Xiaoyu Zhao

Bio: Xiaoyu Zhao is an academic researcher from Harbin Institute of Technology. The author has contributed to research in topics: Robot & Trajectory. The author has an hindex of 4, co-authored 13 publications receiving 55 citations.

Capture tolerance capacity testing system and method of three-jaw type space end effector in microgravity environment

Abstract: The invention discloses a capture tolerance capacity testing system and method of a three-jaw type space end effector in a microgravity environment, and relates to a target interface capture tolerance capacity testing system and method of a three-jaw type space manipulator end effector in the microgravity environment. The problems that an existing microgravity platform verification system is complex, poor in safety and reliability and not capable of achieving six-degree-of-freedom motion of a mechanical arm or a spacecraft in the three-dimensional space of the microgravity environment can be solved. The capture tolerance capacity testing system comprises a capture subsystem, a target subsystem and a measurement subsystem. The capture tolerance capacity testing method includes the steps that first, the capture tolerance capacity testing system is mounted; second, the original position and the coordinate axis of a coordinate system of the space end effector are determined; third, the pose of the three-jaw type space end effector is determined; fourth, the pose of a target to be captured is determined; fifth, the pose deviation of the target to be captured relative to the space end effector is acquired; sixth, a capture test is carried out under different pose deviations. The capture tolerance capacity testing system and method of the three-jaw type space end effector in the microgravity environment belong to the field of space robots or spacecraft ground verification systems.

Device and method for simulating space mechanical arm to capture ground three-dimensional space microgravity of target satellite

Abstract: The invention provides a device and method for simulating a space mechanical arm to capture ground three-dimensional space microgravity of a target satellite, and relates to a device and method of the ground three-dimensional space microgravity. The problem that the movement of a floating satellite base in the three-dimensional space and operation process of the space mechanical arm is not considered is solved. The device comprises two industrial mechanical arms, the space mechanical arm, a hand eye camera, a capturing paw, a capturing connector, a service satellite body simulator, a target satellite body simulator and six-dimensional force and torque sensors; the method comprises the steps that target satellite movement is simulated; the position and attitude of the target satellite and movement information of joints of the space mechanical arm are determined; movement information of a service satellite body simulator base and the industrial mechanism arms is calculated; the capturing connector captures the target satellite body simulator in a capturing paw area; a movement state of the service satellite body simulator is achieved by simulating a real target satellite movement sate. The device and method for simulating the space mechanical arm to capture the ground three-dimensional space microgravity of the target satellite is applied to the field of space mechanical arm ground three-dimensional space microgravity simulation.

Development of ground experiment system for space end-effector capturing the floating target in 3-dimensional space

Abstract: Purpose – The purpose of this paper is to develop a set of ground experiment system to verify the basic functions of space effector and the capturing reliability of space end-effector for the free-floating target payload in the three-dimensional space. The development of ground experiment system for space end-effector is essential and significant, because it costs too much to launch a space robot or other spacecraft and carry out operation tasks in space. Owing to the negligible gravity in space, which is different from that in the ground environment, ground experiment system for space end-effector should have the capability of verifying the basic functions of space effector and the reliability of space end-effector in capturing the free-floating target payload in space. Design/methodology/approach – The ground experiment system for space end-effector mainly adopts the hybrid simulation method, which includes the real hardware experiment and software simulation. To emulate the micro-gravity environment, t...

Minimum Base Disturbance Control of Free-Floating Space Robot during Visual Servoing Pre-capturing Process

Abstract: During visual servoing space activities, the attitude of free-floating space robot may be disturbed due to dynamics coupling between the satellite base and the manipulator. And the disturbance may cause communication interruption between space robot and control center on earth. However, it often happens that the redundancy of manipulator is not enough to fully eliminate this disturbance. In this paper, a method named off-line optimizing visual servoing algorithm is innovatively proposed to minimize the base disturbance during the visual servoing process where the degrees-of-freedom of the manipulator is not enough for a zero-reaction control. Based on the characteristic of visual servoing process and the robot system modeling, the optimal control method is applied to achieve the optimization, and a pose planning method is presented to achieve a second-order continuity of quaternion getting rid of the interruption caused by ambiguity. Then simulations are carried out to verify the method, and the results show that the robot is controlled with optimized results during visual servoing process and the joint trajectories are smooth.

