We encounter large-scale environments where both structured and unstructured spaces coexist, such as on campuses. In this environment, lighting conditions and dynamic objects change constantly. To tackle the challenges of large-scale mapping under such conditions, we introduce DiTer++, a diverse terrain and multi-modal dataset designed for multi-robot SLAM in multi-session environments. According to our datasets' scenarios, Agent-A and Agent-B scan the area designated for efficient large-scale mapping day and night, respectively. Also, we utilize legged robots for terrain-agnostic traversing. To generate the ground-truth of each robot, we first build the survey-grade prior map. Then, we remove the dynamic objects and outliers from the prior map and extract the trajectory through scan-to-map matching. Our dataset and supplement materials are available at https://github.com/sparolab/DiTer-plusplus/.

This paper presents a novel spherical target-based LiDAR-camera extrinsic calibration method designed for outdoor environments with multi-robot systems, considering both target and sensor corruption. The method extracts the 2D ellipse center from the image and the 3D sphere center from the pointcloud, which are then paired to compute the transformation matrix. Specifically, the image is first decomposed using the Segment Anything Model (SAM). Then, a novel algorithm extracts an ellipse from a potentially corrupted sphere, and the extracted ellipse’s center is corrected for errors caused by the perspective projection model. For the LiDAR pointcloud, points on the sphere tend to be highly noisy due to the absence of flat regions. To accurately extract the sphere from these noisy measurements, we apply a hierarchical weighted sum to the accumulated pointcloud. Through experiments, we demonstrated that the sphere can be robustly detected even under both types of corruption, outperforming other targets. We evaluated our method using three different types of LiDARs (spinning, solid-state, and non-repetitive) with cameras positioned in three different locations. Furthermore, we validated the robustness of our method to target corruption by experimenting with spheres subjected to various types of degradation. These experiments were conducted in both a planetary test and a field environment. Our code is available at https://github.com/sparolab/MARSCalib.

Place recognition using SOund Navigation and Ranging (SONAR) images is an important task for simultaneous localization and mapping (SLAM) in underwater environments. This paper proposes a robust and efficient imaging SONAR-based place recognition, SONAR context, and loop closure method. Unlike previous methods, our approach encodes geometric information based on the characteristics of raw SONAR measurements without prior knowledge or training. We also design a hierarchical searching procedure for fast retrieval of candidate SONAR frames and apply adaptive shifting and padding to achieve robust matching on rotation and translation changes. In addition, we can derive the initial pose through adaptive shifting and apply it to the iterative closest point (ICP)-based loop closure factor. We evaluate the SONAR context's performance in the various underwater sequences such as simulated open water, real water tank, and real underwater environments. The proposed approach shows the robustness and improvements of place recognition on various datasets and evaluation metrics. Supplementary materials are available at https://github.com/sparolab/sonar_context.git.

Input-output transmission ratio shifting mechanisms provide a variable transmission ratio, which effectively expands a speed-force operating range of actuators. Although it is the most effective solution to increase the performance of robotic systems, its application to compact robotic systems still remains a challenging issue due to its complexity and massive structure. In this paper, we introduce a twisted string actuation-based transmission module for compact robotic systems. The twisted string mechanism provides a simplified transmission design and a compact form factor of the transmission module. An automatic transmission shifting algorithm is proposed for effective and autonomous control strategies. The developed prototype is integrated into a robotic gripper/hand, and its performance is verified with grasping demonstrations.

This paper presents the mechanism and design of a robotically steerable catheter system for percutaneous and minimally invasive treatment of mitral regurgitation. One of the main causes of mitral regurgitation is an impaired mitral valve topology, that results in severe heart-related diseases. Repair or replacement of the mitral valve through open-heart surgery such as traditional sternotomy has been conducted as a treatment. However, at least 50 % of patients with severe mitral regurgitation are not candidates for this surgery due to their age or comorbidities. Recently, minimally invasive or transcatheter approaches for mitral valve repair/replacement have been gaining attention to minimize the surgery's risk and several catheter mechanisms have been proposed in early phase clinical trials. Although dexterity and manipulability are essential functions in the transcatheter procedure, a direct torsional capability has not been implemented in the systems. We present a design of a 5-DoF robotically steerable catheter having two bending joints, two torsion joints having a direct torquing design, and a mitral implant delivery module to provide dexterous manipulation of the tip of the catheter. Designs and kinematic models of each joint module are presented and their performance is verified with experiments. Lastly, a mitral clip implanting procedure is demonstrated in a phantom heart model.

Cervical spinal cord injury (SCI) can severely impact hand motor and sensory function, and accordingly, patients with SCI are often unable to complete basic everyday tasks without assistance. In recent years, there has been an increase in hand exoskeleton research due to their distinct advantages for improving rehabilitation. In this work, we present a voice-controlled, tendon-driven soft robotic hand rehabilitation exoskeleton for hand function improvement in patients with cervical SCI. A new fabrication process utilizing high consistency rubber silicone is used to construct a formfitting, durable, and customizable exoskeleton glove. Bioinspired tendon routing pathways embedded within the glove create 5 actively actuated degrees-of-freedom in the index finger, middle finger, and thumb for both extension and flexion. Tendon tension sensors are developed and integrated into the exoskeleton system. The force feedback from the sensors is used in the implementation of admittance control for the exoskeleton system to improve grasping motions. The exoskeleton was evaluated in a case study with a healthy participant through range-of-motion characterization, pinch force testing, admittance controller validation, and object manipulation.

