Three-wheeled Omnidirectional Mobile Robot Research Articles

Fuzzy Behavior-based Control of Three Wheeled Omnidirectional Mobile Robot

In this paper, a fuzzy behavior-based approach for a three wheeled omnidirectional mobile robot (TWOMR) navigation has been proposed. The robot has to track either static or dynamic target while avoiding either static or dynamic obstacles along its path. A simple controller design is adopted, and to do so, two fuzzy behaviors “Track the Target” and “Avoid Obstacles and Wall Following” are considered based on reduced rule bases (six and five rules respectively). This strategy employs a system of five ultrasonic sensors which provide the necessary information about obstacles in the environment. Simulation platform was designed to demonstrate the effectiveness of the proposed approach.

Minimum-energy cornering trajectory planning with self-rotation for three-wheeled omni-directional mobile robots

A minimum-energy cornering trajectory planning with self-rotation algorithm is investigated for three-wheeled omni-directional mobile robots (TOMRs). First, an generalized minimum-energy point-to-point trajectory planning algorithm is studied, which is obtained using Pontryagin’s minimum principle, a practical cost function as the energy drawn from the batteries to motors, and the accurate TOMR dynamic model including actuator dynamics and the Coriolis force. By analyzing the co-state equation, the minimum-energy rotational velocity trajectory is presented in analytic form. Also a novel algorithm for the minimum-energy translational velocity trajectory is investigated. Second, the minimum-energy cornering trajectory planning algorithm with self-rotation is developed. Simulation results show that the minimum-energy cornering trajectory can save energy up to 15.20%compared with the conventional control using trapezoidal velocity profiles, and up to 3.96 % compared with the loss-minimization control using the armature loss as the cost function. Also a resolved-acceleration controller is implemented to show an actual performance.

Research on the intelligent control technology of the uneven road omni-directional mobile robot

For the omni-directional mobile robot on uneven pavement, its variants and mutations movement control have been puzzling the researchers. An adaptive extension intelligent control technology, which combines the high precision of the adaptive control technology, fast reaction rate of the extension control technology, is used to study the three wheeled omni-directional mobile robot on uneven pavement in this paper. Through the research, the three wheeled omni-directional mobile robot’s kinematics and dynamics model have been constructed firstly. Then a kind of adaptive extension intelligent control method has been built. At last the adaptive extension intelligent controller has been designed and the experimental results have been given accordingly. The experimental results show that the three wheeled omni-directional mobile robot which has the ability of high precision, fast reaction rate, self-organizing and self-learning using adaptive extension intelligent control technology is better than using adaptive control technology. This technology can meet the requirements of three wheeled omni-directional mobile robot.

Kinematic analysis and simulation of active-caster robotic drive with ball transmission (ACROBAT-S)

In this study, a new type of active-caster with a single ball transmission (ACROBAT-S) was proposed. The proposed ball transmission involved a novel mechanism that realized to control the active-caster for propelling robotic platforms. The combined power from two motors rotated a single ball in two dimensions. Additionally, the combined power was simultaneously decomposed to the wheel shaft and steering shaft of an active-caster in an appropriate ratio. The transmission design enabled an omnidirectional robot with three active-casters to control its 3D motion by three motors with no redundancy. The new concept of ACROBAT-S offers several advantages as compared to the previous ACROBAT design as the number of balls was reduced from two to one, and therefore the number of friction drives between a ball and rollers or a ball and another ball was also reduced from five to three. These features could contribute to simplifying the mechanism design and to reduce transmission slippages and energy losses. The design concept was verified by deriving and analyzing the kinematics of a single ball transmission mechanism and a three-wheeled omnidirectional mobile robot. Furthermore, the motions of ACROBAT-S and that of an omnidirectional robot were verified using computer simulations. The results confirmed that the proposed single ball transmission could be applied to an omnidirectional wheel mechanism to realize non-redundant omnidirectional motions.

Front and Back Movement Analysis of a Triangle-Structured Three-Wheeled Omnidirectional Mobile Robot by Varying the Angles between Two Selected Wheels.

Omnidirectional robots can move in all directions without steering their wheels and it can rotate clockwise and counterclockwise with reference to their axis. In this paper, we focused only on front and back movement, to analyse the square- and triangle-structured omnidirectional robot movements. An omnidirectional mobile robot shows different performances with the different number of wheels and the omnidirectional mobile robot's chassis design. Research is going on in this field to improve the accurate movement capability of omnidirectional mobile robots. This paper presents a design of a unique device of Angle Variable Chassis (AVC) for linear movement analysis of a three-wheeled omnidirectional mobile robot (TWOMR), at various angles (θ) between the wheels. Basic mobility algorithm is developed by varying the angles between the two selected omnidirectional wheels in TWOMR. The experiment is carried out by varying the angles (θ = 30°, 45°, 60°, 90°, and 120°) between the two selected omniwheels and analysing the movement of TWOMR in forward direction and reverse direction on a smooth cement surface. Respectively, it is compared to itself for various angles (θ), to get its advantages and weaknesses. The conclusion of the paper provides effective movement of TWOMR at a particular angle (θ) and also the application of TWOMR in different situations.

