Fault-tolerant transputer-based controller configurations for gas-turbine engines

Advanced optimization of gas turbine aero-engine transient performance using linkage-learning genetic algorithm: Part II, optimization in flight mission and controller gains correlation development

Safe operation of Gas Turbine Engines (GTEs) is one of the paramount missions in the GTE industry. Ensuring reliable operation and control performance is a challenging task that involves optimizing engine performance across various operating points. The Model Predictive Control (MPC) technique is a powerful approach that provides an optimization framework to meet the management and control requirements of GTEs during their operation. This work presents a systematic control framework to efficiently control a GTE. The proposed control algorithm employs an adaptive MPC methodology that ensures both safe and efficient engine operation. The MPC structure is adapted across varying operating points, and its parameters are optimized to provide control inputs that ensure best engine performance during both transient and steadystate engine operation. To enhance control reliability, the MPC is systematically coupled with min-max limiters to maintain critical variables within allowable bounds, ultimately to prevent engine surge, flame-out, and exceeding unsafe variable limits. Through this approach, the aim is to achieve a superior level of safety and operability for GTE control and management. Simulation results on a generic commercial turbofan engine with a 40,000-pound thrust show that the proposed algorithm outperforms a gain-scheduled PI controller with min-max limiters, and demonstrate enhanced performance in engine management and control.

A stable gain scheduled controller for a gas turbine engine that drives a variable pitch propeller is developed and described. A stability proof is developed for gain scheduled closed-loop system using global linearization and linear matrix inequality (LMI) techniques. Using convex optimization tools, a single quadratic Lyapunov function is computed for multiple linearizations near equilibrium and nonequilibrium points of the nonlinear closed-loop system. This approach guarantees stability of the closed-loop gas turbine engine system. To verify the stability of the closed-loop system on-line, an optimization problem is proposed, which is solvable using convex optimization tools. Simulation results show that the developed gain scheduled controller is capable to regulate a turboshaft engine for large thrust commands in a stable fashion with proper tracking performance.

Searching for more efficient ways to improve process quality and increase plant throughput has encouraged changes in the control system architecture toward greater distribution. A distributed control system, illustrated in Fig.15.1, can be defined as control systems in which functions around a plant are distributed into computing nodes (i.e., control computers and smart devices) that are physically separated; and all the computing nodes are interconnected by digital communication networks (e.g., fieldbuses). Distributed control systems are now found in many industrial fields, such as oil and gas production (Hars, 1994), automobiles (Hansson et al., 1997), and gas turbine engine control (Shaffer, 1999). Advances in distributed control system technology have been driven by the ever increasing performance of smart field devices and fieldbuses using smaller, less expensive and more functional microprocessors. In fact, the goal of a distributed control system is the same as its centralised counterpart; that is, to get input from the plant through its sensors and give output using its actuators. However, the use of field-buses and smart devices introduces many advantages into a distributed control system over a centralised one. Not only does a distributed architecture offer reduced wiring and simplified maintenance, it also provides the opportunity to implement different control strategies. Consequently, the emergence of distributed control systems is promoting changes in control systems design issues. One of the key changes from conventional control techniques is driven by the local processing power. In distributed architectures, smart devices employing a built-in microprocessor with a fieldbus interface offer the possibility of the faster and more reliable self-diagnosis and self-compensation. Several researchers (Henry 1993; Koscielny et al 1997) have discussed the benefits of local fault-diagnosis. Extra information about the element status reported through a fieldbus network is also very beneficial for reconfigurable control. For example, Lee et al. (2001) presented an on-line retuning strategy for PI control to tolerate actuator faults using this information.

: Synthesis procedures for nonlinear stochastic feedback control of gas turbine engines were developed and evaluated. Modern estimation and control procedures based upon separating the stochastic and deterministic aspects of the control problem were employed. The resulting closed-loop control consists of nonlinear deterministic feedback control logic designed using piecewise-linear/piecewise-optimal techniques, and an estimator designed using nonlinear filtering logic. Engine variables estimated from noise-corrupted measurements are fed back through the deterministic control logic to generate commanded inputs to the engine. Mode-switching logic was developed to provide smooth transition between small-signal regulation and large-signal transient modes of estimator/controller operation.

