Research On A Suspension-type Pendulum Bench Insensitive To Horizontal Vibration

With the development of science and technology, the accelerometer has been usedmore and more widely, and the expected resolution is higher and higher. For example, thesensitivity of the accelerometer used in the satellite CHAMP for gravity measurements is10-9～10-8m/s2/Hz1/2, and the noise of the accelerometer in LISA project for gravitationalwaves detections should be smaller than3×10-15m/s2/Hz1/2. However, the performance ofthe accelerometers has to be tested on ground before its use in space, in which process theinfluence of the ground vibration noise, which will be directly coupled to the input of theaccelerometer can not be avoided. As the ground vibration acceleration noise is muchhigher than the accuracy requirement, so performance investigation of a high-precisionaccelerometer on ground is limited by the seismic noise. Thus, it is very important todecrease the influence of the vibration noise in the test of accelerometers on ground.In this paper, conventional methods to suppress the vibration noise have beeninvestigated, and we proposed and demonstrated a new approach to decrease the influenceof vibration noise for the ground test of our high precision space accelerometer. In thisapproach, a pendulum bench is suspended as a test platform, which will tilt when there’san impact on the suspension point due to the vibration noise. In this situation, the impact isautomatically compensated by the change of the projection of the gravitationalacceleration caused by the tilt.First of all, the performance of the design scheme is analyzed, and the transferfunction of the response of the accelerometer which is placed on the pendulum bench andthe acceleration of ground can be obtained. The theoretical analysis results show that withthis design scheme, not only the high frequency (above the eigenfrequency of thependulum bench) ground vibration noise, but also the low frequency (below theeigenfrequency of the pendulum bench) ground vibration noise, can be suppressed.Secondly, the effect of the hinge stiffness has been discussed in theory. Theperformance of the pendulum bench shall be disturbed by the hinge stiffness in the lowfrequency region, and the hinge dissipation is one of mechanical thermal noise sources.These theoretical analysis results are useful for the experimental design. Finally, in order to verify the feasibility of the method, a pendulum bench has beenconstructed. The test results show that its performance matches the theoretical analysis,both the high frequency and the low frequency ground vibration noise can be attenuatedby the pendulum bench.