Method for controlling an electromechanical brake system

Abstract

To provide a method for controlling an electromechanical parking brake.SOLUTION: The invention provides a method of controlling an electromechanical brake system. The method comprises measuring a voltage of a motor, measuring a current of the motor, and estimating a position of a component of the electromechanical brake system based on the voltage and the current. The method comprises estimating a force imposed by the component based on the voltage and the current, and estimating a hydraulic pressure associated with a hydraulic brake system. In an apply operation, the force of the component is corrected based on the hydraulic pressure. In a release operation, the position of the component is corrected based on the hydraulic pressure.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Patent No. 63 / 416,221, filed October 14, 2022, which is incorporated by reference in its entirety for all purposes.

[0002] The present teachings generally relate to a method for controlling an electromechanical brake system, which may take into account the hydraulic pressure of a hydraulic brake system. [Background technology]

[0003] Many vehicles are manufactured with a parking pole in the transmission or driveline assembly. During parking maneuvers, the pole provides a backup in case the parking brake experiences a failure or degradation condition, causing the applied load to fall below that required to keep the vehicle stationary. In these types of vehicles, the control of the parking brake is coupled; that is, a single controller controls both the driver's and passenger's side of the vehicle. Coupled control typically does not account for failures or degradation conditions, as the system can rely on the pole. Thus, in the event of, for example, a controller or sensor failure, the pole can be relied upon to keep the vehicle stationary. If the vehicle is configured without a pole, fault redundancy must be addressed.

[0004] In controlling the parking brake, the actuator mechanism may be controlled to ensure that the applied load is commensurate with the grade on which the vehicle is located. Applying a load that exceeds the grade requirement may shorten the service life of the brake system. A dedicated sensor may be used to determine the grade. However, this solution requires extra cost and manufacturing complexity, as well as impacting the weight and packaging space of the vehicle. Existing sensor inputs in the vehicle may also be used. However, if the sensor input is unavailable and / or the brake system does not operate correctly or at all, failure redundancy must be established to ensure accurate system operation.

[0005] Some vehicle braking systems use both an electromechanical system (an "electromechanical parking brake system" or "EPB system") and a hydraulic system (a "hydraulic service brake system" or "HSB system") to act on a piston that moves one or more brake pads against a brake disc ("rotor") to apply a braking load. Typically, the electromechanical system is used during parking brake operation and the hydraulic system is used during service brake operation, although either or both may be used during either braking operation.

[0006] Load overlap from electromechanical and hydraulic systems can occur when operations overlap. For example, a driver parking a vehicle may apply the service brake to bring the vehicle to a standstill and then apply the parking brake while the service brake is active. As another example, a driver preparing to move out of a parked position may apply the service brake before releasing the parking brake. As yet another example, an electromechanical or hydraulic support system may supplement the operation of the electromechanical or hydraulic primary system in the event of a primary system failure. One concern with load overlap is the risk of exceeding the maximum recommended load on the brake system, shortening its useful life. Another concern is energy efficiency. Operating an electromechanical brake system at the high torque associated with exceeding the maximum load consumes energy unnecessarily.

[0007] Brake systems typically operate with a running clearance between the brake pads and brake discs when neither the electromechanical nor hydraulic systems are operational. The running clearance ensures that the vehicle's wheels can rotate freely and there is no frictional engagement between the brake pads and brake discs. When the operations of the electromechanical and hydraulic brake systems overlap, the running clearance can become misaligned because operation of the hydraulic system causes the perceived or estimated position of the electromechanical actuator to deviate from its actual position due to deflections induced by the hydraulic brake system.

[0008] Sensors can be used to determine the position of the electromechanical actuator. However, additional sensors increase cost and manufacturing complexity, as well as affect vehicle weight and packaging space. It has been proposed to consider hydraulic pressure during the operation of an electromechanical brake system. However, existing methods vary in which sensor inputs are used. Fault redundancy also remains a concern. Some existing methods use open-loop control, in which no feedback is provided to correct the estimated actuator position or applied force. However, due to the unpredictable nature of the influence of the hydraulic brake system on the operation of the electromechanical brake system, open-loop control can result in inaccurate operation of the electromechanical brake system. U.S. Pat. No. 10,137,878, incorporated herein by reference in its entirety for all purposes, describes a closed-loop control method in which the position and / or force of the electromechanical brake system are estimated based on voltage and / or current measurements. However, the above patent document does not propose considering the pressure applied by the hydraulic brake system.

[0009] It is desirable to provide a method for controlling electromechanical braking systems used in vehicles with or without parking poles.

[0010] It would be desirable to provide a method for controlling an electromechanical braking system that takes vehicle gradient into account.

[0011] It would be desirable to provide a method for controlling an electromechanical braking system using existing sensor inputs, eliminating the need to add additional sensors to the vehicle.

[0012] It is desirable to provide a method for controlling an electromechanical braking system that provides failure redundancy.

[0013] It would be desirable to provide a method for controlling an electromechanical braking system in a decoupled manner, with separate controllers controlling the driver's and passenger's sides of the vehicle.

[0014] It would be desirable to provide a method of controlling an electromechanical braking system in which fault or deterioration conditions are communicated between separate controllers associated with both the driver's and passenger's sides of the vehicle.

[0015] It would be desirable to provide a method of controlling an electromechanical braking system to avoid applying loads in excess of requirements for a particular grade condition.

[0016] It would be desirable to provide a method for controlling an electromechanical braking system in a closed loop manner such that feedback is taken into account in tuning the system.

[0017] It would be desirable to provide a method for controlling an electromechanical braking system that avoids applying more than the maximum load to the brake pads.

[0018] It is desirable to provide a method for controlling an electromechanical braking system that takes into account the hydraulic pressure in the hydraulic braking system.

[0019] It is desirable to provide a method for controlling an electromechanical braking system to maintain a running clearance between the brake pads and the brake disc. Summary of the Invention

[0020] The present disclosure relates to a method of controlling an electromechanical braking system that may address at least a portion of the needs identified above. The method may comprise measuring a voltage of a motor, measuring a current of the motor, and estimating a position of a component of the electromechanical braking system based on the voltage and current.

[0021] The method may comprise estimating a force exerted by a component based on the voltage and current and estimating a hydraulic pressure associated with the hydraulic brake system.

[0022] In application operations, component forces can be compensated for based on hydraulic pressure.

[0023] In the release operation, the position of the component can be corrected based on the hydraulic pressure.

[0024] The oil pressure may be estimated from a sensor input, which may be determined based on a logic table, which may take into account faults or degradation conditions.

[0025] The hydraulic pressure may be estimated from a first pressure associated with the left wheel cylinder, a second pressure associated with the right wheel cylinder, a third pressure associated with the master cylinder, or any combination thereof. The first, second, and third pressures may be obtained from respective pressure sensors associated with the left wheel cylinder, the right wheel cylinder, and / or the master cylinder. The first, second, and third pressures may be estimated from other sensor inputs.

[0026] If both a first pressure sensed in the left wheel cylinder and a second pressure sensed in the right wheel cylinder are available, the estimated oil pressure may be the average of both.

[0027] If only one of the first pressure sensed in the left wheel cylinder and the second pressure sensed in the right wheel cylinder is available, the estimated oil pressure may be the available one of the first pressure or the second pressure.

[0028] If neither the first pressure sensed at the left wheel cylinder nor the second pressure sensed at the right wheel cylinder is available, the estimated oil pressure may be the third pressure sensed at the master cylinder.

[0029] If none of the first pressure sensed in the left wheel cylinder, the second pressure sensed in the right wheel cylinder, and the third pressure sensed in the master cylinder are available, the estimated oil pressure may be set to a default value.

[0030] The component may be a spindle nut, a spindle, a component of a motor assembly, or any combination thereof.

[0031] The method may further include rotating the spindle by the motor about the axis in a first direction such that the spindle nut moves the one or more brake pads against the braking surface, and rotating the spindle by the motor about the axis in a second direction such that the one or more brake pads move away from the braking surface.

[0032] In an apply operation, the compensation may reduce and / or prevent damage caused by the combined loads of the electromechanical and hydraulic brake systems. In a release operation, the compensation may reduce and / or prevent damage caused by residual caliper drag.

[0033] The control of the electromechanical braking system may be closed loop.

[0034] The method may further comprise estimating a vehicle gradient. The method may further comprise adjusting a force applied by a component of the electromechanical braking system based on the vehicle gradient.

