Measuring viscoelasticity and friction of tempuras for robotic handling

Abstract

Automation in the food industry is not as developed as that in the automotive industry because of the difficulties in handling food products that vary significantly in shape, size, and mechanical properties. Food properties have been studied in terms of product processing, nutrition, and eating. However, the investigation of mechanical properties, such as the viscoelasticity and friction coefficient under different grasping forces and velocities, which are crucial for robotic handling, is currently insufficient. In this study, we propose a measuring apparatus reproducing a robotic grasping scenario and methods for measuring the viscoelasticity and friction coefficient of food materials. The standard linear solid model was employed to represent the viscoelasticity of food materials, and the model parameters were estimated through a grasping test conducted using the proposed method. The friction coefficient was calculated using the measured normal and shear forces during an induced slippage. Finite element (FE) simulation was conducted to validate the friction coefficient calculation. Finally, experimental tests on four kinds of tempuras suggested that the proposed apparatus and methods can estimate the viscoelasticity and friction properties of food materials, and the grasping force, velocity, and contact area influence the estimated properties. • An apparatus was developed to measure viscoelasticity and friction coefficient of food materials for robotic handling. • Approaches for estimating viscoelasticity and friction coefficient of food materials were established. • Experiments on four tempuras were conducted under different conditions of grasping force and velocity. • Results reveal that grasping force, velocity and contact area influence the estimated properties. • Friction coefficient of tempura is 0.3–0.4 at normal force 0.5–1.0 N grasped by robotic hand with flat stainless fingers.