Estimation of the temperature of the electric motor of a vehicle brake actuator and control of the motor

Abstract

FIG3 depicts a wheel control device (4). The control device (4) is configured to determine a first correction coefficient (α1) for the temperature (T) of the motor according to the ratio of the angular velocity (ω) of the motor to the power supply intensity (i) of the motor in dependence on the power supply voltage (u) of the motor. The control device (4) is configured to determine a second correction coefficient (α2) for the temperature (T) of the motor according to the ratio of the ohmic resistance (R) of the motor to the constant (K) of the motor in dependence on the temperature (T) of the motor.

Description

Technical Field

[0001] The present invention relates to vehicle brakes and more particularly to controlling an electromechanical brake actuator as a function of the temperature of the actuator's motor. Background Art

[0002] A floating caliper brake includes an electromechanical actuator connected to a caliper. The electromechanical actuator includes an electric motor.

[0003] Some of these brakes are equipped with a temperature sensor. Then, the motor of the actuator is controlled taking into account the temperature of the motor. Then, the braking force applied by the brake tends to be more precise.

[0004] There is a need to limit the effect of motor temperature on brake performance, particularly in the absence of a brake temperature sensor. Summary of the invention

[0005] In this respect, the invention relates to a method for controlling a vehicle brake, the brake comprising an electromechanical actuator comprising an electric motor. The control method comprises controlling the actuator as a function of an estimated temperature of the motor, the temperature of the motor being estimated as a function of a motor constant and an ohmic resistance of the motor.

[0006] According to the invention, a method for controlling a brake comprises the step of determining a first temperature correction coefficient of the motor based on a first function representing a ratio of the angular velocity of the motor to the supply current of the motor as a function of the supply voltage of the motor.

[0007] Additionally or alternatively, the method for controlling a brake comprises the step of determining a second temperature correction coefficient for the motor based on a second function representing a ratio of the ohmic resistance of the motor to a motor constant as a function of the temperature of the motor.

[0008] By estimating the temperature of the electric motor, the influence of the temperature of the motor on the braking performance is limited, including in the absence of a brake temperature sensor, with the first temperature correction factor and / or the second temperature correction factor. The electric motor, and more generally the actuator, is controlled taking into account the estimated temperature of the electric motor. By taking into account the temperature of the electric motor, in particular by means of the first temperature correction factor and / or the second temperature correction factor, the braking force applied by the brake is also estimated more accurately.

[0009] Thus, the mass, power and cost of the electromechanical brake actuator can be limited.By more accurately controlling the braking force applied by the brake, braking tends to be more effective.

[0010] The present invention can optionally include one or more of the following features, whether or not these features are combined with each other.

[0011] According to a particular embodiment, the control method comprises controlling the motor so that the brake applies a braking force according to a braking set point, the braking force applied by the brake being estimated according to a temperature of the motor.

[0012] According to a particular embodiment, the braking force applied by the brake is estimated by means of the first correction factor and / or the second correction factor.

[0013] According to certain embodiments, the first function and / or the second function are configured to be linear.

[0014] According to a particular embodiment, the motor constant and / or the ohmic resistance of the motor is estimated from the supply voltage of the motor and the supply current of the motor.

[0015] The invention also relates to a device for controlling a vehicle brake, the brake comprising an electromechanical actuator, the electromechanical actuator comprising an electric motor. The control device is configured to control the electromechanical actuator as a function of the temperature of the electric motor of the actuator, the temperature of the motor being estimated as a function of a motor constant and the ohmic resistance of the motor.

[0016] According to the invention, the control device is configured to determine a first temperature correction coefficient for the motor based on a first function representing a ratio of the angular velocity of the motor to the power supply current of the motor as a function of the power supply voltage of the motor.

[0017] Additionally or alternatively, the control device is configured to determine a second temperature correction coefficient for the motor based on a second function representing a function of a ratio of the ohmic resistance of the motor to a motor constant as a function of the temperature of the motor.

[0018] The invention also relates to a motor vehicle brake comprising an electromechanical actuator and a control device as defined above. The control device is configured to control the actuator of the brake.

