| Iron roughneck is well known as an importantly automated auxiliary equipment in modem oil production, which can efficiently accomplish the making-up and breaking-out processes of drilling tools. In order to improve the automatic degree and the efficiency of the work and on the basis of reading the present situation of iron roughneck’s development, this paper aiming at some key problems such as the synchronization technology of hydraulic cylinder and the methods of automatically detecting the drill pipe center, redesigned the clamping cylinders of iron roughneck and improved it’s hydraulic system. And a further study of automatic centering has been to do.According to the operation process of the iron roughneck prototype, this paper analyzed the shortcomings of synchronization method and centering method using in the prototype. And a new synchronization scheme and schemes of automatically detecting the drill pipe center have been proposed, which have the advantages of high synchronization precision and high efficiency and greatly improving the iron roughneck automatic degree.According to the synchronization accuracy requirement of iron roughneck’s, the paper designed a new grip cylinder of electrical synchronization. The double cylinders of clamp pincers realized the electric synchronization by using stepping motor drive nut set of ball screw and clamped by hydraulic drive that meets large clamping force. And hydraulic circuit of the original prototype was improved.According to the actual working status of iron roughneck, it’s required that the center of clamping pliers and the center of the drill tool should be coincident, in order to avoid damaging the drill tool and the circular guide in clamping pliers. Combining the centering requirement of system of iron roughneck, the paper proposed a method of determining the center of the drill pipe by using high speed counter module based on photoelectric sensor and grating ruler. The method can determine the center and diameter of drill pipe, but can’t guarantee that the distance between the left clamping jaw of clamping cylinder and the center of the drill pipe is equal to the distance between the right clamping jaw of clamping cylinder and the center of the drill pipe. Then the paper proposed a method of determining the center of the drill pipe based on ultrasonic sensor, which used three ultrasonic sensors distributed on the same circumference. Experimental research shows that the method can determine the center of the drill pipe, but can’t determine the diameterof drill pipe. By analyzing the advantages and disadvantages of the two methods and synthesizing the two methods, the paper proposed a multi-sensor fusion method of determining the center of the drill pipe based on photoelectric sensor, ultrasonic sensor and grating ruler. The Experiment shows that the method can determine the position of the drill pipe center, determine the diameter of drill piper and ensure that the distance between the left clamping jaw of clamping cylinder and the center of the drill pipe is equal to the about equal to the distance between the right clamping jaw of clamping cylinder and the center of the drill pipe.According to the control requirements of the synchronization technology and automatic centering methods, the synchronization control system of iron roughneck’s grip cylinder and the detection control system of automatic centering has been designed which is based on the programmable logic controller (PLC). The design process of control system contains choosing the PLC, distributing the I/O ports, designing the external wiring diagram and preparing the control program. Last, the human-computer interface of the synchronization control system and automatic centering detection control system of iron roughneck has been designed.According to the hydraulic and control system of iron roughneck’s grip cylinder and the detection control system of automatic centering, some related experiments have been carried out. The experiment was divided into four parts:1) completed the experiment of clamping cylinder synchronization precision and evaluated the synchronization accuracy.2) proceed with the method of determining the center of the drill pipe based on the photoelectric sensor and the grating ruler, analyzed the reason of the error of the diameter measurement experiment and proposed the compensation method.3) proceed with the method of determining the center of the drill pipe based on ultrasonic sensors, calibrated ultrasonic sensor by experiments before the experiment, which provided the basis of programming.4) synthesizing the two methods, conducted the experiment of multi-sensor fusion method of determining the center of the drill pipe based on photoelectric sensor, ultrasonic sensor and grating ruler, the results of which indicated that the designed methods of the method can satisfy the requirements of precision requirement of automatic centering.
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