In mobile machinery, hydro-mechanical pumps are increasingly replaced by electronically controlled pumps to improve the automation level, but diversified control functions (e.g., power limitation and pressure cut-off) are integrated into the electronic controller only from the pump level, leading to the potential instability of the overall system. To solve this problem, a multi-mode electrohydraulic load sensing (MELS) control scheme is proposed especially considering the switching stability from the system level, which includes four working modes of flow control, load sensing, power limitation, and pressure control. Depending on the actual working requirements, the switching rules for the different modes and the switching direction (i.e., the modes can be switched bilaterally or unilaterally) are defined. The priority of different modes is also defined, from high to low: pressure control, power limitation, load sensing, and flow control. When multiple switching rules are satisfied at the same time, the system switches to the control mode with the highest priority. In addition, the switching stability between flow control and pressure control modes is analyzed, and the controller parameters that guarantee the switching stability are obtained. A comparative study is carried out based on a test rig with a 2-ton hydraulic excavator. The results show that the MELS controller can achieve the control functions of proper flow supplement, power limitation, and pressure cut-off, which has good stability performance when switching between different control modes. This research proposes the MELS control method that realizes the stability of multi-mode switching of the hydraulic system of mobile machinery under different working conditions.
In mobile machinery, hydro-mechanical pumps are increasingly replaced by electronically controlled pumps to improve the automation level, but diversified control functions (e.g., power limitation and pressure cut-off) are integrated into the electronic controller only from the pump level, leading to the potential instability of the overall system. To solve this problem, a multi-mode electrohydraulic load sensing (MELS) control scheme is proposed especially considering the switching stability from the system level, which includes four working modes of flow control, load sensing, power limitation, and pressure control. Depending on the actual working requirements, the switching rules for the different modes and the switching direction (i.e., the modes can be switched bilaterally or unilaterally) are defined. The priority of different modes is also defined, from high to low: pressure control, power limitation, load sensing, and flow control. When multiple switching rules are satisfied at the same time, the system switches to the control mode with the highest priority. In addition, the switching stability between flow control and pressure control modes is analyzed, and the controller parameters that guarantee the switching stability are obtained. A comparative study is carried out based on a test rig with a 2-ton hydraulic excavator. The results show that the MELS controller can achieve the control functions of proper flow supplement, power limitation, and pressure cut-off, which has good stability performance when switching between different control modes. This research proposes the MELS control method that realizes the stability of multi-mode switching of the hydraulic system of mobile machinery under different working conditions.
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