Method for operating a hydrostatic actuator system
A hydrostatic actuator system includes an electric motor for delivering a hydraulic fluid via a piston unit. The actuator system is operating using a method in which a change in volume caused by a temperature change is sensed by a pressure measurement. The method reliably identifies a state of the transfer of the hydraulic fluid from a planetary roller transmission compartment into the master piston. The pressure measurement is continuously evaluated, and, in the event of a negative signal of the pressure measurement, suction of the hydraulic fluid by a planetary roller transmission lying in the hydraulic fluid between the electric motor and the piston unit into the piston unit is recognized and a fault signal is output.
1. A method for operating a hydrostatic actuator system, in which an electric motor is used for delivering a hydraulic fluid in the actuator having a piston unit, in which a change in volume of the hydraulic fluid caused by a temperature change is sensed by a pressure measurement, wherein the pressure measurement is continuously evaluated, wherein, in the event of a negative signal of the pressure measurement, suction of the hydraulic fluid by a planetary roller transmission lying in the hydraulic fluid between the electric motor and a spindle into the piston unit is recognized and a fault signal is output, and in which a sniffing action is triggered on the basis of the fault signal to eliminate a shift in a characteristic curve.
2. The method according to claim 1 , wherein the fault signal is output if the negative signal of the pressure measurement lasts for a predetermined period of time.
3. The method according to claim 1 , wherein the negative pressure signal is less than −0.2 bar.
4. The method according to claim 2 , wherein the predetermined time period is at least 0.3 seconds.
5. The method according to claim 1 , wherein a position signal of the actuator is continuously monitored and the fault signal is output when the actuator moves back from a high actuator position to a low actuator position.
6. The method according to claim 5 , wherein the continuous evaluation of the pressure signal and the position signal takes place during a diagnostic process which is carried out in response to a predetermined ambient temperature.
7. The method according to claim 1 , wherein the sniffing action is immediately initiated in response to the fault signal.
8. An actuator system comprising:
a spindle;
a master cylinder;
a piston within the master cylinder and axially fixed to the spindle;
an electric motor driving the spindle via a planetary transmission, the planetary transmission being encased in a sleeve;
a pressure sensor within the sleeve; and
a controller programmed to evaluate a signal from the pressure sensor and output a fault signal in response to a negative pressure.
9. The actuator system according to claim 8 , wherein the fault signal is output if the negative pressure lasts for a predetermined period of time.
10. The actuator system according to claim 9 , wherein the predetermined time period is at least 0.3 seconds.
11. The actuator system according to claim 9 , wherein the fault signal is output in response to the negative pressure being less than −0.2 bar.
12. The actuator system according to claim 8 , further comprising a spindle position sensor and wherein the fault signal is output when the actuator moves back from a high actuator position to a low actuator position.
13. The actuator system according to claim 12 , wherein the controller evaluates the pressure signal and a position signal during a diagnostic process which is carried out in response to a predetermined ambient temperature.
14. The actuator system according to claim 8 , wherein a sniffing request is triggered on the basis of the fault signal.
15. The actuator system according to claim 14 , wherein a sniffing process is immediately initiated in response to the fault signal.