An All-Fiber Optical Sensor Combined with FBG and CFBG-FP for Attitude Estimation.

In order to meet the needs of attitude correction of the optical fiber sensor array, an all-fiber optical sensor combined with FBG and CFBG-FP is proposed to monitor its attitude angle. The FBG sensor for pitch and roll angles detection employs a geometric model solution to shift the center wavelength of the three fiber Bragg gratings connected to it through the mass sphere, allowing for pitch and roll angle detection. Based on the magnetostrictive effect, the CFBG-FP sensor for heading angle detection employs changes of the cavity length of the chirped grating Fabry-Pérot cavity connected to its surface. The method of interpolation data processing and derivation of the attitude angle matrix is used to realize heading angle detection. The experimental results indicate that the FBG sensor for the pitch and roll angles detection has an effective detection range of 180 degrees and an angle measurement error of less than 1.5 degrees. Meanwhile, in the region beyond 10 degrees in the geomagnetic north-south direction, the angle measurement error of the CFBG-FP sensor for the heading angle detection is less than 1.3 degrees. Moreover, the impact of temperature in the system is minimized, demonstrating the validity of this combined fiber optical approach in the attitude angle measurements.

A Hierarchical Stabilization Control Method for a Three-Axis Gimbal Based on Sea-Sky-Line Detection.

Obtaining a stable video sequence for cameras on surface vehicles is always a challenging problem due to the severe disturbances in heavy sea environments. Aiming at this problem, this paper proposes a novel hierarchical stabilization method based on real-time sea-sky-line detection. More specifically, a hierarchical image stabilization control method that combines mechanical image stabilization with electronic image stabilization is adopted. With respect to the mechanical image stabilization method, a gimbal with three degrees of freedom (DOFs) and with a robust controller is utilized for the primary motion compensation. In addition, the electronic image stabilization method based on sea-sky-line detection in video sequences accomplishes motion estimation and compensation. The Canny algorithm and Hough transform are utilized to detect the sea-sky line. Noticeably, an image-clipping strategy based on prior information is implemented to ensure real-time performance, which can effectively improve the processing speed and reduce the equipment performance requirements. The experimental results indicate that the proposed method for mechanical and electronic stabilization can reduce the vibration by 74.2% and 42.1%, respectively.

Analysis of force vector field during centrifugation for optimizing cell sheet adhesion.

A three-dimensional tissue was fabricated by layering cell sheets with centrifugation. In this system, an optimal centrifugal force promoted the adhesion between (a) a cell sheet and a culture dish, and (b) layered cell sheets, resulting in a significant decrease in the fabrication time of the tissue. However, negative effects like sliding/significant deformation of cell sheets were observed upon high rotational speed use. These negative effects inhibit the further shortening of the fabrication time. The sliding/deformation suggests that the centrifugal forces were applied on the cell sheets in unwanted directions. Studies on the force vector field applied to the object placed on the plate during centrifugation are not available, and thus, the reason for the occurrence of such negative effects is unclear. Here, we theoretically derived the spatial distribution of acceleration applied on a plate during centrifugation. Using this theory, we found that the negative effects were triggered by the centrifugal force in the direction parallel to the plate surface, which appeared due to an inclination of the plate surface against a horizontal plane. Therefore, by adding weights on the plate edge to maintain the plate surface in a horizontal position, we succeeded in eliminating the negative effects and in increasing the rotational speed, with the minimum risk of sliding/deformation of cell sheets. We succeeded in reducing the time to establish tight adhesion between a mouse myoblast sheet and a culture dish, and layered cell sheets by increasing the centrifugal force from 5 min to 1 min without significant cytotoxicity.

Attitude Angle Compensation for a Synchronous Acquisition Method Based on an MEMS Sensor.

As a new type of micro-electro-mechanical systems (MEMS) inertial sensor, the Quartz Vibrating Beam Accelerometer (QVBA) is widely used in intelligent sweeping robots, small aircraft, navigation systems, etc. For these applications, correcting and compensating the attitude angle with the result of acceleration plays an important role to improve the measurement accuracy. The synchronization error between the measurement of the accelerometer and gyroscope attitude angle has an adverse impact on the accuracy of the attitude angle. In this paper, a synchronous acquisition scheme of the accelerometer and gyroscope attitude angle in a strapdown inertial navigation system (SINS) is proposed. At the same time, to improve the sampling accuracy and the conversion speed of QVBA, an improved equal-precision frequency measuring method is also implemented in this paper. The hardware float point unit (FPU) is used to accelerate the calculation of the frequency measurement value. The long-term cumulative error of the frequency measurement value is less than 10 - 4 . The calculation process time from sampling to attitude angle compensation calculation is reduced by 40.8%. This work has played a very good role in improving the measurement accuracy and speed of the SINS.