[0035] The method may further comprise obtaining a longitudinal acceleration of the vehicle. The vehicle gradient may be estimated based on the longitudinal acceleration.

[0036] If a fault or degradation condition occurs, the force may be set to a default value. The fault or degradation condition may include longitudinal acceleration not being available, longitudinal acceleration exceeding a maximum value, longitudinal acceleration being below a minimum value, or any combination thereof.

[0037] The method may further comprise obtaining a wheel speed, which may determine whether the vehicle is in a static or dynamic state, and the vehicle gradient may be estimated only when the vehicle is in a static state.

[0038] The wheel speed may be the minimum of a maximum wheel speed of a first diagonal wheel set and a maximum wheel speed of a second diagonal wheel set. The first diagonal wheel set may include a left front wheel and a right rear wheel. The second diagonal wheel set may include a right front wheel and a left rear wheel.

[0039] If a failure or deterioration condition occurs with respect to the left or right front wheel, the wheel speed of the corresponding rear wheel in the first or second diagonal wheel set may be considered in determining the minimum value.

[0040] If a failure or deterioration condition occurs for both the left and right front wheels, the wheel speeds may be set to default values.

[0041] If a failure or deterioration condition occurs with either the left or right rear wheel, the wheel speed may be set to a default value.

[0042] If the wheel speed is below the static threshold for a predetermined period of time, the vehicle may be assumed to be in a static state. If the wheel speed is above the dynamic threshold for a predetermined period of time, the vehicle may be assumed to be in a dynamic state.

[0043] A force may be determined based on the vehicle gradient.

[0044] The force may be determined by the vehicle grade within a discrete range of vehicle grade and / or the force may be modeled as a function of vehicle grade, where the function may be linear, non-linear, or piecewise.

[0045] The method may further include detecting, by the first controller, a fault or degraded condition associated with a first brake caliper to which the first controller is assigned. The method may further include communicating, by the first controller, the fault or degraded condition to a second controller assigned to a second brake caliper. The method may further include setting a force associated with the second brake caliper to a default force.

[0046] The first controller and the first brake caliper may be located on the passenger side of the vehicle and the second controller and the second brake caliper may be located on the driver's side of the vehicle, or vice versa. [Brief explanation of the drawings]

[0047] [Figure 1] 1 illustrates a fault redundancy scheme in accordance with the present teachings. [Figure 2A] 1 shows a graph of gradient ranges according to the present teachings. [Figure 2B] 10 shows a graph of target load as a function of gradient in accordance with the present teachings. [Figure 3A] 1 illustrates a graph of parking brake and service brake operating parameters as a function of time in accordance with the present teachings. [Figure 3B] 3B shows an enlarged view of a portion of the graph of FIG. 3A. [Figure 4] 10 shows a graph illustrating clamping force applied by a parking brake as a function of spindle nut position and oil pressure in accordance with the present teachings. [Figure 5] 1 illustrates a fault redundancy scheme in accordance with the present teachings. [Figure 6A] 1 illustrates a flow diagram or control model for linear time-varying estimation (LTV) in accordance with the present teachings. [Figure 6B] 6B shows a flow diagram of the subcomponents of the state estimation model of the LTV of FIG. 6A. DETAILED DESCRIPTION OF THE INVENTION

[0048] The disclosed methods may be utilized with a braking system. The braking system may function to slow, stop, limit, and / or prevent vehicle movement. The braking system may function to apply a load that slows, stops, limit, and / or prevent rotation of the brake disc, slows, stops, limit, and / or prevent vehicle movement, or both. The load may be applied during a parking brake operation that limits or prevents rotation of the brake disc when the vehicle is in a stopped or parked position, limits or prevents vehicle movement, or both.

[0049] The braking system may be any system or assembly that performs the functions described above. For example, the braking system may be an opposed braking system (i.e., fixed caliper braking system), a floating brake system (i.e., floating caliper), a parking brake assembly, a drum-in-hat braking system, or a combination thereof.

[0050] The brake system may be used in any vehicle to perform the functions described above. For example, the brake assembly may be used in any light vehicle (e.g., car, truck, SUV, etc.) or any heavy vehicle (e.g., large truck, van, SUV, etc.).

[0051] The braking system may include one or more brake calipers, which may function to house, house, and / or provide mounting and functionality for any of the components of an electromechanical braking system, a hydraulic braking system, or both.

[0052] The brake caliper may function to provide movement of one or more brake pads relative to the brake disc. The brake caliper may move during an application operation (i.e., a floating caliper) or the brake caliper may be fixed to prevent movement of the brake caliper during an application operation (i.e., a fixed caliper). The brake caliper may include one or more support brackets for engaging the one or more brake pads. The one or more support brackets may be positioned around the brake disc such that one or more brake pads are located on the inboard side of the brake disc and one or more brake pads are located on the outboard side of the brake disc.

[0053] Inboard may refer to the side of the brake disc facing the longitudinal centerline of the vehicle. Outboard may refer to the side of the brake disc facing away from the longitudinal centerline of the vehicle.

[0054] An apply operation may refer to moving one or more brake pads towards the brake disc, and therefore, an apply direction may refer to a direction towards the brake disc. A release operation may refer to moving one or more brake pads away from the brake disc, and therefore, a release direction may refer to a direction away from the brake disc.

[0055] The brake disc may cooperate with one or more elements of the brake system during apply and / or release operations. The brake disc may be at least partially enclosed by a brake caliper. The friction material of one or more brake pads may face an inboard side of the brake disc, and the friction material of one or more brake pads may face an outboard side of the brake disc.

[0056] During an application operation, the friction material of one or more brake pads can be moved into contact with one or more sides of the brake disc to slow, stop, and / or restrict the brake disc, the vehicle, or both. During an application operation, the friction material of one or more brake pads can be moved into contact with one or more sides of the brake disc to restrict a stopped or parked vehicle or brake disc, respectively, from moving or rotating.

[0057] One or more brake pads may cooperate with one or more elements of a brake assembly in an apply operation. The apply operation may relate to a service brake or a parking brake. For example, in an apply operation, the friction material of one or more brake pads is moved into contact with a given surface, such as one or more sides of a brake disc. The one or more brake pads may move in unison, individually, sequentially, or a combination thereof.

[0058] In a release operation, one or more brake pads may move. For example, in a release operation, the friction material of one or more brake pads may be moved away from and / or out of contact with a surface, such as one or more sides of a brake disc. The one or more brake pads may move in unison, individually, sequentially, or a combination thereof.

[0059] The braking system may include one or more piston assemblies that may function to move one or more brake pads toward and / or away from a surface in an apply and / or release operation, respectively, and that may function to transfer or convert rotational torque or force into a linear force to move one or more brake pads axially relative to a brake disc.

[0060] The one or more piston assemblies may selectively engage pressure plates of one or more brake pads, for example, during application, the one or more piston assemblies engage one pressure plate to move friction material disposed on the pressure plate toward the brake disc.

[0061] Each of the one or more piston assemblies may include one or more pistons, one or more spindle nuts, and one or more spindles, which may function together to perform the functions described above.

[0062] The one or more pistons may function to move the one or more brake pads against a surface during an apply or release operation. The one or more pistons may move along a piston axis toward or away from the brake pads. The one or more pistons may move in and out of corresponding piston openings or bores.

[0063] The one or more pistons may be moved toward or away from one or more brake pads via any fluid, via any mechanical device or linkage, or a combination thereof, such as a spindle nut and spindle. Preferably, during operation of the service brake, the one or more pistons are moved via pressure applied to a fluid. Preferably, during operation of the parking brake, the one or more pistons are moved via a motor gear unit connected to a linkage including the spindle nut and spindle.

[0064] The one or more spindle nuts may function to engage one or more pistons to allow movement of one or more brake pads relative to the brake disc during apply and / or release operations. The one or more spindle nuts may engage the corresponding pistons via any suitable engagement or attachment. For example, the engagement may be threaded, sliding, interference, permanent, removable, keyed, or the like, or a combination thereof.

[0065] A moving force may be applied to one or more spindle nuts (e.g., provided by a motor gear unit, a worm wheel, a spindle, an output shaft, etc.) to move one or more pistons relative to the brake pads along their respective piston axes. The one or more spindle nuts may move at least partially relative to the pistons without the pistons and / or brake pads actually moving relative to the brake disc (i.e., a gap may extend between the spindle nut and the piston pocket). In other words, the spindle nuts may be moved axially a certain distance before the nuts actually move the pistons and / or brake pads.

