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Abstract: In a digital valve which uses a stepper motor under
continuous control as the electrical-to-mechanical interface, because of
the sinusoidal wave driving currents the input-output characteristics
demonstrate repetitive features, which is defined as stage control of
the digital valve. Due to the existence of saturation and hysteresis in
electromagnetic circuit of the stepper motor, the correspondent
nonlinearities are also involve in the input-output characteristics of
the digital valve. Sinusoidal curve is used to simulate the
electromagnetic nonlinearities and dominant equations are established to
describe the input-output characteristics of the digital valve. A
special experiment is designed to obtained the nonlinear parameters,
such as nonlinear error rate, hysteresis and resolution of the digital
valve under stage control. It is concluded from theoretical and
experimental results that the nonlinear error rate of the digital valve
is approximately proportional to the stage number used in the digital
valve and by increasing the number of stage control, the nonlinear error
rate can be effectively reduced and thus the accuracy improved in the
digital valve. In fact, the digital valve with multi-stage control is
applied in the electrohydraulic force servo control in material test
system (MTS).
Key words: Digital valve Nonlinearities stage control
Electrohydraulic servo
CLC No: TH137
国家自然科学基金(50475118)和浙江自然科学基金青年基金(R104506)资助项目.
Received 20041207, received in revised form 20050418
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