Robot Car Design Competition
Introduction
This is the 7th Electronic Design Competition of Tsinghua University in 2005. Contestants are required to design both the hardware and software parts of a robot car to complete specified tasks. Before the car reaches the entrance of the field, it needs to pass a track that has several turnings. After the car enters the field, which is in the scope of a camera, it should try to push as many boxes as possible to the goal. The instructions for the car are sent by a remote PC according to the recognized map information.
Framework
The whole system consists of three main parts — circuits design, MCU programming and decision program run on the remote PC. The circuits design contains driving module which controls the car's movement and speed, and RF module which communicates with the remote PC. The MCU generates control signals for the driving module as well as PWM output to provide several different gears. Meanwhile, it deals with the feedback of the sensors for turning detection through interrupt service. The decision program takes the recognized map information as input parameters and decides what the car should do next. As the captain of the team, I was in charge of the first two parts while my teammate wrote the decision software.
Design
I used AT89C2051 MCU and L298 Chip for design of the driving module. The schematic and pcb pictures are as follows, drawn in the Altium Protel software.
The Innovation Laboratory in our university has a simple processing equipment for making single-layer PCBs. So the whole PCB was made all by myself. For the RF module, I basically made it according to the instructions provided by the competition committee, used PT2262 encoding chip connected to the PC and PT2272 decoding chip installed in the car. The communicating data was limited to six bits per round.
The MCU adopts the regular power-on reset circuit. To detect the turnings before entering the field, I installed three collision switches beyond the head of the car in the left, middle and right direction. A electric pulse resulted from a collision will trigger the external interrupt service of MCU and then change the moving direction of the car. The receiving data via RF communication are also processing through interrupt service mechanism.