[0066] The one or more spindles may function to engage one or more pistons, spindle nuts, or both to allow movement of one or more brake pads relative to the brake disc. The one or more spindles may be in communication with respective worm wheels, output shafts, or both, and may cooperate with respective spindle nuts to convert rotational force received from the motor gear unit, output shaft, worm wheel, differential, etc., into linear force for moving pistons along their respective piston axes.

[0067] The one or more spindles may engage with corresponding spindle nuts via any suitable engagement or attachment to perform the functions described above. Preferably, the engagement may be a threaded engagement. To this end, each of the one or more spindle nuts may include one or more threads. The one or more spindles may rotate or translate in an apply direction to move the spindle nuts, pistons, and / or brake pads toward the brake disc. The one or more spindles may rotate or translate in a release direction to move the spindle nuts, pistons, and / or brake pads away from the brake disc. It is within the scope of this disclosure that the one or more spindles, the one or more spindle nuts, and / or the one or more pistons may be a single component and still function in the manner described above.

[0068] One or more worm wheels may be in communication with each spindle. The one or more worm wheels may function to receive and transmit rotational force or torque to the one or more spindles so that the one or more brake pads can move relative to the brake disc. The rotational force may be provided by or from a motor gear unit, a respective output shaft, a differential, or the like. The one or more worm wheels may rotate in an apply direction to move the corresponding spindle, ultimately moving the corresponding brake pad toward the brake disc. The one or more worm wheels may rotate in a release direction to move the corresponding spindle, ultimately moving the corresponding brake pad away from the brake disc.

[0069] Each worm wheel may include a flange or opening that engages with a respective spindle. The engagement may be any suitable engagement for performing the functions described above. Exemplary engagements may include, but are not limited to, threaded engagement, sliding engagement, interference engagement, permanent engagement, removable engagement, keyed engagement, magnetic engagement, etc., or combinations thereof. Each worm wheel may include features for engaging a respective output shaft, worm, motor gear unit, differential, or combinations thereof.

[0070] The one or more output shafts may function to provide or transmit rotational force or torque. Specifically, the one or more output shafts may function to receive rotational force or torque generated or provided by the motor gear unit, the differential, or both, and transmit the rotational force or torque to a respective piston assembly, a worm wheel, or both. The one or more output shafts may include any suitable engagement to transmit the rotational force or torque to a respective piston assembly, a worm wheel, or both. For example, the one or more output shafts may include one or more worms and / or teeth that may engage with a corresponding worm wheel.

[0071] The output shaft(s) may include one or more bearings, counterweights, or both to assist in rotation (i.e., to create a low-friction device). The bearing(s) may also serve to connect and support the respective output gear to a brake caliper or housing.

[0072] The one or more output shafts may ultimately be rotated by the one or more motors and / or motor gear units. The one or more linkages may transfer torque generated by the one or more motors and / or motor gear units to the one or more output shafts.

[0073] The one or more motor gear units may be any device or combination of devices operable to generate or provide a force or torque suitable for the apply and / or release operations. For example, the one or more motor gear units may include a DC motor, a series-wound motor, a shunt-wound motor, a compound-wound motor, a separately excited motor, a servo motor, or a permanent magnet motor.

[0074] The one or more motor gear units may include one or more gears that may function to transmit, increase, decrease, or a combination thereof, any power or torque generated by the motor.

[0075] The one or more motor gear units may be located within a housing, which may be integrally formed with the brake caliper or removably attached to the brake caliper.

[0076] The one or more motor gear units may directly or indirectly (i.e., via one or more linkages, piston assemblies, etc.) move one or more pistons, brake pads, or both toward and / or away from the brake disc. The one or more motor gear units may generate sufficient rotational force or torque to move one or more piston assemblies, brake pads, or both relative to the one or more brake pads. The one or more motor gear units may generate sufficient holding force to hold the one or more brake pads against the brake disc.

[0077] The method may comprise one or more of the following steps, some of which may be duplicated, eliminated, rearranged relative to other steps, combined into one or more steps, separated into two or more steps, or combinations thereof.

[0078] The method may be performed at least in part by one or more controllers. The controller may execute computer-executable instructions that direct the performance of the method. The controller may or may not be mounted on a wheel. The controller may be an existing controller of the vehicle. The existing controller may include a booster controller, an electronic stability controller, etc., or any combination thereof. Any controller used in a vehicle may be suitable for performing the method of the present teachings. The controller may be a dedicated controller for performing the method. That is, the dedicated controller may exclusively perform the method. The present disclosure provides a method for operating an electromechanical brake system. During operation of the parking brake of the electromechanical system, a load is applied to the brake disc. The load may be commensurate with the gradient (inclination) on which the vehicle is parked to ensure the vehicle remains stationary.

[0079] The method may include estimating a vehicle gradient. The vehicle gradient may be estimated when the estimated vehicle state is a static state. The vehicle gradient may be estimated based on a longitudinal acceleration and / or a wheel speed of the vehicle. The method may include obtaining a longitudinal acceleration of the vehicle. The gradient may be estimated by the following equation, where Ax is the longitudinal acceleration and G is the gravitational constant: Grade=TAN[A * SIN(Ax / G)]

[0080] The method may comprise communicating the estimated vehicle slope to one or more operational modules.

[0081] The method may include adjusting the electromechanical brake system to a first load determined by the operational module based on the estimated vehicle gradient. The first load may be determined based on the vehicle gradient.

[0082] The method may comprise obtaining a longitudinal acceleration of the vehicle. The vehicle gradient may be estimated based on the longitudinal acceleration.

[0083] In the event of a failure or degradation condition in one module, the first load may be set to a default load of another functional module. The default load may be between about 5% and about 11%, preferably between about 6% and about 10%, and more preferably between about 7% and about 9% (e.g., 8%). Fault conditions may include longitudinal acceleration not being available, longitudinal acceleration exceeding a maximum value, or longitudinal acceleration being below a minimum value.

[0084] As referred to herein, fault condition and degraded condition may be used interchangeably with respect to results achieved by the present method. Additionally, the term fault redundancy may apply to fault conditions and / or degraded conditions. That is, for example, a default load may be established upon detection of a fault condition, as well as upon detection of a degraded condition. A fault condition may refer to the unavailability of any input or operation (e.g., if an actuator is frozen, broken, etc.). As an example, a fault condition may exist if an electromechanical actuator experiences stiction. A degraded condition may refer to any input or operation that is available but does not operate correctly.

[0085] The method may include obtaining a wheel speed. The wheel speed may determine whether the vehicle is in a static or dynamic state. The vehicle gradient may be estimated only when the vehicle is in a static state. The wheel speed may be a minimum of a maximum wheel speed of a first diagonal wheel set including a left front wheel and a right rear wheel and a maximum wheel speed of a second diagonal wheel set including a right front wheel and a left rear wheel.

[0086] If a left or right front wheel fails or deteriorates, the wheel speed of the corresponding rear wheel in the first or second diagonal wheel set may be considered in determining the minimum value. If both the left and right front wheels fail or deteriorate, the wheel speed may be set to a default value. If either the left or right rear wheel fails or deteriorates, the wheel speed may be set to a default value.

[0087] If the wheel speed is below the static threshold for a predetermined period of time, the vehicle may be assumed to be in a static state. If the wheel speed is above the dynamic threshold for a predetermined period of time, the vehicle may be assumed to be in a dynamic state.

[0088] The weight values ​​may be assigned discrete gradient ranges, such that below a first threshold the first weight is set to a first range and above the first threshold the first weight is set to a second range.

[0089] The first load may be modeled as a function of the slope. The first load may have a linear, non-linear, or piecewise relationship to the slope.

[0090] The first load may be adjusted based on hydraulic pressure of the hydraulic brake system. The hydraulic pressure may impart a second load to the piston. Thus, the first load may be adjusted to account for the second load. The first load may be adjusted to avoid a superposition of the first and second loads meeting or exceeding a maximum load threshold. The first load may be adjusted to account for slack in the electromechanical brake system.

[0091] The method may include determining whether a fault or degradation condition exists. The fault or degradation condition may be associated with an electromechanical brake system. The fault or degradation condition may be detected by a controller dedicated to a brake caliper (e.g., the left brake caliper) and communicated to a controller dedicated to another brake caliper (e.g., the right brake caliper). The method may include instructing one or more non-faulty brake calipers to apply a maximum default load upon detecting a fault or degradation condition in one or more controllers and / or brake calipers. The maximum default load applied during the fault or degradation condition may be used in place of a load determined by vehicle grade, as described above.

