RÉSUMÉ
The single-axis rotary inertial navigation system can use the rotary joint to compensate the drift error of the inertial components. Therefore, whether the signal can be transmitted in the rotary joint freely, accurately, for a long time, and without maintenance determines the accuracy of inertial navigation. A noncontact slip ring based on capacitive coupling and quasitime division multiplexing is proposed in this paper. First, the theoretical calculation is carried out on the method of signal transmission using two pairs of capacitors, and the factors affecting signal quality are analyzed. Second, the principle of quasitime division multiplexing and Manchester encoding is used to solve the problems such as converting multiple signals into a single signal, capacitor cannot transmit DC signal, and signal synchronization. Finally, an improved differential transmission method is designed to enhance the anti-interference of the system and to solve the level mismatch of the primary and secondary circuits. In this paper, a prototype is designed to verify the method. When the transmission rate of the three navigation signals is 1 Mbps, the navigation signals can be transmitted without distortion. And the maximum transmission frequency is 17 MHz, which can be further improved. The experimental results show that the proposed method provides a new design for the signal transmission of noncontact power slip ring. It has the advantages of high reliability, fast transmission rate, and good versatility. It can be applied to aviation, aerospace, navigation, wind power generation, and other fields where the power and signal need to be transmitted simultaneously.
RÉSUMÉ
OBJECTIVE: To compare the effectiveness of the arthroscopic anterior cruciate ligament (ACL) reconstruction with the transtibial technique and through anteromedial approach. METHODS: Between April 2008 and May 2012, 86 patients (86 knees) with ACL rupture underwent single bundle reconstruction with autogeneic hamstring tendons with the transtibial technique in 44 cases (group A) and through anteromedial approach in 42 cases (group B). There was no significant difference in age, gender, injury causes, injury to admission time, preoperative International Knee Documentation Committee (IKDC) score, and Lysholm score between 2 groups (P > 0.05). The femoral and tibia tunnels were measured by X-ray films and CT. The knee stability and function were evaluated by Lachman test, pivot shift test, IKDC score, and Lysholm score. RESULTS: The patients were followed up 1-2 years (mean, 1.5 years) in group A and 1 year-1 year and 6 months (mean, 1.2 years) in group B. No limitation of knee motion was observed. The Lysholm score and IKDC score were significantly increased at 1 year after operation when compared with preoperative scores in 2 groups (P < 0.05), but no significant difference was found between 2 groups (P > 0.05). At 1 year after operation, the stability of the knee in group B was significantly better than that in group A, and the results of Lachman test and pivot shift test showed significant differences between 2 groups (P < 0.05). The femoral tunnel in group A was significantly longer in length and bigger in coronal angles and sagittal location than that in group B (P < 0.05). CONCLUSION: ACL reconstruction through anteromedial approach is a surgical technique to be closer to anatomy reconstruction, which can obtain better rotation function and stability of the knee than the transtibial technique.