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Drive Train System Testing
In order to conduct subscale component and system level testing for drive train system we have developed several testing systems.

Mechanical Diagnostic Test Bed:The Mechanical Diagnostic Test Bed (MDTB) consists of a 30 HP AC variable speed drive motor and a 75 HP AC load motor to simulate loads on the gearbox at variable torque levels as shown in figure 2.

 
Figure 2: Mechanical Diagnostic Test Bed

The test gearbox is instrumented with input and output torque cells to monitor the loading conditions throughout the test cycle.  The MDTB has been instrumented with a variety of sensors including accelerometers, high resolution rotational speed encoders, thermocouples, acoustic emission sensors, and oil debris sensors.  Seeded fault and transitional run to failure tests have been conducted for gear, bearing and shaft faults on this test system.

Shaft Crack Prognostics Testing System: The shaft crack prognostics testing system consists of a 30 HP DC drive motor and a 75 HP DC motor load motor as shown in figure 3.

Figure 3: Shaft Crack Prognostics Testing System

The shaft is instrumented with a variety of high resolution rotational speed encoders, torsional vibration sensors, accelerometers and displacement transducers.  The shaft can be seeded with a small surface crack/defect and radially loaded while the shaft is rotating at operational speeds.  The crack propagation can be tracked over various speeds and loads which enables the development of prognostic shaft failure techniques.  

Bearing Prognostics Testing System: The bearing prognostics testing system consists of a 2 HP DC drive motor with roller element  bearing support structure that allows for the radial loading of the bearing as shown in figure 4.

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Figure 4: Bearing Prognostics Testing System

The loading mechanism is instrumented with a load cell and the bearing is instrumented with vibration transducers for diagnostic and prognostic technology development.  The bearing can be seeded with a race spall, element spall or cage defect and radially loaded while the shaft is rotating at operational speeds.  The crack propagation can be tracked over various speeds and loads which enables the development of prognostic bearing failure techniques.

Gear Testing Systems: The Drivetrain Technology Center (DTC) at the Applied Research Laboratory is equipped with a comprehensive capability to evaluate gears and gear materials.

 
Figure 5: High Speed Power Re-circulating Test Rig

This equipment can be utilized for conducting baseline and some fault gear testing.  Several power re-circulating  test rigs are available for low speed and high speed gear testing. Utilizing a 4-square kinematic mechanism, the load on the gears is obtained by applying a torque on the test gears against a pair of reversing gears.  The motor driving the test rig has only to provide for the frictional losses in the kinematic mechanism.  Low-speed (speeds up to 3000 rpm) test rigs are generally utilized for rotating bending fatigue tests and are configured for a 4 inch center distance. Other center distances can be tested with modifications to the rigs. High speed (speeds up to 10,000 rpm) test rigs are utilized for contact fatigue and scoring resistance tests.  Two high speed rigs are available with 3.5 inch center distance and one high speed test rig is available with a 6 inch center distance.  Figure 5 shows two of the high speed tests stands.

Diesel Engine and Fuel System Testing

In order to conduct component and system level testing for diesel engine and fuel systems we have developed two testing systems.

Diesel Enhanced Mechanical Diagnostic Test Bed: A test cell for performing transitional and seeded fault research on areciprocating engine and mechanical drive train parts is a key enabler towards the development of diagnostic and prognostic capability.  The Diesel Enhanced Mechanical Diagnostic Test Bed (DEMDTB) system is capable of generating diesel engine operational data at the component and subsystem level under variable speed and load conditions.  It provides the opportunity for conventional and advanced sensing techniques on real machinery in a controlled environment.  The DEMDTB provides two methods of driving forces for testing: electric motor or diesel engine.  A block diagram layout of the DEMDTB in the diesel engine drive configuration is shown in figure 6a and 6b.

Figure 6a: Schematic of Diesel Enhanced Mechanical Diagnostic Test Bed

The DEMDTB provides accurate torque and speed information via torque cells and shaft encoders mounted on the drive and load shafts.  Secondary torque and speed measurements are also provided from the electric motor controllers.  The 1.7-liter 4-cylinder Isuzu diesel engine provides a continuous output of 36.1 bhp @ 3000 rpm with a maximum rating of 80.0 ft-lbs @ 1800 rpm.  This test bed provides an effective means for studying health indication parameters for a representative diesel engine.  Seeded faults in the diesel engine may include excessive wear on piston rings and valves or a cracked crankshaft and lifter rods.  While the DEMDTB provides a mechanism for developing diesel engine diagnostics, the test bed can also provide the means for testing different types of gearboxes and other mechanical devices

