Experimental investigation of a gimbal in the frequency domain

[摘要] ENGLISH ABSTRACT: When it comes to renewable energies, the reduction of initial investment costs helpmake these generation methods a more viable option for governments, or privatecompanies. For Concentrated Solar Power (CSP) plants, a particular example ofthis would be the initial investment costs associated with the heliostats. Heliostatfoundation preparation and heliostat structure quality need to be of a high standardfor a heliostat to remain within its calibration parameters for long periods of time.If calibrations, inspections and cleaning of these heliostats can be done moreregularly, the time for which the heliostat needs to maintain its calibrationparameters is reduced, thereby reducing foundation preparation costs and heliostatmanufacturing costs.At the University of Stellenbosch, the Solar Thermal Energy Research Group(STERG) is investigating the use of automated drones to perform inspections,calibrations and cleaning of heliostats. In order to attach sensors to the drone, agimbal is used. This isolates the sensor from the drone's rotations. Gimbal dynamicperformance data, which is relevant to design engineers, is not readily available. Inthis thesis, the pitch responses of a two-axis gimbal to pitch and roll disturbancesare measured for varying disturbance frequencies and amplitudes, without vibrationisolation pads.In addition to producing the gimbal performance data, it is found that the largestgains observed occurred in region where no structural natural frequencies werefound. It is suspected that the knocking of the gimbal Inertial Measurement Unit(IMU) cable, which is connected to the device-mount IMU, is the source of thesepeak responses. The responses to pitch and roll actuations differed significantly,with the largest reponse attenuation observed for pitch actuations between 31 Hzand 46 Hz. It is also found that the gimbal is sensitive to frame vibrations, especiallyat frame natural frequencies, which highlights the need for vibration isolation padsduring use. It is recommended that further research be conducted in the frequencydomain for roll and yaw responses. In addition, it is recommended that the efficacyof gimbal vibration isolation pads, for blade pass frequencies, be investigated.Lastly, it is recommended that a more detailed analysis of the gain attenuationobserved for the responses to pitch actuations, be conducted.

[发布机构] Stellenbosch University