Design of a Lyapunov Controller for an Electro-hydraulic Actuator During Contact Tasks

2000 ◽  
Vol 123 (2) ◽  
pp. 299-307 ◽  
Author(s):  
Navid Niksefat ◽  
Christine Q. Wu ◽  
Nariman Sepehri
Keyword(s):  
Free Space ◽  
Nonsmooth Dynamics ◽  
Hydraulic Actuator ◽  
Nonlinear Controller ◽  
Robust Controller ◽  
Task Control ◽  
Lyapunov Controller ◽  
Lyapunov’S Second Method ◽  
The Stability ◽  
Contact Tasks

In this paper, an algorithm is developed for contact task control of electro-hydraulic actuators. The goal is to design and experimentally evaluate a robust controller that allows a hydraulic actuator to follow a free space trajectory and then make and maintain contact with the environment for exerting a desired force. First, the dynamic model of a hydraulic actuator interacting with an environment is described. Then, a Lyapunov-based controller is designed, which regulates the actuator’s position and upon contact with the environment switches to a force controller. Extended Lyapunov’s second method is used for stability analysis of the developed control system, which consists of nonsmooth dynamics. The stability of the system is guaranteed by using a smooth Lyapunov function under the condition of existence and uniqueness of Filippov’s solution. The efficacy of the proposed nonlinear controller is verified via experiments. The experiments are performed on an industrial hydraulic actuator equipped with a servovalve and include motion through free space, contact with the environment and the transition between the two.

scholarly journals Imitation learning-based framework for learning 6-D linear compliant motions

2021 ◽  
Author(s):  
Markku Suomalainen ◽  
Fares J. Abu-dakka ◽  
Ville Kyrki
Keyword(s):  
Contact Force ◽  
Free Space ◽  
Prior Information ◽  
Goal Area ◽  
Imitation Learning ◽  
Learning From Demonstration ◽  
End Effector ◽  
Localization Accuracy ◽  
Novel Method ◽  
Contact Tasks

AbstractWe present a novel method for learning from demonstration 6-D tasks that can be modeled as a sequence of linear motions and compliances. The focus of this paper is the learning of a single linear primitive, many of which can be sequenced to perform more complex tasks. The presented method learns from demonstrations how to take advantage of mechanical gradients in in-contact tasks, such as assembly, both for translations and rotations, without any prior information. The method assumes there exists a desired linear direction in 6-D which, if followed by the manipulator, leads the robot’s end-effector to the goal area shown in the demonstration, either in free space or by leveraging contact through compliance. First, demonstrations are gathered where the teacher explicitly shows the robot how the mechanical gradients can be used as guidance towards the goal. From the demonstrations, a set of directions is computed which would result in the observed motion at each timestep during a demonstration of a single primitive. By observing which direction is included in all these sets, we find a single desired direction which can reproduce the demonstrated motion. Finding the number of compliant axes and their directions in both rotation and translation is based on the assumption that in the presence of a desired direction of motion, all other observed motion is caused by the contact force of the environment, signalling the need for compliance. We evaluate the method on a KUKA LWR4+ robot with test setups imitating typical tasks where a human would use compliance to cope with positional uncertainty. Results show that the method can successfully learn and reproduce compliant motions by taking advantage of the geometry of the task, therefore reducing the need for localization accuracy.

Observer-Based Feedback Linearizing Control of an Electromagnetic Suspension

1996 ◽  
Vol 118 (3) ◽  
pp. 615-619 ◽  
Author(s):  
B. C. Fabien
Keyword(s):  
Feedback Controller ◽  
Superior Performance ◽  
Linear Feedback ◽  
Nonlinear Controller ◽  
Electromagnetic Suspension ◽  
Weakly Coupled ◽  
Coupled Riccati Equations ◽  
Linear Feedback Controller ◽  
Lyapunov’S Second Method ◽  
Feedback Linearizable Systems

