Terminal sliding mode control for coordinated motion of a space rigid manipulator with external disturbance

The control problem of coordinated motion of a free-floating space rigid manipulator with external disturbance is discussed. By combining linear momentum conversion and the Lagrangian approach, the full-control dynamic equation and the Jacobian relation of a free-floating space rigid manipulator are established and then inverted to the state equation for control design. Based on the terminal sliding mode control （SMC） technique, a mathematical expression of the terminal sliding surface is proposed. The terminal SMC scheme is then developed for coordinated motion between the base＇s attitude and the end-effector of the free-floating space manipulator with external disturbance. This proposed control scheme not only guarantees the existence of the sliding phase of the closed-loop system, but also ensures that the output tracking error converges to zero in finite time. In addition, because the initial system state is always at the terminal sliding surface, the control scheme can eliminate reaching phase of the SMC and guarantee global robustness and stability of the closed-loop system. A planar free-floating space rigid manipulator is simulated to verify the feasibility of the proposed control scheme.

Adaptive neural network control for coordinated motion of a dual-arm space robot system with uncertain parameters

Control of coordinated motion between the base attitude and the arm joints of a free-floating dual-arm space robot with uncertain parameters is discussed. By combining the relation of system linear momentum conversation with the Lagrangian approach, the dynamic equation of a robot is established. Based on the above results, the free-floating dual-arm space robot system is modeled with RBF neural networks, the GL matrix and its product operator. With all uncertain inertial system parameters, an adaptive RBF neural network control scheme is developed for coordinated motion between the base attitude and the arm joints. The proposed scheme does not need linear parameterization of the dynamic equation of the system and any accurate prior-knowledge of the actual inertial parameters. Also it does not need to train the neural network offline so that it would present real-time and online applications. A planar free-floating dual-arm space robot is simulated to show feasibility of the proposed scheme.

Coordinated motion of molecular motors on DNA chains with branch topology

Toward understanding the macroscopic mechanical behaviors of responsive deoxyribonucleic acid(DNA)hydrogels integrated with DNA motors,here we construct the state map for the translocation process of a single C-terminal translocase domain(FtsKC)on a single DNA chain at the molecular level and then investigate the movement of single or multiple FtsKC motors on DNA chains with varied branch topology.Our studies indicate that multiple FtsKC motors can have coordinated motion,which is mainly due to the force responsive behavior of individual FtsKC motor.We further suggest the potential application of motors of FtsKC,together with DNA chains of specific branch topology,to serve as strain sensors in hydrogels.

Coordinated motion of molecular motors on DNA chains with branch topology

To understand the macroscopic mechanical behaviors of responsive DNA hydrogels integrated with DNA motors,we constructed a state map for the translocation process of a single FtsKc on a single DNA chain at the molecular level and then investigated the movement of single or multiple FtsKc motors on DNA chains with varied branch topologies.Our studies indicate that multiple.FtsKc motors can have coordinated motion,which is mainly due to the force-responsive behavior of individual FtsKc motors.We further suggest the potential application of motors of FtsKc,together with DNA chains of specific branch topology,to serve as strain sensors in hydrogels.

Improvement of Computation Method of Fault Motion Coordination Ratio and Analysis of Earthquake Cases

According to the concept of the fault motion coordination ratio( FCR),this paper discusses the effect of the starting point on the result of FCR calculation and puts forward the calculation method for FCR using the sliding window and the index for evaluating the dispersion. Earthquake cases analysis shows that at the Lijiang site across the fault: the FCR value varied greatly and its distribution was dispersive before the MS7. 0 Lijiang earthquake,while the value was stable and less dispersive after the earthquake,which reflects the strain accumulation of the fault during the seismogenic process and the poor movement coordination between the motion of the three components. After the earthquake,the fault was in a free activity state,the accumulated strain energy released, and the movement of the three components was coordinated mutually. At present,FCR dispersion of Lijiang is at a low value,and fault strain accumulation is at a low level.

