Motion Of Wheeled Mobile Robot Research Articles

Predictive Tracking Control for WMR Systems with Sensor and Control Delays

This paper addresses the control design problem for nonlinear Wheeled Mobile Robot (WMR) tracking with sensor and control delays. The tracking model is built by WMR dynamical equation. The state-space representations of the controlled WMR motion system and the dynamical target system are obtained by transformations. Then, the tracking error system with sensor and control delays is achieved and a nonlinear tracking control is presented. The physical implement problem of the predictive control is solved by constructing a high-gain predictor, based on which the predicted states in state feedback control are replaced by the predictive ones. The simulation results demonstrate that the physical implement problem are solved by designing a high-gain predictor. The target paths of a figure-of-8 and a circle are successfully tracked by the state feedback and output feedback controllers.

Predictive Feedback Linearization Tracking Control for WMR Systems with Control Delay

This article addresses the control design problem for nonlinear wheeled mobile robot (WMR) tracking with a control delay. The tracking model is built by WMR dynamical equation. The state-space representations of the controlled WMR motion system and the dynamical target system are obtained by transformations. Then, the tracking error system with control delay is achieved and a feedback linearization delayed control is presented. The physical implement problem of the predictive control is solved by constructing a high-gain predictor, based on which the predicted states in feedback linearization controllers are estimated by the predictive states. The simulation results demonstrate that the physical implement problem are solved well by using high-gain predictor. The target path are successfully tracked by the designed feedback linearization controllers of state feedback and output feedback.

Motion Control of Wheeled Mobile Robots

The paper deals with the modeling and control strategies of the motion of wheeled mobile robots. The model of the vehicle has two driving wheels and the angular velocities of the two wheels are independently controlled. First, the vehicle kinematics model and the control strategies using a feedforward compensator are analyzed. Second, fuzzy reactive control of a mobile robot motion in an unknown environment with obstacles are proposed. Finally, the mobile robot simulation is illustrated.

Bio-inspired Approach for Smooth Motion Control of Wheeled Mobile Robots

Wheeled mobile robot (WMR) has gained wide application in civilian and military fields. Smooth and stable motion of WMR is crucial not only for enhancing control accuracy and facilitating mission completion, but also for reducing mechanical tearing and wearing. In this paper, we present a novel bio-inspired approach aiming at significantly reducing motion chattering phenomena inherent with traditional methods. The main idea of the proposed smooth motion controller is motivated by two famous Chinese sayings “haste does not bring success” and “ride softly then you may get home sooner”, which inspires the utilization of pre-processing the speed commands with the help of fuzzy rules to generate more favorable movement for the actuation device, so as to effectively avoid the jitter problem that has not yet been adequately solved by traditional methods. Detail formulas and algorithms are derived with consideration of the kinematics and dynamics of WMR. Smooth and asymptotically stable tracking of the WMR along the desired position and orientation is ensured and real-time experiment demonstrates the effectiveness and simplicity of the proposed method.

Direction and control adjustment for smooth motion of wheeled mobile robots

Control of wheeled mobile robots (differential or steering wheel structure) has been studied extensively in the last decades, and many control strategies were proposed for various applications. This paper will present the solutions to two issues encountered in the implementation of the controllers: over corrections of the robot's heading direction and saturation of the control efforts. The solutions to the problems and their experimental verifications are provided.

Study of the internal dynamics of an autonomous mobile robot

The requirement of ideal rolling without sideways slipping for wheels imposes nonholonomic (non-integrable) constraints on the motion of the wheels and consequently on the motion of wheeled mobile robots. From the control point of view, the dynamics of nonholonomic systems can be divided in two parts: external and internal dynamics. The dimension of the external dynamics of nonholonomic systems depends on the number of inputs to the system and the dimension of the internal dynamics depends on the number of independent nonholonomic constraints. For different motion control problems of nonholonomic systems, a smooth (model based) state feedback control law only deals with the system external dynamics; therefore, the system internal dynamics must be examined separately and its stability has to be analyzed and proved. In this paper, the internal dynamics of a three-wheel mobile robot with front wheel steering and driving is investigated. In particular, its internal dynamics stability is analyzed for two different situations, when the mobile robot is moving and when it is stationary.

Analytical framework for the smooth manoeuvre of wheeled mobile robots traversing obstacles

The aims of this paper are twofold. The first aim is to employ a vectorial approach to model the dynamics of wheeled mobile robots (WMRs), which need to travel over localized surface irregularities. This approach results in compact vectorial equations which are more easily programmable using a symbolic programming software tool. The second aim is to apply the model in conjunction with temporal trajectory functions to compute the traction–force requirements of WMRs traversing obstacles of specified profiles. This model–based approach provides a more robust framework for the development of active control of the motion of WMRs traversing obstacles. It is demonstrated that, during obstacle traversing, a compromise can be achieved between the minimal times of manoeuvre on the one hand and traction force, inertia load and geometrical properties of WMRs and obstacles on the other. The traction force needed to complete the manoeuvre may change sign, necessitating a switch to a braking action. This shift between the traction mode and braking mode of the actuators can be avoided by an appropriate choice of a minimum time of manoeuvre. This study also provides a basis for the selection of an appropriate manoeuvre time based on prior knowledge of the friction characteristics of a traction surface.

