Method for adjusting a force that can be provided by means of an electromechanical actuator

Abstract

The invention relates to a method for regulating a force which is available by means of an electromechanical actuator. The method has the following steps: generating a first control signal which corresponds to a deviation sought by a first adder of a force regulation loop by means of a target force and an actual force, inputting the first control signal into a phase-locked loop of the force regulation loop, generating an actuator control signal by means of a second adder by adding a second control signal which is variable over time and is output by an oscillator to the first control signal, actuating the electromechanical actuator by means of the actuator control signal, seeking a phase difference between the actuator control signal and the rotor orientation of the electric motor by means of a phase comparator, feeding a phase difference signal which is output by the phase comparator and corresponds to the phase difference to a phase regulator which is designed to generate an oscillator control signal on the basis of the phase difference signal, feeding the oscillator control signal to the oscillator which is designed to generate the second control signal which is variable over time on the basis of the oscillator control signal, generating a signal which corresponds to the actual force on the basis of the oscillator control signal, and feeding the signal to the first adder.

Description

Technical Field

[0001] The present invention relates to a method for regulating the force available by means of an electromechanical actuator. Background Technology

[0002] Electromechanical actuators are used in many technical fields, such as as actuators in vehicle braking systems. Here, electromechanical actuators are used to generate a force that causes the brake pads to press against the brake drum or brake disc.

[0003] The problem of finding a suitable sensor system or method for determining the operating force remains open for electromechanical brakes. Existing (conditionally suitable) solutions also include path-based methods, where the relationship between clamping / expansion force and the rotor orientation of the regulating motor, such as a brushless DC motor, is used. A drawback of this approach is that liner stiffness, wear condition, and other influences, such as thermal expansion in the brake drum, significantly affect the relationship between the clamping / expansion force and the rotor orientation (i.e., the path). Furthermore, these influences cannot be modeled or measured with sufficient accuracy, or can only be modeled or measured with sufficient accuracy at a higher cost. The installation of sensors for directly measuring the force is associated with very high costs due to the environmental influences of the load in the brake (e.g., contamination, temperature, vibration, etc.), and is therefore not preferred.

[0004] To estimate force based on a model by regulating the current of a motor, precise knowledge of the model structure and parameters is required, such as those describing frictional losses in the drive stage or bearings. Model development and parameter determination are complex and may necessitate additional sensor systems. Furthermore, operating parameters can vary (e.g., due to temperature), which can negatively impact the accuracy and reliability of model-based estimations. Summary of the Invention

[0005] The objective of this invention is to describe a solution to the aforementioned problems.

[0006] In the first aspect, this task is solved by a method for adjusting the force available by means of an electromechanical actuator having an electric motor, wherein the method has:

[0007] - Generate a first control signal, which corresponds to the deviation between the target force and the actual force calculated by the first adder in the force adjustment loop.

[0008] - A phase-locked loop that inputs the first control signal into the force regulation circuit has the following characteristics:

[0009] - Second adder,

[0010] - Electromechanical actuator,

[0011] - Phase comparator,

[0012] - Phase adjuster, and

[0013] - Oscillator,

[0014] The method also has the following characteristics:

[0015] - An actuator control signal is generated by adding the time-varying second control signal output from the oscillator to the first control signal using a second adder.

[0016] - Control the electromechanical actuator using actuator control signals.

[0017] - The phase difference between the actuator control signal and the rotor position of the motor is determined using a phase comparator.

[0018] - The phase difference signal, output from the phase comparator and corresponding to the phase difference, is fed to the phase adjuster, which is designed to generate oscillator control signals based on the phase difference signal.

[0019] - An oscillator control signal is fed to an oscillator designed to generate a time-varying second control signal based on the oscillator control signal, and

[0020] - A signal corresponding to the actual force is generated based on the oscillator control signal, and the signal is sent to the first adder.

[0021] The problems discussed above using conventional methods can be solved using the method according to the present invention because:

[0022] - No force sensor is required, as force sensors typically require installation at a higher cost.

[0023] - No detailed model of the electromechanical actuator is required, and

[0024] - The method is not affected by changes in force path relationships, such as those that depend on temperature or are caused by wear.

[0025] The signal corresponding to the actual force can be generated, for example, based on a lookup table or instantaneous value table, which stores a clear relationship between the oscillator control signal and the force. This relationship can be obtained in advance (e.g., by direct measurement) and stored, and is therefore independent of the model of the electromechanical actuator.

[0026] In order to ensure that there is a clearly defined phase difference between the rotor orientation and the actuator control signal, the second control signal can also be specified as a periodic signal, such as a sine wave signal.