: This report describes the results of a design, fabrication, bench test, and evaluation of an engine-mounted advanced technology gas turbine engine control system on which development was started under previous Army contracts. The control system comprises a full-authority electronic computer module, a fuel metering and inlet guide vane actuator module, a high-speed fuel pump and alternator module, a radiation pyrometer for blade temperature limiting, and other required sensors. The control modules are evaluated on an experimental Army gas turbine engine (STAGG) which was under development at Pratt and Whitney Florida Research and Development Corporation. Tests of the engine-mounted system were conducted in two phases. An environmental phase allowed the control components to be debugged and evaluated over the full power range of the engine while the engine was being controlled by a test stand control system. The second phase of testing demonstrated active control of the engine. All of the engine-mounted control testing was conducted in accordance with the planned engine test schedule on a noninterference basis. Approximately 44 hours of engine-mounted testing were accumulated, and about 8.6 of these hours included active engine control. During this testing, all of the control modules were successfully evaluated including the control of engine accelerations, decelerations, speed governing, inlet guide vane scheduling and ignition.

This paper presents techniques for design and control of a brushless direct-current (DC) limited-angle torque motor (LATM) with its application to fuel control of gas turbine engines. Given the desired specifications, a two-pole brushless DC LATM with a toroidally wound armature is designed using selected ferromagnetic material and rare-earth permanent magnets; its electromagnetic characteristics is then computationally found and well tuned using the finite element method (FEM) in order to ensure whether the design meets the performance specifications. To achieve the simple and inexpensive semi-closed-loop fuel control, a robust position controller (including a proportional-integral-derivative (PID) controller with a prefilter) is synthesized for providing the required positioning performance for the developed motor, thereby achieving an inexpensive semi-closed-loop fuel control. A closed-loop fuel controller associated with the proposed position controller and a flow meter is then proposed based on multi-loop control structure in order to achieve required linear input–output relationship. All the proposed fuel control laws were implemented using a stand-alone single-chip digital signal processor (DSP). Experimental results are conducted to show the efficacy and usefulness of the developed limited-angle torque motor with its application to an experimental gas turbine fuel control test platform.

The Navy Landing Craft Air Cushion (LCAC) Service Life Extension Program (SLEP) upgrades the current TF40B gas turbine engine and analog control system on the LCAC to an Enhanced TF40B (ETF40B) gas turbine with a Full Authority Digital Engine Control (FADEC) system. This upgrade and enhancement will provide additional engine horsepower, increased engine reliability, and modern digital engine control equipment to the LCAC. The success of the ETF40B engine development program has been an ongoing effort between the Navy, the LCAC craft builder Textron Marine & Land Systems (TM&LS), and the engine manufacturer Honeywell Engine and Systems. This paper will document and outline the differences between the TF40B and ETF40B and the efforts of the ETF40B 150 hour endurance qualification test.

Based on the success of gas turbine and automotive engine control system designs, a single lever power control (SLPC) model for aircraft piston engines has been developed utilizing fuzzy logic controllers. To permit development and refinement of the SLPC controllers, a propulsion simulation workbench has been developed for simulation of light aircraft piston engine applications. The objective of the workbench is to provide a platform on which the aircraft engine control system modeling and development can occur. The workbench is an integrated set of Matlab Simulink/sup (R)/ models of a piston aircraft engine, variable pitch propeller, and controller. In addition, an atmospheric model simulates the ambient conditions as they change with aircraft altitude. Results of simulated aircraft missions show dynamic and steady state characteristics of both the propulsion system model and single lever power control system to be acceptable for this application, and demonstrate the utility of the engine/propeller simulation.

This paper describes an advanced survivable avionics system for future manned or unmanned space missions. The basic element of such an avionics system is a Byzantine fault tolerant computer (FTC), which has already been developed at DASA-RI for operation in the Russian segment of the International Space Station Alpha (ISSA). The paper outlines the essential design elements of the FTC, especially the efficient realisation of the Byzantine protocol within the constraints of technical risk and cost. We describe a quadruplex redundant MIL 1553 bus system with a synchronised packet protocol as communication medium between the FTC and the peripheral sensors and actuators. To illustrate the generic approach applied in the FTC design this paper also describes a fault tolerant Propulsion Drive Electronic (PDE) as a redundant actuator subsystem. The PDE will be equipped with basic communication and control elements re-using the FTC design.

