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Showing papers in "IEEE Transactions on Control Systems and Technology in 2008"


Journal ArticleDOI
TL;DR: A distributed model predictive control framework, suitable for controlling large-scale networked systems such as power systems, is presented and the distributed MPC algorithm is feasible and closed-loop stable under intermediate termination.
Abstract: A distributed model predictive control (MPC) framework, suitable for controlling large-scale networked systems such as power systems, is presented. The overall system is decomposed into subsystems, each with its own MPC controller. These subsystem-based MPCs work iteratively and cooperatively towards satisfying systemwide control objectives. If available computational time allows convergence, the proposed distributed MPC framework achieves performance equivalent to centralized MPC. Furthermore, the distributed MPC algorithm is feasible and closed-loop stable under intermediate termination. Automatic generation control (AGC) provides a practical example for illustrating the efficacy of the proposed distributed MPC framework.

774 citations


Journal ArticleDOI
TL;DR: A dynamic model of the THS powertrain is developed and then applied for model-based control development, and two control algorithms are introduced: one based on the stochastic dynamic programming method, and the otherbased on the equivalent consumption minimization strategy.
Abstract: Toyota hybrid system (THS) is used in the current best selling hybrid vehicle on the market-the Toyota Prius. This hybrid system contains a power-split planetary gear system which combines the benefits of series and parallel hybrid vehicles. In this paper, we developed a dynamic model of the THS powertrain and then apply it for model-based control development. Two control algorithms are introduced: one based on the stochastic dynamic programming method, and the other based on the equivalent consumption minimization strategy. Both approaches determine the engine power based on the overall vehicle efficiency and apply the electrical machines to optimize the engine operation. The performance of these two algorithms is assessed by comparing against the dynamic programming results, which are non-causal but provide theoretical benchmarks for other implementable control algorithms.

619 citations


Journal ArticleDOI
TL;DR: A novel methodology for high-level control and coordination of autonomous vehicle teams and its demonstration on high-fidelity models of the organic air vehicle developed at Honeywell Laboratories is described.
Abstract: This paper describes the application of a novel methodology for high-level control and coordination of autonomous vehicle teams and its demonstration on high-fidelity models of the organic air vehicle developed at Honeywell Laboratories. The scheme employs decentralized receding horizon controllers that reside on each vehicle to achieve coordination among team members. An appropriate graph structure describes the underlying communication topology between the vehicles. On each vehicle, information about neighbors is used to predict their behavior and plan conflict-free trajectories that maintain coordination and achieve team objectives. When feasibility of the decentralized control is lost, collision avoidance is ensured by invoking emergency maneuvers that are computed via invariant set theory.

263 citations


Journal ArticleDOI
TL;DR: The glider coordinated control system (GCCS) uses a detailed glider model for prediction and a simple particle model for planning to steer a fleet of underwater gliders to a set of coordinated trajectories.
Abstract: The glider coordinated control system (GCCS) uses a detailed glider model for prediction and a simple particle model for planning to steer a fleet of underwater gliders to a set of coordinated trajectories. The GCCS also serves as a simulation testbed for the design and evaluation of multivehicle control laws. In this brief, we describe the GCCS and present experimental results for a virtual deployment in Monterey Bay, CA and a real deployment in Buzzards Bay, MA.

236 citations


Journal ArticleDOI
TL;DR: An algorithm to monitor an environmental boundary with mobile agents to optimally approximate the boundary with a polygon is proposed and an algorithm that distributes the vertices of the approximating polygon uniformly along the boundary is designed.
Abstract: In this brief, we propose and analyze an algorithm to monitor an environmental boundary with mobile agents. The objective is to optimally approximate the boundary with a polygon. The mobile sensors rely only on sensed local information to position some interpolation points and define an approximating polygon. We design an algorithm that distributes the vertices of the approximating polygon uniformly along the boundary. The notion of uniform placement relies on a metric inspired by approximation theory for convex bodies. The algorithm is provably convergent for static boundaries and efficient for slowly-moving boundaries because of certain input-to-state stability properties.

