Dichen Li

A motor-piezo actuator for nano-scale positioning based on dual servo loop and nonlinearity compensation

This paper presents the design of an ultra precision positioning system, which consists of a coarse stage and a fine stage. Two servo motors moving on recirculating ball screw are used to drive the coarse stage and three piezo actuators are used to provide the nanoscale positioning. The static and dynamic performances of the positioning system are formulated for designing the micro stage. Based on an evaluation of the systems natural frequency, a dual sever loop approach is used as the control mechanism. The main noise caused by the ambient environment is reduced by a vibration-suppressing table, and in the system control software, a digital Chebyshev filter is used to remove the noise caused by the magnetic chuck on the table. To correct the hysteresis and nonlinearity of PZT, Exact Model Matching (EMM) control law has been used, and therefore repeatability of the fine stages motion can be improved considerably, the positive and negative movement can follow exactly the same path. A positioning accuracy of 8 nm is achieved over a traveling range of 200 mm with this system.

A low cost cutter-based paper lamination rapid prototyping system

Paper lamination rapid prototyping technology has an advantage of its low overall cost due to the building materials and the processing principle. To reduce the system and its operating cost further, a cutter-based paper lamination rapid prototyping system is proposed. The cutter set employed is cheap and the cutter can turn its cutting direction automatically so as to simplify the system control. In this paper, the cutting mechanism of the cutter was studied. According to its kinetic characteristics, the motion of the cutter nose was described by a tractrix model, and its trace error can be eliminated by modifying the cutter path. Experimental study on the cutting notch was carried out, and the notch specimens were measured through a high-power microscope VH-8000. According to the analysis of the experimental results, the dimension error caused by the cutting notch was within 3 μm and the roughness average (Ra) was less than 6 μm. Two physical parts have been fabricated on the developed experimental machine, which indicates the proposed system has use value.

Fabrication and mechanical properties of UV-curable glass fiber-reinforced polymer—matrix composite

A UV-curable glass fiber-reinforced composites was investigated in order to develop a cost-effective fabrication approach for manufacturing polymer—matrix composites. The effects of glass fiber-treating process and UV exposure power on the tensile strength were studied through scanning electron microscopy, contact angle determination, and curing degree test. The experimental results showed 11.5% increase in tensile strength for the UV-cured composite reinforced with heat-treated glass fiber, and 51.4% increase with glass fiber treated by coupling agent. The optimal exposure power was 0.94 J/mm2 to obtain the optimized mechanical properties. However, overexposure could seriously result in the loss of tensile strength. The maximum tensile strength and shear strength of composite cured by UV approach in this study were 902.09 and 25.04 MPa, respectively.A UV-curable glass fiber-reinforced composites was investigated in order to develop a cost-effective fabrication approach for manufacturing polymer—matrix composites. The effects of glass fiber-treating process and UV exposure power on the tensile strength were studied through scanning electron microscopy, contact angle determination, and curing degree test. The experimental results showed 11.5% increase in tensile strength for the UV-cured composite reinforced with heat-treated glass fiber, and 51.4% increase with glass fiber treated by coupling agent. The optimal exposure power was 0.94 J/mm2 to obtain the optimized mechanical properties. However, overexposure could seriously result in the loss of tensile strength. The maximum tensile strength and shear strength of composite cured by UV approach in this study were 902.09 and 25.04 MPa, respectively.