Adaptive Friction Minimization for Electrohydraulic Actuators.

Abstract

To improve control of an electromechanical actuator.SOLUTION: The present invention relates to a control method for an electromechanical actuator (101). The method comprises determining a voltage (U) applied to the actuator (101) by superimposing a control variable on a vibration signal, and measuring an oil pressure affected by the actuator (101). The vibration signal is adjusted according to the measured oil pressure.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The invention relates to a control method according to the preamble of claim 1, an assembly according to claim 6, a computer program according to claim 7 as well as a data processing device according to claim 8. [Background technology]

[0002] It is known in the prior art to apply an electrical vibration signal to an electrohydraulic actuator. This reduces mechanical friction in the actuator. However, vibrations in a hydraulic system can have undesirable effects, which are captured on a test bench and stored in a control device.

[0003] Since the conditions occurring in reality can only be approximately reproduced on a test bench, the actuators must be controlled with a safety margin to ensure that a safety margin is maintained in conditions that could be critical for the system. This has the drawback that the actuators' performance cannot be maximized. Summary of the Invention [Problem to be solved by the invention]

[0004] SUMMARY OF THE DISCLOSURE The object of the present invention is to improve the control of electromechanical actuators. [Means for solving the problem]

[0005] This problem is solved by a control method according to claim 1, an assembly according to claim 6, a computer program according to claim 7 and a data processing device according to claim 8. Advantageous configurations are set out in the dependent claims and will become apparent from the following description and the embodiment shown in FIG.

[0006] The method according to the invention envisages the use of an electro-hydraulic actuator, which is configured to affect the hydraulic pressure depending on an applied voltage. There is a functional link between the voltage and the hydraulic pressure. The hydraulic pressure is a function of one or more parameters. These parameters include the voltage. In particular, the hydraulic pressure may depend only on the voltage.

[0007] As mentioned above, in order to reduce the mechanical friction in the actuator, an oscillation is added to the voltage applied to the actuator, i.e. the voltage is determined by superposing a variable (hereafter called the control variable) with the oscillation signal.

[0008] A vibration signal is a quantity that repeatedly varies over time, i.e. a deviation from a mean value. Its value repeatedly deviates from the mean value. Its value is preferably zero. The vibration signal can be, for example, a sinusoidal vibration.

[0009] It is preferable that the vibration signal on which the control variable is superimposed does not cause interference between the control variable and the vibration signal that cancels out the vibration signal. If the vibration signal is canceled out, the voltage determined by the superposition does not fluctuate over time. In other words, this means that the voltage is oscillating.

[0010] The oscillating voltage causes the actuator to produce mechanical vibrations, which on the one hand reduces the mechanical friction of the actuator, but on the other hand the hydraulic pressure influenced by the actuator can also produce vibrations.

[0011] In order to avoid undesirable effects due to vibrations in the hydraulic pressure, the hydraulic pressure is measured. According to the invention, the vibration signal is adjusted according to the measured hydraulic pressure. The adjusted vibration signal is different from the vibration signal superimposed with the control variable before the adjustment.

[0012] In a further preferred embodiment, the hydraulic vibrations are measured, since it is in particular the hydraulic vibrations that have the undesirable effect. In a further preferred embodiment, in particular the amplitude, the frequency and / or the signal shape of the hydraulic pressure can be measured.

[0013] The method according to the invention preferably includes adjusting the vibration signal in response to the amplitude, frequency and / or signal shape of the measured oil pressure, which may be calculated from the oil pressure measurement or may be measured directly as described above.

[0014] Conditioning of the vibration signal is accomplished in preferred configurations by adjusting the amplitude, frequency and / or signal shape of the vibration signal.

[0015] In a further preferred arrangement, the expected oil pressure is determined as a function of the control variables and / or the vibration signal. The determination of the expected oil pressure can be performed by calculation or simulation.

[0016] According to a further embodiment, the vibration signal is adjusted as a function of the deviation between the measured oil pressure and the expected oil pressure, which means that the deviation is calculated in a further method step. The adjustment is preferably performed in such a way that the deviation is minimized, which makes it possible to minimize the influence of disturbance variables.

[0017] The assembly according to the invention comprises an electrohydraulic actuator, a hydraulic line, a sensor and a data processing device, the actuator being adapted to affect the hydraulic pressure in the hydraulic line in response to a voltage specified by the data processing device as described above.

