Permanent magnet synchronous motor (PMSM) has been widely employed in the continuous-wave pulse generator and exhibits advanced performance. However, its applications are constrained to some extent, because of the alternating load shocks and measurement resolution, etc. To cope with these issues, a double degree-of-freedom (DOF) control strategy that combines the extended Kalman filter (EKF) and adaptive linear active disturbance rejection control (LADRC) is proposed to realize fast dynamic response and strong anti-interference capability. The EKF is established according to the PMSM motion model to filter measurement noise and generate external disturbance estimations in a timely manner and reduce the observed burden of adaptive LADRC. The LADRC characteristics are analyzed to highlight conflicts between dynamic response and noise suppression under different observer and system bandwidths. Then, adaptive bandwidth laws are constructed. Finally, the simulation and experimental results are achieved to verify the effectiveness of the proposed strategy for the PMSM control system. It is believed that the striking advantages of such a method render it very suitable and powerful for the speed control of a continuous-wave pulse generator.

A simple differential capacitive sensor is provided in this paper to measure the absolute positions of length measuring systems. By utilizing a shield window inside the differential capacitor, the measurement range and linearity range of the sensor can reach several millimeters. What is more interesting is that this differential capacitive sensor is only sensitive to one translational degree of freedom (DOF) movement, and immune to the vibration along the other two translational DOFs. In the experiment, we used a novel circuit based on an AC capacitance bridge to directly measure the differential capacitance value. The experimental result shows that this differential capacitive sensor has a sensitivity of 2 × 10⁻⁴ pF/μm with 0.08 μm resolution. The measurement range of this differential capacitive sensor is 6 mm, and the linearity error are less than 0.01% over the whole absolute position measurement range.

The quality of pressure signals is intricately linked to the speed variation characteristics of the permanent magnet synchronous motor (PMSM) employed to drive the rotor of the continuous wave pulse generator. However, achieving precise control of PMSM is significantly challenged by complex and time-varying drilling operating conditions. A serial n ADRC (S n ADRC) is presented to increase the control motor's immunity and dynamic performance, where “ n ” indicates the number of sequential output stacking extended state observers (SOS-ESOs) equal to the highest order of the disturbance. Based on the deduced continuous wave pulse generator rotor model, first-order SOS-ESO is intended to detect the first-order disturbance, with the higher order SOS-ESO designed to anticipate the residual disturbances in order to accomplish real-time and precise hydraulic torque prediction. Moreover, the estimation performance of SOS-ESO is analyzed, and the intrinsic stability of S n ADRC with the speed loop control system is rigorously demonstrated using the Lyapunov theory. Additionally, SOS-ESO is employed in simulation to resist polynomial disturbances, and it is discovered that the n thorder SOS-ESO may successfully suppress complex disturbances up to ( n -1) order. Finally, the control performance of S n ADRC is compared to that of classical control methods in both the simulation and experiment, and the results show that S n ADRC has excellent rapidity and stability in motor control, which opens up a wide range of possibilities for practical applications in control and engineering fields.

The joule balance, which relates the mechanical energy and the electrical energy, was proposed by National Institute of Metrology (NIM) to measure the Planck constant and realize the kilogram with the Planck constant based on the new definition of the kilogram. In 2019, the NIM-2 joule balance participated in the first key comparison of kilogram realizations (CCM.M-K8.2019) with a combined relative standard uncertainty of 4.5×10 ^-8 . After the first key comparison, a series of improvements on the mechanical, electrical, and the alignment systems have been carried out. To improve the accuracy of the electrical measurement, the periodical calibration of the digital voltmeter (DVM) with the Programmable Josephson Voltage System (PJVS) was also realized. The calibration period of the DVM was reduced from 5 days to 3.5 hours. With these improvements, the corresponding uncertainties were decreased significantly.

This paper describes an absolute method for calibrating commercial 1000:1 dc current transducers (DCCTs). By adding two auxiliary windings to produce 10:1 and 100:1 ratios, we use a three-step build-up method to establish the 1000:1 current ratio standard. First, we determine the 10:1 ratios of 11 DCCTs through permutation; second, we set up a two-stage composite DCCT to produce a 100:1 ratio; after switching auxiliary windings in the two-stage setup, we then derive the 1000:1 current ratio. The experimental results show that the requirements for the current source and the current meter are not stringent; their Type-B contributions to the overall uncertainties are very small. Type-A uncertainties which include factors such as the experimental environment and possible drifts of the output offsets of the DCCTs are experimentally determined. Repeated tests show that the current ratio standard has an expanded uncertainty of 0.26 x 10⁻⁶ for the 1000:1 ratio.

If a used “vertical beam” is not perfectly vertical in a measurement, a cosine error will be introduced into it. To decrease and compensate for this cosine error, a measurement system is proposed to measure the deviation of the laser beam from the vertical direction. The structure of our measurement system is illustrated, and a model for solving for the deviation angle is established. As the distance of the beam spots on the charge-coupled device is the essential parameter for the measurement results, the acquisition process for this distance is explained. Moreover, the accuracy of the algorithm used in the acquisition process is also tested by experiments. Further, a self-correction module is designed and applied to reduce the error caused by the corner cube reflector in the system. The characteristics of the measurement system such as the resolution, stability, temperature drift, and direction accuracy are analyzed through experiments. The combined uncertainty of the measurement system is calculated to be $11\times {10}^{-6}\mathrm{rad}$.