219 citations


Journal ArticleDOI
TL;DR: This brief illustrates how the amalgamation of an adaptive model-based feedforward term (for linearly parameterized uncertainty) with a robust integral of the sign of the error (RISE) feedback term can be used to yield an asymptotic tracking result for Euler-Lagrange systems that have mixed unstructured and structured uncertainty.
Abstract: The control of systems with uncertain nonlinear dynamics has been a decades-long mainstream area of focus. The general trend for previous control strategies developed for uncertain nonlinear systems is that the more unstructured the system uncertainty, the more control effort (i.e., high gain or high-frequency feedback) is required to cope with the uncertainty, and the resulting stability and performance of the system is diminished (e.g., uniformly ultimately bounded stability). This brief illustrates how the amalgamation of an adaptive model-based feedforward term (for linearly parameterized uncertainty) with a robust integral of the sign of the error (RISE) feedback term (for additive bounded disturbances) can be used to yield an asymptotic tracking result for Euler-Lagrange systems that have mixed unstructured and structured uncertainty. Experimental results are provided that illustrate a reduced root-mean-squared tracking error with reduced control effort.

217 citations


Journal ArticleDOI
TL;DR: A constructive method is presented to design cooperative controllers that force a group of N unicycle-type mobile robots with limited sensing ranges to perform desired formation tracking, and guarantee no collisions between the robots.
Abstract: A constructive method is presented to design cooperative controllers that force a group of N unicycle-type mobile robots with limited sensing ranges to perform desired formation tracking and guarantee no collisions between the robots. Physical dimensions and dynamics of the robots are also considered in the control design. Smooth and p times differential bump functions are introduced and incorporated into novel potential functions to design a formation tracking control system. Despite the robot limited sensing ranges, no switchings are needed to solve the collision avoidance problem. Simulations illustrate the results.

217 citations


Journal ArticleDOI
TL;DR: Online learning and control using neural network of a wheel-driven mobile inverted pendulum system is presented, showing the robustness of the proposed controller even when outer impacts as disturbance are present.
Abstract: The mobile inverted pendulum is developed and tested for an intelligent control experiment of control engineers. Intelligent control algorithms are tested for the control experiment of a low cost mobile inverted pendulum system. Online learning and control using neural network of a wheel-driven mobile inverted pendulum system is presented. Neural network learning algorithm is embedded on a digital signal processing board along with primary proportional-integral-differential controllers to achieve real time control. Without knowing dynamics of the system, uncertainties in system dynamics are compensated by neural network in an online fashion. Digital filters are designed for a gyro sensor to compensate for a phase lag. Experimental studies of balancing the pendulum and tracking the desired trajectory of the cart for one dimensional motion are conducted. Results show the robustness of the proposed controller even when outer impacts as disturbance are present.

199 citations


Journal ArticleDOI
TL;DR: Sufficient stability and convergence properties for the combined system are presented along with a modified approach for determining monotonic convergence of systems that are computationally challenging.
Abstract: This paper presents an improved method for precision motion control by combining individual axis iterative learning control (ILC) and cross-coupled ILC (CCILC) into a single control input. CCILC is a new method in which a multi-axis cross-coupled controller (CCC) is reformatted into a single-input single-output (SISO) ILC format. Applying the techniques of ILC to CCC enables learning of the cross-coupled error which leads to a modified control signal and subsequent improvements in the contour trajectory tracking performance. In this paper, performance of the combined ILC and CCILC system is compared to standard feedback control through computer simulations and experimental testing on a Cartesian robotic system. Sufficient stability and convergence properties for the combined system are presented along with a modified approach for determining monotonic convergence of systems that are computationally challenging. The combined design is shown to enhance the precision motion control of the robotic system through performance improvements in individual axis tracking and contour tracking.

