System and method for controlling a brake with variable braking modes

Abstract

System for controlling a brake with variable braking modes, comprising: an operating part (10) provided to enable a driver to selectively input one of a plurality of predetermined braking characteristic modes; a brake input detector (15) for detecting a brake pedal operation variance of the driver; and a control device (20) which receives a mode selection signal from the operating part (10) to detect the braking characteristic mode selected by the driver and then controls a wheel brake to generate a predetermined pattern of braking force in the braking characteristic mode selected by the driver based on the brake pedal operation variance detected by the brake input detector (15), characterized in that the brake input detector (15) also detects a brake pedal operating force and the predetermined pattern is also generated based on the brake pedal operating force detected by the brake input detector (15), and the system further comprises a pedal force variation device (41) which adjusts a pedal stroke of a pedal simulator (42) with respect to a pedal force of the driver in accordance with a control signal of the control device (20), wherein the control device (20) receives the mode selection signal from the operating part (10) to recognize the braking characteristic mode selected by the driver, and then controls the pedal force varying device (41) to vary the pedal stroke of the pedal simulator (42) with respect to the driver's pedal force according to the braking characteristic mode, so that different braking forces are generated depending on the selected braking characteristic mode even when an equal pedal force is applied to the pedal.

Description

[0001] The invention relates to a system and method for controlling a brake for a vehicle, and more particularly to a system and method for controlling a brake for a vehicle that can provide customized braking characteristics for drivers with different driving habits and can improve the marketability of a vehicle.

[0002] Generally, a vehicle's brake decelerates or stops the vehicle during operation or holds the vehicle in a stationary state. When the brake is applied, the vehicle's kinetic energy is converted into heat energy through mechanical friction, and the resulting frictional heat is released into the atmosphere.

[0003] Vehicle brakes are divided into drum-type hydraulic brakes and disc-type hydraulic brakes. In a disc-type hydraulic brake, braking force is generated by rotating a disc with a wheel instead of a drum, and the brake is applied forcefully by a brake pad.

[0004] However, since hydraulic brakes require mechanical components, the structure of hydraulic lines and components for controlling hydraulic pressure connected to a brake pedal in front of a driver's seat is complicated.

[0005] Accordingly, electromechanical brakes (EMB) have been used recently to simplify the structure of the braking device.

[0006] Unlike typical hydraulic brakes, EMBs refer to brakes that achieve stopping force by pressing a brake pad using a mechanism driven by an electric motor.

[0007] Typical EMBs have an actuator that includes a motor that rotates to apply or release braking. The motor's torque applies pressure to the brake pad, allowing the disc to be compressed and rubbed by friction. EMBs detect a driver's braking intent through the brake pedal and then control the braking pressure of a wheel using the motor.

[0008] Since EMBs, as next-generation braking concepts, have a fast response speed and enable precise control compared to hydraulic brakes, they are expected to be preferred for environmentally friendly vehicles, such as electric vehicles.

[0009] EMBs can also be implemented in combination with hydraulic brakes. For example, a hydraulic brake and an EMB can be applied to the front and rear wheels. Compared to a system using only a hydraulic brake, the combined system of EMB and hydraulic brake has a simple structure and excellent braking force response with easy braking force control.

[0010] An electronic brake system (EBB) can also be implemented, with EMBs mounted on the front and rear wheels. The EBBB system performs braking by using electric brake calipers located on the front and rear wheels that can hold the disc in accordance with signals from a control device.

[0011] An electro-hydraulic brake (EHB) system is another form of BBW system and differs from the EMB. In the EHB system, a control unit receives signals from a pedal travel sensor and a hydraulic sensor in a master cylinder to detect the driver's braking intention, requests deceleration, and controls the hydraulic pressure of an accumulator via a solenoid valve to apply hydraulic braking to the wheels.

[0012] Because the BBW system transmits the driver's braking intention via electrical signals, there is no mechanical connection between the brake pedal and the wheel, allowing independent and precise control of the braking force at each wheel of a vehicle. Furthermore, braking force control is easy, braking distances can be shortened, and braking stability can be increased.

[0013] The BBW system uses a pedal simulator to create a hydraulic pedal-like feel using hysteresis characteristics. The pedal simulator recreates the feel of a pedal, such as an existing hydraulic brake, when a driver applies the pedal and assists the driver's braking effort by generating a pedal repulsion force that counteracts the brake effort.

