CN113085468A - Stability system for vehicle, control unit and method thereof - Google Patents
Stability system for vehicle, control unit and method thereof Download PDFInfo
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- CN113085468A CN113085468A CN201911337738.6A CN201911337738A CN113085468A CN 113085468 A CN113085468 A CN 113085468A CN 201911337738 A CN201911337738 A CN 201911337738A CN 113085468 A CN113085468 A CN 113085468A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60G—VEHICLE SUSPENSION ARRANGEMENTS
- B60G17/00—Resilient suspensions having means for adjusting the spring or vibration-damper characteristics, for regulating the distance between a supporting surface and a sprung part of vehicle or for locking suspension during use to meet varying vehicular or surface conditions, e.g. due to speed or load
- B60G17/015—Resilient suspensions having means for adjusting the spring or vibration-damper characteristics, for regulating the distance between a supporting surface and a sprung part of vehicle or for locking suspension during use to meet varying vehicular or surface conditions, e.g. due to speed or load the regulating means comprising electric or electronic elements
- B60G17/016—Resilient suspensions having means for adjusting the spring or vibration-damper characteristics, for regulating the distance between a supporting surface and a sprung part of vehicle or for locking suspension during use to meet varying vehicular or surface conditions, e.g. due to speed or load the regulating means comprising electric or electronic elements characterised by their responsiveness, when the vehicle is travelling, to specific motion, a specific condition, or driver input
- B60G17/0165—Resilient suspensions having means for adjusting the spring or vibration-damper characteristics, for regulating the distance between a supporting surface and a sprung part of vehicle or for locking suspension during use to meet varying vehicular or surface conditions, e.g. due to speed or load the regulating means comprising electric or electronic elements characterised by their responsiveness, when the vehicle is travelling, to specific motion, a specific condition, or driver input to an external condition, e.g. rough road surface, side wind
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60G—VEHICLE SUSPENSION ARRANGEMENTS
- B60G17/00—Resilient suspensions having means for adjusting the spring or vibration-damper characteristics, for regulating the distance between a supporting surface and a sprung part of vehicle or for locking suspension during use to meet varying vehicular or surface conditions, e.g. due to speed or load
- B60G17/015—Resilient suspensions having means for adjusting the spring or vibration-damper characteristics, for regulating the distance between a supporting surface and a sprung part of vehicle or for locking suspension during use to meet varying vehicular or surface conditions, e.g. due to speed or load the regulating means comprising electric or electronic elements
- B60G17/016—Resilient suspensions having means for adjusting the spring or vibration-damper characteristics, for regulating the distance between a supporting surface and a sprung part of vehicle or for locking suspension during use to meet varying vehicular or surface conditions, e.g. due to speed or load the regulating means comprising electric or electronic elements characterised by their responsiveness, when the vehicle is travelling, to specific motion, a specific condition, or driver input
- B60G17/0164—Resilient suspensions having means for adjusting the spring or vibration-damper characteristics, for regulating the distance between a supporting surface and a sprung part of vehicle or for locking suspension during use to meet varying vehicular or surface conditions, e.g. due to speed or load the regulating means comprising electric or electronic elements characterised by their responsiveness, when the vehicle is travelling, to specific motion, a specific condition, or driver input mainly during accelerating or braking
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60G—VEHICLE SUSPENSION ARRANGEMENTS
- B60G17/00—Resilient suspensions having means for adjusting the spring or vibration-damper characteristics, for regulating the distance between a supporting surface and a sprung part of vehicle or for locking suspension during use to meet varying vehicular or surface conditions, e.g. due to speed or load
- B60G17/015—Resilient suspensions having means for adjusting the spring or vibration-damper characteristics, for regulating the distance between a supporting surface and a sprung part of vehicle or for locking suspension during use to meet varying vehicular or surface conditions, e.g. due to speed or load the regulating means comprising electric or electronic elements
- B60G17/019—Resilient suspensions having means for adjusting the spring or vibration-damper characteristics, for regulating the distance between a supporting surface and a sprung part of vehicle or for locking suspension during use to meet varying vehicular or surface conditions, e.g. due to speed or load the regulating means comprising electric or electronic elements characterised by the type of sensor or the arrangement thereof
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60G—VEHICLE SUSPENSION ARRANGEMENTS
- B60G17/00—Resilient suspensions having means for adjusting the spring or vibration-damper characteristics, for regulating the distance between a supporting surface and a sprung part of vehicle or for locking suspension during use to meet varying vehicular or surface conditions, e.g. due to speed or load
- B60G17/015—Resilient suspensions having means for adjusting the spring or vibration-damper characteristics, for regulating the distance between a supporting surface and a sprung part of vehicle or for locking suspension during use to meet varying vehicular or surface conditions, e.g. due to speed or load the regulating means comprising electric or electronic elements
