Tracking errors occur during the position tracking because the three degrees of freedom (d. o. f.) hydraulic servo joint is a nonlinear dynamic system with saturation, dead band and stroke coupling.

• 摘要三自由度液压伺服关节在实现位置跟踪时存在跟踪误差，原因在于液压伺服关节是一个具有饱和、结构死区和强耦合的动力学系统。