Method and control device for combined brake and drive / service brake control - Patents.com

Abstract

The present invention relates to a method for combined brake and drive / service brake control in which, at low speeds (106), the right steered wheels (108) and the left steered wheels (108) of the vehicle (100) are steered to have counter-rotating toe angles (110) to decelerate the vehicle (100), thereby at least partially compensating for pitching motion (122) of the vehicle caused by deceleration with vertical motion (120) resulting from the counter-steered wheels (108).

Description

[Technical Field]

[0001] FIELD OF THE INVENTION The present invention relates to a method for combined control of brake braking and drive and / or service braking, a corresponding control device and a corresponding computer program product. [Background technology]

[0002] Prior art Conventionally, to steer a vehicle, the right and left wheels on one axle are steered by the vehicle's steering wheel via a common steering gear. When steering is performed in a "steer-by-wire" manner, the mechanical connection between the steering wheel and the steering gear, and therefore the mechanical connection to the steered wheels, is eliminated. The steering movements are converted into electrical signals at the steering wheel and transmitted to the control device of the actual steering regulator. In a central steer-by-wire system, the left and right wheels are still steered by a common steering gear and are therefore kinematically coupled.

[0003] In order to be able to omit the mechanical connection between the right and left wheels, in the case of "steer-by-wire" steering, each wheel can be steered by an individual wheel steering adjuster. Summary of the Invention [Problem to be solved by the invention]

[0004] Disclosure of the Invention Against this background, the approach presented herein provides a method for combined brake braking and drive / service braking control, a corresponding control device and a corresponding computer program product as set forth in the independent claims. Advantageous developments and improvements of the approach presented herein are evident from the description and are set forth in the dependent claims.

[0005] Advantages of the invention When a vehicle wheel is steered, the vehicle rises or falls in the area of ​​that wheel based on the chassis kinematics of the wheel. This reaction is based on various chassis parameters, including, inter alia, the kingpin angle of the steering axis relative to the vehicle's height axis and the caster rail lever arm, which is the distance between the intersection of the steering axis extension at the road height in the x-direction and the wheel contact point.

[0006] With individual wheel steering adjusters, different toe angles can be set for each steered wheel of the vehicle independently of one another, allowing the chassis kinematics to be fully utilized and the vertical movement of the vehicle's axle kinematics to be controlled individually via each wheel.

[0007] Additionally, the wheels of an axle roll in different directions due to different toe angles when the vehicle moves. Since the vehicle, including the wheels, can only move in the resulting direction, the different toe angles create slip angles at the steered wheels relative to the vehicle's direction and thus to lateral or transverse forces. In response to the application of these lateral forces, tension is applied to the chassis. This tension can cause the vehicle to additionally lift or lower at the steered wheels. When the toe angles of the individual wheels are adjusted symmetrically, the lateral force component directed in the direction of the vehicle's movement generates a braking action.

[0008] When the vehicle decelerates, a pitching moment occurs as a result of the vehicle's mass inertia. This causes a spring contraction on the axle located forward in the direction of travel. On this axle, the vehicle drops due to the pitching moment. When the vehicle accelerates, an opposite pitching moment occurs. This pitching moment causes a spring extension on the axle located forward in the direction of travel. [Means for solving the problem]

[0009] The approach presented herein uses chassis kinematics and / or chassis tension application to raise or lower the vehicle by manipulating the toe angles of each individual wheel to at least partially compensate for the rise or fall due to the pitching moment. Additionally, the pitching motion of the vehicle can be influenced by deliberate driving or braking of the vehicle.

[0010] The approach presented herein allows pitching movements of the vehicle body to be at least partially counteracted, and even substantially completely compensated, by establishing a balance between the pitching moment induced by driving or braking and the toe angle in the pulley position.

[0011] The approach presented here is applicable to both forward and reverse driving, with the toe angles set accordingly.

[0012] A method is presented for combined brake braking and drive / service braking control, where at low speeds, when a braking moment is applied to the braked wheels of the vehicle, the steered right and left wheels of the vehicle are steered to have opposite toe angles, whereby pitching motion of the vehicle caused by the braking moment is at least partially compensated for by vertical motion due to the wheels being steered in opposite directions, and when a drive moment is applied to the driven wheels of the vehicle, the steered wheels are steered back, whereby pitching motion caused by the drive moment is at least partially compensated for by vertical motion due to the wheels being steered in opposite directions.

