航模舵机的动态特性测试与系统辨识

航模飞机受机体质量、机体空间和设计成本的限制，选用的小型航模舵机大多缺乏相应的频响特性指标，须在使用前完成频响特性测试。考虑舵面惯性载荷和气动载荷对舵机特性的影响，设计了舵机频响特性测试平台，可对大部分航模舵机和小型伺服电机进行空载或带载测试。针对常用的三款舵机进行频响特性测试，并采用子空间辨识获得舵机准确的数学模型。通过三款舵机频响特性对比得出，即使舵机的标称扭矩满足使用要求，负载增加也会改变舵机的幅频特性；舵机中存在的时滞时长随负载变化。而航模舵机常用的50 Hz PWM信号，也限制了舵机的带宽。 

Dynamic property test and system identification of model aircraft actuators

Small actuators are chosen due to the limitation of model aircraft's weight, space and design cost, most of which are lack of frequency response characteristics that need to be tested. Considering the influence of inertial loads and aerodynamic loads of rudder, an platform for testing frequency response characteristics of actuator was designed and capable to perform tests with or without loads on rudder. Frequency response characteristics test was conducted for three types of frequently-used actuators. Subspace identification method is used to obtain precise mathematical model of actuator. The comparison among frequency response characteristics of three actuators indicated that even if the nominal torque of the actuator meets the requirements of use, the amplitude-frequency characteristics change with the increase of loads. The time delay in the actuator also varies with the load. Widely used 50 Hz PWM signal limits the bandwidth of the actuator.