Applications of integrated motion controllers for precise CNC machines

The error resources of precise motion control systems are basically categorized into linear and nonlinear effects. To realize the precise motion of industrial computer numerical control (CNC) machines, this paper presents an integrated motion control structure with modular algorithms, including both the linear control and the nonlinear compensation. In the linear control design, this study applies three algorithms: (1) feedforward control to address the tracking errors, (2) cross-coupled control to reduce the contouring errors, and (3) digital disturbance observer to lessen the effects of modeling errors and disturbances in real applications. The results indicate that the linear motion controller achieves greatly improved accuracy in both tracking and contouring by reducing the servo lags and mismatched dynamics of the different axes. However, the adverse effect due to friction still exists and cannot be eliminated by applying the linear motion controller only. This study further integrates the nonlinear compensator and develops friction estimation and compensation rules for CNC machines. The digital signal processors are suitable to implement all the developed linear and nonlinear algorithms, and the present controllers have been successfully applied to industrial CNC machines. Experimental results on a vertical machining center indicate that, under different feed rates, the CNC machine with the integrated motion controller significantly reduces the maximum contouring error by 135% on average.     

基于模糊逻辑的AFS／DYC集成控制策略研究

文中所研究的汽车动态控制系统是基于模糊逻辑控制的主动前轮转向（AFS）和直接横摆力矩控制（DYC）的集成。控制系统采用分层控制。上层使用模糊逻辑控制器（横摆角速度控制器）,输入为横摆角速度偏差及其变化率,其输出为直接横摆力矩控制信号和前轮修正转向角;下层（模糊集成控制器）设计了基于轮胎侧向力工作区的模糊逻辑控制器,通过调整前轮侧向力的方向,激活切换函数来调节模糊逻辑控制器的比例因子。仿真结果表明,使用非线性七自由度车辆模型,与单独的AFS或DYC控制器相比较,使用集成AFS／DYC控制系统,汽车操纵稳定性得到了很大的改善。     

电机运行监控系统的设计与实现

设计了针对电机运行的监控系统。主要介绍了由PC与PLC组成的监控系统以及它们之间的通信协议。运行结果表明:该系统能实时调节、显示电机转速,监控其运行。该系统构成成本低,具有可移植性、灵活性和实用性。     

Direct yaw moment control for distributed drive electric vehicle handling performance improvement

For a distributed drive electric vehicle (DDEV) driven by four in-wheel motors, advanced vehicle dynamic control methods can be realized easily because motors can be controlled independently, quickly and precisely. And direct yaw-moment control (DYC) has been widely studied and applied to vehicle stability control. Good vehicle handling performance: quick yaw rate transient response, small overshoot, high steady yaw rate gain, etc, is required by drivers under normal conditions, which is less concerned, however. Based on the hierarchical control methodology, a novel control system using direct yaw moment control for improving handling performance of a distributed drive electric vehicle especially under normal driving conditions has been proposed. The upper-loop control system consists of two parts: a state feedback controller, which aims to realize the ideal transient response of yaw rate, with a vehicle sideslip angle observer; and a steering wheel angle feedforward controller designed to achieve a desired yaw rate steady gain. Under the restriction of the effect of poles and zeros in the closed-loop transfer function on the system response and the capacity of in-wheel motors, the integrated time and absolute error (ITAE) function is utilized as the cost function in the optimal control to calculate the ideal eigen frequency and damper coefficient of the system and obtain optimal feedback matrix and feedforward matrix. Simulations and experiments with a DDEV under multiple maneuvers are carried out and show the effectiveness of the proposed method: yaw rate rising time is reduced, steady yaw rate gain is increased, vehicle steering characteristic is close to neutral steer and drivers burdens are also reduced. The control system improves vehicle handling performance under normal conditions in both transient and steady response. State feedback control instead of model following control is introduced in the control system so that the sense of control intervention to drivers is relieved.     

