Shane Farritor

On low-frequency electric power generation with PZT ceramics

Piezoelectric materials have long been used as sensors and actuators, however their use as electrical generators is less established. A piezoelectric power generator has great potential for some remote applications such as in vivo sensors, embedded MEMS devices, and distributed networking. Such materials are capable of converting mechanical energy into electrical energy, but developing piezoelectric generators is challenging because of their poor source characteristics (high voltage, low current, high impedance) and relatively low power output. In the past these challenges have limited the development and application of piezoelectric generators, but the recent advent of extremely low power electrical and mechanical devices (e.g., MEMS) make such generators attractive. This paper presents a theoretical analysis of piezoelectric power generation that is verified with simulation and experimental results. Several important considerations in designing such generators are explored, including parameter identification, load matching, form factors, efficiency, longevity, energy conversion and energy storage. Finally, an application of this analysis is presented where electrical energy is generated inside a prototype Total Knee Replacement (TKR) implant.

The use of piezoelectric ceramics for electric power generation within orthopedic implants

This paper presents the results of tests that demonstrate the feasibility of using piezoelectric (PZT) ceramics to generate in vivo electrical energy for orthopedic implants. Sensors encapsulated within implants could provide in vivo diagnostic capabilities such as the monitoring of implant duty (i.e., walking) cycle, detecting abnormally asymmetric or high forces, sensing misalignment and early loosening, and early detection of wear. Early diagnosis of abnormalities or impending failure is critical to minimize patient harm. However, the routine use of sensors and microprocessors embedded within orthopedic implants for diagnostic and monitoring purposes has been limited by the lack of a long-term self-contained power source capable of lasting the expected 20-year implant lifetimes. By embedding PZT materials within orthopedic implants, a small amount of the mechanical energy generated during normal physical activity can be converted into useful electrical energy. This in vivo energy source can power embedded microprocessors and sensors for a broad range of biomedical uses. The current work investigates the application of this technology to total knee replacement (TKR) implants, but it is applicable to many other implanted biomedical devices.

Natural orifice surgery with an endoluminal mobile robot

Natural orifice transgastric endoscopic surgery promises to eliminate skin incisions and reduce postoperative pain and discomfort. Such an approach provides a distinct benefit as compared with conventional laparoscopy, in which multiple entry incisions are required for tools and camera. Endoscopy currently is the only method for performing procedures through the gastrointestinal tract. However, this approach is limited by instrumentation and the need to pass the entire scope into the patient. In contrast, an untethered miniature robot inserted through the mouth would be able to enter the abdominal cavity through a gastrotomy for exploration of the entire peritoneal cavity. In this study, the authors developed an endoluminal robot capable of transgastric abdominal exploration under esophagogastroduodenoscopic (EGD) control. Under EGD control, a gastrotomy was created, and the miniature robot was deployed into the abdominal cavity under remote control. Ultimately, future procedures will include a family of robots working together inside the gastric and abdominal cavities after their insertion through the esophagus. Such technology will help to reduce patient trauma while providing surgical flexibility.

Localization and follow-the-leader control of a heterogeneous group of mobile robots

This paper investigates the control and localization of a heterogeneous (e.g., different sensing, mechanical, computational capabilities) group of mobile robots. The group considered here has several inexpensive sensor-limited and computationally limited robots, which follow a leader robot in a desired formation over long distances. This situation is similar to a search, demining, or planetary exploration situation where there are several deployable/disposable robots led by a more sophisticated leader. Specifically, the robots in this paper are designed for highway safety applications where they automatically deploy and maneuver safety barrels commonly used to control traffic in highway work zones. Complex sensing and computation are performed by the leader, while the followers perform simple operations under the leaders guidance. This architecture allows followers to be simple, inexpensive, and have minimal sensors. Theoretical and statistical analysis of a tracking-based localization method is provided. A simple follow-the-leader control method is also presented, including a method for changing followers configuration. Experimental results of localization and follow-the-leader formation-motion are included.

Mobile in vivo camera robots provide sole visual feedback for abdominal exploration and cholecystectomy

Abstract The use of small incisions in laparoscopy reduces patient trauma, but also limits the surgeon’s ability to view and touch the surgical environment directly. These limitations generally restrict the application of laparoscopy to procedures less complex than those performed during open surgery. Although current robot-assisted laparoscopy improves the surgeon’s ability to manipulate and visualize the target organs, the instruments and cameras remain fundamentally constrained by the entry incisions. This limits tool tip orientation and optimal camera placement. The current work focuses on developing a new miniature mobile in vivo adjustable-focus camera robot to provide sole visual feedback to surgeons during laparoscopic surgery. A miniature mobile camera robot was inserted through a trocar into the insufflated abdominal cavity of an anesthetized pig. The mobile robot allowed the surgeon to explore the abdominal cavity remotely and view trocar and tool insertion and placement without entry incision constraints. The surgeon then performed a cholecystectomy using the robot camera alone for visual feedback. This successful trial has demonstrated that miniature in vivo mobile robots can provide surgeons with sufficient visual feedback to perform common procedures while reducing patient trauma.

