Smooth control of hydraulic actuator
View Patent ↗A method and system is provided for controlling a hydraulic actuator in a work machine by opening a load holding valve in a measured fashion in order to leak hydraulic pressure back into a depressurized portion of the hydraulic circuit, thereby minimizing or eliminating jerkiness in the actuator when the actuator is under an external load.
1. A method for smoothly controlling a hydraulic actuator configured to actuate an implement that is acted upon by an external load in a first direction, the method comprising the steps of:
receiving a command input to move the implement in the first direction;
upon receipt of the command input, opening a load holding valve hydraulically connected between a pump and a side of the actuator upstream of the pump a first amount to create a leakage path, the first amount being less than fully open;
monitoring the pressure at the pump, and
fully opening the load holding valve once the pressure between the valve and the pump is equal to pressure between the valve and the actuator via the leakage path.
2. The method of claim 1 , further comprising monitoring a command input device.
3. The method of claim 2 , wherein the monitoring is continuous.
4. The method of claim 1 , wherein the command input is a control signal generated by a user-controlled input device.
5. The method of claim 1 further comprising:
comparing the monitored pump pressure with a predetermined threshold.
6. The method of claim 5 , further comprising:
further opening the load holding valve if the predetermined pressure threshold is not met.
7. The method of claim 5 , further comprising:
fully opening the load holding valve when the predetermined pressure threshold is met.
8. The method of claim 5 , wherein the monitoring pump pressure includes monitoring an electric current produced by a motor mechanically coupled to the pump.
9. The method of claim 1 , wherein the step of equalizing pressure between the valve and the pump with pressure between the valve and the actuator occurs after opening the load holding valve the first amount.
10. A method for smoothly controlling a hydraulic actuator configured to actuate an implement that is acted upon by an external load in a first direction, the method comprising the steps of:
receiving a command input to move the implement in the first direction;
upon receipt of the command input, metering flow from the actuator via a load holding valve hydraulically connected between a pump and a side of the actuator upstream of the pump;
monitoring the pressure at the pump, and
metering flow from the actuator via the pump once the pressure between the valve and the pump is equal to pressure between the valve and the actuator via the metered flow.
11. The method of claim 10 further comprising:
comparing the monitored pump pressure with a predetermined threshold.
12. The method of claim 11 , further comprising:
further opening the load holding valve if the predetermined pressure threshold is not met.
13. The method of claim 11 , further comprising:
metering the flow via the pump when the predetermined pressure threshold is met.
14. The method of claim 11 , wherein the monitoring pump pressure includes monitoring an electric current produced by a motor mechanically coupled to the pump.
15. The method of claim 10 , wherein the step of equalizing pressure between the valve and the pump with pressure between the valve and the actuator occurs after metering flow from the actuator via the load holding valve.
16. A hydraulic actuation system comprising:
a hydraulic pump;
a load holding check valve upstream of the pump;
a controller configured to generate and send command signals to the load holding check valve;
a sensor configured to monitor pump pressure;
wherein the load holding check valve is configured to partially open upon receipt of an open command signal, and wherein the load holding check valve is configured to fully open once the pressure between the valve and the pump is equal to pressure between the valve and the actuator.
17. The system of claim 16 , wherein the pressure sensor senses current generated by an electric motor mechanically coupled to the pump.
18. The system of claim 16 , wherein the controller is configured to generate a control signal to fully open the load holding check valve after pump pressure exceeds a predetermined pressure.
19. The system of claim 16 , further comprising an inverter and an electric machine mechanically coupled to the hydraulic pump, the inverter configured to store electrical energy generated by the electric machine when the pump is driven by fluid flow.