Omnidirectional Wheeled Mobile Robot Research Articles

Simultaneous tracking and stabilization of an omnidirectional mobile robot in polar coordinates: a unified control approach

SUMMARYThis paper presents a polar-space kinematics control method to achieve simultaneous tracking and stabilization for an omnidirectional wheeled mobile robot with three independent driving omnidirectional wheels equally spaced at 120° from one another. The kinematic model of the robot in polar coordinates is presented. With the kinematic model, a kinematic control method based on feedback linearization is proposed in order to achieve simultaneous tracking and stabilization. The proposed method is easily extended to address the path following problem. Computer simulations and experimental results are presented to show the effectiveness and usefulness of the proposed control method at slow speeds.

Adaptive Trajectory Tracking and Stabilization for Omnidirectional Mobile Robot with Dynamic Effect and Uncertainties

Abstract This paper presents an adaptive backstepping control method for trajectory tracking and stabilization of an omnidirectional wheeled mobile robot with parameter variations and uncertainties caused by friction and slip. The dynamic model of the robot with three independent driving omnidirectional wheels equally spaced at 120 degrees from one another is briefly introduced. With the dynamic model, the adaptive controller to achieve both trajectory tracking and stabilization is synthesized via adaptive backstepping approach. Experimental results are conducted to show the merit of the proposed control method.

Smooth control of a wheeled omnidirectional robot

The paper investigates and proposes a solution for the smooth control of a wheeled omnidirectional mobile robot. The flexibility of this holonomous robot is fully exploited by means of the control strategy proposed. It is based on two main concepts: a Cartesian path planning and a wheel command generation based on the dynamic inversion of the robot kinematic model. The planned path has to exhibit appropriate geometric characteristics in order to generate wheel command signals with continuous accelerations. In particular, the second order geometric continuity of the path, i.e. the continuity of the curvature, has to be guaranteed. Simulation results concerning a perturbed system are reported

Dynamic model with slip for wheeled omnidirectional robots

A dynamic model is presented for omnidirectional wheeled mobile robots, including wheel/motion surface slip. We derive the dynamics model, experimentally measure friction coefficients, and measure the force to cause slip (to validate our friction model). Dynamic simulation examples are presented to demonstrate omnidirectional motion with slip. After developing an improved friction model, compared to our initial model, the simulation results agree well with experimentally-measured trajectory data with slip. Initially, we thought that only high robot velocity and acceleration governed the resulting slipping motion. However, we learned that the rigid material existing in the discontinuities between omnidirectional wheel rollers plays an equally important role in determining omnidirectional mobile robot dynamic slip motion, even at low rates and accelerations.

Development of a Fault-Tolerant Omnidirectional Wheeled Mobile Robot Using Nonholonomic Constraints

Robots used in hazardous environments need a high degree of mobility with good precision and robustness to actuator failures. In this paper, a novel gear train is proposed to satisfy the requirement for such a mechanism. The gear train is developed based on the following principles: (i) the mechanism is omnidirectional for a high degree of mobility, (ii) the mechanism uses only conventional tirewheels for high precision, and (iii) the mechanism uses only three motors for no actuation redundancy; at the same time, it has robustness to actuator failure so that when any one of the motors is not functioning properly, regardless of which one is not and regardless of the configuration at the moment of failure, the posture is controllable with the other two working actuators. By virtue of the proposed gear train, in an actuator failure, the entire structure becomes similar to a differentially driven two-wheeled mobile robot subject to nonholonomic constraints. The nonholonomic constraints, inherent in the mechanism and stemming from an actuator failure, are crucial to maintain the controllability of the robot posture when omnidirectional mobility is lost due to actuator failure. Controllability is proved and control laws are presented for both the omnidirectional mode, when all three motors are functioning, and the non-omnidirectional mode, when one of the motors is locked due to a failure. The omnidirectional mobility and robustness to an actuator failure is verified by experimental results.

Development of a Fault-Tolerant Omnidirectional Wheeled Mobile Robot Using Nonholonomic Constraints

Robots used in hazardous environments need a high degree of mobility with good precision and robustness to actuator failures. In this paper, a novel gear train is proposed to satisfy the requirement for such a mechanism. The gear train is developed based on the following principles: (i) the mechanism is omnidirectional for a high degree of mobility, (ii) the mechanism uses only conventional tirewheels for high precision, and (iii) the mechanism uses only three motors for no actuation redundancy; at the same time, it has robustness to actuator failure so that when any one of the motors is not functioning properly, regardless of which one is not and regardless of the configuration at the moment of failure, the posture is controllable with the other two working actuators. By virtue of the proposed gear train, in an actuator failure, the entire structure becomes similar to a differentially driven two-wheeled mobile robot subject to nonholonomic constraints. The nonholonomic constraints, inherent in the mechanism and stemming from an actuator failure, are crucial to maintain the controllability of the robot posture when omnidirectional mobility is lost due to actuator failure. Controllability is proved and control laws are presented for both the omnidirectional mode, when all three motors are functioning, and the non-omnidirectional mode, when one of the motors is locked due to a failure. The omnidirectional mobility and robustness to an actuator failure is verified by experimental results.