193 citations


Journal ArticleDOI
TL;DR: A nonlinear adaptive robust control method is presented for a single-rod electro-hydraulic actuator with unknown nonlinear parameters and shows that the nonlinear control algorithm, together with the adaptation scheme, gives a good performance for the specified tracking task in the presence of unknown non linear parameters.
Abstract: In this paper, a nonlinear adaptive robust control method is presented for a single-rod electro-hydraulic actuator with unknown nonlinear parameters. Previous adaptive control methods of hydraulic systems always assume that the system's unknown parameters occur linearly, but, in a practical hydraulic system, unknown nonlinear parameters, which enter the system equations in a nonlinear way, are common; for example, when the original control volumes are unknown or change, uncertain nonlinear parameters will exist. The proposed control method in this paper is to present a nonlinear adaptive controller with adaptation laws to compensate for the uncertain nonlinear parameters due to the varieties of the original control volumes. The main feature of the scheme is that a novel-type Lyapunov function is developed to construct an asymptotically stable adaptive controller and adaptation laws. Furthermore, by combining backstepping techniques and a simple robust control method, the whole system's controller and adaptation laws are presented, which can compensate for all unknown parameters and uncertain nonlinearities. The experimental results show that the nonlinear control algorithm, together with the adaptation scheme, gives a good performance for the specified tracking task in the presence of unknown nonlinear parameters.

187 citations


Journal ArticleDOI
TL;DR: A hybrid converter model that is valid for the whole operating regime, and an a posteriori analysis proves, by deriving a piecewise-quadratic Lyapunov function, that the closed-loop system is exponentially stable.
Abstract: DC-DC converters pose challenging hybrid control problems, since the semiconductor switches induce different modes of operation and several constraints (on the duty cycle and the inductor current) are present. In this paper, we propose a novel approach to the modeling and controller design problem for fixed-frequency DC-DC converters, using a synchronous step-down DC-DC converter as an illustrative example. We introduce a hybrid converter model that is valid for the whole operating regime. Based on this model, we formulate and solve a constrained optimal control problem. To make the scheme implementable, we derive offline the explicit state-feedback control law, which can be easily stored and implemented in a lookup table. A Kalman filter is added to account for unmeasured load variations and to achieve zero steady-state output voltage error. An a posteriori analysis proves, by deriving a piecewise-quadratic Lyapunov function, that the closed-loop system is exponentially stable. Simulation results demonstrate the potential advantages of the proposed control methodology.

Journal ArticleDOI
TL;DR: A sliding-mode approach for fault-tolerant control of a civil aircraft, where both actuator and sensor faults are considered, and the novelty lies in the application of the sensor fault reconstruction scheme to correct the corrupted measured signals before they are used by the controller.
Abstract: This paper presents a sliding-mode approach for fault-tolerant control of a civil aircraft, where both actuator and sensor faults are considered. For actuator faults, a controller is designed around a state-feedback sliding-mode scheme where the gain of the nonlinear unit vector term is allowed to adaptively increase at the onset of a fault. Unexpected deviation of the switching variables from their nominal condition triggers the adaptation mechanism. The controller proposed here is relatively simple and yet is shown to work across the entire "up and away" flight envelope. For sensor faults, the application of a robust method for fault reconstruction using a sliding-mode observer is considered. The novelty lies in the application of the sensor fault reconstruction scheme to correct the corrupted measured signals before they are used by the controller, and therefore the controller does not need to be reconfigured.

Journal ArticleDOI
Dongbing Gu1
TL;DR: A receding horizon approach is adopted to synthesize a state-feedback controller for the formation control of mobile robots as a linear-quadratic Nash differential game through the use of graph theory.
Abstract: This paper presents a differential game approach to formation control of mobile robots. The formation control is formulated as a linear-quadratic Nash differential game through the use of graph theory. Finite horizon cost function is discussed under the open-loop information structure. An open-loop Nash equilibrium solution is investigated by establishing existence and stability conditions of the solutions of coupled (asymmetrical) Riccati differential equations. Based on the finite horizon open-loop Nash equilibrium solution, a receding horizon approach is adopted to synthesize a state-feedback controller for the formation control. Mobile robots with double integrator dynamics are used in the formation control simulation. Simulation results are provided to justify the models and solutions.

