Architected materials derive performance characteristics from material properties and internal geometry. These materials are increasingly prevalent across a wide variety of domains. Many intricate feature geometries associated with architected materials can be explored using additive manufacturing (AM) processes. However, current AM methods generally cannot fabricate geometries with completely closed voids without introducing a support structure. This paper describes a new, support-free approach to AM capable of creating structures with closed voids. This work limits part geometry to three-dimensional (3D) geometries defined by a revolution about a single axis. This limitation enables planar analysis within a three-degree-of-freedom (3-DoF) task space. Part geometry in 3-DoF task space is constrained to a convex arch. Task space geometry is divided into an ordered set of sub-regions, considering feasible deposition orientations and collision constraints. The use of 3-DoF task space provides planar translation and rotation of the component during fabrication. The introduction of this rotational DoF addresses AM overhang constraints imposed by gravity. Methods for generating, ordering, and layering sub-regions suitable for printing a part with a closed hole are presented. Layers derived in the 3-DoF task space analysis are then extended to 3D deposition paths using the axis of revolution defined by the original part. The method of hole closure relies on the concept of a "keystone" which requires a 45° nozzle offset for collision-free deposition within keystone-adjacent sub-regions. The feasibility of deposition using a 45° nozzle offset is explored experimentally, and results demonstrate feasibility.

The ability of robotic systems to effectively address disaster scenarios that are potentially dangerous for human operators is continuing to grow as a research and development field. This leverages research from areas such as bimanual manipulation, dexterous grasping, bipedal locomotion, computer vision, sensing, object segmentation, varying degrees of autonomy, and operator control/feedback. This paper describes the development of a semi-autonomous bimanual dexterous robotic system that comes to the aid of a mannequin simulating an injured victim by operating a fire extinguisher, affixing a cervical collar, cooperatively placing the victim on a spineboard with another bimanual robot, and relocating the victim. This system accomplishes these tasks through a series of control modalities that range from supervised autonomy to full teleoperation and allows the control model to be chosen and optimized for a specific subtask. We present a description of the hardware platform, the software control architecture, a human-in-the-loop computer vision algorithm, and an infrastructure to use a variety of user input devices in combination with autonomous control to compete several dexterous tasks. The effectiveness of the system was demonstrated in both laboratory and live outdoor demonstrations.

A new type of continuum manipulator is presented, in which the body of the device is made up of identical, repeated interlocking fibers. A working prototype is demonstrated. Basic models describing the kinematics and mechanical properties of the device are developed, and their predictions are compared with the performance of the physical prototype. Advantages of the interlocking design include improved strength due to better load distribution, controllable stiffness, and a large open lumen.

Osteolysis is a debilitating condition that can occur behind the acetabular component of total hip replacements due to wear of the polyethylene liner. Conventional treatment techniques suggest replacing the component, while less-invasive approaches attempt to access and clean the lesion through the screw holes in the component. However, current rigid tools have been shown to access at most 50% of the lesion. Using a recently developed dexterous manipulator, we have adapted a group-theoretic convolution framework to define the manipulator's workspace and its ability to fully explore a lesion. We compared this with the experimental exploration of a printed model of the lesion. This convolution approach successfully contains the experimental results and shows over 98.8% volumetric coverage of a complex lesion. The results suggest this manipulator as a possible solution to accessing much of the area unreachable to the conventional less-invasive technique.

This paper presents the experimental validation of software-based safety features implemented during the control of a prosthetic limb in self-feeding tasks with a human patient. To ensure safe operation during patient controlled movements of the limb, velocity-based virtual fixtures are constructed with respect to the patient's location and orientation relative to the limb. These imposed virtual fixtures or safety zones modulate the allowable movement direction and speed of the limb to ensure patient safety during commanded limb trajectories directed toward the patient's body or environmental obstacles. In this implementation, the Modular Prosthetic Limb (MPL) will be controlled by a quadriplegic patient using implanted intracortical electrodes. These virtual fixtures leverage existing sensors internal to the MPL and operate in conjunction with the existing limb control. Validation of the virtual fixtures was conducted by executing a recorded set of limb control inputs while collecting both direct feedback from the limb sensors and ground truth measurements of the limb configuration using a Vicon tracking system. Analysis of the collected data indicates that the system performed within the limitations prescribed by the imposed virtual fixtures. This successful implementation and validation enabled the approved clinical use of the MPL system for a neural controlled self-feeding task.

