Abstract
In order to improve the energy efficiency and dynamic of negative control swing systems of excavators, this paper proposes a technical scheme of adding two PRVs (pressure reducing valves) to main valve pilot control circuit, which can adjust main value opening arbitrarily according to the working condition. A pump-value compound control strategy was formulated to regulate the system power flow. During swing motor acceleration, main pump and the two PRVs are controlled to match system supply flow with motor demand flow, thereby reducing motor overflow and shortening system response time. During swing motor braking, the channel from motor to tank is opened to release hydraulic brake pressure by controlling PRVs before swing speed reduces to zero, which prevents the motor from reversing and oscillating. A simulation model of 37-ton excavator was established, and the control strategy was simulated. The original and optimized performance of the swing system were compared and analyzed, and results show that the application of new scheme with the compound control strategy can reduce overflow and increase braking stability of the swing system. In addition, system response and speed control performance are also improved when excavator performs a single-swing action.
Highlights
In a typical working cycle of an excavator, the running time of the swing system accounts for about 50–70% of the total running time, and the energy consumption of the swing system accounts for 25–40% of the total consumption [1]
Frequent switching of motor acceleration and deceleration makes the swing system often work in the state of over-matching and under-matching [3,4], the supply power of system does not match the demand power of actuator, and system response and stability deteriorate which seriously affects the operator’s experience
PRVs are an independent metering for the swing main valve, so the main valve pilot pressure and opening can be arbitrarily adjusted to optimize the performance of the negative control swing system
Summary
In a typical working cycle of an excavator, the running time of the swing system accounts for about 50–70% of the total running time, and the energy consumption of the swing system accounts for 25–40% of the total consumption [1]. Yu et al [10,11] proposed a new energy regenerative swing system with two accumulators, and the energy efficiency and stability have been effectively improved through combined control of motor displacement, main valve opening, and accumulator. Yan et al [12] proposed a hydraulic slewing system based on secondary regulation control, which can make the swing motor reach the specified speed quickly and smoothly through PID control. Considering the upgrade cost of hydraulic systems, this paper proposes a technical scheme which adds two PRVs (pressure reducing valves) to the main valve pilot control circuit, and the PRVs are an independent metering for the swing main valve, so the main valve pilot pressure and opening can be arbitrarily adjusted to optimize the performance of the negative control swing system. A compound control strategy of an electric proportional pump and two PRVs was formulated, and a simulation model of a 37-ton excavator was established to verify the correctness of the strategy
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