Journal ArticleDOI
TL;DR: Simulation results are presented for the hover stabilization of an airship UAV, which are demonstrative of the excellent performance of the proposed controller and illustrate its robustness in face of wind disturbances.
Abstract: This brief presents a backstepping-based controller with input saturations, applicable for the hover flight of an unmanned aerial vehicle (UAV). A dynamic model for a generic UAV is introduced that is valid for quasi-stationary conditions, with quaternion formulation of the kinematics equations. Based on this model, a backstepping design formulation is deduced for UAV hover control, and its global asymptotic stability is demonstrated. In order to cope with limitations due to reduced actuation, saturations are introduced in the control design, and the stability of the modified control solution is verified. Simulation results are presented for the hover stabilization of an airship UAV, which are demonstrative of the excellent performance of the proposed controller and illustrate its robustness in face of wind disturbances.

Journal ArticleDOI
TL;DR: The input-to-state stability (ISS) property of the overall nonlinear control system is proven and leads to a major contribution of construction of a theoretically guaranteed robust nonlinear controller with DOB.
Abstract: In this brief, a novel robust nonlinear motion controller with disturbance observer (DOB) for positioning control of a nonlinear single-input-single-output (SISO) mechanical system is proposed. The controller is designed in a backstepping manner. First, a proportional-integral (PI) controller is designed to stabilize the position error. Consequently, a novel robust nonlinear velocity controller with DOB is designed to stabilize the velocity error. With the help of nonlinear damping terms, the input-to-state stability (ISS) property of the overall nonlinear control system is proven, which leads to a major contribution of construction of a theoretically guaranteed robust nonlinear controller with DOB. The performance of the proposed controller is verified through application to a magnetic levitation system. Comparative studies with an adaptive robust nonlinear controller are also carried out. It is shown that the proposed novel controller while being simple is superior over the adaptive robust nonlinear controller for the experimental setup under study.

Journal ArticleDOI
TL;DR: The design of an adaptive cruise controller for a Smart car, a type of small car, is proposed as a benchmark setup for several model predictive control methods for nonlinear and piecewise affine systems, to assess the main properties, characteristics, and strong/weak points of each method.
Abstract: The design of an adaptive cruise controller for a Smart car, a type of small car, is proposed as a benchmark setup for several model predictive control methods for nonlinear and piecewise affine systems. Each of these methods has been already applied to specific case studies, different from method to method. This paper has therefore the purpose of implementing and comparing them over a common benchmark, allowing us to assess the main properties, characteristics, and strong/weak points of each method. In the simulations, a realistic model of the Smart car, including gear box and engine nonlinearities, is considered. A description of the methods to be compared is presented, and the comparison results are collected in a table. In particular, the tradeoffs between complexity and accuracy of the solution, as well as computational aspects are highlighted.

Journal ArticleDOI
TL;DR: It is shown that passivity can be maintained in the face of varying delay and packet loss but that it depends fundamentally on the mechanism used to handle missing packets.
Abstract: In this brief, we propose a passivity-based framework for control of bilateral teleoperators under time-varying delays and data loss. The usual scattering formalism which guarantees passivity for any constant time delay is extended in several important ways to handle adverse network dynamics. Communication management modules (CMM) are proposed to reconstruct the scattering variables while guaranteeing passivity of the bilateral teleoperator and asymptotic stability of the master/slave velocities under time-varying delays and data losses. The results are also extended to the discrete domain, in particular to the case where communication between the master and slave robots occurs over a packet-switched network. We show that passivity can be maintained in the face of varying delay and packet loss but that it depends fundamentally on the mechanism used to handle missing packets. Our framework unifies several existing results in the continuous and discrete time domain. We develop novel algorithms for the CMM which not only preserve passivity and stability, but have been shown through experiments to improve tracking performance in a single-degree-of-freedom teleoperator system.

Journal ArticleDOI
TL;DR: A new modeling approach and control law for pneumatic servo actuators are presented and the use of novel bipolynomial functions to model the valve flow rates is shown to produce a more accurate solution than prior approaches.
Abstract: Pneumatic actuators are low-cost, safe, clean, and exhibit a high power to weight ratio. In this paper a new modeling approach and control law for pneumatic servo actuators are presented. The nonlinear system model is developed using a combination of mechanistic and empirical methods. The use of novel bipolynomial functions to model the valve flow rates is shown to produce a more accurate solution than prior approaches. A novel multiple-input single-output nonlinear position control law is designed using the backstepping methodology. The stability analysis includes the effects of friction modeling error and valve modeling error. Experiments are conducted with 9.5-mm bore and 6.4-mm bore pneumatic cylinders, and four low-cost two-way proportional valves. In experiments with the 9.5-mm bore cylinder and a 1.5-kg moving mass, maximum tracking errors of plusmn0.5 mm for a 1-Hz sine wave trajectory, and steady-state errors within plusmn0.05 mm for an S-curve trajectory were achieved.

