Cooperative Control Algorithm Research Articles

Fault tolerant cooperative control for multiple unmanned aerial vehicle systems with plugging operations

A tracking problem for a group of multiple unmanned aerial vehicle (Multi-UAV) systems with agent faults is investigated. A neighbouring rule-based cooperative control algorithm is proposed such that the Multi-UAV systems can follow the common reference signals in a fault free situation. Once in the presence of faults that change the dynamics of the agents, a fault tolerant cooperative control strategy based on the plugging operations (with a minor adjustment of connection) is employed in order to make each agent continue to follow the reference signals without increasing the number of weak points. Moreover, the utilised plugging operations do not need to reconfigure any individual’s self control law or stop the faulty agents. Simulation results show the effectiveness of the proposed methods.

Cooperative control of the motor and the electric booster brake to improve the stability of an in-wheel electric vehicle

A cooperative control algorithm for an in-wheel motor and an electric booster brake is proposed to improve the stability of an in-wheel electric vehicle. The in-wheel system was modeled by dividing it into motor and mechanical parts, and the electric booster brake was modeled through tests. In addition, the response characteristics of the in-wheel system and the electric booster brake were compared through a frequency response analysis. In the cooperative control, the road friction coefficient was estimated using the wheel speed, motor torque, and braking torque of each wheel, and the torque limit of the wheel to the road was determined using the estimated road friction coefficient. Based on the estimated road friction coefficient and torque limit, a cooperative algorithm to control the motor and the electric booster brake was proposed to improve the stability of the in-wheel electric vehicle. The performance of the proposed cooperative control algorithm was evaluated through a hardware-in-the-loop simulation (HILS). Furthermore, to verify the performance of the proposed cooperative control algorithm, a test environment was constructed for the anti-lock braking system (ABS) hydraulic module hardware, and the performance of the cooperative control algorithm was compared with that of the ABS by means of a HILS test.

Robust optimal motion planning approach to cooperative grasping and transporting using multiple UAVs based on SDRE

In this paper, we consider the problem of controlling a team of Quadrotors that cooperatively grasp and transport a common payload in three dimensions in the presence of external disturbances and parametric uncertainties such as wind field effects. The main contribution of this work is to propose a cooperative control algorithm based on a decentralized strategy. This algorithm consists of two main parts: first calculating the control vectors for each Quadrotor using Moore–Penrose theory and second combining these control vectors with individual control vectors, which are obtained from a closed-loop non-linear robust optimal controller. In this regard, a robust optimal sliding mode controller (ROSMC), which incorporates the state-dependent Riccati equation (SDRE) method with sliding mode control (SMC) technique, is designed. It also has the capability of maximum dynamic load carrying capacity (DLCC) to increase the carrying capacity and the efficiency of the group of Quadrotors. The proposed method inherits the advantages of both approaches including robustness against model uncertainties and high flexibility in designing the control parameters to provide an optimal solution for the non-linear dynamic of the system. The control algorithm is based on the Lyapunov technique, which is able to provide the stability of the end-effecter during tracking of the desired trajectory with acceptable precision. Finally, the simulation results demonstrate the effectiveness of the control strategy for the cooperative Quadrotors to grasp and transport a common payload in various manoeuvres.

V2X-Based Decentralized Cooperative Adaptive Cruise Control in the Vicinity of Intersections

Cooperative driving with V2X communication is widely researched due to its considerable potential to improve the safety and efficiency of road transportation systems. In this paper, a decentralized cooperative adaptive cruise control algorithm using V2X for vehicles in the vicinity of intersections (CACC-VI) is proposed. This algorithm is designed to improve the throughput of intersection by reorganizing the vehicle platoons around it, in consideration of safety, fuel consumption, speed limit, heterogeneous features of vehicles, and passenger comfort. Within a platoon, vehicles try to find the optimal control input by a distributed particle swarm optimization (PSO) algorithm, in order to reduce tracking errors, while respecting different constraints. A concept of opportunity space is proposed to facilitate platoon reorganization, in which a subplatoon or an individual vehicle can choose to accelerate to join in the preceding platoon or to decelerate to depart from the current one. The main idea is to make full use of the road capacity and to distribute it to most vehicles that are capable to find an accelerating trajectory to get through the intersection within a limited period. The originality of our algorithm is the introduction of a novel application of V2X communication to make the traffic more intelligent, in terms of safety, time saving, and environment friendly.