[0027] The phase adjuster is designed to adjust the phase difference to a preset phase difference corresponding to a specific oscillator control signal. The oscillator control signal, in turn, corresponds to a specific frequency of a signal generated by the oscillator. To ensure a high degree of robustness to parameter variations relative to the actuator or actuator system with the actuator, the oscillator control signal may be specified to correspond to the inherent frequency of the electromechanical actuator or actuator system.

[0028] If the frequency of the second control signal, i.e., the excitation frequency, corresponds to the undamped natural frequency of the actuator system, then the phase difference between the rotor orientation and the actuator control signal is one-quarter of the cycle duration (i.e., 90° or π / 2). A phase adjuster can be designed to adjust the phase difference to one-quarter of the cycle duration. Thus, the excitation frequency can be adjusted to the undamped natural frequency.

[0029] The method according to the invention can be used in applications requiring precise motor position signals, such as steering systems. Furthermore, the method can be used to adjust braking force in electromechanical braking systems, where the electromechanical actuator is part of the electromechanical vehicle brake.

[0030] In a second aspect of the invention, a computer program is provided, the computer program including instructions that, when executed by a computer, cause the computer to perform the aforementioned method.

[0031] In a third aspect of the invention, a computer-readable storage medium is provided on which a computer program according to the second aspect is stored.

[0032] In a fourth aspect of the invention, a vehicle braking system is provided, the vehicle braking system having one or more electromechanical brakes and one or more control / adjustment devices designed to perform adjustment according to the method described above.

[0033] Vehicle braking systems may have a central control / regulation device designed to control / regulate multiple or all of the electromechanical brakes.

[0034] In a fifth aspect of the invention, a vehicle is provided having a vehicle braking system according to the fourth aspect. Attached Figure Description

[0035] The present invention will now be described in detail with reference to the accompanying drawings.

[0036] Figure 1 A schematic diagram of an exemplary vehicle with an electromechanical vehicle braking system is shown.

[0037] Figure 2 A schematic diagram of a regulating circuit for adjusting the force provided by an electromechanical actuator is shown.

[0038] Figure 3 A diagram showing time curves displaying actuator control signals, rotor orientation, and actuation force during the execution of the method according to the invention is presented.

[0039] Figure 4 An exemplary flowchart of an exemplary method according to the present invention is shown. Detailed Implementation

[0040] As previously stated, the method according to the invention can be used in many technical fields, such as for adjusting braking force provided by an electromechanical brake or steering force in a steering system.

[0041] Without limiting specific applications, the method according to the present invention is based on Figure 1 The vehicle braking system 100 of the vehicle 10 shown is described.

[0042] The vehicle braking system 100 may include: a first front wheel brake 120-1 associated with a first front wheel 12-1 and a second front wheel brake 120-2 associated with a second front wheel 12-2 on the front axle 12 of the vehicle 10; and a first rear wheel brake 140-1 associated with a first rear wheel 14-1 and a second rear wheel brake 140-2 associated with a second rear wheel 14-2 on the rear axle 14 of the vehicle 10. The first front wheel brake 120-1, the second front wheel brake 120-2, the first rear wheel brake 140-1, and the second rear wheel brake 140-2 are configured as electromechanical brakes.

[0043] The vehicle braking system 100 also includes a control device 160 designed to individually control / adjust the first front wheel brake 120-1, the second front wheel brake 120-2, the first rear wheel brake 140-1, and the second rear wheel brake 140-2. The control device 160 can, for example, be connected in a signal exchange manner with the first front wheel brake 120-1, the second front wheel brake 120-2, the first rear wheel brake 140-1, and the second rear wheel brake 124-2 via signal exchange lines 160-1, 160-2, 160-3, and 160-4.

[0044] The control device 160 may, for example, have a computer-readable storage medium 160-11 and a data processing device 160-21. A computer program comprising instructions, when executed by the data processing device 160-21, may be stored on the storage medium 160-11. These instructions, when executed by the data processing device 160-21, cause the data processing device 160-21 to perform a method for controlling / adjusting the vehicle braking system 100, which subsequently... Figures 2 to 4 It is described in detail.

[0045] Storage media 160-11 may include, for example, random access memory, read-only memory, hard disk, etc. Data processing apparatus 160-21 may include, for example, a processor, application-specific integrated circuit (ASIC), etc. Data processing apparatus 160-21 and consequently control apparatus 160 can therefore be understood as computers in the sense of this disclosure.

[0046] The control device 160 may be designed to perform a method for adjusting the braking force available by means of one of the brakes 120-1, 120-2, 140-1, 140-2.

