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The development of the spherical robot to meet the requirements of high-speed and high-precision tasks is of great importance. In this study, a fractional-order adaptive integral hierarchical sliding mode controller (F-AIHSMC) is proposed. F-AIHSMC enables the spherical robot to have better controlled performance when facing unknown disturbances and system chattering, which can seriously affect the high-speed and high-precision motion of the spherical robot. We establish the standard dynamic model of the spherical robot for high-speed linear motion first, and then use the feedforward compensation method to compensate the controllable influencing factors in the motion process. According to the standard dynamic model, the integral term and fractional calculus methods are integrated into the hierarchical sliding mode controller, and the adaptive method is used to evaluate and compensate unknown disturbances in the high-speed motion process. In order to verify the efficiency of the proposed F-AIHSMC, we test its control effect using the BYQ-GS spherical robot. The experimental results demonstrate that, compared with the classical hierarchical sliding mode controller and the adaptive hierarchical sliding mode controller, the F-AIHSMC has obvious advantages in response speed, convergence speed, stability and robustness when being applied to the control of high-speed linear motion of spherical robot. Moreover, the advantages of its control performance are more highlighted with the increase of the speed of the spherical robot. INDEX TERMS Adaptive control, fractional calculus, hierarchical sliding mode control, high-speed motion control, spherical robot.

Aiming at the recognition and location of noncooperative spacecraft, this paper presents a monocular vision pose measurement method based on solar triangle structure. First of all, an autonomous recognition algorithm of feature structure based on sliding window Hough transformation (SWHT) and inscribed circle of a triangle is proposed, and the image coordinates of feature points on the triangle can be obtained relying on this algorithm, combined with the P4P algorithm and the structure of spacecraft, calculating the relative pose of target expressed by rotation and translation matrix. The whole algorithm can be loaded into the prewritten onboard program, which will get the autocomplete feature structure extraction and relative pose measurement without human intervention, and this method does not need to mount any markers on the target. Then compare the measured values with the accurate value of the laser tracker, so that a conclusion can be drawn that the maximum position error is lower than 5% and the rotation error is lower than 4%, which meets the requirements of noncooperative spacecraft’s pose measurement for observations, tracking, and docking in the final rendezvous phase.

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Due to the confined intraocular space and physical constraints in tool manipulation, snake-like robots have a significant potential for use in retinal microsurgery. By enhancing the dexterity at the tool tip, not only the operable space on the retina can be enlarged, but also the delicate target tissues can be reached at an optimal angle minimizing the damage and making the operation much easier. In this study, we present an improved version of our earlier integrated intraocular snake (IRIS) robot, and combine it with another robotic assistant: the cooperatively controlled Steady-Hand Eye Robot (SHER). SHER is used to drive IRIS close to the retina with precision, while IRIS makes omnidirectional bends by combining its yaw and pitch motions and provides a significantly enhanced intraocular dexterity while holding the sclerotomy port fixed. For precise control of IRIS, its snake-like tip actuation has been characterized through experiments considering both a free tool tip and external loading at the tool tip. The workspace analysis showed ±45° yaw and pitch with excellent repeatability (±1°) despite the highly miniaturized articulated segment length (3 mm) and very thin shaft (Ø 0.9 mm). Our preliminary experiments in an artificial eye model have shown feasibility in reaching targets requiring bends up to 55° accurately.