Closed-Loop Shape Control of a Haptic Jamming Deformable Surface

A Haptic Jamming tactile display, consisting of an array of thin particle jamming cells, can change its shape and mechanical properties simultaneously through a combination of vacuuming individual cells, pressurizing the air chamber beneath the surface, and pinning the nodes between the cells at various heights. In previous particle jamming devices for haptics and soft robotics, shape has typically been commanded open-loop or manipulated directly by a human user. A new algorithm was designed for the three types of actuation inputs for a Haptic Jamming surface, using the depth map provided by an RGB-D sensor as shape feedback for closed-loop control to match a desired surface input. To test the closed-loop control accuracy of the system, a mass-spring model of the Haptic Jamming device generated three unique surface shapes as desired inputs into the controller with a mean height range of 25.1 mm. The average correlation coefficient between the desired input shape and the experimental output generated by the controller on the actual device across four trials for each shape was 0.88, with an average height error of 2.7 mm. When the desired input surface is generated from a 3D model of an object that a Haptic Jamming surface cannot necessarily recreate, the difference between the input and the output increases substantially. However, simulation of a larger array suggests that a Haptic Jamming surface can provide a compelling match for these more complicated shapes.