Aiming at the process of autonomous mobile robots' navigation along the wall, a detection system consisting of a transceiver-integrated ultrasonic sensor and a stepper motor is designed. Introduce the structure and hardware and software design of this system. The experiment summarized the influence of the size of the incident angle of the ultrasonic beam and the target on the stability of the ranging. The method of searching for the closest point from the wall was proposed and applied to the correction of the pose of the mobile robot itself, and it was applied to the environmental detection of the mobile robot.
One of the most important tasks for mobile robots to gain autonomous behavior is to acquire knowledge about the environment. This is achieved by measuring with different sensors and extracting meaningful information from those measurements. Vision, infrared, laser, ultrasonic and other sensors have been applied in mobile robots. Ultrasonic sensors have been widely used in the mobile robot sensing system due to their high cost-effectiveness and simple hardware implementation. However, ultrasonic sensors also have certain limitations, mainly due to large beam angles, poor directivity, and unstable range measurement (in non-vertical reflections). Therefore, multiple ultrasonic sensors or other sensors are often used to compensate. In order to make up for the shortcomings of the ultrasonic sensor itself and improve its ability to obtain environmental information, this paper designs a detection system consisting of an integrated ultrasonic sensor and a stepper motor.
The basic principle of an ultrasonic sensor is to send an (ultrasonic) pressure wave packet and measure the time it takes for the wave packet to transmit and return to the receiver.
Where L is the distance of the target from the ultrasonic sensor; c is the ultrasonic wave velocity (for simplicity of explanation, the distances discussed in the following discussion do not consider the velocity of the wave affected by the temperature); t is the time interval from transmission to reception.
Because measuring distance with ultrasound is not a point measurement. Ultrasonic sensors have a certain diffusion characteristics, and the emitted ultrasonic energy is mainly concentrated on the main lobe, wavy attenuation along both sides of the main wave axis, and a diffusion angle of about 30[deg.]. In fact, the more time-efficient the calculation of equation (1) is based on the success of ultrasound, the vertical reflection in the name. However, it is difficult for the mobile robot to ensure the stability of its own motion posture. The ultrasonic sensor is used to fix the detection method of the mobile robot body. When the mobile robot deviates from the parallel wall surface, the detection system is often difficult to obtain the actual distance. In addition, the divergence characteristics of ultrasonic waves can only provide the distance information of the target obstacle when applied to the measurement of obstacles, and cannot provide the direction and boundary information of the target. These defects have greatly limited the practical application and promotion of ultrasonic sensors.