End-Effector and Control Logic for Robot

Introduction

In this project, I developed an easily implementable and economic control system for the management of electric drivings. This system shall apply to an pre-existing robot endowed with three axes. In addition, for this robot I have added an axis and designed a flexible gripper that is adaptable to a different workpiece’s shapes.

Mechanics

The robot has three rotational joints which are driven by DC motor (E192).

For the end-effector I designed a gripper that is able to pick up objects with different shapes and dimension, made by a flexible fingers. The gripper is made with polymeric material (PLA) using the 3D printing (FDM).

The gripper is moved by two motors: a servomotor (MG996R) for the rotation on the vertical plane (pitch) and a brushless motor (FIT0441) for the opening/closing of the gripper.

Hardware

The hardware is studied in order to have a modular and economic system.

The three motors DC are connected to the power cards, that are connected to the Arduino UNO board. These engines are equipped with encoder that detect the position and transmit it to the respective Arduino UNO.

The servomotor and the brushless motor, of the gripper, are directly connected to the Arduino UNO.

The brushless motor gives back the angular position, through the encoder, to the Arduino UNO.

All the Arduino UNO are connected to the RaspBerry Pi 3.

The complete control system is composed by planes on a rack.

Software

I have developed a simple program that use a strategy of movement based on manual training, bringing the robot in the positions and memorize it and then execute all the points memorize in sequence.

The software developed in POWER-KI is execute by PowerBerry, that allows to interface with the robot and to control it.

In the interface is present a page of set-up, where for every axis can be regulated the “zero position”, the range of movement, the minimum rotation speed and can be found a reading zone of encoder’s positions.

Once the set up is done there are two choices:

• The first one is filling out a dedicated area with the values of the axis parameters;

• The second choice is manually take the robot in the interested position recording the parameters from the encoders.

Every time that a position is recorded, appears in the interface a line with all the joint parameters and a checkbox for the opening and closing of the gripper. Lots of programs can be recorded.