Differential-drive Mobile Robots Research Articles

Fuzzy Logic Controller for Bidirectional Garaging of a Differential Drive Mobile Robot

This paper presents a procedure for the design of a fuzzy logic controller for the garaging of a wheeled mobile robot, with non-holonomic constraints and discrete control signal levels. The design procedure is based on the virtual fuzzy magnet principle, which implies the definition of fictive points in the garage surroundings, and which, in an appropriate manner, by robot attraction, provides an efficient garaging process. The proposed fuzzy logic controller has four input variables: two represent the robot's distancing from fictitious fuzzy magnets and two are angles that define the orientation of the vehicle. The output variables are related to voltages sent to motors in charge of propelling the left and right wheel of the robot. The efficiency and shortfalls of the proposed algorithm are analyzed by means of both detailed simulations and multiple re-runs of a real experiment. Special attention is devoted to the analysis of different initial robot configurations and the effect of an error in the estimation of the current position of the robot on garaging efficiency.

Fuzzy-Based Controller for Differential Drive Mobile Robot Obstacle Avoidance

This paper presents a new methodology for the avoidance of one or more obstacles, and for the navigation of a differential-drive mobile robot. The approach is based on fuzzy logic with virtual fuzzy magnets, and represents a reactive controller for navigation through an unknown environment to the ultimate target. Relative parameters of the obstacle in the robot's way are determined at the preprocessing stage and the algorithm is therefore applicable to obstacles of different sizes. The algorithm, designed to avoid a single stationary obstacle, was generalized and successfully applied in a multiple-obstacle navigation scenario. The efficiency of the algorithm is illustrated by computer simulations using the kinematic model of a mobile robot.

Flocking for multi-robot systems via the Null-Space-based Behavioral control

Flocking is the way in which populations of animals like birds, fishes, and insects move together. In such cases, the global behavior of the team emerges as a consequence of local interactions among the neighboring members. This paper approaches the problem of letting a group of robots flock by resorting to a behavior-based control architecture, namely Null-Space-based Behavioral (NSB) control. Following such a control architecture, very simple behaviors for each robot are defined and properly arranged in priority in order to achieve the assigned mission. In particular, flocking is performed in a decentralized manner, that is, the behaviors of each robot only depend on local information concerning the robot’s neighbors. In this paper, the flocking behavior is analyzed in a variety of conditions: with or without a moving rendez-vous point, in a two- or three-dimensional space and in presence of obstacles. Extensive simulations and experiments performed with a team of differential-drive mobile robots show the effectiveness of the proposed algorithm.

RF/초음파센서와 이동특성에 기반한 고속 이동로봇의 위치추정기법

A new localization algorithm is proposed for a fast moving mobile robot, which utilizes only one beacon and the global features of the differential-driving mobile robot. It takes a relatively long time to localize a mobile robot with active beacon sensors since the distance to the beacon is measured by the traveling time of the ultrasonic signal. When the mobile robot is moving slowly the measurement time does not yield a high error. At a higher mobile robot speed, however, the localization error becomes too large to locate the mobile robot. Therefore, in high-speed mobile robot operations, instead of using two or more active beacons for localization, only one active beacon and the global features of the mobile robot are used to localize the mobile robot in this research. The two global features are the radius and center of the rotational motion for the differential-driving mobile robot which generally describe motion of the mobile robot and are used for the trace prediction of the mobile robot. In high speed operations the localizer finds an intersection point of this predicted trace and a circle which is centered at the beacon and has the radius of the distance between the mobile robot and the beacon. This new approach resolves the large localization error caused by the high speed of the mobile robot. The performance of the new localization algorithm has been verified through the experiments with a high-speed mobile robot.

Minimum Wheel-Rotation Paths for Differential-Drive Mobile Robots

The shortest paths for a mobile robot are a fundamental property of the mechanism, and may also be used as a family of primitives for motion planning in the presence of obstacles. This paper characterizes shortest paths for differential-drive mobile robots, with the goal of classifying solutions in the spirit of Dubins curves and Reeds—Shepp curves for car-like robots. To obtain a well-defined notion of shortest, the total amount of wheel-rotation is optimized. Using the Pontryagin Maximum Principle and other tools, we derive the set of optimal paths, and we give a representation of the extremals in the form of finite automata. It turns out that minimum time for the Reeds—Shepp car is equal to minimum wheel-rotation for the differential-drive, and minimum time curves for the convexified Reeds—Shepp car are exactly the same as minimum wheel-rotation paths for the differential-drive. It is currently unknown whether there is a simpler proof for this fact.

