Drive control system for work machine

A drive control system for a work machine comprising:

• a work machine main body;
• a front work implement attached pivotably in an upward and downward direction with respect the work machine main body and having a plurality of movable parts;
• a drive actuator configured to drive each of the movable parts of the front work implement;
• a calculation device configured to perform a control calculation for controlling driving of the drive actuator;
• an actuator drive hydraulic circuit including
• a flow control valve configured to control supply of hydraulic fluid to the drive actuator, and
• a proportional pressure reducing valve configured to output pilot hydraulic fluid to be supplied to the flow control valve based on an operation of a control lever;
• a lever operation amount detection unit configured to detect an operation amount of the control lever;
• and
• an attitude detection unit configured to detect an attitude of the work machine, wherein:
• the calculation device includes
• a stability judgment section configured to predict, based on the operation amount of the control lever detected by the lever operation amount detection unit and the attitude of the work machine detected by the attitude detection unit, a behavior of the work machine when it is assumed that the work machine stops suddenly and judge stability of the work machine, and
• an operation limitation determination section configured to calculate and output a gradual stoppage command for limiting a deceleration of the drive actuator based on a result of the judgment of the stability judgment section to gradually stop the drive actuator and an operation speed limitation command for limiting an upper limit operation speed of the drive actuator;
• the actuator drive hydraulic circuit includes a pilot pressure correction unit configured to correct a pilot pressure to be outputted from the proportional pressure reducing valve in response to the gradual stoppage command and the operation speed limitation command from the operation limitation determination section;
• the pilot pressure correction unit is configured from
• a stoppage characteristic modification unit configured to correct the pilot pressure such that the drive actuator is stopped gradually upon a stoppage operation of the control lever, and
• an operation speed limitation unit configured to correct the pilot pressure such that the operation speed of the drive actuator is limited;
• the stoppage characteristic modification unit and the operation speed limitation unit are individually driven by the gradual stoppage command and the operation speed limitation command from the operation limitation determination section such that, when the gradual stoppage command and the operation speed limitation command are inputted from the operation limitation determination section, the pilot pressure to be outputted from the proportional pressure reducing valve is corrected, but when the gradual stoppage command and the operation speed limitation command are not inputted from the operation limitation determination section, the pilot pressure outputted from the proportional pressure reducing valve is supplied to the flow control valve without being corrected;
• the stoppage characteristic modification unit includes a speed increasing unit provided on a pilot line that connects the proportional pressure reducing valve and the flow control valve, the speed increasing unit including a speed increasing solenoid proportional valve connected to a pilot hydraulic fluid supply device other than the proportional pressure reducing valve so as to generate and output a pressure higher than a pilot pressure outputted from the proportional pressure reducing valve;
• the operation speed limitation unit includes a speed reducing unit configured to reduce and output the pilot pressure;
• the drive control system further includes a failure detection unit configured to detect a failure of the speed increasing solenoid proportional valve included in the speed increasing unit;
• the actuator drive hydraulic circuit further includes a speed increase interruption unit configured to interrupt supply of the pilot hydraulic fluid from the pilot hydraulic fluid supply device other than the proportional pressure reducing valve to the speed increasing unit;
• and
• the calculation device causes, when a failure of the speed increasing solenoid proportional valve is detected by the failure detection unit, the speed increase interruption unit to interrupt supply of the pilot hydraulic fluid to the speed increasing unit.