Patent Publication Number: US-2021170998-A1

Title: Braking system with configurable force feedback and related methods

Description:
TECHNICAL FIELD 
     The disclosure herein relates to a braking system. 
     TECHNICAL BACKGROUND 
     Two-axle vehicles are fitted with hydraulic systems that have two brake circuits, thus ensuring that, if one of the two brake circuits fails, the vehicle can still be braked by means of the other brake circuit. In general, the wheel brakes are associated with the brake circuits in a diagonally split arrangement, in which a brake circuit acts on one front wheel and the respective diagonally opposite rear wheel. The two brake circuits are connected to a master brake cylinder, to which a brake pedal actuated by a driver to build up a corresponding brake pressure in the two brake circuits is coupled. 
     To implement a “brake-by-wire” brake system with a fallback level, a displacement simulator, an electrically controllable pressure source, two block valves (also referred to as connecting valves) and two circuit block valves are required in addition to the brake-pedal-actuated master brake cylinder. For the “brake-by-wire” operating mode, the wheel brakes are separated from the master brake cylinder by means of the block valves, while the wheel brakes are connected via the circuit block valves to a controllable pressure source common to both brake circuits or to a respective controllable pressure source provided for each of the brake circuits. 
     Such brake systems comprise a large number of hydraulic lines, which are interconnected by the valves in different ways, and therefore the occurrence of leaks cannot be excluded. Particularly in the case of “brake-by-wire” brake systems, there is the disadvantage that haptic feedback signals from the brake circuits are not transmitted to the brake pedal when said brake circuits are separated from the master brake cylinder. However, such haptic feedback is desired as a comfort feature. Therefore, a displacement simulator is connected in parallel with the master brake cylinder, said simulator imparting to the driver a pedal characteristic of a conventional brake system when the brake pedal is actuated if the wheel brakes are supplied with pressure medium from the pressure medium reservoir by the electrically controllable pressure source to generate a brake pressure. However, the disadvantage here is that it is not possible to achieve haptic feedback signals which indicate to the driver the safety and integrity of the brake system. This relates, for example, to increased volume inclusions, such as air or leaks, which are indicated in conventional brake systems by the absence of force feedback at the brake pedal. Mismatches in the volumes of a “brake-by-wire” brake system must therefore be detected electronically. 
     In addition, such brake systems comprise a large number of hydraulic lines, which are interconnected by the valves in different ways. The method in which the valves are connected prevent the feedback from road noise under braking from reaching the driver. By controlling the perceived driver force, the brake system can provide a more accurate feedback of road noise and situational events i.e ABS events. 
     What is needed is a way to provide adjustable force feedback for the driver. 
     SUMMARY 
     A braking system including a first performance mode and a second performance mode, the braking system includes a pedal assembly coupled with a master cylinder, the pedal assembly having a feedback force, the pedal assembly having two or more activated positions and an inactivated position, a pedal feel simulator coupled with the pedal assembly, the pedal feel simulator configured to apply force feedback to the pedal assembly, the pedal feel simulator coupled with a simulator valve, the simulator valve configured to hold pressure within the pedal feel simulator when the braking system is in the second performance mode, a plurality of wheel brakes hydraulically or non hydraulically coupled with the master cylinder. 
     In one or more embodiments, the first performance mode is a default mode and the second performance mode is an alternate mode which provides a driver with a shorter travel and higher force pedal feel characteristic than in the default mode. 
     In one or more embodiments, the simulator valve is an analog valve. 
     In one or more embodiments, the braking system further includes a check valve coupled with the pedal feel simulator. 
     In one or more embodiments, the check valve is hydraulically connected in parallel with the analog valve. 
     In one or more embodiments, the braking system further includes a second simulator valve coupled with the pedal feel simulator. 
     In one or more embodiments, the second simulator valve is an analog valve. 
     In one or more embodiments, the second simulator valve is a digital valve. 
     In one or more embodiments, the feedback force is greater in the second performance mode than in the first performance mode. 
     In one or more embodiments, the pedal feel simulator is configured to apply force feedback to the pedal assembly via the master cylinder. 
     A method is disclosed herein and includes selecting a driving performance mode from at least one of a first performance mode and a second performance mode for a braking system, the braking system having a pedal assembly coupled with a master cylinder, the pedal assembly having a feedback force, the pedal assembly having two or more activated positions and an inactivated position, a pedal feel simulator coupled with the pedal assembly, the pedal feel simulator configured to apply force feedback to the pedal assembly, the pedal feel simulator coupled with a simulator valve, the simulator valve configured to hold pressure within the pedal feel simulator when the braking system is in the second performance mode, a plurality of wheel brakes hydraulically coupled with the master cylinder, selecting a pedal response force based on performance mode selection, where the pedal response force having a first pedal response force for the first performance mode and a second pedal response force for the second performance mode, and the first pedal response force is different than the second pedal response force, and configuring the pedal feel simulator to have the selected pedal response force. 
