Road depth estimation plays a crucial role in vehicle chassis control and autonomous driving. Monocular depth estimation, due to its low cost, energy efficiency, and ease of deployment, remains an important area for research. However, challenges persist in improving the accuracy of monocular depth estimation, reducing the impact of errors, and ensuring the convergence of errors over long-term operation. This paper proposes an improved monocular depth estimation approach that integrates deep learning techniques with feedback from vehicle suspension states. Under the DispNet architecture, we replace traditional neural networks with the Standard Nonlinear Operator Form (SNOF) and incorporate vehicle suspension information to build a delayed state observer for real-time depth estimation error compensation. State compensation is achieved through solving Linear Matrix Inequalities (LMI), ensuring error convergence during extended operation. Extensive real-world experiments using signal-collecting vehicles demonstrate that the proposed method exhibits excellent generalization capabilities across diverse environments and lighting conditions.

In this work, the brightness temperature (TB) transfer from the microwave calibration target (MCT) to the feeder antenna in the near-field region is investigated, which is the fundamental physical process in microwave radiometer calibration. As in this scenario, the MCT and antenna cannot be separately considered as points like in far fields, it is interesting and important to study the TB characteristics of the target in cases of feeder antennas at different positions and with different aperture sizes. Recently, as reciprocity in the near field has been established, this fundamental issue can be now investigated. The study starts at a high frequency of 89 GHz when the free-space lambda is much smaller than the unit period of MCT; then, the distributions of the local TB contribution rate are calculated to understand the possible TB transfer variation. It is found that the key factor for the TB variation is the illumination area upon the array-type MCT, and as the footprint is sufficiently large to cover several pyramid units, the TB can be stable versus relative position.

In this work, an interesting phenomenon is investigated in the scenario of calibration link in microwave radiometers, where a feeder antenna is directly harvesting the radiated brightness temperature (BT) from the microwave calibration target (MCT). As reciprocity has been established for the near-field BT transfer, it is important to investigate the performance variation of the MCT in case of different antenna illumination. In this work, it is found and analyzed that at the frequencies where lambda is near to the unit period of periodic array-shaped calibration target, the reflectivity may be notably increased in case of small aperture feeder illumination. This is a disturbing phenomenon that should be avoided for practical applications.

Autonomous vehicles (AVs) equipped with an array of advanced sensors gather road preview information, presenting new opportunities to enhance ride comfort. To simultaneously improve both the vertical and longitudinal ride comfort of vehicles, a dual timescale model predictive control (MPC) preview active suspension system (ASS) and longitudinal dynamics coupled controller is developed. On a short time scale, the coupling control of the vehicle’s ASS and longitudinal acceleration is achieved using road preview information, enhancing both vertical and longitudinal ride comfort, thereby improving response speed. On a longer time scale, road prediction information obtained via Gaussian processes (GPs) is utilized for vehicle speed planning, aiming to mitigate vertical excitations caused by road profile variations while minimizing frequent speed changes. However, when road preview information is continuously used as disturbance predictions in MPC, it undermines the recursive feasibility and stability of MPC. To address this, a scaling method is devised to account for disturbances incorporated into the predictive model. Theoretical foundations ensure both recursive feasibility and asymptotic stability. The effectiveness and advantages of the dual timescale MPC preview active suspension and longitudinal dynamics coupled control are validated through simulations and bench tests.

Point-in-spherical-polygon tests are a fundamental problem in computational geometry.For such tests, efficiency is much required for many global information processing matters, especially their real-time processing.Though many efforts have been made, it is still challenging due to the constraints from the non-Euclidean space of the sphere.Recently, a method is proposed to construct an Adaptive Hexagonal Hierarchical Grid (AHHG) to manage spherical polygon edges, by which the non-Euclidean space constraint of the sphere can be well handled to improve point-in-spherical-polygon tests.However, this method is very expensive in the construction of AHHGs, which prevents its use in practice.In this paper, we present novel measures to divide the task of AHHG construction into several subtasks to solve the problems that arise in the parallel construction of incongruent adaptive hierarchies, so we can exploit the parallel computing potential of GPUs for acceleration.We also develop measures to adaptively optimize the hierarchical levels of an AHHG for high efficiency.Experimental results show that we can answer 1,000,000 query points against dynamically varying spherical polygons in over 100,000 edges in real time on a personnel computer, where AHHGs for spherical polygons are individually constructed.This is much superior to the existing methods.

