The Transport Research Laboratories (TRL) in Crowthorne, Berkshire perform a multitude of tests on vehicles of all shapes and sizes. Offering testing services to both vehicle manufacturers and component manufacturers, many of the tests performed involve collisions to measure the forces when a vehicle is involved in an accident.

When TRL wanted to update one of the test rigs it turned to JK Controls Ltd to provide the control and data capture equipment. JK Controls is a specialised control engineering company with a proven track record of supplying control and measurement systems to test laboratories. The scope of supply included a PLC/SCADA-based control system together with data acquisition and logging hardware and software.

The new test rig is designed to simulate the effects of a collision on vehicle components and attachments. Consisting of a sled which is accelerated down a short track (only 20m in length) and crashed into a dampened stop, the rig is designed to evaluate the effectiveness of vehicle sub-systems in a typical vehicle impact. Throughout the set-up and performance of the test, the sled's position must be accurately monitored. JK Controls needed to find a measuring system offering a non-contact method of operation, millimetre accuracy and, most importantly, a fast dynamic response.

The DME5000 laser distance measuring system from SICK proved to be the ideal solution. This system, emits an eye-safe red laser beam which is reflected by a reflector mounted on the sled. The DME5000 uses the time of flight principle to determine the distance to the target. As the DME5000 has a response time of less than 1ms, can operate at a speed of up to 10m/s and produce an absolute positional output with a resolution of 0.05mm JK Controls found this measuring system to be ideal for their application at TRL.

In the TRL application, the DME5000 has two primary functions.

The bungee cords which accelerate the sled down the track are tensioned by pulling the sled up the track using a winch. The position of the sled on the track at the point of release determines the speed the sled will be travelling at the point of impact. Therefore, during the set-up of the test, accurate positioning of the sled using the distance measurement produced by the DME5000 is essential in ensuring that the required terminal speed is achieved. When the sled is arrested one vital piece of information is the total stopping distance. Here, the ultra-fast dynamic response of the DME5000 is vital, enabling the total depth of impact to be precisely recorded.

Now that the unit is installed and in operation, TRL is carrying out tests on various restraint systems, car seats and other vehicle sub-systems to establish their behaviour during impacts. The DME5000 is performing admirably and providing the vital data required to enable component manufacturers to improve the safety of their products. So, while the SICK DME5000 cannot help the crash test dummies at the TRL, it is helping to save the lives of drivers and passengers in tomorrow's cars.