単球によるACROBAT全方向移動機構の提案と性能評価

In this paper, new type of an active-caster with a single ball transmission (ACROBAT-S) is proposed. The new concept of ACROBAT-S gives many advantages compared with the original ACROBAT since the number of ball is reduced, therefore the number of friction drive reduced from five to three. These features may contribute to simplify the mechanism design and to reduce transmission energy losses. To verify the design concept, we derive and analyze a kinematics of a single ball transmission mechanism and a three-wheeled omnidirectional mobile robot. Furthermore the motions of ACROBAT-S and that of an omnidirectional robot are verified by computer simulations. From the results, it is confirmed that the proposed single ball transmission is applicable for omnidirectional wheel mechanism to realize the non-redundant omnidirectional motions.

Finding the Quickest Straight-Line Trajectory for a Three-Wheeled Omnidirectional Robot under Input Voltage Constraints

We provide an analytical solution to the problem of generating the quickest straight-line trajectory for a three-wheeled omnidirectional mobile robot, under the practical constraint of limited voltage. Applying the maximum principle to the geometric properties of the input constraints, we find that an optimal input vector of motor voltages has at least one extreme value when the orientation of the robot is fixed and two extreme values when rotation is allowed. We can find an explicit representation of the optimal vector for a motion under fixed orientation. We derive several properties of quickest straight-line trajectories and verify them through simulation. We show that the quickest trajectory when rotation is allowed is always faster than the quickest with fixed orientation.

Stable Model-Based Predictive Control for Wheeled Mobile Robots using Linear Matrix Inequalities

This paper presents practical results from the application of a new synthesis methodology based on model predictive control (MPC) applied to a three-wheeled omnidirectional mobile robot seeking to follow pre-established trajectories. The approach is based on the definition of an objective function with a finite future time horizon. The resulting optimization problem is declared in the form of linear matrix inequalities (LMIs). The closed loop stability of the system is guaranteed through constraints related to the non-increasing monotonicity of the objective function. Constraints are also implemented in the manipulated variables with the objective of adapting the control system to the physical limitations of the robot. Additionally, methods are described to handle the computational delay in the robot model and to adjust the control law to improve the global performance of the system.

Online Minimum-Energy Trajectory Planning and Control on a Straight-Line Path for Three-Wheeled Omnidirectional Mobile Robots

To maximize total operating time, an online minimum-energy translational and rotational velocity trajectory planning and control system is presented on a straight-line path for three-wheeled omnidirectional mobile robots (TOMRs). We suggest an efficient online trajectory planning algorithm, which minimizes a practical cost function as the energy that is drawn from batteries to motors, which is based on an accurate TOMR dynamic model that includes both the Coriolis force and the actuator motor dynamics. Using Pontryagin's minimum principle, we find the minimum-energy rotational velocity trajectory in analytic form. Then, the minimum-energy translational velocity trajectory is found using a novel algorithm that has a time complexity of O(n), which is based on a linearity condition on the state transition of TOMRs. Moreover, a trajectory control system is implemented using the resolved-acceleration control to validate the actual performance. Simulation and experiment results show that these minimum-energy trajectories can save energy up to 4.76% compared with the energy-efficient trapezoidal velocity profile and up to 5.29% compared with the loss-minimization control.

Development of an Field-Programmable Gate Arrays-Based Three-Wheeled Omnidirectional Sensor Mobile Robot for the Teaching of Embedded Robotics

Development of an Field-Programmable Gate Arrays-Based Three-Wheeled Omnidirectional Sensor Mobile Robot for the Teaching of Embedded Robotics

Minimum-Energy Trajectory Generation for Cornering with a Fixed Heading for Three-Wheeled Omni-Directional Mobile Robots

The minimum-energy trajectory generation problem of cornering with a fixed heading is solved for three-wheeled omni-directional mobile robots (TOMRs). To maximize the total operation time of a mobile robot with carried batteries having finite energy, we have chosen a practical cost function to be the total energy drawn from the batteries. Then, we formulate the minimum-energy trajectory generation problem of executing a cornering motion with a fixed heading for TOMRs with given dynamics including actuator motors. The optimal control theory using a Hamiltonian function and a numerical method are used to obtain the minimum-energy trajectory, which gives the velocity profile in analytic form. Performance analyses are conducted with various simulations and the consumed energy using obtained minimum-energy trajectory is compared with a typical conventional trajectory with a trapezoidal velocity profile, which reveals that an energy savings of up to 18.7 % is achieved. To validate the actual performance of our trajectory, we implemented and tested an accurate trajectory following system which utilizes a resolved acceleration controller.

