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Flexible members such as solar panels of robotic systems during a maneuver may get stimulated and vibrate. ‎Therefore, such vibrations will cause some oscillatory disturbance forces on the moving base and manipulated ‎object, which in turn produces error in the position and speed of the manipulating end-effectors, which should be ‎prevented. In this paper, a new control algorithm for an object manipulation task by a wheeled mobile robotic ‎system with flexible members is proposed. To this end, a new dynamics modelling approach for control ‎implementations on compounded rigid-flexible multi-body systems is introduced. Then, based on a designed ‎path/trajectory for a wheeled mobile robotic system, an Adaptive Hybrid Suppression Control (AHSC) is proposed ‎to perform an object manipulation task by such complicated rigid-flexible multi-body systems. Finally, a wheeled ‎mobile robotic system is simulated which contains two manipulators, and a rotating antenna and a camera as its ‎third and fourth arms, appended with two solar panels as has been proposed for space explorations. Obtained ‎results reveal the merits of the proposed AHSC algorithm which will be discussed.‎

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Tractor-trailer wheeled mobile robot (TTWMR) is a robotic system that consists of a tractor module towing a trailer. Trajectory tracking is one of the challenging problems which is focused in the context of wheeled mobile robots (WMRs) that has been discussed in this paper. First, kinematic equations of TTWMR are obtained. Then, reference trajectories for tracking problem are produced. Subsequently, an output feedback kinematic control law and a dynamic Fuzzy Sliding Mode Control (FSMC) are designed for the TTWMR. The proposed controller steer the TTWMR asymptotically follow reference trajectories. Finally, experimental results of the designed controller on an experimental setup and comparison results are presented. Obtained results show the effectiveness of the proposed controller.

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In this paper, trajectory tracking control of a wheeled mobile robot is analyzed. Wheeled mobile robot is a nonlinear system. This system including three generalized coordinates (x,y,ϕ), and a nonholonomic constraint. First, system kinematic and dynamic equations are obtained. A non-model-based control algorithm using PD-action filtered errors has been used in order to control the wheeled mobile robot. Non-model-based controllers are always more appropriate than model-based algorithms due to independency from dynamic models, lower computational costs and also robustness to uncertainties. Asymptotic stability of the closed loop system for trajectory tracking control of wheeled mobile robot has been investigated using appropriate Lyapunov function and also Barbalat’s lemma method. Finally, in order to show the effectiveness of the proposed approach simulation and experimental results have been presented. Obtained results show that without requiring a priori knowledge of plant dynamics, and with reduced computational burden, the tracking performance of the presented algorithm is quite satisfactory. Therefore, the proposed control algorithm is well suited to most industrial applications where simple efficient algorithms are more appropriate than complicated theoretical ones with massive computational burden.

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Trajectory tracking is one of the main control problems in the context of Wheeled Mobile Robots (WMRs). Besides, control of underactuated systems possesses a particular complexity and importance; so it has been focused by many researchers in recent years. In this paper, these two important control subjects are discussed regarding a Tractor-Trailer Wheeled Mobile Robot (TTWMR); which includes a differential drive wheeled mobile robot towing a passive spherical wheeled trailer. The use of spherical wheels instead of standard wheels in trailer makes the robot highly underactuated with severe nonlinearities. Spherical wheels are used for the trailer to increase robots’ maneuverability. In fact, standard wheels create nonholonomic constraints by means of pure rolling and nonslip conditions, and reduce robot maneuverability. In this paper, after introducing the robot, kinematics and kinetics models are obtained, and combined as the dynamics model. Then, based on physical intuition a new controller is developed for the robot, named as Lyapaunov-PID control algorithm. Then, singularity avoidance of the proposed algorithm is discussed and the stability of the algorithm is discussed. Simulation results reveal the suitable performance of the proposed algorithm. Finally, experimental implementation results are presented which verify the simulation results.

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A solar-powered robot is a mobile robot powered completely or significantly by direct solar energy. The sun's energy is converted into electric energy by solar panels mounted on the robot. These solar panels are required to be light, because of the important demands for low-energy consumption. As a result of the flexibility of elements of the panels, undesirable low-frequency vibration may occur when the robot moves on a rough terrain. In this paper, a new method for stabilization of solar panels vibration base on trajectory planning for articulated mobile robot is presented. The dynamics of solar panels attached to the robot is derived using Kane’s method. The attitude and configuration of a rover as a function of the terrain on which it moves is determined using inverse kinematics of the robot. The attitude and configuration of a rover is required to approximate the domain of vibration by derived dynamics equations. Base on this approximation, a trajectory planning algorithm is presented that can reduce vibration without significant decrease in the velocity of the robot. The proposed method is simulated for a six-wheeled mobile robot with rocker-bogie structure The obtained results show that the algorithm stable the domain of vibration in allowable area and do not decrease the velocity of the robot significantly.

