A Piezo Gripper That Feels What It Is Holding
PI's P-606.1P puts a piezoresistive force sensor inside a monolithic flexure gripper — 4 N of clamping force, 500 µm of jaw travel, and no bearings to introduce play during active alignment.
PI (Physik Instrumente) introduced the P-606.1P piezoelectric micro gripper on 1 September, aimed at photonics and micro-optics assembly. It delivers up to 4 newtons — about 0.9 pounds — of clamping force, with typical jaw travel of 500 micrometres and opening widths from 0.5 to 1.9 millimetres depending on jaw configuration.
The construction is the interesting part. The mechanism is a monolithic flexure with piezoelectric actuation and an integrated piezoresistive force sensor. Flexure guidance means there are no conventional bearings, and therefore no friction and no mechanical play — the gripper deforms elastically rather than sliding.
That matters for the application it is built around. Active alignment requires holding an optical component — a fibre end, a lens, a laser die — rigidly while the positioning system runs a rapid scanning or optimisation routine looking for peak coupling. Any play in the grip becomes position error in the search, and any stick-slip in a bearing becomes a discontinuity the optimiser has to fight. The component must also survive the process: a fibre crushed by an over-enthusiastic grip is scrap, and the margin between too loose and too tight is small.
Putting the force sensor inside the gripper rather than at the robot wrist is the design pattern worth noting. Force measured at the wrist includes the mass and dynamics of everything between the sensor and the workpiece, which at these scales swamps the signal of interest. Measured in the jaws, it is the grip force itself, available fast enough to close a loop around it.
Interchangeable jaws let the interface be adapted to different geometries. PI lists fibre manipulation and active alignment, photonic component assembly, lens and optical alignment, camera and imaging module assembly, optical probing and inspection, and microelectronics assembly as target processes — which is, in effect, a list of the places where automated assembly is currently gated by how gently a machine can hold something.
Source: PI (Physik Instrumente)