[0047] Figure 2 An exemplary force regulation circuit 200 is shown. The regulation circuit 200 consists of a first adder 210, an integrator 220, a phase-locked loop 300, and a lookup table 230.

[0048] The phase-locked loop 300 consists of a second adder 310, an electromechanical actuator 320, a phase comparator 330, a phase adjuster 340, and an oscillator 350. The electromechanical actuator 320 has an electric motor and may have a rotary-translational drive, which is designed to convert the rotational motion of the motor shaft (rotor) into translational motion, through which the brake pads of the associated vehicle brake can compress the brake drum or brake disc.

[0049] During operation, a signal F corresponding to the target braking force is generated when the brake pedal is operated. Soll Signal F Soll The signal is fed to the first adder 210, where it is received from signal F. Soll Subtract the signal F corresponding to the actual braking force Ist Adder 210 outputs a signal ΔF to integrator 220, which corresponds to the difference between the target force and the actual force. Based on this signal, integrator 220 generates a first control signal τ. const The first control signal is sent to the second adder 310 of the phase-locked loop 300. The first control signal τ const It can be a current or voltage signal corresponding to the torque that should be output by the motor of actuator 320.

[0050] In adder 310, the first control signal τ const With the second control signal τ that varies with time e The sums are added together, and the summation signal is used as the actuator control signal τ. mot The output actuator control signal is sent to the motor of the electromechanical actuator 320. The actuator control signal τ is then transmitted. mot At this time, the motor shaft / rotor is rotating.

[0051] Figure 3 The actuator control signal τ is shown.mot Rotor azimuth θ mot And the curve of the actuation force F of actuator 320 with respect to time t. Actuator control signal τ mot It has an average value τ const , amplitude A τ and frequency f τ That is, the period f τ -1 The periodic signal. Rotor azimuth θ mot After the response time t0 (Einschwingzeit), it essentially has the same response as the actuator control signal τ. mot The same frequency, and relative to the actuator control signal τ mot Phase misalignment, i.e., at rotor azimuth θ mot With actuator control signal τ mot There is a phase difference (phase offset) Δφ between them. The actuation force F follows the rotor azimuth θ. mot It also exhibits a periodic curve around the average value (operating point) F0 after the response time t0.

[0052] The phase difference Δφ is frequency-dependent and forms at the operating point F0 based on the rotational mass (Schwungmasse) and stiffness of the actuator 320 or the actuator system having the actuator 320. The rotational mass is structurally determined and can be considered constant.

[0053] The rotor orientation θ can be detected over time using a sensor provided on actuator 320. mot And the sensor's orientation θ relative to the rotor mot The corresponding signal is sent to phase comparator 330, which is designed to determine the actuator control signal τ. mot With rotor orientation θ mot The phase difference Δφ between them.

[0054] The phase difference signal corresponding to the phase difference Δφ is then fed to a phase adjuster 340, which is designed to generate an oscillator control signal f based on the phase difference signal. e The oscillator control signal is sent to oscillator 350. Oscillator 350 is designed to operate based on the oscillator control signal f. e Generate a time-varying second control signal τ e The second control signal is sent to the second adder 310 as performed previously.

[0055] Oscillator 350 can be designed to generate a periodic second control signal τ. e Therefore, for example, a defined phase difference can be provided. Oscillator 350 can be as follows: Figure 2The diagram shows a sine wave generator 350-1 and a post-amplifier 350-2, which is designed to amplify the sine wave generated by the sine wave generator 350-1 to an amplitude A. τ .

[0056] Therefore, the actuator control signal τ can be controlled using the phase-locked loop 300. mot With rotor orientation θ mot The phase difference Δφ between the two phases is adjusted to the desired phase difference, thereby generating a second control signal τ with the desired frequency using the oscillator 350. e By adjusting to a specific phase difference Δφ, a second control signal with a frequency generated using the inherent frequency of actuator 320 or an actuator system having actuator 320 can be generated. This ensures a high degree of robustness relative to parameter changes (e.g., attenuation changes) in the actuator or actuator system.

[0057] If the second control signal τ e If the excitation frequency corresponds to the undamped natural frequency of the actuator system, then the phase difference Δφ is one-quarter of the period duration (i.e., 90° or π / 2). The phase adjuster 340 can be designed to adjust the phase difference Δφ to one-quarter of the period duration. Thus, the excitation frequency can be adjusted to the undamped natural frequency.

[0058] In addition, the signal F corresponding to the actual braking force Ist Based on oscillator control signal f e The signal F corresponding to the actual braking force is generated and fed to the first adder 210. Ist For example, a lookup table 230, i.e., a value table, can be generated, in which the explicit relationship between the oscillator control signal and the force is stored.

