Papers by Keyword: Velocity Feedback

Abstract: Limited by supply voltage on board, control accuracy of low velocity and available torque of Control Moment Gyros (CMGs) gimbal driving motor are limited. Adding Harmonic Drive (HD) between driving motor and CMGs gimbal can improve CMGs control system performance. The paper establishes a practical HD model considering transmission, bearing friction, tooth meshing friction and compliance of flexspline. The model is properly simplified for analysing the control performance of whole closed loop system. Transfer functions are analysed and the flexspline output velocity is chosen to be the velocity feedback for controller according to the characteristics of CMGs gimbal velocity command. All of the numerical simulation results validate the theory analysis.

Abstract: This paper presents a theoretical and experimental study of a non-collocated pair of piezopolymer PVDF sensor and piezoceramic PZT actuator, which are bonded on a cantilever beam, in order to suppress unwanted vibration at the tip of the beam. The PZT actuator patch was bonded near the clamped part and the PVDF sensor, which was triangularly shaped, was bonded on the other part of the beam. This is because the triangular PVDF sensor is known that it can detect the tip velocity of a cantilever beam. Because the arrangement of the sensor and actuator pair is not collocated and overlapped each other, the pair can avoid so called "in-plane coupling", which can be found at a matched piezoelectric sensor and actuator pair and restricts the stability and performance of direct velocity feedback control. The test beam is made of aluminum with the dimension of 200 × 20 × 2 mm. Before control, the sensor-actuator frequency response function is confirmed to have a nice phase response without accumulation in a reasonable frequency range of up to 5000 Hz. The feedback control attenuates the magnitude of the first two resonances in the error spectrum of about 6 -7 dB.