Journal ArticleDOI
TL;DR: Experimental results demonstrate significant merits of the proposed control system compared against those obtained by conventional mapping/calibration-based approaches.
Abstract: This paper describes a hybrid robust nonlinear control approach for modern diesel engines operating multiple combustion modes; in particular, low temperature combustion and conventional diesel combustion modes. An innovative control system is designed to track different key engine air-path operating variables at different combustion modes as well as to avoid singularity which is inherent for turbocharged diesel engine running multiple combustion modes. The overall system consists of a finite-state machine-based supervisory controller and multivariable sliding mode controllers with integral actions in sliding surfaces for different combustion modes. The system controlled outputs for different combustion mode controllers are carefully chosen with respect to combustion characteristics as well as sensor/measurement limitations. The performance of the control system is evaluated on a modern light-duty diesel engine. Experimental results demonstrate significant merits of the proposed control system compared against those obtained by conventional mapping/calibration-based approaches.

Journal ArticleDOI
TL;DR: A new model for shape memory alloy (SMA) actuators based on the physics of the process is described and control strategies using the model are developed, showing fast and accurate control of the strain in the SMA actuator.
Abstract: This brief describes a new model for shape memory alloy (SMA) actuators based on the physics of the process and develops control strategies using the model. The model consists of three equations - the temperature dynamics described by Joules heating-convectional cooling, the mole fraction distribution with temperature given by statistics to describe a two state system, and a constitutive equation relating the changes in temperature and mole fraction to the stress and strain induced in the SMA. This model is used to develop two control schemes for controlling the strain in an SMA actuator. The first control scheme describes a gain-scheduled proportional-integral (PI) controller, the gains of which are obtained by means of linear quadratic regulator (LQR) optimization. The second control scheme is an Hinfin loop-shaping controller using normalized coprime stabilization which ensures robust stability by minimizing the effect of unmodeled dynamics at high frequencies. Simulation and experimental results show fast and accurate control of the strain in the SMA actuator for both control schemes.

Journal ArticleDOI
TL;DR: The design and experimental results of a novel output feedback controller for slender-body underwater vehicles derived using model-based design techniques and proved to be asymptotically stable using Lyapunov and cascaded systems theory are presented.
Abstract: This paper presents the design and experimental results of a novel output feedback controller for slender-body underwater vehicles. The controller is derived using model-based design techniques. Two separate control plant models are employed: a 3-degree-of-freedom (DOF) current-induced vessel model accounting for the current loads acting on the vehicle and a 5-DOF model describing the vehicle dynamics. The main design objective behind this strategy is to incorporate the vehicle dynamics when estimating the current influence on the vehicle. Furthermore, the transit model is based on the notion of constant propeller revolution resulting in a partly linearized model, which subsequently leads to perspicuous and implementable controller and observer structures. The controller is derived using the observer backstepping technique, and the closed loop is proved to be asymptotically stable using Lyapunov and cascaded systems theory. The control objective is to track the desired pitch and heading angle generated by the line-of-sight guidance system while keeping constant forward thrust. Experimental results demonstrate successful performance of the proposed output feedback controller implemented on the Minesniper MkII AUV/ROV.

Journal ArticleDOI
TL;DR: This paper illustrates that MPC can be implemented on inexpensive hardware at high sampling rates using traditional online quadratic programming methods for nontrivial models and with significant control performance dividends.
Abstract: The difficulties imposed by actuator limitations in a range of active vibration and noise control problems are well recognized. This paper proposes and examines a new approach of employing model predictive control (MPC). MPC permits limitations on allowable control action to be explicitly included in the computation of an optimal control action. Such techniques have been widely and successfully applied in many other areas. However, due to the relatively high computational requirements of MPC, existing applications have been limited to systems with slow dynamics. This paper illustrates that MPC can be implemented on inexpensive hardware at high sampling rates using traditional online quadratic programming methods for nontrivial models and with significant control performance dividends.