[0014] The BBW system is more advanced than typical braking devices, where the characteristics of the rider's pedal force (force applied to the pedal) versus the braking force have a single mode.

[0015] For example, when a driver presses the brake pedal with a force A1, the pedal variance (pedal depth, pedal travel, and pedal stroke) caused by the force A1 is substantially equal to A2. When the pedal variance is equal to A2, the braking force of the brake device corresponding to the pedal variance substantially has a predetermined value A3.

[0016] When the pedal effort variance is constant, a constant braking force is always generated to meet the driver's desired deceleration. The pedal stroke corresponding to a specific pedal force, the driver's desired deceleration, and the braking force corresponding to the pedal stroke are determined in a dedicated single mode. Likewise, the braking force variation patterns corresponding to the pedal force and the pedal effort variance are determined in a single mode.

[0017] Therefore, according to the prior art, since the characteristics of the braking feeling of a vehicle cannot be changed according to the pedal force in a predetermined single mode and the pedal force or braking force characteristics cannot be changed according to the driver's habits, sufficient braking force cannot be obtained by, for example, women or elderly men.

[0018] It is also difficult to create a sporty braking feeling for a driver who likes sporty driving.

[0019] Systems for adjusting braking characteristics are known from DE 693 07 419 T2 and DE 100 50 466 A1. A system for selecting a brake pedal actuation variance / braking force characteristic is known from DE 10 2007 011 054 A1. A system for automatically correcting braking characteristics is known from DE 600 36 269 T2. A system for adjusting braking characteristics by actuating the brake pedal while stationary is known from DE 10 2004 048 605 B3. A system for controlling a brake with variable braking modes according to the preamble of claim 1 and a method for controlling a brake with variable braking modes according to the preamble of claim 6 are known from DE 199 51 119 A1.

[0020] The object of the invention is to provide a system and a method for controlling a brake for a vehicle, which provide customer-specific braking characteristics for different driving habits and ultimately improve the marketability of a vehicle.

[0021] This object is achieved by a system for controlling a brake with variable braking modes according to claim 1 and by a method for controlling a brake with variable braking modes according to claim 6. Advantageous embodiments are the subject of the dependent claims.According to the invention, a brake control system with variable braking modes comprises: an operating part provided to allow a driver to selectively input one of a plurality of predetermined braking characteristic modes, a braking input detector for detecting a brake pedal operation variance or a brake pedal operation force of the driver, and a controller that receives a mode selection signal from the operating part to detect the braking characteristic mode selected by the driver and then controls a wheel brake to generate a predetermined pattern of braking force in the braking characteristic mode selected by the driver based on the brake pedal operation variance and the brake pedal operation force detected by the braking input detector.

[0022] According to the invention, a method for controlling a brake with variable braking modes comprises: selectively inputting one of a plurality of predetermined braking characteristic modes by operating an operating part by a driver, receiving a mode selection signal from the operating part by a controller to detect the braking characteristic mode selected by the driver, and controlling a wheel brake to generate a predetermined pattern of braking force in the braking characteristic mode selected by the driver based on a brake pedal operation variance and a brake pedal operation force detected by a brake input detector.

[0023] The invention is explained in more detail with reference to the drawing. The drawing shows: Fig. 1 is a schematic diagram of a configuration of a braking device with a control system according to an embodiment of the invention; Fig. 2 is a diagram illustrating the braking characteristics between the pedal force and the deceleration according to the driver selection mode in a control method according to an embodiment of the invention; Fig. 3 is a diagram illustrating the variation of the pedal travel according to the pedal force for each mode in a control method according to another embodiment of the invention; and Fig. 4 is a view illustrating a mode display part according to an embodiment of the invention.

[0024] It is understood that the term “vehicle” includes general motor vehicles, such as passenger cars, including sport utility vehicles (SUVs), buses, trucks, various commercial vehicles, watercraft, including a variety of boats and ships, aircraft, and the like, as well as hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles, and other alternative fuel vehicles (e.g., fuels derived from feedstocks other than petroleum).

[0025] The system and method for controlling a brake for a vehicle can create optimal braking force or pedal force characteristics preferred by a driver. The system and method for controlling a brake are configured to achieve a braking force or pedal force (pedal feel) corresponding to the braking characteristic mode selected by a driver.