[0019] According to a particular embodiment, the control device is configured to control the motor such that the brake applies a braking force according to a brake set point, the braking force applied by the brake being estimated according to a temperature of the motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention will be better understood by reading the description of the exemplary embodiments with reference to the accompanying drawings, in which:

[0021] - Figure 1 is a partial schematic diagram of a vehicle brake according to a first embodiment of the present invention;

[0022] - Figure 2 is a partial schematic diagram of an actuator and an actuator control device according to a first embodiment of the present invention;

[0023] - Figure 3 is a partial schematic diagram of an actuator control device according to a first embodiment;

[0024] - Figure 4 is a partial schematic diagram of the ratio of the angular velocity of the motor to the current supplied to the motor as a function of the supply voltage of the motor;

[0025] - Figure 5 is a partial schematic diagram of the ratio of the ohmic resistance of the motor to the motor constant as a function of the temperature of the motor;

[0026] - Figure 6 A method for controlling a brake according to a first embodiment is shown. DETAILED DESCRIPTION

[0027] Identical, similar or equivalent components in different figures have the same reference signs to facilitate transition from one figure to another.

[0028] Figure 1 A disc brake 1 for a motor vehicle is shown. The disc brake 1 comprises a caliper 2, advantageously of the floating type, a yoke (not shown), an electromechanical actuator 3, two pads (not shown) and a disc 12. The brake 1 also comprises a piston 11 and means 4 for controlling the actuator. In particular, the brake 1 is a parking brake.

[0029] In a first variant embodiment, the brake according to the invention comprises a hydraulic actuator (usually a cylinder / piston) for service braking and an electromechanical actuator for parking and / or emergency braking. In a second variant embodiment, all brake actuators are of the electric or electromechanical type. Advantageously, a single electromechanical actuator provides service, parking and / or emergency braking.

[0030] A piston 11 is housed in the caliper 2. The piston can translate relative to the caliper 2 in order to bring closer together a plurality of pads (not shown) that clamp the disc 12 during braking.

[0031] The electromechanical actuator 3 is connected to the yoke 2. The electromechanical actuator 3 includes an electric motor 31, a transmission 32, and a housing 34 accommodating the motor 31 and the transmission 32.

[0032] The operation of the motor 31 is described by the following five equations:

[0033] (1)

[0034] (2)

[0035] (3)M L (t) = M F +MC (t)

[0036] (4)

[0037] (5)u(t)=Ri(t)+Kω(t)

[0038] In these equations, u represents the motor supply voltage, i represents the motor supply current, L represents the motor inductance, R represents the motor ohmic resistance, K represents the motor constant, J represents the motor moment of inertia, ω represents the motor angular velocity, and M L Indicates the motor output torque, M C Indicates the motor load torque, M F represents the motor friction torque, and S represents the displacement of the piston.

[0039] The transmission device 32 is connected to the piston 11. The transmission device includes a plurality of motion transmission elements, such as gears. When the transmission device 32 is driven by the motor 31, the transmission device is configured to displace the piston 11.

[0040] The control device 4 comprises at least one control unit. The control device 4 controls the operation of the motor 31, for example, via a data transmission network, a wireless connection or a power cable. The control device 4 is suitable for the type of motor 31 used (a motor with brushes and / or a motor without brushes, etc.). Advantageously, the control device comprises a switching device, which comprises, for example, a power transistor, etc., which is advantageously controlled by a digital computer.

[0041] In the embodiment shown, each control unit is located outside the housing 34 of the actuator. Each control unit comprises, for example, a computing unit. The computing unit is formed, for example, by a computer of a vehicle stabilization system (for example known under the trademark "ESP"), a central computer dedicated to braking, a digital computer shared with other functions of the vehicle and / or a computer integrated in the brake 1.

[0042] Reference Figure 2 and Figure 3 The control device 4 includes a device 5 for estimating the resistance of the motor, a device 6 for estimating the motor constant, a device 7 for estimating the temperature of the motor, a device 8 for estimating the angular velocity of the motor, a device 9 for estimating the output torque of the motor, a device 20 for estimating the displacement of the piston and a device 22 for estimating the braking force.

