Aiming at on-orbit automatic assembly, an improved uncalibrated visual servo strategy for hyper-redundant manipulators based on projective homography is proposed. This strategy uses an improved homography-based task function with lower dimensions while maintaining its robustness to image defects and noise. This not only improves the real-time performance but also makes the joint space of hyper-redundant manipulator redundant to the homography-based task function. Considering that the kinematic parameters of the manipulator are easily changed in a space environment, the total Jacobian between the task function and manipulator joints is estimated online and used to construct a controller to directly control the manipulator joints without a kinematics model. When designing the controller, the above-mentioned redundancy is exploited to solve the problem of the over-limiting of the joint angles of the manipulator. The KF-SVSF method, which combines the optimality of the Kalman filter (KF) and the robustness of the smooth variable structure filter (SVSF), is introduced to the field of uncalibrated visual servos for the first time to perform the online estimation of the total Jacobian. In addition, the singular value filtering (SVF) method is adopted for the first time to avoid the interference caused by the unstable condition number of the estimated total Jacobian. Finally, simulations and experiments verify the superiority of this strategy in terms of its real-time performance and precision.

Position controllers are used for free motion, whereas force controllers are used for constrained motion of robotic manipulators. The hybrid controller switches between position and force control modes depending on whether the manipulator is in contact with the environment. To improve production efficiency, the velocity of contact between the manipulator and environment is not set to zero. However, the high impact force due to the nonzero contact velocity might damage the environment surface or manipulators. In this article, we propose a virtual semi-active damping learning method to suppress force overshoot without decreasing the contact velocity. Virtual semi-active damping is adjusted according to the manipulator position in force control. The limited-memory BFGS method is used to obtain the ideal impedance model for the unknown environment. By minimizing the defined cost function, we get the desired interaction performance. The correctness and effectiveness of the proposed method are verified by conducting simulations and experiments.

In dual-frequency heterodyne structured-light 3D measurement, fringe-order misjudgment often occurs near object edges, hole boundaries, and local low-reliability regions, which may further lead to absolute phase jumps and abnormal 3D reconstruction results. To address this problem, this paper proposes a phase-unwrapping method based on region-of-interest (ROI) constraint, coarse estimation using the synthetic wrapped phase, dual-frequency consistency residual optimization, and local spatial regularization. The method first automatically extracts the target ROI using a binary mask, thereby excluding invalid background regions and reducing unnecessary computation. A synthetic wrapped phase is then constructed from the two wrapped phases, and a coarse absolute phase is obtained using the long synthetic period. The initial fringe order is estimated by rounding rather than the conventional floor operation, reducing systematic fringe-order misjudgment near integer boundaries. On this basis, a dual-frequency consistency residual is constructed to perform local candidate search and reliability evaluation. Reliable-anchor constraints and local spatial regularization are subsequently introduced to correct abnormal fringe orders in low-reliability regions and suppress error propagation near edges and holes. Experimental results on objects with complex boundaries show that the proposed method effectively suppresses phase jumps and improves the continuity of the unwrapped phase and reconstructed point cloud. Accuracy verification using a three-layer step block showed mean height errors of 0.0230, 0.0320, and 0.0370 mm for the three layers, respectively, with corresponding standard deviations of 0.00852, 0.00880, and 0.00963 mm, all below 0.01 mm. These results demonstrate that the proposed method can effectively suppress fringe-order-induced phase jumps while maintaining high accuracy and stability in structured-light 3D reconstruction.