This paper develops a stabilizing observer-based feedback linearizing controller for a single-axis electromagnetic suspension. The controller uses only the measured output of the system, and is shown to be robust with respect to parameter uncertainty. The controller differs from other robust feedback linearizing controllers that have appeared in recent literature, because it is continuous, and non-adaptive. Lyapunov’s second method is used to prove stability and robustness of the controller. The controller has a simple structure and its gains are determined by solving two weakly coupled Riccati equations. Numerical simulations are performed to compare a linear feedback controller and the observer-based feedback linearizing controller. Results obtained demonstrate that the nonlinear controller yields superior performance when compared with the linear feedback controller. The controller synthesis technique developed in this paper is applicable to other fully feedback linearizable systems, not just electromagnetic suspensions.

scholarly journals Designing a Robust Controller Using SMC and Fuzzy Artificial Organic Networks for Brushed DC Motors

Energies ◽  
2020 ◽  
Vol 13 (12) ◽  
pp. 3091 ◽  
Author(s):  
Pedro Ponce ◽  
J. Antonio Rosales ◽  
Arturo Molina ◽  
Hiram Ponce ◽  
Brian MacCleery
Keyword(s):  
Engineering Students ◽  
Sliding Mode ◽  
Dc Motor ◽  
Sliding Mode Controller ◽  
Robust Controller ◽  
Load Torque ◽  
Dc Drive ◽  
The Stability ◽  
Command Signal ◽  
Organic Networks

Electric direct-current (DC) drives based on DC motor are extremely important in the manufacturing process, so it must be crucial to increase their performance when they are working on load disturbances or the DC motor’s parameters change. Usually, several load torque suddenly appears when electric drives are operating in a speed closed-loop, so robust controllers are required to keep the speed high-performance. One of the most well-known robust strategies is the sliding mode controller (SMC), which works under discontinue operation. This controller can handle disturbances and variations in the plant’s parameters, so the controller has robust performance. Nevertheless, it has some disadvantages (chattering). Therefore, this paper proposed a fuzzy logic controller (FLC) that includes an artificial organic network for adjusting the command signal of the SMC. The proposed controller gives a smooth signal that decrements the chattering in the SMC. The stability condition that is based on Lyapunov of the DC motor is driven is evaluated; besides, the stability margins are calculated. The proposed controller is designed using co-simulation and a real testbed since co-simulation is an extremely useful tool in academia and industry allows to move from co-simulation to real implementation in short period of time. Moreover, there are several universities and industries that adopt co-simulation as the main step to design prototypes. Thus, engineering students and designers are able to achieve excellent results when they design rapid and functional prototypes. For instance, co-simulation based on Multisim leads to design directly printed circuit boards so engineering students or designers could swiftly get an experimental DC drive. The experimental results using this platform show excellent DC-drive performance when the load torque disturbances are suddenly applied to the system. As a result, the proposed controller based on fuzzy artificial organic and SMC allows for adjusting the command signal that improves the dynamic response in DC drives. The experimental response using the sliding-mode controller with fuzzy artificial organic networks is compared against an auto-tuning, Proportional-Integral-Derivative (PID), which is a conventional controller. The PID controller is the most implemented controller in several industries, so this proposal can contribute to improving manufacturing applications, such as micro-computer numerical control (CNC) machines. Moreover, the proposed robust controller achieves a superior-speed response under the whole tested scenarios. Finally, the presented design methodology based on co-simulation could be used by universities and industry for validating and implementing advanced control systems in DC drives.

