【正文】 德才，孫明，許海平，何新智．磁懸浮球的實(shí)驗(yàn)研究[J]．運(yùn)城學(xué)報，[17] 上官霞南．永磁偏置磁懸浮球及其控制系統(tǒng)[D]．哈爾濱理工大學(xué)工程碩士學(xué)位論文，2007[18] 魏克新、王云亮、陳志敏．MATLAB語言與自動控制系統(tǒng)設(shè)計[M]．北京：機(jī)械工業(yè)出版社，2001[19] 徐渠．磁懸浮系統(tǒng)的控制[J]．研究科技創(chuàng)新導(dǎo)報，2008[20] 孫亮，楊鵬．自動控制原理[M]．北京：北京工業(yè)大學(xué)出版社，2006附 錄一、英文原文PID controller A proportional–integral–derivative controller (PID controller) is a generic control loop feedback mechanism(controller) widely used in industrial control systems –a PID is the most monly used feedback controller. A PID controller calculates an error value as the difference between a measuredprocess variable and a desired setp oint. The controller attempts to minimize the error by adjusting the process control inputs. In the absence of knowledge of the underlying process, PID controllers are the best controllers.[1] However, for best performance, the PID parameters used in the calculation must be tuned according to the nature of the system – while the design is generic, the parameters depend on the specific system. The PID controller calculation (algorithm) involves three separate parameters, and is accordingly sometimes calledthreeterm control: the proportional, the integral and derivative values, denoted P, I, and D. The proportionalvalue determines the reaction to the current error, the integral value determines the reaction based on the sum of recent errors, and the derivative value determines the reaction based on the rate at which the error has been changing. The weighted sum of these three actions is used to adjust the process via a control element such as the position of a control valve or the power supply of a heating element. Heuristically, these values can be interpreted in terms of time: P depends on the present error, I on the accumulation of past errors, and D is a prediction offuture errors, based on current rate of change. By tuning the three constants in the PID controller algorithm, the controller can provide control action designed for specific process requirements. The response of the controller can be described in terms of the responsiveness of the controller to an error, the degree to which the controller overshoots the setpoint and the degree of system oscillation. Note that the use of the PID algorithm for control does not guarantee optimal control of the system or system stability.Some applications may require using only one or two modes to provide the appropriate system control. This is achieved by setting the gain of undesired control outputs to zero. A PID controller will be called a PI, PD, P or I controller in the absence of the respective control actions. PI controllers are fairly mon, since derivative action is sensitive to measurement noise, whereas the absence of an integral value may prevent the system from reaching its target value due to the control action.Note: Due to the diversity of the field of control theory and application, many naming conventions for the relevant variables are in mon use.Control loop basics A familiar example of a control loop is the action taken when adjusting hot and cold faucet valves to maintain the faucet water at the desired temperature. This typically involves the mixing of two process streams, the hot and cold water. The person touches the water to sense or measure its temperature. Based on this feedback they perform a control action to adjust the hot and cold water valves until the process temperature stabilizes at the desired value. Sensing water temperature is analogous to taking a measurement of the process value or process variable (PV). The desired temperature is called the setpoint (SP). The input to the process (the water valve position) is called the manipulated variable (MV). The difference between the temperature measurement and the setpoint is the error (e), that quantifies whether the water is too hot or too cold and by how much. After measuring the temperature (PV), and then calculating the error, the controller decides when to change the tap position (MV) and by how much. When the controller first turns the valve on, they may turn the hot valve only slightly if warm water is desired, or they may open the valve all the way if very hot water is desired. This is an example of a simple proportional control. In the event that hot water does not arrive quickly, the controller may try to speedup the process by opening up the hot water valve moreandmore as time goes by. This is an example of an integral control. By using only the proportional and integral control methods, it is possible that in some systems the water temperature may oscillate between hot and cold, because the controller is adjusting the valves too quickly and overpensating or overshooting the set point. In the interest of achieving a gradual convergence at the desired temperature (SP), the controller may wish to dampthe anticipated future oscillations. So in order to pensate for this effect, the controller may elect to temper their adjustments. This can be thought of as a derivative control method. Making a change that is too large when the error is small is equivalent to a high gain controller and will lead to overshoot. If the controller were to repeatedly make changes that were too large and repeatedly overshoot the target, the output would oscillate around the setpoint in either a constant, growing, or decaying sinusoid. If the oscillations increase with time then the system is unstable, whereas if they decrease the system is stable. If the oscillations remain at a constant magnitude the system is marginally stable. A human would not do this because we are adaptive controllers, learning from the process history。第四節(jié) 本章小結(jié) 本章介紹了幾種控制器的的設(shè)計和調(diào)試，結(jié)合圖形對控制對象進(jìn)行控制。二、磁懸浮系統(tǒng)中的頻率響應(yīng) 由第一節(jié)內(nèi)容已經(jīng)得到，開環(huán)傳遞函數(shù)，即控制對象的傳遞函數(shù)為: ()即是 () 。前者稱為幅頻特性，后者稱為相頻特性。增加偶極子可以做到：（1）基本不改變原有根軌跡；（2）改變開環(huán)增益Ko，改善穩(wěn)態(tài)性能。 閉環(huán)階躍響應(yīng)曲線第二節(jié) 根軌跡控制器的設(shè)計