Differential-drive Wheeled Mobile Robots Research Articles

Tracking-Error Fuzzy-Based Control for Nonholonomic Wheeled Robots

In this paper, the trajectory to be tracked by a differentially driven wheeled mobile robot (DDWMR) is controlled. The considered DDWMR has a chassis with two active wheels and a front idle wheel. After introducing the kinematic model of the robot, the robot trajectory tracking problem using fuzzy and optimal fuzzy logic methods will be analyzed. Also, the same mission will be conducted using model predictive control (MPC) method. Minimizing the path tracking error is the objective of the controllers design. Moreover, the velocity and acceleration constraints are included in the proposed controllers design procedure to prevent the DDWMR from slipping and path curvature deviation. Finally, tracking error results for fuzzy, optimal fuzzy and model predictive controllers are compared. The tracking error analysis of the obtained simulation results, in MATLAB software, reveals the better performance of the designed fuzzy controller (FC) over the MPC, and the better performance of the designed optimal fuzzy controller over the FC.

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.

Decentralized multi-robot encirclement of a 3D target with guaranteed collision avoidance

We present a control framework for achieving encirclement of a target moving in 3D using a multi-robot system. Three variations of a basic control strategy are proposed for different versions of the encirclement problem, and their effectiveness is formally established. An extension ensuring maintenance of a safe inter-robot distance is also discussed. The proposed framework is fully decentralized and only requires local communication among robots; in particular, each robot locally estimates all the relevant global quantities. We validate the proposed strategy through simulations on kinematic point robots and quadrotor UAVs, as well as experiments on differential-drive wheeled mobile robots.

Sensor-Based Motion Planning of Wheeled Mobile Robots in Unknown Dynamic Environments

This paper presents a new sensor-based online method for generating collision-free paths for differential-drive wheeled mobile robots pursuing a moving target amidst dynamic and static obstacles. At each iteration, the set of all collision-free directions are calculated using velocity vectors of the robot relative to each obstacle, forming the Directive Circle (DC), which is the fundamental concept of our proposed method. Then, the best feasible direction close to the optimal direction to the target is selected from the DC, which prevents the robot from being trapped in local minima. Local movements of the robot are governed by the exponential stabilizing control scheme that provides a smooth motion at each step, while considering the robot's kinematic constraints. The robot is able to catch the target at a desired orientation. Extensive simulations demonstrated the efficiency of the proposed method and its success in coping with complex and highly dynamic environments with arbitrary obstacle shapes.

Tracking Control of Differential-Drive Wheeled Mobile Robots Using a Backstepping-Like Feedback Linearization

This paper proposes a tracking control method for differential-drive wheeled mobile robots with nonholonomic constraints by using a backstepping-like feedback linearization. Unlike previous backstepping controllers for wheeled mobile robots, a backstepping-like feedback control structure is proposed in the form of a cascaded kinematic and dynamic linearization to have a simpler and modular control structure. First, the pseudo commands for the forward linear velocity and the heading direction angle are designed based on kinematics. Then, the actual torque control inputs are designed to make the actual forward linear velocity and heading direction angle follow their corresponding pseudo commands. A stability analysis shows that the tracking errors of the posture (the position and heading direction angle) are globally ultimately bounded and its ultimate bound can be adjusted by the proper choice of control parameters. In addition, numerical simulations for various reference trajectories (e.g., a straight line, a circle, a sinusoidal curve, a spinning trajectory with no forward velocity and a nonzero rotational velocity, a cross-shaped trajectory changing the forward and backward directions, etc.) show the validity of the proposed scheme.

A kinematically compatible framework for cooperative payload transport by nonholonomic mobile manipulators

In this paper, we examine the development of a kinematically compatible control framework for a modular system of wheeled mobile manipulators that can team up to cooperatively transport a common payload. Each individually autonomous mobile manipulator consists of a differentially-driven Wheeled Mobile Robot (WMR) with a mounted two degree-of-freedom (d.o.f) revolute-jointed, planar and passive manipulator arm. The composite wheeled vehicle, formed by placing a payload at the end-effectors of two (or more) such mobile manipulators, has the capability to accommodate, detect and correct both instantaneous and finite relative configuration errors. The kinematically-compatible motion-planning/control framework developed here is intended to facilitate maintenance of all kinematic (holonomic and nonholonomic) constraints within such systems. Given an arbitrary end-effector trajectory, each individual mobile-manipulator's bi-level hierarchical controller first generates a kinematically-feasible desired trajectory for the WMR base, which is then tracked by a suitable lower-level posture stabilizing controller. Two variants of system-level cooperative control schemes--leader-follower and decentralized control--are then created based on the individual mobile-manipulator control scheme. Both methods are evaluated within an implementation framework that emphasizes both virtual prototyping (VP) and hardware-in-the-loop (HIL) experimentation. Simulation and experimental results of an example of a two-module system are used to highlight the capabilities of a real-time local sensor-based controller for accommodation, detection and corection of relative formation errors.

Impact of fixture design on sheet metal assembly variation

Differential drive wheeled mobile robots (DDWMRs) have been widely used in various applications due to their maneuverability and energy-saving characteristics. Tracking control of such mechanical systems with nonholonomic constraints in the presence of uncertainties and disturbances has attracted much attention. In this paper, a robust control scheme is developed for trajectory tracking control of a DDWMR in the presence of parametric uncertainties and disturbances. To fulfill the controller design, an inner–outer loop control structure is adopted for the DDWMR. For the inner-loop controller, a fast nonsingular terminal sliding mode (FNTSM) control law is applied for robust disturbance rejection in a finite time. Based on the kinematic model of the DDWMR, the outer-loop controller is designed for accurate trajectory tracking control. Finally, experiments are carried out to validate that the proposed control scheme has more robust tracking accuracy and faster response than an existing robust method.

Theory of the stereoscope

Differential drive wheeled mobile robots (DDWMRs) have been widely used in various applications due to their maneuverability and energy-saving characteristics. Tracking control of such mechanical systems with nonholonomic constraints in the presence of uncertainties and disturbances has attracted much attention. In this paper, a robust control scheme is developed for trajectory tracking control of a DDWMR in the presence of parametric uncertainties and disturbances. To fulfill the controller design, an inner–outer loop control structure is adopted for the DDWMR. For the inner-loop controller, a fast nonsingular terminal sliding mode (FNTSM) control law is applied for robust disturbance rejection in a finite time. Based on the kinematic model of the DDWMR, the outer-loop controller is designed for accurate trajectory tracking control. Finally, experiments are carried out to validate that the proposed control scheme has more robust tracking accuracy and faster response than an existing robust method.