摘要:
A plurality of hydraulic actuators are connected between a supply line (14) and a tank return line (18). A separate desired velocity is requested for each hydraulic actuator. In response to a respective metering mode and the desired velocity for each hydraulic actuator, the flow requirements that each hydraulic actuator has from the supply and return lines are derived. A determination is made as to what fractions of the required flows can be provided by the flow levels that are available from the supply and return lines. Those fractions are used to convert the desired velocity for the given hydraulic actuator into a velocity command which indicates the velocity of the given hydraulic actuator that can be achieved with the available fluid flows. The respective velocity command is used to control the flow of fluid to each hydraulic actuator.
摘要:
The flow of fluid to a hydraulic actuator (16) is controlled by a valve assembly (25) which operates in different metering modes at various points in time. The metering mode to use in selected in response to the hydraulic load that acts on the valve (21-24) associated with the hydraulic actuator. Specifically the load is measured and then compared to threshold levels associated with the different metering modes to choose the metering mode for use a given point in time.
摘要:
An actuator (16) is part of a hydraulic circuit branch that has a first electrohydraulic proportional valve (21) connecting the actuator to a supply line containing pressurized fluid and a second electrohydraulic proportional valve connecting the actuator to a tank return line (24). A method for operating the valves includes requesting a desired velocity for the hydraulic actuator (16) and sensing a parameter which varies with changes of a force on the actuator. The desired velocity and the parameter are used to derive an equivalent flow coefficient which characterizes fluid flow in the hydraulic circuit. From the equivalent flow coefficient, first and second valve flow coefficient are derived and then employed to activate each of the first and second electrohydraulic proportional valves (21,24). The coefficients may characterize either conductance or restriction in the respective part of the hydraulic system (10).
摘要:
A programmable controller, for operating a machine such as one having a hydraulic system, includes a memory that stores a plurality of software function routines. A memory contains a first data file with address pointers to the function routines where the address pointers are listed in the order that the function routines may be executed. A second data file has a separate record associated with each of the address pointers and each record identifies the data variables required by the corresponding function routine. A third data file contains information about each of the variables. A code sequencer accesses the first data file and directs execution of the function routine in the order designated by the pointers. As each function routine executes, the respective record in the second data file is used to access the required variable information.
摘要:
An actuator (16) is part of a hydraulic circuit branch that has a first electrohydraulic proportional valve (21) connecting the actuator to a supply line containing pressurized fluid and a second electrohydraulic proportional valve connecting the actuator to a tank return line (24). A method for operating the valves includes requesting a desired velocity for the hydraulic actuator (16) and sensing a parameter which varies with changes of a force on the actuator. The desired velocity and the parameter are used to derive an equivalent flow coefficient which characterizes fluid flow in the hydraulic circuit. From the equivalent flow coefficient, first and second valve flow coefficient are derived and then employed to activate each of the first and second electrohydraulic proportional valves (21,24). The coefficients may characterize either conductance or restriction in the respective part of the hydraulic system (10).
摘要:
When a swinging boom (15) driven by a hydraulic cylinder (19) stops, inertia causes continued motion of the boom which increases pressure in a chamber (40,42) of the hydraulic cylinder. Eventually that pressure reaches a level which causes the boom to reverse direction. Then pressure in an opposite cylinder chamber (42,40) increases until reaching a level that causes the boom movement to reverse again. This oscillation continues until the motion is dampened by other forces acting on the boom. As a result, an operator has difficulty in properly positioning the boom. To reduce this oscillating effect, a sensor (48,49) detects when the cylinder chamber pressure increases above a given magnitude and then a determination is made when the rate of change of that pressure is less than a defined threshold. Upon that occurrence, a control value (33,34) is opened to relieve the pressure in that cylinder chamber (42,40).