1、Design and analysis of a novel X-Y tableJ.F. Pan1, N.C. Cheung2, Guangzhong Cao1, Hong Qiu1AbstractA novel X-Y table based on linear switched reluctance principle is proposed in this paper. The proposed direct-drive actuator has the characteristics of low cost, simple mechanical structure and high r
2、eliability. Finite element analysis (FEA) proves that the phases between any of the linear motors of the X-Y table are decoupled and each phase can be controlled independently. Experimental results verify that the motion control system based on the X-Y table has good dynamic characteristics.Keywords
3、-switched reluctance, direct-drive, FEAI. IntroductionIn most advanced manufacturing processes, two-dimensional motions are in high demand for industrial applications such as parts assembly, component insertion, machining, etc. A traditional X-Y table often utilizes a rotary motor and couples its ou
4、tput shaft to mechanical translators such as gears or bears to perform linear motion; by vertical arrangement of two such linear motion implementations, two-dimensional movement is achieved. In a direct-drive system, the mechanical output is directly generated to the actuator and load and it has the
5、 characteristics of high force density, high precision and low production cost 1. By elimination of mechanical transmissions, such as rotary-to-linear couplers, the control object, together with the actuator can be implemented as an integral system, which is capable of fast response, high flexibilit
6、y and can have a simple structure. The X-Y table based on direct-drive idea can be constructed according to different motor methodologies such as a pair of linear direct current motors (LDCM), linear induction motors (LIM), linear permanent magnetic motors (LPMM) or linear switched reluctance motors
7、 (LSRM), etc. Due to the presence of a commutator, the LDCM requires frequent adjustment and maintenance. The principle of the LIM is similar to a common rotary induction motor with a robust structure. Though linear motion of high speed or high-precision is difficult to achieve due to the low air ga
8、p flux density 2, a variety of applications can still be found for a long-stroke motion such as the magnetic levitation train for railway transportation 3. The LPMM is the only type of linear actuator available to industry by present and it has the advantages of wide range of speed regulation capabi
9、lity and stable output performance. One structural disadvantage of such linear motor is the utilization of expensive rare-earth permanent magnets to achieve better performance and efficiency. Due to the characteristics of the permanent magnets, a LPMM is not suitable under hostile environment that h
10、as a various temperature change. Moreover the overall cost of the linear motion system is high. II. Design and construction of the X-Y tableWith fast advancement of power electronics technology, research on switched reluctance motors becomes more and more extensive. A typical SR machine has the foll
11、owing characteristics, The mechanical structure is simple and robust with doubly-salient stator. The motor can operate under various hostile environments with large temperature difference since no permanent magnets or commutator involved. Since the winding is fixed only on the stator, the motor is e
12、asy for cooling and has low heat loss thus it has high efficiency. Project 200734 supported by SZU R/D Fund The paper first received 15 Dec 2008 and in revised form 5 Jan 2009. Digital ref: 1231College of Mechatronics and Control Engineering, Shenzhen University, Shenzhen, P.R.China, E-mail:gzcao2De
13、partment of EE, The Hong Kong Polytechnic University, Hong Kong, E-mail: norbert.cheungpolyu.edu.hk Torque generation is irrelevant of current directions. Therefore the drive topology can be minimized to reduce system cost. According to the winding arrangement, a LSRM can be categorized as “active-s
14、tator-passive-translator” and “passive-stator-active-translator” structure 4. The motion system applies the “passive-stator-active-translator” scheme for the following reasons, Simple manufacture of the stator base with no complicated coil arrays Flexible traveling range and stator dimensions Easy m
15、anufacture of mover slots with mounted coil windings Low overall production costBased on the idea of “passive stator-active translator” structure, the linear motor is constructed as shown in Fig.1. The motor is composed of the moving platform and the stator base. The stator base is made of aluminum
16、alloy to minimize the mass and facilitate the magnetic flux path. A pair of high-grade linear guides is fixed on the stator base to facilitate the movement of the moving platform. The stator utilizes 0.5mm thick silicon-steel plates with tooth structure instead of any expensive materials such as rare-earth permanent magnets. A pair of aluminum locking bars is fixed on the stator base slot to hold the pl
