Abstract: A method for selecting drilling parameters for drilling a borehole penetrating the earth with a drill string. The method includes: measuring vibration-related amplitudes of the drill string during operation using one or more vibrations sensor to provide amplitude measurements; determining with a downhole processor one or more modal properties comprising one or more eigenfrequencies of the drill string using the amplitude measurements, the determination being made by including any excitation force in a white noise term of a model of the drillstring; and selecting drilling parameters that apply an excitation force at a frequency that avoids a selected range of frequencies that bound the one or more eigenfrequencies using the processor.

Abstract: A method for selecting drilling parameters for drilling a borehole penetrating the earth with a drill string. The method includes: measuring vibration-related amplitudes of the drill string during operation using one or more vibrations sensor to provide amplitude measurements; determining with a downhole processor one or more modal properties comprising one or more eigenfrequencies of the drill string using the amplitude measurements, the determination being made by including any excitation force in a white noise term of a model of the drillstring; and selecting drilling parameters that apply an excitation force at a frequency that avoids a selected range of frequencies that bound the one or more eigenfrequencies using the processor.

Abstract: A method of testing a downhole component configured to be incorporated in a drilling assembly includes generating a mathematical drilling assembly model representing a connecting string as a virtual connecting string and describing a behavior of the connecting string in response to rotation of the drilling assembly, disposing the downhole component at a sample of a formation material, and rotating the downhole component by applying a torque to the downhole component via a torque motor based on the drilling assembly model and a selected rotational rate of a virtual top drive. The method further includes inputting real time measurements of an angular velocity of the downhole component into the drilling assembly model, calculating a target torque corresponding to an amount of torque that would be applied to the downhole component by the virtual connecting string, and adjusting the applied torque from the torque motor to correspond to the target torque.