Patent Number: 053368940
Section: summary

BACKGROUND OF THE INVENTION The present invention relates generally to a universal infrared heat source controller, and more particularly to a controller for a single infrared source capable of being programmed to act as a target for a missile target seeker. A previous test system in use requires two controllers and two heat sources. Each controller must use its own heat source. It is necessary to switch from the operation of one controller to the other. The switching procedure involves: 1. Removing the heat source that is in the collimating tube and placing it on the provided holding shelf. 2. Unplugging the interface cable from the one controller and plugging it into the one to be used. 3. Performing the recommended calibration after switching controllers. The disadvantage to the system is that it is time consuming and also causes wear on the cabling. The disadvantages to the controllers are: 1. The heat sources are not provided with adequate protection. Heat sources burn up on a yearly basis. 2. Lack of support for repair and calibration of the controllers from the manufacturer. 3. Some of the circuitry in the controllers is unreliable. Repeatability of the controllers is not as good as it needs to be and they need frequent repairs. United States patents of interest include U.S. Pat. No. 4,480,372, to Wirick et al, which describes a target for calibrating and testing infrared devices. Barnett et al, in U.S. Pat. No. 3,960,000, supply energy to a heat source 13 used to test a missile 11. The heat source is operated by a controller 14 connected to a programmer 15. Heat energy impinging on IR cell 17 actuates a detector 18. In U.S. Pat. No. 4,482,252, Lorenz discusses a calibration method and apparatus for optical scanners used to scan cloudscapes or landscapes from above the earth in an aircraft or spacecraft. Operation in the infrared area of the optical spectrum is described. U.S. Pat. No. 4,621,265 to Buse et al describes a simulator array and method for evaluating the tracking capability of a passive target seeker. In U.S. Pat. No. 4,737,792 to Grone, a counter-based simulated target generator is used to generate signals for testing a radar system. SUMMARY OF THE INVENTION An objective of the invention is to correct a heat source problem and to eliminate controller problems. The invention relates to a controller for a single infrared source capable of being programmed to act as a target for an AIM-9target seeker GCS (Guidance and Control Section). It is constructed for operation as part of an automatic test equipment system for testing a guidance and control section of missiles of different types, and can be operated manually or remotely. In either mode the controller is capable of selecting any temperature, aperture and shutter-filter combination. Four different kinds of data are read by the controller, namely (a) temperature data, (b) aperture data, (c) shutter-filter data, and (d) missile ID data. After data is read and decoded by a microprocessor, action is taken on each kind of data by separate circuitry. The unit contains internal protection circuitry for the most critical components. Advantages of the invention are: 1. A single heat source is used to do what the previous system does with two heat sources. 2. The controller is programmable and can accommodate future needs. A new feature relates to protection circuitry for the heat source. The heat source is protected from being over heated by component failure or miscalibration. The controller includes a CPU using a microprocessor, with a program stored in a programmable read only memory. The heat source includes an aperture wheel having a plurality of apertures rotated by a motor. A potentiometer is mechanically connected to the motor and aperature wheel to indicate its position. The controller reads aperture data from the stand, compares the data to digital signals derived from the potentiometer by analog to digital conversion, operates the motor to select an aperture as designated by the data, and then sends an aperature ready signal to the stand. The controller reads missile identification data from the stand. Operation is controlled depending on missile type (AIM-9P, AIM-9L, or AIM-9M). For temperature control, the black body is part of a voltage divider which is one side of a resistance bridge circuit. A voltage divider forming the other side of the bridge provides a reference voltage. A plurality of MOSFETs are used to select a value of resistance to determine the value of the reference voltage. A transistor circuit between a 24-volt power supply and the top of the bridge controls the power to the black body. An instrumentation amplifier is connected across the diagonal of the bridge to compare the reference voltage to a voltage determined by the resistance of the black body, which is a function of its temperature. The CPU reads temperature data from the stand, converts it to a temperature code, and uses it to select the MOSFETs. The instrumentation amplifier output is coupled to the transistor circuit which controls power to the bridge, which thereby controls the temperature and resistance of the black body. When the black body is at the designated temperature, the differential voltage across the diagonal of the bridge and the inputs of the instrumentation amplifier is approximately zero. The CPU reads shutter-filter data from the stand, and uses the data to generate signals to control the solenoids for a shutter and two filters which are part of the IR heat source. The control of the solenoids depends on the missile type. The controller includes a temperature ready circuit coupled to a thermocoupe integrated into the black body for indicating to the CPU whether the black body is heating, cooling, or stabilized. A temperature-ready signal is sent to the stand when the temperature has stabilized. A black body protection circuit opens a solid state relay to disable the 24-volt power supply to the bridge when the thermocouple indicates a temperature of approximately 95 degrees C. The results of testing this circuit shows that the fuse for the 24-volt supply will blow or the black body temperature will be maintained at approximately 95 degrees. A light on the front panel of the controller will indicate the overheat condition.