Birgit Schulze reveals how hexapods enable higher precision for industrial applications
Automated production and quality control processes are becoming increasingly complex, requiring new solutions to achieve the precise multi-axis movements necessary for everything from automotive vehicle assembly to wafer testing in silicon photonics. Parallel-kinematic hexapods provide a number of advantages over traditional multi-axis robots: superior path accuracy, repeatability and flatness compared to industrial robots.
Multi-axis movement has been critical to the ongoing development of robotics, but these systems typically rely on serial set-ups, such as stacked stages or robots consisting of multiple links connected by motor-actuated joints. These devices allow movement in six degrees of freedom, but do not always offer the precision or flexibility required for the manufacturing of complex components or the positioning of inspection and calibration systems.
Hexapods – parallel-kinematic positioning systems consisting of six independent, actuator-controlled struts – offer a potential answer to this issue. These robots are able to position loads up to several tons in weight with micrometre precision and are suitable for handling the smallest components. All six struts of the hexapod act directly on a single motion platform, which eliminates the accumulation of guiding errors associated with serial set-ups and improves precision. This offers a much better ratio of payload to operating weight.
Easy to use
Input commands for movement and positioning are expressed in Cartesian coordinates, and a digital controller handles the complex transformation algorithms, controlling the six struts in real time. The variety of components and controller languages in the automation industry makes seamless communication between devices quite a challenge. The use of standard protocols such as RS232 and TCP/IP, as well as fieldbus protocols such as including EtherCAT, makes it easy to integrate them into any automated environment.
Automotive Industry Adoption
The automotive industry was an early adopter of industrial automation, pioneering the use of robot-assisted and fully robotic assembly lines. Today, hexapods are often used as standalone devices in prototype manufacturing or quality assurance processes, or combined with existing industrial robots to allow more accurate small-scale movements. They are ideally suited to collaborative working in a semi-automated environment bearing heavy loads, as well as the assembly of small automotive parts requiring complex manipulations.
Hexapods In Mobile Phones
Manufacturing of camera-equipped smartphones is another area where hexapods are in routine use. The lenses that form the basis of the camera hardware must be carefully and precisely aligned in order to create a single optical axis – to produce a sharp and clear image – then brought into precise orientation with a CCD or CMOS sensor chip and glued together.
Hexapods are also playing a role in mobile phone software development. Improving image stabilisation algorithms is a key focus for many mobile developers, and hexapods are used to create defined, replicable vibrations. This simulates the natural tremors in a user’s hand, allowing a scientific approach to test image quality.
Silicon Photonics – Active Alignment
The highly complex process of wafer probing requires the precise, contact-free coupling of optical fibres for assessment of numerous parallel optical parts with interacting inputs and outputs. One proven solution (from PI) for fast photonics alignment combines firmware-based routines for simultaneous optimisation, a hexapod and an additional piezo XYZ stage for nanometre resolution and high-speed scanning.
Birgit Schulze is with PI