Differential Wheeled Mobile Robots Research Articles

Decentralized fault-tolerant control of multi-mobile robot system addressing LiDAR sensor faults

The control of multi-robot formations is a crucial aspect in various applications, such as transport, surveillance and monitoring environments. Maintaining robots in a specific formation pose or performing a cooperative task is a significant challenge when a fault occurs among any of the robots. This work presents a Decentralized Fault-Tolerant Control (DFTC) scheme that addresses lidar sensor faults within a system of multiple differential wheeled mobile robots. The robots change the formation shape according to the number of available robots within the formation. A Graph theory is implemented to represent the multi-robot formation and communication. Each mobile robot is equipped with three sensors: a wheel encoder, an Inertial Measurement Unit (IMU), and a lidar sensor. Sensor fault detection and isolation (FDI) is implemented at two levels. The pose estimation obtained from the wheel encoder and IMU is fused using an extended Kalman filter (EKF), and this pose estimation is utilized at the local level of lidar sensor FDI. At the system level, the FDI of the lidar sensor involves computing a residual by comparing the pose estimation with other lidar sensors mounted on other mobile robots within the formation. The presented FTC scheme is simulated in Simulink multi-robot environments.

Correction: Trajectory Tracking of Differential Wheeled Mobile Robots with Input Saturation and Mismatched Centers

Correction: Trajectory Tracking of Differential Wheeled Mobile Robots with Input Saturation and Mismatched Centers

Enhanced path planning algorithm via hybrid WOA-PSO for differential wheeled mobile robots

This study introduces an enhanced algorithm for global path planning of Differential Wheeled Mobile Robots (DWMRs) that merges the Whale Optimization Algorithm (WOA) and Particle Swarm Optimization (PSO). This hybrid strategy, termed HWPSO, is designed to leverage WOA's exploration strength with PSO's efficient exploitation, specifically targeting the challenges of non-holonomic constraints in complex terrains. To validate the effectiveness of the proposed algorithm, its performance is evaluated across five diverse environments and compared against PSO, WOA, and Grey Wolf Optimization which is widely used for mobile robot path planning. Moreover, the comparison broadens to encompass four established environments from the literature where algorithms based on firefly, ant colony, A*, and other PSO variants have previously exhibited optimal performance. Additionally, a new environment is introduced to analyze the efficacy of the proposed approach for path planning for two DWMRs. Simulation results consistently demonstrate the superiority of the proposed HWPSO, manifesting performance improvements of up to 19.3% for path length reduction and up to 12.7% for DWMR travel duration reduction when compared to other methods. This underscores the efficacy of the proposed hybrid approach in achieving enhanced path planning outcomes for DWMRs in diverse scenarios.

Trajectory Tracking of Differential Wheeled Mobile Robots with Input Saturation and Mismatched Centers

Trajectory Tracking of Differential Wheeled Mobile Robots with Input Saturation and Mismatched Centers

Tracking Control of Mobile Robots based on Rhombic Input Constraints

This paper focuses on the trajectory tracking control algorithm for Differential Wheeled Mobile Robots (DWMRs) based on rhombic input constraints. The kinematics and dynamics model of DWMRs are established, and vector analysis method is used to design the controller when the linear velocity and angular velocity of DWMRs were not mutually independently. Through the simulation of tracking 8-shaped curve, a good control performance is obtained.

Trajectory Tracking Control of Differential Wheeled Mobile Robots Based on Rhombic Input Constraints

Trajectory Tracking Control of Differential Wheeled Mobile Robots Based on Rhombic Input Constraints

Trajectory Tracking of Wheeled Mobile Robots Using Z-Number Based Fuzzy Logic

Being trajectory tracking key for safe mobile robot navigation, Fuzzy Logic (FL) has been useful in tackling uncertainty and imprecision to realize robust and smooth trajectory tracking. In this paper, we present the Z-number based Fuzzy Logic control for trajectory tracking of differential wheeled mobile robots. The unique point of our approach lies in the ability to encode constraint and reliability in multi-input and multi-output rules, whose antecedent universe considers only the instantaneous measurements of distance and the orientation gaps, and whose consequent universe is computed by the interpolative reasoning and the graded mean integration approach. As a consequence, not only our approach avoids the complexity of encoding error gradients, but also is advantageous to model versatile control rules able to cope with missing observations and noisy inducements on actuators. Our experiments using both physics-based simulations and real-world tests based on a Pioneer 3DX robot architecture have elucidated the superior efficacy and the feasibility of the proposed controller regarding accuracy, robustness, and smoothness compared to other well-known related frameworks such as Fuzzy Logic Type 1, Fuzzy Logic Type 2 and Fuzzy Logic with PID. Our results provide unique insights to realize generalizable algorithms aided by FL and Z-number towards robust trajectory tracking.

