Abstracts:Soft robots have demonstrated significant potential in numerous fields due to their inherent compliance; however, the soft nature of their actuators poses challenges for applications requiring load-carrying capacity, and their mechanical properties are nonadjustable postfabrication. Drawing inspiration from the mechanical programmability of metamaterials, we propose a new hybrid fiber-reinforced actuator (HFRA) by incorporating a metamaterial-inspired skeleton into the fiber-reinforced actuator (FRA). By utilizing the V-beam unit, the skeleton maintains the same deformation tendency as the FRA while allowing for adjustable mechanical properties through programming its thickness. Experimental results indicate that this skeleton not only transforms the nonlinear force–displacement relationship of the FRA into linearity and adjusts its linear range of force–pressure characteristics, but also enhances both axial and lateral stiffness of the HFRA. To demonstrate these capabilities, we fabricate a soft wrist-gripper system employing our HFRA technology, showcasing omnidirectional elongation and bending capabilities of the wrist along with versatile grasping and manipulation abilities across various object orientations. We believe that integrating metamaterials with soft robots could establish a new paradigm for designing, actuating, and enhancing functionality in next-generation soft robots.

Abstracts:A weight-unbalanced $k$-winner-take-all (WU-$k$WTA) network with finite-time convergence is constructed, analyzed, and applied to undirected and directed multirobot systems with unbalanced weights of communication topology. The convergent time of the finite-time $k$WTA network is theoretically derived with theorems proof. Furthermore, comparisons are conducted among the proposed WU-$k$WTA network and other existing $k$WTA works, and results reveal that the proposed network has high precision when encountering undirected or directed weight-unbalanced topologies. Additionally, a dynamic target tracking algorithm is established by employing the proposed WU-$k$WTA network, and its feasibility and efficiency are validated via simulations on a multirobot system and an experiment on the E-puck robot physical platform.

Abstracts:Energy efficiency is crucial in developing transtibial prostheses, encompassing two main aspects: amputee metabolic cost and prosthetic energy consumption. The parallel elastic structure is commonly used to enhance power efficiency, but usually with a fixed balanced angle. However, it can be demonstrated that the energy efficiencies in both aspects are related to this balanced angle when walking on different slopes. Therefore, we developed a powered transtibial prosthesis with adjustable parallel springs to change the equilibrium position. Slope adaptation strategies in both aspects are proposed based on theoretical and dataset analysis. The effectiveness is experimentally illustrated through multiple unilateral transtibial amputees walking on various slopes. The results demonstrate that the proposed prosthesis can effectively increase the peak torque, and substantially impact the energy consumption and the metabolic cost by adjusting the equilibrium position. We also confirm that the optimal positions in the metabolic cost and the prosthetic energy consumption are different in the same slope condition.

Abstracts:In multimanipulator systems (M$^{2}$Ss), one of the main challenges for the collaboration of manipulators is posed by the switching and weight-unbalanced topologies (SWUTs) due to the different communication power and unpredictable connection failures, which has not been investigated and can cause instability and performance degradation. In this article, following the distributed principle, the collaboration in M$^{2}$Ss with SWUTs is constructed for problems in the forms of optimization with a universal convex performance index and an inequality constraint for joint velocities, in which an algorithm for weight-unbalanced topologies to estimate their required left eigenvector is introduced, and a distributed formula with topology switching compensation is proposed as well. In the next step, a neural dynamics controller is employed to solve the aforementioned optimization problems, with its stability and convergence proved strictly. Afterwards, the efficacy of the proposed controller is validated through both simulations and physical experiments, and comparisons are provided to demonstrate its superiority in handling the abovementioned challenges in the distributed collaboration in M$^{2}$Ss with SWUTs.

Abstracts:Insertion of capillaries poses a great challenge to biomedical researchers owing to the demanding requirements of multi-DOF, large stroke, high resolution, and adjustable force. In this article, the output performance of a two-DOF inertial piezoelectric robotic insertion device (PRID) was studied and improved, and its application potential in vascular micropuncture was verified. First, configuration and working principle of the PRID were elaborated. Next, theoretical analyses were conducted to obtain the adjustable pretightening force range, thereby guiding the improvement of the puncture force characteristics. Then, a series of experiments were carried out to study its output characteristics. Eventually, a robotic micromanipulation system was proposed, and the capillary micropuncture tests were implemented. The experimental results indicated that the PRID achieved linear and rotary strokes of 36 mm and 360°, the puncture force range was from 16.85 mN to 154.26 mN; the coupling rates in linear and rotary directions separately were 4.04% and 3.21%, the displacement resolutions in linear and rotary directions separately were 6.5 nm and 0.6 μrad, and the exciting frequency could be used to actively adjust the puncture force. Furthermore, the PRID successfully completed the micropuncture of two sizes of silicone capillaries on the eyeball model in collaboration with a six-DOF piezoelectric platform. The PRID can be applied in the field of micropuncture of cells and blood vessels with different shapes and sizes.

