Abstract
To reduce the energy consumption and emissions of the hydraulic excavator, a two-level idle speed control system with a hydraulic accumulator for the construction machinery is proposed to reduce the energy consumption and improve the control performance of the actuator when the idle mode is cancelled. The structure and working principle are analyzed. The hydraulic accumulator (HA) is used to store the energy, which can provide backup pressured fluid when the idle mode is cancelled. Then, a method of how to set the pressure differential between the hydraulic accumulator and the load is proposed and the control law is discussed. The test rig is built. The experimental result shows that the idle speed can be switched among the first idle speed, the second idle speed and the normal speed automatically. Though the idle speed in the novel system can be reduced more than that in the conventional automatic idle speed control system (AISCS), the proposed system can still build the actuator pressure more quickly when the idle mode is cancelled. When compared to the system without the idle speed control, the energy saving of the proposed system is about 67%. The proposed two-level idle speed control system with a HA can achieve a high energy efficiency and a good control performance.
Highlights
Energy saving and environment friendly become the primary demands for the construction machinery under the environment of stringent emission regulations
When the time of the joystick backs to middle position is longer than time T1 + T2 and the pressure of hydraulic accumulator (HA) is under the threshold values, the controller makes the electric motor (EM) work at the second level idle speed n2, which is lower than the first level idle speed n1 to further reduce the energy consumption
When the controller detects the joystick staying at middle position for 8 s, which means that the actuator stops working for 8 s, and the controller makes the EM work at the first level idle speed (800 rpm) from time 15 s
Summary
Energy saving and environment friendly become the primary demands for the construction machinery under the environment of stringent emission regulations. Hao optimized the duty ratio of the PWM, minimum ramping time, and idle speed through adapting the adaptive control method and achieved a better energy saving effect [24]. Those researches were still based on the traditional engine and the idle speed cannot be too low to avoid the misfire. The adjusting time of the transition from the idle speed to the normal speed of the engine cannot be very short and the pumps cannot build the pressure quickly to drive the actuator when the idle mode is cancelled This leads to the instability of the actuator movement and a slow response to the working signal.
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