[0043] Reference Figure 2 and Figure 3 The control device 4 is configured to control the electromechanical actuator 3 as a function of the temperature T of the electric motor of the actuator estimated by the device 7 for estimating the temperature.

[0044] The temperature estimation device 7 is configured to estimate the temperature T of the motor 31 based on the motor constant K and the motor ohmic resistance R. In particular, when the motor temperature T rises, the motor constant K tends to decrease. When the motor temperature T increases, the motor ohmic resistance R tends to increase.

[0045] Furthermore, the constant K and the ohmic resistance R of the motor tend to change as the electric motor 31 ages. The resistance estimation device 5 is configured to estimate the ohmic resistance R of the electric motor based on the motor supply voltage u and the motor supply current i. The device 6 for estimating the motor constant is configured to estimate the constant K of the electric motor based on the motor supply voltage u and the motor supply current i. When the constant K and the ohmic resistance of the motor are determined, the value of the moment of inertia J of the motor is known.

[0046] For example, through the above five equations representing the behavior of the electric motor 31, the constant K of the motor and the ohmic resistance R of the motor are estimated in two steps using the estimation method disclosed in the patent application US2016 / 0103430.

[0047] In parallel or after the temperature T of the motor has been estimated, the angular velocity estimation means 8 estimates the angular velocity ω of the motor. The means 9 for estimating the motor output torque estimates the motor output torque M L For example, if the ohmic resistance R, the motor constant K, the motor power supply voltage u, and the motor power supply current i are known, the above equations (2) and (5) are used to estimate the motor angular velocity ω and the motor output torque M L .

[0048] Once the motor angular velocity ω and the motor output torque M are estimated L , the control device 4 establishes a first temperature correction coefficient α1 of the motor and a second temperature correction coefficient α2 of the motor.

[0049] More specifically refer to Figure 4 , a first correction coefficient α1 is established according to a first function f1. The first function f1 is configured to be substantially linear. The first function relates to a function of the ratio of the motor angular velocity ω to the current i supplied to the motor 31 as a function of the power supply voltage u of the motor. Considering the effect of the temperature of the motor 31 on the braking force F applied by the brake 1 S The first correction coefficient α1 is then used to estimate the braking force F S .

[0050] More specifically refer to Figure 5, a second correction coefficient α2 is established according to a second function f2. The second function f2 is configured to be substantially linear. The second function relates to a function of the ratio of the ohmic resistance R of the motor to the constant K of the motor as a function of the temperature T of the motor. Considering the effect of the temperature T of the motor 31 on the braking force F applied by the brake 1 S The second correction coefficient α2 is then used to estimate the braking force F S .

[0051] Refer again Figure 3 The device 20 for estimating the displacement of the piston is configured to estimate the displacement S of the piston based on the angular velocity ω of the motor. The displacement S of the piston depends on the reduction ratio of the transmission device 32 and the reduction ratio of the transmission element accommodated in the caliper 2. Since the displacement S of the piston is almost independent of the temperature T of the motor, in the embodiment shown, the displacement S of the piston is estimated without a correction coefficient related to the temperature of the motor (such as the first correction coefficient α1 or the second correction coefficient α2). Such a device 20 for estimating the displacement of the piston is known per se.

[0052] The estimation device 22 for estimating the braking force is configured to estimate the braking force F applied by the brake 1 on the corresponding wheel. S In the embodiment shown, the braking force F S corresponds to the clamping force exerted by the pad (not shown) on the disk 12. According to the angular velocity ω of the motor, the output torque M of the motor L and the motor temperature T to estimate the braking force F S In particular, the temperature T of the motor is taken into account by the first correction coefficient α1 and the second correction coefficient α2 to estimate the braking force F S .

[0053] Reference Figure 3 and Figure 6 A method for controlling a brake 1 is shown. The control method 100 is executed by the above-mentioned control device 4. In step 135, the control method 100 aims at controlling the operation of the electric motor 31 of the actuator as a function of the estimated temperature T of the motor.

