Integrated design of a bio-inspired soft gripper for mushrooms harvesting

In this paper, an integrated design of a soft gripper is described for an efficient mushrooms harvesting. The soft gripper is made up multi-phalanges soft fingers in order to address the shape adaptability issues regarding the form enclosure grasping strategy. The shape kinematics of these soft fingers has been described using parametric curves, namely the Pythagorean Hodograph (PH) curves, with a prescribed length. This has enabled a Reduced Order Modeling (ROM) by using a few number of geometric control points. Then, Euler-Bernoulli (EB) modeling technique has been applied to these curves to estimate the actuation control inputs, allowing the mushrooms to be grasped under optimal safety conditions. The real-time grasping control issues based on the sliding Mode, have been discussed using a combined action of the attractive and repulsive Artificial Potential Field (APF), used to drive the soft gripper to the mushroom target. This control has been applied to the virtual control points of their representative PH curves, and yielded an accurate positioning of the soft gripper during the grasping process. The safety and the quality of the mushroom during the harvesting has been guaranteed by the presence of the contact force sensors, as well as the hyper-elastic material constituting each soft finger. The above strategy keeps the harvested mushroom safe during the grasping and therefore, enables a real-time shape control for a form enclosure soft grasping. The results of the proposed technique have been experimentally assessed using a 3-fingers soft gripper made up of Fluidic Elastomeric Actuators (FEAs) in an agriculture fresh mushrooms farm.