Research Of Magneto-rheological Damper Force Sensor Based On Piezoresistive Principle

Magneto-rheological(MR)dampers are semi-active control devices that have many advantages with continuously adjustable damping, fast response, wide dynamic range and low power consumption. So far, MR dampers have been applied in many application fields, such as civil structure, vehicle, healthcare etc. However, there may exit some defects for MR dampers, such as the MR fluid deposition, hardening and leakage or other mechanical and electrical fault. All these can lead to the attenuation performance or even the failure of MR dampers. Therefore, the health of MR damper in operation need to be monitored. To realize the feedback control of the MR damper system, the premise is to use sensors to obtain real-time dynamic information of the application objects. Compared with acceleration, velocity and displacement of these state parameters, damping force can influence the control effect of magneto-rheological damper output more directly In addition, it is more easier to acquire the damping force, Besides, It can also reflect the health status of the operation of the MR damper to a great extent So it is very necessary for MR dampers to develop an output damping force monitoring system online.Aiming at the existing shortcomings of semi-active suspension system separated with MR dampers,such as complex wire, high cost and low reliability. A piezoresistive MR damper force sensor integrated with the piston rod of the MR damper is proposed in this study.The main work of this paper is summarized as follows:① A comprehensive review of background and significance of the study, research and development of magnetorheological fluid and MR damper, research status of magnetorheological damper force sensing technology and piezoresistive pressure sensors at home and abroad are given in this paper.② According to the operating characteristics of the magnetic rheological dampersfor automobile and the design principle of piezoresistive pressure sensor, we design theoverall structure and the chip of the piezoresistive MR damper force sensor The sensoris designed in order to measure dynamic reciprocating stroke of the MR damper whichneed to achieve the design range, obtain larger sensitivity and natural frequency. Thesize of the sensor chip is determined by the combined method of theory calculationand finite element simulation. The type of the sensor chip, the measuring circuit and the fabrication materials are determined through analytic demonstration. For the design of the chip layout, the crystal orientation, the doping concentration and temperature are critical factors influencing the piezoresistive coefficient. The doping concentration, the arrangement direction, the position, the size, and the bending number of the resistance are acquired according to theoretical analysis and FEM.③ The static and dynamic performance index of the MR damping force sensor based on piezoresistive principle is analyzed. By using the FEM simulation, a group of pressures are applied on the sensor, and the stress distribution and the stress changes along the piezoresistive strip width and length at different pressures are obtained. So we can evaluate the linearity and sensitivity of the piezoresistive MR damper force sensor. We simplify the magneto-rheological damper force sensor for single degree freedom linear system of two order, and derive the calculation of air damping coefficient of the sensor system, then obtain the transfer function of the sensor. At last, we analyze the dynamic performance of the sensor with Matlab. The characteristics of the sensor in time domain and frequency domain are obtained by exerting different excitation.④ The analysis of process and package of the MR damper force sensor based on piezoresistive principle is carried out. The key process and the mask used during production process of MR damping force sensor are designed. Besides, the thermal stress generated by adhesive with different Young’s modulus and different thickness are simulated when the sensor is packaged. All this work lay the foundation for the further processing.