Reference trajectory analysis and trajectory control by bank angle for re-entry vehicle

The re-entry problem consists of guidance design and trajectory control. This paper summarizes the detailed relationships between the velocity, drag acceleration and altitude in determining reference trajectories. The computational issues are also addressed, and the performance of the proposed simple nonlinear control of a bank angle for the longitudinal/lateral trajectory is demonstrated. In particular, the fixed bank angle methods that can reduce the drag acceleration errors at low-speeds are proposed. The importance of bank reversals with respect to the azimuth errors is also elucidated.     

An improved model-based predictive control of vehicle trajectory by using nonlinear function

A new model-based predictive control algorithm for vehicle trajectory control is proposed by using vehicle velocity and sideslip angle. Based on the error function combined with vehicle velocity and side slip of a bicycle model, a predictive control method has been proven to be useful on low velocity. Thus, it could be applied for an autonomous vehicle without a driver. Although an autonomous robot is not necessary to be driven with a high velocity, a commercial vehicle has to be driven at high velocity. Thus the previous predictive control formulation is not enough for a commercial driving system. This study is proposed to enhance the capacity of the predictive controller for rather high speed vehicles. This paper was presented at the 4th Asian Conference on Multibody Dynamics(ACMD2008), Jeju, Korea, August 20–23, 2008. Mr. Jeong-Han Lee is pursuing a Ph.D. degree in Mechanical Engineering at Pusan National University under the supervision of professor Wan-Suk Yoo. His research interests are focused on the area of adaptive control using multibody dynamics. Dr. Wan-Suk Yoo received his Ph.D. degree in 1985 from the University of Iowa. In 1994, he became a full professor at the Pusan National University, and he was selected an ASME fellow. He is serving as a vicepresident of the KSME.     

水下运载器纵向轨迹自适应跟踪控制

针对强非线性、大俯仰角运动的水下运载器纵向运动轨迹跟踪问题提出了一类非线性自适应控制方案.首先,直接采用非线性运动模型,在控制器设计过程中引入饱和函数,通过麦克劳林展开公式避免了俯仰角为小角度的假设限制;其次,考虑到运载器非线性运动模型很难给出精确的数学描述并且实际运载器系统存在模型误差,采用在线自适应方法近似逼近其非线性模型;最后,利用Backstepping方法设计了非线性自适应控制器,并利用Lyapunov理论证明了控制系统的稳定性.半实物仿真结果表明:在考虑测量噪声和参数不确定性的情况下,该算法对给出的3种轨迹的跟踪误差均小于0.5m,俯仰舵偏均小于15°,俯仰力矩均在105 N.m量级.结果验证了本文提出的控制系统鲁棒性强,满足跟踪性能要求.     

运用网格法对汽车梯形转向机构的优化设计

汽车转向机构直接影响汽车操纵稳定性、安全性和轮胎使用寿命。优良的转向机构,可以使汽车转弯行驶时,车轮作无滑动的纯滚动运动,以减少轮胎磨损和动力消耗[1]。探讨高等机构学在乘用车梯形转向机构优化设计问题的应用,在基于空间机构的原理上所建立的模型能较为全面地反映汽车转向特性,以C型汽车为原型探讨了汽车前轮转向梯形机构的优化设计问题。     

基于正交试验设计的客车车身结构优化研究

应用MSC.Nastran软件对某客车车身骨架结构进行四种不同工况下的截面尺寸优化,然后采用正交试验设计方法,分析了四种优化工况结果在综合优化分析中所占的最优权重,确定了最优的综合优化方案.通过对综合优化后的车身结构进行分析校核可以确认,引入正交试验设计方法进行结构综合优化,可以在确保大客车车身刚度、强度和模态等性能指标的前提下,实现结构多工况优化设计和车身结构的轻量化.     

