基于伪谱法的神经网络制导控制器设计

针对可重复使用运载火箭(Reusable Launch Vehicle,RLV)再入段制导周期长和弱鲁棒性问题,提出一种基于hp自适应伪谱法的神经网络制导控制器。首先建立RLV再入段的弹道优化模型,利用hp自适应伪谱法离线进行弹道优化,得到有干扰和标准条件下的多条最优弹道数据,构成RLV再入段状态量x、y、z、vx、vy、vz和控制量α、β的样本库;再用样本库训练BP神经网络,得到神经网络制导控制器;最后对RLV再入段进行仿真验证,结果表明:存在初值偏差和环境干扰的条件下,制导周期小于0.01 s且制导误差较小,该控制器鲁棒性强、有工程应用价值。

H_∞ Robust Fault-Tolerant Controller Design for an Autonomous Underwater Vehicle’s Navigation Control System

In order to improve the security and reliability for autonomous underwater vehicle （AUV） navigation, an H∞ robust fault-tolerant controller was designed after analyzing variations in state-feedback gain Operating conditions and the design method were then analyzed so that the control problem could be expressed as a mathematical optimization problem. This permitted the use of linear matrix inequalities （LMI） to solve for the Hv controller for the system. When considering different actuator failures, these conditions were then also mathematically expressed, allowing the H∞ robust controller to solve for these events and thus be fault-tolerant. Finally, simulation results showed that the H∞ robust fault-tolerant controller could provide precise AUV navigation control with strong robustness.

Integrated Product and Process Control for Sustainable Semiconductor Manufacturing

Semiconductor fabrication is a manufacturing sequence with hundreds of sophisticated unit operations and it is always challenged by strategy development for ensuring the yield of defect-free products.In this paper,an advanced control strategy through integrating product and process control is established.The proposed multiscale scheme contains three layers for coordinated equipment control,process control and product quality control.In the upper layer,online control performance assessment is applied to reduce the quality variation and maximize the overall product performance （OPP）.It serves as supervisory control to update the recipe of the process controller in the middle layer.The process controller is designed as an exponentially weighted moving average （EWMA） run-to-run controller to reject disturbances,such as process shift,drift and tool worn out,that are exerted to the op-eration.The equipment in the process is individually controlled to maintain its optimal operational status and maximize the overall equipment effectiveness （OEE）,based on the set point given by the process controller.The ef-ficacy of the proposed integrated control scheme is demonstrated through case studies,where both the OPP （for product） and the OEE （for equipment） are enhanced.

Automatic Guidance of an Agricultural Tractor along with the Side Shift Control of the Attached Row Crop Cultivator

This paper presents the automatic guidance system of an agricultural tractor and the side shift control of the attached row crop cultivator using electro-hydraulic actuators. In order to simulate the dynamic behaviour of the tractor along with the attached cultivator, the modified bicycle model was adopted. Steering angle sensor, fibre optic gyroscope （FOG） and RTK-DGPS technologies are assumed for measurements of the steering angle, yaw rate and the lateral position of the tractor, respectively. The kinematics model was used for the implement. In this study four cascade controllers were designed and simulated for tractor guidance which consists ofPD, PD, P and PID controllers. Other PI and PID controllers also had been designed for implement side shifting purpose. Then, these two systems were combined and the performance of the whole system was evaluated through the simulation results. According to the results tractor reaches the desired path after less than 10 seconds. Simulations showed that the maximum deviation of the tractor from the desired path was about 5 cm within this period. And the cultivator blades would follow the predetermined path with steady state error of about 5 cm too.

Steering Multiple Reverse Current into Unidirectional Current in Deterministic Ratchets

Recent investigations have shown that with varying the amplitude of the external force, the deterministic ratchets exhibit multiple current reversals, which are undesirable in certain circumstances. To control the multiple reverse current to unidirectional current, an adaptive control law is presented inspired from the relation between multiple reversaJs current and the chaos-periodic/quasiperiodic transition of the transport velocity. The designed controller can stabilize the transport velocity of ratchets to steady state and suppress any chaos-periodic/quasiperiodic transition, namely, the stable transport in ratchets is achieved, which makes the current sign unchanged.

Movability of the tracked pipeline-robot based on hierarchical fuzzy control

The turning motion of a tracked pipeline-robot implemented by skid steering is a nonholonomic dynamic problem with intrinsic nonlinearity, to which the classical control method is inappropriate and cannot be applied. This paper presents a novel path tracking control method based on hierarchical fuzzy structure. The controller consists of three sub-level low dimensional fuzzy control systems： fuzzy supervisory control, fuzzy steering and fuzzy velocity control. As a result, establishing the bases of rules for the fuzzy control becomes feasible and simplified, and the related controller can be adapted to complicated ground and environment. Using this method, the number of fuzzy controt rules is greatly decreased so that the curse of dimensionality causing the multivariable problem does not occur. Simulation and experimental results validate the effectiveness of the proposed method with satisfied performance on path tracking. Autonomous navigation of the caterpillar-inspired pipeline-robot is also implemented based on the sensor feedbacks.

STATE DERIVATIVE-FREE VARIABLE STRUCTURE MODEL REFERENCE ADAPTIVE CONTROL OF LINEAR PARABOLIC SYSTEMS

The problem of constructing a model dimensional parabolic system is considered in this reference adaptive control law for an uncertain 1- article. The controller designed here involves only the plant state but no its derivatives. A priori bounds on the plant＇s uncertain parameters are used to propose switching laws which serve as an adaptive mechanism. The exponential decay to zero of the state error with any prescribed rate is guaranteed by choosing a controller parameter correspondingly. Numerical studies are also presented to illustrate the applicability of the control law.