No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Adaptive Sliding-Mode Control for Velocity and Head-Angle Tracking
Abstract
The ability of a control scheme for a mobile robot to ensure satisfactory performance in an unstructured or unknown environment is what makes the control law unique. Various sources of uncertainties pose a serious challenge to the tracking performance of the system. The state-of-the-art control law presented in Chap. 1 cannot ensure stability in the presence of uncertainties due to feedback linearization methodology, as it requires exact cancellation of the nonlinearities in the system [1, 2]. Moreover, singular perturbation-based approach is prone to generate high control gains which may jeopardize the integrity of the actuators [1, 2]. This is where robust control techniques step in, to assure stable and acceptable performance in the presence of uncertainties. To imitate variation of ground condition, time-varying uncertainties have been induced through the friction coefficients in the planar snake robot model. These uncertainties have been assumed to be bounded with a known upper bound to implement a Sliding-Mode Control (SMC) law with the aim of achieving efficient head-angle and velocity tracking. Furthermore, to relax the constraint on the uncertainty bound and also to solve the overestimation of switching gain, an adaptive SMC has been proposed to improve the tracking performance.
ResearchGate has not been able to resolve any citations for this publication.
This technical brief investigates virtual holonomic constraints for Euler-Lagrange systems with n degrees-of-freedom and n-1 controls. In our framework, a virtual holonomic constraint is a relation specifying n-1 configuration variables in terms of a single angular configuration variable. The enforcement by feedback of such a constraint induces a desired repetitive behavior in the system. We give conditions under which a virtual holonomic constraint is feasible, i.e, it can be made invariant by feedback, and it is stabilizable. We provide sufficient conditions under which the dynamics on the constraint manifold correspond to an Euler- Lagrange system. These ideas are applied to the problem of swinging up an underactuated pendulum while guaranteeing that the second link does not fall over.
Snake Robots is a novel treatment of theoretical and practical topics related to snake robots: robotic mechanisms designed to move like biological snakes and able to operate in challenging environments in which human presence is either undesirable or impossible. Future applications of such robots include search and rescue, inspection and maintenance, and subsea operations. Locomotion in unstructured environments is a focus for this book.
The text targets the disparate muddle of approaches to modelling, development and control of snake robots in current literature, giving a unified presentation of recent research results on snake robot locomotion to increase the reader’s basic understanding of these mechanisms and their motion dynamics and clarify the state of the art in the field. The book is a complete treatment of snake robotics, with topics ranging from mathematical modelling techniques, through mechatronic design and implementation, to control design strategies. The development of two snake robots is described and both are used to provide experimental validation of many of the theoretical results.
Snake Robots is written in a clear and easily understandable manner which makes the material accessible by specialists in the field and non-experts alike. Numerous illustrative figures and images help readers to visualize the material. The book is particularly useful to new researchers taking on a topic related to snake robots because it provides an extensive overview of the snake robot literature and also represents a suitable starting point for research in this area.
Advances in Industrial Control aims to report and encourage the transfer of technology in control engineering. The rapid development of control technology has an impact on all areas of the control discipline. The series offers an opportunity for researchers to present an extended exposition of new work in all aspects of industrial control.
This article proposes new methodologies for the design of adaptive sliding mode control. The goal is to obtain a robust sliding mode adaptive-gain control law with respect to uncertainties and perturbations without the knowledge of uncertainties/perturbations bound (only the boundness feature is known). The proposed approaches consist in having a dynamical adaptive control gain that establishes a sliding mode in finite time. Gain dynamics also ensures that there is no overestimation of the gain with respect to the real a priori unknown value of uncertainties. The efficacy of both proposed algorithms is confirmed on a tutorial example and while controlling an electropneumatic actuator.
The objective of this chapter is to present advanced control methodologies of uncertain nonlinear systems. Firstly, adaptive
sliding mode controller that retains the system’s robustness in the presence of the bounded uncertainties/perturbations with
unknown bounds is proposed. Due to the on-line adaptation, the proposed approach allows reducing control chattering. Secondly,
a high order sliding mode control strategy that features a priory knowledge of the convergence time is presented. Finally,
the output feedback second order sliding mode controller is presented and discussed. The control algorithms are applied to
experimental set-up equipped by electrical or electropneumatic actuators.
