Active Suspension System Energy and Power Requirements for Military Applications

Center for Electromechanic

Dynamic Simulations of a Large High-Frequency Power System

Dynamic simulations to assess performance aspects of a large high-frequency power system have been conducted. The analysis uses a model of an 80-MW power system for an all-electric ship. The model, developed in the Matlab/Simulink environment, includes several power generation units, two propulsion power trains, an energy storage system, a high-power pulse load, and several service loads. Three case studies were addressed. The first considers the response of the power system to a high-power step load, representing a sudden request for acceleration of the ship. The second deals with the effects of a partial loss of generation during operation. The third addresses the effects of load drop on the power system.Center for Electromechanic

An alternative architecture and control strategy for hexapod positioning systems to simplify structural design and improve accuracy

Hexapod systems (6 legged Stewart Platforms), offer advantages in accuracy over other positioning systems and are finding applications in numerous telescopes. However, instruments with increased sophistication for modern telescopes continue to grow in size and required positioning accuracy. This paper details an alternative hexapod configuration and design approach, particularly focused on relatively large, high precision hexapod systems supporting high mass payloads. The new configuration improves accuracy, reduces actuator mass, simplifies design, and reduces system cost but requires modest additional control algorithm sophistication.Center for Electromechanic

Development of Electric Propulsion Motors with Integrated Power Electronics

The effective integration of electric power in future naval ships requires the development of technologies that allow for volume and mass reduction of critical components. The University of Texas at Austin Center for Electromechanics is studying the potential for volume and mass reduction through the integration of power electronics into an electric propulsion motor. Two conceptual designs of a motor with integrated power electronics are presented. Integration of power electronics into the motor frame offers space saving advantages, allowing the motor and power electronics to share the same housing and cooling system. Accordingly, significant mass and volume reductions are possible in the power electronics housing and cooling auxiliaries.Center for Electromechanic

Light-Weight Containment for High Energy, Rotating Machines

Developed a lightweight containment system for high-speed composite rotors. The containment device, consisting of a rotatable, composite structure, has been demonstrated to contain the high-energy release from a rotor burst event and is applicable to composite rotors for pulsed power applications. The most important aspect of this design is that the free-floating containment structure dissipates the major loads (radial, torque, and axial) encountered during the burst event, greatly reducing the loads that pass through the stator structure to its attachments. The design results in significant system-level weight savings for the entire rotating machine when compared to a system with an all-metallic containment. Of equal interest to the containment design, the experimental design and instrumentation was very challenging and resulted in significant lessons learned. This paper describes the containment system design, rotor burst test setup, instrumentation for measuring loads induced by the burst event, and a detailed explanation of the successful containment test results and conclusions.Center for Electromechanic

Design and development of a high precision, high payload telescope dual drive system

A high precision, dual drive system has been designed and developed for the Wide Field Upgrade to the Hobby-Eberly Telescope* at McDonald Observatory in support of the Hobby-Eberly Telescope Dark Energy Experiment‡. Analysis,design and controls details will be of interest to designers of large scale, high precision robotic motion devices. The drive system positions the 19,000 kg star tracker to a precision of less than 5 microns along its 4-meter travel. While positioning requirements remain essentially equal to the existing HET, tracker mass increases by a factor greater than 5. The 10.5-meter long tracker is driven at each end by planetary roller screws, each having two distinct drive sources dictated by the desired operation: one slowly rotates the screw when tracking celestial objects and the second rotates the nut for rapid displacements. Key results of the roller screw rotordynamics analysis are presented. A description of the complex bearing arrangement providing required degrees of freedom as well as the impact of a detailed Failure Modes and Effects Analysis addressing necessary safety systems is also presented. Finite element analysis results demonstrate how mechanical springs increase the telescope's natural frequency response by 22 percent. The critical analysis and resulting design is provided.Center for Electromechanic

Design, testing, and installation of a high-precision hexapod for the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX)

