In this paper, the mechanical structure of an underactuated end-effector manipulator for apple-picking is
presented. The structure is consisted of three identical fingers which are driven by one motor. Each finger is formed by
three joints which are connected with connecting bar and gears. With operation of grasp and twist executed by the driven
fingers, apple-picking action completed. Mathematical model of the mechanical structure is proposed. Kinematics
simulation & optimization software which have a Human-Computer Interaction interface is developed with Visual Basic
visualization platform. Parameters which affect enveloping space mostly are analyzed. With processing and analyzing
data which get from the software, a set of optimum structure parameters are obtained. A sample machine of the Endeffector
Manipulator which is used for testing purpose is designed according to the optimum structure parameters.