Hypersonic Sensor Architecture Evaluation, Sensor Testing and Communication Needs

Flight test and on-board monitoring systems require multiple and different types of measurements, including pressure, temperature, heat flux, strain, flow position, vibration, and shock. As many as four to six wires from each sensor carry analog signals and power to and from the analog signal conditioning. For large numbers of sensors, this will mean large numbers of wires that add weight and occupy significant space. Traditional analog transducer systems result in large, long bundles of cables carrying analog signals that are difficult to manage and are susceptible to EMI/RFI noise pick up. Low-level sensor signals often require special shielding and elaborate grounding schemes. Flight testing of future hypersonic vehicles compounds the above mentioned instrumentation challenges by requiring light weight, small volume hardware with harsh operational environmental requirements. The instrumentation must survive the high temperature and high vibration generated by the hypersonic speeds and aircraft maneuvers. The sensor technology to perform the needed measurements on hypersonic vehicles is readily available. What are lacking are the ruggedized sensors and system components that are able to operate under the harsh environmental conditions, as well as an effective system architecture that drastically reduces volume and weight requirements. VIP Sensors proposes to design a new ruggedized measurement system architecture that processes signals from multiple sensors and sensor types distributed throughout the hypersonic vehicle, to store the processed data at the transducer, and to transfer real time data to a central data storage unit or telemetry system. The system is based on networked digital sensors and highly integrated electronics technology. The proposed system consists of smart sensors, postage-stamp size interface modules (IBIM) that convert traditional analog sensors to smart ones, and a network interface controller (NIC) that controls the transducer digital bus and sends data to a COTS telemetry system and Ethernet-based systems. Smart Sensors contain embedded analog signal conditioning and digital signal processing. They each interface with a digital network communication bus to form a multi-drop sensor measurement system. Small interface modules (IBIM), containing all of the electronic functions of a smart sensor, are used in those applications where temperatures of the transducer exceed the operating range of electronics circuits, or the transducer size limitations do not allow integration of the electronic functions. Smart Sensors and IBIMs have an onboard microprocessor, which allows them to function as stand-alone, distributed sensors and control nodes. They not only sense and process the signals, but also, based on the results from running local software algorithms, control actuators and switches. This practical feature increases the flexibility and attraction of the proposed system architecture. The Network Interface Controller is the master of the digital network. It provides DC power to the IBIM’s, and it also has the option to provide to the IBIM a synchronization signal to achieve synchronous/simultaneous data sampling among all the IBIM’s on the digital transducer bus. Smart Sensor systems offer highly desirable attributes, especially when dealing with large numbers of measurement channels, such as: elimination of traditional bulky analog signal conditioners and data acquisition boxes (less weight and volume); reduction of cables and interconnects (network instead of point to point wiring); increased reliability; improved EMI performance by transmitting digital signals instead of analog; improved Signal to Noise Ratio; common interface with multiple sensor types; lowered integration costs and lowered overall system cost. In Phase I, VIP Sensors accomplished the following objectives: (1) developed small ruggedized packaging concepts for sensors and other system components to be able to operate under the demanding hypersonic flight environmental conditions; (2) defined technical system characteristics such as sensor accuracy, bandwidth, data acquisition rate, sampling schedule, self-test, time synchronization among different measurements, etc.; (3) built a prototype measurement system with COTS components that proved the proposed smart sensor architecture concept; and (4) provided a detailed product development and commercialization plan. In Phase II, a flight-worthy prototype system will be developed, built and tested at Wright-Patterson’s Test Cell. It will be comprised of: 1) low frequency IBIM modules to interface with voltage or full bridge types of transducers such as flowmeters, thermocouples, strain gages and pressure transducers, 2) 3-channel Charge/IEPE IBIM modules to interface with Piezoelectric, integral electronics PE (IEPE, Isotron, ICP, etc.), and velocity coil types of sensors that are commonly used to measure vibration and dynamic pressure, 3) a Smart Accelerometer, which consists of a MEMS accelerometer sensor element in an IBIM package, 4) a Network Interface Controller (NIC) to control the transducer bus activity and provide a convenient Ethernet-based interface to a PC, and 5) a PC-based application software that provides a graphical user interface for system setup and data acquisition activities.