[0026] Braking input from a driver can be performed using a brake pedal. When the driver selects a braking characteristic mode and depresses the brake pedal, the braking force pattern or pedal feel can vary according to the selected mode to provide optimal braking feel for the driver.

[0027] Since different braking force and pedal force characteristics can be achieved according to the selected mode, anyone, including women or elderly men, can easily perform the braking operation and achieve a desired braking feeling according to their habits.

[0028] Fig. 1 shows a configuration of a braking device with a control system according to an embodiment of the invention. Fig. 2 is a diagram illustrating the braking characteristics between the pedal force and the deceleration according to the driver selection mode, ie, the braking characteristic mode selected by a driver in a control method according to an embodiment of the invention.

[0029] A system for controlling a brake may include an operating part 10 for a driver to selectively input one of a plurality of predetermined braking characteristic modes.

[0030] The operating part 10 may be arranged around the driver's seat, such as on a center dashboard, a console, a steering wheel, a multifunction switch, or a door panel, whereby the driver can easily operate the operating part 10.

[0031] With reference to the Fig. 2 and Fig. 3, the braking characteristic mode may be predetermined by a plurality of modes having different braking force characteristics or pedal force characteristics by the driver's brake input operation, ie, by stepping on the brake pedal to stop the vehicle.

[0032] As in Fig. 1, the operating part 10 may be configured to include a plurality of buttons 11, 12, and 13. Instead of the button, the operating part 10 may be redesigned into operating devices or input devices in a vehicle, such as a button, switch, or touch screen.

[0033] When the driver operates the operating part 10 to select a mode, a mode selection signal of the operating part 10 selected by the driver may be supplied to a controller 20, and then the controller 20 may recognize the mode selected by the driver.

[0034] The brake control system may include a brake input detector 15 for detecting a brake pedal operation variance or a brake pedal operation force from a driver. The brake input detector 15 may include a pedal stroke sensor for detecting a brake pedal stroke (pedal travel) or a pressure sensor for detecting a pedal force (force applied to the brake pedal) from a driver.

[0035] The controller 20 may comprise a typical brake control device for controlling the operation of the braking device in a vehicle according to the braking input from a driver. As with a typical braking device, when a driver operates the brake pedal, the controller 20 may calculate a driver's desired deceleration using a map based on the brake pedal operation variance (pedal stroke or pedal travel) or brake pedal operation force (pedal force) detected by the brake input detector 15, and calculate a target braking force corresponding to the driver's desired deceleration, and then control the generation of the braking force of a wheel brake 30 based on the target braking force.

[0036] Therefore, the generation of the braking force of the wheel brake 30, which is controlled according to the brake pedal operation variance or the brake pedal operation force, is no different from the prior art. However, in this embodiment, when a driver performs the braking input for the mode selected by the driver, the controller 20 can control the braking force characteristics according to the brake pedal operation variance, the brake pedal operation force, or the pedal force characteristics upon the brake pedal operation by distinguishing between the modes.

[0037] Fig. Figure 2 illustrates the braking force characteristics differentiated between modes by a software process, showing the braking force characteristics for each mode. The pedal force versus driver-input deceleration graph may be an example of a map for calculating driver-input deceleration based on a driver's brake pedal operation variance or brake pedal operation force detected by the brake input detector 15.

[0038] Fig. Figure 2 shows a map in which the driver's desired deceleration is differentiated by each mode according to the operating force / operating pressure, i.e., the pedal force exerted by a driver. Since the pedal stroke is determined according to the pedal force, the driver's desired deceleration according to the pedal stroke can also be determined as shown in the diagram of Fig. 2.

[0039] When the driver's desired deceleration is determined from the deceleration map of the pedal stroke-related driver's desired deceleration based on the pedal stroke (brake pedal operation variance) detected by the pedal stroke sensor, and a target braking force that can meet the driver's desired deceleration is calculated, a method of performing control of a brake to generate the target braking force can also be used.

[0040] Therefore, the map in which the driver's desired deceleration is predetermined by the brake pedal operation variance (pedal stroke or pedal travel) or the brake pedal operation force for each mode may be stored in advance in the controller 20, so that the driver's desired deceleration for each mode can be calculated based on the brake pedal operation variance or brake pedal operation force detected and inputted by the brake input detector 15.

