Method of HWIL simulation for the dual-mode optical sensor

Toru Yonezawa, Toshiya Kinoshita, Ryuji Ohtake, Hisayuki Nakajima, Hiroshi MiyauchiToshiba Corporation, Komukai Works

Komukaitoshiba-cho 1, Saiwai-ku, Kawasaki, 210-8581, Japan

ABSTRACT

Hard-Ware-In-the-Loop (1-TWIL) simulation is used as a means of performance evaluation of a flying object in ToshibaCorporation. Especially, in the evaluation of guidance and control performance in a development phase, and a performancecheck of the product in a mass-production phase, this technique plays an important part.

In this paper, our facilities for FIWIL simulation (flight simulator, computer, and target generator) are presented. Then,the simulation execution approach and method in various development phases are described focusing on the example inwhich a dual-mode optical sensor is evaluated. Specifically the execution approach in the case only with a sensor (withoutnavigation unit etc.) is described first. Secondly the approach in which a navigation unit is added to a sensor is described.Furthermore, the approach is described when a control unit that includes a servomotor and control surfaces is added to them.

Keywords: Guidance and Control, Sensor, simulation

1. INTRODUCTION

As for the means of guidance and control of the moving object that moves in 3-dimensional space, such as an aircraft( namedflying object), there is a means in which an external target point is observed. And the direction to move is controlledon the basis of the line of sight (LOS) of the target. This means is considered to need the device made up of a CCDthatdetects a target and a mechanism that tracks the target. Besides the sensor, a servomotor which gives a controlling force tothe flying object and a navigation unit which converts a sensor output into a command to a control unit are very importantcomponents. As for the target detection, two kinds of means, an optics and radio frequency (RF) way can be considered. Inthe case of an optical way, an image observation of the target is used recently, and when it is RF, range finding and directionmeasuring by radar are mainly used.

In the development of a flying object, the performance evaluation of the sensor is indispensable, and HWIL simulationis considered as the one approach for the evaluation. With the exception of real flight, HWIL simulation is probably themost important means of performance evaluation in that the components are acted. When executing HWIL simulation, thefunctions of the systems other than the component under test need to be simulated by the computer. As it may be mentionedlater, the more the proportions for which accounts to all the components under test are (i.e., the less the degree of themathematical simulation is), the higher the fidelity of the simulation becomes. In the development of a flying object, thecomponents with which a test can be presented are restricted according to the development phase. And the test approach andstyle should change with each case. Moreover, also in the phase of mass production, FIWIL simulation is used as means of asynthetic performance check.

2. FACILITIES OF HWIL SIMULATION

The block diagram of the facilities of FIWIL simulation is shown in Fig. 1. This facility roughly consists of threesystems, i.e. a flight simulator, a computer, and a target generator. Henceforth, the outline of these systems is presented.

2.1. Flight Simulator

A flight simulator is the equipment in which the five-axis gimbals can be moved dynamically. Five gimbals include thethree-axis gimbals of orientation angle of the flying object and the two-axis gimbals of direction angle of the target. Gimbalsare moved with hydraulic power. The two-axis gimbals in which the target generator is carried are called target gimbals.There are two kinds of target gimbals, one is for an optical target with a short arm, and the other is for a RF targetwith along arm. By interchanging this target gimbals, both types of sensor can be evaluated. Overview of the flight simulator isshown in Fig. 2, and the major performance is shown in Table 1.

Part of the SPIE Conference on Technologies for Synthetic Environments:120 Hardware-in-the-Loop Testing IV • Orlando, Florida • April 1999

SPIE Vol. 3697 • 0277-786X/99/$1O.00

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FLIGHT SIMULATOR TARGET GENERATOR

Table I Specifications of Flight Simulator

MODEL S-495R-[) (CARC() ELEcTR( )NICS)

MAXANGULARSPEE1)(deg/sec)

I

(ROLL)1000

(PITCH)60()

(YAW)ô0()

(AZIMUTH)90(OP)50(RF)

(ELEVATION)L0(OP)30(1(F)

FREQUENCYRESPONSE

(Hi)20 20 2() 1)

3.5(1(F)S(OP)

3.5(1(F)

PRECI SION

(deg) o i 0.05 0.05 0.05 0.05

LI

Fig.1 Block Diagram of II WIL Facilities

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2.2. Computer

A computer calculates a 6—DOF motion of the flying object, and outputs the orientation iLligles of the l1vin objectaround three axes (roll, pitch. yaw) and direction angles of the target (a,irnuth and elevation) to the flight simulator. Thecomputer consists of the operation unit with ('PU. and analoe and digital I/o unit. To the flight simulator, it is perfornungoutput usine the analog signals now. Al)SIM language is used for modeling, and it describes a motion of a fl inz object mda target. A calculation lime step is 50011 sec to I msec. The major performance of a computer is shown in table 2.

Table 2 Specifications of Computer

122

MODEL AI)-RTS(AI)I)

OPERATION PERFORMANCE ô4hits (Floating Point)• TIME STEI < Imsec

ANALOG I/O INPUT 32ch (I hits)• OUTPUT S2ch

DIGITAL I/O fJ

INPUT 8chOUTPUT ch

Fig.2 Picture of Flight Simulator

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2.3. Targetgenerator

The target generator presents the object of observation for the sensor that is carried on the flight simulator. Two kinds oftarget generator, an optical type and RF type, can be presented so that each kind of sensor can be evaluated.