A dynamic voltage scaling algorithm for sporadic tasks

Dynamic voltage scaling (DVS) algorithms save energy by scaling down the processor frequency when the processor is not fully loaded. Many algorithms have been proposed for periodic and aperiodic task models but none support the canonical sporadic task model. A DVS algorithm, called DVSST, is presented that can be used with sporadic tasks in conjunction with preemptive EDF scheduling. The algorithm is proven to guarantee each tasks meets its deadline while saving the maximum amount of energy possible with processor frequency scaling. DVSST was implemented in the /spl mu/C/OS-II real-time operating system for embedded systems and its overhead was measured using a stand-alone Rabbit 2000 test board. Though theoretically optimal, the actual power savings realized with DVSST is a function of the sporadic task set and the processors DVS support. It is shown that the DVSST algorithm achieves 83% of the theoretical power savings for a robotic highway safety marker real-time application. The difference between the theoretical power savings and the actual power savings is due to the limited number of frequency levels the Rabbit 2000 processor supports.

Physics-based planning for planetary exploration

Recently a planetary rover returned important scientific information from Mars. More ambitious missions are planned. New planning methods are required that allow rovers to explore challenging areas with a high level of autonomy. This paper presents a planning methodology based on a physics-based model of the rover and environment. Plans are developed that allow a rover to perform a mission while explicitly considering constraints such as power, actuator, wheel slip, and vehicle stability limits. Results obtained from detailed rover simulations are presented.

Surgery with cooperative robots

Advances in endoscopic techniques for abdominal procedures continue to reduce the invasiveness of surgery. Gaining access to the peritoneal cavity through small incisions prompted the first significant shift in general surgery. The complete elimination of external incisions through natural orifice access is potentially the next step in reducing patient trauma. While minimally invasive techniques offer significant patient advantages, the procedures are surgically challenging. Robotic surgical systems are being developed that address the visualization and manipulation limitations, but many of these systems remain constrained by the entry incisions. Alternatively, miniature in vivo robots are being developed that are completely inserted into the peritoneal cavity for laparoscopic and natural orifice procedures. These robots can provide vision and task assistance without the constraints of the entry incision, and can reduce the number of incisions required for laparoscopic procedures. In this study, a series of minimally invasive animal-model surgeries were performed using multiple miniature in vivo robots in cooperation with existing laparoscopy and endoscopy tools as well as the da Vinci® Surgical System. These procedures demonstrate that miniature in vivo robots can address the visualization constraints of minimally invasive surgery by providing video feedback and task assistance from arbitrary orientations within the peritoneal cavity.

Miniature robots can assist in laparoscopic cholecystectomy.

Laparoscopy reduces patient trauma but eliminates the surgeon’s ability to directly view and touch the surgical environment. Although current robot-assisted laparoscopy improves the surgeon’s ability to manipulate and visualize the target organs, the instruments and cameras remain constrained by the entry incision. This limits tool tip orientation and optimal camera placement. This article focuses on developing miniature in vivo robots to assist surgeons during laparoscopic surgery by providing an enhanced field of view from multiple angles and dexterous manipulators not constrained by the abdominal wall fulcrum effect. Miniature camera robots were inserted through a small incision into the insufflated abdominal cavity of an anesthetized pig. Trocar insertion and other laparoscopic tool placements were then viewed with these robotic cameras. The miniature robots provided additional camera angles that improved surgical visualization during a cholecystectomy. These successful prototype trials have demonstrated that miniature in vivo robots can provide surgeons with additional visual information that can increase procedural safety.

Modeling, Analysis, and Experimental Study of In Vivo Wheeled Robotic Mobility

Laparoscopy is abdominal surgery performed with long tools inserted through small incisions. The use of small incisions reduces patient trauma, but also eliminates the surgeons ability to view and touch the surgical environment directly. These limitations generally restrict the application of laparoscopy to procedures less complex than those performed during open surgery. This paper presents a theoretical and experimental analysis of miniature, wheeled, in vivo robots to support laparoscopy. The objective is to develop a wireless mobile imaging robot that can be placed inside the abdominal cavity during surgery. Such robots will allow the surgeon to view the surgical environment from multiple angles. The motion of these in vivo robots will not be constrained by the insertion incisions. Simulation and experimental analyses have led to a wheel design that can attain good mobility performance in in vivo conditions