The research and future prospects of the arc sensorWeld seam tracking is to ensure that the premise of quality and welding automation, and sensors are the basis for achieving this prerequisite. Welding sensor according to the different ways of sensing additional sensors can be divided into two major categories and arc sensors. Most of the traditional seam tracking is an additional type of sensor, for example, touch sensors, electromagnetic sensors and a variety of optical sensors, such sensors is the sensor and the common problems is the separation of the arc, the sensor detection point arc with a certain distance away , a large arc in the welding seam will affect tracking performance. The arc sensor using the arc welding process, the current waveform or the change of arc voltage waveforms obtained ARC Centre has deviated from the seam as the sensor information and real time, tracking well. Arc sensor is its biggest advantage of the anti-arc, high temperature and strong magnetic fields are strong, and it is always consistent with the overall arc, simple structure, low cost, at present, arc welding sensor as a means of sensors much national attention, many foreign welding equipment research and manufacturing organizations are working to develop this area. Early start of the study of industrial countries, have developed a variety of arc scan forms (such as double wire tie, swing and rotation) of the arc sensor, suitable for submerged arc welding, TIG and MIG / MAG welding methods, such as different, and some have been used in welding production. Many countries on the production of arc welding robot equipped with swing arc sensor tracking device. 1 Classification of arc sensor 1.1 Swing scanning arc sensor Swing arc scanning is currently the most widely used sensor of a welding arc sensor, which needs a swing arc sensor device, in the horizontal direction of the weld seam tracking back and forth and achieve. Used in arc welding robot sensors do not need to swing on a swing device, driven by the robot arm for horizontal swing to torch. However, the impact of structural factors by robots, robot beat frequency of 10Hz is generally less as shown in Figure 1a. In the high-speed arc welding and weld large cases, the tracking performance will be affected. M KODAMA invented an electromagnetic high-speed swing arc sensor, the sensor on both sides of this arc has a permanent magnet and exciting coil, when the excitation coil of the DC current through a certain frequency, the conductive rod swing will produce a certain frequency to achieve seam tracking. This high-speed swing arc sensor generally can beat frequency adjustable between 0 40Hz, 0 4mm adjustable swing, the maximum welding speed 400mm / sec. It features small size, less weight 1Kg, the structure shown in Figure 1b. 1.2 Double wire parallel arc sensor The arc sensor using two separate parallel arc welding on the workpiece, the welding wire around the two current (voltage) difference between the provision of two electric arc welding has deviated from the centerline of information, thus can be realized seam tracking. According to the two arc parameters and compare the difference between the reference value can also be achieved between the tip and the surface distance adjustment. This sensing method is the use of arc static characteristic parameters change as the sensor signal, use the same two parameters were independent loop power parallel groove welding, torch structure more complex, there are certain difficulties in implementation, so the utility on restricted. 1.3 high-speed rotating arc sensor scan The arc sensor to rotate the arc instead of the swing arc, the rotation frequency up to 100Hz. Twentieth century, the eighties, NKK Corporation of Japan has invented a rotating arc sensor, and applied to the narrow gap weld, the principle shown in Figure 2: conductive rod as the cone of the bus, around the cone axis of rotation (revolution) , and not conducting rod around its axis of rotation (rotation), and the magnitude of cone movement at the top of a small diameter of this structure is to adjust the scanning cone angle adjustment, the sensor need to use a gear drive, the structure large, affecting the accessibility of welding torch. NKK Corporation of this technology in ships, boilers and structure to be applied in production, and achieved remarkable results. CH Kim Korea produced a high-speed rotating arc sensor, shown in Figure 3, the sensor tip depend on the eccentricity to achieve the arc of the rotating tip of the eccentricity is the arc radius. Although its rotating body is relatively simple, compact, but its high-speed rotation, the wire tip must be in the same rotational speed, which exacerbated the tip of the loss. Germany U. Dilthey also done a lot of high speed rotating arc sensor research, production and made the arc seam tracking sensors. In China, starting from the late eighties, to Tsinghua University, Academy o