Measurement of Unmanned Aerial Vehicle Attitude Angles Based on a Single Captured Image.

The limited load capacity and power resources of small-scale fixed-wing drones mean that it is difficult to employ internal high-precision inertial navigation devices to assist with the landing procedure. As an alternative, this paper proposes an attitude measurement system based on a monocular camera. The attitude angles are obtained from a single captured image containing five coded landmark points using the radial constraint method and three-dimensional coordinate transformations. The landing procedure is simulated for pitch angles from -15 ∘ to -40 ∘ , roll angles from -15 ∘ to +15 ∘ and yaw angles from -15 ∘ to +15 ∘ . For roll and pitch angles of approximately 0 ∘ and -25 ∘ , respectively, the accuracy of the method reaches 0.01 ∘ and 0.04 ∘ . This UAV attitude measurement system obtains an attitude angle by a single captured image, which has great potential for assisting with the landing of small-scale fixed-wing UAVs.

Measuring system for an attitude angle of a denture using an Inertial Measurement Unit.

PURPOSE: The aim of this study was to assemble and verify a measuring system for 3-D movements (attitude angle) of the denture during function. METHODS: For the calibration test, the sensor was fixed at the center of the rotary table. Operation and stopping of the rotary table were repeated 8 times, and the direction of rotation was reversed in the middle. The amount of rotation was 1.2 and 2.4°. As a pilot clinical trial, the attitude angles of three upper complete dentures during tapping were measured by this system. RESULTS: The attitude angles calculated by this system reduced by 3-4%. Pitch and roll of Subject III were significantly larger than Subjects I and II (P<0.001), but yaw of Subject: III was significantly smaller than Subject: II (P<0.01) during tapping. Pitch and yaw of "good" was significantly smaller than "average" in the stability of the dentures (P<0.001). But roll of "average" was significantly smaller than "good" (P<0.05). Pitch and yaw of "B" was significantly smaller than "C" in the type of maxillary ridge (P<0.001). But roll of "C" was significantly smaller than "B" (P<0.05). CONCLUSIONS: The measurement accuracy of this system was equivalent to that of 3-D motion capture system by four infrared TV cameras. The measuring system using the IMU is reliable and easy to analyze the attitude angle of the denture during function. It may serve a diagnostic appliance to evaluate the quality of the denture.

Intelligent regulation scheme of the gastrointestinal delivery capsule's driving force / 国际生物医学工程杂志

Objective To intelligently adjust the driving force of a remote-controlled drug delivery capsule based on the postural information in intestines,so as to achieve the control of speed and dosage of drug delivery and reduce the energy consuming.Methods A six-axis sensor MPU6050 was used,and its Z axis was coincident with the central axis of the drug delivery capsule so as to made the medicine discharge port pointing to the Z direction.The angular velocities and accelerations of X,Y,Z axes were monitored,transformed to quaternion with built-in digital motion processor,and then converted to Euler angle form.The intelligence adjustment of driving force could be achieved by accessing the real-time attitude angle of the capsule.Results The results of experiments showed that the error between the actual and the attitude angle measured by the sensor was less 1°.Conclusions The intelligent adjustment scheme of driving force of a gastrointestinal remote-controlled drug delivery capsule was designed.The real-time attitude angles of the capsule could be obtained with high spped and precision.This study can provide the theoretical and experimental basis for the intelligent adjustment of the driving force.

Research progress of human's attitude angle measurement methods based on inertial sensors / 医疗卫生装备

Multiple methods of attitude measureinent based on inertial measurement unit (IMU) were summarized.The single sensor's means of attitude measurement and it's relative merits were introduced.What's more,the combined method applied to attitude measurement were highlightedly mentioned.In addition,the ways of attitude measurement with multi-sensors units were listed.It also gave useful recommendations for better selection with regard to specific application.The prospect of IMU applied on human bodies was analysed.