## 1 Introduction
In recent years, studies have shown that the steel bar bending machine is an important piece of equipment for steel bar processing, and a large number of scholars have studied its structure and control system; therefore, new products, new processes, and new technologies are constantly emerging. However, steel bar bending hoop processing belongs to processes of elastoplastic deformation and complex deformation at the same time [13; 14; 15]; the residual stress in the reinforcement during the processing will cause the hoop angle to spring back, thus affecting the product quality and accuracy. [PERSON] and others carried out bending hoop experiments at different angles on steel bars of different materials and specifications; by establishing a mathematical model, the experimental data were compared with the theoretical calculation results, and the experimental data were used to modify the theoretical calculation formula so that the theoretical calculation formula of the springback angle was more perfect [16]. [PERSON] and others used ABAQUS analysis software to simulate the coreless bending of an OCr18 Ni9 pipe and studied the influence of process parameters such as bending angle, bending speed, and wall thickness on the bending springback angle of the material [17]. [PERSON] and others used ANSYS/LS-DYNA finite element analysis software to analyze the influencing factors of steel bar bending and forming on the springback angle, finally analyzed the significance of the influencing factors of the springback angle by orthogonal experimental method, and modified the springback angle formula [18]. [PERSON] applied MARC finite element software to establish a bending model and analyzed the effects of bending hoop speed and bending axis rotation radius on the springback angle [19]. [PERSON] conducted a large number of bending and forming experiments on 1 Cr18 Ni9 Ti pipe, analyzed the factors affecting the bending springback of the pipe, and concluded that the springback angle increased with the increase in bending angle and relative bending radius [20]. [PERSON] used DynaForm simulation software to analyze the influence of yield strength on the resilience performance of V-shaped partsby taking HC550/980 DP, HC700/980 DP, and HC980 FG high-strength steels of different yield strengths as research objects [21]. [PERSON] and others used the three-point bending experimental device to conduct bending experiments on 1500 MPa ultra-high-strength martensitic steel and analyzed the effects of downward pressure speed, thickness, bending radius, and relative bending radius on the bending resilience of materials [22]. [PERSON] developed an online measurement technology for monitoring rotational tensile bending springback that uses a laser transmitter and receiving device to detect part displacement changes; because the laser measurement method does not need the workpiece to be removed from the tooling system, this method was created to improve product quality and productivity while improving the flexibility of the production route [23]. [PERSON] proposed a compensation mechanism based on the principle of implicit equation iteration, so that the final shape of the part converges to the target shape through iterative finite compensation [24]. [PERSON] and others provided a numerical approximation springback prediction and compensation method for SVC MT, compared the calculation accuracy of the three springback numerical approximation methods, and concluded that the Runge-Kutta method has the highest prediction accuracy [25]. [PERSON] and others used DynaForm software to perform springback simulation experiments on L-shaped parts and analyzed the thickness, edge pressing force, and corner radius of the concave and convex die by orthogonal test method [26]. The above study finds that the problem of bending springback is common in the material molding process, which seriously affects the accuracy and quality of finished parts, and springback control is a complex and urgent research topic.