The AUV hardware is composed of two main processor boards: a low level and a high level electronics. The low level electronic is based on the iCm4011 microcontroller development board from Ingenia that uses a dsPIC 30F4011 as main processor. This board provides I2C and RS232 interfaces for communicating with the sensors and the high level processor unit. The high level board is an industrial PC based on Intel X86 microprocessor. This is the environment where most of the planning and controlling software resides. Figure 3 shows, in schematic way, the on-board electronics for the low-coast AUV prototype. The microcontroller board gets the position either from the GPS when surfaced, or from an accelerometer, integrating both x and y readings. From this data and the reading data provided by the depth meter, the microcontroller board is capable to provide the (x, y, z) triplet necessary for the proper position. The GPS sends its data using RS232 streams according to a format specified by the National Marine Electronics Association (NMEA). The accelerometer is based on the Analog Devices ADXL 202, dual axis accelerometer, constituting an inexpensive device that measures accelerations with a full-scale range of ±g. This sensor outputs are analog voltages or digital signals whose duty cycles, that is, the ratio of pulse width to period, are proportional to acceleration. The duty cycle outputs can be directly measured by the microprocessor.
Was this article helpful?