2.3.1. Dual-mode optical target generator

When evaluating the dual-mode sensor which can detect the target by two means such as infrared and visible, thefollowing conditions need to be fulfilled.. Togenerate a visible and an infrared target simultaneously at the same position (on the same axis).. Loading on the target gimbal of the flight simulator is possible.In order to fulfill these conditions, a small target generator which can make dual-mode target was created. The setup of thistarget generator is shown in Fig. 3, and a picture is shown in Fig. 4. The visible generation unit is using the halogen lamp asthe illuminant, and can carry out irradiation of the infinitely far target on a uniform background to the sensor using a patternplate (on which the target configuration is positioned). The background brightness can be adjusted as two phaseswith/without an attenuater.

IR REFLECTER

1T.::..::iIIEIIttI:.::O[ VISIBLE GENERATION UNIT

VISIBLE ILLUMINATION

OLLIMATERLENS LENS REFLECTER

Fig.3 Setup of Optical Target Generator

123

BLACKBODYFURNACE

.:z:•::::::::::::i IR PATTERN PLATE

IR GENERATION UNIT

IR COLLIMATER

SENSOR

COMPOSITIONUNIT

VISIBLEPATTERN PLATE 'IP

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In the infrared generation unit, it is possible to carr\ out irradiation of the infinilelr far target to the sensor by collimating aninfrared—light radiation bundle through the pinh ole of a pattern plate from a hlackbodv furnace. The target tern perature Caiihe adjusted continuously. In a composition unit, a visible and an infrared—light can be composed so that a COrIipOUn(l lihtcan he generated. The error between the axes is (1.5 imad or less. With this taret 1eneralor. a sensor cail receive the imaieof visible and infrared both, and can process both signals for guidance and control of a t1vin object. The major performanceof the optical target generator is showii in Table 3.

I P. (ieneration Unit

Fig.4 Picture of Optical Target Generator

Table 3 Specifications of Optical i'arget (;eneratr

124

VISIBLE (;ENERATION UNIT Band Width ().5—0. fi m

• Collimater Lens > loOmni

• Background Brightness t0000cdim2

INFRARED GENERATION UNIT Band Width 2.5—f i iii

• Concave Mirror 70mm

• Target Temperature

E : En v iroam en I Temp. 0—40C

COMPOSITION UNIT Error between 2-Axes < ft5mrad

'visible ( ieneri1ion Un it

Composition Unit

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2.3.2. RF target generator

The setup of PF target generator is shown in Fig. 5. By this RF target generator, the reflected wave responded with thetransmitted wave from a sensor, i.e. a radar, is generated. Disturbances such as glint-noise, multipath, and clutter can becreated with this equipment.

3. HWIL SIMULATION APPROACH

In the development of a flying object, all the components are hardly evaluated at a simultaneous time. Then, a few oftest approaches are considered when the components are restricted. For example, the system that consists of a sensor, anavigation unit, and a control unit, which are shown in Fig. 6 is considered. A sensor tracks a target and outputs the steeringerror signals into the navigation unit. A navigation unit converts the signals from the sensor into the control surfacedeflection commands with the autopilot and the other sensors, such as inertial measurement unit (IMU) which are includedin it. In a control unit, control surfaces are driven by the actuator to follow the command from the navigation unit. Nowconsidering the following three cases about the real components to be evaluated, the HWILsimulation approach for eachcase is described.• CASE 1: the case only with a sensor• CASE 2: the case with a sensor + a navigation unit• CASE 3: the case with a sensor + a navigation unit + a control unit

RF TARGET GENERATOR

Fig.5 Setup of RF Target Generator

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3.1. CASE 1

In this case, a few components can be evaluated and the accuracy of a simulation model becomes low at the point offidelity. However, because the considerable part of guidance and control performance is due to the sensor, this approach ofevaluation must be important when checking the performance of the whole flying object.

What have the main sensor performance are. Resolution of image(pixel number). Data rate of an image processing. Performance of tracking (Angular velocity etc.). Stability of a sensor (How much is the sensor separated from the oscillation of a flying object?)

As a final result of these performances, the steering error signals are outputted from a sensor. In the test, modeling thenavigation and control unit by the computer is required. This modeling is performed in a part of processing of the computeras well as a motion calculation of a flying object. The points of modeling a navigation system are the error of IMU andprocessing delay. And the frequency responsibility is regarded as a point on modeling a control unit.

3.2. CASE 2

As compared with the preceding case, because of a navigation unit that is added to a sensor, the degree of fidelity willincrease. However, in the case of a strap down sensor, in order to stabilize itself, it needs an output from the rate gyrocarried in the airframe. And rate gyros are mostly included in IMU, so this case, that is, a sensor and a navigation unit arethe minimum components for executing the HWIL simulation.

126

Fig.6 Setup of HWIL Simulation Approach

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3.3. CASE 3

it is the integrity in which the 1-IWIL simulation can be executed with real components as possible. And it is the setup inthe last phase of development, or the phase of mass production. The computer would calculate only a motion of the flyingobject and the target.

4. CONCLUSION

In this paper, it is introduced about the outline of our facilities of 1-IWIL simulation. And, a few of kinds of approacheswere showTl focusing on the dual-mode optical sensor. Finally it should be added that three kinds of approaches shownbefore are all executed and components, e.g. a sensor, can be evaluated successfully.

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