| The wheel force of the vehicle is the result of the interaction of ground and wheel which is also affected by environmental factors. The real-time detection of the wheel force in various conditions is the basis of the vehicle movement analysis and vehicle experiments. As a specialized tool of measuring wheel forces and moments during vehicle driving, the multi-dimensional wheel force transducer (WFT) plays an irreplaceable part in the vehicle experiments and tests. Therefore, it is significant to design and develop the WFT in order to promote the vehicle manufacturing of our nation. This paper focuses on the design of the multi-dimensional WFT, and carries out a detailed study on the data processing and measurement decoupling methods. The main contents are as follows:1. The design of the multi-dimensional WFT has been studied. According to the wheel force measurement, the sensor design is divided into three parts, namely the wheel force sensing, the wheel force data acquisition and the wheel force data processing. The design requirements of each part have been achieved, and the transducer body, the bridge circuits, data acquisition module and data transmission module have been designed. Furthermore, a data processing method that is based on the structure decoupling and rotation decoupling has been proposed in this paper.2. Aiming at the structure coupling issue among the measurement channels of the multi-dimensional WFT, the static calibration experiment of the WFT has been designed and completed on the calibration platform. The mathematical relationship between the voltage outputs of measurement channels and the actual loads on the WFT has been established. Through the analysis and processing of the experimental results, the coupling degree of the measurement channels has been greatly decreased.3. Because the WFT rotates with the wheel during the vehicle driving, the measurement precision of the wheel angle rotation has significant impact on the rotation decoupling of the wheel force data processing. In this paper, a calibration method of encoder’s initial installation has been proposed and tested in experiments. The experiment results show that the proposed method is able to accurately calculate the zero position of encoder, and greatly reduced the measurement error of the wheel rotation angle to further improve the rotational decoupling accuracy.4. For the specific installation of the multi-dimensional WFT, the vehicle turning might introduce angle error in the output of the encoder. A compensation algorithm has been proposed. It estimates the wheel speed by comparing real-time GPS speed with encoders’output to judge whether the angle deviation has occurred, and further correct the output of the encoder. The result of the vehicle test illustrates that the proposed compensation method has effectively enhanced the wheel force calculation accuracy.5. On account of the randomness and the modeling difficulty of the wheel force signal, wheel force signal has been categorized into two dynamic conditions for modeling. The Singer wheel force model based on first order Markov process is established for the high dynamic conditions; planar-turning wheel force model is built cornering the low dynamic conditions. In this way, the random wheel force signals are achieved accurate modeling.6. For the de-noise issue of the wheel force signal, an adaptive filtering method has been proposed for the wheel force rotation decoupling and real-time filtering. It uses the sparse grid quadrature Kalman filter to deal with the nonlinear system model and provide high computational efficiency, and calculates the weights of different models with the interacting multi-model algorithm to further switch to the appropriate model to filtering and rotation decoupling. This method has been tested that it has ability of adaptive selection of the wheel force model, and improvement of the system accuracy. |
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