Terminal sliding mode-based cooperative tracking control for non-linear dynamic systems

This paper investigates cooperative tracking problems for multiple non-linear dynamic systems. The desired trajectory is only available to a portion of the agents. Treating the desired trajectory as a virtual agent, a terminal sliding mode (TSM)-based distributed control algorithm is designed only using the neighbours’ information. A decentralized observer is provided firstly to estimate the unknown external disturbances. Then, the Gaussian functions are introduced to approximate the second-order derivative of the inaccessible states. On this basis, we further develop a TSM-based cooperative tracking control algorithm for the non-linear dynamic systems such that the tracking errors of each agent converge to an adjustable neighbourhood of the origin in finite time. Finally, a simulation example is presented to illustrate the feasibility and effectiveness of the proposed approaches.

Improving the Intersection’s Throughput using V2X Communication and Cooperative Adaptive Cruise Control

In this paper, a decentralized cooperative adaptive cruise control algorithm for vehicles in the vicinity of intersections (CACC-VI) is proposed. This algorithm is designed to make use of the road capacity to let more vehicles get through the intersection within a limited traffic signal period in consideration of safety, fuel consumption, speed limit and heterogeneous features of vehicles, and passenger comfort. Within a platoon, vehicles try to find the optimal control input by a distributed PSO algorithm in order to reduce tracking errors while respecting different constraints. A concept of opportunity space is proposed to facilitate platoon reorganization in which a sub-platoon or an individual vehicle can choose to accelerate to join in the preceding platoon or to decelerate to depart from the current one. It is found that the throughput of the intersection during the green phase can be improved, and an optimal control input can be found for each vehicle within the defined constraints.

Cooperative distributed model predictive control of multiple coupled linear systems

This study presents a cooperative distributed model predictive control (CDMPC) algorithm for a team of linear subsystems with the coupled cost and coupled constraints. At each sampling time, all the subsystems are permitted to synchronously optimise. An improved compatibility constraint, which plays an important to ensure the stability, is constructed to ensure that the actual state trajectory of each subsystem does not deviate too much from its assumed one. Moreover, a positive invariant terminal set and an associated terminal cost (a local control-Lyapunov function) are designed in the distributed manner. By applying the proposed algorithm, the recursive feasibility with respect to both local and coupled constraints and the closed-loop stability of the whole system are ensured. In final, the numerical results of the comparisons between the CDMPC algorithm and the centralised model predictive control are given to show the effectiveness of the proposed algorithm.

Differential Game Theoretic Approach for Distributed Dynamic Cooperative Power Control in Cognitive Radio Ad Hoc Networks

In this paper, we investigate the differential game theoretic approach for distributed dynamic cooperative power control in cognitive radio ad hoc networks (CRANETs). First, a payoff function is defined by taking into consideration the tradeoff between the stock of accumulated power interference to the primary networks and the dynamic regulation of the transmit power of secondary users (SUs). Specifically, the payoff function not only reflects the tradeoff between the requirement for quickly finding the stable available spectrum opportunities and the need for better channel conditions, but also reveals the impact of the differentiated types of data traffic on the demand of transmission quality. Then the dynamic power control problem is modeled as a differential game model. Moreover, we convert the differential game model into a dynamic programming problem to obtain a set of optimal strategies of SUs under the condition of the grand coalition. A distributed dynamic cooperative power control algorithm is developed to dynamically adjust the transmit power of SUs under grand coalition. Finally, numerical results are presented to demonstrate the effectiveness of the proposed algorithm for efficient power control in CRANETs.

