行程偏差 meaning in English

deviation of stroke

The main function of a governor is to monitor the speed deviation of a hydro turbine unit and convert it into the displacement deviation of the servomotor according to a specific characterisic . it is used to control the opening of the guide apparatus and to ensure the unit run steadily at fixed speed under a given load
调速器的主要功用是检测机组转速偏差，并将它按一定特性转换成接力器的行程偏差，借以调整机组导水结构的开度，使机组在给定的负荷下以给定的转速稳定运行。