- B60G17/019—Resilient suspensions having means for adjusting the spring or vibration-damper characteristics, for regulating the distance between a supporting surface and a sprung part of vehicle or for locking suspension during use to meet varying vehicular or surface conditions, e.g. due to speed or load the regulating means comprising electric or electronic elements characterised by the type of sensor or the arrangement thereof
- B60G17/01908—Acceleration or inclination sensors
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60G—VEHICLE SUSPENSION ARRANGEMENTS
- B60G17/00—Resilient suspensions having means for adjusting the spring or vibration-damper characteristics, for regulating the distance between a supporting surface and a sprung part of vehicle or for locking suspension during use to meet varying vehicular or surface conditions, e.g. due to speed or load
- B60G17/02—Spring characteristics, e.g. mechanical springs and mechanical adjusting means
- B60G17/04—Spring characteristics, e.g. mechanical springs and mechanical adjusting means fluid spring characteristics
- B60G17/052—Pneumatic spring characteristics
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60G—VEHICLE SUSPENSION ARRANGEMENTS
- B60G2800/00—Indexing codes relating to the type of movement or to the condition of the vehicle and to the end result to be achieved by the control action
- B60G2800/20—Stationary vehicle
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60G—VEHICLE SUSPENSION ARRANGEMENTS
- B60G2800/00—Indexing codes relating to the type of movement or to the condition of the vehicle and to the end result to be achieved by the control action
- B60G2800/90—System Controller type
- B60G2800/91—Suspension Control
- B60G2800/914—Height Control System
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Vehicle Body Suspensions (AREA)
Abstract
A stability system for a vehicle, a control unit and a method thereof are provided. The control unit (21) comprises: an acquisition module (31) configured to acquire a distance of a front suspension from a vehicle center of mass and a distance of a rear suspension from the vehicle center of mass; a processing module (32) configured to calculate an optimized height of the front suspension based on the static and maximum vertical loads of the front suspension and the actual coefficient of friction, and to calculate an optimized height of the rear suspension based on the static and maximum vertical loads of the rear suspension and the actual coefficient of friction; and a generating module (33) configured to generate a first height control signal in dependence on the optimized height of the front suspension; and a second height control signal based on the optimized height of the rear suspension.
Description
Technical Field
The invention relates to a stability system for a vehicle, a control unit and a method thereof.
Background
The stability system of the vehicle can improve the control performance of the vehicle and can also effectively prevent the vehicle from being out of control when reaching the dynamic limit. Because, the stability system of the vehicle can promote the safety and the maneuverability of the vehicle. The stability system of the vehicle can exert the function of actively improving the safety under various scenes. For example, during Automatic Emergency Braking (AEB), the stability system of the vehicle may improve safety and handling by controlling the suspension system.
The suspension system of the vehicle is used for transmitting force and moment between wheels and axles and inhibiting vibration of the vehicle in the driving process so as to ensure smooth driving of the vehicle. The vehicle may experience instability phenomena during braking, such as pitching, which negatively affects the stability and braking effectiveness of the vehicle. Although the prior art has a scheme of controlling a suspension system through a stability system of a vehicle so as to reduce the vibration of the vehicle, the prior scheme cannot achieve an ideal shock absorption effect in the braking process of the vehicle.
Disclosure of Invention
In view of the above problems in the prior art, the present invention is directed to provide a stability system for a vehicle, a control unit and a method thereof, which can alleviate the shock of the vehicle during automatic emergency braking and can improve the braking efficiency.
To this end, according to one aspect of the present invention, there is provided a control unit for a stability system of a vehicle, comprising: an acquisition module configured to acquire a distance of a front suspension from a vehicle center of mass and a distance of a rear suspension from the vehicle center of mass; a processing module configured to calculate a static vertical load of the front suspension based on a distance of the front suspension from a center of mass of the vehicle and a static vertical load of the rear suspension based on a distance of the rear suspension from the center of mass of the vehicle; determining the maximum vertical load of a front suspension and the maximum vertical load of a rear suspension based on the actual friction coefficient of the road surface; calculating the optimized height of the front suspension based on the static vertical load and the maximum vertical load of the front suspension and the actual friction coefficient, and calculating the optimized height of the rear suspension based on the static vertical load and the maximum vertical load of the rear suspension and the actual friction coefficient; and a generating module configured to generate a first height control signal for adjusting the height of the front suspension during automatic emergency braking of the vehicle in dependence on the optimized height of the front suspension; and forming a second height control signal for adjusting the height of the rear suspension during automatic emergency braking of the vehicle in dependence on the optimized height of the rear suspension.