[0092] The actuators may adjust the target load during or after the application operation is complete. During or after the first actuator completes the application operation, the second actuator may experience a failure or degradation condition. The operable actuator may then adjust the target load to a maximum default load.

[0093] The method can be used in combined and / or separated brake systems. In a combined brake system, one controller may operate two or more brake calipers (e.g., a left brake caliper and a right brake caliper). The controller may be associated with a vehicle system such as, for example, an electronic stability controller or an electronic booster controller, although controllers associated with any other vehicle system are also contemplated by the present teachings. In a separated brake system, each brake caliper is operated by a dedicated controller. The controller may be associated with a vehicle system such as, for example, an electronic stability controller and an electronic booster controller, although controllers associated with any other vehicle system are also contemplated by the present teachings.

[0094] In combined systems, parking poles are typically used for failure redundancy. That is, if one or both brake calipers, controllers, or both experience a failure or degraded condition, the parking poles can be relied upon to keep the vehicle stationary. In separated systems, parking poles may not be present because separate controllers and brake calipers can provide failure redundancy for a controller and / or brake caliper experiencing a failure or degraded condition. The present disclosure contemplates that the method may be used in combined systems with or without parking poles. The present disclosure contemplates that the method may be used in separated systems with or without parking poles.

[0095] The present disclosure provides a method for operating an electromechanical brake system without relying on position sensors to determine the position of the motor, electromechanical actuator assembly, and / or brake piston. The method may use control logic to accurately estimate and determine the position of the actuator assembly (e.g., spindle and nut), the position of the brake piston, the position of the motor, the current draw by the motor, the motor speed, the magnitude of the parking brake or clamping force, or any combination thereof, as shown and described with respect to Figures 6A and 6B. Such control logic is described in U.S. Patent No. 10,137,878 B2, which is incorporated herein by reference in its entirety for all purposes. The control logic described herein is modified by taking into account the pressures associated with the hydraulic actuator system described herein.

[0096] A parking brake system, whether a disc brake system, a drum-in-hat brake system, or both, may have control logic for accurately estimating and determining the position of an actuator assembly (e.g., spindle and nut), the position of a brake piston, the position of a motor, the current draw by the motor, the motor speed, the magnitude of a parking brake force or a clamping force, or a combination thereof. The control logic may be embedded in a controller. The controller may be an electronic control unit, a stability control unit, or the like. The controller, the control logic, or both may include a linear time-varying observer (LTV) for estimating the position of the actuator assembly, the position of the brake piston, the position of the motor, or a combination thereof. The caliper dynamics considered to estimate the position and / or force may be nonlinear. The nonlinear caliper dynamics may be linearized for a particular operating state (e.g., applying the parking brake or releasing the parking brake) based on the parking brake force estimated by feedback linearization. The linearized operating state may provide an indication of the motor load during both the parking brake apply and release operations.

[0097] The controller, control logic, LTV, or a combination thereof may be used to estimate the motor position, spindle position, nut position, actuator assembly position, motor speed, current draw by the motor, or a combination thereof. The LTV may associate, correlate, and / or determine current and voltage measurements with the estimated motor position or motor rotational angle, motor speed, current draw by the motor, or a combination thereof. The position of the actuator assembly, brake piston, or both may be accurately estimated based on the estimated motor position, which is the motor's rotational position or angle. This is because as the motor output shaft rotates, the actuator assembly and, with it, the brake piston or brake shoe move correspondingly, all of which are rigidly coupled via one or more geared or threaded connections. The displacement or movement of the actuator assembly, brake piston, or both may be related to a clamping force, which may also be referred to herein as a parking brake force.

[0098] During parking brake application in a disc brake system, as the nut moves axially toward the bottom of the piston pocket and the brake pad moves toward the braking surface or brake rotor, the parking brake force can be related to the motor position based on an appropriate regression model. For example, the model can be a first-order linear regression model, a second-order polynomial regression model, a third-order regression model, a fourth-order regression model, etc. For example, the parking brake force can be related to the motor position based on a known system stiffness, which is often modeled using a second-order polynomial regression. During parking brake application in a drum-in-hat brake system with an internal compliance spring, the parking brake force can be related to the motor position based on a regression model such as a piecewise representation or a lookup table. In either case, a known system stiffness needs to be defined and analytically represented to relate the position of the motor, actuator, and / or brake piston to the clamping or parking brake force.

[0099] One or more models or subcomponents may define the LTV. The one or more subcomponents may include a harness subcomponent, a state estimation subcomponent, a force estimation subcomponent, and a feedback linearization subcomponent. It is understood that one or more of the above-mentioned subcomponents may be combined and / or cascaded. That is, for example, a force estimation subcomponent may be cascaded to a state estimation subcomponent and defined as a single subcomponent.

[0100] The present disclosure provides a method for operating an electromechanical brake system (e.g., a parking brake or "EPB") that can be operated to modulate based on the hydraulic pressure of a hydraulic brake system (e.g., a service brake or "HSB"). The modulation can be in the apply direction and / or the release direction. Such modulation can be based on empirical and / or theoretical models. An exemplary model is shown in FIG. 4.

[0101] Typically, during operation of a service brake, one or more pistons are moved toward or away from one or more brake pads via fluid pressure (of brake fluid). Typically, during operation of a parking brake, one or more pistons are moved toward or away from one or more brake pads via a motor gear unit connected to one or more linkages including a spindle and spindle nut. The present disclosure contemplates that operation of a service brake may be achieved via fluid pressure and / or a motor assembly. The present disclosure contemplates that operation of a parking brake may be achieved via a motor assembly and / or fluid pressure.

[0102] The method may include estimating hydraulic pressure applied to a piston by a hydraulic brake system. The hydraulic pressure may be estimated from one or more sensor inputs. Typically, the master cylinder and / or one or more wheel cylinders include sensors for measuring pressure. However, the pressure at each wheel may differ from the pressure at the master and / or wheel cylinders. The pressure at each wheel may be estimated from one or more other sensor inputs.

[0103] During operation of a hydraulic braking system, brake fluid pressure is typically applied to a master cylinder by the load on the brake pedal, which then transmits the pressure through one or more conduits to the wheel cylinders of the brake mechanisms on each wheel. The master cylinder may be located on or near the firewall. A booster may be used to increase the load applied to the brake pedal.

[0104] Oil pressure may be estimated based on a logic table, taking into account fault or degradation conditions. Oil pressure may be estimated by averaging the pressure sensed at the master cylinder and / or one or more wheel cylinders. In some cases, one or more sensor inputs may not be available due to a fault or degradation condition. In this case, the pressure estimate may be adjusted. Thus, fault redundancy is provided.

[0105] The hydraulic pressure may be estimated from a first pressure associated with the left wheel cylinder, a second pressure associated with the right wheel cylinder, a third pressure associated with the master cylinder, or any combination thereof. The first, second, and / or third pressures may be obtained from respective pressure sensors associated with the left wheel cylinder, the right wheel cylinder, and / or the master cylinder, or the first, second, and / or third pressures may be estimated from separate sensor inputs.

[0106] If both the left and right wheel cylinder sensed pressures are available, the estimated oil pressure may be the average of the two, in which case the master cylinder pressure may be ignored.

[0107] If one of the left and right wheel cylinder sensed pressures is available, the estimated oil pressure may be the pressure sensed in the respective wheel cylinder for which pressure is available, in which case the master cylinder pressure may be ignored.

[0108] If neither the left nor right wheel cylinder sensed pressure is available, the estimated oil pressure may be the pressure sensed at the master cylinder.

[0109] If none of the left wheel cylinder sensed pressure, right wheel cylinder sensed pressure, and master cylinder sensed pressure are available, the estimated oil pressure may be set to a default value.

[0110] Although system accuracy may decrease as alternate pressure input sources are passed through the above alternatives, the method provides several suitable alternatives before relying on the default value.

[0111] Instead of a position sensor for determining the position of an electromechanical actuator component (e.g., spindle), the present disclosure provides a method for controlling an electromechanical actuator ultimately based on measured motor voltage and / or current. Ultimately, the position of the electromechanical actuator component (e.g., spindle) and / or the force exerted by the electromechanical actuator component (e.g., spindle) can be estimated from the measured motor voltage and / or current. Such estimation may proceed as described with respect to Figures 6A and 6B herein and in accordance with the teachings of U.S. Patent No. 10,137,878 B2, which is incorporated herein by reference in its entirety for all purposes.