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Figure 6b: Picture of Diesel Enhanced Mechanical Diagnostic Test Bed

Bradley Fighting Vehicle - Fuel System Test Bed: In order to develop and evaluate embedded diagnostic and predictive fuel system technologies and techniques, a U.S. Army Bradley Fighting Vehicle fuel system test bed was designed and built.  The test bed consists of one fuel tank, four in-tank fuel pumps, a fuel filter separator, and a pressure-time (PT) fuel pump/governor with integrated air-fuel control (AFC) valve.  All of the components except for the fuel tank and the fluid conduit are components from the vehicle and are configured in the same sequence as they are on the platform.  On the test bed, fuel enters the in-tank fuel pump and continues through the fuel filter separator to the PT pump which is directly driven by a 30 HP AC electric motor.  The PT pump leakage and fuel supplied to the needle valve are returned directly into the sump tank to form a continuous closed loop non-combusting fuel circuit as shown in figure 7.

For fault induction and component isolation purposes, three sets of two-way ball and bleed valves graphically depicted as yellow cubes in figure 3 (drawing-left) are incorporated into the test bed fuel circuit to re-route fuel directly back to the sump tank as needed.  There are also three sets of flow meters, pressure transducers and thermocouples co-located in three segments of the fuel circuit with the valves

 
Figure 7: Bradley Fuel System Test Bed – (drawing - left) and (picture - right)

The valves, flow meters, pressure transducers and thermocouples are located at the following locations:         

• After the in-tank fuel pump and before the fuel filter separator
• After the fuel filter separator and before the PT pump
• After the PT pump and before the needle valve

Additional collection instrumentation includes voltage and current sensors for monitoring the in-tank pump power, a triaxial accelerometer mounted on the PT pump, and a torque cell measuring both torque and speed of the drive shaft to the PT pump.

Structural System Testing

The primary focus of the structural integrity heath management technology development has been for helicopter structures.  To support the research efforts for this area several test beds have been designed and built including a plate (skin mock-up) test bed, structural member (frame mock-up) test bed and full scale integrated helicopter skin and frame test bed.

A versatile steel framed fixture was developed for use with the multiple test structures.  The frame depicted in figure 8 is a massive steel fixture which provides stable boundary conditions.  The simple plate, stiffened plate, and helicopter transmission frame structure can all be mounted in the test frame / fixture.

Figure 8: Experimental test bed. (left) CAD model showing the fixture and the adjustable support to mount the shaker, (right) Photo of the actual test bed showing an aluminum test plate installed.

Out-of-plane external dynamic excitation can be provided using an electrodynamic vibration shaker (positioned with / mounted on the adjustable support), and in-plane excitation is provided through the use of PZT actuators mounted directly on the test structure.

Dominant energy sinks (dissipative mechanisms) can be added through the use of attached constrained layer damping beams (CLD beams) or through the use of an Active Energy Sink (AES).  The AES is implemented using a second shaker or PZT actuator and a separate real time control system based on velocity feedback control.  Drive forces / accelerations, response accelerations, and response strains can be recorded using a National Instruments data acquisition system. 

Structural Member Test Bed:The frame mock-up test beds were developed to facilitate the transition of techniques and technolgies from simple test beds (plate-like structures) to flight like structural components.  The frame mock-up (see Figure 9) was intended to simulate the UH-60 helicopter joint FS360-BL 16.5 which is a typical structural component of interest for this research. The test bed, although not a scaled version, includes the relevant structural features characterizing the flight structures (note all tests structure materials are Aluminum Alloy 6061-T6).

Two different versions of the frame mock-up were developed. The first version was assembled using flight-rivets and was used for preliminary testing. The second test bed was assembled using machine screws and was intended to be used in destructive testing, including loosened / missing strap fasteners and fatigue cracked straps.

Full Scale Helicopter Structural Test Bed: Structural testing can be conducted on an actual UH-60 helicopter structure shown in figure 10.  Previous testing has been implemented with an impact resonator near/on a critical transmission frame joint to generate a damage like vibration signature.  Developed methods have been implemented on the structure and detection performance evaluated.  Preliminary vibration measurements (experimental modal analysis) have been conducted to characterize the UH-60 test structure resonance frequency and damping content.  This information can be used for aiding the design of the SHM systems for flight ready hardware.

Figure 9: Transmission frame critical joint mock-up (cruciform test structure mounted in test frame)

Figure 10: Upper cabin UH-60 structure including the main rotor transmission frame

Electrical Power System Testing

In order to conduct component and system level testing for electrical power systems we have developed several testing systems.

