Christopher Y. Brown

Design of a new cable-driven manipulator with a large open lumen: Preliminary applications in the minimally-invasive removal of osteolysis

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.

Design of a new independently-mobile reconfigurable modular robot

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.

Efficiency and effectiveness analysis of a new direct drive miniature quadruped robot

This paper introduces a new, 50g miniature robot (Figure 1 and attached video) that uses four direct-drive hybrid wheel/legs and has been clocked at speeds exceeding 30 body lengths/s. The lowest recorded cost of transport (defined as total energy to move the robot mass a given distance) is 0.90. We discuss hardware considerations for design of robots at this scale, and the benefits of a direct-drive system over coupled transmissions. We develop a simple simulation model to examine the effects of drive speed and mechanical properties of the legs, and compare the results with experimental data on efficiency and effectiveness of locomotion with various leg designs.

Approaches to robotic teleoperation in a disaster scenario: From supervised autonomy to direct control

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 MEMS sensor for low-frequency vibration energy harvesting

This paper reports ongoing work in development of a MEMS electrostatic sensor for self-powered detection of mechanical vibrations of less than 1000 Hz. The sensor is an in-plane overlapping comb configuration. Six different variants on a common design were fabricated on a single die using the commercial SOI-MUMPS process. Additional masses were manually added to lower the resonant frequency.

Buckybot: A robot based on the geometry of a truncated icosahedron

This paper introduces Buckybot, a novel mobile platform, and investigates its kinematics and preliminary control algorithms. Buckybot is a ground-based platform whose geometry is based on a truncated icosahedron, i.e. a soccer ball with flattened sides. The platform has 20 passive hexagonal faces on which it can stably rest, and 12 rounded pentagonal faces which can be extended linearly to tilt Buckybot. The symmetric geometry of the robot makes it operational in any configuration which is ideal for a variety of deployment scenarios including throwing or dropping. Buckybot currently locomotes using a semi-static tipping gait to move between adjacent hexagonal faces. In this work, we present the design and low-level control of the Buckybot platform, explore the kinematics associated with Buckybot’s method of locomotion, experimentally characterize tipping, and investigate trajectory planning for this new mobile robot. Results demonstrate effective trajectory planning accounting for plan uncertainty.Copyright

Electrofluidic systems for contrast management

Operating in dynamic lighting conditions and in greatly varying backgrounds is challenging. Current paints and state-ofthe- art passive adaptive coatings (e.g. photochromics) are not suitable for multi- environment situations. A semi-active, low power, skin is needed that can adapt its reflective properties based on the background environment to minimize contrast through the development and incorporation of suitable pigment materials. Electrofluidic skins are a reflective display technology for electronic ink and paper applications. The technology is similar to that in E Ink but makes use of MEMS based microfluidic structures, instead of simple black and white ink microcapsules dispersed in clear oil. Electrofluidic skins low power operation and fast switching speeds (~20 ms) are an improvement over current state-ofthe- art contrast management technologies. We report on a microfluidic display which utilizes diffuse pigment dispersion inks to change the contrast of the underlying substrate from 5.8% to 100%. Voltage is applied and an electromechanical pressure is used to pull a pigment dispersion based ink from a hydrophobic coated reservoir into a hydrophobic coated surface channel. When no voltage is applied, the Young-Laplace pressure pushes the pigment dispersion ink back down into the reservoir. This allows the pixel to switch from the on and off state by balancing the two pressures. Taking a systems engineering approach from the beginning of development has enabled the technology to be integrated into larger systems.