An optimal servo system based on sliding mode for the contact force of an active pantograph

Abstract

This paper presents a design method of optimal servo systems based on sliding mode for an active pantograph with flexibility subject to the stiffness variation of the catenary. It is pointed out through our analysis that the flexibility makes the control problem much harder, because it increases not only the freedom of motion but also the relative degree between the control input and the contact force to be controlled. However, it is shown by employing the optimal control theory, especially SRL (Symmetric Root Locus), together with sliding mode theory that pole-zero cancellations play an important role in the controller design. Some numerical simulations in a practical situation, where the actuator dynamics and sensor noise are taken into account, show the effectiveness of the proposed design method.

Robust control of pantograph‐catenary system: Comparison of 1‐DOF‐based and 2‐DOF‐based control systems

“…It is shown that a lumped model with possibly time‐varying parameters is sufficient in describing the motion of the pantograph in the vicinity of the working configuration [33, 34]. By taking into account the frame flexibility, the dynamics of the active pantograph is modeled with 3‐DOF [9], where a pneumatic cylinder works as the actuator. The main spring is originally for a passive pantograph and not used for active control.…”

“…To test the developed method in realistic environment, consider the dynamics of the pneumatic actuator and measurement noise in the simulation. The dynamics of the pneumatic actuator [9] is Band‐limited white noise with the amplitude and sampling time is added into the system output, namely, the contact force. The simulation result is shown in Figure 12.…”

“…Some guidelines on how to select A e and C e are given. As analyzed in Section 3, the eigenvalues of A e are inferred by the FIGURE 7 Mechanism of active pantograph [9,32] frequency characteristics of uncertainties or disturbances. As for C e , it should be chosen to avoid unnecessary hidden modes in the general EID estimator and to guarantee that the closed-loop control system (31) may be internally stabilized.…”

“…A PID controller was applied to the pantograph‐catenary system [8], where an intelligent algorithm was needed to determine the control parameters. Though a sliding‐mode control method was used to suppress satisfactorily the contact force fluctuation [9], the catenary displacement was a bit large.…”

“…In this paper, the active pantograph is from the Railway Technical Research Institute of Japan[32]. The pantograph parameters were obtained from identification experiments conducted by the joint research of the Railway Technical Research Institute of Japan and the Niigata University of Japan[9].…”