Abstract: An electric fan with a self-cleaning mode to energise rotating fan blades in alternate forward and reverse directions to create a vibration in order to shake built-up dust or dirt particles from the blades in a frequency at which the rotational direction is alternated set to a known or detected resonant frequency of the blades thereby excite resonant modes and maximise the amplitude of vibrations. The self-cleaning operation may be triggered by detection of excessive/abnormal loading on the motor. The fan may be operated in a vibration detecting mode over a range of rotational speeds to locate speeds that produce resonance, or to detect a fault with the fan. Motor reversal frequencies corresponding to resonance-inducing speeds may be used in the self-cleaning mode. The vibration detecting mode may be carried out while the at least one blade is rotated in a direction opposite to its normal operational rotational direction.

Abstract: An electric fan with a self-cleaning mode to energise rotating fan blades in alternate forward and reverse directions to create a vibration in order to shake built-up dust or dirt particles from the blades in a frequency at which the rotational direction is alternated set to a known or detected resonant frequency of the blades thereby excite resonant modes and maximise the amplitude of vibrations. The self-cleaning operation may be triggered by detection of excessive/abnormal loading on the motor. The fan may be operated in a vibration detecting mode over a range of rotational speeds to locate speeds that produce resonance, or to detect a fault with the fan. Motor reversal frequencies corresponding to resonance-inducing speeds may be used in the self-cleaning mode. The vibration detecting mode may be carried out while the at least one blade is rotated in a direction opposite to its normal operational rotational direction.

Abstract: A method and system for building virtual reality object models. The method includes defining an object space, generating multiple two-dimensional real images of the object, and selecting multiple reference points in each image, the reference points defining an image region, the region having a texture. The method also includes determining the three-dimensional position in the object space of each of the reference points in each image, the positions determined defining a model surface, mapping the texture of an image region onto a model surface, and generating a three-dimensional model of the object using the determined positions and the mapped texture. The system includes one or more cameras, a calibration apparatus, a graphic interface and software for performing the method.