[0054] The control method 100 comprises an initial step 101 of determining a supply voltage u of the motor 31, a supply current i of the motor and a moment of inertia J of the motor. The moment of inertia J of the motor is known, for example, from the specifications of the electric motor 31. The supply voltage u and the supply current i are measured at different times, for example at regular time intervals.

[0055] The control method 100 continues with step 103, in which the motor constant K is estimated based on the measured motor supply voltage u and motor supply current i. In parallel, the control method 100 includes step 105 of estimating the motor ohmic resistance R based on the motor supply voltage u and motor supply current i.

[0056] Then, the control method 100 comprises a step 107 in which the temperature T of the electric motor is estimated by means of the temperature estimation device 7 from the ohmic resistance R of the motor and the constant K. In this context, the step 107 of estimating the temperature T is also referred to as a method for estimating the temperature T of the motor.

[0057] The control method 100 comprises a step 109, in which the angular velocity ω of the motor is estimated according to the power supply voltage u of the motor, the power supply current i of the motor, the inertia moment J of the motor, the ohmic resistance R of the motor and the constant K of the motor. In parallel, the control method 100 comprises a step 111, in which the output torque M of the motor is estimated according to the power supply voltage u of the motor, the power supply current i of the motor, the inertia moment J of the motor, the ohmic resistance R of the motor and the constant K of the motor. L .

[0058] The control method 100 comprises a step 131, in which the displacement S of the piston is estimated according to the angular velocity ω of the motor by means of the device for estimating the displacement of the piston 20. In parallel, the control method 100 comprises a step 133, in which the braking force estimation device 22 is used to estimate the displacement S of the piston according to the angular velocity ω of the motor, the output torque M of the motor L and the motor temperature T to estimate the braking force F S .

[0059] The control method 100 ends with step 135 for controlling the operation of the motor 31. In particular, the control device 4 controls the motor supply voltage u and the motor supply current i. Thus, the motor 31 rotates at an angular velocity ω and generates an output torque M L , so that the piston 11 is displaced by the set point value S, and the brake 1 applies the braking force F according to the braking set point S .

[0060] Of course, those skilled in the art may make various modifications to the invention just described without departing from the described scope of the invention.

[0061] In an exemplary embodiment not shown, the brake 1 is a drum brake which comprises an electromechanical actuator 3 and a control device 4 for the actuator.

[0062] In another embodiment not shown, the brake 1 is a fixed caliper brake instead of a floating caliper brake.

[0063] The displacement s of the piston 11 can be estimated by the control device 4 based on the temperature T of the motor 31 .

[0064] Alternatively or additionally, the constant K of the motor, the ohmic resistance R of the motor and / or the angular velocity ω of the motor are measured instead of being estimated from the supply voltage u and the supply current i of the motor.

[0065] The control device 4 can control the operation of the motor 31 by means of other parameters, for example by taking greater account of the wear and / or friction of the motor 31 or the transmission 32 .

[0066] In addition to the first correction coefficient α1 and the second correction coefficient α2 , other types of correction coefficients may be used.

[0067] The first function f1 and the second function f2 may be configured in a nonlinear manner (eg, polynomial) to be more accurate.

