感盘读写系统的数学模型 磁盘读写系统的数学模型 前面确定了磁盘驱动系统的两个初始目标： 。精确定位读写头至期望轨道 @在50ms内由一条轨道移动到另一条轨道 首先确定控制对象G(s)和传感器的 数学模型。磁盘驱动器使用永磁直 Motor 流电机使得读写臂旋动。直流电机 使用所谓的音圈电动机。音圈电动 机是为适应计算机外围设备存储容 Arm 量增大的需要而发展起来的一种高 Flexure 精度直线定位用的新型执行元件。 读写头安装在滑动装置上，而滑动 Head 装置连接在读写臂上，如右图所示： 图3：读写臂结构 控制系统综合 自动控制膜理 电子信息学院5159 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 磁盘读写系统的数学模型 磁盘读写系统的数学模型 前面确定了磁盘驱动系统的两个初始目标： 1 精确定位读写头至期望轨道 2 在 50 ms 内由一条轨道移动到另一条轨道 首先确定控制对象 G(s) 和传感器的 数学模型。磁盘驱动器使用永磁直 流电机使得读写臂旋动。直流电机 使用所谓的音圈电动机。音圈电动 机是为适应计算机外围设备存储容 量增大的需要而发展起来的一种高 精度直线定位用的新型执行元件。 读写头安装在滑动装置上，而滑动 装置连接在读写臂上，如右图所示： Section 2.10 Sequential Design Example: Disk Drive Read System 117 2.10 SEQUENTIAL DESIGN EXAMPLE: DISK DRIVE READ SYSTEM ^ In Section 1.9, we developed an initial goal for the disk drive system: to position the reader head accurately at the desired track and to move from one track to another within 10 ms, if possible. We need to identify the plant, the sensor, and the controller. We will obtain a model of the plant G(s) and the sensor. The disk drive reader uses a permanent magnet DC motor to rotate the reader arm (see Figure 1.26). The DC motor is called a voice coil motor in the disk drive industry. The read head is mount￾ed on a slider device, which is connected to the arm as shown in Figure 2.71. A flex￾ure (spring metal) is used to enable the head to float above the disk at a gap of less than 100 nm. The thin-film head reads the magnetic flux and provides a signal to an amplifier. The error signal of Figure 2.72(a) is provided by reading the error from a prerecorded index track. Assuming an accurate read head, the sensor has a transfer function H(s) = 1, as shown in Figure 2.72(b). The model of the permanent magnet DC motor and a linear amplifier is shown in Figure 2.72(b). As a good approxima￾tion, we use the model of the armature-controlled DC motor as shown earlier in FIGURE 2.71 Head mount for reader, showing flexure. Motor Flexure Head FIGURE 2.72 Block diagram model of disk drive read system. Desired + ,- head i ^ position -~A -^ error J * , + P(r\ R(s) i f —. ~ w J * . Control device Amplifier Input voltage Actuator and read arm DC motor and arm Sensor Read head and index track on disk (a) Amplifier K* V(s) Sensor H(s) = 1 Actual >- i -i Motor and arm G(s) (7(- -I - " v " s(Js+b)(Ls+R) position (b) 图 3: 读写臂结构 控制系统综合 自动控制原理 电子信息学院 5 / 59