[0018] A voltage specified by the data processing device is applied to the actuator, which in turn influences the hydraulic pressure as described above. In particular, the actuator can be configured to generate a hydraulic pressure depending on the voltage. Alternatively, an actuator configured, for example, as a pressure regulating valve is also conceivable, which regulates the magnitude of the hydraulic pressure generated by the further actuator.

[0019] The assembly may, for example, be part of an automatic transmission, in which the individual gears are shifted via hydraulically actuated clutches and / or brakes, where at least one brake or clutch is actuated via hydraulic pressure influenced by an actuator.

[0020] The assembly according to the invention is designed to implement the method according to the invention or a preferred configuration thereof. In particular, the sensor is arranged to measure the liquid pressure. A signal from the sensor is provided as an input signal to a data processing device. According to the invention, the data processing device is arranged to adjust the vibration signal as described above depending on the measured pressure.

[0021] A data processing device according to the invention is designed to carry out the method according to the invention or a preferred arrangement. Preferably, the data processing device is adapted or designed to be suitable for use in an assembly according to the invention.

[0022] The computer program according to the invention is designed to cause a data processing apparatus to carry out the method according to the invention or a preferred arrangement. The carrying out of the method according to the invention by the data processing apparatus is achieved by the computer program being executed on the data processing apparatus.

[0023] A preferred embodiment of the present invention is shown in FIG. [Brief description of the drawings]

[0024] [Figure 1] FIG. 2 is an explanatory diagram showing a hydraulic system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] The system shown in FIG. 1 includes an electro-hydraulic actuator 101 , a hydraulic pipe 103 , a pressure sensor 105 , a control device 107 , and a signal line 109 .

[0026] A voltage U is applied to the actuator 101. The actuator 101 is controlled via the voltage U.

[0027] The actuator 101 influences the hydraulic pressure in the hydraulic line 103. This occurs as a function of a voltage U, i.e. the hydraulic pressure is dependent on the voltage U. To reduce the mechanical friction occurring in the actuator 101, an oscillation is applied to the voltage.

[0028] The hydraulic pressure in the hydraulic line 103 is measured by a pressure sensor 105. The measured values ​​of the pressure sensor 105 are evaluated and further processed by a control device 107. For this purpose, the pressure sensor 105 is signal-transmittingly connected to the control device 107 via a signal line 109.

[0029] The control device 107 analyzes the pressure signal transmitted from the pressure sensor 105 via the signal line 109 for the presence or absence of anomalies. In case of anomalies, the control device 105 appropriately adjusts the oscillation applied to the voltage U. [Explanation of symbols]

[0030] 101 Actuator 103 Hydraulic Pipe 105 Pressure Sensor 107 Control device 109 Signal Line U Voltage

Claims

1. A control method for an electrohydraulic actuator (101), comprising determining a voltage (U) applied to said actuator (101) by superimposing a control variable with a vibration signal and measuring an oil pressure dependent on said voltage (U) applied to said actuator (101), comprising: adjusting the vibration signal in response to the measured oil pressure.

2. 2. A method according to claim 1, characterized in that oscillations in the hydraulic pressure are measured.

3. 3. A control method according to claim 1 or 2, characterized in that the vibration signal is adjusted depending on the amplitude, frequency and / or signal shape of the measured oil pressure.

4. A control method according to any one of claims 1 to 3, characterized in that the amplitude, the frequency and / or the signal shape of the vibration signal are adjusted.

5. Control method according to any one of claims 1 to 4, characterized in that an expected oil pressure is determined as a function of the control variable and / or the vibration signal, and that the vibration signal is adjusted to the expected oil pressure as a function of the deviation from the measured oil pressure.

6. 1. An assembly comprising an electrohydraulic actuator (101), a hydraulic line (103), a sensor (105) and a data processing device (107), the actuator (101) being configured to influence a hydraulic pressure in the hydraulic line (103) depending on a voltage (U) specified by the data processing device (107), the data processing device (107) determining the voltage (U) by superimposing a control variable with a vibration signal, the sensor (105) being configured to measure the hydraulic pressure, 4. The assembly, characterized in that the data processing device (107) is configured to adjust the vibration signal in response to the measured oil pressure.

7. A data processing device (107), configured to perform the method according to any one of claims 1 to 5.

8. A computer program arranged to cause a data processing device (107) to carry out the method according to any one of claims 1 to 5.

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