A new approach to six degrees of freedom

Traditional hexapod structures are based on parallel motion. A hybrid hexapod combines parallel and serial kinematic structures.

Incorporating new layers of capabilities with traditional concepts of six-legged positioning devices allows the Hybrid Hexapod to combine the strengths of dual kinematic architectures to overcome and exceed previous limitations. Traditional hexapod users face restrictions in travel range, speed, and precision – factors that must be optimal to improve production processes and achieve the levels of efficiency and precision demanded by industry today. With the next generation of motion control devices, manufacturers can achieve sub-micron and nano-levels of precision and increased accuracy.

Traditional hexapod structures are based on parallel motion. A hybrid hexapod combines parallel and serial kinematic structures. Rather than using six legs to create motion, it uses a traditional X-Y stage, a tripod, and a rotation stage to provide 6 degrees of freedom (DOF) in the device. The tripod’s parallel kinematic structure delivers Z-plane and tip/tilt motion, which is integrated with a monolithic serial kinematic structure for X- and Y-motion.

“The combination removes previous application limitations and positioning errors synonymous with traditional hexapods,” says Walter Silvesky, vice president of sales at Alio Industries. “With the Hybrid Hexapod, the precision of serial kinematics combined with the flexibility and compactness of a parallel kinematic device allows users to have all of the strengths of a 6DOF hexapod with none of its critical weaknesses. This key differentiator of the Hybrid Hexapod opens the door for using a 6DOF positioner in several applications not previously considered possible. The Hybrid Hexapod is therefore a true blue ocean technology, allowing manufacturers to achieve the impossible and stimulating innovation at every level.”

A 6DOF positioner can move up, down, forward, backward, left, and right, as well as rotate to face a different axis (pitch, yaw, and roll).

The technology’s increased travel range and working envelope create additional capabilities for its use. It can reach speeds of hundreds, or in some cases thousands of millimeters per second with extremely high acceleration. Also, encoders on all axes allow the user to know where each positioning element on the Hybrid Hexapod is at all points at any time.

Tool center points (TCPs) can be reprogrammed while the device is translating and rotating, just by uploading a series of three commands in real-time. The device does not need to restart and recalculate its kinematic space. A motion controller allows users to control the Hybrid Hexapod by using commands to indicate where to move, when to move, and how fast to move.

Changes in TCP locations are also programmed easily through provided codes.

Aerospace users often incorporate the Hybrid Hexapod in metrology systems. In precision optical elements, the tool can characterize, test, or measure optical components and optical subassemblies. In precision assembly applications such as in the joining of optical image stabilization (OIS) modules to ultra-high resolution CCD arrays, the Hybrid Hexapod can serve as the motion device that manipulates the OIS module in 6DOF space in the alignment and bonding process. The high accuracy of the Hybrid Hexapod decreases assembly time as the OIS is properly placed into a package without time-consuming post-alignment measurements and re-alignment steps.