The mechanical transmission employed inside the computer numerical control (CNC) machine electromechanical system usually has an inherent backlash. As a position-controlled system is commonly used for the electromechanical system, the backlash limits the performance of the motion control system due to its nonlinearity and discontinuity. This paper proposes an effective method to adaptively detect and compensate for the backlash effect in real time, in which the end-effect load position of the CNC machine is estimated and controlled by the position-controlled servo system, in order to eliminate the influence of backlash on the contour path performance. The simulation results obtained from the model of a realistic CNC machine show the successful elimination of the error between the reference and the end-effector position and a significant improvement in the control system performance.

A unidirectional and unipolar stepper motor driver has been designed, for the purpose of effectively solving many existed pressing problems in the stepper motor such as high costs, poor universality, complex circuitry, and inconvenient manipulation and so forth. The unidirectional and unipolar stepper motor will become outstanding as the result of its low costs, stable performance, suitable for computer control and could be driven by unipolar stepper motor. The circuit employs CD4017 to distribute pulse, and applies 74LS02 TTL to converse the single-pass four circulations into dual-pass four circulations, and utilizes the integrated Darlington pairs (Darlington transistors) to amplify the power, and then activates the stepper motor by the amplified power. It has been verified in the experiment that the circuit operates stably and pertains high control accuracy.