Research on Key Technologies of Precise Measurement of Geographic Coordinates of Subsea Pipelines

With the continuous increase of offshore oil and gas exploitation activities, the number of subsea pipelines is becoming larger and larger, which leads to frequent occurrence of subsea pipeline accidents. Long-term safe operation of subsea pipelines can be ensured by regular defect detection. The premise of locating and disposing defects is to accurately measure the geographic coordinates of subsea pipelines. Our research group has put forward a kind of pipeline spherical internal detector (SD), which has the advantages of convenient implementation, low risk to jam. For the SD, this paper has carried out research on the key technology of precise measurement of subsea pipelines’ geographic coordinates using the internal magnetic fields. The main work is as follows: (1) Magnetic tensor invariant calibration method for magnetometer array has been studied and L-M algorithm is taken to solve the parameters, which is efficient and accurate. Field calibration experiment has proved this method is effective and has good robustness. (2) A new method of measuring pipeline’s pitch angle is proposed. Under the experimental condition of using AC servo motor to drive the sensor instead of the SD to rotate, the pitch angle measurement error is less than 0.2°. (3) Magnetic anomaly of spiral weld and buckling pipeline are used as new mark points to calibrate the geographic coordinates of subsea pipelines. Experimental results show that the newly designed SD can successfully identify spiral welds and buckling pipeline.

FPGA-Based Implementation of Torque Controller for 6-DOF Articulated Robots

This paper aims to design an impedance position-based proportional-integral-derivative (PID) controller based on forward and inverse kinematics of HIWIN RA605 articulated robot, and Field-Programmable Gate Array (FPGA) implementation for a PID torque controller. In order to control the robot, the FPGA needs to output commands to communicate with the AC servo motor drivers. An FPGA-based controller for a 6-degree-of-freedom (DOF) articulated robot that implements several tasks such as hardware implementation, encoder counters, noise cancellation algorithm, analog generators, PID controller, and communication are included, the processing time of the FPGA is 16 μs. Meanwhile, the whole process of the system only takes 82 μs to complete.

A Review on The AC Servo Motor Control Systems

AC Servomotors are widely used in the industries for the control of static and dynamic loads. Precise control of position, speed, and torque are the main issues with the AC Servomotor. AC Servomotors are highly demanded by the industries to have a precise response under dynamic load conditions. Many control techniques are commercially available for the control of AC Servomotor under static and dynamic load conditions. However, all of these control techniques have advantages and limitations. Many investigations are done on the control of AC Servomotor, but comprehensive surveys on the control of AC Servomotor were still limited. In this paper, most of such commercially available control techniques are investigated, discussed, and compared.

Improved Internal Model Control Technique for Position Control of AC Servo Motors

This paper focuses on the simulation analysis of the conventional Internal Model Control (IMC) technique and the development of two proposed control techniques for the position control of AC Servo Motor. Internal Model Control (IMC) technique [1] was only able to control the AC Servo Motor under static load condition. Also, it had step response problems, and it was not robust against external disturbances. For these reasons, the IMC technique was further improved to control the AC Servo Motor under dynamic load conditions by proposing Amended Internal Model Controller (AIMC). The step response and the robustness of AIMC against external disturbances were further improved by proposing AIMC+FLC. Where a Fuzzy Logic Controller (FLC) is designed and connected with the AIMC.

Microtension control for a yarn winding system with an IMC PID controller

In this paper, feedforward compensation and an internal model control (IMC) PID tuning method to maintain the yarn tension within a micro-boundary range are proposed. The proposed method can be used to improve the quality of products in textile industry. We first develop a mathematical model of the AC servo motor and yarn tension system. Based on the results of the mathematical model, an IMC PID controller is designed to control the microtension of the yarn. The proposed IMC-PID controller can be directly calculated from the time constant and time delay. Feedforward control is used to compensate for the linear velocity of the winding roller. To reduce the lateral vibrations of the yarn, we designed an active roller to nip the moving yarn. The active roller compensates for the variation in the diameter of the unwinding roller. The proposed method effectively improves the dynamics performance and the robustness of the system, and is appropriate for industrial application. Experimental instruments, including a tension sensor, an AC servo motor and a motion controller, equipped with a computer, are used to test the proposed method. The simulation and experimental results show the effectiveness of the proposed controller for the yarn microtension control system.