According to a possible embodiment, the acquisition module also acquires the actual amount of gas in a first air spring connected to the front suspension and the actual amount of gas in a second air spring connected to the rear suspension of the vehicle; the processing module is further configured to calculate an amount of gas required by the first air spring to cause the front suspension to reach its optimized height based on the optimized height of the front suspension, and calculate an amount of gas required by the second air spring to cause the rear suspension to reach its optimized height based on the optimized height of the rear suspension; the generation module generates a first gas amount control signal based on an actual gas amount and a required gas amount in the first air spring for adjusting the gas amount in the first air spring during automatic emergency braking of the vehicle; and generating a second gas amount control signal based on the actual gas amount and the required gas amount in the second air spring for adjusting the gas amount in the second air spring during automatic emergency braking of the vehicle.
According to a possible embodiment, the actual friction coefficient is obtained by: the acquisition module further acquires a default road friction coefficient of the stability system and an actual acceleration of the vehicle in the running direction, and the processing module calculates a predicted acceleration of the vehicle in the moving direction based on the default road friction coefficient; and calculating the actual coefficient of friction based on the predicted acceleration and the actual acceleration.
According to one possible embodiment, the processing module calculates the predicted acceleration based on the following formula:
a(request)＝c(default)*g
wherein a (request) is the predicted acceleration, c (default) is the default road surface friction coefficient, g is the gravity acceleration,
the processing module calculates the actual friction coefficient based on the following formula:
c(actual)＝c(default)*a(actual)/a(request)
where a (actual) is the actual acceleration of the vehicle in the direction of motion and c (actual) is the actual coefficient of friction of the road surface.
According to a possible embodiment, the acquisition module also acquires vehicle parameters including vehicle mass, actual acceleration of the vehicle in the direction of motion, and distance between the front and rear suspensions; the processing module is configured to calculate an optimal height of the front suspension by: calculating the difference between the maximum vertical load and the static vertical load of the front suspension to obtain the vertical load transfer amount of the front suspension; calculating the optimized height of the front suspension according to the vertical load transfer amount of the front suspension, the actual friction coefficient and the vehicle parameters; and the processing module is configured to calculate the optimal height of the rear suspension by: calculating the difference between the maximum vertical load and the static vertical load of the rear suspension to obtain the vertical load transfer amount of the rear suspension; and calculating the optimized height of the rear suspension according to the vertical load transfer amount of the rear suspension, the actual friction coefficient and the vehicle parameters.
According to a possible embodiment, the processing module calculates the optimal height of the front suspension by the following formula:
h(front,optimal)＝[F(front,max)-F(front,static)]*L(total)/[m*c(actual)*a(brake)]
the processing module calculates the optimized height of the rear suspension through the following formula:
h(rear,optimal)＝[F(rear,max)-F(rear,static)]*L(total)/[m*c(actual)*a(brake)]
wherein F (front, max) is the maximum vertical load of the front suspension, F (front, static) is the static vertical load of the front suspension, F (rear, max) is the maximum vertical load of the rear suspension, F (rear, static) is the static vertical load of the rear suspension, a (break) is the actual acceleration of the vehicle in the moving direction, c (actual) is the actual friction coefficient, m is the vehicle mass, and l (total) is the distance between the front and rear suspensions.
According to one possible embodiment, the processing module calculates the static vertical load of the front suspension by the following formula:
F(front,static)＝m*g*L(front)/L(total)
the processing module calculates the static vertical load of the rear suspension by the following formula:
F(rear,static)＝m*g*L(rear)/L(total)
wherein m is the vehicle mass, g is the gravitational acceleration, l (front) is the distance between the front suspension and the vehicle center of mass, l (rear) is the distance between the rear suspension and the vehicle center of mass, and l (total) is the distance between the front and rear suspensions.
According to a possible embodiment, the obtaining unit further obtains the tire pressure of a front wheel connected to the front suspension, the tire pressure of a rear wheel connected to the rear suspension, and environmental parameters, the environmental parameters including at least an ambient temperature and a road surface humidity; the processing module determines a maximum vertical load of the front suspension based on a tire pressure of a front wheel, an environmental parameter, and an actual friction coefficient; and the processing module determines a maximum vertical load of the rear suspension based on the tire pressure of the rear wheel, the environmental parameter, and the actual coefficient of friction.