[0041] Fig. Figure 2 shows three braking characteristic modes (light, normal, and sport). The map can be configured to differentiate the gradient (rate of change) of the driver's desired braking with respect to pedal force (force applied by a driver to the pedal) between three modes.

[0042] Alternatively, the map can be configured such that the magnitude of the driver's desired deceleration is always differentiated between three modes according to the pedal force. Here, the pedal force can be detected by a pressure sensor as the brake input detector 15, but instead of the pedal force, a pedal stroke value can be detected by the pedal stroke sensor.

[0043] In light mode, the rate of change of deceleration with respect to the variation of a driver's input pedal force (pedal stroke) may be relatively larger than that in other modes, and similarly, the magnitude of driver's desired deceleration corresponding to the same pedal force may always be larger than that in other modes.

[0044] With reference to Fig. 2 In light mode, although a driver operates the brake pedal with a smaller force than that in other modes, a larger braking force can be generated because the driver's desired deceleration with respect to the same pedal force is larger than that in other modes.

[0045] The gradient of the line in normal mode can be set smaller than that in easy mode, and the gradient of the line in sport mode can be set smaller than that in normal mode.

[0046] Similarly, the magnitude of the driver's desired deceleration with respect to the same pedal force in normal mode can always be set smaller than that in light mode, and the magnitude of the driver's desired deceleration with respect to the same pedal force in sport mode can always be set smaller than that in normal mode.

[0047] The number of braking characteristic modes can be changed and is not limited to the Fig. 2. Accordingly, more different modes can be set with respect to braking force characteristics.

[0048] With reference to Fig. 1, the braking device may comprise a wheel brake 30 which generates a braking force corresponding to the brake pedal operation variance or the brake pedal operation force by performing hydraulic control (in the case of the hydraulic brake or the EHB) or electrically operated control (in the case of the EMB) according to the control signals of the control device 20.

[0049] Here, the mechanical configuration of the wheel brake 30 may be the same as that of a typical wheel brake. Likewise, there is no difference in the process of controlling the hydraulic pressure (e.g., controlling the hydraulic pressure of a wheel cylinder / hydraulic brake caliper) applied to the wheel brake 30 via a hydraulic valve 31 based on the target braking force, or performing the electric actuation control (motor), so that a braking force can be generated in the wheel brake 30 of each wheel according to the brake pedal operation variance or the brake pedal operation force of a driver.

[0050] As in Fig. As shown in Figure 2, the driver's desired deceleration according to the mode can be calculated from the brake pedal operation variance or the brake pedal operation force (detected by the brake input detector) according to the predetermined braking force characteristics for each mode. Based on the driver's desired deceleration according to the selected mode, the generation of the braking force of the wheel brake 30 can be controlled. Accordingly, there is a significant difference in that the generated braking force and the braking force characteristics (variation pattern of the braking force according to the pedal operation variance or pedal operation force) vary with the mode.

[0051] When a driver selects a desired mode, the controller 20 can recognize the selected mode to generate a specific braking force for each mode according to the pedal operation variance or pedal operation force. Specifically, since the wheel brake 30 is controlled to generate different braking forces (hydraulic control or electrically actuated control), even if the pedal operation variance or pedal operation force is the same according to the selected modes, different braking force characteristics can be achieved according to the modes.

[0052] Fig. 3 is a diagram showing braking characteristics representing a relationship between the pedal force and the pedal stroke (pedal travel) according to the driver selection mode, that is, the braking characteristic mode selected in a system and method for controlling a brake according to another embodiment of the invention, showing a variation of the pedal travel according to the pedal force for each mode.

[0053] In the case of Fig. 2, the control device 20 can vary the braking force generated in the wheel brake 30 according to each mode even if the same pedal force is applied by a driver, so that the braking force characteristics can be differentiated according to the mode selected by the driver.

[0054] On the other hand, in another embodiment of Fig. 3, the control device 20 can recognize the braking characteristic mode selected by a driver from a mode selection signal input from the operating part 10, and then vary the pedal force (pedal feel) characteristics for each mode instead of the braking force characteristics.