Tracking control for an object in pushing operation

We consider the problem of making a manipulator push an object on a flat floor with point contact to a desired position. A manipulator control method for the object to follow a planned trajectory as proposed. First, using the given distribution of frictional forces between the object and the floor, we find out a particular point, named pseudo center, on which the motion of the pushed object cart be approximates by the motion of wheeled mobile robot on its center. Then, a control rule of the pushing operation is derived by applying a tracking control rule for a nonholonomic mobile robot at the pseudo center. This method makes it possible for the robot to perform the tracking control in the pushing operation. A simulation result shows the effectiveness of the proposed method. Finally, we give an, approach to use a mobile manipulator for realizing the pushing operation. Experimental verification on the proposed method is performed and its result is described.

Highly Accurate Dynamic Position Measurement for Wheeled Mobile Robot Using Laser Beacon Measuring System.

The present research concerns a compensation method for dynamic measurement error using the laser beacon measuring system (LBMS), which is necessary for highly accurate positioning control and trajectory tracking control of a wheeled mobile robot (WMR). The LBMS uses particular laser beacons, each of which emits two symmetrical laser beams traveling in opposite directions around the beacon. The beacons are placed at two reference positions. Receiving beams from these beacons, a photosensor carried on a sensor unit of WMR yields four time intervals which are necessary to calculate the position of WMR. The position of a standing WMR can be measured with high accuracy by LBMS. However, the position of a moving WMR can not be measured as accurately, because the above-mentioned four time intervals change slightly owing to motion of WMR and consequently, dynamic measurement error arises. The proposed method is the one which compensates the position of a moving WMR measured by LBMS, making use of the dynamic measurement error calculated from four different time intervals. In this paper, we report on this compensation method which has been found to yield satisfactory results concerning its accuracy and repeatability after various simulations and experiments.

押し作業における対象物の軌道追従制御

This paper presents a control method of pushing an object with point contact to control its position and orientation along a given trajectory. First, using the given distribution of frictional forces between the object and a support surface, we find out a particular point, named pseudo center, on which the motion of the pushed object can be approximated by the motion of wheeled mobile robot on its center. Then, a control rule of the pushing operation is derived by applying a tracking control rule for a non-holonomic mobile robot at the pseudo center. This method makes a robot possible to perform the tracking control in the pushing operation. A simulation result shows the effectiveness of the proposed method. Finally, we give an approach to use a mobile manipulator for realizing the pushing operation. Experimental verification on the proposed method is performed and its result is described.

車輪式移動ロボットの運動学および動力学の一般理論に関する研究

This paper proposes a general theory for kinematics and dynamics of wheeled mobile robots (WMRs) . This study has two features: 1) The proposed method can deal with various WMR system ranging from typical three or four-wheeled mobile robot to multi-WMR systems where multiple WMRs are connected by joints. A WMR is regarded as a planar linkage mechanism with several ends: wheels correspond to the ends. Generally, a WMR system has active joints such as steering axis, passive joints such as casters and couplers, and driven/non-driven wheels. A model of WMR system called tree structure link covering these configurations is proposed. 2) This theory deals with kinematics and dynamics of WMR including slip of wheels. WMR dynamics is derived regarding frictional force between wheels and the ground as an external force which is a function of the slip speed. When no slip is assumed in wheels, WMR's motion is expressed by kinematics. In this manner, the proposed method is applied systematically on the kinematics when slip can be neglected and the dynamics when slip exists. Furthermore, velocity input dynamics is proposed which gives the motion of WMR when the velocity commands are inputs to active joints and wheels under the condition that wheels slip.

Kinematic modeling of wheeled mobile robots

AbstractWe formulate the kinematic equations of motion of wheeled mobile robots incorporating conventional, omnidirectional, and ball wheels.1 We extend the kinematic modeling of stationary manipulators to accommodate such special characteristics of wheeled mobile robots as multiple closed‐link chains, higher‐pair contact points between a wheel and a surface, and unactuated and unsensed wheel degrees of freedom. We apply the Sheth‐Uicker convention to assign coordinate axes and develop a matrix coordinate transformation algebra to derive the equations of motion. We introduce a wheel Jacobian matrix to relate the motions of each wheel to the motions of the robot. We then combine the individual wheel equations to obtain the composite robot equation of motion. We interpret the properties of the composite robot equation to characterize the mobility of a wheeled mobile robot according to a mobility characterization tree. Similarly, we apply actuation and sensing characterization trees to delineate the robot motions producible by the wheel actuators and discernible by the wheel sensors, respectively. We calculate the sensed forward and actuated inverse solutions and interpret the physical conditions which guarantee their existence. To illustrate the development, we formulate and interpret the kinematic equations of motion of Uranus, a wheeled mobile robot being constructed in the CMU Mobile Robot Laboratory.