According to a possible embodiment, the processing module is further configured to: calculating a first target braking force for a front wheel connected to the front suspension based on the optimized height and the static vertical load of the front suspension and the actual friction coefficient; and calculating a second target braking force for a rear wheel connected to the rear suspension based on the optimized height and the static vertical load of the rear suspension and the actual friction coefficient.
According to one possible embodiment, the processing module calculates the first target braking force according to the following formula:
Fbf＝F(front,static)+c(actual)*m*a(brake)*h(front,optimal)/L(total)
the processing module calculates a second target braking force according to the following formula:
Fbr＝F(rear,static)-c(actual)*m*a(brake)*h(rear,optimal)/L(total)
where Fbf is the first target braking force, F (front, static) is the static vertical load of the front suspension, Fbr is the second target braking force, F (rear, static) is the static vertical load of the rear suspension, a (brake) is the actual acceleration of the vehicle in the direction of motion, c (actual) is the actual coefficient of friction, m is the vehicle mass, and l (total) is the distance between the front and rear suspensions.
According to another aspect of the present invention, there is provided a stability system for a vehicle, comprising: a sensor unit for detecting a relative distance between the host vehicle and a potential collision object; a controller coupled to the sensor unit, the controller including a control unit as described above, the controller configured to activate the control unit as described above upon determining that the host vehicle enters automatic emergency braking based on the relative distance; and a suspension system coupled to the controller, the suspension system including a front suspension and a first air spring connected thereto, a rear suspension and a second air spring connected thereto, and a suspension controller, wherein the suspension controller is configured to control an amount of gas within the first air spring under control of the first height control signal such that the height of the front suspension is adjusted to be in accordance with the optimized height thereof, and to control an amount of gas within the second air spring under control of the second height control signal such that the height of the rear suspension is adjusted to be in accordance with the optimized height thereof.
According to a possible embodiment, the suspension controller is further configured to: detecting the height variation of the front suspension and the height variation of the rear suspension; when detecting that the height variation of the front suspension and the height variation of the rear suspension are equal, generating a stop instruction; and sending the stop instruction to a controller to stop the operation of the control unit.
According to one possible embodiment, the controller is further configured to send the first target braking force and the second target braking force to a hydraulic actuator of the vehicle, so that the actuator performs a braking maneuver of a front wheel connected to the front suspension based on the first target braking force and performs a braking maneuver of a rear wheel connected to the rear suspension based on the second target braking force.
According to a further aspect of the invention, there is also provided a control method for a stability system of a vehicle, optionally implemented by means of a control unit as described above and/or a stability system as described above, the method comprising: acquiring the distance between a front suspension and the vehicle mass center and the distance between a rear suspension and the vehicle mass center; calculating the static vertical load of the front suspension based on the distance between the front suspension and the vehicle mass center, and calculating the static vertical load of the rear suspension based on the distance between the rear suspension and the vehicle mass center; determining the maximum vertical load of a front suspension and the maximum vertical load of a rear suspension based on the actual friction coefficient of the road surface; calculating the optimized height of the front suspension based on the static vertical load and the maximum vertical load of the front suspension and the actual friction coefficient, and calculating the optimized height of the rear suspension based on the static vertical load and the maximum vertical load of the rear suspension and the actual friction coefficient; and generating a first height control signal for adjusting the height of the front suspension during automatic emergency braking of the vehicle in dependence on the optimized height of the front suspension; and forming a second height control signal for adjusting the height of the rear suspension during automatic emergency braking of the vehicle in dependence on the optimized height of the rear suspension.
Therefore, according to the technical scheme of the invention, the stability of the vehicle body in the automatic emergency braking process is maintained by providing the optimized height of the front suspension and the optimized height of the rear suspension in the automatic emergency process, so that the stability and the safety of the vehicle are improved. Moreover, according to the technical scheme of the invention, the target braking force can be provided, so that the braking efficiency is improved.
Drawings
Fig. 1 shows a schematic block diagram of a stability system for a vehicle according to one possible embodiment of the invention.
Fig. 2 shows a schematic block diagram of the control unit of the stability system of fig. 1.
Fig. 3 shows a schematic diagram of the suspension system of the stability system of fig. 1.
Fig. 4 shows a schematic structural view of a portion of the suspension system of fig. 3, according to one possible embodiment of the invention.
