Dynamics & control of High Speed High Precision LinearMotion SystemAbstract: This paper presents an improved robust control of a high speed high precision XY-table linear motion system used in semiconductor wire bonding machine. robust control is implemented in both inner velocity Hloop and outer position loop to achieve high and consistent control performance even in the presence of considerable resonance uncertainties and external disturbances. Auto-tuned feed-forward compensation based on fuzzy logic method is employed to obtain satisfactory dynamic and settling performance. High close loop bandwidth has been yielded, and high acceleration of 20g (1g = 9.81m/s 2), high speed of 0.9m/s can be achieved with the dynamic error of 2 m, settling error of 1.2m and static error of 0.2m.Keywords: Robust control; linear motion; XY-table positioning system; feed forward compensation; fuzzy logic;I. INTRODUCTIONWith the rapid development of semiconductor industry, microelectronics and bioengineering, mechanical systems such as machine tools, microelectronics manufacturing equipment, mechanical manipulators, and automatic inspection machines are intensively implemented with the requirements of robust, high speed, and high-accuracy positioning performance. Linear Permanent Magnet Synchronous Motors (LPMSM) has inherent advantages of direct drive, simple structure, high thrust density, high acceleration/deceleration capability and almost maintenance free 1,2. Therefore it is particularly suitable for linear motion system where high speed & high precision are required.In semiconductor wire-bonding machine application, high-speed operation is often required to yield high productivity, and the precision requirement becomes more and more stringent because less than 30 um bond pad pitch bonding capability is required in the industry. High-speed LPMSM direct-drive XY-table positioning mechanism is therefore implemented in the wire-bonding machine to achieve the required performances. In the XY-table positioning mechanism, Y-table is located on X-table and the bonding mechanical system that composes of bond head, optics, wire-clamps and cable bracket are mounted on the Y-table. The complicated mechanical design results in severe resonances, which vary with different operating conditions and from machine to machine due to manufacturing tolerance. The uncertain resonances cause difficulties in feedback control system design. It is difficult for traditionally designed proportionalintegralderivative (PID) controller, in combination with notch filters, to uniquely deal with a wide range of mass-produced machines with multi-varying resonance modes.Intensive studies on the control of high-speed high precision linear motion systems have been conducted in many literatures. A disturbance observer was developed in 3 and used for table positioning systems 4, 5. An adaptive robust position control design was proposed for linear motor drives 6. Composite nonlinear feedback control is proposed to achieve good tracking performance 7. These designs, which are based on the mathematical modeling of low-frequency plant dynamics, may not effectively take the mechanical resonance uncertainty into consideration. Robust control design including velocity/position dual control loop and feed-forward compensator is presented in 8. However, the acceleration of the XY-table is only 5g, the bandwidth is low and the high frequency resonances are not eliminated enough for close-loop frequency response, which will cause vibrations during settling.An improved robust control design is proposed for a high-speed high precision XY-table positioning mechanism. This improved robust Hcontrol design is employed in both velocity and position control loop to achieve high bandwidth that can reach 450Hz. Feed- forward compensation based on fuzzy logic control is implemented to obtain satisfactory dynamic and tracking performances. High acceleration of 20g is yielded with such design. Satisfactory performance has been achieved in the implementation of mass production.II. MECHANICAL STRUCTURE AND DYNAMIC MODELINGA. Mechanical StructureFig. 1 (a) shows the mechanical structure of the high-speed XY- table positioning mechanism mounted on a wire-bonding machine. Y table is mounted on top of the X table. A bonding mechanical system including a bonding head (BH) and its assembly accessories, such as bonding capillary, wire clamp and cable bracket are placed on the Y table. Each table is driven by a linear permanent magnet motor. The driving motors are composed of a base-mounted permanent magnet and one or two supporting carbon fiber brackets where the three-phase adjoining start-connection coils are embedded. The coil bracket shown in Fig. 1(b) is sandwiched between 2permanent magnet mounted bases with air-gaps and acts as the moving part of the motor. By feeding appropriate three-phase current to the coils, the interaction between the permane