[0055] That is, by controlling hardware factors in a brake pedal unit according to the braking characteristic mode selected by the driver, a driver can feel different forces applied to the brake pedal. The pedal stroke and the variation pattern thereof according to the pedal force can be controlled to be different according to each mode. Therefore, even when the same pedal force is applied, different braking forces can be generated according to the selected modes.

[0056] In this embodiment, the control system may further comprise a pedal force variation device 41 of a pedal simulator 42 that adjusts the pedal stroke pattern with respect to the driver's pedal force according to a control signal output from the control device 20 for each mode. The pedal force variation device 41 is in Fig. 1 shown.

[0057] The pedal force variation device 41 can vary the pedal force characteristics according to the control signal of the control device 20, ie the pedal force stroke characteristics according to the Fig. 3. The pedal force varying device 41 can control the repulsive force against the pedal force in the pedal feel determining pedal simulator 42 to vary the pedal stroke when a specific pedal force is applied according to the mode. Therefore, the pedal force varying device 41 can serve as a device that varies the pedal force to be applied to apply a desired braking force according to the mode.

[0058] To generate a desired braking force, the pedal force can be varied by a driver. Likewise, as in Fig. 3, the pedal stroke can be varied even if the same pedal force is input to the pedal simulator 42 according to the selected mode.

[0059] The pedal force varying device 41 may have a structure in which the pedal force varies by changing the shear force of magnetorheological (MR) and electrorheological (ER) fluids by means of a pedal simulator, that is, a structure in which the fluid flow rate and the hydraulic pressure of the pedal simulator vary by changing the inlet area of ​​an orifice of a motor control type, or a structure in which the fluid flow rate and the hydraulic pressure of the pedal simulator vary by means of a solenoid valve.

[0060] When the pedal force varying device 41 is used, the pedal force to be applied to perform the same pedal stroke and the braking force can vary with each mode.

[0061] Since the pedal stroke varies according to the pedal force with different modes, the pedal stroke may be different for each mode even if a rider applies the same force to the pedal.

[0062] If the pedal stroke of the brake pedal unit varies with the same applied force, the braking force may vary with the mode due to a difference between the pedal strokes.

[0063] In this case, when the brake input detector 15 detects the pedal stroke and inputs the pedal stroke to the controller 20, the controller 20 can calculate the driver's desired deceleration according to the detected pedal stroke and then calculate a target braking force. Likewise, the controller 20 can control the wheel brake 30 to generate the target braking force.

[0064] Accordingly, since the pedal stroke is detected by the brake input detector 15, that is, the pedal stroke sensor varies with the mode, there may be a difference in the generated braking force when the controller 20 controls the wheel brake 30 based on the information of the pedal stroke sensor.

[0065] While the variation pattern of the pedal stroke according to the pedal force differs between the modes in a hardware method that controls the pedal force varying device 41 of the pedal simulator 42, the braking force of the wheel brake 30 may vary with the mode even if a driver applies the same pedal force.

[0066] Therefore, even though a lower pedal force is applied according to the mode, a large braking force can be generated. Similarly, a case may arise where a driver must apply a greater pedal force to generate the same braking force.

[0067] Fig. 3 shows three braking characteristic modes (light, normal and sporty). As in Fig. As shown in Figure 3, the pedal stroke change rate in the pedal simulator with respect to the pedal force (force applied by a driver to the pedal) can be distinguished between three modes.

[0068] Alternatively, a map may be configured such that the size of the pedal stroke is always differentiated between three modes according to the pedal force. In this case, the pedal stroke may be a value set in a hardware method by the pedal force variation device 41 of the pedal simulator 42 such that it varies with the mode.

[0069] In light mode, the rate of change of pedal stroke with respect to the variation of pedal force (pedal stroke) input by a rider may be relatively larger than that in other modes, and similarly, the size of pedal stroke corresponding to the same pedal force may always be larger than that in other modes.

[0070] Accordingly, in the light mode, although a driver operates the brake pedal with a smaller force than that in other modes, a larger braking force can be generated because the pedal stroke in the pedal simulator is larger than that in other modes with respect to the same pedal force.

[0071] The gradient of the line in normal mode can be set smaller than that in easy mode, and the gradient of the line in sport mode can be set smaller than that in normal mode.

[0072] Similarly, the size of the pedal stroke with respect to the same pedal force in the normal mode can always be set smaller than that in the light mode, and the size of the pedal stroke with respect to the same pedal force in the sport mode can always be set smaller than that in the normal mode.

