Control Of Wheeled Mobile Robot Research Articles

Tracking control of WMRs on loose soil based on mixed H2/H∞ control with longitudinal slip ratio estimation

Wheeled mobile robots (WMRs) often suffer from the longitudinal slipping when moving on the loose soil of the surface of the moon during exploration. Longitudinal slip is the main cause of WMRs' delay in trajectory tracking. In this paper, a nonlinear extended state observer (NESO) is introduced to estimate the longitudinal velocity in order to estimate the slip ratio and the derivative of the loss of velocity which are used in modelled disturbance compensation. Owing to the uncertainty and disturbance caused by estimation errors, a multi-objective controller using the mixed H2/H∞ method is employed to ensure the robust stability and performance of the WMR system. The final inputs of the trajectory tracking consist of the feedforward compensation, compensation for the modelled disturbances and designed multi-objective control inputs. Finally, the simulation results demonstrate the effectiveness of the controller, which exhibits a satisfactory tracking performance.

Output-feedback formation control of wheeled mobile robots with actuators saturation compensation

This paper addresses output-feedback formation control of a group of wheeled mobile robots with saturating actuators. A virtual leader–follower strategy and a passivity-based design procedure are utilized to propose an adaptive neural network formation controller together with a nonlinear observer for the performance improvement of robots formation. The main tactic for the enhancement of the formation controller performance is the effective compensation of the actuators saturation nonlinearity by using neural networks and saturation functions. The need for velocity measurements is eliminated by a saturated observer that reduces unwanted peaks in the velocity estimates. A stability analysis is presented by using Lyapunov’s direct method. Finally, simulation results illustrate the efficiency of the proposed controller compared with existing results.

The Modeling of Motion Control for Wheeled Mobile Robot Based on PSO-MLS Method

The present paper describes a PSO-MLS modeling method for the motion control of wheeled mobile robot. The proposed method is based on Particle Swarm Optimization (PSO) in combination with Moving Least Squares (MLS). The PSO method is used for parameter setting in MLS method, which significantly influences the fitting accuracy. However, its use in the motion control of wheeled mobile robot has not been yet widely explored. So in this paper, the PSO-MLS method is used for the modeling of motion control of wheeled mobile robot, which is based on the local approximation method. Main advantages of this method are the PSO method used in the optimization of parameter setting and the local approximation used in MLS method. Application in the motion control of wheeled mobile robot based on PSO-MLS method is performed in this paper, and the performance of it is verified by the comparison with conventional least squares (LS) method in data fitting. Finally, the main conclusions of this study are exposed.

Disturbance Attenuation Tracking Control for Wheeled Mobile Robots With Skidding and Slipping

In this paper, a robust tracking control scheme is proposed for wheeled mobile robots with skidding, slipping, and input disturbance. Considering the existing skidding and slipping, a desired disturbance-observer-based virtual velocity control law is first designed. Then, the robust tracking control scheme is developed by considering the prescribed tracking performance requirement and using the disturbance observer. In the tracking control scheme design, the prescribed performance function method is employed to guarantee the desired tracking performance. To handle the skidding, slipping, and input disturbance, the disturbance observer is developed in the control scheme design. Experiment results demonstrate the effectiveness of the proposed tracking control scheme for wheeled mobile robots with skidding, slipping, and input disturbance.

The Coordinated Control of Wheeled Mobile Robot on Loose Soil

Generating the coordinated tractive force of each wheel for the robot is an important control objective in order to ensure the wheels to be the driven wheel but not the towed wheel. The tractive force is different between the front wheel and the following rear wheel because of the wheel’s unequal sinkage caused by the compaction of loose soil. In this study, the mathematical model of sinkage is established to investigate the influence of repetitive passing on wheel sinkage, and the wheels’ tractive performance is deduced on basis of the terramechanics. The equal drawbar pull generated by all the wheels under the optimal efficiency analysis is defined as the index to evaluate the wheel’s motion consistency, as well as the coordinated control objective of wheeled mobile robot on loose soil. Furthermore, dynamic model of a six-wheel mobile robot is established and the fuzzy sliding mode controller is designed. Meanwhile, the validity of the proposed modeling and control method is demonstrated through the ADAMS co-simulation model. The result shows that control system has good performance in simulation.