基于解轨迹多项式系数估计的非线性电路故障诊断

本文针对一类斜波激励响应轨迹（解轨迹）存在的弱非线性电路,提出一种基于解轨迹多项式拟合的非线性电路故障诊断方法.本文在电路混合节点方程基础上,通过解轨迹多项式系数迭代关系分析多项式系数与故障信息间的对应关系;由解轨迹多项系数间存在的由低到高的解耦关系导出基于多项式系数的故障诊断方程,将非线性电路故障诊断转换为一组线性电路故障诊断问题.以解轨迹多项式系数为特征的故障诊断方法能有效减少故障传播的非线性造成的故障特征重叠、交叉现象,并可充分利用电路结构信息实现故障隔离;文中同时给出了基于解轨迹多项式系数聚类性分析的测试点优化准则.该方法具有分析过程简单、分析动态范围大和适用于未知非线性电路故障诊断等特点.最后通过实例仿真说明该方法的有效性.     

Trajectory optimization and the control of a re-entry vehicle in TAEM phase

This paper investigates the optimal trajectory and the feedback linearization control of a re-entry vehicle during TAEM (terminal area energy management) phase. First, an optimization algorithm with dynamic pressure as the cost function is used to obtain the optimal trajectory in TAEM. This optimal trajectory is considered the reference for ensuring a stable flight path of the re-entry vehicle. The control inputs are the angle of attack and bank angle, which determine the total energy and safety of the re-entry vehicle. Second, feedback linearization is used to design a tracking law in the TAEM phase. This paper validates the optimal solution as the reference trajectory with HAC (heading alignment cylinder) and the tracking performance of the re-entry vehicle onto the reference trajectory by feedback linearization.     

Trade-off analysis in multi-objective optimization using Chebyshev orthogonal polynomials

In this paper, it is intended to introduce a method to solve multi-objective optimization problems and to evaluate its performance. In order to verify the performance of this method it is applied for a vertical roller mill for Portland cement. A design process is defined with the compromise decision support problem concept and a design process consists of two steps : the design of experiments and mathematical programming. In this process, a designer decides an object that the objective function is going to pursuit and a non-linear optimization is performed composing objective constraints with practical constraints. In this method, response surfaces are used to model objectives (stress, deflection and weight) and the optimization is performed for each of the objectives while handling the remaining ones as constraints. The response surfaces are constructed using orthogonal polynomials, and orthogonal array as design of experiment, with analysis of variance for variable selection. In addition, it establishes the relative influence of the design variables in the objectives variability. The constrained optimization problems are solved using sequential quadratic programming. From the results, it is found that the method in this paper is a very effective and powerful for the multi-objective optimization of various practical design problems. It provides, moreover, a reference of design to judge the amount of excess or shortage from the final object.     

基于AVR MCU的车辆轨迹通讯仪的设计

为了对物流企业车辆实现可视化管理,降低物流费用.采用AVR MCU、GPRS MODEM、GPS开发了车辆轨迹通讯仪.轨迹通讯仪以GPRS的方式,每隔60S向物流信息中心发送一次位置信息,以UTC时间为序,保存于SQL SERVER数据库中.其它软件可根据所需要的精细程度,提取部分关键点,形成车辆轨迹.该产品投入应用后,能够帮助物流公司合理调配车辆,组织货源,改善服务质量,提高物流绩效.     

正交试验设计的硬钢群钻几何参数优化分析

针对硬钢材料硬度高、强度大和导热性差等材料特性,通过正交试验设计法进行群钻基础钻削试验,分析和研究外刃顶角2ρ、后角αfc和尖宽bφ三种钻尖参数对钻头寿命的影响,并进行方差分析及显著性检验,然后对研究结果进行单因素分析验证。其结果表明:在三种钻尖参数中,外刃顶角对群钻钻头寿命起决定性作用;通过相关优化分析获得了在硬钢材料钻削中,群钻钻尖的最优几何参数。     

Cutting edge orthogonal contact-zone analysis using detailed tool shape representation