This paper presents a method for estimating drive cable length in an underactuated, hyper-redundant, snake-like manipulator. The continuum manipulator was designed for the surgical removal of osteolysis behind total hip arthroplasties. Two independently actuated cables in a pull-pull configuration control the compliant manipulator in a single plane. Using a previously developed kinematic model, we present a method for estimating drive cable displacement for a given manipulator configuration. This calibrated function is then inverted to explore the ability to achieve local manipulator configurations from prescribed drive cable displacements without the use of continuous visual feedback. Results demonstrate an effectiveness in predicting drive cable lengths from manipulator configurations. Preliminary results also show an ability to achieve manipulator configurations from prescribed cable lengths with reasonable accuracy without continuous visual feedback.

This paper presents M3Express (Modular-Mobile-Multirobot), a new design for a low-cost modular robot. The robot is self-mobile, with three independently driven wheels that also serve as connectors. The new connectors can be automatically operated, and are based on stationary magnets coupled to mechanically actuated ferromagnetic yoke pieces. Extensive use is made of plastic castings, laser cut plastic sheets, and low-cost motors and electronic components. Modules interface with a host PC via Bluetooth®radio. An off-board camera, along with a set of modules and a control PC form a convenient, low-cost system for rapidly developing and testing control algorithms for modular reconfigurable robots. Experimental results demonstrate mechanical docking, connector strength, and accuracy of dead reckoning locomotion.

Intraoperative patient registration may significantly affect the outcome of image-guided surgery (IGS). Image-based registration approaches have several advantages over the currently dominant point-based direct contact methods and are used in some industry solutions in image-guided radiation therapy with fixed X-ray gantries. However, technical challenges including geometric calibration and computational cost have precluded their use with mobile C-arms for IGS. We propose a 2D/3D registration framework for intraoperative patient registration using a conventional mobile X-ray imager combining fiducial-based C-arm tracking and graphics processing unit (GPU)-acceleration. The two-stage framework 1) acquires X-ray images and estimates relative pose between the images using a custom-made in-image fiducial, and 2) estimates the patient pose using intensity-based 2D/3D registration. Experimental validations using a publicly available gold standard dataset, a plastic bone phantom and cadaveric specimens have been conducted. The mean target registration error (mTRE) was 0.34 ± 0.04 mm (success rate: 100%, registration time: 14.2 s) for the phantom with two images 90° apart, and 0.99 ± 0.41 mm (81%, 16.3 s) for the cadaveric specimen with images 58.5° apart. The experimental results showed the feasibility of the proposed registration framework as a practical alternative for IGS routines.

A dexterous manipulator (DM) with a large open lumen is presented. The manipulator is designed for surgical applications with a preliminary focus on the removal of osteolysis formed behind the acetabular shell of primary total hip arthroplasties (THAs). The manipulator is constructed from two nested superelastic nitinol tubes enabling lengthwise channels for drive cables. Notches in the nested assembly provide reliable bending under applied cable tension producing kinematics that can be effectively modeled as a series of rigid vertebrae connected using pin joints. The manipulator is controlled in plane with two independently actuated cables in a pull-pull configuration. For the purpose of the procedure, the manipulator is mounted on a Z-θ stage adding a translational and rotational degree of freedom (DOF) along the axis of the manipulator. Preliminary experimental results demonstrate the initial modeling and control of the manipulator.

A new self-reconfigurable robot is presented. The robot is a hybrid chain/lattice design with several novel features. An active mechanical docking mechanism provides inter-module connection, along with optical and electrical interface. The docking mechanisms function additionally as driven wheels. Internal slip rings provide unlimited rotary motion to the wheels, allowing the modules to move independently by driving on flat surfaces, or in assemblies negotiating more complex terrain. Modules in the system are mechanically homogeneous, with three identical docking mechanisms within a module. Each mechanical dock is driven by a high torque actuator to enable movement of large segments within a multi-module structure, as well as low-speed driving. Preliminary experimental results demonstrate locomotion, mechanical docking, and lifting of a single module.

A problem associated with motion planning for the assembly of individual modules in a new self-reconfigurable modular robotic system is presented. Modules of the system are independently mobile and can be driven on flat surfaces in a similar fashion to the classic kinematic cart. This problem differs from most nonholonomic steering problems because of an added constraint on one of the internal states. The constraint properly aligns the docking mechanism, allowing modules to connect with one another along wheel surfaces. This paper presents an initial method for generating trajectories and control inputs that allow module assembly. It also provides an iterative method for locally optimizing a nominal control function using weighted perturbation functions, while preserving the final pose and internal states.