一种双轴直驱平台新型同步渐近跟踪控制设计

针对双轴直驱平台伺服系统中存在同步进给的问题,提出一种交叉耦合迭代学习控制器与自适应加加速度控制器相结合的新型同步控制方法。首先,构建同步误差,利用交叉耦合控制器解决双轴的耦合问题;设计自适应PD型学习律减小同步误差,实现双轴协调同步。采用模型前馈控制补偿系统的参数不确定性,提高系统的响应速度。自适应加加速度控制器抑制系统中外部扰动、摩擦力等不确定性因素,实现系统的渐近跟踪控制。加加速度积分后形成反馈控制律,保证了控制信号的稳定性和连续性。设计自适应更新律,使鲁棒增益实现指数收敛并削弱测量噪声对系统的影响,增强系统的鲁棒性。系统实验结果表明,该方法能够明显地提高系统的同步性能,改善双轴直驱平台伺服系统的控制精度。     

Error detection and recovery in flexible assembly systems

This study investigates error detection and recovery for flexible assembly systems. A method for error recovery based upon an expert system is presented. An expert system is used to control the assembly cell, but the robot controller controls the assembly operation. This ensures adequate speed of the assembly cycle. The robot signals the expert system when an error occurs. It determines the cause of the error and recommends a preprogrammed recovery procedure to correct the error automatically. The system is flexible and new error recovery routines are easily added to the system. The proposed method was implemented in the Mark II assembly cell at 1VF-KTH in Stockholm. The reliability of the assembly cell increased considerably after installation of the error detection and recovery system. The error detection did not affect the cycle time and error recovery took less than 10 seconds on average.     

整车非线性系统的输入输出解耦及解耦比例微分控制

根据非线性解耦控制理论设计出解耦控制器,以消除装有主动悬架(ASS)和电动助力转向(EPS)的集成控制器中控制通道的耦合和路面不平度的干扰.为进一步减少响应时间和跟踪误差并降低超调量,在解耦控制器的基础上,设计出动态响应较为理想的解耦比例微分(PD)控制器.仿真结果表明,基于解耦控制的ASS EPS集成系统,与未集成的ASS或EPS系统相比,前者能更好地改善汽车动力学特性.此外,解耦PD控制与单独的解耦控制相比,在改善整车的行驶平顺性和操纵稳定性等方面效果也更为明显.为验证理论分析和仿真计算的正确性,进行实车道路试验,试验采用自行设计的ASS EPS集成控制系统,试验结果与仿真计算结果基本吻合,进一步验证了所提方法是正确有效的.     

Contouring accuracy improvement using a tangential contouring controller with a fuzzy logic-based feedrate regulator

In contour-following tasks, contour error reduction is an issue of much concern. Generally speaking, contour error is caused by the mismatched dynamics between each axis. To reduce the contour error, many previous studies have focused on developing proper controllers and/or more accurate contour error estimation algorithms. An alternative method for reducing contour errors is to exploit the idea of desired feedrate adjustment. This paper proposes using the approximate contour error information to develop a fuzzy logic-based feedrate regulator, which adjusts the value of the desired feedrate. Moreover, to further reduce contour error, an integrated motion control scheme is also developed. This scheme consists of a position loop controller with velocity command feedforward, a tangential contouring controller (TCC), a real-time contour error estimator, and the proposed fuzzy logic-based feedrate regulator. Several experiments on free-form contour-following tasks are conducted to evaluate the performance of the proposed approach. The experimental results clearly demonstrate the effectiveness of the proposed approach.     

基于力外环的模糊灰色预测力控制器

在基于位置环的显式力控制方案的框架内,提出一种新型模糊灰色预测力控制策略。采用灰色预测器来预测将来的接触力,通过模糊增益调节器将预测的接触力误差和实际测得的当前接触力误差进行合成形成一个综合接触力误差,综合接触力误差作为PID或PI力补偿器的输入变量,力补偿器生成位置控制系统的输入指令。这样该控制器可以利用过去、当前和将来的接触力信息来计算合适的控制校正量来对接触力误差进行预补偿,使控制器可以同时获得超调量小和响应快速的性能。而且,该控制器可以按照当前和将来的接触力状态来调节预测的接触力误差和实际测得的当前接触力误差的权值,使控制器对机器人和环境之间的动态接触过程具有适应性。最后用仿真试验证明所提出的模糊灰色预测力控制器的有效性。     

