Charles E. Penney

Laboratory testing of the pulse power system for the cannon caliber electromagnetic gun system (CCEMG)

The team of (prime contractor) United Defense LP (UDLP) and The University of Texas at Austin Center for Electromechanics (UT-CEM) has completed a significant portion of the testing phase of a trailer mounted compulsator driven 35 mm (round bore equivalent) rapid fire railgun system. The objective of the program is to develop a compact, lightweight pulse power test bed capable of launching 3, 5 round salvos of 185-g integrated launch packages to 1.85 km/s at a firing rate of 5 Hz. Per contractual requirements, the pulse power system is also size compatible with the Amphibious Assault Vehicle (AAV). The pulse power system is developed around a second generation air-core, 4-pole rotating armature, self-excited, compulsator design. The 40 MJ at 12,000 rpm composite rotor stores all 15 shots inertially and is capable of 2.5 GW performance into the 2.21 m long series augmented railgun. This paper describes the CCEMG pulse power supply configuration and highlights important features of the commissioning test plan. The paper then presents test results from mechanical runs, stand alone compulsator (CPA) rectifier tests, short circuit tests, and single shot live fire tests. Finally, CPA performance is compared with predictions for the single shot tests presented.

Continued testing of the cannon caliber electromagnetic gun system (CCEMG)

The cannon caliber electromagnetic gun system is based upon a compulsator driven 30 mm rapid fire railgun system. The objective of the program was to develop a compact, lightweight test bed capable of launching three, five round salvoes of 185 g integrated launch packages to 1.85 km/s at a firing rate of 5 Hz. Per contractual requirements, the pulse power system is also size compatible with the amphibious assault vehicle. The pulse power system was developed around a fourth generation air-core, 4-pole rotating armature, self-excited, compulsator design. Although the contract for this effort has expired, the system continues to be used in part to demonstrate compulsator driven railgun technology. This system has performed seven single shots using identical control settings for each shot, which is the first such experience using a compulsator driven railgun system. This paper describes the experimental set-up for the demonstrations and compares the generator, converter, gun switch, and launcher performances for each shot.

Testing of the cannon caliber rapid fire railgun

A rapid fire launcher has been designed, built, and tested in single-shot mode for the Cannon Caliber Electromagnetic Gun (CCEMG) System. The 2.25-m long railgun has a rectangular cross-section (30 mm round bore equivalent) and has a series, two-turn augmented rail configuration. The gun is designed for rapid fire operation; three, five round salvos of 185 g integrated launch packages (ILPs) accelerated to 1,850 m/s with a minimum time between salvos of 2.5 s. Launch packages will be autoloaded at a repetition rate of 5 Hz via a hydraulic mechanism capable of up to 3,000 lb insertion forces. The railgun support structure and flexible buswork permit the railgun to recoil approximately 2 cm to mitigate the electromagnetic repulsion loads. Multiple 830 kA pulses provided from the CCEMG compulsator power supply require the gun to be liquid cooled for thermal management. Diagnostics for the single-shot tests include B-dots, flux rulers, voltage, and current measuring sensors. Other launcher diagnostics include rail conductor temperatures, coolant temperatures, and railgun preload mechanism (flatjacks) dynamic pressures. This paper presents the test results and general gun performance observations for single-shot, compulsator powered experiments.

Single shot switch performance on the cannon caliber electromagnetic gun program

The Cannon Caliber Electromagnetic Gun (CCEMG) program at The University of Texas at Austin Center for Electromechanics incorporates two solid state switch modules. The 95 MW rectifier/inverter bridge (RIB) generates the field inside of the compulsator (CPA) and the 825 kA gun switch module (GSM) is the main closing switch between the CPA and the launcher. Since commissioning the CCEMG system, nearly 400 discharges have been performed using these switches. These tests produced a significant amount of information which will be very useful for the design of future solid-state switching systems on other electromagnetic launch programs. This paper presents the basic design, testing and lessons learned from the commissioning of the CCEMG system switches.

HETDEX tracker control system design and implementation

To enable the Hobby-Eberly Telescope Dark Energy Experiment, The University of Texas at Austin Center for Electromechanics and McDonald Observatory developed a precision tracker and control system – an 18,000 kg robot to position a 3,100 kg payload within 10 microns of a desired dynamic track. Performance requirements to meet science needs and safety requirements that emerged from detailed Failure Modes and Effects Analysis resulted in a system of 13 precision controlled actuators and 100 additional analog and digital devices (primarily sensors and safety limit switches). Due to this complexity, demanding accuracy requirements, and stringent safety requirements, two independent control systems were developed. First, a versatile and easily configurable centralized control system that links with modeling and simulation tools during the hardware and software design process was deemed essential for normal operation including motion control. A second, parallel, control system, the Hardware Fault Controller (HFC) provides independent monitoring and fault control through a dedicated microcontroller to force a safe, controlled shutdown of the entire system in the event a fault is detected. Motion controls were developed in a Matlab-Simulink simulation environment, and coupled with dSPACE controller hardware. The dSPACE real-time operating system collects sensor information; motor commands are transmitted over a PROFIBUS network to servo amplifiers and drive motor status is received over the same network. To interface the dSPACE controller directly to absolute Heidenhain sensors with EnDat 2.2 protocol, a custom communication board was developed. This paper covers details of operational control software, the HFC, algorithms, tuning, debugging, testing, and lessons learned.