Cornering Trajectory Planning Avoiding Slip for Differential-Wheeled Mobile Robots

In this article, we propose an efficient algorithm for cornering trajectory planning avoiding slip based on dynamics for differential-wheeled mobile robots (DWMRs). In general, slip between tires and the ground increases odometry errors. Hence, to consider not only full dynamics, including actuators, but also slip avoidance, we formulate a complex planning problem, in which the following essential constraints are imposed: longitudinal and lateral force constraints to avoid slip and motor control input bounds for DWMR dynamics, including actuators. Given a single corner, the proposed trajectory is divided into three turning sections, which are composed of multiple intervals. In order to satisfy all constraints, the intervals are then split into several subintervals, which are with constant or time-varying control inputs based on the bang–bang principle or on force constraint bounds for optimal acceleration. We then find two local minimum trajectories by analyzing the time trend w.r.t. the turning radius for cornering. These are the low-velocity decrease trajectory and the shortest distance trajectory. The time-optimal solution is determined by the minimum of the local minima. Both simulations and experiments are conducted to verify the effectiveness of the proposed algorithm.

Global Trajectory Planning Based on DWMR Dynamics in Circular C-space

This paper proposes an efficient near time-optimal trajectory planning algorithm for differential wheeled mobile robots(DWMRs) in a circular C-space under constraints on robot’s kinematics, dynamics, and motor’s voltage. This problem is considered to be complex if there exist lots of obstacles to pass and robot’s dynamics including motor’s dynamics should be considered. A* algorithm is incorporated into the modified TOTP (Time Optimal Trajectory Planning) algorithm [1] to find near minimum time trajectory without any homotopy class by defining a node as an obstacle with direction information. In addition, TOTP algorithm is improved so that the proposed algorithm can be applied to the environment without any assumption about the distance between obstacles. Simulations show that the proposed algorithm is applied in an environment where multiple obstacles exist. An experiment shows that the generated trajectory by the proposed algorithm is well followed by the robot.

Adaptive Distributed Fault-tolerant Formation Control for Multi-robot Systems under Partial Loss of Actuator Effectiveness

This paper presents an adaptive distributed fault-tolerant formation control for multi-robot systems. Both the kinematics and dynamics of differential wheeled mobile robots are considered. In particular, the problem caused by actuator faults is investigated. Based on dynamic surface control techniques, adaptive formation controllers can be obtained under a directed communication network. The closed-loop stability is guaranteed by using Lyapunov stability analysis such that all followers can exponentially converge to a leader-follower formation pattern. Simulation and experimental results illustrate that the desired formation pattern can be preserved for a group of wheeled robots subject to unknown uncertainties and actuator faults.

Time-Optimal Trajectory Planning Based on Dynamics for Differential-Wheeled Mobile Robots With a Geometric Corridor

We propose an efficient time-optimal trajectory planning algorithm for an environment with multiple static circular obstacles, which is based on dynamics for differential-wheeled mobile robots (DWMRs) including actuators. This problem is known to be complex particularly if obstacles are present and if full dynamics including actuators is considered. Given a geometric corridor, the proposed technique defines a portion of trajectory between obstacles as a section which is constituted of an arc, out-curve, and in-curve, each with constant control input satisfying bang–bang principle for time-optimization. Then, it designs time-optimal trajectory composed of multiple sections using common tangent between two tangent circles, in which it handles multiple consecutive obstacles without arcs. This method helps to treat complex environment considering dynamics with DWMR's actuators. Simulation results are shown to validate the efficiency of the proposed algorithm.

Design of a redundant wheeled drive system for energy saving and fail safe motion

Mobile robots are widely used in many applications, such as transportation, military domain, searching, guidance, rescue, hazard detection, and carpet cleaning. Because mobile robots usually carry limited power sources, such as batteries, energy saving is an important concern. In particular, differential wheeled mobile robots that have two independently movable wheels are popular because of relatively low mechanical complexity to achieve three-dimensional motion on a ground. This article presents a new wheeled device with a redundant drive system which consists of three independently movable actuators and two planetary gears to connect the actuators to two wheels. The proposed system is able to continue its motion safely when one of the motors breaks down for some causes and also able to operate over a longer period of time due to energy saving consumption property. Experimental results show that the proposed method is effective in saving energy approximately by 20.45% for linear motion and 13.05% for circular motion compared to a conventional one.

CONTROL SYSTEMS SIMULATOR FOR WHEELED ROBOTS USING EASY JAVA SIMULATIONS

This paper describes a control systems simulator for differential wheeled mobile robots using Easy Java Simulations and Simulink® interconnected. This simulator provides a tool to study and simulate control systems. Also, a simulation example is presented using velocity field control with the results and a brief explanation. This simulator offers a new option for those users interested on wheeled mobile robots navigation control, who want to simulate their models. To achieve this, the application allows: position control with X, Y and angle reference set by the user; reference using velocity fields, robot dynamics, and contact sensors.