Brake pedal emulator of a brake-by-wire system
Patent Information
- Authority / Receiving Office
- DE · DE
- Patent Type
- Patents
- Current Assignee / Owner
- GM GLOBAL TECHNOLOGY OPERATIONS LLC
- Filing Date
- 2017-08-07
- Publication Date
- 2026-07-23
AI Technical Summary
Conventional brake pedal feel in hydraulic systems cannot be tailored to a driver's preferences, and brake-by-wire systems lack the ability to emulate the resistance and feedback experienced in traditional hydraulic braking systems.
A brake pedal emulator using a hydraulic cylinder with magneto-rheological hydraulic fluid and an electrical element to control viscosity, simulating the brake pedal feel by adjusting damping forces through electrical control.
The emulator provides adjustable brake pedal feedback similar to traditional systems, allowing for real-time control of damping forces and emulating the desired brake pedal feel.
Smart Images
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Abstract
Description
AREA OF INVENTION
[0001] The subject matter of the invention relates to a brake-by-wire system (BBW system) and in particular a brake pedal emulator of the BBW system and methods for its operation. BACKGROUND
[0002] Conventional automotive braking systems are typically hydraulically operated and activated when the driver presses the brake pedal, which generally actuates a master cylinder. The master cylinder, in turn, pressurizes the hydraulic fluid in various hydraulic lines that lead to corresponding actuators at the brakes located next to the wheels. Such a hydraulic braking system can be augmented by a hydraulic modulator system, which supports the anti-lock braking system (ABS), traction control (TCS), and systems for enhanced vehicle stability. The wheel brakes are primarily operated by the manually operated master cylinder with supplemental pressure gradients supplied by the hydraulic modulator system during anti-slip, traction control, and stability enhancement operating modes.
[0003] When the driver presses the brake pedal, which in turn actuates a piston in the master cylinder to activate the wheel brakes, they encounter pedal resistance. This resistance is caused by a combination of factors, such as the actual braking forces at the wheels, hydraulic pressure, mechanical resistance in the brake booster / master cylinder, the force of a return spring acting on the brake pedal, and others. Therefore, a driver becomes accustomed to this feeling of resistance as a normal occurrence while driving. Unfortunately, the feel of conventional brake pedals cannot be adjusted to a driver's preferences.
[0004] Recent advances in braking technology include brake-by-wire (BBW) systems, which actuate the vehicle's braking system via an electrical signal, typically triggered by an onboard controller. Braking torque can be applied to the wheel brakes without a direct hydraulic connection to the brake pedal. The BBW system can be used as a supplementary system (i.e., replacing part of the more conventional hydraulic braking system) or to completely replace a hydraulic braking system (i.e., a pure BBW system). In either case, the "brake feel" to which the driver is accustomed must be emulated.
[0005] Accordingly, it is desirable to provide an adjustable brake pedal emulator that can simulate the brake pedal "feel" of more conventional braking systems. SUMMARY OF THE INVENTION
[0006] In an exemplary embodiment of the invention, a brake pedal emulator extends between and connects a support structure and a brake pedal, which is operatively connected to the support structure. The brake pedal emulator includes a hydraulic cylinder with a magnetorheological hydraulic fluid and an electrical element configured to carry an electrical current for controlling the viscosity of the magnetorheological hydraulic fluid. By controlling the viscosity of the hydraulic fluid, a force exerted by the hydraulic cylinder against the brake pedal can be controlled.
[0007] In another exemplary embodiment of the invention, a BBW system for a vehicle includes a brake pedal that operatively engages with a support structure and a brake pedal emulator. The brake pedal emulator is designed and arranged to exert a damping force on the brake pedal and includes a hydraulic cylinder with an electrical coil and a hydraulic fluid configured to change viscosity when the electrical coil is energized.