[0112] The position of a component (e.g., a spindle) and / or the force applied by the component can be determined from the current and / or voltage of a motor of the electromechanical braking system. The position can be determined at a zero load condition. The current and / or voltage can be related to the torque applied by the motor. The torque applied by the motor can be related to the torque applied by the spindle. The torque applied by the spindle can be related to the spindle position and / or spindle force.

[0113] Although this disclosure refers to the position of the spindle nut, the linear or angular position of any component of the electromechanical braking system may be considered in the methods of this disclosure. The linear or angular position of any component of the spindle nut, spindle, or motor assembly may be relative to one another.

[0114] In application operation, the electromechanical brake system may be controlled based on an estimated force, such as that referred to herein as a clamping force applied to the rotor. In this regard, the estimated force may be used in a control strategy to prevent the superposition of forces associated with the electromechanical actuator system and the hydraulic actuator system from exceeding a maximum force threshold.

[0115] In estimated force-based control, the disclosed method comprises estimating the force exerted on the rotor by a component (e.g., a spindle) of the electromechanical actuator (e.g., indirectly via a spindle nut that cooperates with the spindle and engages a brake pad).

[0116] The method may comprise correcting an estimated force applied by the electromechanical actuator based on a pressure associated with the hydraulic actuator system. Thus, depending on the measured or estimated pressure, the force of the electromechanical actuator may be corrected (e.g., reduced) to meet a target force and to avoid the superposition of forces applied by the electromechanical brake system and the hydraulic brake system exceeding a maximum force threshold. In this regard, unnecessary application of force beyond the target force and / or damage caused by exceeding a maximum force threshold may be mitigated and / or prevented.

[0117] Operation of both the electromechanical brake system and the hydraulic brake system in an apply operation can result in a load superposition. In an apply operation, the electromechanical brake system and / or the hydraulic brake system can move a piston toward and / or apply a load to one or more brake pads. Accordingly, the target force of the electromechanical brake system can be adjusted so that the combined force from the electromechanical brake system and the hydraulic brake system is less than a maximum load threshold. Such adjustments can take into account the hydraulic pressure of the hydraulic brake system. Such adjustments can occur before, during, or after operation of the electromechanical brake system in the apply direction.

[0118] In a release operation, the electromechanical brake system may be controlled based on the position, i.e., the position of a component of the electromechanical actuator system (e.g., the spindle). In this regard, the position may be used in a control scheme to ensure the necessary clearance between the rotor and one or more brake pads.

[0119] The method may include correcting an estimated position of a component of the electromechanical actuator based on pressures associated with the hydraulic actuator system. Thus, with the measured or estimated force, the position of the electromechanical actuator may be corrected (e.g., moved in an apply or release direction, typically in the release direction) to achieve a desired running clearance. In this regard, residual caliper drag may be reduced and / or prevented.

[0120] Residual caliper drag can be generated by contact between the brake disc and one or more brake pads when no braking pressure is applied by the electromechanical and / or hydraulic brake systems. Residual caliper drag can result from insufficient running clearance between one or more brake pads and the brake disc. During the release operation of a hydraulic brake system, the load applied to the brake pads transitions from being shared between the hydraulic brake system and the electromechanical brake system to being applied entirely by the electromechanical system.

[0121] The transfer of load to the electromechanical system may cause the electromechanical system to misalign in the release direction due to elastic deformation of the material, slippage between components, gaps between components, or any combination thereof. Misalignment due to one or any combination of these factors may be referred to herein as relaxation or deflection. As the electromechanical brake system relaxes in the release direction, it may relax and move in the extension and / or application direction, thereby reducing the misalignment of the zero-load position of the components of the electromechanical brake system. Therefore, the zero-load position is adjusted in the release direction, and the electromechanical brake system is adjusted to the corrected zero-load position so that a running clearance (e.g., approximately 0.5 mm to 1.5 mm) can be maintained after hydraulic pressure release.

[0122] The control of the electromechanical braking system may include closed-loop estimation.

[0123] As described herein with respect to FIG. 4, empirical and / or theoretical models may relate pressures associated with a hydraulic actuator system to forces and positions. FIG. 4 is merely an exemplary model, and the present teachings are not intended to be limited to this model. Thus, if control is force-based, pressure may be related to force, and if control is position-based, pressure may be related to position. In other words, the force applied by the hydraulic actuation system is related to the pressure of the hydraulic actuation system, and the zero-load position deviation of the electromechanical actuation system is related to the pressure of the hydraulic actuation system. The force applied by the hydraulic actuation system and the zero-load position deviation of the electromechanical actuation system may be calculated, estimated, or otherwise determined from the pressure.

[0124] FIG. 1 illustrates a failure redundancy scheme. Inputs related to the left front wheel (FL), right front wheel (FR), left rear wheel (RL), and right rear wheel (RR) are considered. As taught herein, wheel speeds can be used to determine whether the vehicle is in a static or dynamic state. Speeds are determined for each wheel. Thus, if one or more of the inputs are unavailable, the method can rely on other inputs or predetermined values.

[0125] In general, the method determines the maximum wheel speed for a diagonal pair of wheels (e.g., front left and rear right wheels). The method then determines the minimum of the two maximum values ​​determined from each diagonal wheel pair. This minimum is the estimated wheel speed.

[0126] If input from any of the front wheels is unavailable, the method relies on the corresponding rear wheel in the diagonal pair. If input from both front wheels or from any of the rear wheels is unavailable, the method sets the estimated speed to a fault value.

[0127] FIG. 2A shows a graph of gradient ranges. Each gradient range is bounded by thresholds (T1, T2, and T3). The graph shown is merely exemplary, and a greater or lesser number of discrete gradient ranges are contemplated by the present teachings. As taught herein, longitudinal acceleration can be used to determine gradient. The gradient can be bounded into discrete ranges, and a load to which the electromechanical actuator is adjusted can be assigned to each gradient range.

[0128] 2B shows a graph of target load as a function of slope. In addition to or as an alternative to the method of FIG. 2A, the load can be adjusted according to a linear (dashed line), non-linear (dotted line), or piecewise (solid line) relationship as a function of slope.

[0129] 3A shows a graph of parking brake and service brake operating parameters as a function of time. The present disclosure is at least partially concerned with the operation between (3) and (4) where force superposition occurs, and the operation between (5) and (6) where running clearance returns between the brake pads and the brake disc.

[0130] At (2), the zero-load travel of the electromechanical brake system ("electric parking brake" or "EPB") stops, and the electromechanical brake system contributes to the load applied to the brake pads. If the electromechanical brake system and the hydraulic brake system ("hydraulic service brake" or "HSB") are operational, the disclosed method determines the required spindle nut travel, taking into account the hydraulic pressure of the hydraulic brake system, so that the combined load of the electromechanical brake system and the hydraulic brake system meets and / or does not exceed the maximum recommended load (A). Between (3) and (4), the hydraulic pressure of the hydraulic brake system is released, and the total load applied to the brake pads is transferred entirely to the electromechanical brake system. When the hydraulic brake system is released, the relaxation of the electromechanical brake system leaves the electromechanical brake system in the applied position, but the spindle nut of the electromechanical brake system moves ("deflects") a certain distance in the release direction.

[0131] Between (4) and (5), the FPB load and total load are 28845N, the HPS load is 0N, the motor current is 0A, the motor speed is 0RPM, the motor voltage is 0V, the motor driving torque is 0Nm, the pressure wave is 0bar, the spindle position is 0.522mm, and the deflection is 0.522mm.

[0132] At (5), the electromechanical brake system releases the load on the brake pads, and the spindle nut position returns to a zero-load position between (5) and (6). At (6), a running clearance exists. The disclosed method accounts for hydraulic pressure to determine the deflection of the spindle nut due to relaxation of the electromechanical brake system, shown in FIG. 3B as the difference between (Y) and (X). The disclosed method accounts for relaxation in the target load so that the desired load is achieved after relaxation. Without accounting for relaxation, the zero-load position (between (5) and (6)) may be distorted by the difference between (Y) and (X). In some circumstances, residual caliper drag may occur if the difference between (Y) and (X) meets or exceeds the running clearance between the brake pads and the brake disc.