[0013] The conception of the embodiments of the present invention can be considered to be based in particular on the ideas and knowledge set forth below.

[0014] Different toe angles on each wheel of a vehicle axle can cause the wheels to move apart or move towards each other as the vehicle moves. In this case, a "Pluck" or "V" angle can be established between the wheels. The Pluck or V angle applies tension to the axle chassis. In the case of a Pluck angle, the wheels move towards the center of the axle. The Pluck angle can cause a lateral pushing force on the axle chassis in the y-direction of the axle center. In the case of a V-angle, the wheels move away from each other outward. The V-angle can cause a pulling force on the chassis in the y-direction away from the center of the vehicle.

[0015] If the pull angle or V-angle is set symmetrically, when the vehicle moves, the lateral slip of the wheels generates a deceleration force in the x-direction of the vehicle that counteracts this movement. The vehicle is braked by the pull angle or V-angle. In this case, the vehicle is braked more strongly the more the wheels are steered. This is a nonlinear relationship, and this nonlinear relationship only applies up to a certain slip angle limit. Slip can cause wear on the wheels. Therefore, the approach presented here is proposed for low-speed driving, preferably up to 20 km / h, in order to be able to limit wear. An additional braking moment can be provided via the wheel brakes of the wheels.

[0016] The pitching movement caused by starting off, especially at the front axle, can be compensated for by lowering the chassis when steering back. A driving moment can be applied to the non-steered and / or steered wheels. A braking moment, in particular, cannot be applied to the steered wheels. This means that the steered wheels are either driven or free to roll. This reduces the steering force required. By steering back when applying a driving moment, a harmonious acceleration of the vehicle can be achieved, since the braking effect is continuously reduced as the wheels are steered back in opposite directions.

[0017] When a vehicle moves to one side during deceleration, the steered wheels can be steered to have different, counter-rotating toe angles, allowing the resulting pull or V angle to remain the same in absolute terms. Variable toe angles keep the vehicle under control. Different toe angles allow the vehicle to steer in a straight line.

[0018] When a vehicle is steered in one direction during deceleration, the steered wheels can be steered to have different, counter-rotating toe angles, and the resulting pull angle or V angle can remain unchanged in absolute value. The different toe angles allow the vehicle to steer on a predetermined trajectory while using the approach presented herein.

[0019] If the vehicle moves to one side during deceleration, braking moments can be applied asymmetrically to at least one right wheel of the vehicle and at least one left wheel of the vehicle. The asymmetric braking intervention can generate a stabilizing yaw moment. In this case, different steering of the wheels can still be performed.

[0020] After the vehicle has come to a stop, the steered wheels can remain steered with opposite toe angles to keep the vehicle stationary. The wheels steered in opposite directions can prevent the vehicle from rolling away due to the resulting lateral force component in the longitudinal direction of the vehicle. This stopping can be assisted by wheel brakes.

[0021] The method is preferably computer-implemented and may be implemented, for example, as software or hardware or as a mixture of software and hardware, for example in a driver assistance system.

[0022] The approach presented herein further provides a control device configured to perform, control or realize the steps of the method variants presented herein in a corresponding device.

[0023] The control device may be an electrical device comprising at least one computing unit for processing signals or data, at least one storage unit for storing signals or data, and at least one interface and / or communication interface for reading or outputting data embedded in a communication protocol. The computing unit may be, for example, a signal processor, a so-called system ASIC, or a microcontroller for processing sensor signals and outputting data signals depending on the sensor signals. The memory unit may be, for example, a flash memory, an EPROM, or a magnetic memory unit. The interface may be configured as a sensor interface for reading sensor signals from sensors and / or as an actuator interface for outputting data and / or control signals to actuators. The communication interface may be configured to read or output data wirelessly and / or via a wired connection. The interface may be, for example, a software module residing on a microcontroller adjacent to other software modules.

[0024] Also advantageous is a computer program product or computer program having a program code storable on a machine-readable carrier or machine-readable memory medium, such as a semiconductor memory, a hard disk or an optical memory, and which, in particular when executed on a computer or device, is used to perform, realize and / or control the steps of the method according to one of the embodiments described above.

