# Analysis of a Novel Automatic Control Approach for the Free Forging Hammer
## 1 Introduction
[15] developed an energy model for the opening time of the blow valve and the blow energy, which provides a reference for the program control of the die forging hammer and achieves good performance in the open loop control of the die forging hammer. [PERSON] et al. [16] established a new model of the die forging hammer based on the elastic deformation of the cushion under the anvil and deduced a theoretical calculation formula of the maximum hammering force, which provided a reference for the design and use of the die forging hammer. Electrohydraulic forging hammers can be divided into free forging hammers and die forging hammers and configurations of die forging hammers have been optimized by the above methods. However, improvements of the free forging hammer have rarely been reported thus far. In addition to these methods, researchers have also focused on processing conditions and hammerhead compositions to improve the energy efficiency and processing performance of forging hammers. [PERSON] [17] studied the influence of friction on the forming effect of die forging hammers, and the results show that the upper mold achieves the best filling effect when the friction coefficient of the upper mold is about 0.2 and the friction coefficient of the lower mold is the maximum. [PERSON] et al. [18] employed the continuous damage mechanics theory to analyze the fatigue damage problem of the forging hammer foundation system and provided theoretical guidance for the engineering application of the forging hammer. [PERSON] and [PERSON] [19] studied the effect of the forging hammer composition on the deformation efficiency of lead workpieces and pointed out that a hammerhead filled with steel balls could improve the blow efficiency. [PERSON] and [PERSON] [20] proposed a failure detection method for the free forging hammer and pointed out that several ductile dimples would appear in the overload area, thereby resulting in fatigue cracks and hammer failure. The core aim of these methods is to improve the processing performance of the forging hammer by optimizing the composition and production environment through finite element analysis of the forging hammer equipment. Since the die forging hammer works intermittently and the workpieces are formed by molds in which the mold height and manufactured parts are all relatively fixed, the forming energy changes between different working cycles are regular. Therefore, it is easy to realize program control for the die forging hammer. By controlling the opening time and beat of the blow valve, the blow energy and blow step can be controlled as required. Furthermore, the machining accuracy and control performance are significantly improved based on a variety of optimization algorithms, and all forming actions of a die forging hammer are completed by control buttons and programs. Therefore, most of the new die forging hammers on the market nowadays are programmed die forging hammers. However, because of the large randomness of the process requirements in the production process of free forging hammers, the energy changes frequently between different steps, and the strike frequency is faster than the die forging hammer. Therefore, the control method applied to the die forging hammer cannot adapt to the working mode of the free forging hammer, and it is difficult for the free forging hammer to realize its automatic control by adjusting the opening time and beat of the blow valve. As can be seen from Figure 1, motions of a free forging hammer are still realized by manually operating a set of lever mechanisms in front of the forging hammer, of which the working principle are shown in Figure 2. The operator continuously manipulates the forging hammer for a long time (80 times/min), and another operator controls the forging manipulator on the operating car, leading to a high labor intensity, strong heat radiation, a high level of noise, and a low processing accuracy of a free forging hammer.