Fig. 5 shows a schematic diagram of the pitching movement of a vehicle during automatic emergency braking.
Fig. 6 shows a flow chart of a control method for a stability system of a vehicle according to one possible embodiment of the invention.
Detailed Description
According to the technical scheme, the optimized heights of the front suspension and the rear suspension are respectively calculated in the automatic emergency braking process of the vehicle, and the heights of the front suspension and the rear suspension are simultaneously adjusted according to the calculated optimized heights until the height variation amounts of the front suspension and the rear suspension are consistent, so that pitching motion of the vehicle in the automatic emergency braking process is slowed down or restrained. In addition, the technical scheme of the invention also provides target braking force for the vehicle in the automatic emergency braking process of the vehicle, thereby improving the braking efficiency.
Embodiments of the present invention are described below with reference to the accompanying drawings.
Fig. 1 shows a stability system 100 for a vehicle according to one possible embodiment of the invention, which mainly comprises a sensor unit 10, a controller 20, a hydraulic actuator 40 and a suspension system 50.
The sensor unit 10 may comprise a variety of sensors for detecting different parameters. For example, the sensor unit 10 may include a radar sensor and a displacement sensor mounted on a vehicle. Radar sensors are used to detect the relative distance between a vehicle and a potential collision object, e.g., the relative distance between the host vehicle and a preceding vehicle or obstacle. The sensor unit 10 may also include other types of sensors for assisting in sensing information around the vehicle, such as GPS, cameras, etc. The displacement sensor is used for detecting the displacement of the vehicle in the vertical direction. For example, the displacement sensor may have a plurality of sensors that respectively detect displacements of the front suspension and the rear suspension of the suspension system 50 in the vertical direction.
The sensor unit 10 may further include an acceleration sensor for sensing acceleration (e.g., braking deceleration) of the vehicle in the moving direction. The sensor unit 10 may include an environment sensor for sensing an environment around the vehicle. For example, the environmental sensor may include a temperature sensor for sensing an ambient temperature around the vehicle and a humidity sensor for sensing a humidity of a road surface on which the vehicle travels. The sensor unit 10 may further include a pressure sensor for sensing the tire pressure of the wheel.
It should be understood that the suspension controller 58 may be provided separately in the vehicle, may be integrated with the controller 20 of the stability system 100, or may be centralized in the controllers of other systems of the vehicle.
The operation of the suspension system of the present invention will now be described with reference to fig. 4, taking an air spring 55 of the suspension system 50 as an example.
Figure 4 schematically illustrates one air spring 55 and its associated components of a suspension system 50 according to one possible embodiment of the invention. As shown in fig. 4, the air spring 55 is coupled with the damper 61, and the damper 61 is coupled with the hub 5' of the wheel 5. The piston position of the damper 61 is adjusted by adjusting the amount of air in the air spring 55, thereby adjusting the height of the center of mass (e.g., the hub 5') of the wheel 5 from the ground. The air spring 55 is fluidly connected to the air reservoir 67, and a compressor 63 is connected in line between the air spring 55 and the air reservoir 67. The compressor 63 is connected to a motor 65 to be driven by the motor 65, thereby adjusting the amount of gas in the air spring 55.
The suspension controller 58 acts as a secondary controller in the stability system 100 that controls the regulation of the amount of gas in the air springs under the control of control signals from the controller 20 of the stability system 100. For example, the height of the suspension is adjusted by adjusting the amount of gas in the air spring, so that the vibration applied to the suspension by the wheels can be damped, and the vehicle body can be kept stable.
It should be understood that fig. 3 and 4 only show a schematic configuration of a suspension system and its air springs, which may also be implemented as other combinations of elements or other arrangements in accordance with the present invention.
The controller 20 is coupled with the sensor unit 10 to receive the relative distance between the host vehicle and the potential collision object from the sensor unit 10. The controller 20 comprises a control unit 30 which may be activated in automatic emergency braking of the vehicle. When the controller 20 determines that the vehicle needs to enter the automatic emergency braking according to the relative distance, the controller 20 activates the control unit 30 to execute a control strategy for mitigating vehicle shock and improving braking efficiency during the automatic emergency braking.
After the vehicle enters automatic emergency braking, the control unit 30 may calculate an optimal height for the front suspension and an optimal height for the rear suspension for adjusting the heights of the front and rear suspensions, respectively. The control unit 30 may further calculate a required gas amount in a first air spring for the optimized height of the front suspension and a required gas amount in a second air spring for the optimized height of the rear suspension for achieving the optimized height of the suspension based on the required gas amounts.