Dynamic modeling and simulation for the flexible spacecraft with dynamic stiffening

A rigid flexible coupling physical model which can represent a flexible spacecraft is investigated in this paper. By applying the mechanics theory in a non-inertial coordinate system,the rigid flexible coupling dynamic model with dynamic stiffening is established via the subsystemmodeling framework. It is clearly elucidated for the first time that,dynamic stiffening is produced by the coupling effect of the centrifugal inertial load distributed on the beamand the transverse vibration deformation of the beam. The modeling approach in this paper successfully avoids problems which are caused by other popular modeling methods nowadays： the derivation process is too complex by using only one dynamic principle; a clearly theoretical explanation for dynamic stiffening can＇t be provided. First,the continuous dynamic models of the flexible beamand the central rigid body are established via structural dynamics and angular momentumtheory respectively. Then,based on the conclusions of orthogonalization about the normal constrained modes,the finite dimensional dynamic model suitable for controller design is obtained. The numerical simulation validations showthat： dynamic stiffening is successfully incorporated into the dynamic characteristics of the first-order model established in this paper,which can indicate the dynamic responses of the rigid flexible coupling system with large overall motion accurately,and has a clear modeling mechanism,concise expressions and a good convergence.

A novel motion coordination method for variable-sized multi-mobile robots

Multi-mobile robot systems(MMRSs)are widely used for transportation in industrial scenes such as manufacturing and warehousing.In an MMRS,motion coordination is important as collisions and deadlocks may lead to losses or system stagnation.However,in some scenarios,robot sizes are different when loaded and unloaded,which means that the robots are variable-sized,making motion coordination more difficult.The methods based on zone control need to first divide the environment into disjoint zones,and then allocate the zones statically or dynamically for motion coordination.The zone-control-based methods are not accurate enough for variable-sized multi-mobile robots and reduce the efficiency of the system.This paper describes a motion coordination method based on glued nodes,which can dynamically avoid collisions and deadlocks according to the roadmap structure and the real-time paths of robots.Dynamic features make this method directly applicable to various scenarios,instead of dividing a roadmap into disjoint zones.The proposed method has been applied to many industrial projects,and this study is based on some manufacturing projects for experiments.Theoretical analysis and experimental results show that the proposed algorithm is effective and efficient.

Motion Coordination for a Class of Multi-Agents via Networked Predictive Control

The motion coordination formation control problem for a class of non-linear system is considered in this paper,where networked induced time-delays exist in the feedback channel of each agent and in communication channels between agents.As a foundation work,a coordination formation controller in discrete-time domain that without time-delay is provided firstly.Based on the above results,a motion coordination predictive formation control strategy as well as its detail implementation processes are proposed to actively compensate the time-delays.Stability analysis and simulation results are provided to demonstrate the feasibility and effectiveness of the proposed predictive strategy.

Three-dimensional analysis of relationship between relative orientation and motion modes

Target motion modes have a close relationship with the relative orientation of missile-totarget in three-dimensional highly maneuvering target interception. From the perspective of relationship between the sensor coordinate system and the target body coordinate system, a basic model of sensor is stated and the definition of relative angular velocity between the two coordinate systems is introduced firstly. Then, the three-dimensional analytic expressions of relative angular velocity for different motion modes are derived and simplified by analyzing the influences of target centroid motion, rotation around centroid and relative motion. Finally, the relationships of the relative angular velocity directions and values with motion modes are discussed. Simulation results validate the rationality of the theoretical analysis. It is demonstrated that there are significant differences of the relative orientation in different motion modes which include luxuriant information about motion modes. The conclusions are significant for the research of motion mode identification,maneuver detection, maneuvering target tracking and interception using target signatures.

Coordinate difference homogenization matching method for motion correction in 3D range-intensity correlation laser imaging

This Letter proposes a coordinate difference homogenization matching method to solve motion influence in three-dimensional（3D） range-intensity correlation laser imaging. Firstly, features and feature pairs of gate images are obtained by speeded-up robust figures and bi-directional feature matching methods. The original mean value of the feature-pair coordinate differences is calculated. Comparing the coordinate differences with the original mean value, the wrong feature pairs are removed, and then an optimized mean value is updated. The final feature-pair coordinates are re-registered based on the updated mean value. Thus, an accurate transformation is established to rectify motion gate images for 3D reconstruction. In the experiment, a 3D image of a tower at 780 m is successfully captured by our laser gated imaging system on a pan-tilt device.