“Experiments have shown that the two robots can correctly complete the chasing action without external interference. This design provides a testbed for studying simple interactions between robots. In the future research, by changing the sensor position and internal procedures, the interaction between the two can be changed, such as collaboration, etc., for further research.
Authors: Wei Junbo; Li Guifeng; Xu Zhiqiang
As one of the greatest inventions of mankind in the 20th century, robots have undergone rapid changes in just 40 years. With the development of computer technology, communication technology, sensor technology, etc., the interaction between robots has become a hot spot in robotics.
In this paper, a robot chase control system based on Motorola MC68HC08 series microcontroller is designed to study the simple interaction between robots.
Mobile Robot Behavior Description
In this system, we name two mobile robots one “cat” and one “mouse”. When the two robots cannot receive the signal from each other, the robot “Cat” moves forward in an S shape, and the robot “Rat” swings 180 degrees in place; when the robot “Cat” detects the signal sent by the robot “Rat”, Chase the direction of the robot “rat” in a straight line, and the robot “rat” receives the signal from the “cat” at the same time, and moves forward in a straight line to avoid the “cat” chasing, until it escapes the receiving range of the “cat”, repeat Behavior when the signal cannot be received; if the “cat” cannot detect the presence of the “rat” for a period of time, an audible alarm is issued. During the whole process, due to the unknown environment, “cat” and “rat” have obstacle avoidance control, and can play different music according to different behavioral states.
System Hardware Design
The circuit designs of the “Cat” and “Mouse” robots are basically the same, and they are both composed of a single-chip microcomputer system, an infrared transceiver module, a motor control module, and a voice module. The difference is the arrangement of the infrared transmitter and receiver tube arrays. The single-chip microcomputer selects Motorola’s 8-bit microprocessor M68HC908GP32 (42-pin package); the infrared transceiver module uses a simple infrared transceiver circuit composed of PT2262 and an amplifier; the motor control module selects L293D for motor drive; the voice module selects ISD25120 to control playback. In addition, the power supply module of the system uses a 12V dry battery.
Single chip system
The microcontroller in the MC68HC08 series is an 8-bit microcontroller launched by Motorola in 1999, which has the characteristics of fast speed, strong function, low power consumption and price.
The MC68H C908GP32 microcontroller we selected in the design is the first batch of MC68HC08 series microcontrollers. It is characterized by rich on-chip resources, high performance, low price, and a variety of protection functions, suitable for various data processing. Platform construction. Here we mainly use it to complete infrared information fusion, motor control and voice playback control.
In the design, the main port settings of the microcontroller on the two robots are the same, as shown in Table 1. In addition, the three contact switches for collision avoidance are controlled as PTB0, PTB6, and PTA7.
Infrared transceiver module
The infrared emission module uses an infrared emission circuit composed of PT2262 and an array of infrared emission tubes. The infrared receiving circuit is composed of infrared receiving tube array and amplifier. The received signal is input to the PTB7 port of the microcontroller, and after A/D conversion, it is sent to the processor to control the behavior of the robot.
Motor Control Module
The motor drive circuit adopts the integrated circuit L293D based on bipolar H-bridge pulse width adjustment mode PWM. L293D has many advantages, such as continuous current; the motor can run in four corners; when the motor stops, there is a micro-vibration current, which plays the role of “dynamic lubrication” and eliminates the dead zone of static friction in forward and reverse; good low-speed stability, etc. The L293D generates the enable signal through internal logic. The input of the H-bridge circuit can be used to set the rotation direction of the motor, and the enable signal can be used for pulse width adjustment (PWM). In addition, the L293D integrates two H-bridge circuits on one chip, which means that one chip can control two motors at the same time.
The robot has three wheels, two are controlled by motors, and the other is a universal wheel, so one piece of L293D can be used for control. Connect the two-way PMW control signals to the enabling pins EN12 and EN34 of the two-way motor control respectively, and the speed of the motor can be adjusted by adjusting the duty ratio of the PWM. Connect the motor forward and reverse control lines to IN1, IN2, IN3 and IN4 respectively, and control the forward and reverse rotation of the two motors by writing different values.
In order to distinguish the different states of the mobile robot, we make it play different sounds while making different actions. In order to achieve this purpose, the voice control part selects the voice chip ISD25120. The recording and playback time of ISD25120 is 120 seconds, and the recording can be divided into 600 segments at most. As long as the address A0″A9 is assigned a value before the segment recording/playback operation (not less than 300 nanoseconds), the recording and playback functions start from the set start address.
System software design
The system software is mainly composed of main program module, interrupt service program module, voice control module and motion planning module. The software part of the whole system is written in assembly language.
Experiments have shown that the two robots can correctly complete the chasing action without external interference. This design provides a testbed for studying simple interactions between robots. In the future research, by changing the sensor position and internal procedures, the interaction between the two can be changed, such as collaboration, etc., for further research.