The control unit 30 may calculate a first target braking force for the front wheels and a second target braking force for the rear wheels for the hydraulic actuator 40 to perform the braking manipulation.
The control unit 30 may also determine a first braking torque request based on the measured relative distance, the speed and acceleration of the vehicle in the moving direction in combination with the first target braking force, so that the hydraulic actuator 40 performs a braking maneuver on the front wheels connected to the front suspension based on the first braking torque request. The control unit 30 determines a second braking torque request based on the measured relative distance, the speed and acceleration of the vehicle in the moving direction in combination with the second target braking force, so that the hydraulic actuator 40 performs a braking maneuver on the rear wheel connected to the rear suspension based on the second braking torque request.
Referring to fig. 5, when the vehicle enters automatic emergency braking, the wheels are deflected in the vertical direction, thereby causing the vehicle to pitch in a "nod-head" like manner. The control unit 30 can provide a control strategy for damping this pitch motion. Referring to fig. 2, the control unit 30 mainly includes an acquisition module 31, a processing module 32, and a generation module 33. The modules of the control unit 30 and their operating principle are described in detail below.
The acquisition module 31 acquires parameters for subsequent calculations, including front and rear suspension displacements, vehicle mass, distance of the front suspension from the vehicle center of mass, distance of the rear suspension from the vehicle center of mass, distance between the front and rear suspensions, system default road friction coefficient, speed and acceleration of the vehicle in the direction of motion.
In the present invention, front suspension displacement refers to a vertical displacement of the front suspension, i.e., a change in height of the front suspension, which can be measured by a displacement sensor near or coupled to the front suspension. The rear suspension displacement refers to a displacement of the rear suspension in the vertical direction, that is, an amount of change in the height direction of the rear suspension, which can be measured by a displacement sensor near or coupled to the rear suspension. The mass of the vehicle can be understood as the mass of the vehicle body.
The processing module 32 calculates the vertical load transfer amount Δ F of the front suspension using the parameters acquired by the acquisition module 31fAnd the amount of vertical load transfer of the rear suspension Δ Fr. Vertical load transfer amount Δ F of front suspensionfObtained by the difference between the maximum vertical load F (front, max) and the static vertical load F (front, static) of the front suspension, which is obtained by the following formula (i). Vertical load transfer amount Δ F of rear suspensionrObtained by the difference between the maximum vertical load F (rear, max) and the static vertical load F (rear, static) of the rear suspension, wherein the static vertical load F (rear, static) of the rear suspension is obtained by the following formula (c).
F(front,static)＝m*g*L(front)/L(total) ①
F(rear,static)＝m*g*L(rear)/L(total) ②
Wherein m is the vehicle mass, g is the gravitational acceleration, l (front) is the distance between the front suspension and the vehicle center of mass, l (rear) is the distance between the rear suspension and the vehicle center of mass, and l (total) is the distance between the front and rear suspensions.
The maximum vertical load F (front, max) of the front suspension can be obtained from a lookup table based on the actual friction coefficient of the road surface on which the vehicle is traveling, the tire pressure of the front wheels, the ambient temperature, and the road surface humidity. The maximum vertical load F (rear, max) of the rear suspension can be obtained from a lookup table based on the actual friction coefficient of the road surface on which the vehicle is traveling, the tire pressure of the rear wheels, the ambient temperature, and the road surface humidity. It should be understood that the table for finding the actual coefficient of friction may be obtained by means of a tire model provided by the supplier of the tire. The process by which the processing module 32 calculates the actual coefficient of friction is described below.
The processing module 32 determines a requested value (predicted value) of the acceleration of the vehicle in the moving direction based on the system default road surface friction coefficient, that is, predicts the acceleration that the vehicle can currently take according to the whole vehicle moving model and the system default set parameters. For example, the processing module 32 calculates the requested value of the acceleration according to the following formula. The processing module 32 then determines the actual friction coefficient of the current road surface from the predicted and measured values of acceleration. For example, the processing module 32 calculates the actual friction coefficient according to the following equation (d).
a(request)＝c(default)*g ③
c(actual)＝c(default)*a(actual)/a(request) ④
Wherein, a (request) is the request value of the acceleration of the vehicle in the moving direction, a (actual) is the measured value of the acceleration of the vehicle in the moving direction, g is the gravity acceleration, c (default) is the default value of the friction coefficient of the road surface, and c (actual) is the actual value of the friction coefficient of the road surface.