Impact Control in Hydraulic Actuators

2004 ◽  
Vol 127 (2) ◽  
pp. 197-205 ◽  
Author(s):  
P. Sekhavat ◽  
Q. Wu ◽  
N. Sepehri
Keyword(s):  
Lyapunov Stability Theory ◽  
Control Law ◽  
Asymptotic Convergence ◽  
Hydraulic Parameters ◽  
Hydraulic Actuators ◽  
Task Control ◽  
Nonsmooth Systems ◽  
Type Contact ◽  
The Stability ◽  
Short Transition

Every manipulator contact task that begins with a transition from free motion to constraint motion may exhibit impacts that could drive the system unstable. Stabilization of manipulators during this transition is, therefore, an important issue in contact task control design. This paper presents a discontinuous controller to regulate the transition mode in hydraulic actuators. The controller, upon sensing a nonzero force, positions the actuator at the location where the force was sensed, thus, exerting minimal force on a nonmoving environment. The scheme does not require force or velocity feedback as they are difficult to measure throughout the short transition phase. Also, no knowledge about the environment or hydraulic parameters is required for control action. Due to the discontinuity of the control law, the control system is nonsmooth. First, the existence, continuation and uniqueness of Filippov’s solution to the system are proven. Next, the extension of Lyapunov stability theory to nonsmooth systems is employed to guarantee the global asymptotic convergence of the entire system’s state towards the equilibrium point. Complete dynamic characteristics of hydraulic functions and Hertz-type contact model are included in the stability analysis. Experiments are conducted to verify the practicality and effectiveness of the proposed controller. They include actuator collisions with hard and soft environments and with various approach velocities.

Development of Robust Excitation Controller for Synchronous Generator

2014 ◽  
Vol 573 ◽  
pp. 328-333
Author(s):  
R. Ramya ◽  
K. Selvi ◽  
M. Tamilvanan
Keyword(s):  
Output Voltage ◽  
Closed Loop ◽  
Synchronous Generator ◽  
Local Mode ◽  
Small Signal ◽  
Closed Loop System ◽  
Robust Controller ◽  
Sensitivity Approach ◽  
Single Machine Infinite Bus ◽  
The Stability

This paper deals with the design and evaluation of robust excitation controller for a single-machine infinite-bus power system. The design of the regulator guarantees the stability of the closed loop system and ensures the output voltage is maintained within an acceptable threshold. In addition, it damps out local mode oscillations for small signal disturbances. The designed robust controller is also analyzed under change in step input and disturbance, which limits the heavy oscillations on the speed ω and voltage. Glover-McFarlane loop shaping algorithm is applied in designing the robust excitation controller. Two different techniques such as Optimal control and mixed sensitivity approach is used in this paper. The performance of the AVR was analyzed and compared with IEEE type2 Exciter.

Uniform robust exact differentiator based adaptive robust control for a class of nonlinear systems

2017 ◽  
Vol 40 (9) ◽  
pp. 2901-2911 ◽  
Author(s):  
Zhangbao Xu ◽  
Dawei Ma ◽  
Jianyong Yao
Keyword(s):  
Robust Control ◽  
Nonlinear Systems ◽  
Closed Loop ◽  
Lyapunov Method ◽  
Adaptive Robust Control ◽  
Experimental Results ◽  
Closed Loop System ◽  
Robust Controller ◽  
Performance Simulation ◽  
The Stability

In this paper, an adaptive robust controller with uniform robust exact differentiator has been proposed for a class of nonlinear systems with structured and unstructured uncertainties. The adaptive robust controller is integrated with an uniform robust differentiator to handle the problem of the incalculable part of the derivative of virtual controls and the differential explosion happened in backstepping techniques. The stability of the closed loop system is demonstrated via Lyapunov method ensuring a prescribed transient and tracking performance. Simulation and experimental results are carried out to verify the advantages of the proposed method.

scholarly journals Robust Time-Varying Output Formation Control for Swarm Systems with Nonlinear Uncertainties

Complexity ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Xiaofeng Chai ◽  
Qing Wang ◽  
Yao Yu ◽  
Changyin Sun
Keyword(s):  
Stability Problem ◽  
Formation Control ◽  
Directed Network ◽  
Control Problems ◽  
Time Varying ◽  
Robust Controller ◽  
Nonlinear Uncertainties ◽  
The Stability ◽  
High Order Time ◽  
Time Invariant