Cooperative distributed stochastic MPC for systems with state estimation and coupled probabilistic constraints

A cooperative distributed stochastic model predictive control (CDSMPC) algorithm is given for multiple dynamically decoupled subsystems with additive stochastic disturbances and coupled probabilistic constraints, for which states are not measurable. Cooperation between subsystems is promoted by a scheme in which a local subsystem designs hypothetical plans for others in some cooperating set, and considers the weighted costs of these subsystems in its objective. To achieve satisfaction of coupled probabilistic constraints in a distributed way, only one subsystem is permitted to optimize at each time step. In addition, by using a lifting technique and the probabilistic information on additive disturbances, measurement noise and the state estimation error, a set of deterministic constraints is constructed for the predictions of nominal models. Recursive feasibility with respect to both local and coupled probabilistic constraints is guaranteed and stability for any choice of update sequence and any structure of cooperation is ensured. Numerical examples illustrate the efficacy of the proposed algorithm.

Cooperative Control Algorithm for Friction and Regenerative Braking Systems Considering Temperature Characteristics

In a hybrid electric vehicle (HEV), the braking system is composed of friction braking and regenerative braking. When a driver presses the brake pedal, each braking system collaborates and applies braking torque. The friction brake is a hydraulic system which has a slow response time and the regenerative brake is an electric system which responds quickly. Such characteristics bring a control problem, especially transient characteristic of shifts between regenerative brake and friction brake, because the hydraulic system cannot follow the response time of the electric system. The friction braking torque is also governed by the friction coefficient which changes with temperature. This causes the braking torque to be generated differently with the demanded braking torque, without considering the temperature. Due to these problems, the driver would feel uncomfortable and the vehicle would be unstable resulting from the difference in response time and variance of the friction coefficient when pressing the brake pedal. Hence, it is essential to coincide the settling time of friction and regenerative braking system regarding the temperature. To solve these problems, the hydraulic system was mathematically modelled using the flow and continuity equations and the electric system was modelled using the d-q transformation and voltage equation. The temperature estimation model of the brake components was developed using the heat transfer methods which are conduction, convection and semi-infinite solid. The brake temperature was calculated by the finite difference method (FDM). With the mathematical model of hydraulic and electric systems, the coincidence control for the settling time of both systems was established. It was also possible to find the friction coefficient and calculate the braking torque by using the temperature estimator. In this paper, the numerical simulation was carried out to verify these control algorithms. The difference in response time between friction and regenerative braking system was reduced and the transient characteristic was improved. Also, the braking torque was compensated with the temperature, and the difference between demanded and actual braking torque lessen using the algorithms.

Distributed cooperative control design for finite‐time attitude synchronisation of rigid spacecraft

Two finite-time control algorithms are developed for distributed cooperative attitude synchronization of multiple spacecraft with a dynamic virtual leader. Each spacecraft is modeled as a rigid body incorporating with model uncertainty and unknown external disturbance. The virtual leader gives commands to some of the follower spacecraft, and the communication network between followers can be an undirected or a directed graph. By using two neighborhood synchronization error signals, a finite-time control algorithm is designed associated with adaptive mechanism such that all follower spacecraft synchronize to the virtual leader in finite time. Then, a novel estimator-based finite-time distributed cooperative control algorithm is developed by using the followers estimates of the virtual leader, and the convergence of the attitude and angular velocity errors can be guaranteed in finite time. Moreover, both of the control strategies are chattering-free for their continuous design. Simulation examples are illustrated to demonstrate the validity of the two algorithms.

