Key Engineering Materials Vols. 295-296

Abstract: The non-contact pneumatic measurement technique is useful for dimension measurement. The authors have developed a new type of air-pin pneumatic-electronic sensor. The ultra-precision air-pin sensor and the dynamic characteristics of the sensor are investigated. The measurement accuracy of the air-pin pneumatic-electronic sensor is better than 0.1µm for the 10µm measurement range. The response time is less then 10ms.

Abstract: For reducing the machining difficulty and increasing the conjunction precision, an automatic sorting system is presented. The system combines the backpressure pneumatic measurement with a pneumatic-electric transfer technology. A semiconductor pressure sensor is used for the pneumatic-electric transfer. The air chamber pressure is converted to an electrical signal. The merits of the semiconductor pressure sensor include high conversion precision, high frequency response, and small volume. But it has a relatively big temperature drift if no compensation is provided. The sensor can compensate temperature drift. But the null shift and sensitivity shift still exist. Reducing supply voltage using an electric bridge or reducing supply current using a constant current source can reduce the shift. The null shift and sensitivity shift can be further reduced by auto-compensation using a calibrated gauge. The automatic sorting system can automatically sort injector valves and orifices quickly with a resolution of 0.2µm. The sorting accuracy is 0.5µm and the speed is approximately thirty pieces per minute. The system has the function of auto-control and error auto-compensation and has a high measuring efficiency and high precision.

Abstract: This paper describes the design of an intelligent multi-gyro measurement device to measure and monitor an inertial unit composed of three dynamically tuned gyros (DTGs). A 16-bit microprogrammed control unit is programmed to fulfill the functions of signal processing, logic control and serial communication with a master computer. An FPGA, designed by using Verilog Hardware Description Language, is used to realize high speed 16-bit reversible counters for output pulses of the DTG digital dynamic balance circuits. The count values represent the angular motion of the inertial unit. A stepping electric bridge is employed to measure the resistance of thermal resistors within the gyros in a wide temperature environment. The resistance represents the working temperature of the gyros. An effective calibration method for the bridge is developed to eliminate the resistance measurement error. A test system is established to examine whether the device meets the user requirements. Results of the tests show that the device has a good performance. A trial use has proved that the device is stable and reliable and that it satisfies the demand of the user.

Abstract: This paper describes an X-Y stage with a plane cross grating for position feedback. The stage has a current servo motor and a piezoelectric actuator to realize coarse and fine positioning throughout the 50mm x 50mm range of travel. The objective table contacts tightly on a planar wafer to enhance the motion flatness. The horizontal positioning noise is less than 20nm. The stage has a positioning accuracy of 3µm. If a high quality grating and guide is used, it should be useful for 3D surface measurement and ultra-precision machining. The operating principle and the characteristics of the plane cross grating are presented. The internal structure is explained. The comparison result for the stage with a laser interference calibration is presented. The theoretical precision and error sources of the system including grating grid, guide and grating installation error are analyzed. Experiments on factors such as system noise, guide error and motion interference are presented and the results are analyzed.

Abstract: It is important to track a free flying insect to investigate its flight performance. Conventional video tracking systems are difficult to track a highly maneuverable insect, because the capture frequency of the camera is limited and it can hardly get the position of the insect in real time. We proposed a fast sensing method for insect tracking based on magnetic search coil sensors. It can simultaneously determine the orientation and position of the sensors. We constructed a system, calibrated the magnetic device. We developed a set of calculating methods and measured several positions and angles of coil sensors. The results show that it can rapidly provide the tracking feedback information to meet the requirement for insect tracking.

Abstract: We propose a new beating machine based on a dual cam and lever mechanism to operate flapping and torsion motions of a dragonfly wing. The beating machine was designed according to the time dependent variation in flapping angle and in torsion angle of a free flight dragonfly. Our experiment results show that the variations in flapping angle and in torsion angle of a wing on beating machine agree well with those of a real free flight dragonfly wing, confirming that our beating machine is available for studying the beating performance. We then use the beating machine to study the aerodynamic force and inertia affecting on the wing by comparing the flapping angle and torsion angle under the normal and vacuum conditions.

Abstract: A new linear motor based on the Sawyer principle is firstly introduced. Some important features of the linear actuator are discussed for better understanding of its performances and functions with absolute positioning. We investigated the static characteristics of the linear motor such as the relationship between the current and the maximum thrust force (I-F curve), the relationship between the displacement and the thrust force (D-F curve), and the positioning accuracy. The measuring methods for these characteristics are explained in detail. We analyzed the experimental data and evaluated the characteristics. We obtained that the suitable working current is 1A and the maximum thrust force is 15N for the linear motor. The positioning accuracy is ±12µm.