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One of the main topics in the field of robotics is the formation control of the group of robots in trajectory tracking problem. Using organized robots has many advantages compared to using them individually. Among them the efficiency of using resources, the possibility of robots' cooperation, increasing reliability and resistance to defects can be pointed out. Therefore, formation control of multi-body robotic systems and intelligent vehicles attracted considerable attention that is discussed in this paper. First, kinematic and kinetic equations of a differential drive wheeled robot are obtained. Then, reference trajectories for tracking problem of the leader robot are produced. Next, a kinematic control law is designed for trajectory tracking of the leader robot. The proposed controller steer the leader robot asymptotically follow reference trajectories. Subsequently, a dynamic control algorithm for generating system actuator toques is designed based on feedback linearization method. Afterwards, formation control of the robots has been considered and an appropriate algorithm is designed in order to organize the follower robots in the desired configurations, meanwhile tracking control of the wheeled robot. Furthermore the stability of the presented algorithms for kinematic, dynamic and formation control laws is analyzed using Lyapunov method. Finally, obtained results for different reference paths are presented which represents the effectiveness of the proposed controller.

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Numerous studies have been devoted to motion control of wheeled mobile robots in recent years. Among them, trajectory tracking has received much attention.. A feed-forward and feedback control structure for trajectory tracking is used to circumvent the limitation of Brockett’s theorem. Feed-forward control is calculated according to the reference trajectory, it can not compensate instrumentation and initial state errors, therefore a feedback controller is utilized as well. In this paper a model predictive controller is used as the feedback controller. Since the initial state is not often matched to the desired trajectory, rapid tracking of the trajectory in early steps is very important. In this paper a model predictive controller with laguerre functions and another one with exponential data weighting is used to reduce tracking error in early steps. According to simulation results, reference trajectory tracking is improved through laguerre functions in model predictive controller.

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One of the main topics in the field of robotics is the motion control of wheeled mobile robots. Motion control encompasses trajectory tracking and point stabilization problems. In this paper these control problems will be considered for the tractor-trailer wheeled robots and a predictive control algorithm is developed for solving these problems. Therefore first kinematic model of the tractor_trailer robot is developed. Next, reference trajectories is produced for the system. Subsequently, predictive control law is designed for the trajectory tracking and point stabilization problems. Predictive control based on the known values of reference trajectories in the future, produces the control inputs in present time. Consequently the error signal with respect to the reference trajectory in future will be used in order to control the system at the present instant of time. This method is developed for solving the aforementioned control problems and is employed on the tractor_trailer wheeled robot. As can be seen from the results, the proposed control algorithm steer the wheeled robot asymptotically follow reference trajectories. Obtained results from the implementation of the proposed method for solving trajectory tracking and point stabilization problems, demonstrate the effectiveness of the presented algorithm.

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There exist satisfactory results in the analysis of the motion control of the vehicles with the assumption of nonslip (pure rolling) condition of robot wheeles, But unfortunately in practice due to the presence of uncertainties such as sliding of wheels especially in agriculture applications where working conditions are rough the results and the quality of the control performance of the system are affected. The ideal control of wheeled systems is performed with the assumption of the existence of nonholonomic non-slip constraints, while in the real system these constraints are violated due to the presence of slippages. In this paper the problem of trajectory tracking control of wheeled vehicles in the presence of sliding is addressed. To take sliding effects into account, sliding models are introduced into the kinematic model. In other words, these effects are added as unknown parameters to the ideal kinematic model. For taking into account the sliding effects their mathematical models are introduced in system kinematic model. In another word these effects as an unknown parameters are added to the system ideal kinematics. An integrating parameter adaptation technique and backstepping control algorithm has been utilized in order to control the system. The backstepping control law is designed to track the reference trajectories and make the robot asymptotically stable around the reference trajectories. Finally, the obtained results are presented for tracking reference trajectories and comparison results shows the efficiency of using the estimation of slips in control of the system.

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