# Analysis of a Novel Automatic Control Approach for the Free Forging Hammer
## 2 Methodology  
The above two forging hammers are controlled by manual operation of the slide valve. If a novel controller can be developed and used to substitute traditional manual control, then automatic control of the forging hammer can be realized. However, due to the randomness of the production process of the free forging hammer, the energy required between different working steps is different. Therefore, it is impossible to realize automatic control for the free forging hammer by the approach used in the current die forging hammer. In fact, motions of a free forging hammer are controlled by a main control valve, namely the manual slider valve. Therefore, automation of a free forging hammer can be achieved through automatic control of the main control valve. However, as the manual slide valve has a transition state and is infinitely variable, the valve opening size and the valve on-off state can be accurately controlled by a servo control system. In this control system, movement of the main control valve spool is controlled by a servo cylinder instead of a traditional manual drive, in which the servo cylinder is controlled by  
Figure 2: Schematic diagram of the all-hydraulic free forging hammer. (1: hammerhead; 2: relief valve; 3: working cylinder; 4: manual spool valve; 5: accumulator group; 6: hydraulic power unit). an electrohydraulic servo valve. Based on this method, the hammerhead motion state composed of stopping, slow rising, slow falling, returning, and striking with different frequencies and routes can be realized automatically. Figure 3 is a schematic diagram of the electro-hydraulic servo control system. As shown in Figure 3, the main control valve 1 is employed to control the motion state of the hammerhead. According to the opening size, the spool speed and the on-off state of the main control valve 1, hammerhead motions composed of fast falling, pressure with slow falling, pressure maintaining, fast returning, slow returning, and other actions can be accurately realized. To achieve an automatic free forging hammer, the movement of the valve 1 spool is driven by a servo valve 4 controlled single-action servo hydraulic cylinder. Compared with traditional manual control of slide valve 1, not only the control accuracy, but also the manipulating agreeableness are significantly improved. Displacement sensor 3 is employed to measure the position of servo cylinder 2, and the real-time measured data are uploaded onto the upper PC after processing. Then, the upper PC sends a control signal to servo valve 4 under the overall consideration of the current position data from sensor 3 and a required position signal for the following operation. In this servo control system, the response speed and the advance site of cylinder 2 completely follow the given command signal from the controller. Furthermore, the position signal of the hammerhead is also detected, and then fed back to the controller. By analyzing the differential value between the actual position and the reference position, a control signal employed to adjust the hammerhead trajectory is sent to servo valve 4 to change the motion state of servo cylinder 2 and main control valve 1, thereby realizing the automatic operation of the free forging hammer according to the set parameters. The relevant control algorithm will be discussed in the following section. Figure 4 presents a control diagram of the electro-hydraulic free forging hammer  
Figure 4: Control diagram of the electro-hydraulic free forging hammer. Figure 3: Schematic diagram of the electro-hydraulic servo control system. (1: main control valve; 2: servo hydraulic cylinder; 3: displacement sensor; 4: servo valve). The striking speed of the free forging hammer is up to 9 m/s, which produces a large impact and vibration on the forging hammer body and foundation.