[0008] The aforementioned features and advantages, as well as further features and advantages of the invention, are readily apparent from the following detailed description of the invention in conjunction with the associated drawings. BRIEF DESCRIPTION OF THE DRAWINGS
[0009] Other features, advantages and details appear only as examples in the following detailed description of the embodiments, the detailed description referring to the drawings in which the following applies:
[0010] Fig. Figure 1 is a schematic top view of a vehicle with a BBW system as a non-limiting example in accordance with the present invention;
[0011] Fig. Figure 2 is a schematic view of the BBW system;
[0012] Fig. Figure 3 is a diagram of a force profile of a force induction device of the BBW system as a function of the brake pedal travel;
[0013] Fig. Figure 4 is a diagram of a damping coefficient profile of the BBW system;
[0014] Fig. Figure 5 is a schematic view of a brake pedal assembly of the BBW system;
[0015] Fig. Figure 6 is a schematic representation of another embodiment of the brake pedal assembly; and
[0016] Fig. Figure 7 is a flowchart for a procedure for operating the BBW system. DESCRIPTION OF THE EXECUTION FORMS
[0017] The following description is merely exemplary and is not intended to limit the present invention in its applications or uses. It should be noted that in all drawings, the same reference numbers refer to the same or corresponding parts and features. The terms "module" and "controller" as used herein refer to a processing circuit that may include an application-specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or grouped), and memory executing one or more software or firmware programs, a combinational logic circuit, and / or other suitable components that provide the described functionality.
[0018] According to an exemplary embodiment of the invention, Fig. 1. A schematic view of a vehicle 20 , which is a drivetrain 22(i.e., engine, transmission and differential), several rotating wheels 24 (i.e., four depicted) and a BBW system 26 may include a braking system 28 for each of the corresponding wheels 24 , a brake pedal system 30 and a control system 32 may include powertrain 22 is set up so that at least one of the wheels 24 is powered so that the vehicle 20 is moved on a surface (e.g., road). The BBW system 26 is configured to generally determine the speed of the vehicle 20 slows down and / or stops the vehicle's movement. 20 can be a car, a truck, a van, an off-road vehicle or any other self-propelled or towed conveying device suitable for transporting a load.
[0019] Every brake system 28 of the BBW system 26can a brake 34 and an actuator 36 include, configured to actuate the brake. The brake 34 It can include a brake caliper and be any type of brake, including disc brakes, drum brakes, and others. Non-restrictive examples include the actuator. 36 an electro-hydraulic brake actuator (EHBA) or another actuator that controls the brake 34 can operate based on an electrical input signal provided by the controller 32 can be received. More precisely, the actuator can 36 any type of motor that responds to a received electrical signal and converts energy into motion, which acts as a brake. 34 controls the actuator. 36 a DC motor configured to generate electro-hydraulic pressure, which is supplied, for example, to the brake calipers of the brake. 34 is being managed.
[0020] The control 32 It can include a computer-based processor (e.g., a microprocessor) and a computer-readable and writable storage medium. During operation, the control system can... 32 one or more electrical signals from the brake pedal assembly 30 via a path (see arrow) 38 ) are obtained, from which the driver's braking intention can be inferred. The control 32 It can, in turn, process such signals and, at least partially based on these signals, generate an electrical control signal via a path (see arrow). 40 ) to the actuators 36 Output. Depending on the different vehicle conditions, the command signals for each wheel can be displayed. 24 they may be the same, or they can be for each wheel 24 Different signals are output. The paths 38 , 40These can be wired or wireless paths, or a combination of both. Non-restrictive examples of control. 32 They can include an arithmetic processing unit and logical operations; an electronic control unit that queries, decodes, and executes instructions from memory; and a module unit that uses multiple parallel processing elements. Other examples of control 32 They may include an engine control unit and an application-specific integrated circuit. It is further intended and expected that the control system will... 32 may include redundant controls, and / or the system may include other redundancies to improve the reliability of the BBW system. 26 to improve.
[0021] With reference to Fig. 2. The brake pedal system 30 a brake pedal 42 and a brake pedal emulator 44 include the brake pedal. 42can be derived from a fixed structure 46 are supported and are in a movable relationship with it. As a non-restrictive example, consider the brake pedal. 42 rotatable with the fixed structure 46 about a first axis of rotation 48 be connected around. The emulator 44 can be from the brake pedal 42 and the fixed structure 46 be worn and extend between them. More precisely, the emulator can 44 with the brake pedal on the second pivot axis 50 It can be rotated into engagement and can be connected to the fixed structure. 46 on a third axis of rotation 52 They can be brought into rotational engagement. The second and third axes of rotation 50 , 52 can from the first axis of rotation 48 be spaced apart, and all three axes of rotation 48 , 50 , 52They can essentially be parallel to each other.
[0022] The emulator 44 the brake pedal system 30 It is configured to simulate the behavior and / or "feel" of a more conventional hydraulic braking system. The emulator 44 can a damping device 54 and a force induction device 56 to include at least a "feel" of the brake pedal desired or expected by the driver during operation 42 to simulate. The damping device 54 It is designed and arranged in such a way that it generally produces a damping force which is a function of the speed at which a driver applies the brake pedal. 42 actuated. The force induction device 56 It generates an induced force (e.g., spring force) that is a function of the brake pedal displacement. Both the damping device 54 as well as the force induction device56 can be controlled individually or in combination 32 to be controlled in order to at least simulate the desired "pedal feel".
