Browsing by Author "Haller, Michen Christian"

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    Experimental investigation of a gimbal in the frequency domain
    (2019-04) Haller, Michen Christian; Smit, Willie; Bekker, Annie; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering (CRSES)
    ENGLISH ABSTRACT: When it comes to renewable energies, the reduction of initial investment costs help make these generation methods a more viable option for governments, or private companies. For Concentrated Solar Power (CSP) plants, a particular example of this would be the initial investment costs associated with the heliostats. Heliostat foundation preparation and heliostat structure quality need to be of a high standard for a heliostat to remain within its calibration parameters for long periods of time. If calibrations, inspections and cleaning of these heliostats can be done more regularly, the time for which the heliostat needs to maintain its calibration parameters is reduced, thereby reducing foundation preparation costs and heliostat manufacturing 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, a gimbal is used. This isolates the sensor from the drone’s rotations. Gimbal dynamic performance data, which is relevant to design engineers, is not readily available. In this thesis, the pitch responses of a two-axis gimbal to pitch and roll disturbances are measured for varying disturbance frequencies and amplitudes, without vibration isolation pads. In addition to producing the gimbal performance data, it is found that the largest gains observed occurred in region where no structural natural frequencies were found. 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 these peak responses. The responses to pitch and roll actuations differed significantly, with the largest reponse attenuation observed for pitch actuations between 31 Hz and 46 Hz. It is also found that the gimbal is sensitive to frame vibrations, especially at frame natural frequencies, which highlights the need for vibration isolation pads during use. It is recommended that further research be conducted in the frequency domain for roll and yaw responses. In addition, it is recommended that the efficacy of gimbal vibration isolation pads, for blade pass frequencies, be investigated. Lastly, it is recommended that a more detailed analysis of the gain attenuation observed for the responses to pitch actuations, be conducted.