A new method for numerically controlled (NC)-simulation-based numerical analysis of the tool-workpiece contact area in cutting processes is presented. To gain enhanced knowledge about tool-workpiece interaction, determination of chip thickness, contact length, and resulting cross-section area of the undeformed chip is of major interest. Compared to common simulation approaches, where rotationally symmetrically constructed tool shape is used, the new method uses a detailed three-dimensional tool shape model for an extended and more accurate contact zone analysis. As a corresponding representation of the workpiece and its time-dependent change of shape, a multidexel model is used. To perform contact zone analysis, each cutting element and a multidexel model are intersected in discrete time steps corresponding to the tool rotation. Subsequently, the intersection point of each dexel is mapped on the local coordinate system of the cutting geometry. The parametric cutting geometry allows a direct computation of local cutting depth and contact length for each involved point. Based on the local values of contact length and cross section area of the undeformed chip, the characteristic values for the entire contact zone are calculated and used to predict mechanical loads caused by the cutting process. To demonstrate the application of the novel approach, a prediction of forces in slot milling and drilling of 1.1191 steel (C45EN) is presented.     

Quaternion-based nonlinear trajectory tracking control of a quadrotor unmanned aerial vehicle

At present, most controllers of quadrotor unmanned aerial vehicles(UAVs) use Euler angles to express attitude. These controllers suffer a singularity problem when the pitch angle is near 90°C, which limits the maneuverability of the UAV. To overcome this problem, based on the quaternion attitude representation, a 6 degree of freedom(DOF) nonlinear controller of a quadrotor UAV is designed using the trajectory linearization control(TLC) method. The overall controller contains a position sub-controller and an attitude sub-controller. The two controllers regulate the translational and rotational motion of the UAV, respectively. The controller is improved by using the commanded value instead of the nominal value as the input of the inner control loop. The performance of controller is tested by simulation before and after the improvement, the results show that the improved controller is better. The proposed controller is also tested via numerical simulation and real flights and is compared with the traditional controller based on Euler angles. The test results confirm the feasibility and the robustness of the proposed nonlinear controller. The proposed controller can successfully solve the singularity problem that usually occurs in the current attitude control of UAV and it is easy to be realized.     

Sliding mode based trajectory linearization control for hypersonic reentry vehicle via extended disturbance observer

This paper proposes a novel hybrid control framework by combing observer-based sliding mode control (SMC) with trajectory linearization control (TLC) for hypersonic reentry vehicle (HRV) attitude tracking problem. First, fewer control consumption is achieved using nonlinear tracking differentiator (TD) in the attitude loop. Second, a novel SMC that employs extended disturbance observer (EDO) to counteract the effect of uncertainties using a new sliding surface which includes the estimation error is integrated to address the tracking error stabilization issues in the attitude and angular rate loop, respectively. In addition, new results associated with EDO are examined in terms of dynamic response and noise-tolerant performance, as well as estimation accuracy. The key feature of the proposed compound control approach is that chattering free tracking performance with high accuracy can be ensured for HRV in the presence of multiple uncertainties under control constraints. Based on finite time convergence stability theory, the stability of the resulting closed-loop system is well established. Also, comparisons and extensive simulation results are presented to demonstrate the effectiveness of the control strategy.     

基于MATLAB的喷涂轨迹重叠率优化

用高速静电旋杯式喷涂系统进行喷涂时,涂料雾化后的微粒在工件表面上形成的沉积模型具有多种形状。在详细分析多种涂料沉积模型的基础上,对β型沉积分布模型函数进行充分研究,推导出包含涂料漆流底面半径R、调整系数K,喷枪移动速度v及喷涂流量Q0等主要参数在内的平面喷涂的涂层沉积厚度方程;基于该涂层趁机厚度方程,用MATLAB语言编写程序对两条相邻喷涂轨迹之间的重叠距离进行优化,并得出优化结果,为喷漆机器人轨迹规划设计奠定了基础。     

基于MATLAB的优化分析与计算

以应用实例说明，使用优化工具函数进行无约束优化问题和约束优化问题的分析和计算，具有良好的通用性、有效性和简便性，可以快速获得优化过程信息和结果。     

A global optimal sliding-mode control for the minimum time trajectory tracking with bounded inputs

A new design of the sliding mode control is proposed for the uncertain linear time-varying second order system. The proposed control drives system states to the target point in the minimum time with specified ranges of parametric uncertainties and disturbances, One of the advantages of the proposed control scheme is that the control inputs do not go beyond saturation limits of the actuators. The other advantage is that the minimum arrival time and the acceleration of the second order actuators system can be estimated with given parametric bounds and can be expressed in the closed form; conversely, the designer can select actuators based on the condition of the minimum arrival time to the target point. The superior performance of the proposed control scheme to other sliding mode controllers is validated by computer simulations.     

