Robotnačka

• Project goals
• Robot description
• Technical specifications
• Images
• Video

The goal of the project is to design a drawing mobile robot as a physical representation of turtle used in the Logo programming environment: Comenius Logo, Imagine Logo. The robot must have its own power supply and allow exchanging of pens. The operation time must be in at least two hours. The communication with computer should be wireless.

Mobile robot Robotnačka is designed to support educational process in connection with flexible environment of Logo developped at Department of Informatics Education at Comenius University in Bratislava. This environment allows the students to use turtle graphics to learn about programming basics. The central concept of the environment is the virtual turtle, which is programmed by the user. Mobile robot Robotnačka is a physical representation of this turtle, and brings the educational process into a new dimension, adds the real-world experience, and makes the programming more fun.

Description:
Robot kinematics is based on the three-wheeler with a independently propelled wheels. The third wheel is supporting and has minimal friction. Robot is driven by MICROCON stepper motors working in unipolar mode with switched cycle pairs to enhance its torque. The robot features accelerating and decelerating component, which pays attention that no steps are lost during the starting and stopping management of the robot. The motor control is in an open-ended loop.
        The central processing unit is the microprocessor ATMEL 89C51, which uses the dual full bridge L298 for both driving the two motors attached to the wheels, and for driving the motor controlling the pen. The pen movement is achieved with bipolar stepper motor with worm gear obtained from a small floppy disk. The limiting positions of the movement are indicated by an optical sensor. The robot contains transmitting/receiving module based on SFH5110 and HDSL4400 and internal charger for its 6V, 4Ah accumulator working in a voltage mode with limiting current.

Short description of communication:
The robot is controlled from Logo using the commands move forward x steps (negative number results in backwards movement) and turn by x degrees (negative number results in opposite direction of turning). The pen is controlled using two commands pd - pen down, and pu - pen up. The commands are transmitted through the serial port of the computer into an IR modem that directs the message to the robot.
        IRmodem has the central role in the communication: controls the data flow to the computer as well as transmission of the commands to the robot, while it allows communication with multiple robots. The data are sent in packets backed by the checksum. The data packets are confirmed by reply packets in a half-duplex communication.

• Three-wheeler with two propelled wheels and one supporting wheel
• Stepper motors MICROCON SL17
• Bip. stepper motor from 3.5" FDD
• 6V lead maintenance-free accumulator, 4Ah
• Wheel radius: 25 mm
• Wheels distance: 184mm
• Height of the base: 90mm
• Base length: 200mm
• Base width: 200 mm
• Number of impulses to turn the base by 360 degrees: 1440
• CPU: 8-bit microcomputer AT89C51
• Infrared transceiver SFH5110, HDSL4400 IR LED

• Notebook 486/100MHz + Comenius Logo software
• IR modem, 12VDC adapter

Click on the pictures to see larger size.