Ultra-low frequency active vibration control for cold atom gravimeter based on sliding-mode robust algorithm

Abstract

An ultra-low frequency vibrational noise isolation apparatus from external vibration can be a critical factor in many fields such as precision measurement, high-technology manufacturing, scientific instruments, and gravitational wave detection. To increase the accuracies of these experiments, well performed vibration isolation technology is required. Until recently the cold atom gravimeter has played a crucial role in measuring the acceleration due to gravity and earth gravity gradient. The vibration isolation is one of the key techniques in the cold atom gravimeter. To reduce the vibrational noise caused by the reflecting mirror of Raman beams in the cold atom gravimeter, a compact active low-frequency vibration isolation system based on sliding-mode robust control is designed and demonstrated. The sliding-mode robust control active vibration isolation method is used to solve the vibration problem of Raman mirror in the cold atomic gravimeter. The purpose of vibration control is that the controller enables the system to be at zero state as the system states are away from the equilibrium due to vibration disturbance. In this system, the mechanical setup is based on a commercial passive isolation platform which only plays a role at higher frequency. A sliding-mode robust control subsystem is used to process and feed back the vibration measured by a seismometer which can measure the velocity of the ground vibration. A voice coil actuator is used to control and cancel the motion of a passive vibration isolation platform. The simulation and experiment results of vibration isolation platform show, on the one hand, that the vibration noise power spectral density decreases by up to 99.9%, and that the phase noise in cold atom interferometry produced by vibration decreases by up to nearly 85.3% compared with the results of the passive vibration isolation platform. On the other hand, compared with the lead-lag control method, the vibration noise power spectral density decreases by up to 83.3% and the phase noise in cold atom interferometry produced by vibration decreases by nearly 40.2%. Therefore, the sliding-mode robust control has the advantages of less tuning parameters, strong anti-interference ability, and more obvious vibration isolating effect.

High-accuracy inertial measurements with cold-atom sensors

“…As mentioned in part III E for increased T , parasitic vibrations limit the sensitivity. Different isolation methods have been used, based on superspring stabilization 70 , or the use of passive isolation platforms 25 , eventually combined with additional active stabilization feedback control [71][72][73][74][75] , or the correlation of the interferometer phase with the remaining vibration noise measured by a classical sensor, either a seismometer 76 , or an accelerometer 77 . The latter method allows for correcting the interferometer phase, either via postcorrection 25 , or feed forward compensation in real time on the Raman lasers phase difference 77 .…”

High-accuracy inertial measurements with cold-atom sensors

“…As mentioned in part III E for increased T , parasitic vibrations limit the sensitivity. Different isolation methods have been used, based on superspring stabilization 65 , or the use of passive isolation platforms 25 , eventually combined with additional active stabilization feedback control [66][67][68][69] , or the correlation of the interferometer phase with the remaining vibration noise measured by a classical sensor, either a seismometer 70 , or an accelerometer 71 . The latter method allows for correcting the interferometer phase, either via postcorrection 25 , or feed forward compensation in real time on the Raman lasers phase difference 71 .…”

Research Progress of Dynamic Measurement Technology of Atom Gravimeter

“…Whether it is the compensation of vibration noise or the rough estimate of gravity value, the accelerometer is required to have high precision, so the error of the accelerometer itself cannot be ignored. However, due to the influence of environmental factors such There are mainly three methods for suppressing vibration noise: passive vibration isolation based on super springs [51], active vibration isolation with feedback control [52][53][54], and using a motion sensor such as a seismometer or accelerometer to measure vibration noise and compensate [46,48]. In practical application, in the case of obvious external vibration and large interference, the vibration compensation method has a better effect than the active and passive vibration isolation methods.…”