Because they are capable of subjecting massive payloads to the high accelerations that typical HWIL simulation
scenarios require, it is commonly accepted in the industry that hydraulically-driven flight motion simulators (FMS) offer
advantages over other technologies. However, their small-signal performance does not traditionally match that of their
electromechanical counterparts. This paper presents design improvements in the direct-drive hydraulic servo that
improve accuracy and extend bandwidth, thereby closing the performance gap with electromechanical servos. The paper
reports system performance improvements predicted by comprehensive mathematical simulation. These new design
concepts are being applied to a 3-axis motion simulator test bed model, whose testing will be reported in a follow-up
report.
KEYWORDS: Digital filtering, Device simulation, MATLAB, Lead, Fermium, Frequency modulation, Analog electronics, Actuators, Linear filtering, Data acquisition
Flight motion simulator (FMS) controllers must be tuned to compensate for nonlinear hydraulic plant characteristics and optimize dynamic response within the specified operating bandwidth of each axis. Carco has developed the Matlab-based Carco Tool Kit that adapts the SigLab data acquisition system to perform the specific stimulus and measurement routines required for efficient FMS tuning. Each controller filter is first simulated in Matlab, added to acquired uncompensated-loop data, and optimized using interactive Bode and Nichols charts. The analog filter tuning component values are then extracted from equivalent PSPICE simulations, while the digital filter coefficients are copied directly into the digital controller programming script.
User desire for flight motion simulator (FMW) dynamic transparency is a major factor in selecting the `optimum' structural design and control strategies for hardware-in- the-loop simulations. There are numerous design strategies that can satisfy a given set of user specifications. However, the resulting FMS performance may not be equivalent in terms of satisfying user objectives. This paper describes software simulation and design optimization tools that are effective in evaluating design trade-offs. Examples of performance trade-offs are provided.
Hit-to-kill interceptors and other thruster-controlled missiles demand flight motion simulators having sufficiently accurate high frequency dynamic performance to simulate flexible body behavior. A new servoactuator design is described that uses a piezoelectric element to control a novel open-center hydraulic valve. Detailed nonlinear dynamic models are presented for the valve servoamplifier, piezo element, orifice flow, and hydraulic supply decoupling. These are combined with the structural model of a single actuator system. The resulting system model indicates that several such actuators used in combination would provide accurate simulation of missile body vibration signatures up to 1 kHz or beyond.
The Infrared Simulation and Test Acceptance Facility (IR STAF) will be a state-of-the-art hardware-in-the-loop (HWIL) simulation/test facility for performing all-up-round missile testing in a non-destructive laboratory environment. Full-up IR guided missiles will be placed on a five-axis flight motion simulator (FMS) to allow closed-loop testing of the missile for the full range of tactical flight scenarios. This paper focuses on the unique requirements placed on the FMS, and the design trade-offs that led to performance parameters that could meet mission requirements. The inner three axes of the FMS carries the all-up-round missile under test and the outer two axes move a dynamic IR scene projector system. A real-time control computer simulates the aerodynamic and kinematics response of the missile and generates commands for the FMS and IR scene projector. This system puts the missile under test through multiple scenarios as opposed to a single live-firing. Non-destructive HWIL testing can reduce the number of live firings during lot acceptance tests (LATs) while verifying system performance with a high degree of confidence. The purpose of the facility is to substantially reduce the cost of missile lot acceptance testing while maintaining or improving the confidence in missile hardware.
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