Distributed tracking control of uncertain mechanical systems with velocity constraints

SummaryThis paper considers the leader‐following control problem of multiple mechanical systems with uncertainty and velocity constraints. So as to deal with the velocity constraints, a reduction procedure is applied to transform the model of each system to a cascaded system. With the aid of the cascade structure of each system and the properties of linear time‐varying systems, distributed robust feedback controllers are proposed such that the state of each follower system asymptotically converges to the state of a leader system with the aid of neighbors' information. So as to reduce the cost of the communication between systems, an event‐triggered leader‐following control problem is also considered, and event‐triggered distributed controllers are proposed. As an application of the proposed results, formation control of wheeled mobile robots is considered, and distributed controllers are obtained with the aid of the results in Theorems 1 and 2. Simulation results show the effectiveness of the proposed results. Copyright © 2017 John Wiley & Sons, Ltd.

DOCUMENT DELIVERY ROBOT BASED ON IMAGE PROCESSING AND FUZZY CONTROL

The objective of this study is to integrate image processing, pattern recognition, RFID, and fuzzy theory into an omnidirectional wheeled mobile robot for receiving and delivering documents between rooms. In image pre-processing, the Hue-Saturation-Lightness color space is applied to avoid light interference, and then grayscale image threshold is used to obtain binary image. The median filter is utilized to filter the noises of speckle and salt-and-pepper, so color segmentation is then applied to capture desired color for tracking control. Pattern recognition is performed by the Adaptive Resonance Theory. RFID reader and room tag is used to verify the room number of the destination so that the recognition error from image processing can be avoided. Fuzzy theory is implemented into an omnidirectional wheeled mobile robot control design for driving the wheels of the robot. Experimental results show that the proposed control scheme can make the omnidirectional mobile robot move to destination, receive and deliver documents between offices.

Sequentially switched fuzzy-model-based control for wheeled mobile robot with visual odometry

• The T–S fuzzy-model-based control for wheeled mobile robot is proposed. • The visual odometry (VO) is used for robot localization. • The stabilization is guaranteed based on the Lyapunov stability criterion. • The practical constraints on the VO are enforced in the control design. This study focused on the Takagi–Sugeno (T–S) fuzzy-model-based control design for the differentially-driven wheeled mobile robot with visual odometry. The position and posture of the mobile robot are estimated by visual odometry. The polar kinematic model of the mobile robot is exactly converted to the T–S fuzzy model and then the fuzzy control design is synthesized to the fuzzy model. The sequentially switched fuzzy control design includes turning, forward motion as well as position and posture control modes. The stabilization is guaranteed based on the Lyapunov stability criterion. The practical constraints on the visual odometry are also satisfied in the control design. Finally, the experiment results demonstrate the effectiveness of the fuzzy-model-based control design for the mobile robot with visual odometry.

Two Time-Scale Tracking Control of Nonholonomic Wheeled Mobile Robots

In this paper, a practical control law is proposed for wheeled mobile robots in order to both improve the transient performance and repress the tracking errors. In particular, a two time-scale filtering technique, which can derive a fast variable to compensate for the disturbance, is applied during the carbot’s moving process. The nominal system is governed using a controller derived under the back-stepping framework. Such a design can effectively realize the system’s tracking objective and enhance robustness via properly configured parameters. In the meantime, a two time-scale filter is applied to the system function to estimate the disturbances, essentially improving the system’s precision. By virtue of this innovative technique, the final performance of the system is satisfactory in terms of both transient response and tracking error rejection. A previous sliding mode based control law is compared with the propounded one with respect to transient behavior and steady-state errors, and two types of disturbances, respectively the constant and sinusoid are simulated to verify the filter’s effectiveness. Since, from the results, there is significant improvement in both transient and steady-state performance, the proposed method is confirmed to be practical for tracking control of the wheeled mobile robots.

Adaptive Speed Control of Wheeled Mobile Robot on Uncertain Road Condition

[abstFig src='/00280005/10.jpg' width='300' text='Adaptive speed control for mobile robot' ] This study investigated the effectiveness of a simple adaptive control system used for controlling the dynamics of the driving system of a wheeled mobile robot. This paper describes the design method of a speed control system and the gain adjustment procedure considering a practical application of the simple adaptive control system. Experiments were conducted on two different road conditions, and the results indicated that the rectilinear performance of the wheeled mobile robot improved with the use of the simple adaptive control system. In the case of uncertain road conditions, the simple adaptive control system reduced the deterioration of the control performance effectively.