This paper contributes to the understanding of snake robot locomotion by employing nonlinear system analysis tools for investigating fundamental properties of snake robot dynamics. The paper has five contributions: 1) a partially feedback linearized model of a planar snake robot influenced by viscous ground friction is developed. 2) A stabilizability analysis is presented proving that any asymptotically stabilizing control law for a planar snake robot to an equilibrium point must be time-varying. 3) A controllability analysis is presented proving that planar snake robots are not controllable when the viscous ground friction is isotropic, but that a snake robot becomes strongly accessible when the viscous ground friction is anisotropic. The analysis also shows that the snake robot does not satisfy sufficient conditions for small-time local controllability (STLC). 4) An analysis of snake locomotion is presented that easily explains how anisotropic viscous ground friction enables snake robots to locomote forward on a planar surface. The explanation is based on a simple mapping from link velocities normal to the direction of motion into propulsive forces in the direction of motion. 5) A controller for straight line path following control of snake robots is proposed and a Poincaré map is investigated to prove that the resulting state variables of the snake robot, except for the position in the forward direction, trace out an exponentially stable periodic orbit.
Uncertainty and disturbance are common in a planar snake robot model due to its structural complexity and variation in system parameters. To achieve efficient head-angle and velocity tracking with least computational complexity and unknown uncertainty bounds, a Time-Delayed Control (TDC) scheme has been presented in this paper. A Serpenoid gait function is being tracked by the joint angles utilizing Virtual Holonomic Constraints (VHCs) method. The first layer of TDC has been proposed for stabilizing the VHC dynamics to the origin. Once the VHCs are satisfied, the system is said to be on the constraint manifold. The second layer of TDC has been applied to an output system defined over the reduced order dynamics on the constrained manifold. To establish the robustness of the control approach through simulation, uncertainty in the friction coefficients is considered to
be time-varying emulating change in the ground conditions. Simulation results and Lyapunov stability analysis affirm the Uniformly Ultimately Bounded (UUB) Stability of the robot employing the proposed approach.
A planar snake robot model is prone to uncertainties
and disturbances due to its structural complexity and variation
in system parameters. An Adaptive Sliding Mode Control
(ASMC) has been presented in this work to achieve efficient
head-angle and velocity tracking utilizing least average control
input without the knowledge of bound on the uncertainties.
A Virtual Holonomic Constraints (VHCs) approach has been
taken to track the joint angles to a desired gait function. The
ASMC has been applied to the reduced system on the constraint
manifold. The robustness of the control scheme has been verified
against time-varying uncertainty during simulation. Simulation
results and Lyapunov stability analysis is used to show finitetime
stability of the proposed approach.
In this work, we present a Sliding Mode Control (SMC) based approach to address the velocity tracking and head angle control problem of a planar snake robot. The motion characteristics of a snake exhibit the generation of propulsive force as a result of anisotropic friction with respect to the ground. To imitate the motion of a snake, all the joints of the snake robot are tracked to a Serpenoid gait function utilizing Virtual Holonomic Constraints (VHCs). The parameters of the gait function are obtained from the SMC resulting in head-angle control and velocity tracking. SMC has been chosen to ensure robustness and stability of the system in the presence of uncertainties arising from variation in the friction force coefficients between the robot and the ground. Lyapunov’s stability analysis proves the finite-time stability of the system. The control scheme has also been verified and compared with an existing approach through simulation studies.
This paper investigates the problem of planar maneuvering control for bio-inspired underwater snake robots that are exposed to unknown ocean currents. The control objective is to make a neutrally buoyant snake robot which is subject to hydrodynamic forces and ocean currents converge to a desired planar path and traverse the path with a desired velocity. The proposed feedback control strategy enforces virtual constraints which encode biologically inspired gaits on the snake robot configuration. The virtual constraints, parametrized by states of dynamic compensators, are used to regulate the orientation and forward speed of the snake robot. A two-state ocean current observer based on relative velocity sensors is proposed. It enables the robot to follow the path in the presence of unknown constant ocean currents. The efficacy of the proposed control algorithm for several biologically inspired gaits is verified both in simulations for different path geometries and in experiments.