     In one or more embodiments, selecting the driving performance mode from at least one of the first performance mode and the second performance mode includes selecting from a comfort mode and a sport mode. 
     In one or more embodiments, the method further includes pre-filling fluid pressure within the pedal feel simulator. 
     In one or more embodiments, configuring the pedal feel simulator to have the selected pedal response force includes opening an analog valve connected with the pedal feel simulator. 
     In one or more embodiments, configuring the pedal feel simulator assembly to have the selected pedal response force includes opening at least one of a first valve and second valve connected with the pedal feel simulator. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a schematic diagram of a braking system, as constructed in accordance with one or more embodiments. 
         FIG. 2  illustrates a schematic diagram of a braking system, as constructed in accordance with one or more embodiments. 
     
    
    
     These and other embodiments, aspects, advantages, and features of the present invention will be set forth in part in the description which follows and will become apparent to those skilled in the art by reference to the following description of the invention and referenced drawings or by practice of the invention. The aspects, advantages, and features of the invention are realized and attained by the instrumentalities, procedures, and combinations particularly pointed out in the appended claims and their equivalents. 
     DETAILED DESCRIPTION 
     The following detailed description includes references to the accompanying drawings, which form a part of the detailed description. The drawings show, by way of illustration, specific embodiments in which the apparatus may be practiced. These embodiments, which are also referred to herein as “examples” or “options,” are described in enough detail to enable those skilled in the art to practice the present embodiments. The embodiments may be combined, other embodiments may be utilized, or structural or logical changes may be made without departing from the scope of the invention. The following detailed description is, therefore, not to be taken in a limiting sense and the scope of the invention is defined by the appended claims and their legal equivalents. 
       FIG. 1  shows an electronically controlled hydraulic or non-hydraulic braking system  100  for a vehicle having a first performance mode and a second performance mode, or a default performance mode and an alternate performance mode. In one or more embodiments, the first performance mode is a comfort mode and the second performance mode is a sport mode. In one or more embodiments, the braking system has a first brake circuit  110  and a second brake circuit  112 . A brake control unit generates control signals for the valves of the two brake circuits  110  and  112  as output signals on the basis of sensor signals as input signals. 
     The first brake circuit  110  for a front left-hand wheel  130  (FL) and a rear right-hand wheel  132  (RR) is connected via a block valve  120  to a master brake cylinder  116 . The second brake circuit  112  for a front right-hand wheel  134  (FR) and a rear left-hand wheel  136  (RL) is likewise connected to the master brake cylinder  116  via a block valve  122 . Wheel brakes  138 ,  140  and  142 ,  144  of the wheels  130 ,  132  and  134 ,  136 , respectively, are connected by respective hydraulic lines to the first brake circuit  110  and the second brake circuit  112 . 
     The braking system  100  includes a pedal assembly  108  coupled with a master brake cylinder  116 . The pedal assembly  108  has a feedback force, and the pedal assembly  108  has two or more activated positions and an inactivated position. The master brake cylinder  116  can be actuated by a brake pedal assembly  108 , a pedal feel simulator  150  interacting with the master brake cylinder  116 , a pressure medium reservoir  102  connected to the master brake cylinder  116 , an electrically controllable pressure source  192 , which is designed as an electrohydraulic actuator with an electric motor  190  as a drive motor. The pedal feel simulator  150  is coupled with the pedal assembly  108 , where the pedal feel simulator is configured to apply force feedback to the pedal assembly  108 . The pedal feel simulator  150  is coupled with a simulator valve  152 , where the simulator valve  152  is configured to trap pressure within the pedal feel simulator  150  when the braking system is in the second performance mode. In one or more embodiments, the simulator valve is an analog valve. In one or more embodiments, a check valve  154  is coupled with the pedal feel simulator  150 . In one or more embodiments, the check valve  154  is hydraulically connected in parallel with the analog valve. In one or more embodiments, the braking system  100  further includes a second simulator valve  156 , as shown in  FIG. 2 . 
     In one or more embodiments, the simulator valve  152  is modified to hold fluid pressure by increasing check valve spring force, for example by using an analog valve to increase pressure adjustability and reduce brake noise, vibration and harshness (NVH) during actuation. Initial activation of a second performance mode, such as sport mode, will allow the driver to actuate the pedal and fill the simulator. Upon pedal release, the simulator valve  152  will close and hold the desired prefill pressure in the simulator. Subsequent pedal applications while in this performance mode will now have a high pedal force feedback with respect to pedal travel, giving a sporty pedal feel. 
