Using three three-phase current generators and three respectively assigned adapter gear boxes, the speed and torque values that occur in the vehicle are simulated for both static and dynamic processes.

The test specimen can also be stressed beyond its design torque to reduce the testing time. The wear and tear of teeth and the pitting of gear cogs can be specifically tested.

The test rig is also suitable for developing new rear axle gears due to its flexible control and automation concept.

Test rig design

The test rig is set up on three torsion-free base frames fixed to each other in a "T-cross" and basically consists of the following components:

• Drive unit, consisting of an externally ventilated three-phase current generator, a water-cooled planetary adapter gear box with transmissions 1:1 and 1:6 and a torque measuring flange.
• Two load units, consisting of an externally ventilated three-phase current generator and a water-cooled planetary adapter gear box with transmissions 1:3 and 1:18.
• Truck rear axle gear (test specimen) with oil conditioning device. The device is suspended (as in a truck) on a test specimen console which can be moved in X and Y direction. The test specimen is connected by jointed shafts with length compensation.

The speed and torque are measured directly on the test specimen by digital shaft encoders and a torque measuring flange.

The following safety devices are provided to protect the test rig and the test specimen: total speed monitoring through the control and vibration monitoring of the test specimen and emergency bearing for the jointed shafts and slip clutches.

The performance of the test rig is driven in a circle for the three three-phase current drives via a common DC intermediate circuit of the SIMOVERT converter. This gives an approximately halved connection rating. The reactive power requirement of this design is negligibly small in comparison to a solution with DC drives.

Technical Data

The control is fully digital so that an optimized, reproducible control parameter set can be stored for every gear and every test specimen. The drives are driven in the following control types:

• Drive unit: torque
• Wheel load units: speed
• Differential speed control of the two load units (0 for straight and e.g. delta-n left/right = 1 min-1 for bends).

The control covers all modern strategies for improving the dynamic such as:

• Pre-control
• Control circuit disconnection
• Adaptation and torsion vibration damping

Operation

The test rig has two operating options:

• Manual mode by means of two digital setpoint potentiometers and one operator panel with graphic display in which operating masks can be selected by function keys that enable user-guided control, monitoring and parameterization of the test rig.
• PC mode with the CATS PC systemNT under Windows NT 4.0 for fully automatic testing with setpoint presetting as well as measured value acquisition, display, online classification of measuring results in multi-dimensional matrices, storage and limit value checking.

The test programs can be created, changed or extended as you like. The operating dialog is via the monitor, keyboard and mouse. PC mode requires minimum personnel and supports continuous testing over several weeks with high reproducibility and reliability for the test rig.