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Electromagnetic actuators that produce high linearity driving force are key components in active vibration isolation. In this paper, a design of high linearity electromagnetic actuator is proposed. Scheme of double closed magnetic circuits is used to ensure the linearity of magnetic flux density and rectangular structure is adopted to ensure the processing and assembly precision. The magnetic circuits of electromagnetic actuator are modeled using lumped parameter magnetic circuit modeling method, validated by simulation, and optimized to obtain improved performance. Experimental results show that magnetic flux density of 293.2mT and non-linearity of} 0.37% is achieved.

Linearity and resolution of current drivers are two factors that limit control accuracy and dynamic response accuracy of linear electromagnetic actuators in precision active and semi-active micro-vibration isolation systems. In this paper, a high linearity bidirectional current driver with resolution, AC ripple and stability in the order of $\mu$A is proposed. Complementary power MOSFET is used to produce bidirectional driver current and over-current protecting circuit is used to limit the amplitude of output current and prevent high output current from damaging power MOSFET and load resistance. Design of MOSFET heat dissipation is theoretically analyzed and experimental setup is established to validate performance of the proposed current driver. Experimental results show that resolution of 30$\mu$A, nonlinearity of 0.005%, stability of 150$\mu$ A /30min and AC ripple of 21$\mu$ A are achieved.

A spherical scattering electrical-field probe(SSEP) with noncontact, 3D isotropy and approximate point probing characteristics has been proposed for high-precision measurement of micro and small structures with large aspect ratio. Development of signal processing circuits for detection of weak cpacitantive signal on sub-picofarad level is the key to realize nanometer resolution. In this paper, a set of signal processing circuits based on operational capacitance measurement principle is proposed, and characteristics of the circuits are theorically analyzed and optimized. Experimental results indicates that resolution of 1 nm and nonlinearity of6 nm are achieved with the proposed signal processing circuits for a SSEP with $\phi$ 2.5 mm probing ball.

A low ripple switching power supply with 0-12 V voltage and 35 A maximum current outputs is developed for the application of high-precision thermoelectric circulating water cooling. In order to suppress the voltage ripple in the output caused by voltage and current spikes generated when the switching mode of full-bridge converter changes, which is further resulted from parasitic capacitance and inductance of MOSFET circuit and rectifier diode circuit in the power supply, resonance analysis and optimization design is carried out. Equivalent models of MOSFET circuit and rectifier diode circuit are established, and absorption circuits are designed to absorb the voltage and current spikes, thus to effectively suppress the voltage ripple in the output of the switching power supply. Experimental results show that the output voltage ripple is reduced from 190 mV to 88 mV after optimization of key parameter.

A circulating cooling water machine using agile bidirectional cooling and heating power control method is developed to produce circulating cooling water of high temperature stability and good dynamic performance. Cooling module based on thermoelectric cooling and multilayer compact structure is proposed to achieve cooling power output resolution at sub-watt level and quick response. Heating module based on a compact solenoid-in-tube structure is proposed to achieve heating power output with sub-watt level resolution and quick response. Experiments indicate that temperature stability of ± 3 mK, regulating resolution of 5 mK and regulating time of 128 s corresponding to 1 K step of circulating cooling water temperature are achieved with the developed machine. Thus, the developed machine can satisfy the challenging requirements of precision manufacturing.