中文摘要：

采用标准PD或PID控制器镇定双积分对象时，系统的阶跃响应必然存在超调；为此，设计了一种可以切换增益的非线性PD控制器，给出了系统阶跃响应无超调的充要条件，以及减小调节时间的方法．采用的切换规律是：当误差的幅值大于设定门限时，设计好的快速PD控制器投入工作，以加快误差的收敛；当误差的幅值小于设定门限时，设计好的强阻尼PD控制器投入工作，以抑制可能出现的超调．通过这两个控制器的配合作用，既能实现阶跃响应无超调，又能有效减小调节时间．仿真验证了该结论．

英文摘要：

If a standard PD or a PID controller is used to stabilize a double-integral system with step input, a nonovershooting step-response can＇t be obtained. A novel nonlinear PD controller with gain-switching is presented to deal with this problem. The necessary and sufficient condition of the nonovershooting step-response and the methods to reduce the settling time are given. The designed switching action obeys the following rule： when the amplitude of the tracking error is larger than a threshold value, a fast PD controller is employed to accelerate the convergence of the tracking error; otherwise, a strong-damping PD controller is adopted to restrain the overshoot. The cooperation of the two PD controllers reduces the settling time while rendering a nonovershooting step-response. These theoretical results are confirmed by computer simulations.