A new approach for the estimation of non-cooperative satellites based on circular feature extraction

Abstract: Pose estimation of non-cooperative satellites has been a hot topic in the study of astronautics as the visual feedback will highly enhance the safety of on-orbit services. A stereo vision system is proposed in this paper. It works as an eye-to-hand vision camera in the final approach phase Based on circular feature extraction, a closed-form solution is presented. The position and orientation of the adapter ring can be figured out in real-time as well as the unknown radius. Neither additional sensors nor prior knowledge is required, and the orientation-duality problem has been solved. It works well on the partial ellipses and is robust to outliers, noise and occlusions. Experimental results on both synthetic and real images have demonstrated the effectiveness and efficiency of the proposed method.

A High-Gain Transmitarray for Generating Dual-Mode OAM Beams

Abstract: This paper proposes a novel transmitarray antenna which can achieve high gain and produce dual-mode orbital angular momentum (OAM) beams in Ku -band. Two back-to-back wideband dual-polarized microstrip antennas are employed as the unit cells, which are connected using metalized via holes. Full 360° phase ranges can be obtained by varying the length of feeding lines in two orthogonal polarizations. Due to high isolation between the two orthogonal polarizations, dual-mode OAM beams can be formed simultaneously by tuning phase distributions in x- and y-polarizations, respectively. The approach for generating OAM beams is explained. To verify this concept, one prototype carrying 0 and +1 mode OAM beams is designed, fabricated, and measured. Experimental results demonstrate that both 0 and +1 mode OAM beams can be generated successfully, and the measured results agree well with the simulated results. Because of high directivity and focusing effects of transmitarray, the proposed +1 mode OAM beam has stable performance at a long propagation distance. The maximum gain reaches 26 and 20 dBi in 0 and +1 mode OAM beams, respectively. Meanwhile, a narrow divergence angle of ±5° is obtained in +1 mode OAM beam. Compared with other OAM antennas reported, main advantages of the proposed antenna include high gain, narrow divergence angle, low cost, planar structure, and the capability of producing dual-mode OAM beams.

Force control traction and swinging multi-degree-of-freedom mechanical arm control device and method

Abstract: The invention discloses a force control traction and swinging multi-degree-of-freedom mechanical arm control device and method. A force signal sensor is mounted on a flange plate at the tail end of a mechanical arm in a specific mode by a mounting connector, and the pose information and force/moment information of the tail end of the mechanical arm are sampled synchronously. Based on feedback control of external action force, force feedback information is converted into pose offset information of the tail end of the mechanical arm. The pose and speed of the tail end of the mechanical arm are changed along with the external action force through a force-pose offset control algorithm and a force-speed control algorithm, and accurate swinging can be achieved when manual traction is stopped. According to the force control traction and swinging multi-degree-of-freedom mechanical arm control device and method, a tail end tool can achieve traction operation conveniently in real time according to the will of an operator, the current pose can be kept without external force action, and accurate positioning is achieved; meanwhile, the operator can change the motion trail of the tail end of the mechanical arm by exerting external force in the process that the mechanical arm moves to a target spot, and the mechanical arm can achieve emergent obstacle avoidance in the movement process.

Robust Impedance-Matching of Manipulators Interacting With Uncertain Environments: Application to Task Verification of the Space Station's Dexterous Manipulator

Abstract: A systematic design method is developed for the identification and control of a simulating robot in order to adjust its contact force and impact dynamics to match those of a reference robot when both robots couple to a similar physical environment with unknown impedance. The control architecture, which is based on closed-loop impedance matching between two robots, is utilized by a hydraulic robot testbed facility for high-fidelity task verification of the space station's dexterous manipulator without requiring contact dynamics modeling. First, the uncertain environment is modeled in terms of parameter uncertainty bounds for a class of environment impedances. Then, the control goal is specifically defined as to minimize the contact-force error between the two robots, where the contact force is caused either by time-varying operator commands or impacts due to a nonzero preimpact velocity. Next, a hierarchical control architecture is formulated in the general framework of linear fractional transformation system by making use of the frequency-domain specifications of the robots together with the environment's parameter uncertainty bounds. It is shown that the overall system uncertainty can be represented by a perturbation block in the feedback form, which can be specified by a block structure array by making use of a unitary transformation. Subsequently, a $\mu$ -synthesis-based controller is developed and implemented to achieve the dynamical similarity while maintaining contact stability. Experimental results demonstrate that the simulating robot can generate high-fidelity contact-force profile and impulsive force for different environments without contact dynamics modeling.

A review on the interfaces of orbital replacement unit: Great efforts for modular spacecraft:

Abstract: Over the past decades, the development of single spacecraft for outer space exploration requires more complicated design and higher investment. From the modular design ideas of the International Sp...