Compliant touch sensors give robots an adaptive grip
Spun out from Budapest’s Pazmany Peter University in 2013, the company was initially founded while doing research on walking robots, explained Akos Domotor, the company’s CEO.
“Two of my colleagues were doing a PhD with a special focus on sensing robot gait, trying to measure leg inertia and detect foot slip with largely varying forces. We came up with a first prototype in 2012, and after thousands of iterations, we were able to optimise our sensors into their actual dome shape with a very linear output”, Domotor said.
The optical force sensors have a very simple construction, consisting of a silicone dome covering a central LED and four light sensing elements measuring the light reflected by the dome. By construction, any deformation of the dome along its X, Y or Z axis (through external pressure) will yield a different set of values across the photodiodes.
After a thorough calibration of the sensor, these values can be translated into precise forces values, giving not only force magnitude but its direction, so a simple joystick could be designed out of a single sensor. The company also designed a 6-axis force/torque sensing unit based on an array of such sensors. Correlating the force direction across all sensors gives the overall torque.
The sensors can be designed with various dome sizes of different thickness or made up of different silicone materials (of varying hardness) depending on the final application requirements, say for harsh environments, but the algorithm running to interpret the data is the same as long as calibration has been performed. So in essence, because the electronics is protected by the deformable dome, they are very rugged.
“Applying just the right gripping force to soft or fragile objects without knowing their shape in advance, and preventing slip without exerting too much force has been a research topic in academia for quite some time, but so far, practical solutions were not mature enough to be used in industry”, told us Domotor.
The company has been working on integrating these dome sensors into robotic hands and is already break-even selling its sensors mostly to academic research centres.
“Compliant touch and smart grippers for prosthetics or for home assistant robots represent a very nascent market, and although it may be the biggest potential market for our technology in the future, we are now focusing on industrial applications were our solution is several orders of magnitude cheaper than today’s strain gauges costing from 5,000 up to 20,000 euros”, commented Domotor who sees small and medium enterprises the real business driver.
“A lot of small and medium enterprises would want to use 6-axis force sensors for automation, but often they don’t have the budget. Companies like Danish firm Universal Robots are working on making robots more versatile and cheaper and we see a big potential here”.
“So we are integrating our 6-axis force/torque sensor into robot arms, at the swivel joints between the robot hand and the tool, so for example a robot could exert a constant grinding or polishing pressure across uneven surfaces and contours” concluded Domotor.
Visit Optoforce at https://optoforce.com