Because of hydrodynamic model error of the present dynamic model, there is a challenge in controller design for the underwater snake-like robot. To tackle this challenge, this paper proposes an adaptive control schemes based on dynamic model for a planar, underwater snake-like robot with model error and time-varying noise. The adaptive control schemes aim to achieve the adaptive control of joint angles tracking and the direction of locomotion control. First, through approximation and reducibility using Taylor expansion method, a simplified dynamics model of a planar amphibious snake-like robot is derived. Then, the L1 adaptive controller based on piecewise constant adaptive law is applied on the simplified planar, underwater snake-like robot, which can deal with both matched and unmatched nonlinear uncertainties. Finally, to control the direction of locomotion, an auxiliary bias signal is used as the control input to regulate the locomotion direction. Simulation results show that this L1 adaptive controller is valid to deal with different uncertainties and achieve the joint angles tracking and fast adaptive at the same time. The modified L1 adaptive controller, in which the auxiliary bias item is added, has the ability to change the direction of locomotion, that is, the orientation angle is periodic with arbitrarily given constant on average.
This paper investigates the problem of maneuvering control for planar snake robots. The control objective is to make the center of mass of the snake robot converge to a desired path and traverse the path with a desired velocity. The proposed feedback control strategy enforces virtual constraints encoding a lateral undulatory gait, parametrized by the states of dynamic compensators used to regulate the orientation and forward speed of the snake robot.
Mobile robots having good terrain adaptability, sufficient payload capability, and high mobility are now urgently in de mand. In this paper, design of a practical mobile robot is attempted, with an inspection task in a nuclear reactor as a concrete objective for development. The configuration of the mobile robot is first discussed. A wheel with crawler track, legs, and a snake-like articulated body are shown to be three fundamental configurations. A hybrid configuration consist ing of an articulated body and a crawler track is most ade quate for the nuclear reactor robot because of its excellent terrain adaptability, sufficient payload capability, and high mobility. Design of the joint structure of the articulated body is discussed. Basic control problems such as signal process ing for tactile sensors and control of statically indeterminant forces are also investigated. A mechanical model KR I, a robot with six articulated body segments, 16 degrees of free dom, length 1391 mm, and weight 27.8 kg, is constructed and several experiments are done to demonstrate the basic mobility of the robot and to show the validity of introducing force control.
Finite-time stability is defined for equilibria of continuous but non-Lipschitzian autonomous systems. Continuity, Lipschitz continuity, and Holder continuity of the settling-time function are studied and illustrated with several examples. Lyapunov and converse Lyapunov results involving scalar differential inequalities are given for finite-time stability. It is shown that the regularity properties of the Lyapunov function and those of the settling-time function are related. Consequently, converse Lyapunov results can only assure the existence of continuous Lyapunov functions. Finally, the sensitivity of finite-time-stable systems to perturbations is investigated.
Presents a guide to sliding mode control for practicing control
engineers. It offers an accurate assessment of the so-called chattering
phenomenon, catalogs implementable sliding mode control design
solutions, and provides a frame of reference for future sliding mode
control research
An effective way to extend to the multi-input case the variable
structure control philosophy is based on a set of m+1 control vectors
forming a simplex in R<sup>m</sup> and on the corresponding switching of
the controlled system from one to another of m+1 different structures.
Yet, some problems arise when uncertainties are present in certain
matrices characterizing the controlled systems. In this paper,
conditions are identified under which, even in the presence of
uncertainty, the convergence to the sliding manifold is ensured via the
application of a multi-input control strategy still based on a simplex
of control vectors
Sliding mode control in electromechanical systems
- V Utkin
- J Guldner
- J Shi
V. Utkin, J. Guldner and J. Shi, "Sliding mode control in electromechanical systems", CRC press, vol. 34, 2009.
Neuro sliding mode control of robotic manipulators
- S Purwar
- I N Kar
- A N Jha
S. Purwar, I. N. Kar and A. N. Jha," Neuro sliding mode control of
robotic manipulators", IEEE Int. Conf. on Robot., Autom. and Mech.,
Singapore, Dec, 2004, pp. 595-600.