[0025] It should be noted that some of the possible features and advantages of the present invention are described herein in relation to different embodiments, and those skilled in the art will recognize that the features of the control device and method can be combined, adjusted, or substituted in any suitable manner to arrive at further embodiments of the present invention.

[0026] Embodiments of the present invention will now be described with reference to the accompanying drawings, but neither the drawings nor the description should be construed as limiting the present invention. [Brief explanation of the drawings]

[0027] [Figure 1] FIG. 10 shows the pull position in a vehicle with individual wheel steering adjusters when using a method according to an embodiment. [Figure 2] 10A and 10B are diagrams illustrating the operation of a brake according to an embodiment of the present invention;

[0028] The drawings are only schematic and are not to scale. Identical reference signs represent identical features or features with equivalent action. DETAILED DESCRIPTION OF THE INVENTION

[0029] Embodiments of the invention 1 illustrates a pluck position for a vehicle 100 equipped with an individual wheel steering adjuster 102 when using a method according to one embodiment. The vehicle 100 has an individual wheel steering adjuster 102 on at least one axle 104. The individual wheel steering adjuster 102 is electronically controlled in a "steer-by-wire" system. The illustrated axle 104 is here the front axle of the vehicle 100. However, the axle 104 may alternatively or additionally be the rear axle of the vehicle 100.

[0030] When the vehicle 100 is traveling at a low speed 106, e.g., less than 20 km / h, the wheels 108 of the vehicle 100 are steered to have opposite toe angles 110 when braking. Here, the wheels 108 are steered to have symmetrical toe angles for brake braking 112. In this case, the wheels 108 have a brake angle relative to each other. This steering generates a lateral force 114 at the wheels 108. The lateral force 114 acts partly in the longitudinal direction of the vehicle and partly in the transverse direction. The transverse force 116 is opposite to each other at both wheels 108 and applies tension to the chassis of the axle 104 via the chassis parameters, particularly the kingpin angle and caster angle. The longitudinal force 118 is in the same direction and brakes the vehicle 100.

[0031] The tilt of the wheels 108 about the toe angle 110 causes vertical body movement 120 of the vehicle 100 via the axles 104, with the steering axis of the chassis oriented at an angle relative to the bottom based on the kingpin and caster angles. Additionally, this vertical movement 120 can be amplified by applying tension to the chassis.

[0032] The vertical motion 120 acts to counteract the pitching motion 122 of the vehicle 100 based on a braking moment for braking the vehicle 100. The vertical motion 120 can at least partially compensate for the pitching motion 122.

[0033] In one embodiment, the brakes 112 are released when the vehicle 100 starts moving. Once released, the wheels 108 are again oriented substantially parallel to one another, allowing the vehicle 100 to start moving without braking. In this case, the braking action of the brakes 112 decreases smoothly rather than abruptly, thereby enabling a smooth start.

[0034] That is, pitching of the vehicle is caused by the drivetrain or service brakes, but the application of tension and the vertical movement (caused by the brake steering) associated with the application of tension act to counteract this pitching. The present invention does not relate to the brake process by brake braking itself, but to the combination of brake posture, drivetrain and service brakes when starting or braking, which allows for a driving feel as comfortable as possible with minimal pitching.

[0035] In one embodiment, if the vehicle yaws, the orientation of the brakes 112 is adjusted accordingly. To achieve this, the toe angle 110 of one wheel 108 is decreased while the toe angle 110 of the other wheel 108 is increased. For example, the vehicle 100 may yaw if one wheel 108 has a different friction value with the ground than the other wheel. The different friction values ​​directly cause different lateral forces 114, which correspondingly cause an imbalance of forces acting on the vehicle 100. By varying the brakes 112, a compensated lateral force 114 is generated, and the vehicle 100 continues to move in a straight line.

[0036] In one embodiment, if it is desired to steer the vehicle 100 to one side, the orientation of the brake pull 112 is changed. To do this, the toe angle 110 of one wheel 108 is decreased while the toe angle 110 of the other wheel 108 is increased. Each different toe angle 110 causes a different lateral force 114. Each different lateral force 114 causes a yaw moment that rotates the vehicle 100 about its vertical axis.

