Signal Processing Of The Piezoelectric Six-Axis Accelerometer

The technology of six-axis accelerometers will be not only useful for the development of robotics, navigation, aviation and weapons, but also will be extensively used in industrial automatic control, automobile engineering, earthquake prediction and so on. Most accelerometers only can sense from one degree-of-freedom (DOF) to three-DOF accelerations, so the present researches mainly focus on how to detect six-DOF accelerations through the combination of several single-axis accelerometers. At present, the reported six-axis accelerometers can be categorized into three types, which include the six-axis accelerometers by MEMS (Micro Electronic Mechanical Systems) technology, the six-axis accelerometers with the combination of resistance strain gauges on membrane, and the six-axis accelerometers based on the superconducting principle. Through MEMS technology, several single-axis accelerometers can be integrated on one silicon wafer to realize the six-axis accelerometer. Although the miniaturization of the six-axis accelerometers by MEMS can be increased, the sensory accuracy will be decreased. Furthermore, the six-axis accelerometers by MEMS technology can't bear heavy overload. The six-DOF accelerometers through the combination of resistance strain gauges on the membrane, which are still in the process of research, let the decoupling of the six-axis acceleration be very difficult. The six-axis accelerometer based on the superconducting principle is designed for use in micro-gravitation circumstance. Moreover, the six-axis accelerometer based on the superconducting principle possesses the complicated structure and high cost. In this case, the research on multi-DOF accelerometers (especially the six-axis accelerometers) has important theoretical significance and practical values.In this dissertation, the principle and structure of a piezoelectric six-axis accelerometer are proposed and explored and the six-DOF acceleration is accessed by six piezoelectric single-axis accelerometers, which are aligned along the designated configuration and used as the sensory elements. The corresponding signal conditioning system for the proposed six-axis accelerometer is developed and the rapid prototyping system is also established. Based on the established rapid prototyping system of the six-axis accelerometer, experimental tests are carried out. Moreover, the signal processing system for the piezoelectric six-axis accelerometer is researched based on digital signal processor (DSP). In the research process, the on-off response characteristic that represents the power-on response performance of charge amplifiers is proposed and defined and the corresponding measurement method is also proposed.The major research works completed in this dissertation include:①The principle and structure of the piezoelectric six-axis accelerometer are proposed and explored through aligning six piezoelectric single-axis accelerometers along the designated configuration, in which the six piezoelectric single-axis accelerometers are used as sensory elements to acquire six-DOF acceleration and the structure of the piezoelectric six-axis accelerometer based on the proposed principle is realized. The decoupling algorithm to realize the detection of six-DOF acceleration by combining and decoupling outputs from the six single-axis accelerometers are introduced. Utilizing the decoupling algorithm, the six-DOF acceleration, including three linear acceleration components and three angular acceleration components (or angular velocity), can be acquired.②Regarding the piezoelectric six-axis accelerometers and the gyro-free (GF-INS) based on the piezoelectric six-axis accelerometers, the on-off response time and volume size directly depend on its signal conditioning system. In this dissertation, the on-off response characteristic that represents the power-on response performance of charge amplifiers is proposed and the measurement method is also introduced. In order to improve the on-off response and reduce the volume size, a multi-channel charge amplifier, which not only possesses rapid power-on response performance but also possesses the small volume size, is developed. Furthermore, the rapid on-off response characteristic of the developed charge amplifier is verified by the experimental testing results.③The rapid prototyping system of the piezoelectric six-axis accelerometer is built based on the dSPACE real-time simulation system. The model algorithm of the piezoelectric six-axis accelerometer is designed to programs in MATLAB/Simulink and then the programs are loaded into dSPACE. By communication with the host computer, the detected six-axis acceleration is monitored in real time by ControlDesk.④The experimental testing system for the rapid prototyping system of the piezoelectric six-axis accelerometer is set up and test experiments are carried out. The experimental results show that the proposed six-axis accelerometer is capable of sensing the six-DOF acceleration.⑤Furthermore, the signal processing system for the piezoelectric six-axis accelerometer based on DSP is researched and the arithmetic of model is integrated into DSP, which provides the foundation for the miniaturization and production.The research works in this dissertation establish the theoretical foundation for the development of six-axis accelerometers.