Decoupled Control Design of Aerial Manipulation Systems for Vegetation Sampling Application

With the development of rotor aerial robot, it has been widely used as a stabilized flying platform to achieve observation, communication relay and so on by equipping corresponding equipment, which are always called passive tasks. However, many applications need rotor aerial robots to possess more active capability, such as grasp, carry and assemblage. Thus, the demand for an aerial manipulation system gradually appears, and becomes a hot research issue in recent years. Aerial manipulator system, usually composed of rotor aerial robot and the manipulator, is a new type of robot system with active operating capability. Compared with the mobile manipulator based on the ground and underwater mobile robot which is now widely applied, the aerial manipulation has lager working range and better flexibility obviously. Unfortunately, the new aerial manipulation system also brings new challenges, such as strong dynamics coupling, the modeling and stabilization problem, etc. which may affect its further application. Thus, in our work, an actual physical aerial manipulator system is designed and implemented for its system and application research. Based on the system, the preliminary modeling and control was researched and also an experiment for grasping and carry application is conducted. The conclusions of these researches will help us to realize and improve the system in the future.

Torch relay is an important tradition of the Olympics and heralds the start of the games. Robots applied in the torch-relay activity can not only demonstrate the technological capability of humans to the world but also provide a sight of human lives with robots in the future. This article presents an aerial manipulator designed for the robot-to-robot torch-relay task of the Beijing 2022 Winter Olympics. This aerial manipulator system is composed of a quadrotor, a 3 degree of freedom (DoF) manipulator, and a monocular camera. This article primarily describes the system design and system control scheme of the aerial manipulator. The experimental results demonstrate that it can complete a robot-to-robot torch-relay task under the guidance of vision in the ice and snow field.

Control of an aerial manipulator is challenging due to the decentralized dynamics of the aerial vehicle and the robotic arm. It is generally complex to adjust the controller of the aerial manipulator when replacing a different robotic arm. This paper presents a flexible control scheme for a quadrotor-based aerial manipulator equipped with a replaceable robotic arm. To analyze the dynamic characteristics during grasping, the model of the aerial manipulator is decentralized including the models of a quadrotor and the centroid of an n-DOF robotic arm. The interaction effect of a moving robotic arm on the quadrotor is considered by analyzing the varying centroid of the robotic arm. Based on the modeling of the aerial manipulator, a control scheme integrating a linear model predictive control (LMPC) and a feedforward controller is presented to accurately control the motion of the aerial platform. The LMPC controls the aerial vehicle to follow the desired trajectory, and a feedforward controller keeps the aerial platform hovering stably during grasping. Practical experiments with two different robotic arms are performed. Experimental results show that the proposed modeling and control scheme provides a flexible and effective approach for an aerial manipulator with a replaceable robotic arm.

For aerial manipulators, a steady flight must be guaranteed to perform safe interaction with the surrounding environment. This paper focuses on the development of a position control algorithm for an aerial manipulator system (AMS). The position control algorithm is based on the Immersion and Invariance (I&I) theory. The proposed controller maintains the position of the aerial manipulator at the desired point under external and internal disturbances. The control architecture uses a Visual-SLAM technique using on-board sensors for AMS positioning. A series of outdoor experimental tests are performed to demonstrate the effectiveness of the proposed control strategy.

In this paper, the distributed formation tracking control problem of quadrotor unmanned aerial vehicles is considered. Adaptive backstepping inherently accommodates model uncertainties and external disturbances, making it a robust choice for the dynamic and unpredictable environments in which unmanned aerial vehicles operate. This paper designs a formation flight control scheme for quadrotor unmanned aerial vehicles based on adaptive backstepping technology. The proposed control scheme is divided into two parts. For the position subsystem, a distributed robust formation tracking control scheme is developed to achieve formation flight of quadrotor unmanned aerial vehicles and track the desired flight trajectory. For the attitude subsystem, an adaptive disturbance rejection control scheme is proposed to achieve attitude stabilization during unmanned aerial vehicle flight under uncertain disturbances. Compared to existing results, the novelty of this paper lies in presenting a disturbance rejection flight control scheme for actual quadrotor unmanned aerial vehicle formations, without the need to know the model parameters of each unmanned aerial vehicle. Finally, a quadrotor unmanned aerial vehicle swarm system is used to verify the effectiveness of the proposed control scheme.

Rotorcrafts, with satisfactory maneuver performance and ability under complex terrains unreachable for ground robots, are playing important roles for goods transportation. In this article, we focus on the control of the cable-suspended transportation way due to its lower costs and more agility of the rotorcraft's rotational motion. Compared with traditional crane systems and single rotorcrafts without loads, the aerial transportation system presents "double" underactuated property, stronger system nonlinearity, and more complex dynamic coupling, which are huge challenges for control schemes design. Meanwhile, aerial transportation usually suffers from external disturbances and uncertainties presented with aerodynamic damping coefficients and rope length. Additionally, overshoots of the rotorcraft's position are potential threats for flight safety, especially in confined and complex environments. To address these problems, a novel adaptive control scheme is designed, which ensures effective rotorcraft positioning and payload swing suppression with restricted overshoot amplitudes. Asymptotic results are obtained with rigorous theoretical derivations provided by the Lyapunov-based stability analysis and LaSalle's invariance theorem. Real-time experiments are performed to validate the effectiveness of the proposed control scheme even in the presence of external disturbances. To the best of our knowledge, this is the first method designed for aerial transportation systems which achieves simultaneous rotorcraft positioning and swing suppression, together with insurance for overshoot restriction even in the presence of parametric uncertainties.