Battery Prognostics Test Bench: The battery prognostics test bench as shown in figure 11 was built for the development of prognostic technology for primary & secondary batteries under funding from the Office of Naval Research. 

This test bed provides us with the ability to tailor and train our battery prognostic technologies over a range of operational temperatures and electrical loads as well as for the specific battery type used for the platform application.

Generator Diagnostics Test Bed: A synchronous generator test bed was developed to support electrical power health management technology development. The test bed consists of a Kato Engineering, Model A267890000, 5 kW, 3-phase, 60 Hz, synchronous AC generator as shown in figure 12.

Figure 12: Synchronous Generator Diagnostic Test Bed

The drive motor is a Kato Engineering, Model D267880000, 7.5 HP, synchronous, brushless, DC motor, which is a scale model of the 501-K34 electrical generator used to provide ship’s service electrical power onboard U.S. Navy warships. The generator has been customized to allow for the testing & analysis of seeded faults such as shorted stator windings, faulty rectifier diodes and bearing fault and it is also equipped with a 3 phase load bank for analysis of step loading changes for each phase of the generator.  The test bed is instrumented with current sensors, voltage sensors and vibration transducers. 

Ground Vehicle Hardware-in-the-Loop Test & Evaluation Bed: This hardware in the loop test bed (shown in figure 13) simulates large ground vehicle diesel engine and internal combustion engine starting cycles under a wide range of conditions in order to evaluate performance of engine starters and energy storage devices.

Figure 13: Ground Vehicle Hardware-in-the-Loop Test & Evaluation Bed

  The test bed has electric motors for assist/opposition torque that is used to emulate the various engine configurations such as engine size, various number of cylinders and temperature conditions.  It is instrumented with load cells, current and voltage sensors and the system is operated with a dSPACE control system that utilizes Matlab Simulink models for different vehicles.  The primarily use for this system is to evaluate starters and electrical power storage systems for performance verse engine size and temperature conditions.  This testing is leverage for gathering baseline and some fault data for starter and battery health management technology development.

Ground Vehicle Alternator Test Bed: This test bed includes a 60 HP, 3600 RPM induction motor to drive the alternator with a 28 Volt, 400 A DC load bank operated with dSPACE microcontroller as shown in figure 14.  

The bed is instrumented with current sensors, voltage sensors, and vibration transducers.  The primarily use for this system is to evaluate alternators for performance verse various speed and temperature conditions.  This testing is leverage for gathering baseline and some fault data for alternator health management technology development.

Figure 14: Ground Vehicle Alternator Test Bed

Electronic System Testing

Power Electronics Test Bench: This test bench was developed to support the development of power electronic fault detection and prognostic techniques.  The test bench as shown in figure 15 includes an AC load bank, DC to AC inverters and switching power supplies, a DC power source, data acquisition system, thermal chamber and power electronic device for testing.

This test bench supports the development of diagnostic and prognostic models for the packaging of high temperature, high power silicon carbide (SiC) power devices, and is also be designed to accommodate testing and analysis of electronic power converters.

Robot Testing

ARL Penn State develops health management technology for robot applications and several different robots have been acquired for testing including: Packbot, Talon, Andros and several smaller robots that have been developed at the laboratory. The primary focus of the robot health management technology development has been on batteries prognostics and manipulator arm fault detection.

  
Figure 16: Packbot (left) & Battery Diagnostics Development for Talon Robot (right)

Full Scale Test Platforms

ARL Penn State also has several full scale military vehicles including a Marine Corps Medium Tactical Wheeled Vehicle (MTVR), and a Heavy Expanded Mobility Tactical Truck (HEMTT) that are on loan from the Department of Defense for the implementation and demonstration of advanced diagnostic and prognostic technology as shown in figure 17. 

ARL Penn State platforms are instrumented with embedded vehicle health management systems that support both low bandwidth and high bandwidth capabilities for multiple sensors including current, voltage, pressure, temperature and level as well as vibration transducers.   These test beds provide us with the ability to train, test, verify and validate diagnostic and prognostic technology that has been developed for mechanical, electrical, electrochemical and structural applications in an operational environment.

Figure 17: Heavy Expanded Mobility Tactical Truck (HEMTT) and Medium Tactical Wheeled Vehicle (MTVR) and Health Management Technology Test Vehicles

To facilitate development and implementation of health management technology, advance concept vehicle health information displays have been developed for the ARL Penn State test benches and platforms as shown in figure 18.

These test beds and vehicles show our ability to manage and operate small to large scale test bed systems and equipment.