A tractor-trailer wheeled robot (TTWR) is a kind of modular robotic system that consists of a tractor template attached with a single or multiple trailers, and hence it is a nonlinear and underactuated system subjected to nonholonomic constraints. Tracking control of such a complicated system is a challenging problem, and that is the focus of this paper. To this end, first dynamics model of a TTWR is developed. Next, feasible reference trajectories are generated to define a trajectory tracking problem. Then, a Lyapunov kinematic control law is elaborated to stabilize tracking errors. Subsequently, a feedback linearizing dynamic controller (FLDC) is designed to generate actuator torques. In a wheeled mobile robot (WMR), like most of real engineering applications, it is impossible to obtain an exact dynamics model due to various unknown, or unpredictable and irregular features. Therefore, the robustness of controllers to overcome uncertainties and external disturbances is necessary. So, a robust adaptive feedback linearizing dynamic controller (RAFLDC) is proposed to control the system using estimated upper-bounds of uncertainties. The stability of the control algorithm is verified using the Lyapunov method. Robustness and effectiveness of the proposed controller, and comparison of results for RAFLDC and FLDC algorithms, is investigated using both simulation studies and experimental implementations, and obtained results will be discussed.

SUMMARY: Free-flying space manipulator systems, in which robotic manipulators are mounted on a free-flying spacecraft, are envisioned for assembling, maintenance, repair, and contingency operations in space. Nevertheless, even for fixed-base systems, control of mechanical manipulators is a challenging task. This is due to strong nonlinearities in the equations of motion, and consequently different algorithms have been suggested to control end-effector motion or force, since the early research in robotic systems. In this paper, first a brief review of basic concepts of various algorithms in controlling robotic manipulators is introduced. Then, specific problems related to application of such systems in space and a microgravity environment is highlighted. Basic issues of kinematics and dynamics modeling of such systems, trajectory planning and control strategies, cooperation of multiple arm space free-flying robots, and finally, experimental studies and technological aspects of such systems with their specific limitations are discussed.

Step adjustment can improve the gait robustness of biped robots; however, the adaptation of step timing is often neglected as it gives rise to nonconvex problems when optimized over several footsteps. In this article, we argue that it is not necessary to optimize walking over several steps to ensure gait viability and show that it is sufficient to merely select the next step timing and location. Using this insight, we propose a novel walking pattern generator that optimally selects step location and timing at every control cycle. Our approach is computationally simple compared to standard approaches in the literature, yet guarantees that any viable state will remain viable in the future. We propose a swing foot adaptation strategy and integrate the pattern generator with an inverse dynamics controller that does not explicitly control the center of mass nor the foot center of pressure. This is particularly useful for biped robots with limited control authority over their foot center of pressure, such as robots with point feet or passive ankles. Extensive simulations on a humanoid robot with passive ankles demonstrate the capabilities of the approach in various walking situations, including external pushes and foot slippage, and emphasize the importance of step timing adaptation to stabilize walking.

Nowadays, aerial robots or Unmanned Aerial Vehicles (UAV) have many applications in civilian and military fields. For example, of these applications is aerial monitoring, picking loads and moving them by different grippers. In this research, a quadrotor with a cable-suspended load with eight degrees of freedom is considered. The purpose is to control the position and attitude of the quadrotor on a desired trajectory in order to move the considered load with constant length of cable. So, the purpose of this research is proposing and designing an antiswing control algorithm for the suspended load. To this end, control and stabilization of the quadrotor are necessary for designing the antiswing controller. Furthermore, this paper is divided into two parts. In the first part, dynamics model is developed using Newton-Euler formulation, and obtained equations are verified in comparison with Lagrange approach. Consequently, a nonlinear control strategy based on dynamic model is used in order to control the position and attitude of the quadrotor. The performance of this proposed controller is evaluated by nonlinear simulations and, finally, the results demonstrate the effectiveness of the control strategy for the quadrotor with suspended load in various maneuvers.

Toincrease the mobility of on-orbit robotic systems, Space Free-Flying Robots (SFFR) in which one ormore manipulators are mounted on a thruster-equipped base, have been proposed. Unlike fixedbased manipulators, the robotic arms of SFFR are dynamically coupled with each other and the freeflying-base, hence the control problem becomes more challenging. In this paper, the Multiple Impedance Control (MIC) is developed,to manipulate space objects by multiple,arms of SFFR. The MIC law is based ,on the ,concept of designated ,impedances and enforces them at various ,system levels, i.e., the free-flying base, all cooperating manipulators, and the manipulated object itself. The object may include an internal angular momentum source, as is the case in most satellite manipulation tasks. The disturbance rejection characteristic of this algorithm is also studied. The result of this ,analysis reveals that the effect of ,disturbances ,substantially reduces ,through 2 appropriate tuning of the controller mass matrix gain. A system of three manipulators mounted,on a free-flying base is simulated in which ,force and torque disturbances are exerted at several points. The system dynamics ,is developed ,symbolically and the controlled system is simulated. The

This paper focuses on the dynamics of a multiple manipulator space free-flying robot (SFFR) with rigid links and issues relevant to the development of appropriate control algorithms. To develop an ...