Research On Data Acquisition System Of Piezoelectric Six-Axis Force Measuring Instrument

The six-dimensional force/torque sensor is a device to sense the three-dimensional force and measure the three-dimensional torque of physical objects in three-dimensional space.For the merits of full space-time,better stability,the six-dimensional force sensing technology has been integrated into many industries and has an application prospect in the fields like land,sea,air as well as space.The piezoelectric six-axis force sensor has an outstanding performance in its linearity,natural frequency and other performance indicators among all the six-dimensional force sensors.However,it requires special equipment in the later measurement,for the adoption of the piezoelectric effects principle and the specific support structure of eight points.Due to the complex procedure,the heavy weight,the sole function and the high cost,the traditional measurement methods are failed to achieve the convenient and fast real-time measurement.Based on the reasons above,the piezoelectric six-axis force sensor is encountering the bottleneck in the practical utilization.This paper studies the flat piezoelectric six-axis force sensor and proposes the solution based on the embedded real-time operating system(RTOS)in which the adoption of the single A/D multichannel synchronous acquisition technology and embedded RTOS solve the technical difficulties such as multichannel synchronous data acquisition and background multitasking.The paper includes the study of the sensing mechanism and the output signal characteristics of the flat piezoelectric six-axis sensor,the design proposal and the evaluation of the system hardware;the demand analysis of the function of the data acquisition system,the design proposal of the software based on the FreeRTOS,the research on the types of the embedded RTOS,the architecture design of the system software,the transplantation and the embedment of the necessary middleware,the analysis and the allocation of the system tasks as well as the optimal design of system functions;the construction of the test environment of the measurement instrument,and the verification of the primary functions of the measurement instrument.The main research is concluded as following:(1)the study of the sensing principle of the piezoelectric six-dimension force sensor,and the detailed research on the characteristics of the output signal from the sensor.The author analyzes the overall design requirement and then determines the overall design plan of the hardware in which the single A/D multichannel synchronous signal sampling technology is realized by using a true bipolar chip AD7606 from ADI,and the mainstream design plan is adopted in the rest of other modules.(2)the analysis of the functional requirements of the acquisition system of the piezoelectric six-axis force measurement instrument,the rejection to the traditional super cycle framework for software design,and the adoption the solution of the embedded RTOS.The author transplants FreeRTOS which is the most used embedded RTOS,transplants and modifies the graphical interface emWin as well as the file system FatFs according to the functional requirements of the acquisition system.Also,the author embeds the Internet of Things(IoT)in the function of the environmental measurement module,exchanging data with OneNET,the China Mobile IoT open platform,and designs a unique environment index algorithm to monitor and display the measurement environment in real time.Meanwhile,the author embeds the least squares method to fit the input/output characteristic curve of the sensor into the comprehensive judgement function.Besides,in the display function,the multichannel data can be displayed for the manipulation of Message Queuing by the operation system FreeRTOS.(3)the construction of the experiment environment to test and evaluate the data acquisition system,the analysis of the experimental data,and the explanation of the reasons for the errors therein.The solution of the flat piezoelectric six-axis force measurement instrument based on the embedded real-time operating system(RTOS)in this paper lays the practical foundation for the sensor techonology,and enhances its network function and intelligence with the embeddment of the network plaform protocol and algorithm.