped function, avoiding a new attractive limit cycle. However, this controller results in the inevitable chattering because of discontinuities. A smoothing controller provides continuous properties and thus can inhibit the chattering problem, but has a smaller region of attraction compared with the oscillation controller. A hybrid controller merges the two controllers for a smooth transition. At the low level, the desired CoM motion is defined as tasks and embedded in a whole body operational space (WBOS) controller to compute the joint torques analytically. The novelty of the low-level controller lies in that within the WBOS framework, CoM motion is not subject to fixed CoM dynamics and thus can be generalized.

scholarly journals Shoulder kinematics plus contextual target information enable control of multiple distal joints of a simulated prosthetic arm and hand

2021 ◽  
Vol 18 (1) ◽  
Author(s):  
Sébastien Mick ◽  
Effie Segas ◽  
Lucas Dure ◽  
Christophe Halgand ◽  
Jenny Benois-Pineau ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Contextual Information ◽  
Gaze Tracking ◽  
Joint Coordination ◽  
Virtual Scene ◽  
Motor Synergies ◽  
Control Scheme ◽  
Command Signals ◽  
High Level ◽  
Shoulder Kinematics

Abstract Background Prosthetic restoration of reach and grasp function after a trans-humeral amputation requires control of multiple distal degrees of freedom in elbow, wrist and fingers. However, such a high level of amputation reduces the amount of available myoelectric and kinematic information from the residual limb. Methods To overcome these limits, we added contextual information about the target’s location and orientation such as can now be extracted from gaze tracking by computer vision tools. For the task of picking and placing a bottle in various positions and orientations in a 3D virtual scene, we trained artificial neural networks to predict postures of an intact subject’s elbow, forearm and wrist (4 degrees of freedom) either solely from shoulder kinematics or with additional knowledge of the movement goal. Subjects then performed the same tasks in the virtual scene with distal joints predicted from the context-aware network. Results Average movement times of 1.22s were only slightly longer than the naturally controlled movements (0.82 s). When using a kinematic-only network, movement times were much longer (2.31s) and compensatory movements from trunk and shoulder were much larger. Integrating contextual information also gave rise to motor synergies closer to natural joint coordination. Conclusions Although notable challenges remain before applying the proposed control scheme to a real-world prosthesis, our study shows that adding contextual information to command signals greatly improves prediction of distal joint angles for prosthetic control.

Dynamics and Control of a Novel Active Yaw Stabilizer to Enhance Vehicle Lateral Motion Stability

2018 ◽  
Vol 140 (8) ◽  
Author(s):  
Fengchen Wang ◽  
Yan Chen
Keyword(s):  
Degrees Of Freedom ◽  
Hierarchical Control ◽  
Lateral Force ◽  
Stability Control ◽  
Level Control ◽  
Road Friction ◽  
Dynamics And Control ◽  
High Level ◽  
And Control ◽  
Yaw Moment

In this paper, a novel active yaw stabilizer (AYS) system is proposed for improving vehicle lateral stability control. The introduced AYS, inspired by the recent in-wheel motor (IWM) technology, has two degrees-of-freedom with independent self-rotating and orbiting movements. The dynamic model of the AYS is first developed. The capability of the AYS is then investigated to show its maximum generation of corrective lateral forces and yaw moments, given a limited vehicle space. Utilizing the high-level Lyapunov-based control design and the low-level control allocation design, a hierarchical control architecture is established to integrate the AYS control with active front steering (AFS) and direct yaw moment control (DYC). To demonstrate the advantages of the AYS, generating corrective lateral force and yaw moment without relying on tire–road interaction, double lane change maneuvers are studied on road with various tire–road friction coefficients. Co-simulation results, integrating CarSim® and MATLAB/Simulink®, successfully verify that the vehicle with the assistance of the AYS system has better lateral dynamics stabilizing performance, compared with cases in which only AFS or DYC is applied.

scholarly journals Disturbance Observer-Based Control for Trajectory Tracking of a Quadrotor

Electronics ◽  
2020 ◽  
Vol 9 (10) ◽  
pp. 1624
Author(s):  
Sang Wook Ha ◽  
Bong Seok Park
Keyword(s):  
Trajectory Tracking ◽  
Closed Loop ◽  
Control Method ◽  
Control Strategies ◽  
Hierarchical Control ◽  
Loop System ◽  
Nonlinear Controller ◽  
Closed Loop System ◽  
External Disturbances ◽  
Dynamic Surface

This paper presents a new control approach for the trajectory tracking of a quadrotor in the presence of external disturbances. Unlike in previous studies using hierarchical control strategies, a nonlinear controller is designed by introducing new state transformations that can use Euler angles as virtual control inputs. Thus, the proposed method can eliminate the timescale separation assumption of hierarchical control strategies. To estimate the external disturbances involved in the translational and rotational dynamics of the quadrotor, disturbance observers are developed. Using state transformations and estimates of external disturbances, we design a robust nonlinear controller based on the dynamic surface control method. The stability of the closed-loop system is analyzed without separation into two subsystems. From the Lyapunov stability theory, it is proven that all error signals in the closed-loop system are uniformly ultimately bounded and can be made arbitrarily small. Finally, simulation results are presented to demonstrate the performance of the proposed controller.

scholarly journals Robust Hierarchical Control for Uncertain Multivariable Hexarotor Systems

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Wei Lin ◽  
Hao Liu
Keyword(s):  
Control Method ◽  
Controller Design ◽  
Load Capacity ◽  
Hierarchical Control ◽  
Tracking Errors ◽  
Robust Controller ◽  
External Disturbances ◽  
Loop Control ◽  
Control Scheme ◽  
Robust Controller Design

Multirotor helicopter attracts more attention due to its increased load capacity and being highly maneuverable. However, these helicopters are uncertain multivariable systems, which pose a challenge for their robust controller design. In this paper, a robust two-loop control scheme is proposed for a hexarotor system. The resulted controller consists of a nominal controller and a robust compensator. The robust compensators are added to restrain the influences of uncertainties such as nonlinear dynamics, coupling, parametric uncertainties, and external disturbances. It is proven that the tracking errors are ultimately bounded with specified boundaries by choosing the parameters of the robust compensators. Simulation results on the hexarotor demonstrate the effectiveness of the proposed control method.

General decay projective synchronization of memristive competitive neural networks via nonlinear controller

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Malika Sader ◽  
Fuyong Wang ◽  
Zhongxin Liu ◽  
Zengqiang Chen
Keyword(s):  
Neural Networks ◽  
General Decay ◽  
Projective Synchronization ◽  
Communication Security ◽  
Activation Functions ◽  
Nonlinear Feedback ◽  
Nonlinear Controller ◽  
Control Scheme ◽  
Special Cases ◽  
Inequality Techniques

Abstract In this paper, the general decay projective synchronization of a class of memristive competitive neural networks with time delay is studied. Firstly, a nonlinear feedback controller is designed, which does not require any knowledge about the activation functions. Then, some new and applicable conditions dependent on the Lyapunov function and the inequality techniques are obtained to guarantee the general decay projective synchronization of the considered systems under the developed controller. Unlike other forms of synchronization, projective synchronization can improve communication security due to the scaling constant’s unpredictability. In addition, the polynomial synchronization, asymptotical synchronization, and exponential synchronization can be seen as the special cases of the general decay projective synchronization. Finally, a numerical example is given to demonstrate the effectiveness of the proposed control scheme.

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