This thesis describes a positioning control method, using piezoelectric element, of a tiny ultrasonic linear actuator. Because an ultrasonic actuator uses a different driving method from the one of an existing electromagnetic actuator, it has lots of both advantages and disadvantages simultaneously ...
This thesis describes a positioning control method, using piezoelectric element, of a tiny ultrasonic linear actuator. Because an ultrasonic actuator uses a different driving method from the one of an existing electromagnetic actuator, it has lots of both advantages and disadvantages simultaneously compared with the latter. Unlike an electromagnetic actuator, an ultrasonic actuator has an advantage of being not affected by the electric field at all, and it makes nearly no noise when activated. In addition, it can make enormous torque in low speed, and it has a feature of very fast response as to driving and stopping. Whereas, it has a disadvantage of hard control. The reasons are that the driving method of it is more complex than that of the electromagnetic one and furthermore each and every product has slightly peculiar features. Another disadvantage is that, in time of indiscrete driving, it has less durability than a general motor. An ultrasonic actuator is, according to it's structure, divided into a Multi-layer type and a Bimorph type. A tiny ultrasonic linear actuator focused in this thesis is a Bimorph structure that is worked by the principle under which one side is contracted as the other side is extended. This type of actuator is very small in size and has the disadvantage the application of a positioning control system is hard. Because the size is very small, a precise positioning control system should be used. And there's much need for a cheap positioning control system because prevailing positioning control systems are very expensive and the price takes high percentage among the price of the whole system. In this study, instead of an expensive positioning system, a low-cost MR sensor is used to explore the method of precise positioning control of an actuator. We attached a magnetic bar to the mobile element of an actuator and, using an MR sensor, measured the magnetic field varying along with the movement of the mobile element to where a magnetic bar is attached. At each and every predetermined sampling time at every interval, we measured the values of an MR sensor. The measured data were stored at flash memory. Futhermore, even unmeasured location data were calculated by an interpolation method. These measured or calculated location data were used to execute positioning control. For precise positioning control, we calibrated the locations by a minutely step control method. These processes incarnated precise positioning control that is not only much cost-saving but simple in structure.
This thesis describes a positioning control method, using piezoelectric element, of a tiny ultrasonic linear actuator. Because an ultrasonic actuator uses a different driving method from the one of an existing electromagnetic actuator, it has lots of both advantages and disadvantages simultaneously compared with the latter. Unlike an electromagnetic actuator, an ultrasonic actuator has an advantage of being not affected by the electric field at all, and it makes nearly no noise when activated. In addition, it can make enormous torque in low speed, and it has a feature of very fast response as to driving and stopping. Whereas, it has a disadvantage of hard control. The reasons are that the driving method of it is more complex than that of the electromagnetic one and furthermore each and every product has slightly peculiar features. Another disadvantage is that, in time of indiscrete driving, it has less durability than a general motor. An ultrasonic actuator is, according to it's structure, divided into a Multi-layer type and a Bimorph type. A tiny ultrasonic linear actuator focused in this thesis is a Bimorph structure that is worked by the principle under which one side is contracted as the other side is extended. This type of actuator is very small in size and has the disadvantage the application of a positioning control system is hard. Because the size is very small, a precise positioning control system should be used. And there's much need for a cheap positioning control system because prevailing positioning control systems are very expensive and the price takes high percentage among the price of the whole system. In this study, instead of an expensive positioning system, a low-cost MR sensor is used to explore the method of precise positioning control of an actuator. We attached a magnetic bar to the mobile element of an actuator and, using an MR sensor, measured the magnetic field varying along with the movement of the mobile element to where a magnetic bar is attached. At each and every predetermined sampling time at every interval, we measured the values of an MR sensor. The measured data were stored at flash memory. Futhermore, even unmeasured location data were calculated by an interpolation method. These measured or calculated location data were used to execute positioning control. For precise positioning control, we calibrated the locations by a minutely step control method. These processes incarnated precise positioning control that is not only much cost-saving but simple in structure.
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