[0133] Hydraulic pressure may be accounted for by an empirical or theoretical model, such as that shown in Figure 4. This disclosure contemplates that the model of Figure 4 is merely exemplary and may be specific to different types of brake systems and / or different vehicle makes, models, model years, and / or trim levels.

[0134] Figure 4 shows a graph illustrating the clamping force applied by the parking brake as a function of spindle nut position and hydraulic pressure. The position of the spindle nut (x-axis) actuated by the electromechanical braking system is related to the clamping load (y-axis) applied to the brake pads by the electromechanical braking system. Considering only the x- and y-axes, as the spindle nut position moves in the application (positive) direction, the clamping load increases beyond the zero-load position. Point B indicates the zero-load position where the spindle nut contacts the piston but applies no load.

[0135] When hydraulic pressure (z-axis) is applied to the piston by the hydraulic brake system, the position of the piston is displaced in the application direction, and the zero-load position of the spindle nut is adjusted in the application direction accordingly. Since the zero-load position is adjusted along line A' (e.g., point B'), the electromechanical brake system may adjust the position of the spindle nut by the difference between the x-axis coordinate of point B and any point along line A' (e.g., point B').

[0136] If hydraulic pressure is not taken into account, the running clearance when hydraulic pressure is released can be reduced by the difference between the x-axis coordinate of point B and any point along line A' (for example, point B').

[0137] Line (B) indicates the maximum load in the model. Therefore, when hydraulic pressure is applied to the piston, the electromechanical brake system may adjust its operation to avoid meeting or exceeding the maximum EPB clamp load upon pressure release.

[0138] Figure 5 shows a schematic diagram of the split architecture. The electromechanical brake systems (e.g., parking brakes) for the left and right brake calipers are operated by separate controllers. The controllers communicate with their respective brake calipers (line (A)), each other (line (B)), and with existing vehicle systems (line (C)).

[0139] 5 shows an electronic stability controller dedicated to the right brake caliper and a booster controller dedicated to the left brake caliper, this disclosure contemplates that the reverse arrangement may be used, and that any other vehicle controller may operate any brake caliper.

[0140] In the event of a fault or deterioration condition (e.g., malfunction of the right electromechanical actuator), the fault or deterioration condition may be communicated by the controller of the failed / deteriorated brake caliper to the other controllers, which in turn instructs the operable brake calipers (e.g., by the electromechanical brake system) to apply a maximum default load to the rotors. In this way, vehicle stationary state may be ensured.

[0141] FIG. 6A shows a flow diagram or control model of a linear time variable ("LTV") 10 contained within the controller. Because no position sensors are used to determine the position of the motor, actuator assembly, and / or brake piston in this parking brake system, the LTV 10 is used to accurately estimate the motor position, actuator position, spindle position, nut position, or a combination thereof. The LTV 10 is also used to accurately estimate motor speed or force and motor current. The control logic architecture of the LTV 10 comprises various models that can be combined or cascaded. The models of the LTV 10 include a harness model 12, a state estimation model 14, a force estimation model 16, and a linearization model 18.

[0142] The harness model 12 may be a model of the vehicle harness from the controller to the actuator assembly. The motor current 20 and voltage 22 are measured at the harness model 12. Before the electromechanical actuator system is actuated, the load on the motor is known to be zero. Therefore, the input voltage 22 and input current 20 to the motor are known.

[0143] After the electromechanical actuator system is activated and the load on the motor increases to apply or release the parking brake, the motor draws additional current (i.e., motor current) from the power source to maintain the motor's operating state, activating and moving the motor gear unit ("MGU"), actuator assembly, brake pads, or brake shoes, etc., to generate a clamping force. As the current drawn by the motor increases, the voltage at the motor terminals drops due to the harness resistance. This change in current is measured in harness model 12. The harness resistance is accounted for in these measurements, and the motor voltage is determined based on the measured current and voltage in the harness model. Motor current measurements 24 and motor voltage measurements 26 of the motor are output from harness model 12 and input to state estimation model 14.

[0144] The state estimation model 14 (related to the motor dynamics and gear dynamics described with respect to FIG. 6B ) is a model used to estimate the motor position, motor speed, and / or motor current. The state estimation model 14 may be a linearized state-space model of the actuator assembly. The motor position, motor speed, and / or motor current are estimated based on current measurements 24 and voltage measurements 26 from the harness model 12. One or more of the motor position, motor speed, and motor current are included in Xhat 28, which is an output of the state estimation model 14. The estimated motor position (included in Xhat 28) is output from the state estimation model 14 and input to the force estimation model 16. As shown and described with respect to FIG. 6B , the state estimation model 14 takes into account motor dynamics 30 and gear dynamics 32. The estimated states (e.g., motor position, motor speed, and / or motor current contained in Xhat28) are output from the state estimation model 14 and fed back to the state estimation model 14 to provide error correction terms based on the estimated and measured currents, as described in more detail below.

[0145] The force estimation model 16 is a model used to estimate a clamping force 36, which may be used interchangeably with parking brake force herein. The force estimation model 16 may provide a force model that may be implemented as a polynomial regression or a look-up table for estimating the clamping force 36. In the force estimation model 16, the clamping force 36 is estimated based on an estimated motor position 34 and a pressure 38 associated with a hydraulic actuator system (e.g., a service brake). However, the clamping force 36 may additionally or alternatively be estimated based on an estimated motor current and / or an estimated motor speed. The estimated clamping force 36 may be, for example, a second-order polynomial regression of the estimated motor position 34. The estimated motor position 34 and the estimated clamping force 36 are output from the force estimation model 16.

[0146] During application of the parking brake, the clamping force is the amount of force generated when the brake pads or brake shoes are pressed against the braking surface (e.g., the brake rotor or brake drum, respectively) to limit or prevent movement of the wheel or vehicle. When the parking brake is released, the clamping force decreases and the wheel or vehicle can move again.

[0147] Those skilled in the art will appreciate that the friction material of the brake pads and brake shoes typically wears over time, requiring the brake pads and shoes to move further toward the braking surface to generate sufficient clamping force. Therefore, to compensate for this additional required movement of the brake pads and shoes, as well as the actuator assembly, the motor position changes to generate the required clamping force. Therefore, the LTV 10 continually updates to compensate for this wear and the corresponding changes in motor and / or actuator position. These updates are implemented in a force estimation model 16 that is centered around a zero-clearance condition where the brake pads or brake shoes begin to engage the rotor or drum, respectively.

[0148] The clamping force 36 output from the force estimation model 16 is input to the linearization model 18. The output of the linearization model 18 is an estimate of the motor load torque 40, which linearizes the state estimation model 14 (i.e., estimated motor position, motor speed, motor current) using feedback linearization. The estimated motor load torque 40 is fed to the state estimation model 14 along with the estimated state output from the state estimation model 14 (i.e., Xhat, estimated motor position, estimated motor speed, estimated current draw by the motor, or a combination thereof). By using feedback of the motor load torque 40 to the state estimation model 14, the system is represented in a state space representation where the state A matrix is ​​a time-varying matrix (i.e., A(t)) as defined in Equations 20 and 22 below. Feedback linearization with respect to the motor operating load 40 provides an accurate linear state space formulation for estimating the internal state (Xhat) using Equations 36-39 below.

[0149] 6B shows an LTV 10 defined by a parametric system model. The parametric system model may be described by motor dynamics subcomponents 30, gear dynamics subcomponents 32, spindle dynamics subcomponents 42, and parking brake dynamics subcomponents 44. One or more models or subcomponents may define the LTV.

[0150] When a load is applied to the motor during parking brake application or parking brake release, the motor draws additional current, which is an output measurement from the harness model 12, as described above. Motor speed 46 and motor current 24 are estimated as outputs from the motor dynamics model 30. Motor speed 46 and motor current 24 are estimated based on the voltage 26 measurement output and the motor load torque 40. Motor speed 46 and corresponding spindle position 48 are used to determine motor load torque 40, which is fed back to the motor dynamics model 30 so that the LTV 10 can continuously update the motor position 34. Spindle speed 50, based on motor speed 46, is output from the gear dynamics model 32 and input to the spindle dynamics model 42 to determine spindle torque 52 based on load force feedback from the park brake dynamics model 44. Spindle position 54 is related to spindle speed 50. Spindle position 54 is an output from spindle dynamics model 42 and an input to park brake dynamics 44. Spindle force 56 is an output from park brake dynamics 44 and is also fed back to spindle dynamics model 42 so that LTV 10 can continuously update spindle position 54 to spindle force 56 as brake pads or brake shoes wear over time. Spindle load force 58 is related to clamp force 36 illustrated in FIG. 6A.