Design of Augmented Extended and Unscented Kalman Filters for Differential-Drive Mobile Robots

Design of Augmented Extended and Unscented Kalman Filters for Differential-Drive Mobile Robots

An Efficient Localization Scheme for a Differential-Driving Mobile Robot Based on RFID System

This paper presents an efficient localization scheme for an indoors mobile robot using Radio-Frequency IDentification (RFID) systems. The mobile robot carries an RFID reader at the bottom of the chassis, which reads the RFID tags on the floor to localize the mobile robot. Each of the RFID tags stores its own absolute position, which is used to calculate the position, orientation, and velocity of the mobile robot. However, a localization system based on RFID technology inevitably suffers from an estimation error. In this paper, a new triangular pattern of arranging the RFID tags on the floor has been proposed to reduce the estimation error of the conventional square pattern. In addition, the motion-continuity property of the differential-driving mobile robot has been utilized to improve the localization accuracy of the mobile robot. According to the conventional approach, two readers are necessary to identify the orientation of the mobile robot. Therefore, this new approach, based on the motion-continuity property of the differential-driving mobile robot, provides a cheap and fast estimation of the orientation. The proposed algorithms used to raise the accuracy of the robot localization are successfully verified through experiments.

Linear estimation of the physical odometric parameters for differential-drive mobile robots

In this paper a calibration technique aimed at identifying the odometric parameters of differential-drive mobile robots is proposed. The algorithm is based on two successive least-squares estimations based on the continuous-time kinematic equations of motion; the time-discretization error, thus, is avoided. The use of the least-squares technique is made possible by working on a linear mapping between the unknowns and the measurements and is not the result of a linearization. Another advantage of the proposed technique is that no specific path is required. The basic technique makes use of video-camera measurements and absolute position readings of the wheels' encoders; the use of different sensors and measurements of the wheels velocities is also discussed. Experimental results with a mobile robot Khepera II confirm the effectiveness of the proposed technique.

REAL-TIME CONTROL OF A MOBILE ROBOT USING LINEARIZED MODEL PREDICTIVE CONTROL

This paper proposes an optimal control strategy for a differential-drive mobile robot. It is well known that such a system can not be feedback stabilized by a smooth time-invariant control law. By using model predictive control (MPC), an appropriate control law is implicitly obtained. Furthermore, the system physical constraints on state and inputs are dealt with in a straightforward way. The optimization problem is solved by quadratic programming (QP) and experimental results show that the control law computation can be performed under the system real-time requirements.

A calibration method for odometry of mobile robots based on the least-squares technique: theory and experimental validation

For a mobile robot, odometry calibration consists of the identification of a set of kinematic parameters that allow reconstructing the vehicle's absolute position and orientation starting from the wheels' encoder measurements. This paper develops a systematic method for odometry calibration of differential-drive mobile robots. As a first step, the kinematic equations are written so as to underline linearity in a suitable set of unknown parameters; thus, the least-squares method can be applied to estimate them. A major advantage of the adopted formulation is that it provides a quantitative measure of the optimality of a test motion; this can be exploited to drive guidelines on the choice of the test trajectories and to evaluate accuracy of a solution. The proposed technique has been experimentally validated on two different mobile robots and, in one case, compared with other existing approaches; the obtained results confirm the effectiveness of the proposed calibration method.

차동 구륜이동로봇의 기구학적 보정과 모터제어기의 가속도 해상도 제약을 고려한 기준속도궤적의 설계

차동 구륜이동로봇의 기구학적 보정과 모터제어기의 가속도 해상도 제약을 고려한 기준속도궤적의 설계

A KINEMATIC AND DYNAMIC MODEL-BASED MOTION CONTROLLER FOR MOBILE ROBOTS

The paper presents a model for motion generation of differential-drive mobile robots. The parameters of the dynamic model allow adjusting the robot translational and rotational behaviours separately. The model takes into account the robot kinematic and dynamic constraints, making the velocities and accelerations bounded and compatible with those the robot can perform. The main contribution of the paper is to use the model itself as a motion controller: under soft hypothesis on the velocities and accelerations, this approach allows an easy tuning of the controller parameters. A system stability and parameters sensitivity analysis is developed, in order to get guidelines for controller tuning. The clear physical sense of the parameters make this tuning easy and intuitive. Experimental results involving a real mobile robot show the performance of this approach.

Measurement and correction of systematic odometry errors in mobile robots

Odometry is the most widely used method for determining the momentary position of a mobile robot. This paper introduces practical methods for measuring and reducing odometry errors that are caused by the two dominant error sources in differential-drive mobile robots: 1) uncertainty about the effective wheelbase; and 2) unequal wheel diameters. These errors stay almost constant over prolonged periods of time. Performing an occasional calibration as proposed here will increase the odometric accuracy of the robot and reduce operation cost because an accurate mobile robot requires fewer absolute positioning updates. Many manufacturers or end-users calibrate their robots, usually in a time-consuming and nonsystematic trial and error approach. By contrast, the method described in this paper is systematic, provides near-optimal results, and it can be performed easily and without complicated equipment. Experimental results are presented that show a consistent improvement of at least one order of magnitude in odometric accuracy (with respect to systematic errors) for a mobile robot calibrated with our method.

Cross-coupling motion controller for mobile robots

The design and implementation of a cross-coupling motion controller for a differential-drive mobile robot is described. A new concept, the most significant error, is introduced as the control design objective. Cross-coupling control directly minimizes the most significant error by coordinating the motion of the two drive wheels. The cross-coupling controller has excellent disturbance rejection. This is advantageous when the robot is not loaded symmetrically or has large friction in its drive mechanism, and especially when it is instructed to follow curved paths. Experimental results show that cross-coupling control yields substantially smaller position and orientation errors than conventional methods. >