The combination of a dexterous continuum robot and magnetic resonance imaging can potentially improve surgical precision and minimize brain manipulation in a minimally invasive neurosurgical procedure. In this work, a seven degree-of-freedom (DoF) continuum neurosurgical robot was developed. The main innovation lies in the design of a safe and robust switching mechanism and gear-based quick-connect mechanism that, respectively, allow selective actuation of the 6-DoF end effector using only three motors and highly efficient end effector exchange. Its performance has been validated in experiments involving multi-segment dexterous motion. We also evaluated the robotic system on a human cadaver head in a clinical 3-Tesla MRI. The entire workflow of robotic system set-up was implemented, confirming its clinical feasibility. The signal-to-noise ratio (SNR) drop was consistently less than 6% throughout various stages of end effector motion.

This article introduces the analysis and control of a meso-scale two degree-of-freedom robotic endoscopic tool body for minimally invasive surgeries. The design of the robotic tool uses two types of a tendon-driven joint known as a bending flexure joint that allows us to control each degree-of-freedom by minimizing interjoint coupling by design. Pure kinematic modeling and control for these robots may not provide precise control performance due to kinematic uncertainties arising from tendon elongation, tendon slacking, gear backlash, etc. We propose a static model for each of the joints of the robotic tool that avoids several of these problems. Depending on the direction of tendon tension application, the proximal joint displays considerable hysteresis due to the superelastic material characteristics and this is included in our static model. The statics of a highly compliant distal joint is also modeled and validated using finite element analysis and experimental data. Using these models, we develop a control system that comprises of a disturbance observer and the proposed static model to provide precise force control and compensate for joint hysteresis.

Mitral regurgitation is one of the most common heart diseases caused by ventricular dysfunction or anatomic abnormality of the mitral valve. The fundamental treatment for mitral regurgitation is to repair/replace the mitral valve through open-heart surgery which is risky and requires more time to recover or through minimally invasive approaches, which have significant challenges and limitations. Through the transcatheter approach, the mitral valve implant is minimally invasively delivered directly to the mitral valve and is clamped onto the leaflet to mitigate or prevent regurgitation. However, this procedure requires delicate manipulation of the catheter in a constrained space and remains a challenging problem. In this work, we present a robotically steerable cathether design for the transcatheter procedure to address mitral regurgitation. The proposed catheter consists of two bending joints, one torsion joint, and implant delivery module at the distal end of the robot. Kinematic models for each joint design are derived and compared with experimental results. Finally, we experimentally demonstrate the feasibility of the proposed catheter to navigate in a phantom heart model. In this demonstration, the bending joint was actuated by 75°, the torsion joint was actuated by 90° and the implant was pushed out by 1.8 mm to deliver the implant.

Hydrocephalus in the pediatric population is often treated with endoscopic procedures, in which a rigid endoscope provides a working channel and needed visualization for brain manipulation. The lack of flexible and steerable endoscopic tools limits the ability of the surgeon to conduct complex operations. In this paper, we propose the design of a novel tool for such procedures that uses the compliance of a bending flexural joint to build a compact steerable multi-joint tool. These joints are machined into a tube made of a super-elastic material to create two joints near the tip of the tool. The directional stiffness properties of the flexural joint are exploited to minimize inter-joint coupling. We perform a static analysis of each joint and a kinematic analysis of the entire robot. We follow this with the design of a hand-held controller for this robot, and analyze its ability to control multiple degrees-of-freedom of the robot while minimizing the coupling between joints.

In this work, we propose a voice-controlled hand rehabilitation device driven by exotendons. A smartphone-based voice recognition system interprets user intention and is utilized for various grasping tasks. A bio-inspired tendon routing mechanism provides four-degrees-of-freedom (DoFs) across the thumb, index finger, and middle finger. A novel thumb sleeve design is presented for stable thumb movement. The exoskeleton is fabricated from polyurethane rubber and rigid 3D-printed parts to provide form-fitting properties while constraining tendon motion. Twisted string actuators and spring units provide active flexion and passive extension, respectively. The compact nature of the actuation unit allows for placement on the forearm, improving the portability of the system. The voice control system allows for easy user manipulation and accessibility and may improve rehabilitation efficiency. The performance of the tendon routing and thumb sleeve design were experimentally evaluated and voice control system was evaluated with various grasping tests.

In this paper, a dual-mode twisting actuation mechanism with an active clutch is newly presented for a high performance tendon-driven robot (e.g., robot hand). This mechanism is a kind of mechanical automatic power transmission mechanism which provides fast motion and large contraction force by two geared motors. One of the motors is adopted for main actuation and the other is utilized for active clutch. The active clutch consisting of low-power DC motor and gear set allows easy control of the dual-mode twisting actuation and simplifies relaxation process of twisted strings which was a critical problem by a passive brake in previous research [17]. Kinematics of the proposed mechanism is represented and its simulation is performed to verify the performance numerically. By using BLDC & DC motor with 8 W & 0.3 W power, we developed a prototype of the dual-mode twisting actuation with the weight of 45.7 g and the size of 71 mm × 21.5 × 15 mm. Despite of simple structure, the proposed mechanism shows that operation mode-change can be easily managed and the relaxation time was much more reduced than that of the passive brake version.