[0151] The motor dynamics subcomponents 30 may be modeled using Kirchhoff's voltage law, torque balance equations, and / or Ohm's law. The input voltage 22 to the motor may be derived from observed electronic control currents and voltages using nominal vehicle harness resistance. The generated motor torque (K t The motor terminal voltage (U) can be estimated based on the harness resistance and current observations 24, based on Ohm's law. The motor voltage (U) is calculated based on the measured ESC voltage (V), as shown in EQ1. esc) to harness voltage drop (iR r ) minus U=V esc -iR r EQ1

[0152] The rate of change of current 24 in the parametric system model can be expressed as the applied motor voltage (U) minus the back EMF voltage and the resistive drop in the circuit, as shown in EQ2, where L is the circuit inductance, R is the circuit resistance, and K b represents the back EMF constant of the motor.

number

[0153] In the torque balance equation, the inertia (J) can be composed of the motor component in addition to the equivalent reflected inertia from the actuator assembly, including the spindle and nut. For highly reduced speed systems, such as those typified by the motor in a caliper system, the equivalent inertia is 1 / R 2 Therefore, the motor acceleration is calculated by the motor torque (K t i) to the motor load torque (T m )40 and minus the viscous losses due to internal damping.

number

[0154] The gear dynamics subcomponent 32 is the amplified motor torque (T m ) model. The total amplification is calculated by the lumped reduction ratio (R t ) and gear efficiency (η t ) This relationship is a function of the spindle torque T s This can be shown by EQ4, which is represented by:

number

[0155] The spindle dynamics 42 may be a model of the spindle and nut. The parking brake force F(t) is calculated based on one or more spindle and nut parameters and the spindle torque (T s (t)) can be related to the parking brake force F(t) and the spindle torque (T s The relationship between (t) and (t) may depend on the particular operating mode of the spindle (e.g., whether the spindle is operating during parking brake application or parking brake release) and may be expressed as a piecewise equation in terms of motor and / or spindle speed. Due to the self-locking effect between the spindle and nut, there is significant stiction (i.e., friction that prevents the spindle and nut from moving out) within the actuator assembly when transitioning from static to dynamic friction. Therefore, since the estimation is only valid during non-zero motor speeds, stiction of the actuator assembly can be neglected and the dominant friction during operation can be considered dynamic friction.

[0156] The spindle torque equations for both parking brake application and parking brake release may be defined by equations EQ5 and EQ6, respectively. The spindle coefficient equation (SF sa ,SCIENCE FICTION sr ) can be expressed in one or more forms for symmetric and asymmetric threads. For example, the spindle factor SF sa ,SCIENCE FICTION sr may be represented by EQ7 and EQ8, respectively. The spindle parameters may include one or more parameters such as spindle friction μ, effective spindle diameter dm, spindle lead l, and spindle flank angle α. The bearing parameters may include bearing friction μ db and effective bearing diameter d bThe spindle and bearing parameters (SF) may be estimated using adaptive control methods to address degradation of the parking brake system over time. Combining EQ5 and EQ7, and EQ6 and EQ8 results in EQ9 and EQ10, respectively.

number

[0157] The park brake dynamics 44 and the corresponding brake piston displacement can be related to the generated parking brake force (F(t)) based on the system stiffness characteristics. The system stiffness characteristics can be represented by an appropriate regression model, such as a linear regression model, a quadratic regression model, a cubic regression model, or a quartic regression model. For example, the system stiffness can be represented by the characteristics shown in EQ16 and EQ17 for parking brake application and parking brake release, respectively. In a disc brake system, the parking brake force (F(t)) can be realized by two regression coefficients C1 and C2. These regression coefficients C1 and C2 can be further refined to form a model of piston position versus parking brake force (F(t)) as a function of both temperature and wear. Accordingly, the parking brake force (F(t)) can be related to the spindle torque (T) as a function of piston position and spindle coefficient (SF). s (t)) can be substituted into EQ9 and EQ10. F(t)=C1x(t) 2 +C2x(t) EQ11 T sa (t)=SF sa [C1x(t) 2 +C2x(t)] EQ12 T sr (t)=SF sr [C1x(t) 2 +C2x(t)] EQ13

[0158] The park brake dynamics 44 may be represented using a state space representation. The overall efficiency of the parking brake system may be lumped into a single representation for use in adaptive control. This single representation may consist of one or more parameters, such as motor, MGU, bearing, and spindle efficiency parameters. The lumped spindle coefficients are described in EQ14 and EQ15 for parking brake application and parking brake release, respectively. The motor load torque (T m The expressions for EQ14 and EQ15 are written in EQ16 and EQ17 after substituting EQ14 and EQ15 into the motor load torque equation EQ4 and the spindle torque equations EQ9 and EQ10, respectively.

number

[0159] The parking brake system may be represented in a nonlinear form. The internally selected system states may be motor position (θ), motor speed ({grave over(θ)}), and motor current (i). The system observations are described by the state output (y), given only the motor current (i). This motor current observation (i) is generated by a control unit, electronic stability controller, or equivalent vehicle hardware. The LTV 10 may rely on knowledge of the input voltage (U) 22 and motor current (i) 24 observations to correct the state estimate (predictor-corrector).

number

[0160] The motor load torque (T m) 40 may be evaluated as a time-varying parameter to linearize the state-space representation of EQ 18 for the currently operating motor load. Linearization may be completed through feedback to the state estimation model 14 to update the model 14 in discrete time. The linearized state-space formation is shown in equations EQ20-EQ23. This feedback linearization allows for the use of linear time-varying estimates of motor position (θ), motor speed ({grave over(θ)}), and motor current (i). This feedback linearization is represented by Fx(t) in EQ22 below.

number

[0161] Observability (Ob) may refer to how well the internal state of the system (i.e., motor position (θ), motor speed ({grave over(θ)}), and motor current (i)) can be inferred from knowledge of the external outputs. A system may be observable if, for any possible sequence of states and control vectors, the current state can be determined in finite time using only the outputs. This quality can be assessed by checking the rank of the observability matrices EQ34 and EQ35. All parameters in the observability matrix EQ35 are related to the generated parking brake force (F x (t)) may be constant time-invariant parameters. x (t)) may be a time-varying parameter. x (t)) may take on either a positive real representation of the parking brake force or the value zero. For the generation or parking brake force, the observation matrix may be full rank, which may correspond to complete observability. Complete observability may mean that all internal system states can be estimated based on the observation of the motor current (i).

[0162] During application of the parking brake, the parking brake force may be coupled with the position of the motor, the actuator assembly, or both to provide a predictor-corrector relationship such that the estimate is corrected based on the defined system dynamics.

number

[0163] The theoretical expression of the LTV10 with gain (L) can be provided in equations EQ36 and EQ37 for continuous time and in equations EQ38 and EQ39 for discrete time representation. The gain (L) can be selected using pole placement techniques to meet the system response specifications. Since the system dynamics are time-varying, for pole placement design criteria, the gain parameter L in the vector is expressed as L = f(F) or correspondingly L = f(T m ) based on the current operating conditions.

number

[0164] Another advantage of the state-space methodology can be that the estimated and measured motor currents can be used to adapt internal model-based parameters over the life of the actuator assembly. In other words, the spindle factor (SF sa ,SCIENCE FICTION sr ) may be lumped with thrust bearing and MGU efficiencies and adapted based on the error between estimated and measured motor current. This degradation adaptation may be used to adapt the overall parking brake system efficiency within LTV 10 to account for the degradation of the actuator assembly. This adaptation preferably reduces the overall estimation error and / or reduces force and position control variations, thereby enabling a reduction in system size, which ultimately results in reduced weight and system cost. Degradation adaptation is achieved using equation EQ40 and determines the spindle factor (SF) according to EQ41. sa ,SCIENCE FICTION sr) may be weighted relative to previous adaptations to minimize variation in ω, where ω is a weight assigned to each adaptation and the sum of the weights is equal to 1.

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[0165] It is understood that the above description is intended to be illustrative and not restrictive. Accordingly, the specific embodiments described herein are not intended as exhaustive or limiting teachings. Numerous embodiments and applications other than the examples provided will be apparent to those skilled in the art upon reading the above description. Those skilled in the art may adapt and apply the present teachings in numerous forms, as may best suit the requirements of a particular application. Other combinations are possible, as can be seen from the claims below, which are also incorporated herein by reference.

