Article

Coordinated Control of a Dual-Arm Space Robot: Novel Models and Simulations for Robotic Control Methods

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Abstract

Space robots have attracted increasing attention for performing, autonomously or telerobotically, on-orbit servicing missions such as repairing, refueling, and upgrading spacecraft; reusing space assets; and on-orbit assembly. The extension of robot application to space can release astronauts from risky, time-consuming, and expensive extravehicular activities [1]. However, in the microgravity environment, the floating base of a space robot will be disturbed by the robot's arm motion when it approaches or manipulates a target. The motion of the spacecraft base resulting from this disturbance will, conversely, affect the motion of end effectors (known as coupling dynamics), making control of space robots more complicated than that of fixed-base robots. In addition, such a disturbance of spacecraft attitude may result in a communication interruption between the spacecraft and the ground station or a failure of energy accumulation caused by disorientation of solar panels [2].

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... Basically, a space mission could be classified into four phases, which are: observation and plan, approach, capture and post-capture phases [20]. Typically, the control strategy could be utilised in the last three phase. ...
... Although there were a lot of beneficial outcomes about space robots, the accurate motion control of the dual-arm space manipulators in 3D space which aims to approach and capture non-cooperative objects like spinning defunct spacecraft presented in this paper is a novel contribution for future space technology. Firstly, most of the above work [10,20,29,33,38] analysed the performance of end-effectors in the 2D-plane. However, the 3D motion of the end-effectors are significantly more useful for actual space missions. ...
... End-effector 1 (1 ) Link 1 (1) Joint 1 (1) Link 2 (1) Link 3 (1) Joint 2 (1) Joint 3 (1) Link 1 (2) Link 2 (2) Link 3 (2) Base Figure 1: 3D model of a dual-arm space robots for pre-capture. [20,22,29]. On the contrary, the non-cooperative targets like the spinning object in Fig. 1 would not be prepared for the capture and some parameters like position and velocity only could be estimated by external devices like cameras on the space robot. ...
Article
The non-cooperative objects in space such as space debris and spinning defunct satellites have attracted significant attention because of the rapid development of space exploration. To approach and capture the spinning targets in 3D space, the dual-arm space robot could be more efficient and safer than single-arm space robot to carry out the complicated tasks for spinning targets. The paper extends the model of a dual-arm space robot with Reaction Wheels into 3D space, which is more realistic in practice. The desired trajectories for end-effectors of the space robot are designed to securely approach and prepare to capture the spinning object through synchronising with the grasp points, while at the same time the desired attitude of the base could be maintained. Then coordinated control of the base and end-effectors could be carried out by Nonlinear Model Predictive Controller (NMPC) and a state feedback controller called Direct Parametric Method (DPM) with the consideration of the uncertainties of the space robot system. NMPC has performed with a higher accuracy than DPM without the uncertainties of the space robot system. Considering the imperfect knowledge of the mass and inertia as the uncertainties, NMPC could hold the accuracy of tracking error at the same level of accuracy, but the DPM has showed the poor robustness and downgraded performance in the presence of uncertainties.
... Multiarm space robots can accomplish tasks in more dexterous ways, such as coordinated operation, parallel task, and target clamping [1]. Studies on multiarm FFSR are also being carried out these years, including capturing tool designs [19], capturing strategies during coordinate operations [20], and satellite-manipulator decoupling strategies of freeflying and free-floating robots [1,21]. To eliminate base disturbance with the decoupling strategy, the rapidly exploring random trees-based method was applied [22]. ...
... where is the time derivative of and can be determined by Eq. (19). ...
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... However, the application of novel CDRSM also brings challenges, including complex multiple-space kinematic mapping and coupling phenomena of cable-driven joints. Additionally, the dynamic coupling between the free-floating base and the manipulator can also interfere with the planning and control of the EE trajectory [12][13][14]. ...
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The cable-driven redundant space manipulator (CDRSM) has a wide range of potential applications in on-orbit servicing due to its light weight, low inertia, and intrinsic compliance. Especially for capturing and detumbling large-momentum tumbling targets in space, it requires agile approaching and synchronizing, compliant contact and dexterous post-capture manipulation. Due to the limited energy resources of the space robot, we propose a coordinated configuration and end-effector (EE) trajectory optimization method to minimize base disturbance, as well as maximize EE stiffness for guaranteeing the accuracy of post-capture manipulation. The dynamics coupling between the free-floating base and the CDRSM is derived, along with the kinematic modeling and stiffness analysis of the cable-driven joints. Considering the equiangular constraint relationship and the kinematic coupling characteristics of the cable-driven joints, the configuration of the CDRSM and the EE trajectory are parametrically represented using the arm angle and the rational Bézier curves, respectively. Further, based on these parameter variables, the particle swarm optimization and multiple-objective particle swarm optimization algorithms are used to minimize the base disturbance and maximize EE stiffness during post-capture manipulation. Finally, several simulation results demonstrate the effectiveness of the proposed method.
... The control system of a space mobile manipulator requires special attention as a freefloating mobile base, disturbance from the host spacecraft, and end-effector motion can affect the pose of the whole robot. A coordinated control system considering the attitude of the base robot and the motion of the dual arm manipulator system was investigated [104]. Alternatively, Dongming et al. discussed an impedance-based control system by designing the end-effector motion as a mass damper-spring system for target grabbing [105]. ...
