Characterization and control of a pneumatic microactuator with an integrated inductive position sensor

As the intelligence and the functionality of microrobots increase, there is a growing need to incorporate sensors into these robots. In order to imit the outer dimensions of these microsystems, this research investigates sensors that can be integrated efficiently into microactuators. Here, a neumatic piston-cylinder microactuator with an integrated inductive position sensor was developed. The main advantage of pneumatic actuators s their high force and power density at microscale. The outside diameter of the actuator is 1.3 mm and the length is 15 mm. The stroke of he actuator is 12 mm, and the actuation force is 1 N at a supply pressure of 1.5 MPa. The position sensor consists of two coils wound around he cylinder of the actuator. The measurement principle is based on the change in coupling factor between the coils as the piston moves in he actuator. The sensor is extremely small since one layer of 25 m copper wire is sufficient to achieve an accuracy of 10 m over the total troke. Position tests with a PI controller and a sliding mode controller showed that the actuator is able to position with an accuracy up to 0 m. Such positioning systems offer great opportunities for all devices that need to control a large number of degrees of freedom in a restricted olume. 2007 Elsevier B.V. All rights reserved.