Journal ArticleDOI
TL;DR: A special class of positive definite functions is employed to formulate the control methodology such that the closed-loop system stability can be guaranteed and a precise tracking ability in following a specified motion trajectory is demonstrated in the experimental study.
Abstract: This paper proposes a sliding-mode enhanced adaptive control methodology for piezoelectric actuation systems to track specified motion trajectories. This control methodology is proposed to overcome the problems of unknown or uncertain system parameters, nonlinearities including the hysteresis effect, and external disturbances in the piezoelectric actuation systems, without any form of feedforward compensation. In this paper, a special class of positive definite functions is employed to formulate the control methodology such that the closed-loop system stability can be guaranteed. The control formulation, stability analysis, and analytical closed-loop solution are presented. Furthermore, a precise tracking ability in following a specified motion trajectory is demonstrated in the experimental study. With the capability of motion tracking under the aforementioned conditions, the sliding-mode enhanced adaptive control methodology is very attractive in realising high-performance control applications in the field of micro/nano manipulation.

Journal ArticleDOI
TL;DR: This brief is concerned with the problem of nonlinear fault detection, isolation, and recovery for the satellite's orbital and attitude models through construction of residual generators that are based on least-squares parameter estimation techniques.
Abstract: This brief is concerned with the problem of nonlinear fault detection, isolation, and recovery (FDIR) for the satellite's orbital and attitude models through construction of residual generators that are based on least-squares parameter estimation techniques. By viewing system anomalies caused by faults and/or malfunctions as changes of certain parameters in the system, our goal is to detect, isolate, and recover from faults through estimating these parameters and adaptively redesigning and reconfiguring the controllers. The convergence and robustness properties of the residual generators are analytically and experimentally investigated. Furthermore, the corresponding decision logic and thresholds for fault diagnosis are properly selected and specified. Numerical simulation results for the proposed technique as applied to nonlinear satellite models are presented to demonstrate its performance capabilities.

Journal ArticleDOI
TL;DR: It is analytically demonstrated that the proposed teleoperation architecture is capable of providing ideal transparency when transmission delays are present, and criteria for its stable operation are derived and it is shown that a three-channel variant of the proposed four-channel control architecture can offer a comparable performance with less implementational complexity.
Abstract: Besides stability, a high degree of transparency is also an essential requirement in order to enable operators to safely and precisely perform bilateral teleoperation tasks. An existing approach based on the wave transformation technique can make a two-channel teleoperation system insensitive to time delays by making the time-delayed communication channel passive. In this paper, we propose a novel method for incorporating this technique in a four-channel architecture, which is the optimal architecture from a transparency point of view, and derive the corresponding absolute stability condition. It is analytically demonstrated that the proposed teleoperation architecture is capable of providing ideal transparency when transmission delays are present, and criteria for its stable operation are derived. We also show that a three-channel variant of the proposed four-channel control architecture can offer a comparable performance with less implementational complexity. Experimental results in support of the developed theory are provided.

Journal ArticleDOI
TL;DR: The nonlinear Saint-Venant equations are considered as a system of two conservation laws perturbed by non-homogeneous terms, and a new strategy is derived which ensures that the water level and water flow converge to the equilibrium.
Abstract: The problem of the stabilization of the flow in a reach is investigated. To study this problem, we consider the nonlinear Saint-Venant equations, written as a system of two conservation laws perturbed by non-homogeneous terms. The non-homogeneous terms are due to the effects of the bottom slope, the slope's friction, and also the lateral supply. The boundary actions are defined as the position of both spillways located at the extremities of the reach. It is assumed that the height of the flow is measured at both extremities. Assuming that the non-homogeneous terms are sufficiently small in C 1-norm, we design stabilizing boundary output feedback controllers, i.e., we derive a new strategy which depends only on the output and which ensures that the water level and water flow converge to the equilibrium. Moreover, the speed of the convergence is shown to be exponential. The proof of this result is based on the estimation of the effects on the non-homogeneous terms on the evolution of the Riemann coordinates. This stability result is validated both by simulating on a real river data and by experimenting on a micro-channel setup.

