test bench

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A test stand is a device or a device with which a technical object can be tested for its properties in a reproducible manner. In addition to the mechanical design for accommodating the test object, a test bench also includes the corresponding sensors and controls in order to be able to generate the properties and log measured values .

Overview

Chassis technology test bench, the tire is tested here
Engelbert Zaschka in front of the test bench of his gyrocopter and helicopter, photo from the Federal Archives , 1927

There are two different types of test stands depending on the area of ​​activity:

  • Development test bench
  • EoL test bench (end-of-line test bench)

Development test bench

In development test benches, route profiles, synthetic route profiles or step tests (table with different load levels) that have previously been stored in the vehicle can be run fully automatically. The aim is to run through the load in the vehicle or other relevant test scenarios on the test bench in the shortest possible time.

Development test benches can in turn be divided into:

  • Endurance test bench (components are tested for service life over a defined cycle)
  • Emission test bench (test of an internal combustion engine for its exhaust gas values ​​or compliance with statutory exhaust gas regulations)
  • Climatic test bench ( the behavior of the test object in hot and cold conditions, and possibly moisture, is tested in the climatic chamber )
  • Vibration test bench / strength test bench (testing of mechanical strength in the event of vibration and other mechanical loads)
  • Wind tunnel altitude test bench (testing of aircraft engines)

EoL test bench (end-of-line test bench)

This includes test stands in production, which check the function of the newly built test objects at the end of the production process. They are used for quality assurance and have been given their English name because the test stands are usually located directly at the end of assembly or production lines.

Allocation according to test items

In addition to the division according to the area of ​​responsibility, the test stands are also differentiated according to the test items.

  • Engine test bench / power test bench ( electrical , hydraulic or internal combustion engines are tested or measured. In addition to the engine parameters such as torque and power , other parameters are determined and compliance with the specified parameters (e.g. efficiency) is checked and, if necessary, optimized)
  • Transmission test bench: The transmission or the rear axle are connected to an electric drive machine (replaces the combustion engine) and electr. Wheel machines (substitutes the road) operated. Depending on the type of drive, there are 3E test stands (rear or front axle drive) and 5E test stands (all-wheel drive).
  • Vehicle test bench / roller test bench (the entire vehicle runs on a special drive roller and driving cycles of the vehicle are simulated). The overall properties, including the losses in the drive train such as the gearbox, drive shaft and bearings, are also measured. The homologation tests (approval tests) including exhaust gas measurements are usually carried out on a roller dynamometer.
  • Engine test bench (testing of aircraft engines)
  • Component test bench (testing of geometries, load-bearing components, structural components, joints)

General

There are different versions of the listed types and very often there are also combinations of the different types. With the exception of the roller dynamometer, they all have in common that the test item is rigidly connected to a performance brake ( water vortex brake , eddy current brake ) or a corresponding drive. Depending on requirements, the drive accelerates the motor (e.g. a DC machine works as an electric motor) or brakes (e.g. a DC machine absorbs the motor energy and works as a brake), whereby the torque , speed and other motor parameters are continuously measured . From these, in turn, the engine power can be calculated.

Working method

control

The test bench is usually controlled by a real-time computer, also called an automation system.

  • This gives the control system the setpoints (speed and / or the counter torque to the brake or to the motor and other variables).
  • The automation system receives the resulting variables as reactions of the test object (motor, gearbox, etc.) from measurement sensors on the test bench (torque, speed, temperature, pressure, volume flow, etc.).
  • The entire speed range of the test item in question is measured in this way.
  • The target values ​​and the measured values ​​of the test object are graphically displayed on the computer and stored for later evaluations.
  • Almost all characteristics of a test item can be recorded and checked.

Multiple machine control (depending on the test setup)

This has the task of regulating the setpoints and then specifies their setpoints for the individual machine controllers. The laws of control engineering must depend on the test setup (e.g. for a transmission with a drive machine and 2 load machines, a decoupled multiple machine control is required so that the mechanical system on the test bench behaves almost identically to the mechanical system on the vehicle)

Machine control

The machine control receives the setpoints and converts them into manipulated variables for electrical actuators. Nowadays these are mostly IGBTs, which then use the electr. Apply electricity to the machines.

Test bench machine

This is mostly about

  • Electric motors
    • Asynchronous (most common)
    • Synchronous motors (for highly dynamic test stands and those with very little space for the electric motors)
    • DC motors (seldom in new projects due to increased maintenance)

See also

Test field