Robots are widely used in dangerous and harsh environments such as military reconnaissance, mine clearance and disaster relief, and nuclear and chemical contamination prevention, as well as in material handling in industrial automated production. With increasing task complexity, the requirements for mobile robots are becoming increasingly intelligent. However, most comprehensive path tracking control methods are computationally complex and difficult to implement. This paper focuses on the design of the walking system of a mobile robot, specifically an intelligent vehicle. Using an MCS-51 microcontroller as the control core, the intelligent vehicle utilizes a single-beam reflection sampling infrared sensor to detect obstacles in front and to the left and right, and employs a control algorithm to find a path, autonomously navigating a maze without human control. The design employs a wheeled movement mechanism, enabling the robot to walk in straight lines and turn left and right. The main focus is on optimizing the path tracking algorithm, proposing an effective and feasible method that is simpler and easier to implement than previous algorithms.
Robots should possess several characteristics: mobility, execution, sensory perception, and intelligence. Currently, there are over 20 robot competitions worldwide, involving hardware and software simulation. These various competitions share a common goal: to cultivate scientific innovation, stimulate imagination, and encourage the integration of theory and practice. Furthermore, increasingly more automated control products are being integrated into production, finding wide application in agriculture and industry. These new working methods significantly reduce manual labor time and physical exertion. The miniature robotic mouse navigating mazes is primarily based on the principle of an Automated Guided Vehicle (AGV), enabling the robot to identify routes, automatically avoid obstacles, and choose the correct path out of the maze. This study focuses on creating a simple movement device to facilitate obstacle avoidance or maze navigation. To achieve route identification, obstacle avoidance, and path selection, a single-beam reflection sampling infrared sensor is used for obstacle detection, a DC motor is used for the drive motor, and an MCS-51 microcontroller is used for the control core. The control system employs time-division multiplexing technology, utilizing a single microcontroller to implement signal acquisition, circuit identification, and motor control functions. The maze consists of 16×16 sections. The starting point is located at a corner, and the ending point is located in the center, occupying four sections. Each section is 180mm×180mm in size, with partitions 50mm high and 12mm thick. The sides are painted white, and the bottom is painted black, as shown in Figure 1.
1. Overall Design Scheme of Maze Car Control System
The maze car consists of wall sensors, a microcontroller control board, a power and steering system, and the control block diagram is shown in Figure 2.
The maze car uses a wheeled locomotion system. Its advantages are simple structure and control, and mature technology. The car's speed can be easily calculated from the selected motor speed and tire diameter. However, factors such as road resistance and uphill driving torque become important. Considering this, the tires are made of plastic, the same material used in wireless remote-controlled cars. As shown in Figure 3, the front wheel 1 is a swivel caster or spherical wheel, while the rear wheels 2 and 3 are independent drive wheels, using their speed difference to achieve steering. This combination is characterized by easy mechanism assembly, and the fact that when the two drive wheels rotate at the same speed but in opposite directions, the car body can rotate around the midpoint of the line connecting the two drive wheels. It is worth noting that the center of rotation is not the same as the center of the car body.
Material selection for the maze car body. Most of the material used in a maze car is for structural purposes, and metal should generally be used. The maze car should not experience severe deformation or breakage under load and during movement; from a mechanical point of view, it should possess sufficient strength. Maze cars have low loads, are lightweight, and do not have high lifespan requirements. Therefore, sheet metal is chosen.
1.1 Design of the maze car control circuit
The control circuit mainly consists of a motor drive circuit, a microcontroller interface circuit, a power supply circuit, and a sensor circuit. The control block diagram is shown in Figure 4.
(1) The infrared light sensing circuit sensor emits infrared light through light-emitting diodes. If there is an obstacle in front, the infrared light will be reflected back and received by the phototransistor. The microcontroller program compares and processes the signal and sends control commands to the two motors of the rear wheel according to the set action requirements to control the movement of the car.
(2) The motor drive circuit uses an 89S51 microcontroller, which controls the two drive motors through an L293D chip. The 89S51 determines the direction of the maze car based on the signal fed back from the infrared sensor after detecting the outside world, and sends control commands to the left and right drive motors respectively. After being driven by the L293D chip, the signal directly controls the corresponding motor to move, so that the maze car moves forward, backward and turns according to the predetermined actions.
