Six-Axis Positioning System with Brushless DC Motors and Absolut Encoders: Flat Hexapod for Industrial Automation
By Physik Instrumente
Posted on Feb 08, 2018
Physik Instrumente (PI) GmbH & Co. KG (Germany) – Parallel-kinematic hexapods position in six degrees of freedom and they work with considerably more precision than is possible with serial, stacked systems. In automation systems, the space for integrating the hexapod is usually very limited and multi-shift operations require durable solutions. At the same time, the limited space often increases the risk of collisions; for example, when referencing is necessary after an emergency stop or a power failure and therefore needs to be moved back without being controlled. With the compact H-825 hexapod, PI (Physik Instrumente) now has the suitable positioning solution in its portfolio for these types of applications.
The parallel-kinematic positioning system works with brushless DC motors. These are particularly suitable for high rotation speeds, can be controlled very accurately, and ensure high precision. Because they dispense with sliding contacts, they run smoothly, are wear-free, and achieve a long lifetime. Absolute encoders, which provide clear position information even when powered off, make reference moves superfluous, therefore improving the efficiency and safety during operation. The drives have been "folded" to achieve a compact design. Therefore, the hexapod has a height of just 195 mm with a diameter of 320 mm and it can position loads of up to 30 kg precisely, quickly, and over long operating times. It is suitable for travel ranges to ±27.5 mm and rotation ranges to ±11.5°. The minimum incremental motion is 0.3 μm in the X, Y, and Z axis with repeatability to ±0.1 μm or ±2 μrad.
Typical application fields include for example, microassembly, biotechnology, the semiconductor industry or when aligning optical systems.
Because the cables are compatible with drag chains, the hexapod can be moved in the system without any problems. PI controllers control the hexapod drives. It is also possible to use Cartesian coordinates for convenient commanding of complex motion profiles. The hexapod controllers can also communicate with the higher level controller via EtherCAT®.
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