The processing module 32 calculates the vertical load transfer Δ F of the front suspensionfAnd the amount of vertical load transfer of the rear suspension Δ FrThen, according to the vertical load transfer amount Δ F of the front suspensionfCalculating the optimal height h (front, optimal) of the front suspension according to the actual friction coefficient of the road surface, and according to the vertical load transfer amount delta F of the rear suspensionrAnd calculating the optimal height h (rear) of the rear suspension by using the actual friction coefficient of the road surface. For example, the processing module calculates the optimal height h (front) of the front suspension according to the formula [ + ] and the formulaSixthly, calculating the optimal height h (rear) of the rear suspension.
h(front,optimal)＝ΔFf*L(total)/[m*c(actual)*a(brake)]＝[F(front,max)-F(front,static)]*L(total)/[m*c(actual)*a(brake)] ⑤
h(rear,optimal)＝ΔFr*L(total)/[m*c(actual)*a(brake)]＝[F(rear,max)-F(rear,static)]*L(total)/[m*c(actual)*a(brake)] ⑥
Where a (brake) is the brake deceleration, i.e. the actual acceleration of the vehicle in the direction of motion, c (actual) is the actual value of the road friction coefficient, m is the vehicle mass, and l (total) is the distance between the front and rear suspensions.
After the processing module 32 calculates the optimized height of the front suspension and the optimized height of the rear suspension, the generating module 33 generates a first height control signal based on the optimized height of the front suspension and a second height control signal based on the optimized height of the rear suspension.
In turn, the suspension controller 58 controls the adjustment of the front and rear suspension heights in response to the first and second height control signals. For example, the suspension controller 58 controls the adjustment of the amount of gas within the first air springs 52 and 53 in accordance with the first height control signal to adjust the height of the front suspension 56 to its optimal height and to monitor the amount of height change of the front suspension 56. The suspension controller 58 controls the adjustment of the amount of gas in the second air springs 54 and 55 in accordance with the second height control signal to adjust the height of the rear suspension 57 to its optimum height and monitors the amount of height change of the rear suspension 57.
The control unit 30 continuously calculates the optimized heights of the front and rear suspensions based on the parameters sensed in real time by the sensor unit 10, and the suspension system 50 dynamically adjusts the heights of the front and rear suspensions corresponding to the first and second height control signals until the amount of height change of the front suspension coincides with the amount of height change of the rear suspension. For example, when the suspension controller 58 monitors that the amount of height change of the front suspension coincides with the amount of height change of the rear suspension, a stop instruction is generated, and the control unit 30 stops calculating the optimal heights of the front and rear suspensions in response to the stop instruction.
It should be understood that, when the height variation of the front and rear suspensions is uniform, it can be understood that the gravity center of the vehicle changes uniformly due to the stress and height variation of the front and rear suspensions.
In one embodiment, the processing module 32 may further calculate the amount of gas required by the first air spring to bring the front suspension to its optimal height and the amount of gas required by the second air spring to bring the rear suspension to its optimal height after calculating the optimal heights of the front and rear suspensions. And the generating unit 33 determines the amount of gas that the first air spring needs to adjust (enter or exhaust) based on the actual amount of gas in the first air spring and the required amount of gas to generate the first gas amount control signal. The generating unit 33 determines the amount of gas that the second air spring needs to adjust (enter or exhaust) based on the actual amount of gas in the second air spring and the required amount of gas to generate the second gas amount control signal.
The suspension controller 58 controls adjustment of the amount of gas in the first air spring in response to the first gas amount control signal and controls adjustment of the amount of gas in the second air spring in response to the second gas amount control signal. When the amount of gas in the first air spring reaches its desired amount, the front suspension is adjusted to its optimal height. When the amount of gas in the second air spring reaches its desired amount, the rear suspension is adjusted to its optimum height.
According to the embodiment, the front and rear suspensions can be adjusted to the corresponding optimized heights quickly, and the embodiment can directly adjust the suspension height to the target height through the calculated air adjustment amount, so that the process of detecting whether the optimized height is reached while adjusting is omitted.
Next, the processing module 32 calculates a first target braking force Fbf for the front wheels coupled to the front suspension based on the optimized height and the static vertical load of the front suspension and the actual coefficient of friction. For example, the processing module 32 calculates the first target braking force Fbf according to the following formula. The processing module 32 calculates a second target braking force Fbr for a rear wheel connected to the rear suspension based on the optimized height and the static vertical load of the rear suspension and the actual coefficient of friction. For example, the processing module 32 calculates the second target braking force Fbr according to the following formula ((r)).