Time-varying output formation control problems for high-order time-invariant swarm systems are studied with nonlinear uncertainties and directed network topology in this paper. A robust controller which consists of a nominal controller and a robust compensator is applied to achieve formation control. The nominal controller based on the output feedback is designed to achieve desired time-varying formation properties for the nominal system. And the robust compensator based on the robust signal compensator technology is constructed to restrain nonlinear uncertainties. The time-varying formation problem is transformed into the stability problem. And the formation errors can be arbitrarily small with expected convergence rate. Numerical examples are provided to illustrate the effectiveness of the proposed strategy.

Neuro-Fuzzy Sliding Mode Control of Inverted Pendulum

2013 ◽  
Vol 711 ◽  
pp. 432-439
Author(s):  
Khedoudja Kherraz ◽  
Mustapha Hamerlain ◽  
Nouara Achour
Keyword(s):  
Function Method ◽  
Inverted Pendulum ◽  
Sliding Mode ◽  
Robust Controller ◽  
Fuzzy Sliding Mode Control ◽  
Neuro Fuzzy ◽  
Lyapunov Function Method ◽  
Fuzzy Sliding Mode ◽  
Simulation Results ◽  
The Stability

In this paper we develop a robust controller based on sliding mode, neural network and fuzzy logic for the control of a class of under-actuated systems. The stability of the proposed controller is proved with the Lyapunov function method. Simulation results are made on an inverted pendulum.

scholarly journals Amplitude Modulation and Synchronization of Fractional-Order Memristor-Based Chua's Circuit

2013 ◽  
Vol 2013 ◽  
pp. 1-10 ◽  
Author(s):  
A. G. Radwan ◽  
K. Moaddy ◽  
I. Hashim
Keyword(s):  
Fractional Order ◽  
Amplitude Modulation ◽  
Lyapunov Stability Theory ◽  
Stability And Convergence ◽  
Chua’S Circuit ◽  
Nonlinear Controller ◽  
Chua's Circuit ◽  
Control Functions ◽  
Nonlinear Control Theory ◽  
The Stability

This paper presents a general synchronization technique and an amplitude modulation of chaotic generators. Conventional synchronization and antisynchronization are considered a very narrow subset from the proposed technique where the scale between the output response and the input response can be controlled via control functions and this scale may be either constant (positive, negative) or time dependent. The concept of the proposed technique is based on the nonlinear control theory and Lyapunov stability theory. The nonlinear controller is designed to ensure the stability and convergence of the proposed synchronization scheme. This technique is applied on the synchronization of two identical fractional-order Chua's circuit systems with memristor. Different examples are studied numerically with different system parameters, different orders, and with five alternative cases where the scaling functions are chosen to be positive/negative and constant/dynamic which covers all possible cases from conventional synchronization to the amplitude modulation cases to validate the proposed concept.

Robust Controller Synthesis of Multivariable System Subjected to Noises and Nonlinear Time-Varying Plant Perturbations

1988 ◽  
Vol 110 (3) ◽  
pp. 336-340
Author(s):  
Feng-Hsiag Hsiao ◽  
Bor-Sen Chen
Keyword(s):  
Robust Stability ◽  
Function Class ◽  
Controller Synthesis ◽  
Schur Function ◽  
Time Varying ◽  
Multivariable System ◽  
Feedback Systems ◽  
Robust Controller ◽  
Stabilizing Controller ◽  
The Stability

A new robust stability criterion is developed to guarantee the stability of the feedback systems subjected to noises and nonlinear time-varying plant perturbations. The main contribution of this paper is an extension of the results of robust stability for the class of feedback systems containing nonlinear time-varying plant perturbations to the class of systems with unstable plants and noises. The generally parameterized stabilizing controller, advanced by Youla et al., is combined with Schur function (class S) to synthesize the robust stabilizers of the feedback systems subjected to noises and nonlinear time-varying plant perturbations.

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