John F. Jansen

Ferrofluid field induced flow for microfluidic applications

Exposing a column of ferrofluid to coincident magnetic and thermal fields produces a pressure gradient in the magnetic fluid. As the column of ferrofluid heats up, it loses its attraction to the magnetic field and is displaced by cooler fluid. Subsequently, it is possible to generate a ferrofluid pump with no moving mechanical parts. Until recently, limitations in the magnetic and thermal properties of conventional materials severely limited operating pressures. Advancements in the design and synthesis of metal substituted magnetite enable fine control over both the magnetic and thermal properties of magnetic nanoparticles, a key element in ferrofluids. This manuscript covers three recent contributions to the design of ferrofluid pumps. First, we introduce a new approach to the synthesis of metal substituted magnetite nanoparticles based on thermophilic metal-reducing bacteria. Next, we extend the previous work in the modeling of the ferrofluid pumps to include the coupling between each of the three fundamental domains: magnetic, thermal and fluid dynamic. We validate these models with a comparison between experimental results and a multidomain finite element model. Our results show a good match between the model and experiment as well as approximately an order of magnitude increase in the fluid flow rate over conventional magnetite based ferrofluids operating below 80/spl deg/C. Finally, as a practical demonstration, we describe a novel application of this technology: pumping fluids at the microfluidic scale.

Imaging colorimetry: a new approach.

A new technique is described for the in-process measuring of the color content of images with pixel resolution, using commercially available devices. Color measurement is extremely important in the printing industry for assessing the quality of printed graphic images. Commercially available instruments designed to measure color, in process, have outputs that represent the average color content over specific areas of the printed surface. The color content of an image feature on the printed surface that may be important to consumers is then difficult to assess from these general readings. Instead of an average reading, the technique that we describe provides a color measurement of each pixel within the area of interest on the printing surface so that the color content of specific features can be evaluated.

On the modeling of robots operating on ships

The decrease in manpower and increase in material handling needs on many naval vessels provides the motivation to explore the modeling and control of naval robotic and robotic assistive devices. This paper presents a simple methodology to symbolically compute the dynamic equations of motion of a serial link manipulation system operating on the moving deck of a ship. First we provide background information that quantifies the motion of the ship, both in terms of frequency and amplitude. We then formulate the motion of the ship in terms of homogeneous transforms. Likewise, the kinematics of a manipulator is considered as a serial extension of the ship motion. We then show how to use these transforms to formulate the kinetic and potential energy of the arm moving on a ship. As a demonstration, we consider two examples: a one degree-of-freedom system experiencing three sea states operating in a plane to verify the methodology and a 3 degree of freedom system experiencing all six degrees of ship motion to illustrate the ease of computation and complexity of the solution. We provide a preliminary comparison between conventional linear control and repetitive learning control (RLC) and show how fixed time delay RLC breaks down due to the varying wave disturbance frequency.

Mesofluidic actuation for articulated finger and hand prosthetics

The loss of fingers and hands severely limits career and lifestyle options for the amputee. Unfortunately, while there have been strides made in advancements of upper arm and leg prosthetics, the state of the art in prosthetic hands is lagging far behind. Options are generally limited to claw like devices that provide limited gripping capacity. The overall objective of this paper is to demonstrate a path towards a low-cost prosthetic hand with multiple articulated fingers and a thumb that rivals the human hand in terms of weight, size, dexterity, range of motion, force carrying capacity and speed. We begin with a description of the functional requirements for a human hand. When comparing requirements with actuation technologies, the fluid power approach has the potential to realize a prosthetic hand that rivals a human hand in size, strength and dexterity. We introduce a new actuation technology, mesofluidics, that focuses on miniaturization of fluid power to the meso-scale (mm to cm). As a novel demonstration of the potential for this technology, we describe a proof-of-principle mesofluidic finger that has intrinsic actuation and control (actuators and control valves within the volume of the finger). This finger weighs 63 grams, is sized to the 50th percentile male finger, has a total of 25 mechanical parts and is capable of providing 10 kg (22 lbs) of pinch force.

