Class Of Wheeled Mobile Robots Research Articles

AI-based smart and intelligent wheelchair

The differently abled and/or old-aged people require assistance for their movement. Generally, such assistant providing tool is wheelchair. Normal wheelchairs are manually operated and heavy to move adding burden to the suffered. Hence, automated wheelchairs that are equipped with sensors and a data processing unit constitute a special class of wheeled mobile robots, termed as “smart wheelchairs” in general. In the existing system, the wheelchair movement that is controlled by joystick uses buttons to start and stop the wheel. This is difficult for the differently abled to press the required button with precision. Although there are smart wheelchairs with gesture control, it lacks accuracy in the calculation of the location. The proposed system uses artificial intelligence for its working and proves to be a unique combination of wheelchair and health monitoring system. The wheelchair can be accessed both in manual and automatic modes. In the manual mode, the wheel is controlled using joystick whereas in the automated mode, MPU6050 sensor and accelerometer is used to control the direction by gesture. SPO2 sensor attached to the wheelchair is used to collect the health parameters. Thus, enabling the self-dependency of the person. Further, deep learning analysis of the data from the sensors and the wheelchair usage pattern is compared with the dataset to determine the stress level. The signal from the sensors is monitored and the vitals data is updated in the ThingSpeak website via Bluetooth module serving as a digital health chart.

Adaptive-observer-based dynamic surface tracking of a class of mobile robots with nonlinear dynamics considering unknown wheel slippage

This paper addresses an adaptive-observer-based control design problem for path tracking of a class of wheeled mobile robots in the presence of unknown slippage effects. The linear and angular velocities of mobile robots are assumed to be unmeasurable. This causes nonlinear coupling terms between the unmeasurable velocities and unknown skidding and slipping effects in the robot dynamics, making the design of an adaptive observer difficult. An adaptive observer is presented to estimate unmeasured velocities of the mobile robots and to compensate for the skidding and slipping effects. Then, a simple adaptive controller at the dynamic level is derived using dynamic surface design methodology. Fuzzy logic systems are employed to overcome the coupling problems between the unmeasurable velocities and unknown skidding and slipping effects in the controller design procedure. From Lyapunov stability analysis, the stability of the controlled closed-loop system is analyzed under slippage conditions.

Adaptive tracking control for a class of wheeled mobile robots with unknown skidding and slipping

This study presents an adaptive tracking control approach for trajectory tracking of wheeled mobile robots with torque saturation in the presence of unknown skidding and slipping. The robot kinematics and dynamics are induced from the perturbed non-holonomic constraints. The adaptive control system using the kinematics transformed in polar coordinates is developed to compensate unknown skidding and slipping at the dynamic level of mobile robots with the input saturation. All signals of the controlled closed-loop system are uniformly bounded and the point tracking errors converge to an adjustable neighbourhood of the origin regardless of large initial tracking errors, input saturation and unknown skidding and slipping. Simulation results are provided to demonstrate the performance and stability of the proposed control scheme.

Steering control algorithm for a class of wheeled mobile robots

The authors present a simple steering control algorithm for a class of non-holonomic wheeled mobile robots. Five different types of wheeled mobile robots are considered. The feedback controls are piece-wise constant, states dependent and the method is based on the construction of a cost function V, which is sum of two semi-positive definite functions V1 and V2. The first m state variables can be steered along the given vector fields directly using the classical controls and remaining n–m state variables can be steered along the missing Lie brackets indirectly. The task of the control strategy is to decay the non-differentiable cost function along the controlled system trajectories only asymptotically. The beauty of the algorithm is that it does not require the conversion of the system models into ‘chained form’ and does not rely on any special transformation techniques.

Controllability and Posture Control of a Wheeled Pendulum Moving on an Inclined Plane

The paper considers a specific class of wheeled mobile robots, namely, mobile wheeled pendulums (MWPs). Robots pertaining to this class are composed of two wheels rotating about a central body. The main feature of MWP pertains to the central body, which can rotate about the wheel axis. As such motion is undesirable, the problem of the stabilization of the central body in an MWP is crucial. The novelty of the work reported here resides in the construction of: 1) the system controllability Lie algebra for the purpose of a rigorous controllability analysis and the computation of the largest feedback-linearizable subsystem; 2) a controller by input-output linearization of the system for achieving the desired steering rate of the robot while stabilizing the central body; 3) a controller based on the internal properties of the system to achieve the desired heading velocity of the robot; and 4) a controller based on the sliding-mode approach for controlling both the position and the orientation of the robot. The entire control structure that permits full control of the robot posture comprises three imbricated loops. Simulations showing good performance of the controlled system are provided. Preliminary tests performed on an experimental platform confirm the validity of the controller.

SENSITIVITY ANALYSIS OF LOW COST FUZZY CONTROLLED SERVO SYSTEMS

The paper performs the sensitivity analysis with respect to the parametric variations of the controlled plant in the case of low cost fuzzy control systems dedicated to servo systems, with focus on solving the tracking control problem for a class of wheeled mobile robots with two degrees of freedom used in mining technologies. A new development method for Takagi-Sugeno PI-fuzzy controllers is proposed, based on applying the Extended Symmetrical Optimum method to the basic linear PI controllers in a cascaded control system structure. Original sensitivity models are derived. The approaches are validated by a case study.

Sensitivity Analysis of a Class of Fuzzy Controlled Mobile Robots

The paper deals with the sensitivity analysis of fuzzy control systems solving the tracking control problem for a class of wheeled mobile robots with two degrees of freedom. There is proposed a development method for PI-fuzzy controllers based on the application of the Extended Symmetrical Optimum method to the basic linear PI controllers. A cascaded control system structure is considered employing the off-line generation of the reference inputs by means of the artificial potential field method for obstacle avoidance. Digital simulation results for a case study validate the theoretical approaches.

Discontinuous feedback stabilization of nonholonomic wheeled mobile robots

We present a new discontinuous stabilizing controllerfor a class of wheeled mobile robots with nonholonomic constraints.This stabilizing controller has a number of desirable properties:it is simple, the state of the robot asymptotically convergesto the target configuration, and the resulting trajectory issmooth. Theoretical and simulation results are both presented.

Optimal kinematic path tracking control of mobile robots with front steering

SummaryThis work concerns the class of wheeled mobile robots with single axis front steering. Because of the relatively low speed of these vehicles their dynamic properties have little effect on their path tracking behaviour. Their motion is, moreover, on a flat environment and can be assumed two dimensional.The kinematics of motion of such a vehicle can be utilized for design of control strategies for maintaining path following stability. In this paper, optimal control technique is implemented to such a system. First, the state space equations governing the motion are derived. The orientation error and the offset from a path form the states and the steering angle is the control input to the system. An optimal controller to minimize the two errors and the steering angle is then sought. The conditions for the existence of the feedback matrix are discussed. The controller structure is defined in terms of the forward speed of the vehicle and, thus, has the advantage of being flexible for speed changes. Numerical illustrative examples, however, demonstrate that variation of the speed has no effect on the controller structure.

Synthesis of an optimal control law for path tracking in mobile robots

An optimal control law is derived for path tracking control of a class of wheeled mobile robots (WMR) or automated guided vehicles with front steering wheel. Optimality is based on minimizing a quadratic performance index in the position and orientation errors and the steering angle. The existence of such a controller which is in the form of a linear feedback of the two errors (position and orientation) formally proves why such a system can be stabilized about a trajectory by using position and orientation error feedback to determine the command to the steering angle. (This has been widely used recently.) The effect of the controller is illustrated by simulation results for various initial conditions in an experimental vehicle.