[0068] Terms referring to the accompanying drawings

[0069] 1: Disc brake

[0070] 2: Calipers

[0071] 3: Electromechanical actuator

[0072] 4: Control device

[0073] 5: Device for estimating motor resistance

[0074] 6: Device for estimating motor constants

[0075] 8: Device for estimating the angular velocity of the motor

[0076] 9: Device for estimating motor torque

[0077] 11: Piston

[0078] 12: Plate

[0079] 20: Device for estimating the displacement of a piston

[0080] 22: Device for estimating braking force

[0081] 31: Electric Motor

[0082] 32: Transmission

[0083] 34: Actuator housing

[0084] T: Temperature of the electric motor

[0085] K: Motor constant

[0086] R: Motor resistance

[0087] L: Motor inductance

[0088] u: motor power supply voltage

[0089] i: Motor power supply current

[0090] J: Moment of inertia of the motor

[0091] ω: angular velocity of the motor

[0092] M L : Motor output torque

[0093] M C : Motor load torque

[0094] M F : Motor friction torque

[0095] S: Piston displacement

[0096] F S : Braking force applied by the brake

[0097] f1: first function

[0098] α1: The first temperature correction coefficient of the motor

[0099] f2: second function

[0100] α2: Second temperature correction coefficient of the motor

Claims

1. A control method for controlling a vehicle brake (1), the brake (1) comprising an electromechanical actuator (3), the electromechanical actuator comprising an electric motor (31), the control method comprising: controlling the electromechanical actuator (3) as a function of the temperature (T) of the electric motor, wherein the temperature (T) of the electric motor is estimated as a function of a motor constant (K) and an ohmic resistance (R) of the electric motor, The control method for controlling the brake (1) comprises a step of determining (121) a first temperature correction coefficient (α1) of the electric motor based on a first function (f1), the first function representing a function of a ratio of an angular velocity (ω) of the electric motor to a power supply current (i) of the electric motor as a function of a power supply voltage (u) of the electric motor, wherein the first temperature correction coefficient (α1) is used to estimate a braking force (F S ), and / or The control method for controlling the brake (1) comprises the step of determining (123) a second temperature correction coefficient (α2) of the electric motor based on a second function (f2), the second function representing a function of a ratio of an ohmic resistance (R) of the electric motor to the motor constant (K) as a function of a temperature (T) of the electric motor, wherein the second temperature correction coefficient (α2) is used to estimate a braking force (F S ); The control method for controlling the brake (1) comprises the following steps: controlling the operation of the electric motor (31) by controlling the power supply voltage (u) and the power supply current (i) of the electric motor (31), so that the electric motor (31) rotates at an angular velocity (ω) and generates an output torque (M L ), so that the piston (11) is displaced by a set point value (S), and the brake (1) applies a braking force according to the brake set point.

2. The control method according to claim 1, wherein: The first function (f1) and / or the second function (f2) are configured to be linear.

3. The control method according to claim 1, wherein: The motor constant (K) and / or the ohmic resistance (R) of the electric motor are estimated based on the supply voltage (u) of the electric motor and the supply current (i) of the electric motor.

4. A control device (4) for controlling a vehicle brake (1), the brake (1) comprising an electromechanical actuator (3), the electromechanical actuator comprising an electric motor (31), in, The control device (4) is configured to control the electromechanical actuator (3) as a function of a temperature (T) of an electric motor of the electromechanical actuator, wherein the temperature (T) of the electric motor is estimated as a function of a motor constant (K) and an ohmic resistance (R) of the electric motor, The invention is characterized in that the control device (4) is configured to determine a first temperature correction coefficient (α1) of the electric motor based on a first function (f1), the first function representing a function of a ratio of an angular velocity (ω) of the electric motor to a power supply current (i) of the electric motor as a function of a power supply voltage (u) of the electric motor, and the control device is configured to estimate a braking force (F) using the first temperature correction coefficient (α1) in consideration of a temperature (T) of the electric motor (31). S ), and / or The control device (4) is configured to determine a second temperature correction coefficient (α2) of the electric motor based on a second function (f2), the second function representing a function of a ratio of an ohmic resistance (R) of the electric motor to the motor constant (K) as a function of a temperature (T) of the electric motor, and the control device is configured to estimate a braking force (F) using the second temperature correction coefficient (α2) in consideration of the temperature (T) of the electric motor (31). S ); The control device (4) is configured to control the operation of the electric motor (31) by controlling the power supply voltage (u) and the power supply current (i) of the electric motor (31), so that the electric motor (31) rotates at an angular velocity (ω) and generates an output torque (M L ), so that the piston (11) is displaced by a set point value (S), and the brake (1) applies a braking force according to the brake set point.

5. The control device (4) according to claim 4, wherein: The first function (f1) and / or the second function (f2) are configured to be linear.

6. The control device (4) according to claim 4, wherein: The motor constant (K) and / or the ohmic resistance (R) of the electric motor are estimated based on the supply voltage (u) of the electric motor and the supply current (i) of the electric motor.

7. A brake (1) for a motor vehicle, comprising an electromechanical actuator (3) and a control device (4) according to claim 4, wherein: The control device (4) is configured to control the electromechanical actuator (3) of the brake (1).

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