Engineers from The University of Texas at Austin Center for Electromechanics and McDonald Observatory have designed, built, and laboratory tested a high payload capacity, precision hexapod for use on the Hobby-Eberly telescope as part of the HETDEX Wide Field Upgrade (WFU). The hexapod supports the 4200 kg payload which includes the wide field corrector, support structure, and other optical/electronic components. This paper provides a recap of the hexapod actuator mechanical and electrical design including a discussion on the methods used to help determine the actuator travel to prevent the hexapod payload from hitting any adjacent, stationary hardware. The paper describes in detail the tooling and methods used to assemble the full hexapod, including many of the structures and components which are supported on the upper hexapod frame. Additionally, details are provided on the installation of the hexapod onto the new tracker bridge, including design decisions that were made to accommodate the lift capacity of the Hobby-Eberly Telescope dome crane. Laboratory testing results will be presented verifying that the performance goals for the hexapod, including positioning, actuator travel, and speeds have all been achieved. This paper may be of interest to mechanical and electrical engineers responsible for the design and operations of precision hardware on large, ground based telescopes. In summary, the hexapod development cycle from the initial hexapod actuator performance requirements and design, to the deployment and testing on the newly designed HET tracker system is all discussed, including lessons learned through the process.Center for Electromechanic

The Development of high-precision hexapod actuators for the Hobby-Eberly Telescope Wide Field Upgrade

Hexapods are finding increased use in telescope applications for positioning large payloads. Engineers from The University of Texas at Austin have been working with engineers from ADS International to develop large, high force, highly precise and controllable hexapod actuators for use on the Wide Field Upgrade (WFU) as part of the Hobby Eberly Telescope Dark Energy Experiment (HETDEX)‡. These actuators are installed in a hexapod arrangement, supporting the 3000+ kg instrument payload which includes the Wide Field Corrector (WFC), support structure, and other optical/electronic components. In addition to force capability, the actuators need to meet the tracking speed (pointing) requirements for accuracy and the slewing speed (rewind) requirements, allowing as many observations in one night as possible. The hexapod actuator stroke (retraction and extension) was very closely monitored during the design phase to make sure all of the science requirements could be met, while minimizing the risk of damaging the WFC optical hardware in the unlikely event of a hexapod actuator or controller failure. This paper discusses the design trade-offs between stiffness, safety, back-drivability, accuracy, and leading to selection of the motor, high ratio worm gear, roller screw, coupling, end mounts, and other key components.Center for Electromechanic

Active Magnetic Bearings for Energy Storage Systems for Combat Vehicles

Advanced energy storage systems for electric guns and other pulsed weapons on combat vehicles present significant challenges for rotor bearing design, Active magnetic bearings (AMBs) present one emerging bearing option with major advantages in terms of lifetime and rotational speed, and also favorably integrate into high-speed flywheel systems. The Department of Defense Combat Hybrid Power Systems (CHPS) program serves as a case study for magnetic bearing applications on combat vehicles. The University of Texas at Austin Center for Electromechanics (UT-CEM) has designed active magnetic bearing actuators for use in a 5 MW flywheel alternator with a 318 kg (700 lb), 20000 rpm rotor. To minimize CHPS flywheel size and mass, a topology was chosen in which the rotating portion of the flywheel is located outside the stationary components. Accordingly, magnetic bearing actuators are required which share this configuration. Because of inherent low loss and nearly linear force characteristics, UT-CEM has designed and analyzed permanent magnet bias bearing actuators for this application. To verify actuator performance, a nonrotating bearing test fixture was designed and built which permits measurement of static and dynamic force. An AMB control system was designed to provide robust, efficient magnetic levitation of the CHPS rotor over a wide range of operating speeds and disturbance inputs, while minimizing the occurrence of backup bearing touchdowns. This paper discusses bearing system requirements, actuator and controller design, and predicted performance; it also compares theoretical vs. measured actuator characteristicsCenter for Electromechanic

Design and analysis of a 20 MW propulsion power train

The electric ship research program at the University of Texas at Austin focuses on the development of power system technology for future electric ships. The main goal of the on-going research activity is to identify critical, high pay-off technology development needed to enable major improvement, in size and functionality, of navy ships power systems. Initial efforts were directed towards the establishment of a baseline power train which highlights various constraints and provides a basis for later optimization efforts. A 20 MW power train system was chosen for such a baseline, and all components, from fuel to propulsion motor, were considered and their impact on the whole power system assessed. The baseline design consists of a 25 MVA/3600 rpm radial flux permanent magnet generator, a 22 MVA PWM converter, and a 20 MW/150 rpm radial flux permanent magnet motor, along with the amount of fuel sized for an assumed mission profile, and the widely used LM2500 gas turbine. The analysis shows that fuel is by far the dominant component contributing to weight and volume and, consequently, overall efficiency of power train components is the most relevant parameter to reduce weight and volume. The 3600 rpm generator is the smallest component. The 150 rpm motor is the heaviest component, other than fuel, weighing close to 100 tonnes.Center for Electromechanic