Robust Distance-Based Tracking Control of Wheeled Mobile Robots Using Vision Sensors in the Presence of Kinematic Disturbances

This paper proposes a robust distance-based tracking control method for two-wheeled differential drive mobile robots (WMRs) in the presence of kinematic disturbances, where only the visual image information between the WMR and the target is used to obtain distances, and the velocity sensors are not available. To achieve the tracking control of the WMR toward the target, a vision system is used so as to obtain the relative posture information between the WMR and the target. In particular, the WMR is assumed to move without velocity sensors, and the posture and velocity information for the WMR and that of the target is unavailable. The necessary information of the maximum velocities between the WMR and the target is thus estimated in an online manner. Correspondingly, a robust backstepping-like feedback linearization method is proposed to simultaneously compensate for the unknown velocities and kinematic disturbances. Experiments have been performed for the WMR with the vision system to verify that the proposed method can allow the WMR to track the target in the presence of kinematic disturbances, even without using the velocity sensors.

An adaptive unscented Kalman filter-based adaptive tracking control for wheeled mobile robots with control constrains in the presence of wheel slipping

A novel control approach is proposed for trajectory tracking of a wheeled mobile robot with unknown wheels’ slipping. The longitudinal and lateral slipping are considered and processed as three time-varying parameters. The adaptive unscented Kalman filter is then designed to estimate the slipping parameters online, an adaptive adjustment of the noise covariances in the estimation process is implemented using a technique of covariance matching in the adaptive unscented Kalman filter context. Considering the practical physical constrains, a stable tracking control law for this robot system is proposed by the backstepping method. Asymptotic stability is guaranteed by Lyapunov stability theory. Control gains are determined online by applying pole placement method. Simulation and real experiment results show the effectiveness and robustness of the proposed control method.

Design of Path Planning and Obstacle Avoidance for a Wheeled Mobile Robot

This paper proposed a path tracking method for wheeled mobile robot (WMR). This method includes path planning and controller design. In path planning, using B-spline instead of A* algorithm to create smooth and obstacle-avoidance path, so that the possibility of collision can be reduced statistically. In controller design, genetic algorithm (GA) and fuzzy logic control (FLC) are combined together for the velocity control for WMR, which is supposed to move in a certain environment. The suitable membership function of FLC according to the feature of environment, such as distance and angle of WMR, is based on the B-spline path, and the input and output of FLC can be adjusted by GA. Therefore, the WMR can move along the planned path steady, which means our method has good performance.

Switched Modeling and Task–Priority Motion Planning of Wheeled Mobile Robots Subject to Slipping

This study is devoted to the modelling and control of Wheeled Mobile Robots moving with longitudinal and lateral slips of all wheels. Due to wheel slippage we have to deal with systems with changing dynamics. Wheeled Mobile Robots can be thus modeled as switched systems with both autonomous switches (due to wheel slippage) and smooth controls (due to control algorithm). It is assumed that the slipping is counteracted by the slip reaction forces acting at contact points of the wheels with the ground. A model of these reaction forces, borrowed from the theory of automotive systems, has been adopted and included into the Lagrangian dynamic equations of the robot. A framework for designing motion planning schemes devoid of chattering effects for systems with changing dynamics is presented. A task---priority motion planning problem for wheeled mobile robots subject to slipping is addressed and solved by means of Jacobian motion planning algorithm based on the Endogenous Configuration Space Approach. Performance of the algorithm is presented in simulations of the Pioneer 2DX mobile platform. The robot dynamics equations are derived and 4 variants of motion are distinguished. The motion planning problem is composed of two sub-tasks: robot has to reach a desired point in the task space (proper motion planning) and the motion should minimize either the control energy expendinture or the wheel slippage. Performance of the motion planning algorithm is illustrated by a sort of the parking maneuver problem.

A Velocity-Based Dynamic Model and Its Properties for Differential Drive Mobile Robots

An important issue in the field of motion control of wheeled mobile robots is that the design of most controllers is based only on the robot's kinematics. However, when high-speed movements and/or heavy load transportation are required, it becomes essential to consider the robot dynamics as well. The control signals generated by most dynamic controllers reported in the literature are torques or voltages for the robot motors, while commercial robots usually accept velocity commands. In this context, we present a velocity-based dynamic model for differential drive mobile robots that also includes the dynamics of the robot actuators. Such model has linear and angular velocities as inputs and has been included in Peter Corke's Robotics Toolbox for MATLAB, therefore it can be easily integrated into simulation systems that have been built for the unicycle kinematics. We demonstrate that the proposed dynamic model has useful mathematical properties. We also present an application of such model on the design of an adaptive dynamic controller and the stability analysis of the complete system, while applying the proposed model properties. Finally, we show some simulation and experimental results and discuss the advantages and limitations of the proposed model.