In ophthalmic surgery, realigning retinal field is a common practice to check the lesion area by rotating the eyeball. It can be a challenging task for teleoperated surgical robots as it requests high precision of hands coordination comparing with traditional surgery. Current ophthalmic surgical robots are mainly designed with one-to-one mapping mode, which requires surgeons to operate with two hands. This article proposes a single master and dual-slave control method to improve the coordination of slave robots. Firstly, motion constraints between slave arms are analyzed. To solve the motion equation of master-slave mapping, Gauss-Newton Iteration is implemented to achieve the real-time motion coordination. Secondly, an adaptive impedance control is adopted to ensure the contact force between end-effectors and sclera within the threshold, preventing the eyeball from stretching and compressing. Finally, the effectiveness and practicability of the proposed method are verified on the established ophthalmic surgical robot platform by fixed trajectory and free trajectory experiments.Note to Practitioners—This paper was motivated by the problem of dual-arm control in robot-assisted retinal surgery. Related previous studies mainly focus on the control of teleoperated surgical robots based on one-to-one mapping mode between the master and slave robots. However, to the limited coordination of human hands, the master robots may perform poor coordination so that one task is hard to be accomplished by salve robots at same time. Especially when the requirement of task is complex and operation is precise, the accuracy and safety may not be guaranteed by one-to-one mapping mode. To solve these problems, this article seeks to develop a single master and dual-slave control method to improve the coordination of slave robots. The proposed method can be integrated into eye surgical robot to help the surgeons perform surgery. Our method will significantly facilitate its practical applications in improvement of surgery safety and reduction of the operation burden and training cost of the surgeons.

In this letter, the recent progress in optimizing the microwave calibration target is reported. Based on the former findings on the wideband reflectivity of the target and the analysis model for the directionally radiated brightness temperature, the authors further investigate the comprehensive optimization in both the aspects of electromagnetic and thermal properties. Specifically, a design instance with a thinner coating at the tip and thicker coating at the bottom is concluded and optimized for stable wideband performance, without introducing further difficulties in manufacturing. The performance of the new design is compared to that of traditional uniform coating, in terms of total reflectivity, temperature gradient, and, finally, the brightness temperature toward the normal direction. Results show the comprehensively improved performance of the new design, which can be a good reference for practical applications.

In this work, the authors investigate the calibration target design for sub-millimeter wave radiometer applications, with specific focus on further improving the brightness temperature radiation accuracy during the miniaturization. The investigation is based on latest design of curved inner kernel for the frequently utilized periodic coated pyramidal target. The numerical study combines the electromagnetic and thermal analysis, then the overall brightness temperature performance can be investigated. Within the typical frequency range of 50-500GHz, results show that the target miniaturization can lead to clearly improved brightness temperature radiation accuracy, however, only in case that correct design strategy is applied. The key is that the coating thickness should be proportionally reduced during the miniaturization, so that the temperature gradient at tips can be notably relieved. On the contrary, keeping the coating thickness unchanged will result in the notable degradation of brightness temperature accuracy. The investigation also includes the important aspect of coating material, for comprehensively referencing for sub-millimeter wave radiometer applications.

Before practical usage in microwave radiometers, the calibration targets must be tested for its emissivity/total reflectivity. In this work, we address the issue that remains in the total reflectivity determination, which is estimating the total reflectivity based on measured backscattering in the monostatic configuration, specifically at high frequencies. Based on the efficient modeling on periodic unit of the array-shaped calibration target, we quantitatively evaluate the relationship between backscattering and the total reflectivity, on the common structure of coated cones and coated pyramids. It is found that the total reflectivity estimation becomes target-specific for the coated cones; meanwhile, stable compensation can be concluded for the pyramidal units, which is important for practical testing in submillimeter applications. Then, the disturbing effects of the geometric defects on the total reflectivity estimation are discussed, and it is inferred that wideband measurement is vital for diagnosing those defects. Furthermore, actual test results are analyzed, showing the complex scenario in estimating the total reflectivity of a prototype with shape defects. Also, the numerical concluded$C_{g}$compensation is verified in the clear case of a fine prototype. The findings in this work offer a direct reference for the application of microwave radiometer calibration, especially in the region of submillimeter waves.

We report the continuous effects in modeling sharp coated cones as calibration targets by surface integration solutions. The Coiflet based method of moment (MoM) is employed in conjunction with the thin dielectric sheet approximation (TDS). The Coifman wavelets inherit mathematical superiority in the Galerkin procedure, e.g., the high precision one-point quadrature for fast matrix filling, local multi-resolution ability, and high regularity with Hölder index 1.449 in smoothness. Local geometry refinements are implemented to reduce the errors by TDS approximation in modeling very sharp structures. The Coiflet-TDS solution is compared to an in-house FDTD package and good agreement has been observed. The presented MoM is also compared against the RWG-TDS based commercial software FEKO, and the Coiflet-TDS demonstrates more robust in modeling surfaces with sharp geometries. Finally, the emissivity of a calibrator is studied versus directions and polarizations, and its variation trends are observed.

The Microwave Radiation Imager (MWRI) on board the FengYun-3A/B satellites observes the Earth atmosphere at 10.65, 18.7, 23.8, 36.5, and 89.0 GHz with each having dual polarization. Its calibration system is uniquely designed with a main reflector viewing both cold and hot calibration targets. Two quasi-optical reflectors are used to reflect the radiation from the hot load and cold space to the main reflector. In the MWRI calibration process, a radiation loss in the beam transmission path must be taken into account. The loss factor in the hot load transmission path is derived using the antenna pattern data measured on ground and satellite data observing over the Amazon forest where the scene temperature is steady and close to the hot load. The instrument nonlinearity factors at different channels are also evaluated over a wide range of brightness temperatures and compared with the results from the ground vacuum test. After a cross-calibration with Windsat data, atmospheric products are derived from MWRI brightness temperatures with the accuracy similar to those from the legacy sensors (e.g., the Special Sensor Microwave/Imager).