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Dual-frequency laser interferometer has been widely used in precision motion system as a displacement sensor, to achieve nanoscale positioning or synchronization accuracy. In a multi-channel laser interferometer synchronous measurement system, signal delays are different in the different channels, which will cause asynchronous measurement, and then lead to measurement error, synchronous measurement error (SME). Based on signal delay analysis of the measurement system, this paper presents a multi-channel SME framework for synchronous measurement, and establishes the model between SME and motion velocity. Further, a real-time compensation method for SME is proposed. This method has been verified in a self-developed laser interferometer signal processing board (SPB). The experiment result showed that, using this compensation method, at a motion velocity 0.89 m s−1, the max SME between two measuring channels in the SPB is 1.1 nm. This method is more easily implemented and applied to engineering than the method of directly testing smaller signal delay.

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Employing the attached magnetic fields of permanent magnet synchronous planar motors for position sensing has been widely investigated, as it is low-cost and requires no complex setup compared to optical ways. An optimized position sensing method requiring only simple calculations to achieve precision planar 3-degree-of-freedom (DOF) position is proposed in this paper. By adding sensors and new decoupling operation, this optimized method complements the unmeasured position areas in the previous work, guaranteeing the ability to measure position in whole motion region. Simulation results verify the 3-DOF position sensing ability for global motion region and show that translational accuracy is 10 μm-order and rotational accuracy is 0.1°-order under a conventional noise level. To demonstrate the feasibility, experiments have been conducted on a self-developed platform. Compared to commercial position devices, the results illustrate that the optimized method is able to measure planar 3-DOF position while its accuracy is limited by the imperfections of the magnetic field. X mean and standard deviation of −16.2 μm and 18.7 μm, and Y error mean and standard deviation of −11.3 μm and 16.4 μm are achieved in small-range comparison measurements.