     The braking system further includes controllable pressure modulation devices with wheel brakes  138 ,  140  for a front left-hand wheel  130  (FL) and a rear right-hand wheel  136  (RL) and with wheel brakes  142 ,  144  for a front right-hand wheel  134  (FR) and a rear left-hand wheel  136  (RL), and a control unit. 
     An inlet valve and an outlet valve  124 ,  128  in each case form a pressure modulation device for the two wheel brakes  138 ,  140  of a first brake circuit  110 , and an inlet valve and an outlet valve  126 ,  130  in each case form a pressure modulation device for the two wheel brakes  142 ,  144  of a second brake circuit  112 . 
     In a “brake-by-wire” operating mode, the inlet valves  124  and  128  are connected via a circuit block valve  170  and  172 , respectively, to the electrically controllable pressure source  192  for generating a system pressure. To measure the system pressure generated by the pressure source  192 , a pressure sensor  196  is arranged on the high-pressure side thereof. Furthermore, each outlet valve  128 , 130  is connected to the pressure medium reservoir  102 . 
     The master brake cylinder  116  is embodied as a dual-circuit tandem master cylinder and is connected to the pressure medium reservoir  102 . To form a fall back plane of the “brake-by-wire” braking system  100 , the master brake cylinder  116  can be connected to the wheel brakes  138 ,  140  of the first brake circuit  110  via a block valve  120  and to the wheel brakes  142 ,  144  of the second brake circuit  112  via another block valve  122 . The brake pressure generated in this case is measured by a pressure sensor  188 . Using the block valves  170  and  172 , the hydraulic connection between the master brake cylinder  116  and the first and second brake circuit  110  and  112  is divided in the “brake-by-wire” operating mode. 
     A displacement sensor  198  is utilized to determine the extent of a pedal actuation brought about by the driver, i.e. the movement of a piston rod of the wheel brake cylinder  116 , said piston rod being connected to the brake pedal assembly  108 , is determined and represents a braking demand of the driver. The pedal feel simulator  150  is coupled hydraulically to the master brake cylinder  116  and simulates a haptic feedback corresponding to the brake pressure generated, i.e. a corresponding pedal feel, to the brake pedal assembly  108 . 
     The electrically controllable pressure source  192  is designed, for example, as a single-circuit electrohydraulic actuator, the piston  194  of which can be actuated by an electric motor  190  via a rotation/translation mechanism. The piston  194  delimits a pressure space, which is connected to the pressure medium reservoir  102  in order to draw in pressure medium. The position of the piston  194  is determined from the rotor position of the electric motor  190 , which is determined by a rotor position sensor  158 , thus allowing the pressure medium volume delivered to be determined from said piston position. 
     A method is further provided herein. The method includes selecting a driving performance mode from at least one of a first performance mode and a second performance mode for a braking system, the braking system having a pedal assembly coupled with a master cylinder, the pedal assembly having a feedback force, the pedal assembly having two or more activated positions and an inactivated position, a pedal feel simulator coupled with the pedal assembly, the pedal feel simulator configured to apply force feedback to the pedal assembly, the pedal feel simulator coupled with a simulator valve, the simulator valve configured to trap pressure within the pedal feel simulator when the braking system is in the second performance mode, a plurality of wheel brakes hydraulically or non hydraulically coupled with the master cylinder, selecting a pedal response force based on performance mode selection, where the pedal response force having a first pedal response force for the first performance mode and a second pedal response force for the second performance mode, and the first pedal response force is different than the second pedal response force, and configuring the pedal feel simulator to have the selected pedal response force. 
     In one or more embodiments, selecting the driving performance mode from at least one of the first performance mode and the second performance mode includes selecting from a comfort mode and a sport mode. In one or more embodiments, the first performance mode is a default mode and the second performance mode is an alternate mode which provides a driver with a shorter travel and higher force pedal feel characteristic than in the default mode. 
     In one or more embodiments, the method further includes pre-filling fluid pressure within the pedal feel simulator. 
     In one or more embodiments, configuring the pedal feel simulator to have the selected pedal response force includes opening an analog valve connected with the pedal feel simulator. 
     In one or more embodiments, configuring the pedal feel simulator assembly to have the selected pedal response force includes opening at least one of a first valve and second valve connected with the pedal feel simulator. 
     The above description is intended to be illustrative, and not restrictive. Many other embodiments will be apparent to those of skill in the art upon reading and understanding the above description. Embodiments discussed in different portions of the description or referred to in different drawings can be combined to form additional embodiments of the present application. The scope should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.