[0023] With reference to Fig. Section 3 will show an example of a force profile of the force induction device. 56 Generally represented as a function of brake pedal travel T, shown in the graph as pedal force F applied by the driver versus brake pedal travel T. The solid arc-shaped or curved line. 71 represents the target profile, and the dashed lines 73 represent the outer limits (i.e., the tolerance) of the target profile. The force induction device 56 can be used for all target profiles 71 be laid out.
[0024] With reference to Fig. Figure 4 presents an example of a damping coefficient profile, generally as a function of the brake pedal travel T, shown in the graph as the brake pedal travel T versus a damping coefficient D. The solid arc-shaped or curved line 75 represents the target profile, and the dashed lines 77 These represent the outer limits (i.e., the tolerance) of the target profile. Similar to the force induction device. 56 can the damping device 54 The system is designed for all target profiles. It is intended and expected that the data for the target force and damping profiles, along with the predefined target tolerances (i.e., limit values) for various processing functions, will be integrated into the control system. 32 can be programmed. It is further planned and assumed that the damping device will be able to function to a certain extent. 54It can be adjustable, with this adjustability depending on the control system. 32 is done in such a way that, for example, the pre-programmed profiles of the Fig. 3 and Fig. 4 must be adhered to. Furthermore, the damping coefficient curve of Fig. 4. This is one of a multitude of damping coefficient curves, each associated with an aspect of vehicle modeling. It is further noted that the damping coefficient D is a function of the pedal position and that the damping force is a function of the pedal actuation rate and the pedal position.
[0025] With reference to Fig. 2. The emulator can 44 furthermore a connecting element 58 include the brake pedal 42 with the devices 54 , 56 on the second axis of rotation 50 operationally connects. A distance sensor 60 of the emulator 44can be configured to shift (e.g., a linear or an angular shift) at least one brake pedal 42 and the connecting element 58 measures. The emulator 44 can also include at least one pressure sensor 62 include, which is generally located on a reactive side of the devices 54 , 56 (i.e., near the third axis of rotation) 52 ) is oriented to measure the applied pressure. It is intended and assumed that the pressure sensor 62 a pressure transducer or other suitable pressure sensor configured or adapted to accurately detect, measure or otherwise determine an applied pressure or force given to the brake pedal.
[0026] To optimize system reliability, the emulator can 44 include more than one distance sensor located at various points on the brake pedal system30 are arranged. Likewise, the emulator can 44 It includes more than one pressure sensor (i.e., force sensor) configured to, for example, output redundant signals to more than one controller to allow for fault tolerance in case of sensor failures. In operation, the controller 32 configured to send a displacement signal (see arrow) 64 ) and a pressure signal (see arrow) 66 ) via path 38 and from the respective sensors 60 , 62 to receive when the brake pedal 42 is operated by a driver. The control 32 processes the displacement and pressure signals 64 , 66 and then sends via the path 40 one or more corresponding command signals 68 to the brake actuators 36 .
[0027] With reference to Fig. The emulator can handle 5. 44 the brake pedal system 30furthermore a basic element 70 include the rotatable directly connected to the fixed structure 46 around the axis of rotation 52 is connected. The damping device 54 and the force induction device 56 Generally, a distinction can be made between the basic element 70 and the connecting element 58 They must be arranged and wear them operatively. During operation, when the brake pedal is pressed... 42 The connecting element is pressed down by a driver. 58 generally closer to the basic element 70 brought forward, and the devices 54 , 56 They are compressed in between, creating the desired "feel" of the brake pedal.
[0028] An example of the force induction device 56 can be an elastically compressible, coiled spring (as shown) with opposite ends resting on the opposing elements 58 , 52resting. Other, non-limiting examples of a force induction device 56 These include an elastomeric foam, a wave spring, and any other device for generating a force in general, as a function of brake pedal displacement. An example of a damping device is... 54 It can be a hydraulic cylinder with at least one internal opening for the flow and exchange of hydraulic fluid between chambers. Such a damping device (and others) can be designed to exert a constant force when a constant velocity is applied to the brake pedal throughout its travel. An example of such a damping device 54 A hydraulic cylinder with a single bore or opening can operate with constant force. Another non-limiting example of a damping device is... 54can be a device designed to apply a force as the pedal travel increases and when the brake pedal is pressed 42 to increase the damping force when the brake pedal is actuated at a constant speed. Such variable-force damping devices can be passive and depend solely on the position and / or displacement of the brake pedal, or they can be active and controlled by the vehicle's steering system. 32 be controlled. An example of a damping device with passive variable force might include a hydraulic cylinder with multiple openings that are individually exposed depending on the brake pedal position. Other non-restrictive examples of a damping device 54The devices may include a friction damper and any other device capable of generating a force generally as a function of the pedal actuation speed. Although shown parallel (i.e., side by side) to each other, it is further conceivable and to be assumed that the orientation of the devices relative to each other can take many forms. For example, the devices may 54 , 56 They lie concentric to each other around a common center line C, which is the axis of rotation 50 and the axis of rotation 52 can cut.
