Recently, surface tension has been shown to be important in emerging high technologies, such as in pumping and control of flow in microfluidic devices, in microchemical analysis of complex fluids, and in rapid DNA screening, etc. Advances in these new technologies will depend strongly on the availability of flexible methods for controlling surface tension. Photo-control using a photoresponsive surfactant is a potentially attractive route to accomplishing many of the tasks required in these processes. Photoresponsive surfactants typically incorporate an azobenzene group as the functional unit which experiences reversible trans-to-cis photoisomerization under different irradiation conditions. The photoisomerization usually causes a change in surface tension. Obviously, a large change in surface tension under different illumination conditions will be highly desirable in practical applications. However, the largest change in surface tension as reported in the literature is only 3 mN/m which is too small to generate any significant effect. In this presentation, we report a new class of photoresponsive surfactants which exhibit excellent performance in surface tension control. Under different illumination conditions, the change in surface tension can be as large as 11.0 mN/m. Experimental results are presented for two new photoresponsive surfactants. A discussion of experimental results follows. / Singapore-MIT Alliance (SMA)

A tension control algorithm for the deployment of a unmanned ground vehicle from an autonomous helicopter is designed and tested in this thesis. The physical hardware which the controller will run on is detailed. The plant model and underlying controllers are derived and modeled. The tension controller algorithm is selected, derived, and modeled. The parameters of the tension controller are chosen and simulations are run with the chosen parameters. The tension control algorithm is run on the physical hardware, successfully demonstrating tension control on a ground vehicle. Robustness simulations are run for a change in the radius of the spool and the length of the tether. Lastly, Future work is outlined on several paths to move forward with the tension controller. / Master of Science

Designing a filament winding machine involves two major components. First component is the designing of the mechanism which delivers appropriate winding pattern as specified by the user (i.e. the winding angle). The second component is the realization of an effective fiber tensioning system for ensuring consistent overall consolidation. Today, there exist a variety of sophisticated methods to achieve both these parameters; however the implementation of these techniques increases the price of a winding machine, making its acquisition very difficult for small scale applications. Sophisticated winding machine includes higher number of degrees of freedom, and high end CNC controlled algorithms. However for creating axi-symetric products with constant diameter, only a 2-axis winding is sufficient. On this note a novel cost effective method for fiber winding angle control and fiber winding tension control is designed, simulated, implemented into a low cost prototype 2-axis filament winding machine, and the scope for its? further improvement has also been discussed. The system designed, uses a cost effective PLC as the centralized controller of the system for implementing both fiber winding control and tension control through PID control. A novel actuator for tension control is designed and implemented. Also a comparison between the conventional PI controller and a Mamdani type Fuzzy inference based control system for controlling the fiber tension is made. In this process a novel technique for making PI controller capable of handling known nonlinearities in the system is introduced. Experimental system responses of the designed prototype are analyzed.

This study examines a specific application of button-head type twist-off bolts. Currently, the Research Council on Structural Connections Specification (2000) removes the requirement for ASTM F436 washers (ASTM 2000a) under the bolt head of twist-off bolts where the head diameter equals or exceeds that of an ASTM F436 washer when oversized and slotted holes are used. The need for washers is also removed for A490 strength bolts used on steels with specified yield strengths less than 40 ksi provided that the head diameter equals or exceeds an ASTM F436 washer. The ASTM F1852 Specification (ASTM 2000b) allows for head diameter dimensions that are slightly smaller than an ASTM F436 washer. Following the RCSC Specification, manufacturers that produce bolts using the ASTM F1852 dimensions are required to use ASTM F436 washers under the bolt head. The discrepancies between the specifications lead to this study, which involved the testing of button-head type twist-off bolts with two different head diameters, both of which were smaller than an ASTM F436 washer. Five bolt diameters between 5/8 in and 1-1/8 in. were tested in standard, oversized, and long-slotted holes. The performance of the twist-off bolts was determined by measuring and comparing the achieved relaxed pretension force in the bolt after tightening. It was found that twist-off bolts with head diameters less than an ASTM F436 washer had no trouble attaining their required minimum pretension force. Bolt head diameter and hole size were found to have no significant influence on the pretension force that was achieved for all bolts tested. / Master of Science

A mathematical model for a Two-Span Web Roller machine is defined in order to facilitate motion planning, motion tracking and state observer design for tracking web tension and web velocity. Differential Flatness is utilized to create reference trajectories that are tracked with a high convergence rate. Flatness also allows for nominal input torque generation without integration. Constraints on the inputs are satisfied through the motion planning phase. A partial state feedback linearization is performed and an exponential tracking dynamic feedback controller is defined. An exponential Kalman-related tension observer is also defined with semi-optimal gain formulation. The observer takes advantage of the bilinearity of the dynamics up to additive output nonlinearity. The closed-loop system is simulated in MatLab with comparisons to reference trajectories previously employed in literature. The importance of proper motion planning is demonstrated by producing excellent performance compared with existing tracking and tension observing methods.

A mathematical model for a Two-Span Web Roller machine is defined in order to facilitate motion planning, motion tracking and state observer design for tracking web tension and web velocity. Differential Flatness is utilized to create reference trajectories that are tracked with a high convergence rate. Flatness also allows for nominal input torque generation without integration. Constraints on the inputs are satisfied through the motion planning phase. A partial state feedback linearization is performed and an exponential tracking dynamic feedback controller is defined. An exponential Kalman-related tension observer is also defined with semi-optimal gain formulation. The observer takes advantage of the bilinearity of the dynamics up to additive output nonlinearity. The closed-loop system is simulated in MatLab with comparisons to reference trajectories previously employed in literature. The importance of proper motion planning is demonstrated by producing excellent performance compared with existing tracking and tension observing methods.