[0037] In one embodiment, the wheels 108 are left in brake pull 112 after stopping the vehicle 100. The brake pull 112 prevents the vehicle 100 from rolling, for example, on a slope.

[0038] 2 shows the operation of a brake system according to an embodiment. Situation identification 200, which can be performed optically, acoustically, via inertial sensors, or based on traffic flow, identifies situations 202, such as stopping and starting downhill, approaching a traffic light or stop sign, an emergency braking situation, a priority situation, a hill-hold situation, an uphill starting situation, or a parking departure situation. Subsequently, combined control 204 of the individual wheel steering regulators, the drive system, or the brake system is performed depending on the situation. For example, brake system activation may be performed during braking, followed by release of brake system and switching on of the drive system when the chassis tension is released.

[0039] In the following, possible embodiments of the invention will be summarized again or described using slightly different terminology choices.

[0040] To improve comfort, a strategy is presented for intelligent control of brake braking by individual wheel actuators in special driving situations.

[0041] Today's steering systems consist of a central coordinator that rotates the left and right wheels approximately evenly. In the majority of vehicles available on the market, such a central coordinator is mounted only on the front axle, with a mechanical connection between the steering wheel and the steered wheels.

[0042] In the case of by-wire systems, the classical mechanical connection between the driver and the actuator systems (steering, braking, etc.) is generally dispensed with. When steering, the corresponding action is carried out purely via one or more regulators. Central, but also decentralized, by-wire steering regulators are already in use on rear axles (e.g., ZF AKC). For the front axle, the first prototype vehicles with by-wire individual wheel steering regulators are already known, such as the research vehicle SpeedE (RWTH Aachen University).

[0043] A by-wire system with steering actuators for each individual wheel can adjust different steering adjuster positions and thus different wheel steering angles depending on the driving profile and the selected gear ratio between the steering wheel angle and the wheel steering angle. Due to the absence of a kinematic coupling between the left and right wheels, the actuators of such a steering system can also steer in opposite directions, which slows the vehicle down, a process known as brake braking.

[0044] In addition to its function of reducing the vehicle's speed, the system can also be used as a parking brake, thereby preventing the vehicle from moving undesirably. To meet the requirements for the parking brake function, depending on the design, this parking function of the parking brake can be implemented in cooperation with other braking systems (friction brakes, brakes in the transmission / drive). In this case, the system does not perform the entire stopping function by itself, but can be assisted by other systems, and in some cases only in special situations.

[0045] The concept of automatically engaging or releasing brake brakes as a deceleration system or parking brake in combination with the intervention of the drive in the corresponding situation has not existed up to now. The function of brake brakes as parking brakes has been provided in previous concepts as a manually activated system that is actively switched on like a parking brake and correspondingly manually deactivated.

[0046] The application of tension to the chassis is achieved by the pull position of the wheels, and the application of tension to the chassis can be skillfully assisted at the same time by the drive device to achieve uniform running characteristics whether the pull position is closed or opened.

[0047] This document presents a concept of how brake braking can be intelligently used as a parking brake / stop function in certain situations and how this braking / parking situation can be switched over to normal driving mode without any change, where the focus is on gaining comfort through simultaneous intervention of the drive to compensate for pitching movements of the vehicle during deceleration or initial acceleration.

[0048] In this case, intelligent identification of situations in which a stopping or deceleration function of brake braking is considered advantageous and the corresponding control of the function in combination with the intervention of the drive are performed centrally and automatically. Furthermore, a control concept for transitioning from brake position to normal driving is presented.

[0049] The pull position of a steer-by-wire system with individual wheel actuators for the case of symmetric positive toe angles is exemplarily shown in Figure 1. Other smaller toe angle differences and negative toe angles for applying pull braking are also possible or necessary depending on the driving situation (e.g., mu-split or steady curve driving).

[0050] The approach presented herein can implement a cycle of situation identification, brake braking, and combined control of the drive and braking system. Identification of specific driving situations, such as approaching a traffic light, starting uphill, or stop-and-go situations, can be performed optically with sensor data from inertial sensors (gradient changes) and by road-tire contact estimation algorithms. This can enable optimal control of the brake function. Brake braking should only be performed in emergency situations, since high speeds are associated with tire wear. The function presented herein is advantageous for low speeds up to approximately 20 km / h. Once the need for deceleration to a standstill is identified, brake braking can already introduce small toe changes, which can then be further supported by friction braking, if necessary. When a future resumption of driving (uphill / downhill / traffic lights / parking) is detected, the pull position is released towards a steady toe-in and at the same time the drive is switched on, allowing for a uniform transition from a stationary situation to a driving situation.