[0073] The number of braking characteristic modes can be changed and is not limited to the Fig. 3. Accordingly, more different modes can be set with respect to braking force characteristics.

[0074] Fig.4 is a view showing a mode display part 14 for displaying the current braking characteristic mode when a driver operates the operating part 10.

[0075] Therefore, the braking force of a braking device generated in response to a driver's pedal force can be differentiated according to a mode selected by the driver, and customized braking characteristics can be provided for drivers with different habits, thereby improving the marketability of the vehicle.

Claims

[1] A system for controlling a brake with variable braking modes, comprising: an operating part (10) provided to enable a driver to selectively input one of a plurality of predetermined braking characteristic modes; a brake input detector (15) for detecting a brake pedal operation variance of the driver; and a control device (20) which receives a mode selection signal from the operating part (10) to detect the braking characteristic mode selected by the driver and then controls a wheel brake to generate a predetermined pattern of braking force in the braking characteristic mode selected by the driver based on the brake pedal operation variance detected by the brake input detector (15), characterized by , that the brake input detector (15) also detects a brake pedal operating force and the predetermined pattern is also generated based on the brake pedal operating force detected by the brake input detector (15), and the system further comprises a pedal force variation device (41) which adjusts a pedal stroke of a pedal simulator (42) with respect to a pedal force of the driver in accordance with a control signal of the control device (20), wherein the control device (20) receives the mode selection signal from the operating part (10) to recognize the braking characteristic mode selected by the driver, and then controls the pedal force varying device (41) to vary the pedal stroke of the pedal simulator (42) with respect to the driver's pedal force according to the braking characteristic mode, so that different braking forces are generated depending on the selected braking characteristic mode even when an equal pedal force is applied to the pedal. [2] The system of claim 1, wherein the control device (20) is configured such that a driver's desired deceleration varies according to the brake pedal operation variance and the brake pedal operation force with the braking characteristic mode. [3] The system according to claim 2, wherein the braking characteristic mode is provided in a plurality in which a rate of change of the driver's desired deceleration varies with respect to the brake pedal operation variance or the brake pedal operation force, or an amount of the driver's desired deceleration is always variable in accordance with the brake pedal operation variance or the brake pedal operation force. [4] The system according to claim 1, wherein the braking characteristic mode is provided in a plurality in which a change rate of the pedal stroke of the pedal simulator (42) varies with respect to the pedal force of the driver or a size of the pedal stroke is always variable according to the pedal force of the driver. [5] The system according to claim 1, further comprising a mode display part (14) for displaying the braking characteristic mode selected by the driver. [6] A method for controlling a brake with variable braking modes, comprising: selectively inputting one of a plurality of predetermined braking characteristic modes by operating an operating part (10) by a driver; Receiving a mode selection signal from the operating part (10) by a control device (20) to detect the braking characteristic mode selected by the driver; and Controlling a wheel brake to generate a predetermined pattern of braking force in the driver-selected braking characteristic mode based on a brake pedal operation variance detected by a brake input detector (15), characterized by , that the predetermined pattern is also generated based on a brake pedal operating force detected by the brake input detector (15), and the control device (20) receives the mode selection signal from the operating part (10) to detect the braking characteristic mode selected by the driver, and then controls a pedal force varying device (41) to vary a pedal stroke of a pedal simulator (42) with respect to the driver's pedal force according to the braking characteristic mode, so that different braking forces are generated depending on the selected braking characteristic mode even when an equal pedal force is applied to the pedal. [7] The method according to claim 6, wherein the control device (20) is configured such that a driver's desired deceleration varies according to the brake pedal actuation variance and the brake pedal actuation force with the braking characteristic mode. [8] The method according to claim 7, wherein the braking characteristic mode is provided in a plurality in which a rate of change of the driver's desired deceleration varies with respect to the brake pedal operation variance or the brake pedal operation force, or a magnitude of the driver's desired deceleration is always variable according to the brake pedal operation variance or the brake pedal operation force. [9] The method according to claim 6, wherein the braking characteristic mode is provided in a plurality in which a change rate of the pedal stroke of the pedal simulator (42) varies with respect to the pedal force of the driver or a size of the pedal stroke is always variable according to the pedal force of the driver.

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