Design and testing of a high-speed spin test for evaluating pulse alternator windage loss effects

Advanced pulse alternator designs require rotor surface speeds in excess of 1000 m/s. High tip speeds and an operating environment consisting of partial vacuum result in frictional windage losses and subsequent heating of the rotor and stator surfaces. Analytical models for cylindrical rotor windage loss exist. However, solving the combined fluid dynamics and thermal conduction problem for this specific operating regime requires significant code development. A series of spin tests with incremental levels of complexity have been designed and tested and are presented in this paper. The tests are intended to validate windage loss and heating codes used in the pulse alternator rotor design.

Use of failure modes and effects analysis in design of the tracker system for the HET wide-field upgrade

In support of the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX), the Center for Electromechanics at The University of Texas at Austin was tasked with developing the new Tracker and control system to support the HETDEX Wide-Field Upgrade. The tracker carries the 3,100 kg Prime Focus Instrument Package and Wide Field Corrector approximately 13 m above the 10 m diameter primary mirror. Its safe and reliable operation by a sophisticated control system, over a 20 year life time is a paramount requirement for the project. To account for all potential failures and potential hazards, to both the equipment and personnel involved, an extensive Failure Modes and Effects Analysis (FMEA) was completed early in the project. This task required participation of all the stakeholders over a multi-day meeting with numerous follow up exchanges. The event drove a number of significant design decisions and requirements that might not have been identified this early in the project without this process. The result is a system that has multiple layers of active and passive safety systems to protect the tens of millions of dollars of hardware involved and the people who operate it. This paper will describe the background of the FMEA process, how it was utilized on HETDEX, the critical outcomes, how the required safety systems were implemented, and how they have worked in operation. It should be of interest to engineers, designers, and managers engaging in complex multi-disciplinary and parallel engineering projects that involve automated hardware and control systems with potentially hazardous operating scenarios.

Design and testing of the power electronics for the cannon caliber electromagnetic gun system

The University of Texas Center for Electromechanics (UT-CEM) is in the final fabrication and testing phase of a power electronics system required to operate a skid mounted compulsator-driven railgun. Design goals for the self-excited air core compulsator include a 95 MW rectifier/inverter bridge for field coil self-excitation. Initial field coil seed energy is supplied by a 50 kJ capacitive discharge from the field initiation module. The field coil is passively protected from voltage transients by an array of metal oxide varistors. Other system power modules include the gun closing switch and explosive opening switch. This paper presents a brief system overview and detailed design of the rectifier/inverter bridge module with performance data from shots up to 6.

Sensor development for compulsator driven railgun systems

As the technologies of rotating power supplies and thyristor switches advance, new methods of measuring various signals must be developed. The University of Texas at Austin Center for Electromechanics (UT-CEM) has developed new methods to measure compulsator position and speed and has made advancements in health monitoring of the thyristor switches. Technological advancements in machine design have enabled dramatic increases in machine speeds, which in turn increase electromagnetic interference. It is essential to a successful operation to have a method (reliable within this harsh environment) of measuring speed and sensing rotor position to generate gate signals for thyristor switch modules. As the modules switch larger amounts of current and voltage, it is correspondingly important to monitor the switching process, so that any damage to the system caused by a fault condition can be minimized. This paper describes sensors developed at UT-CEM to monitor speed, sense rotor position, and detect fault conditions.

Testing, characterization, and control of a multi-axis, high precision drive system for the Hobby-Eberly Telescope Wide Field Upgrade

A multi-axis, high precision drive system has been designed and developed for the Wide Field Upgrade to the Hobby- Eberly Telescope at McDonald Observatory. Design, performance and controls details will be of interest to designers of large scale, high precision robotic motion devices. The drive system positions the 20-ton star tracker to a precision of less than 5 microns along each axis and is capable of 4 meters of X/Y travel, 0.3 meters of hexapod actuator travel, and 46 degrees of rho rotation. The positioning accuracy of the new drive system is achieved through the use of highprecision drive hardware in addition to a meticulously tuned high-precision controller. A comprehensive understanding of the drive structure, disturbances, and drive behavior was necessary to develop the high-precision controller. Thorough testing has characterized manufacture defects, structural deflections, sensor error, and other parametric uncertainty. Positioning control through predictive algorithms that analytically compensate for measured disturbances has been developed as a result of drive testing and characterization. The drive structure and drive dynamics are described as well as key results discovered from testing and modeling. Controller techniques and development of the predictive algorithms are discussed. Performance results are included, illustrating recent performance of several axes of the drive system. This paper describes testing that occurred at the Center for Electromechanics in Austin Texas.