Journal ArticleDOI
TL;DR: The proposed control scheme uses real-time kinematic (RTK)-GPS and other aiding sensors to measure the WMR's posture, velocities, and perturbations due to wheel skidding and slipping to compensate the path following errors based on a backstepping controller.
Abstract: Most wheeled mobile robot (WMR) controllers have been developed based on nonskidding and nonslipping assumptions. Unfortunately, wheel skidding and slipping are inevitable due to wheel tire-deformation; consequently, the stability and performance of these controllers are not guaranteed. This brief aims to develop a global positioning system (GPS)-based path following a controller for a car-like wheeled mobile robot in the presence of wheel skidding and slipping. The proposed control scheme uses real-time kinematic (RTK)-GPS and other aiding sensors to measure the WMR's posture, velocities, and perturbations due to wheel skidding and slipping. These measurements are applied to compensate the path following errors based on a backstepping controller. The reported experimental results validate the control scheme. With this solution, the WMR is able to maneuver with better precision in outdoor environments in the presence of wheel skidding and slipping.

Journal ArticleDOI
TL;DR: A constructive approach for adaptive NN control design with guaranteed stability is proposed, considering both full-state and output feedback cases, and it is shown that the output tracking error converges to a small neighborhood of the origin, while the remaining closed-loop signals remain bounded.
Abstract: In this brief, robust adaptive neural network (NN) control is presented for helicopters in vertical flight, with dynamics in single-input-single-output (SISO) nonlinear nonaffine form. Based on the use of the implicit function theorem and the mean value theorem, we propose a constructive approach for adaptive NN control design with guaranteed stability. Considering both full-state and output feedback cases, it is shown that the output tracking error converges to a small neighborhood of the origin, while the remaining closed-loop signals remain bounded. The simulation study demonstrates the effectiveness of the proposed control.

Journal ArticleDOI
Wei Ren1, Haiyang Chao1, W. Bourgeous1, N. Sorensen1, YangQuan Chen1 
TL;DR: The experimental results show the effectiveness and robustness of the consensus algorithms even in the presence of platform physical limitations, packet loss, information delay, etc.
Abstract: In this brief, consensus algorithms are experimentally implemented and validated on a mobile actuator and sensor network platform under directed, possibly switching interaction topologies to explore issues and challenges in distributed multivehicle cooperative control. Distributed consensus algorithms are applied to two target applications including rendezvous and axial alignment. In the rendezvous application, multiple mobile robots simultaneously arrive at a common a priori unknown target location determined through team negotiation. In the axial alignment application, multiple mobile robots collectively align their final positions along a line. The experimental results show the effectiveness and robustness of the consensus algorithms even in the presence of platform physical limitations, packet loss, information delay, etc. These experimental results validate the corresponding theoretical results.

Journal ArticleDOI
TL;DR: A two-level coordinated control scheme is proposed: the task-level configures the valve usage for maximal energy saving and the valve-level utilizes adaptive robust control (ARC) technique to guarantee the closed-loop system stability and performance under various model uncertainties and disturbances.
Abstract: As applications of electro-hydraulic systems become increasingly widespread, the demand for low cost, high-level control performance and significant energy saving schemes gets stronger and stronger. The recently developed energy-saving programmable valves, a unique configuration of five independently controlled poppet type cartridge valves, provide hardware possibility to meet the demand. Preliminary research work has shown that the program valves' increased flexibility and controllability lead to significant energy-saving, due to the reduced working pressures of the hydraulic actuators and the full use of free regeneration cross-port flows. However, the increased hardware flexibility also results in increased complexity in controlling the system: for each system, instead of one control input to be synthesized to meet the sole objective of control performance, five control inputs have to be simultaneously determined for all five poppet valves to achieve the dual objectives of both high precision control performance and significant energy saving. This paper proposes a two-level coordinated control scheme: the task-level configures the valve usage for maximal energy saving and the valve-level utilizes adaptive robust control (ARC) technique to guarantee the closed-loop system stability and performance under various model uncertainties and disturbances. Comparative experimental results were obtained to show the high precision control performance and significant energy saving achieved with the proposed low-cost programmable valves.