Design of a telerobotic controller with joint torque sensors

The authors show how to design a joint controller for a telerobotic system when joint torque sensors are available. Other sensors, such as actuator position, actuator velocity, joint position, and joint velocity, are assumed to be accessible; however, the results will also be useful when only partial measurements are available. The controller presented can be applied to either mode of operation of a manipulator (i.e. teleoperation or robotic). Mechanical manipulators with high levels of friction are assumed. The results are applied to a telerobotic system built for NASA. Very high levels of friction have been reduced using high-gain feedback while avoiding limit cycles.<<ETX>>

Control of a teleoperator system with redundancy based on passivity conditions

Ways a stiffness controller can be used to control a teleoperator system with a redundant degree-of-freedom (DOF) slave manipulator and a dissimilar master are examined. No path planning is allowed because of the uncertainty of the environment and computational limitations. The proposed controller was implemented on the 7-DOF Center for Engineering Systems Advanced Research Manipulator slave manipulator with a 6-DOF Kraft master manipulator. The overall performance of this scheme and future directions are discussed.<<ETX>>

Modeling and testing of a novel piezoelectric pump

While there is a wide range of actuation technologies, none currently rivals the overall performance (power density, bandwidth, stress, stroke) of conventional hydraulic actuation [1]. It is well known in the actuation community that the power-to-weight ratios and the power-to-volume ratios of hydraulic actuators are, respectively, around 5 times and 10 to 20 times larger than comparable electric motors. Due to fundamental limitations in the magnetic flux density in the supporting structures and limitations in the heat transfer out of electric actuators, significant changes in these ratios are not likely in the near future [2]. Thermal limitations associated with electric motors do not apply to hydraulic actuators since the hydraulic fluid cools and lubricates the system. However, with all of these virtues, hydraulic actuators have serious practical implementation problems. Typically, servo-based hydraulic actuators are leaky and have generally poor energy efficiencies. This work addresses a new type of electric actuator that combines the best of both the electric and hydraulic mediums.

Modeling and control of a hydraulically actuated flexible-prismatic link robot

Most of the research related to flexible link manipulators to date has focused on single link, fixed length, single plane of vibration test beds. In addition, actuation has been predominantly based upon electromagnetic motors. Ironically, these elements are rarely found in the existing industrial long reach systems. This paper describes a new hydraulically actuated, long reach manipulator with a flexible prismatic link at Oak Ridge National Laboratory (ORNL). Focus is directed towards both modeling and control of hydraulic actuators as well as flexible links that have variable natural frequencies.

Hydraulically powered dissimilar teleoperated system controller design

Addresses two issues associated with the implementation of a hydraulically powered dissimilar master-slave teleoperated system. These issues are the overall system control architecture and the design of robust hydraulic servo controllers for the position control problem. Finally, a discussion of overall system performance on an actual teleoperated system is presented. (Schillings Titan II hydraulic manipulators are the slave manipulators and the master manipulators are from the Oak Ridge National Laboratory-developed Advanced Servo Manipulator).

Development of a remote trauma care assist robot

In typical teleoperated surgeries, skilled staff are still necessary in the remote surgical room to change manipulator tooling and to manage surgical supply delivery and removal. This paper describes the development of a nurse robot to provide automated support to a teleoperated surgical manipulator system in environments where the presence of skilled surgical support staff may not be practical. The tools must be inserted precisely into a compliant manipulator in a timely manner, and the supplies are diverse in nature. To support experimental investigations and evaluations, a seven degrees-of-freedom commercially available manipulator was selected. The design of novel end-effectors, tool grasping and supply holding features, and tool auto-loading systems for optimum surgical tool changing and supply delivery in minimum time is presented. A novel approach for calibration of the nurse robot among compliant and rigid subsystems and for managing forces during subsystem interaction is described and experimental results using this force management approach are presented. Overall experimental performance data for the nurse robot system during tool changing and supply delivery tasks is also presented to illustrate the feasibility of performing these functions in a remote medical or trauma care-assist cell.