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Inspection and repair interventions play vital roles in the asset management of railways. Autonomous mobile manipulators possess considerable potential to replace humans in many hazardous railway track maintenance tasks with high efficiency. This paper investigates the prospects of the use of mobile manipulators in track maintenance tasks. The current state of railway track inspection and repair technologies is initially reviewed, revealing that very few mobile manipulators are in the railways. Of note, the technologies are analytically scrutinized to ascertain advantages, unique capabilities, and potential use in the deployment of mobile manipulators for inspection and repair tasks across various industries. Most mobile manipulators in maintenance use ground robots, while other applications use aerial, underwater, or space robots. Power transmission lines, the nuclear industry, and space are the most extensive application areas. Clearly, the railways infrastructure managers can benefit from the adaptation of best practices from these diversified designs and their broad deployment, leading to enhanced human safety and optimized asset digitalization. A case study is presented to show the potential use of mobile manipulators in railway track maintenance tasks. Moreover, the benefits of the mobile manipulator are discussed based on previous research. Finally, challenges and requirements are reviewed to provide insights into future research.
... The generated contact forces/torques during the process of contact should be considered and controlled to fulfill a successful capture and avoid damaging the structural components [9,10]. Typically, for a FFSR to capture a target, four phases are included [11][12][13], namely observing and planning, approaching, capture, and post-capture stabilization phase. Restricted by space robot capabilities, the spinning targets should be first detumbled to a reasonable rotational rate (< 3 • ∕s) for performing the following operations, such as establishing rigid connection [14,15]. ...
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Force control provided by a small-scaled free-flying space robot on a floating or spinning target will be required for future on-orbit servicing missions, such as detumbling a target, performing an assembly or a maintenance operation. Regarding to different contact geometries for a space robot interacting with a spinning target, this paper addresses the contact model considering its multi-dimensional characteristics. A hybrid motion and force controller is developed to acquire desired contact forces and space robot configuration despite the floating feature of the system. On this basis, the control strategy to implement the operations of three typical phases, namely approaching phase, contact phase and post-contact phase, is proposed. The simulations have been performed to verify the control approaches and visualize the contact scenarios.
... Considering the dynamic couplings between manipulators, Jia et al. 23 utilized a linear parameterized dynamic equation to establish an adaptive control scheme for dual-arm space robots, which helps to avoid the effects of dynamic uncertainties. Abandoning the linearly parameterizing dynamic equations, Shi et al. 24,25 proposed a nonlinear model predictive controller and a SMC controller to improve the trajectory tracking performance of dual-arm space robots in the presence of system uncertainties. Besides, Cheng et al. 26 designed an extended state observer in control schemes for compensating the dynamic uncertainties of dual-arm space robots. ...
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Dual-arm space robots are capable of load transporting and coordinated manipulation for on-orbit servicing. However, achieving the accurate trajectory tracking performance is a big challenge for dual-arm robots, especially when mechanical system uncertainties exist. This paper proposes an adaptive control scheme for the dual-arm space robots with grasped targets to accurately follow trajectories while stabilizing base’s attitude in the presence of dynamic uncertainties, kinematic uncertainties and deadzone nonlinearities. An approximate Jacobian matrix is utilized to compensate the kinematic uncertainties, while a radial basis function neural network (RBFNN) with feature decomposition technique is employed to approximate the unknown dynamics. Besides, a smooth deadzone inverse is introduced to reduce the effects from deadzone nonlinearities. The adaption laws for the parameters of the approximate Jacobian matrix, RBFNN and the deadzone inverse are designed with the consideration of the finite-time convergence of trajectory tracking errors as well as the parameters estimation. The stability of the control scheme is validated by a defined Lyapunov function. Several simulations were conducted, and the simulation results verified the effectiveness of the proposed control scheme.
... In this work the base of the space robot was also controlled in addition to robot manipulators. More recently, a novel adaptive variable structure controller for a dual-arm space robot was applied [27]. This controller achieved higher tracking accuracy and saved more energy comparing to the smoothed quasi-continuous second-order sliding-mode controller. ...
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The design of variable-structure control (VSC) systems for a class of multivariable, nonlinear, time-varying systems is presented. Using the Utkin-Drazenovic method of equivalent control and generalized Lyapunov stability concepts, the VSC design is described in a unified manner. Complications that arise due to multiple inputs are examined, and several approaches useful in overcoming them are developed. Recent developments are investigated, as is the kinship of VSC and the deterministic approach to the control of uncertain systems. All points are illustrated by numerical examples. The recent literature on VSC applications is surveyed
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In this paper we discuss dynamic control of a free-flying space robot system where the base attitude is not controlled by thrust jets. Without external forces and moments, the system is governed by linear and angular momentum conser- vation laws. We first derive the system dynamic formulations in joint space and in inertia space, based on Lagrangian dynamics. Then we discuss the fact that dynamics of a space robot system can not be linearly parameterized, as opposed to the case of a fixed-based robot. Revealing this property is significant since the linearity of parameterization has been used as a prerequisite for various adaptive and nonlinear control schemes currently used in the robot control. Based on the dynamic model of the space robot system, a simple linear control scheme is pre- sented for the normal regulation problem for tasks in space, such as holding lights for illuminating objects or handing an astronaut tools in extra-vehicular activity. A globally stable dynamic control scheme is proposed for trajectory tracking ap- plications, such as catching moving objects or structure inspection for the space station. The dynamic control algorithm exhibits a fast and accurate motion re- sponse even when the mass/inertia ratio of the base with respect to the robot is low. The effectiveness of the proposed algorithms are demonstrated by simulation studies.