Testing movements. Innovations move.

Product life cycles are becoming shorter in all areas of industry. New products appear on the market faster and faster. This trend is particularly evident in the automotive sector. While not so long ago it still took seven to eight years before a vehicle was ready for production, today it is just two-and-a-half to three years. This places high demands on the development team. Vehicle functions, such as the frequent opening and closing of the door, must be tested quickly and precisely so that any necessary optimisations can be performed on short order. Powerful drive solutions are required that can be integrated into test systems easily, work reliably and are easy to operate.

Kübrich Ingenieurgesellschaft GmbH & Co. KG develops and manufactures test systems for checking and ensuring the functionality and quality of complex mechatronic units. Together with intelligent software, well-tried hardware and high-precision mechanical components, automatically operating test systems for different tasks are created at the company headquarters in Priesendorf, starting with the testing of electric power windows to automatic mirror adjustment, entire car seats or the like. The new μAct actuator is a typical example, and is used in the testing of sun visors, door handles, various unlocking devices, actuators elements etc..

Micro actuator with a wide performance spectrum

The compact combination of a complete drive in a robust housing, a flexible mechanical interface for coupling, control electronics, bus interface and a hub for connection additional sensor systems is vibration and moisture resistant, which is important for dynamic component testing under climatic conditions. The actuator is available in two versions, because different applications require different forces. Because of the integrated processor, the systems can carry out the movement processes independently in combination with the relevant test software (TiS). Considerable demands are made of the actuator when this takes place. Up to one million test cycles may be necessary depending on the application; this means that reliable functionality in continuous operation over several weeks is mandatory. The components that are used must therefore meet high expectations, be as durable as possible, reliable, and do their job without needing maintenance.

The driving force

Brushless DC-servomotors are therefore the driving force behind the micro-actuator. Quality "made in Germany" was important to the developers at Kübrich, and it is hardly surprising that the choice ultimately fell on microdrives from the FAULHABER product range. They are the right choice for use in testing and test systems, particularly since they are provided as functional drive systems consisting of a motor, gearhead, brake and encoder. The individual drive components are optimally matched to one another, work perfectly together and thus achieve a very high level of efficiency.

A brushless DC-servomotor lasts significantly longer in comparison to mechanically commutated electric motors. It consists of fewer individual components, essentially consisting of a three-phase winding (stator) and a four-pole permanent magnet (rotor) as well as the electronic commutation system. The dynamically balanced rotor provides quiet, cogging-free operation.

The compact combination consists of a drive, a flexible mechanical interface for coupling, control electronics, a bus interface and a hub for the connecting additional sensor systems. (Image: Kübrich)

Compact motor / gearhead combination

In the described application, there are two different types of use for these servomotors depending on the purpose of the test and the torque that is required: For the smaller version of the μAct, the choice fell on the brushless DC-servomotor of model series 2250 BX4. It has a diameter of 22 mm and is a mere 52 mm in length. The four-pole technology gives it a high level of continuous torque of up to 32 mNm despite these compact dimensions, and also has quiet running characteristics and a low noise level. The bigger testing device is also equipped with a four-pole DC-servomotor from model series 3268 BX4 or 3242 BX4. With a diameter of 32 mm and length of 68 mm or 42 mm, these motors achieve torque of 96 mNm or 53 mNm.

Depending on the purpose of the test, the brushless DC-servomotors are combined with a planetary gearhead (model series 22F) that operates with a reduction of 1:25 or 1:51. All parts of these precision planetary gearheads are made from metal, making them ideally suitable for combining with DC-micromotors for applications such as this one that require high output torque. They are simply attached to the motor using a flange that can be screwed onto the front. This creates a compact drive unit which can be easily integrated into the application and requires less space. For tasks which require lower output torque, there is also the option of a plastic version of the planetary gearhead.

The brushless DC-servomotors also demonstrate their reliability in the new micro-actuators for tests in the automotive sector. After all, they have proven themselves in many other applications, starting with medical engineering and camera technology to any kind of automation task, robotics and even in test systems. They cover torques from 0.1 to 217 mNm in different sizes, can be combined with different gearheads, encoders and drive electronics and can also be modified for special requirements. The most frequent adaptations are, for example, vacuum compatibility, extension of the temperature range, modified shafts, other voltage types as well as customer-specific connections or plugs.

Micro-actuator for testing car doors (image: Kübrich)
Up to one million test cycles may be necessary depending on the application; this means that reliable functionality in continuous operation over several weeks is mandatory. (Image: Kübrich)
The brushless DC servo motors are combined with a planetary gearhead depending on the purpose of the test.