光纤透镜研磨抛光的轮廓成形控制系统的研究

为了有效地减小光纤透镜的研磨抛光轮廓误差,设计一种两轴联动的交叉耦合轮廓控制器,并且针对光纤透镜研磨抛光机床的运动特点,给出了交叉耦合轮廓误差模型.然后利用Matlab软件对该交叉耦合轮廓控制的效果进行了仿真研究与分析.仿真结果表明,利用该控制器能使系统轮廓误差从0.075 μm减小到0.03 μm,但由于加入了交叉耦合器的补偿量,Z轴的跟随误差也从0.05 μm增大到0.07 μm.同时也表明两轴联动的交叉耦合控制系统远远优于单轴PID控制系统.     

多变量主动悬架系统的一种自适应神经元控制策略

研究了车辆主动悬架这个多变量不确定系统的自适应控制问题。提出了一种新型的单神经元多变量控制器。给出一种综合误差的概念,将综合误差与传统的单神经元控制器相结合,得到一种基于综合误差理论的单神经元控制器,它可以同时直接调控被控对象的多输出变量。将该控制方法应用于1/4主动悬架系统,采用二次型性能指标对控制器参数进行了优化设计。研究了在不同的悬架参数及随机路面输入情况下控制器的自适应性能,并与被动悬架及传统神经元控制的主动悬架进行了性能对比。仿真结果表明,所提出的控制器可使车辆获得更为优良的综合减振性能,可显著改善平顺性,是一种简单有效且鲁棒性较好的自适应控制器。该控制方法为主动悬架及类似的多变量不确定系统的控制提供了一种可能的简捷有效的新途径。     

基于PSO自整定PID控制器的柔性臂振动控制

针对压电柔性机械臂运行过程中的弹性振动问题,提出了基于粒子群优化算法（particle swarm optimization,简称PSO）自整定比例积分微分（proportional integral differential,简称PID）控制器参数的柔性臂振动抑制方法。采用标准粒子群优化算法,以时间乘绝对误差积（integrated time and absolute error,简称ITAE）准则为适应度函数,整定PID控制器的3个控制参数K-p,K-i和K-d,并采用Matlab Simulink平台建立双连压电柔性机械臂振动控制仿真模型,研制基于虚拟仪器技术的柔性臂振动控制试验系统。仿真与试验结果表明,采用常规PID控制算法和基于PSO自整定的PID控制算法均能有效地抑制柔性机械臂的弹性振动,但后者的振动抑制效果、鲁棒性与稳定性优于前者。     

低压电流互感器综合自动检测装置机械设计与实现

为解决低压电流互感器型式检验中电气试验人工操作过程频繁、劳动强度大、易发生误操作、电气接触不可靠及存在不安全、效率低、影响检测质量等问题,设计开发出了一种适用于实验室的多功能自动检测装置。装置设计为1个 "控制单元" 加2个 "检测单元" 的 "1+2" 一体化组合式结构,可同时检测两种规格互感器,实现了多品种互感器异步/并行多作业模式检测。结果表明,新型检测装置设计方案可行,运行可靠,达到了预期目标。     

Robust control of nonlinear integrated ride and handling model using magnetorheological damper and differential braking system

The interaction of the ride and handling systems is one of the challenging topics in vehicle dynamics and control. In this study the dynamic behavior of a passenger car considering coupling among all the fourteen degrees of freedom is modeled using Boltzmann Hamel equations. In order to improve the ride quality and stability of the vehicle, a Magnetorheological damper and a differential braking system are used as control devices. Based on the nonlinear integrated ride and handling vehicle model, a nonlinear H-infinity controller is designed for an intermediate passenger car. The dynamic behavior of the controlled vehicle is simulated for single lane change and bump input, considering three different road conditions: Dry, rainy and snowy. The robustness of the designed controller is investigated when the vehicle is under these road conditions. The simulation results confirm the interactive nature of the ride and handling systems and the robustness of the designed control strategy.     