[0029] With reference to Fig. 6 is an example of an emulator 44 with a damping device 54 depicted with an "active variable force". In this embodiment, the force induction device can 56 a concentric arrangement around the damping device 54 It should be an arranged coil spring. The damping device 54This could be a hydraulic cylinder that uses a magnetorheological or electrorheological fluid to actively change the damping force based on, for example, pedal position. Both devices can be configured to compress along the centerline C when the brake pedal is pressed. 42 is pressed down. The force induction device 56 This can also include returning the brake pedal. 42 facilitates movement after the pedal is released by the driver. In this embodiment, the base element can 70 a pole or a frame 72 and an attack 74 include the linkage. 72 can be rotated at one end with the fixed structure 46 It is brought into engagement and is rigidly attached to a base plate at one opposite end. 76 the damping device 54 attached. The stop 74 can be axially between the axis of rotation52 and the base plate 76 the damping device 54 be arranged with respect to the center line C and for the seat of one end of the force induction device 56 from the frame 72 protrude radially outwards.
[0030] The connecting element 58 of the emulator 44 can be a pole or a frame 78 and an attack 80 include the axially from the stop 74 of the basic element 70 is spaced apart and lies opposite this. A first end of the rod 78 can be rotated using the brake pedal 42 on the axis of rotation 50 and are brought into engagement along the midline C and project radially outwards. The linkage 78 can be sealed from the first end by a head plate 82 the damping device 54 and protrude to a distal, opposite second end. The stop80 can be axially between the axis of rotation 50 and the headplate 82 the damping device 54 be arranged in relation to the center line C and from the linkage 78 for the engagement and / or seating of an opposite end of the force induction device 56 protrude radially outwards.
[0031] As already mentioned, the damping device 54 It could be a hydraulic cylinder that uses a magnetorheological or electrorheological fluid to actively change the damping force based on, for example, a pedal position. The damping device 54 can a wall be continuous in the circumferential direction 84 , which can be cylindrical, the base plate 76 , the headstock 82 , a hydraulic or piston head 86 and an electrical element 88 , which may be a coil. The wall 84can be radially from the force induction device or coil spring 56 It is arranged inwards and extends axially between the base and top plates. 76 , 82 . The wall 84 , which are connected to the base and top plates 76 , 82 When combined, it generally defines the boundaries of a hydraulic chamber filled with hydraulic fluid. 90 The piston head 86 is located in the chamber 90 and can be connected to a proximal-distal end of the linkage 78 of the connecting element 58 be intervened. The wall 84 It has a circumferentially continuous surface that points radially inwards and is in sealed contact with the piston head. 86 stands.
[0032] During operation, when the brake pedal is pressed 42 is actuated, the piston head 86 (via the frame) 78 ) in the chamber 90moved back and forth. The chamber 90 is generally through the piston head 86 divided into two separate cavities whose volume changes as the piston head moves back and forth. The damping device 54 also contains an opening 92 in fluid connection between cavities. In one example, the opening can 92 through the piston head 86 can be defined and is connected through this. When the piston head 86 within the chamber 90 As the cavity moves, one cavity expands while the other shrinks. The hydraulic fluid flows through the opening due to the changing volumes between the cavities. 92 and into the enlarged cavity. The resistance to fluid flow through the opening 92 generally generates the damping force of the damping device 54 .
[0033] The resistance to fluid flow through the opening92 The damping coefficient depends at least partially on the viscosity of the hydraulic fluid. The lower the viscosity, the lower the damping coefficient or damping force at a constant flow rate. In the present embodiment, the fluid viscosity can be changed over a given period of time to vary the damping force. To facilitate this active damping force control, the electrical element can be 88 the damping device 54 via a command / control signal from the controller 32 It can be electrically excited. When excited, the electrical element can 88 A magnetic field is generated that alters the molecules of the hydraulic fluid, thereby increasing its viscosity. In one example, the electric element can... 88 on the head 86 in the immediate vicinity of the opening 92 be appropriate. The element 88can be via a hard-wired conductive path, for example a battery and / or the control system 32 , or be excited via a wireless power transmission arrangement (i.e., induction).