[0051] The pitching movements that are present when braking or driving with conventional steering systems can be reduced in the combined brake and drive control, thereby improving driving comfort.

[0052] To ensure that the steering force is as small as possible when the brake function is activated, for example, a stopping force can be applied by the drive unit at the moment of starting off on an uphill slope, which makes it easier to release the chassis tension (the steering force is greater when the wheels are braked by the service brakes).

[0053] In one embodiment, when a vehicle is approaching a green traffic light but is still stationary, braking is performed by closing the brakes without using friction brakes if a slight terminal velocity is present. To achieve a stop, uniform tensioning of the chassis is performed by simultaneously controlling the drive / brake system until the stop is reached. For continued travel, a gradual release of the brakes is performed depending on the distance to the vehicle ahead, with simultaneous assistance from the drive for uniform continued travel and pitch compensation.

[0054] In a further embodiment, in the case of downhill stop-and-go (e.g. with a trailer), a sinusoidal steering angle curve is generated during the corresponding phases of the stop-and-go maneuver. Depending on the estimated road conditions, a slight asymmetrical action can be implemented to maintain toe fidelity. If the road is curved, a slight asymmetrical release of the brook (asymmetrical toe angle) can be implemented with a corresponding toe-in to guide the curve. At the same time, intelligent control can be implemented to mitigate the vehicle's pitching behavior based on the application of tension to the chassis, thereby improving comfort.

[0055] The advantages of break braking compared to conventional braking are particularly noticeable when starting off. The action of break braking is based on utilizing the lateral force of the tire. Therefore, once break braking is terminated, a driving moment (longitudinal force of the tire) can be applied to start off. To reduce tire wear, break braking should be reactivated as soon as the vehicle starts moving. However, a seamless transition between braking and starting off is possible with reduced pitching movements of the vehicle.

[0056] Finally, it should be noted that terms such as "comprise", "include", etc. do not exclude other elements or steps, and terms such as "a" do not exclude a plurality. Reference signs in the claims are not to be construed as limiting.

Claims

1. 1. A method for combined brake and drive / service brake control, comprising: When a braking moment is applied to a braked wheel (108) of a vehicle (100) at low speed (106), the right steered wheel (108) and the left steered wheel (108) of the vehicle (100) are steered to have opposite toe angles (110) so that a pitching motion (122) of the vehicle caused by the braking moment is at least partially compensated for by a vertical motion (120) due to the wheels (108) being steered in opposite directions; When a driving moment is applied to the driven wheels (108) of the vehicle (100), the steered wheels (108) are steered back together; This at least partially compensates for the pitching movement (122) caused by the drive moment by the opposing vertical movement (120) based on the steering back.

2. When the vehicle (100) moves to one side during deceleration, the steered wheels (108) are steered to have different, opposite toe angles (110). The method of claim 1.

3. When the vehicle (100) is steered in one direction during deceleration, the steered wheels (108) are steered to have different, opposite toe angles (110).

3. The method according to claim 1 or 2.

4. When the vehicle (100) moves to one side during deceleration, the braking moment is applied asymmetrically to at least one right wheel (108) of the vehicle (100) and at least one left wheel (108) of the vehicle (100).

4. The method according to any one of claims 1 to 3.

5. After the vehicle (100) has stopped, the steered wheels (108) are maintained steered to have opposite toe angles (110) to keep the vehicle (100) stationary.

5. The method according to any one of claims 1 to 4.

6. A control device adapted to perform, implement and / or control the method according to any one of claims 1 to 5 in a corresponding device.

7. A vehicle, in particular an automobile, comprising a control device according to claim 6.

8. 6. A computer program product configured to cause a processor to perform, implement and / or control the method of any one of claims 1 to 5 when said computer program product is executed.

9. 9. A machine-readable memory medium having stored thereon the computer program product of claim 8.

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