Control Model for Large‐Sized Gantry Type Linear Motor Slider

Abstract

At present, many industrial carrier devices utilize linear motor sliders. However, a heavier load requires a linear motor (which is an example of a direct drive device) to get higher power, compared with a rotary motor with a ball screw slider (which is an example of an indirect drive device). In order to obtain higher power at a lower cost, a linear slider with multiple motors can be utilized, for example, a gantry type linear motor slider. Moving the gantry type slider requires two linear motors that are set up in parallel to enable synchronization control. Some conventional synchronization control methods have been proposed for the parallel twin linear slider; however, a large-scaled gantry type linear motor slider has two unique problems: mechanical distortion caused by the limitations of installation environment and coupling caused by joints with low stiffness. This paper proposes a control model to solve these problems, and an identification method of each parameter. Furthermore, the effectiveness of the control model is verified by comparison with simulation results and experimental results. C⃝ 2018 Wiley Periodicals, Inc. Electr Eng Jpn, 203(2): 39-46, 2018; Published online in Wiley Online Library (wileyonlinelibrary.com).

Consideration of Multi-Degree of Freedom Vibration on Large-Sized Gantry Type Linear Motor Slider

“…This distortion generates a mutually repulsive force between the two axes because the reaction force on one axis is transmitted to the other axis through the top bar (joint table). A previous study derived a simulation model that reproduced this distortion and confirmed that the force between the two axes is repulsive [7]. A large repulsive force can cause the motor output forces to exceed their ratings.…”

“…For example, they are used for carrying thin steel plates in the steel industry [3] and, as for industrial machines, they are used in semiconductor manufacturing [2], in machining centers [4], and in devices producing large-sized liquid crystal panels [5,6]. Beneficial characteristics of linear motor sliders are quiet operation and cleanliness [7,8], which are both superior to the ball screw slider. Additionally, since the linear motor sliders are direct drive devices, they don't have couplings or elastic elements which the ball screw slider has.…”

“…However, to carry heavy loads, the linear motor slider is required to have a higher power. When aiming at higher power of a single linear motor, one has to design and manufacture a large-sized motor; in doing so, special design and individual manufacture are required because of permanent magnets for the field system and other issues, which inevitably add to costs [7,10,11]. Therefore, gantry type linear motor sliders, which are of lowcost and enable high output power, are used in such devices as large-sized liquid crystal panels producing equipment [5,6].…”

“…Hence, this research analyzes this vibration and states that it is important to consider multi-degree of freedom vibration, which means yawing vibration and pitching vibration of the large-sized gantry type linear motor slider. [7,14,15] The experimental equipment is comprised of two sliders arranged in parallel and linked by two attachments and a top bar (Fig. 1).…”

“…3 is implemented in "Approximation of distortion" in Fig. 2 [7]. The output value of "Approximation of distortion" is determined by x t1 .…”