Abstracts:In this article, we present the free-space dynamic modeling of a novel magnetic resonance imaging (MRI)-actuated robotic catheter. The MRI-actuated robotic catheter is modeled as a series of rigid and flexible segments, where the rigid segments are embedded with a set of current-carrying micro-coils. The robotic catheter is steered by controlling the currents passing through the actuators under the influence of the static magnetic field of the MRI-scanner. In this article, two discrete-time dynamic models of the MRI-actuated robotic catheter are presented and evaluated. The first model presented is a full-body Cosserat-rod-based dynamic model based on the dynamic Cosserat-rod theory, where the dynamic Cosserat-rod partial differential equations and the Euler–Lagrange equation are, respectively, used to derive the dynamic equations of the flexible segments and rigid segments. The second model presented is a hybrid Cosserat-rod-based dynamic model, where the dynamic equation of the rigid segments is derived using the Euler–Lagrange equation and the shape of the flexible segments is derived using the static Cosserat-rod theory. The proposed dynamic models are compared and experimentally validated using the 3-D positional trajectories collected from a catadioptric stereo tracking system.

Abstracts:Single-point matching algorithm (point mass filter or particle filter) only uses the current time measurement to calculate the likelihood, which is prone to pseudopeak and false peak. In order to solve the problem, this article introduces the sequence correlation analysis into the single point matching algorithm, and uses the sliding measurement sequence to estimate recursively. First, a position sequence estimation method based on trajectory reconstruction is proposed, which calculates the new position sequence by the relationship between INS displacement and heading angle, instead of the direct translation of INS trajectory method in traditional algorithms. After that, the likelihood of the candidate point is calculated by the correlation analysis method using the corresponding sliding measurement sequence at the current time, and a more accurate position estimation is obtained after the measurement update. Simulation and experiments show that the position sequence obtained by the proposed method based on trajectory reconstruction is more accurate than that obtained by the direct translation inertial navigation method. Compared with only using single time measurement information, the likelihood calculation method based on correlation analysis of sliding measurement sequence can significantly reduce pseudopeak and false peak, and the positioning accuracy of terrain matching is improved.

Abstracts:In this article, a three-dimensional hybrid thermal model (3D HTM) applied to the surface-mounted permanent magnet synchronous motor (SPMSM) is first presented. Starting from the x-y plane and the cross section along the z-axis direction of SPMSM, the thermal domain is subdivided, the general solution is derived, and the boundary condition is established. Next, the lumped parameter thermal network and the electromagnetic analytical model (EAM) based on the subdomain method are introduced to solve 3D HTM. The complex structure and heat exchange behavior of SPMSM in 3D space are fully accounted for. Meanwhile, the fast and precise prediction of the global temperature distribution of SPMSM is realized. Subsequently, in view of the excellent performance of 3D HTM, a multiphysics multiobjective optimization model applied to SPMSM is developed by combining EAM and the nondominated sorting genetic algorithm III (NSGA-III). The optimal design of SPMSM is accomplished quickly and efficiently. The multiphysics performance of SPMSM is significantly improved. Finally, the validity, accuracy, and practicality of this study are strongly demonstrated by the simulation computation and prototype experiment.

Abstracts:Wearable and reconfigurable magnetic tracking systems (MTSs) for tracking passive magnetic targets inside the body offer the benefit of closely conforming to the curvature of the human abdomen and accommodating individuals with different abdominal circumferences. However, the dynamic changes in sensor array configuration, known as deformation, caused by posture changes during long-duration examinations, impose significant challenges on MTSs that heavily rely on magnetometer poses. To address this, we propose a real-time self-sensing method based on the sensor array structural model and magnetic dipole model, which simultaneously estimates the magnet pose and the hinge angles on the sensor array. Experimental results demonstrate that our reconfigurable MTS achieves an average localization accuracy of 1.36$\,\pm\,$0.21 mm and 1.00$\,\pm\, 0.46^\circ$ even under severe deformation. Furthermore, we incorporate the prior knowledge about the sensor array configurations into the self-sensing algorithm. Theoretical analysis and experimental verification demonstrate that integrating prior knowledge can enhance algorithm performance, with a 28.57% enhancement in stability and up to a 6% improvement in global convergence rate.

Abstracts:This article proposes a time-synchronized constrained controller to address the time-varying constrained reorientation problem in spacecraft attitude operations. The characteristics of time-varying attitude constraints are formulated and analyzed. The corresponding artificial potential field-based sliding mode surface is tailored for these constraints. This method utilizes the properties of time-synchronized stability to thoroughly contemplate the interrelationships among different state errors, enabling the synchronized convergence of individual error components while ensuring compliance with state constraints. This design leads to an increase in control efficiency compared with traditional sliding mode-based constrained attitude controllers without adding any computational burden. This efficiency is evident in terms of control energy consumption and convergence time. Theoretical analysis is presented to substantiate the rationality of the proposed method. To validate these advantages, the article conducts diverse numerical simulation analyses and designs corresponding hardware-in-the-loop (HiL) experiments to verify its practical deployment capabilities.