Calibration of omnidirectional wheeled mobile robots: method and experiments

SUMMARYOdometry errors, which occur during wheeled mobile robot movement, are inevitable as they originate from hard-to-avoid imperfections such as unequal wheels diameters, joints misalignment, backlash, slippage in encoder pulses, and much more. This paper extends the method, developed previously by the authors for calibration of differential mobile robots, to reduce positioning errors for the class of mobile robots having omnidirectional wheels. The method is built upon the easy to construct kinematic formulation of omnidirectional wheels, and is capable of compensating both systematic and non-systematic errors. The effectiveness of the method is experimentally investigated on a prototype three-wheeled omnidirectional mobile robot. The validations include tracking unseen trajectories, self-rotation, as well as travelling over surface irregularities. Results show that the method is very effective in improving position errors by at least 68%. Since the method is simple to implement and has no assumption on the sources of errors, it should be considered seriously as a tool for calibrating omnidirectional mobile having any number of wheels.

The study of path error for an omnidirectional home care mobile robot

The first objective of this research was to develop an omnidirectional home care mobile robot. A PC-based controller controls the mobile robot platform. This service mobile robot is equipped with an “indoor positioning system” and an obstacle avoidance system. The indoor positioning system is used for rapid and precise positioning and guidance of the mobile robot. The obstacle avoidance system can detect static and dynamic obstacles. In order to understand the stability of a three-wheeled omnidirectional mobile robot, we carried out some experiments to measure the rectangular and circular path errors of the proposed mobile robot in this research. From the experimental results, we found that the path error was smaller with the guidance of the localization system. The mobile robot can also return to its starting point. The localization system can successfully maintain the robot’s heading angle along a circular path.

Minimum-Time Trajectory for Three-Wheeled Omnidirectional Mobile Robots Following a Bounded-Curvature Path With a Referenced Heading Profile

The minimum-time trajectory planning problem for three-wheeled omnidirectional mobile robots (TOMRs) is solved based on the combined dynamic model of a mobile robot and dc motor actuators, under the constraint of bounded control inputs due to the battery voltage. We constrain that the bounded-curvature path based on a smooth road (which is described as a clothoid) be given for the translational motion of the TOMR and that the reference profile with respect to the path-length parameter be predetermined for the heading motion of the TOMR. The dynamics of the TOMR is transformed into normal and tangent spaces for motion analysis on the bounded-curvature path. We find out the time-optimality condition of the TOMR, which imposes that the input voltage vector of three motors should have at least one extreme component. Based on the optimality condition, we present a systematic way to construct the optimal control input vector. Finally, several examples are analyzed by the use of the proposed method.

A Nonlinear Programming Method for Time-Optimal Control of an Omni-Directional Mobile Robot

The time-optimal control problem of a three-wheeled omni-directional mobile robot is studied in this paper. In contrast to traditional methods, in which the Pontryagin's Minimum Principle is usually used, an iterative procedure is proposed to transform the time-optimal problem into a nonlinear programming (NLP) one. In the formulated NLP problem, the number of control steps is fixed initially and the sampling period is treated as a variable to be minimized in the optimization process. An upper limit on the sampling period is set in advance considering the accuracy of discretization. If the value of the sampling period is larger than the upper limit, then an update of the number of control steps is needed. To generate initial feasible solutions of the NLP problem, a genetic algorithm is adopted. Since different initial feasible solutions can be generated, the optimization process can be started from different points to find the optimal solution. In this manner, one can find a time-optimal movement of the omni-directional mobile robot between two configurations. To show the feasibility of the proposed method, simulation results are included for illustration.

The kinematics for redundantly actuated omnidirectional mobile robots

AbstractOmnidirectional mobile robots have been popularly employed in several application areas. However, the kinematics and singularity analysis for these systems have not been clearly identified, especially for the redundantly actuated case, which is common in current omnidirectional mobile robots. In light of this fact, this article introduces two different kinematic approaches for a typical omnidirectional mobile robot having three caster wheels, and examines singularity configurations of such systems. Then, a singularity‐free load‐distribution scheme for a redundantly actuated three‐wheeled omnidirectional mobile robot is proposed. Through simulation, several advantages of the redundantly actuated mobile robot (singularity avoidance, input‐load saving, and exploiting several subtasks) are presented. © 2002 Wiley Periodicals, Inc.

Kinematic Modeling of Omni-Directional Mobile Robots as Parallel Manipulator

Omni-directional mobile robots have been popularly employed in several applicationareas. However, the kinematics and singularity analysis for these systems has not been clearly identified. This paper introduces two different kinematic approaches for omni-directional mobile robots. Then, a singular-free load distribution scheme for redundantly actuated three-wheeled omni-directional mobile robot is proposed. Throughsimulation, several advantages of redundantly actuated mobile robot in aspect of singularity avoiance, input-load saving, and exploiting several subtasks are presented.