A new nonlinear disturbance observer-based tracking control scheme for an underwater manipulator is presented in this paper. This observer overcomes the disadvantages of existing disturbance observers, which are designed or analyzed by the linear system techniques. It can be applied in underwater manipulator systems for various purposes such as payload compensation, interaction effects compensation, underwater current or external disturbance compensation, and independent system control. The performance of the proposed tracking control scheme is demonstrated numerically by the payload compensation and interaction effects compensation for a two degrees of freedom vertical underwater manipulator.

Expanding an unmanned aerial vehicle (UAV) with an equipped robotic arm increases the ability of the UAV to actively interact with the environment. During the process of active tasks, precise motion control under model uncertainties and external disturbances is a challenging issue. To solve this issue, an active modeling based control scheme is proposed in this paper. In this scheme, the aerial manipulator system (AMS) is modeled with consideration of various uncertainties represented by the model error and the process noise. The model error caused by the gravity and movement of the manipulator is estimated by the unscented kalman filter (UKF). The estimation is further integrated into a nominal controller to achieve high-precision motion control. Detailed experimental results on the self-bulit testbed illustrate the effectiveness and good performance of the proposed method.

As a complex system, control performance of small rotary-wing unmanned aircraft is easily affected by measurement errors and environment disturbances. This paper proposes a nonlinear disturbance observer-based control to improve control performance. The constant and harmonic disturbance that is generated by the exogenous system with modeling perturbation can be estimated and rejected effectively. The random disturbance with certain bound can be reduced by the feedback control. By solving linear matrix inequality, the parameters for feedback control and nonlinear disturbance observer can be selected simultaneously. Therefore, the system stability can be guaranteed and the control performance can be improved effectively. The effectiveness of the nonlinear disturbance observer-based control is proved by a series of flight tests. Compared with feedback control, the disturbance observer-based control yields a better tracking performance in the presence of disturbances.

Due to the increasing development of distribution networks, the need to use clean energy resources, and the existence of different single-phase and three-phase consumers, the maximum use of both single-phase and three-phase distributed generation (DG) units has become crucial. However, the presence of DG units in microgrids (MGs) requires efficient control strategies, for power control and voltage regulation, to achieve a rapid and proper dynamic response with respect to external disturbances and uncertainties. In this paper, in order to improve the dynamic and steady-state performance of an unbalanced multibus microgrid including inverter-based single-phase DGs, a robust control strategy is proposed for controlling the active and reactive power of DGs. The proposed control scheme is composed of a current controller based on an adaptive sliding mode control method in a virtual synchronous dq reference frame, to control the single-phase inverter output current, and a PI controller to regulate the voltage magnitude of the generation buses connected to DGs. In the proposed control structure, each single-phase inverter is controlled as a virtual balanced three-phase inverter, based on the dynamic phasor concept that makes decoupled control of the active and reactive powers of single-phase inverters possible. In order to evaluate the validity and effectiveness of the presented control structure, a multibus single-phase MG containing several inverter-based single-phase DG units has been simulated in MATLAB software environment, and the performance of the proposed control scheme has been investigated for various scenarios of parametric uncertainties and external disturbances.

Suppression of chaotic behavior in horizontal platform systems based on an adaptive sliding mode control scheme

Force/position control with bounded actions on a dexterous robotic hand with two-degree-of-freedom fingers

A dual adaptive fault-tolerant control for a quadrotor helicopter against actuator faults and model uncertainties without overestimation

Fast and accurate positioning of Inlet Guide Vane (IGV) is critical for flow regulation in centrifugal air compressors, especially for surge avoidance control. Both transport delay and external disturbance are present for IGV position control on a compressed air system. A Smith Predictor based control scheme with the process-model modification is applied to this problem. The adopted control scheme can both compensate for the time delay and effectively reject step disturbances present in the IGV system. Simulation was conducted using simple PI controller and a PI controller with the Smith Predictor with process-model modification. It showed that the proposed control scheme can achieve zero steady-state error with the presence of external disturbance and the settling time was shortened. Robust stability and performance of the system was discussed.

This paper presents a motion coordination of a two-cooperating robot arm when there are unknown system parameters and bounded input disturbances. The order of the model of the two-arm system is reduced. To control this, a force/position control scheme based on an inverse dynamics control scheme is devised. On the top of the control scheme, an adaptive control scheme to take care of parametric uncertainties, and a robust control scheme to compensate coupling forces between two arms and input disturbances are devised. The adaptive and the robust control scheme are derived based on a devised Lyapunov function. The adaptive control algorithm is practical since it does not require the feedback of the second derivative of joint angles and interacting forces. The robust control scheme guarantees that the tracking error of the leader arm and the interacting forces between two arms are confined in a certain region. Numerical examples using dual 3 degree of freedom robot arm are shown.