A Practical Precision Control Method Base on Linear Extended State Observer and Friction Feedforward of Permanent Magnet Linear Synchronous Motor

Abstract

In this paper, a detailed model of motion stage driven by iron-less permanent magnet linear synchronous motor (PMLSM) and supported by rolling guides are presented. This stage is a prototype of the feeding system for a precise turning machine tool. In this model, there are two categories disturbances including slow-varying ones mainly produced by the thrust ripple of PMLSM and abrupt-changing ones caused by nonlinear friction of rolling guide. To overcome these disturbances, a simple, effective and practical servo control method based on the general-purpose two-degree-of-freedom PID (2DoF-PID) type controller integrated with the linear extended state observer (LESO) and the friction feedforward (FFF) controller is presented. In this control framework, the linear ESO is designed to estimate and compensate for the slow-varying disturbance and the FFF controller is adopted to eliminate the abrupt-changing nonlinear friction effects. Finally, comparative simulations indicate that the 2DoF-PID-LESO-FFF is effective and achieves better performance compared with traditional controllers, and experiment results demonstrate that the tracking error of the proposed method can be kept in the bounds of 1.5 µm under different conditions.INDEX TERMS Iron-less PMLSM, thrust ripple, nonlinear friction, linear extended state observer (LESO), friction feedforward (FFF).

A Contraction Theory-Based Tracking Control Design With Friction Identification and Compensation

“…2. We selected this relative high gain θ to precisely estimate the state x of the servomechanism model (16). Through this gain θ, the ILESO has a bandwidth of θ/2π = 159 Hz allowing to capture fast characteristics of the servo friction F ; thus, the ILESO estimate F = − x 3 /a closely matches F .…”

“…The friction can also be estimated using disturbance observers, such as the High-Gain Observer (HGO) [9], Sliding Mode Observer (SMO) [10], Nonlinear Disturbance Observer (NDO) [11], and Extended State Observer (ESO) [12]- [16]. In particular, the ESO has received keen attention because it simultaneously estimates the system's states and uncertainty without requiring an exact system model.…”

“…An advantage of this strategy is that the FILESO only has to deal with a small system uncertainty, thus avoiding the use of a large observer gain. Moreover, in comparison with the LESOs in references [12]- [16], that directly employ the servo position measurements, the ILESO and FILESO designs considered in this paper estimate the servo states using the integral of the position measurements, which permits attenuating the effect of quantization or highfrequency noise. In addition, a tracking controller based on the backstepping method is designed, which uses the estimated off-line friction model, on-line estimation of the servo states, and remaining uncertainty from the FILESO to achieve a precise reference tracking.…”

Design and Position Control of Overhang-Type Rail Mover Using Dual BLAC Motor

“…In a more advanced rail system, applications of a linear motor [13][14][15] and magnetic levitation [16,17] can be found. As is well-known, a linear motor can guarantee high con-trol performance with accurate position information; however, the moving rail has to contain permanent magnets or winding cores as a part of linear machines.…”

Motion control of the rail traction system by dual brushless AC motors using a disturbance observer

“…However, the full-order observer involves many system parameters and its adoption is very complex to be used in dual traction systems. Linearextended and sliding-mode observers can be adopted to compensate the non-linear friction, but it requires a complex gain matrix and an electro-mechanical parameter set [14,15]. In these studies, the speed and position accuracy due to feedback delay are not considered.…”