[0166] Accordingly, the scope of the present teachings should be determined not with reference to the above description, but should instead be determined with reference to the appended claims, along with the full range of equivalents to which such claims are entitled. Any omission in the following claims of any aspect of subject matter disclosed herein should not be construed as a disclaimer of such subject matter, nor as an indication that the inventors do not consider such subject matter to be part of the disclosed inventive subject matter.

[0167] Multiple elements or steps may be provided by a single integrated element or step, or a single element or step may be divided into multiple elements or steps.

[0168] The disclosure of "a" or "one" to describe an element or step is not intended to exclude additional elements or steps.

[0169] Terms such as "first," "second," and "third" may be used herein to describe various elements, components, regions, layers, and / or sections, but these elements, components, regions, layers, and / or sections should not be limited by these terms. These terms may be used to distinguish one element, component, region, layer, or section from another element, component, region, layer, or section. These terms do not imply an order or hierarchy unless clearly indicated by context. Thus, a first element, component, region, layer, or section may be referred to as a second element, component, region, layer, or section without departing from the present teachings.

[0170] Spatially relative terms, such as "inside," "outside," "below," "lower," "bottom," "upper," "top," and the like, may be used herein to facilitate the description of an element or feature depicted in a figure relative to another element(s) or feature(s). Spatially relative terms may be intended to encompass different orientations of the device during use or operation in addition to the orientation shown in the figures. For example, if a device in a figure is inverted, elements described as "below" or "below" other elements or features would be oriented "above" the other elements or features. Thus, the exemplary term "below" may encompass both an up and down orientation. The device may be in other orientations (e.g., rotated 90 degrees or other orientations), and the spatially relative descriptors used herein would be interpreted accordingly.

[0171] The terms "approximately" or "substantially" when describing an angular measurement may mean within about + / -10° or less, within about + / -5° or less, or within about + / -1° or less. The terms "approximately" or "substantially" when describing an angular measurement may mean within about + / -0.01° or more, within about + / -0.1° or more, or within about + / -0.5° or more. The terms "approximately" or "substantially" when describing a linear measurement, percentage, or ratio may mean within about + / -10% or less, within about + / -5% or less, or within about + / -1% or less. The terms "approximately" or "substantially" when describing a linear measurement, percentage, or ratio may mean within about + / -0.01% or more, within about + / -0.1% or more, or within about + / -0.5% or more.

[0172] Unless otherwise specified, all ranges include both endpoints and all values ​​therebetween. The use of "about" or "approximately" in connection with a range applies to both ends of that range. Thus, "about 20 to 30" is intended to include "about 20 to about 30," inclusive of at least the specified endpoints.

[0173] The term "consisting essentially of" to describe a combination is intended to include the identified elements, components, or steps, as well as other elements, components, or steps that do not materially affect the basic and novel characteristics of the combination. The use of the terms "comprising" or "including" herein to describe a combination of elements, components, components, or steps also contemplates embodiments that consist essentially of that element, component, component, or step.

[0174] The disclosures of all articles and references, including patent applications and patent publications, are incorporated by reference for all purposes.

Claims

1. 1. A method of controlling a brake system in a vehicle having an electromechanical system and a hydraulic system, the electromechanical system and the hydraulic system acting on a common wheel, the electromechanical system and the hydraulic system being capable of operating in a superimposed manner, the method comprising: measuring a voltage of a motor contributing to the electromechanical system; measuring the current of the motor; estimating a position of a component actuated by the motor based on the voltage and the current; estimating a force exerted by the component based on the voltage and the current; and estimating hydraulic pressure associated with said hydraulic system; Equipped with During a brake application operation of the brake system, the force on the component is corrected based on the hydraulic pressure; The method wherein, during a release operation of the brake, the position of the component is corrected based on the hydraulic pressure.

2. The method of claim 1 , wherein the oil pressure is estimated based on a predetermined logic table that uses one or more sensor inputs, taking into account fault or degradation conditions.

3. 3. The method of claim 2, wherein the oil pressure is estimated from a first pressure associated with a left wheel cylinder, a second pressure associated with a right wheel cylinder, a third pressure associated with a master cylinder, or any combination thereof, wherein the first, second, and third pressures are obtained from respective pressure sensors associated with the left wheel cylinder, the right wheel cylinder, and / or the master cylinder, or the first, second, and third pressures are estimated from another sensor input.

4. if both the first pressure sensed in the left wheel cylinder and the second pressure sensed in the right wheel cylinder are available, the estimated oil pressure is an average of both; if only one of the first pressure sensed in the left wheel cylinder and the second pressure sensed in the right wheel cylinder is available, the estimated oil pressure is the available one of the first pressure or the second pressure; if neither the first pressure sensed at the left wheel cylinder nor the second pressure sensed at the right wheel cylinder is available, the estimated oil pressure is the third pressure sensed at the master cylinder; 4. The method of claim 3, wherein if none of the first pressure sensed at the left wheel cylinder, the second pressure sensed at the right wheel cylinder, and the third pressure sensed at the master cylinder are available, the estimated oil pressure is set to a default value.

5. The method of claim 1 , wherein the component is a spindle nut, a spindle, a component of a motor assembly, or any combination thereof.

6. The method of claim 5 , wherein the component is the spindle.

7. rotating the spindle in a first direction about an axis with the motor such that the spindle nut moves one or more brake pads against a braking surface; rotating the spindle about the axis with the motor in a second direction so as to move the one or more brake pads away from the braking surface; The method of claim 6 further comprising:

8. 2. The method of claim 1, wherein, during the apply operation, the compensation reduces and / or prevents damage caused by a combination of loads of the electromechanical system and the hydraulic system, and during the release operation, the compensation reduces and / or prevents damage caused by residual caliper drag.

9. The method of claim 1 , wherein the control of the electromechanical system is closed loop.

10. Estimating a vehicle gradient; adjusting the electromechanical system to the force exerted by the component based on the vehicle gradient; The method of claim 1 further comprising:

11. The method of claim 10 , further comprising obtaining a longitudinal acceleration of a vehicle, and wherein the vehicle gradient is estimated based on the longitudinal acceleration.

12. 12. The method of claim 11, wherein the force is set to a default value if a fault or degradation condition occurs, the fault or degradation condition including longitudinal acceleration being unavailable, the longitudinal acceleration exceeding a maximum value, the longitudinal acceleration being below a minimum value, or any combination thereof.

13. 12. The method of claim 11, further comprising obtaining wheel speeds, the wheel speeds determining whether the vehicle is in a static or dynamic state, and the vehicle gradient is estimated only when the vehicle is in a static state.

14. 14. The method of claim 13, wherein the wheel speed is the minimum of a maximum wheel speed of a first set of diagonal wheels including a front left wheel and a rear right wheel and a maximum wheel speed of a second set of diagonal wheels including a front right wheel and a rear left wheel.

15. if a failure or deterioration condition occurs with respect to the left front wheel or the right front wheel, the wheel speed of the corresponding rear wheel in the first diagonal wheel set or the second diagonal wheel set is considered in determining the minimum value; if a failure or deterioration condition occurs with respect to both the left front wheel and the right front wheel, the wheel speeds are set to default values; The method of claim 14 , wherein if a failure or deterioration condition occurs with either the left rear wheel or the right rear wheel, the wheel speed is set to the default value.

16. 14. The method of claim 13, wherein the vehicle is assumed to be in a static state if the wheel speed is below a static threshold for a predetermined period of time, and the vehicle is assumed to be in a dynamic state if the wheel speed is above a dynamic threshold for the predetermined period of time.

17. The method of claim 11 , wherein the force is determined based on the vehicle gradient.

18. 18. The method of claim 17, wherein the force is determined by the vehicle slope falling within a discrete range of vehicle slope and / or the force is modeled as a function of the vehicle slope, the function being linear, non-linear, or piecewise.

19. detecting, by a first controller, a fault or deterioration condition associated with a first brake caliper to which the first controller is assigned; communicating, by the first controller, the fault or deterioration condition to a second controller assigned to a second brake caliper; setting the force associated with the second brake caliper to a default force; The method of claim 1 further comprising:

20. 20. The method of claim 19, wherein the first controller and the first brake caliper are located on a passenger side of a vehicle and the second controller and the second brake caliper are located on a driver side of the vehicle, or vice versa.

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