基于CFD的轿车发动机舱前端流场优化

为解决流场中的问题,采用CFD方法,对某汽车发动机舱内的前端局部流场进行分析,包括:机舱前端设计不合理,存在漏风、热气回流等。基于CFD的分析结果,有针对性地提出了多个优化方案,对前端模块,风扇进行重新设计,并增设导流板,解决了上述问题,提高了冷却模块的流量。     

Quantitative analysis of vehicle particle emission by using calibrated CPC system

Particle size distribution and particle number concentration from diesel engines are subjects of significant environmental concerns especially in the EU. A few years ago, the UN-ECE PMP proposed a method for measuring particle emissions in the diluted exhaust of internal combustion engine vehicles, which has become a key method used in new dilution systems and sampling condition. This paper describes the effects of parameters such as condensation particle counter (CPC) according to test procedures, test fuel and vehicle test mode, including NEDC and CVS-75 mode. The main results obtained from this study can be summarized as follows: (1) Periodic calibration of the CPC system is essential because the long-term usage of a CPC leads to an underestimation in the measurements of small particles. (2) Particle emissions measured by the UN-ECE PMP method were found to exhibit comparable repeatability as compared to other regulated emissions. (3) In particle number concentration emitted from different-fueled vehicles, the sources of particle emissions in an ascending order of magnitude are as follows: DPF equipped diesel passenger vehicles, gasoline and LPG fueled vehicles, and DPF unequipped diesel passenger vehicles. Also, we found that the particle numbers of DPF equipped diesel passenger vehicles, gasoline and LPG-fueled vehicles can meet the EU regulation limit (<6.0×10¹¹#/km), while DPF unequipped diesel passenger vehicles do not meet the EU limit.     

Fatigue life analysis of wheels on guideway vehicle using multibody dynamics

A guideway vehicle is used in automobile, semiconductor and LCD manufacturing industries to transport products efficiently. Since the operating speed of the guideway vehicle should be increased for maximum productivity, the weight of the vehicle has to be reduced, and this weight reduction may cause a failure of a part in the system. Therefore, the estimation of the fatigue life of the parts becomes an important problem. In this study, the fatigue life of the wheels in the guideway vehicle is estimated using an S-N curve. To obtain the fatigue life of a part, the S-N curve, the dynamic stress time history applied to the part, and the material property of the part are required. The S-N curve of the driving wheel is obtained from the fatigue experiment on wheels. To obtain the material properties of the driving wheel, which is composed of aluminum with urethane coating, the result of a compression hardware test and static analysis of the wheel’s FE model are used. The dynamic stress time history influencing the driving wheel can be obtained from linear superposition of the dynamic load time history and the static stress. The dynamic load time history is estimated by multibody dynamic analysis, and the static stress is obtained by finite element analysis.     

焊接机器人运动学分析及轨迹规划研究

针对梁构、石化容器等大型焊件普遍存在的焊接难的问题,研制了一种新型7自由度大型焊接机器人.首先,分析了该机器人的机械结构,基于D-H坐标系理论建立了机器人的运动学方程,并对该方程进行了求解,得到了其运动学正反解;其次,在关节空间内,采用过路径点的三次多项式插值方法,结合机器人操作空间运动参数对关节轨迹插值计算,实现了对机器人关节空间的轨迹规划;最后,在Matlab7.8平台上,利用机器人工具箱建立了该机器人模型,并且对机器人运动学、轨迹规划进行了仿真分析.仿真及研究结果表明:该机器人各连杆参数的设计是合理的,在关节空间内利用三次多项式进行轨迹规划具有可行性;同时,这也为机器人动力学的研究打下了基础.目前该技术已应用于机器人的点焊及角焊的现场作业中.