Development of Brake System and Regenerative Braking Cooperative Control Algorithm for Automatic-Transmission-Based Hybrid Electric Vehicles

In this paper, a brake system for an automatic transmission(AT)-based hybrid electric vehicle (HEV) is developed, and a regenerative braking cooperative control algorithm is proposed, with consideration of the characteristics of the brake system. The brake system does not require a pedal simulator or a fail-safe device, because a hydraulic brake is equipped on the rear wheels, and an electronic wedge brake (EWB) is equipped on the front wheels of the vehicle. Dynamic models of the HEV equipped with the brake system developed in this study are obtained, and a performance simulator is developed. Furthermore, a regenerative braking cooperative control algorithm, which can increase the regenerative braking energy recovery, is suggested by considering the characteristics of the proposed hydraulic brake system. A simulation and a vehicle test show that the brake system and the regenerative braking cooperative control algorithm satisfy the demanded braking force by performing cooperative control between regenerative braking and friction braking. The regenerative braking cooperative control algorithm can increase energy recovery of the regenerative braking by increasing the gradient of the demanded braking force against the pedal stroke. The gradient of the demanded braking force needs to be determined with consideration of the driver's braking characteristics, regenerative braking energy, and the driving comfort.

Cooperative Underwater Manipulation Systems: Control Developments within the MARIS project

A novel co-operative control algorithm has been presented in this paper for the transportation of large objects in underwater scenarios using two free floating vehicles, each one endowed with a 7 d.o.f redundant manipulator. The paper also gives detailed information about the theoretical foundations related to the kinematic and dynamic modelling, and then to the cooperative control, of the overall system. Due to the low bandwidth in underwater scenarios, the algorithm presented in the paper just exchanges six numbers (tool frame velocities) and still gives extremely good results even with such high limitations on the information exchange.

自端計測情報の相関関係を利用した複数台SVRの協調制御手法の検討

In this paper, a cooperative control algorithm for multiple step voltage regulator (SVR) using correlation of measurement data of distribution line is proposed. Conventionally, the control time constant of a SVR placed on the feeder end side was set slower than a SVR placed on the substation side. The unnecessary tap movement of SVR was reduced by this setting. In this case, on the condition that “the photovoltaic power generation output of the feeder end fluctuates” and “only SVR of the end side works”, it is a problem that control of SVR becomes slow. By the proposed method, the SVR settled in end side of a feeder can change its tap rapidly only if the SVR settled in sending side of a feeder will not change its tap by using proposed method. The features of the method are followings: (1) to estimate tap change possibility of the sending side SVR using correlation model of both of the SVR, (2) only use local measurement data of the SVRs for tap change control. By the proposed method, unnecessary tap change operation and lag of tap control are reduced without communication networks.

Coverage Capacity Optimization for Mobile Sensor Networks Based on Evolutionary Games

The optimal and distributed provisioning of high coverage capacity in mobile sensor networks is known as a fundamental but hard problem. The situation is exacerbated in a mobile wireless setting due to the dynamic coverage of a mobile sensor network resulting from continuous movement of sensors. In this paper, we propose an optimization framework for maximizing the coverage capacity in mobile sensor networks that comprise both stationary sensors (SSs) and mobile sensors (MSs). Both the intracoverage capacity and the intercoverage capacity are jointly optimized by considering the control of the power and distance between MSs and SSs and the interference among MSs. We propose a new noncooperative control algorithm that iteratively solves intracoverage capacity optimization between MSs and SSs. We also further formulate intercoverage capacity as evolutionary coalition game and present a new cooperative interference control algorithm that iteratively solves intercoverage capacity optimization among MSs. We prove the existence of a solution for iteration control equation of the power and distance and the interference to maximize the coverage capacity. Finally, we assess the performance of the proposed algorithm and show that proposed control scheme can effectively improve the average coveragecapacity in mobile sensor networks.

Distributed attitude control for multiple spacecraft with communication delays

The work presented here considers the attitude synchronization problem for a group of spacecraft in the presence of communication delays. Based on the backstepping control and finite-time control techniques, a novel nonsmooth distributed cooperative attitude control algorithm is proposed for multiple spacecraft with attitude described by quaternion. Rigorous proof shows that attitude synchronization can be achieved asymptotically under the proposed control law if the communication topology graph among the spacecraft is strongly connected. Finally, a simulation example is given to demonstrate the efficiency of the proposed method.