[0059] This method eliminates the need for a braking force sensor, which is typically expensive to install. Furthermore, a detailed model of the electromechanical actuator 320 is not required. The method is applicable even when the force path characteristic curve is unknown, and therefore is unaffected by temperature-dependent or wear-induced variations in the force path characteristic curve.

[0060] Subsequently, with the help of Figure 4 The flowchart shown describes an exemplary method 400 for adjusting a braking force that can be provided by means of an electromechanical actuator 320. Method 400 has:

[0061] - Generate the first control signal τ const This corresponds to the deviation obtained by the first adder 210 of the force adjustment loop 200 between the target force and the actual force (410).

[0062] - The first control signal τ const Input (420) to phase-locked loop 300,

[0063] - By using the second adder 310, the time-varying second control signal τ output by the oscillator 350 is converted into a control signal. e With the first control signal τ const The summation produces the (430) actuator control signal τ. mot ,

[0064] - Control signal τ using an actuator mot Control (440) electromechanical actuator 320,

[0065] - The (450) actuator control signal τ is obtained using phase comparator 330. mot relative to the rotor orientation θ of the motor mot The phase difference Δφ between them

[0066] - The phase difference signal, output by phase comparator 330 and corresponding to the phase difference, is fed to phase adjuster 340, which is designed to generate (460) oscillator control signal f based on the phase difference signal. e ,

[0067] - The oscillator control signal f e The signal is fed to oscillator 350, which is designed to operate based on the oscillator control signal f. e Generate a time-varying second control signal τ e ,and

[0068] - Based on oscillator control signal f e Generate a signal F corresponding to the actual braking force. Ist And transmit the signal (480) to the first adder 210.

Claims

1. A method (400) for regulating a force available by means of an electromechanical actuator (320) having an electric motor, wherein, The method (400) has the following characteristics: - Generate (410) first control signal (τ) const The first control signal corresponds to the deviation between the target force and the actual force obtained by the first adder (210) of the force adjustment loop (200). - The first control signal (τ) const The phase-locked loop (300) inputs the force adjustment circuit (200), wherein the phase-locked loop (300) has: - Second adder (310) - Electromechanical actuator (320). - Phase comparator (330). - Phase adjuster (340), and - Oscillator (350). The method further includes: - By means of the second adder (310), the time-varying second control signal (τ) output by the oscillator (350) is combined with the second adder (310). e ) and the first control signal (τ) const The sum of these signals produces a (430) actuator control signal (τ). mot ), - Control signal (τ) via the actuator mot (440) controls the electromechanical actuator (320). - The actuator control signal (τ) is obtained (450) by means of the phase comparator (330). const ) and the rotor orientation (θ) of the motor mot The phase difference (Δφ) between them. - The phase difference signal output by the phase comparator (330) and corresponding to the phase difference (Δφ) is transmitted (460) to the phase adjuster (340), which is designed to generate an oscillator control signal (f) based on the phase difference signal. e ), - The oscillator control signal (f) e ) is transmitted (470) to the oscillator (350), the oscillator being designed to operate based on the oscillator control signal (f e Generates a second control signal (τ) that varies with time. e ),and - Based on the oscillator control signal (f) e ) generates a signal (F) corresponding to the actual force (480). Ist ), and the signal is sent to the first adder (210).

2. The method (400) according to claim 1, wherein, The signal (F) corresponding to the actual force Ist It is generated based on lookup table (230).

3. The method (400) according to claim 1 or 2, wherein, The second control signal (τ) e () is a periodic signal.

4. The method (400) according to any one of claims 1 to 3, wherein, The oscillator control signal (f) e The frequency corresponds to the inherent frequency of the electromechanical actuator (320) or the actuator system having the electromechanical actuator (320).

5. The method (400) according to claim 4, wherein, The phase difference signal corresponds to a phase difference of 90°.

6. The method (400) according to any one of claims 1 to 5, wherein, The electromechanical actuator (320) is part of the electromechanical vehicle brake, and the force is a braking force.

7. A computer program comprising instructions that, when executed by a computer (160), cause the computer to perform the method (400) according to any one of claims 1 to 6.

8. A computer-readable storage medium (160-11), on which the computer program according to claim 7 is stored.

9. A vehicle braking system (100) having one or more electromechanical brakes (120-1, 120-2, 140-1, 140-2) and one or more control devices (160) designed to perform regulation according to the method of claim 6.

10. The vehicle braking system (100) according to claim 9, the vehicle braking system having a central control device (160) designed to regulate one or all of the electromechanical brakes (120-1, 120-2, 140-1, 140-2).

11. A vehicle (10) having a vehicle braking system (100) according to claim 9 or 10.

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