Calculation of PID controller parameters by using a fuzzy neural network

In this paper, we use the fuzzy neural network (FNN) to develop a formula for designing the proportional-integral-derivative (PID) controller. This PID controller satisfies the criteria of minimum integrated absolute error (IAE) and maximum of sensitivity (Ms). The FNN system is used to identify the relationship between plant model and controller parameters based on IAE and Ms. To derive the tuning rule, the dominant pole assignment method is applied to simplify our optimization processes. Therefore, the FNN system is used to automatically tune the PID controller for different system parameters so that neither theoretical methods nor numerical methods need be used. Moreover, the FNN-based formula can modify the controller to meet our specification when the system model changes. A simulation result for applying to the motor position control problem is given to demonstrate the effectiveness of our approach.     

Control and dynamic releasing method of a piezoelectric actuated microgripper

This paper proposes the control and dynamic releasing method of a symmetric microgripper with integrated position sensing. The microgripper adopted in this micromanipulation system is constructed by two L-shaped leverage mechanisms and the fingers of the microgripper is machined much thinner than the gripper body. A combined feedforward/feedback position controller is established to improve the motion accuracy of the microgripper in high frequency. The feedforward controller is established based on rate-dependent inverse Prandtl-Ishlinskii (P–I) hysteresis model. The inertial force generated in dynamic based releasing process is analyzed through MATLAB simulation. Open-loop experimental tests have been performed, and the results indicate the first natural frequency of the microgripper is 730 Hz. Then experiments in high frequency based on the developed combined controller are carried out and the results show the tracking error of a superimposed sinusoidal trajectory with the frequency of 100 Hz, 120 Hz and 130 Hz is 6.4%. Finally, the tiny objects releasing experiments are conducted where the combined controller is used to control the motion amplitude and frequency to achieve inertial force controllable to improve operation accuracy. And the results show that the dynamic releasing strategy is effective.     

Contouring controller design for biaxial feed drive systems considering compliance of transmission mechanism

Contouring control is an effective method for computer numerical controlled machining, and various such designs have been proposed to date. However, the compliance of the transmission mechanism is not considered in most existent contouring controller designs. This paper presents a new contouring control system design considering the compliance of a transmission mechanism based on a fourth-order model of feed drive dynamics. First, we present a controller design that enables the controller gain assignment for reducing the error component orthogonal to the desired contour curve, independent of the tangential error component. Although this design provides better control performance with small control input variance, there exists an inherent contour error because of the difficulty in calculating the exact contour error for any contour curve in real time. To address this problem, a reference adjustment method is used to estimate the actual contour error. The effectiveness of the proposed design is experimentally verified by comparing the control performance with a design based on a plant model that neglects the compliance.     

Method for graphically evaluating the workpiece’s contour error in non-circular grinding process

To find and compensate the dynamic contour error of workpieces on CNC non-circular grinder, a graphic display and evaluation method is introduced. The programmed set and actual contours of workpiece are displayed through the outlines of grinding wheel at a series of set and actual positions. The dynamic contour error can be recognized directly on CNC control screen without extra measuring equipments as usual. The set and actual positions of grinding wheel related to workpiece are collected from the CNC controller and servo drives and further evaluated. This process is carried out after a dry-run cycle on the machine. Based on this method, a display and evaluation software module has been developed and integrated in the controller of a CNC non-circular grinder. It helps to find contour error and generate the compensation data. Grinding an eccentric test piece shows good result and advantage of the proposed method.     

模糊技术在PLC控制中的应用

针对控制系统装置的对象往往出现大时滞、非线性和难以建立精确数学模型等问题,提出将先进的模糊控制技术引入传统的自动化装置之中.模糊控制具有鲁棒性强等特点,可以使外界干扰和参数变化跳动对控制效果的影响大大减弱.从工程角度出发,采用西门子PLC常规输入/输出模块组成模糊控制器的核心,提出了相应可行的模糊控制算法,并采用了在线...