Hybrid Intelligent Algorithm for Indoor Path Planning and Trajectory-Tracking Control of Wheeled Mobile Robot

This paper presents a hybrid intelligent algorithm for a wheeled mobile robot (WMR) to implement both trajectory-tracking and path-following navigation missions. The novel control scheme combining the kinematic with TSK fuzzy control is developed to track the desired position, linear, and angular velocities, even though the WMR suffers from system uncertainties and disturbances. The proposed TSK fuzzy controller deals with a general dynamic model and has a good ability of disturbance rejection. For the path-following issue, the improved D* lite algorithm determines an appropriate path between an initial position and a destination. The derived path is transformed into a tracking trajectory by a function of time. The asymptotic stability of the overall system is proven by Lyapunov theory. Finally, real-time experiments with the use of the proposed hybrid intelligent algorithm on an eight-shaped reference trajectory and long-distance movement demonstrate the feasibility of practical WMR maneuvers.

Kinematic Analysis and Motion Control of Wheeled Mobile Robots in Cylindrical Workspaces

Wheeled mobile robots (WMRs) are often used for maintenance of round pipes or ducts, which can typically be represented as a cylindrical workspace. Working in round pipes or ducts, kinematic models of WMRs are different from those applying on a plane and thus pose significant challenges in terms of kinematic analysis and motion control. To address these challenges, the kinematic properties of WMRs in a cylindrical workspace are analyzed in this paper. First, we discuss the kinematic properties of a single wheel in a cylindrical workspace. Then, we analyze the geometric constraints of WMRs in round pipes or ducts with analytical geometry. Based on these analyses, kinematic properties of WMRs in cylindrical workspaces are discussed with screw theory. A control law based on biaxial clinometer information is proposed, and it enables the robot to move horizontally in round pipes or ducts. Finally, the motion of a single wheel purely rolling in a cylindrical workspace is simulated. Experiments using a car-like mobile robot moving in round ducts are carried out to show the feasibility of the proposed algorithm.

State of the Art in Predictive Control of Wheeled Mobile Robots

State of the Art in Predictive Control of Wheeled Mobile Robots

Optimal control at energy performance index of the mobile robots following dynamically created trajectories

In practice, the problem of motion control of the wheeled mobile robots is often neglected. Wheeled mobile robots are strongly nonlinear systems and restricted by non-holonomic constraints. Motion control of such systems is not trivial task and usage of non-optimal control signals can lead to deterioration of the overall robot system's performance. In case of autonomous application of the mobile robots all parts of its control system should work perfectly. The paper presents the theory and application of the optimal control method at the energy performance index towards motion control of the two-wheeled mobile robot during the realisation of complex, dynamically created trajectories. With the use of the proposed control method the two-wheeled mobile robot can realise effectively the desired trajectory, which is generated ad-hoc by the navigation system of the robot. Thus the proposed method can be used for motion control of autonomous or semi-autonomous wheeled mobile robots. The presented results of both computer simulations and experiments indicate that the proposed method works effectively from the point of view of the motion control of two-wheeled mobile robot. Movement of the mobile robot appeared reliable and predictable during all the tests.

Velocity Tracking Control of Wheeled Mobile Robots by Iterative Learning Control

This paper presents an iterative learning control (ILC) strategy to resolve the trajectory tracking problem of wheeled mobile robots (WMRs) based on dynamic model. In the previous study of WMRs’ trajectory tracking, ILC was usually applied to the kinematical model of WMRs with the assumption that desired velocity can be tracked immediately. However, this assumption cannot be realized in the real world at all. The kinematic and dynamic models of WMRs are deduced in this chapter, and a novel combination of D-type ILC algorithm and dynamic model of WMR with random bounded disturbances are presented. To analyze the convergence of the algorithm, the method of contracting mapping, which shows that the designed controller can make the velocity tracking errors converge to zero completely when the iteration times tend to infinite, is adopted. Simulation results show the effectiveness of D-type ILC in the trajectory tracking problem of WMRs, demonstrating the effectiveness and robustness of the algorithm in the condition of random bounded disturbance. A comparative study conducted between D-type ILC and compound cosine function neural network (NN) controller also demonstrates the effectiveness of the ILC strategy.