[0034] With reference to Fig. 7, a procedure for operating the BBW system can be 26 a first block 100 include preloading target data (see Fig. 4) relative to a damping force coefficient value as a function of the brake pedal travel on the computer-readable and writable storage medium of the computer-based control system 32 includes. Block 102 can the brake pedal 42 be operated by a driver. The block 104 includes sending a brake pedal position signal 64 (see Fig. 2) from a displacement sensor 60 to the control 32 In block 106 The control system processes 32The brake pedal position signal using the target data. At block 108 The control system 32 A command signal is issued based on the brake pedal position and the target data. (In the block) 110 and as a result of the command signal, the electrical coil 88 (see Fig. 6) excites, which changes the viscosity of the hydraulic fluid based on the brake pedal position. In block 112 A reactive damping force is applied against the brake pedal during brake pedal operation. 42 exerted, which changes with varying viscosity based on the brake pedal position.
[0035] Advantages and benefits of the present disclosure include the use of electric current to control the viscosity of electro- / magneto-rheological fluid (i.e., magneto-rheological or electro-rheological fluid) within a damping device (e.g., a hydraulic cylinder that forces fluid through an orifice) to provide pedal damping similar to that of a more conventional braking system. Other advantages may include simulated brake pedal stiffness, damping, and hysteresis similar to that of a vacuum-reinforced system. A further advantage involves a braking system capable of controlling brake pedal damping in real time and a damping device that not only controls the magnitude of a damping force as a function of pedal speed but can also control the damping force (i.e., the damping coefficient) as a function of brake pedal travel to conform to a desired damping coefficient curve.
[0036] While the invention has been described with reference to exemplary embodiments, those skilled in the field will understand that various modifications can be made and individual parts can be replaced by corresponding other parts without deviating from the scope of the invention. Furthermore, many modifications can be made to adapt a particular material situation to the teachings of the invention without deviating from its essential scope. Therefore, it is intended that the invention is not limited to the specific embodiments disclosed, but also includes all embodiments that fall within the scope of the application.
Claims
[1] Brake pedal emulator extending and connected between a support structure and a brake pedal, which is in operative communication with the support structure, the brake pedal emulator comprising: a hydraulic cylinder with a magneto-rheological hydraulic fluid and an electrical element configured to carry an electric current to control the viscosity of the magneto-rheological hydraulic fluid and thereby control a first force exerted by the hydraulic cylinder when it is actuated. [2] Brake pedal emulator according to claim 1, further comprising: a force induction device that engages between the support structure and the brake pedal and is designed and arranged to apply a second force to the brake pedal, which varies as a function of the brake pedal travel. [3] Brake pedal emulator according to claim 2, wherein the first force is a damping force which changes as a function of at least the brake pedal velocity. [4] Brake pedal emulator according to claim 2, wherein the force induction device is a helical spring. [5] Brake pedal emulator according to claim 4, wherein the helical spring is arranged concentrically around the hydraulic cylinder. [6] Brake pedal emulator according to claim 5, wherein the coil spring and the hydraulic cylinder are compressible along a common centerline. [7] Brake pedal emulator according to claim 6, further comprising: a base element that is directly rotatably engaged with the support structure on a first axis of rotation and rigidly engaged with the hydraulic cylinder; and a connecting element that is directly rotatable with the brake pedal on a second axis of rotation and directly engages with a reciprocating head of the hydraulic cylinder, and in which the coil spring for compression between the base element and the connecting element is located when the brake pedal is actuated. [8] Brake-by-Wire (BBW) system for a vehicle, comprising: a brake pedal in operative connection with a supporting structure; and a brake pedal emulator designed and arranged to exert a damping force on the brake pedal and including a hydraulic cylinder with an electrical coil and a hydraulic fluid configured to change viscosity when the electrical coil is energized. [9] BBW system according to claim 8, further comprising: a computer-based control system configured to control the electric current through the electric coil in order to control the damping force in real time. [10] BBW system according to claim 9, wherein data associated with a damping coefficient curve as a function of the brake pedal position are stored in a computer-readable storage medium of the controller and the controller is configured to control the damping force at least partially on the damping coefficient curve.