High-precision gyro-stabilized control of a gear-driven platform with a floating gear tension device

This study presents an improved compound control algorithm that substantially enhances the antidisturbance performance of a gear-drive gyro-stabilized platform with a floating gear tension device.The tension device can provide a self-adjustable preload to eliminate the gap in the meshing process.However,the weaker gear support stiffness and more complex meshing friction are also induced by the tension device,which deteriorates the control accuracy and the ability to keep the aim point of the optical sensors isolated from the platform motion.The modeling and compensation of the induced complex nonlinearities are technically challenging,especially when base motion exists.The aim of this research is to cope with the unmeasured disturbances as well as the uncertainties caused by the base lateral motion.First,the structural properties of the gear transmission and the friction-generating mechanism are analyzed,which classify the disturbances into two categories:Time-invariant and time-varying parts.Then,a proportional-integral controller is designed to eliminate the steady-state error caused by the time-invariant disturbance.A proportional multiple-integral-based state augmented Kalman filter is proposed to estimate and compensate for the time-varying disturbance that can be approximated as a polynomial function.The effectiveness of the proposed compound algorithm is demonstrated by comparative experiments on a gear-drive pointing system with a floating gear tension device,which shows a maximum 76%improvement in stabilization precision.

Calibration and Application of Actual Tension of Low Precision 20 High Mill

The rolling production of metal thin strips,especially the production of stainless steel and copper thin strips with high yield strength,due to the limitation of the minimum rolling thickness,multi roll mills with small working roll diameter are mostly used,and the 20 roll mill is the most common.Aiming at the problem that the actual tension of some 20 high rolling mills with long service time and low assembly accuracy has a large deviation from the set tension and is not accurate enough,this paper first designs the tension calibration device of the low precision 20 high rolling mill.Secondly,the calibration principle of the tension calibration device designed in this paper is described.Then,according to the calibration principle and specific implementation scheme,the actual tension tact of the strip steel is comprehensively determined,and the mapping relationship between the set tension tset and the actual tension tact of the 20 high mill is established,so as to improve the tension control accuracy of the 20 high mill and ensure the shape quality of the strip steel.

Generation mechanism and control of high-frequency vibration for tracked vehicles

A crawler system provides much larger ground contact,leading to excellent terrain adaptability.Due to its structural characteristics,high‐frequency vibration proportional to the vehicle speed is generated during the driving process.This is a result of the polygon and rolling effects between the track and the wheels.A field test of a tracked vehicle is performed to monitor movement signals of the chassis and a rocker arm.Their corresponding power spectral density distributions confirm the correctness of the frequency‐calculation equation.Then,a novel elastic track tensioning device with a damper is designed as a cushion between the idler and the chassis.Depending on its geometry,the equivalent damping coefficient for a dynamic model is evaluated.Subsequently,the damping is altered in response to different operating conditions by a hybrid damping fuzzy semiactive control system.The controller accounts for both chassis and track vibration.Based on the transfer matrix method for multibody systems,a dynamical model of the track system is developed.Control performances are evaluated using two numerical simulations of obstacle crossing and off‐road driving operations.Results indicate that the proposed semiactive tensioner is substantially better than the conventional one.This paper provides a novel feasible scheme for vibration reduction of tracked vehicles.

The Influence of Different Surgical Schemes on the Healing and Cosmetic Effects of Skin Lesions

Objective To analyze the effects of different surgical procedures on the healing and cosmetic effects of skin lesions.Methods 102 patients with skin defects after skin tumor resection in our hospital from January 2018 to December 2019 were selected and randomly divided into observation group and control group.The control group was treated with a traditional skin flap transplantation,while the observation group was treated with a skin stretch closure device.The effective rate,bleeding volume,wound healing time,total scar length,short-term and long-term complications and patient satisfaction were compared between the two groups.Results The effective rates of the observation group and the control group were 90.2%and88.24%,there was no significant difference in the treatment efficiency between the two groups(P>0.05),but there were significant differences in the amount of bleeding,the time of wound healing and the total length of postoperative scars between the two groups(all P<0.05);the short-term complication rates of the observation group and the control group were 5.88%and 19.61%,and long-term complications rate was 1.96%and 13.73%.The difference in the incidence of short-term and long-term complications between the two groups was statistically significant(all P<0.05);the satisfaction rate of patients in the observation group and the control group was 90.2%and 72.55%,the difference was statistically significant(P<0.05).Conclusion The former can effectively shorten wound healing time and scar length,reduce the incidence of short-term and long-term complications,and improve patients’satisfaction with the treatment,which is worthy of promotion.