An improved cooperative adaptive cruise control (CACC) algorithm considering invalid communication

For the Cooperative Adaptive Cruise Control (CACC) Algorithm, existing research studies mainly focus on how inter-vehicle communication can be used to develop CACC controller, the influence of the communication delays and lags of the actuators to the string stability. However, whether the string stability can be guaranteed when inter-vehicle communication is invalid partially has hardly been considered. This paper presents an improved CACC algorithm based on the sliding mode control theory and analyses the range of CACC controller parameters to maintain string stability. A dynamic model of vehicle spacing deviation in a platoon is then established, and the string stability conditions under improved CACC are analyzed. Unlike the traditional CACC algorithms, the proposed algorithm can ensure the functionality of the CACC system even if inter-vehicle communication is partially invalid. Finally, this paper establishes a platoon of five vehicles to simulate the improved CACC algorithm in MATLAB/Simulink, and the simulation results demonstrate that the improved CACC algorithm can maintain the string stability of a CACC platoon through adjusting the controller parameters and enlarging the spacing to prevent accidents. With guaranteed string stability, the proposed CACC algorithm can prevent oscillation of vehicle spacing and reduce chain collision accidents under real-world circumstances. This research proposes an improved CACC algorithm, which can guarantee the string stability when inter-vehicle communication is invalid.

Co-operative control for regenerative braking and friction braking to increase energy recovery without wheel lock

This paper presents a regenerative braking co-operative control algorithm to increase energy recovery without wheel lock. Considering the magnitude of the braking force available between the tire and road surface, the control algorithm was designed for the regenerative braking force at the front wheel and friction braking force at the rear wheel to be increased following the friction coefficient line. The performance of the proposed regenerative braking co-operative control algorithm was evaluated by the hardware in the loop simulation (HILS) with an electronic wedge brake on its front wheels and an electronic mechanical brake on its rear wheels. The HILS results showed that a proper braking force on the front and rear wheels on a low μ road prevented the lock of the front wheels that was connected to the motor, and maintained the regenerative braking and increased energy recovery.

Hardware-in-the-loop simulation of pressure-difference-limiting modulation of the hydraulic brake for regenerative braking control of electric vehicles

Because of its significant impact on the cooperative regenerative braking performance of electrified vehicles, the modulation effect of a hydraulic brake is of great importance. To improve the hydraulic brake control performance further, a novel pressure-difference-limiting control method for hydraulic pressure modulation based on on–off solenoid valves is proposed. The linear relationship between the coil current and the pressure difference across the valve is obtained. The characteristics of pressure-difference-limiting modulation are simulated and analysed. Then, a cooperative regenerative braking control algorithm based on the pressure-difference-limiting modulation of the hydraulic brake is designed. Hardware-in-the-loop tests of the algorithm under typical braking procedures are carried out. The test results demonstrate the validity and feasibility of the developed regenerative braking control algorithm and indicate that the proposed pressure-difference-limiting modulation method, which has an advantage over the conventional control based on a pulse-width-modulated signal with respect to the control accuracy of the hydraulic brake pressure, has great potential to improve the braking performance of a vehicle.

Finite-Time Cooperative Tracking Control Algorithm for Multiple Surface Vessels

We investigate the problem of finite-time cooperative tracking for multiple surface vessels in the presence of external disturbances. A robust finite-time cooperative tracking algorithm based on terminal sliding-mode control is proposed for multiple surface vessels. In light of the leader-follower strategy, a virtual leader vessel is defined to provide reference point for other surface vessels to form the desired formation. Specifically, the proposed algorithm only requires the communication topology among the surface vessels to be a directed graph with a directed spanning tree. The robustness is achieved by compensating the upper bound of external disturbance in the control input, and the global finite-time stability is proved by Lyapunov stability theory. Finally, the effectiveness of the proposed finite-time cooperative tracking control algorithm is demonstrated by simulation results.