The coefficient of restitution (COR) is one of the microscopic physical properties of maize that must be specified to use EDEM software to perform numerical simulations to support the design of parts used in maize seeding and harvesting machines. Here, the automatic control platform was designed to measure the COR values of irregular maize. Different parts of maize (the umbilicus and different parts of the maize capsule) are involved in the impact on the horizontal zincified plate. Indeed, some parts' designs are difficult to determine without a variety of tests due to the randomness of the impacting parts. In the present work, the effect of each impacting part of the maize on the COR was investigated. Three types of maize particles were studied, including wedged particles, quadrate particles and round particles impacting on the oblique wall. The velocities of the falling maize particles ranged from 2 to 4 m/s. The mechanical behavior of a particle is stochastic and can be traced by a high-speed camera. The normal and tangential coefficients of restitution were quantified based on the modified kinematic equations presented, and the effects of two factors (the impact and rebound angle of maize) on the COR values were analyzed with impact angles ranging from 30 degrees to 90 degrees. Moreover, the effects of the normal and tangential COR on the total COR in oblique collisions were analyzed. Furthermore, the paper presents a method to determine the COR values of irregular particles colliding with a wall obliquely in three dimensions. The study will be helpful for maize simulation and for the design of machines. (C) 2015 Elsevier B.V. All rights reserved.