New Approach To The Formation Of The Adequate Diagnostic Matrix Of The Gas Turbine Engine

In order to improve the traditional speed-tension type three-motor synchronous control platform based on PLC bus control to further enhance the speed and control accuracy of the control system, enhance the control effect, Speed-Tension type Three-motor coordinate synchronous control platform based on Multi-microprocessor is proposed in this paper.In this platform, the complex programmable logic devices (CPLD), Digital Signal Processor (DSP) and microcontroller (MCU) are combined.In order to improve rapid and synchronization of the control system, CPLD Parallel nature is used to achieve three serial ports synchronous and concurrency control; Complex control algorithms are implement by the use of DSP fast and efficient data processing capabilities; Experimental results show: The control system is stable, at the same baud rate the control speed of the platform based on multi-microprocessor is more than three times faster than the one of the traditional PLC bus control platform.In the multi-microprocessor control platform， under the same control algorithm regulation time is more fast 0.53 seconds than traditional PLC control platform, the overshoot of the system is 13.53% of the one using traditional PLC control platform, and the tracking the maximum error reduces 60.53% than the one of the traditional PLC control platform.

The distributed control architecture becomes more and more important in future gas turbine engine control systems, in which, the sensors and actuators will be connected to the controllers via a network. Therefore, the control problem of network-enabled high-performance distributed engine control (DEC) has come to play an important role in modern gas turbine control systems. While, due to the properties of the network, the packet-dropouts must be considered. This study introduces a distributed control system architecture based on a networked cascade control system (NCCS). Typical turboshaft engine-distributed controllers are designed based on the NCCS framework with a H ∞ state feedback under random packet-dropouts. The sufficient robust exponential mean-stable conditions are derived via the Lyapunov stability theory and linear matrix inequality approach. Simulations illustrate the effectiveness of the presented method.

The present paper considers the speed control system of a single-shaft gas turbine engine (GTE). A well-known transfer function of the GTE has been modeled in the Matlab environment. A digital PID controller has been calculated that provides the preset dynamic performance indicators of the discrete GTE speed control system functioning. An assessment of the robust stability of the GTE control system has been performed. A modified root locus for the transfer function with interval coefficients has been constructed. The graphical method is based on the application of the strong Kharitonovs theorem which provides a visual demonstration of the absolute robust stability of the GTE speed control system.

Increasing market pressure for industrial turbine controls that reduce cost of installation, increase availability, and reduce overall installation and commissioning time have driven systems in a new direction. This direction is away from complex and expensive triplex or TMR (Triple Modular Redundant) systems and towards dual redundant and networked control systems. Woodward’s core fuel and combustion control is currently being used in a networked system for GE’s LM2500 aeroderivative gas turbine packages. This networked control system utilizes redundant high-speed communications from the sequencer to fuel control. Packaging I/O is also distributed over redundant communications to localize wiring. The fuel control communicates to the gas metering valves and gas turbine variable geometry servo-valves to reduce wiring and installation time. This control system utilizes simplex CPU’s to save cost and duplex hardware and communications for availability. Expansion of this to full redundant CPU processing capabilities can also be achieved to add availability with some cost tradeoff. Woodward has also applied this full redundancy concept in the commercial marine GE LM2500 package applications. In addition to using network communications the core fuel control system is in itself networked, being “package” mounted. Mounting the fuel control on the package reduces the number of field installation wire terminations and the total length of wire used between the gas turbine and the fuel control. Having the main fuel control system mounted on the package allows the control to be wired and tested at the factory rather than at site. The use of network communications in gas turbine control applications has many advantages. Reduction in overall system cost, installation and commissioning time are the main advantages to using networked controls for gas turbines. System expandability and distributed processing are other advantages. Expanding this with hardware redundancy improves availability.