| Hydraulic excavator is an important construction machinery widely used in earthwork construction.Driven by the energy-environment development requirements and humanmachine friendly interaction demand,people has put forward higher and higher requirements for energy saving and maneuverability of excavators.At present,multi-way valve hydraulic system is a mainstream system with high integration and good reliability in excavator market.However,due to the incompatibility between human-input characteristics,system control characteristics and load characteristics,the actual flow state of hydraulic power deviates from its desired state,so that the pressure-flow dynamic matching degree between supply and demand is relatively low,and the system still suffers from low efficiency,poor stability and poor coordination.Therefore,in view of the insufficient working performance of the existing LUDV(Load Independent Flow Distribution),negative control multi-way valve systems,this paper carries out research on hydraulic power flow control and optimization technology based on main valve adjustment.Analysis on the characteristics of multi-way valve hydraulic system and hydraulic power flow regulation model.Based on the chamber-damping-inertia model of actuator,the effect of input flow and oil return damping on actuator driving pressure characteristics and braking-stop speed characteristics is explored,so that entry points of hydraulic power flow optimization control are defined.Based on the hydraulic power flow regulation model,the basic methods of system performance optimization control is discussed from three aspects:supply-demand pressure flow matching,working chamber pressure dynamic regulation,and actuator flow ratio regulation.And then,the key points of power flow optimization regulation are clarified.Main valve input shaping and LUDV actuator stability optimization control.Taking the LUDV swing-boom system as the research object,according to the stage variation characteristics of load pressure,this paper divides the actuator acceleration-braking process into pressure build-up,inertial-acceleration,stable-flow,damping-deceleration,stoposcillation working condition,so as to adjust main valve control signal slope in several sections,and then mainly solves the problem of poor stability of LUDV hydraulic actuator during its acceleration and braking process.During the actuator acceleration process,the inertia load and the pressure energy storage-release process of driving chamber are adjusted to smooth the driving pressure fluctuation by adjusting main valve flow growth rate,and the maximum starting pressure overshoot dropped from 80% to 16%.During the hydraulic cylinder braking process,the cylinder braking-stop initial state parameters are adjusted to restrain the pressure oscillation caused by load inertia,by limiting main valve control pressure change rate,reducing the closing speed of oil return channel,prolonging the actuator damping-deceleration time,and the maximum brake pressure overshoot drops from74% to 28%.Based on the structure,hydraulic parameters and test data of 6-ton LUDV excavator,a virtual excavator that can accurately simulate the real swing or boom lifting action is built,and the model-in-the-loop test is carried out,so as to verify the correctness of the input shaping control principle.Correction control of main valve and working condition-adaptive control of negative control excavator.Taking the swing-boom system as the research object,an electric proportional pressure reducing valve is added to the original hydraulic main valve pilot control circuit,and the valve control pressure is adjusted to make the valve opening dynamically match the control demand,and then the energy efficiency,stability and flow distribution characteristics of negative control excavator under three extreme working conditions,such as overpressure of hydraulic cylinder,passive release of motor brake pressure and imbalance flow ratio of multi-way valve,are improved.In the overpressure working condition,the on-demand flow control is adopted to adjust main valve-negative feedback pressure,and reduce the pump flow supply,thereby suppressing the pump overflow caused by overload.In the motor brake pressure passive release working condition,the active pressure release control is adopted,the motor outlet channel is properly opened by adjusting main valve,and the motor brake pressure is actively released,thereby suppressing the reverse-oscillation.In the swing-boom compound action working condition,the actuator flow ratio control and action priority control are adopted to adjust main valve opening ratio to distribute the dual pump flow according to control requirements,so as to actively adjust the flow distribution characteristics of the multi-way valve system.Based on the structure,hydraulic parameters and test data of 37-ton negative control excavator,a virtual excavator that can accurately simulate the real swing-boom lifting action is built,and the model-in-the-loop test is carried out,so as to verify the correctness of working conditionadaptive control algorithm.Control code generation,testing and verification.The discrete input shaping and adaptive control algorithm models are built,and corresponding control codes are generated.The control code-virtual controller is imported into the virtual excavator,and the softwarein-the-loop tests of the two control algorithms are carried out to verify its expected control functions.The virtual debugging method is used to verify that the two control codes can run correctly in the programmable logic controller,so as to verify the feasibility of the two control algorithms. |