Fbf＝F(front,static)+c(actual)*m*a(brake)*h(front,optimal)/L(total)
⑦
Fbr＝F(rear,static)-c(actual)*m*a(brake)*h(rear,optimal)/L(total)
⑧
Wherein h (front, optimal) is the final value of the optimized height of the front suspension, that is, the value when the height variation of the front and rear suspensions is consistent; h (rear, optimal) is the final value of the optimized height of the rear suspension, i.e., the value at which the amount of height change of the front and rear suspensions is uniform.
It follows that the present invention is capable of providing optimized heights for the front and rear suspensions, respectively, and calculating target braking forces for the front and rear wheels of the vehicle, respectively, based on the optimized heights of the front and rear suspensions and the actual road friction coefficients. In view of the negative influence on the stability of the vehicle caused by the pitching motion of the vehicle during braking, the strategy of optimizing the front and rear suspensions respectively is very advantageous according to the technical scheme of the invention. Therefore, according to the technical scheme of the invention, the stability of the vehicle in the automatic emergency braking process can be improved, the application and distribution of the braking force are more reasonable, and the braking efficiency is improved.
The present invention also provides a method 600 for controlling vehicle body stability during automatic emergency braking. Fig. 6 shows a flow chart of a method 600 according to a possible embodiment of the invention. Alternatively, the method 600 may be implemented by the control unit 30, and the method 600 may also be implemented by the stability system 100. Accordingly, the same description applies.
Referring to fig. 6, in step S602, the acquisition module 31 acquires parameters for subsequent calculation.
In step S604, the processing module 32 calculates the static vertical loads of the front and rear suspensions.
In step S606, the processing module 32 calculates an actual friction coefficient of the road surface.
In step S608, the processing module 32 determines the maximum vertical load of the front and rear suspensions.
In step S610, the processing module 32 calculates the vertical load transfer amount of the front and rear suspensions.
In step S612, the processing module 32 calculates an optimized height of the front and rear suspensions.
In step S614, the generation module 33 generates a first height control signal and a second height control signal.
In step S616, the processing module 32 calculates the amount of gas required in the first and second air springs.
In step S618, the generation module 33 generates the first gas amount adjustment signal and the second gas amount adjustment signal.
In step S620, the processing module 32 determines a first braking torque request and a second braking torque request.
It should be understood that the steps in the method 600 may be performed in other sequences or in parallel as long as the corresponding functions of the modules are enabled.
While the foregoing describes certain embodiments, these embodiments are presented by way of example only, and are not intended to limit the scope of the present invention. The appended claims and their equivalents are intended to cover all such modifications, substitutions and changes as may be made within the scope and spirit of the present invention.
Claims (14)
1. A control unit (30) for a stability system (100) of a vehicle, comprising:
an acquisition module (31) configured to acquire a distance of a front suspension from a vehicle center of mass and a distance of a rear suspension from the vehicle center of mass;
a processing module (32) configured to calculate a static vertical load of the front suspension based on a distance of the front suspension from a vehicle center of mass and a static vertical load of the rear suspension based on a distance of the rear suspension from the vehicle center of mass; determining the maximum vertical load of a front suspension and the maximum vertical load of a rear suspension based on the actual friction coefficient of the road surface; calculating the optimized height of the front suspension based on the static vertical load and the maximum vertical load of the front suspension and the actual friction coefficient, and calculating the optimized height of the rear suspension based on the static vertical load and the maximum vertical load of the rear suspension and the actual friction coefficient; and
a generating module (33) configured to generate a first height control signal for adjusting the height of the front suspension during automatic emergency braking of the vehicle, depending on the optimized height of the front suspension; and forming a second height control signal for adjusting the height of the rear suspension during automatic emergency braking of the vehicle in dependence on the optimized height of the rear suspension.
2. The control unit (30) of claim 1, wherein the acquisition module further acquires an actual amount of gas within a first air spring connected to a front suspension and an actual amount of gas within a second air spring connected to a rear suspension of the vehicle;
the processing module is further configured to calculate an amount of gas required by the first air spring to cause the front suspension to reach its optimized height based on the optimized height of the front suspension, and calculate an amount of gas required by the second air spring to cause the rear suspension to reach its optimized height based on the optimized height of the rear suspension;
the generation module generates a first gas amount control signal based on an actual gas amount and a required gas amount in the first air spring for adjusting the gas amount in the first air spring during automatic emergency braking of the vehicle; and generating a second gas amount control signal based on the actual gas amount and the required gas amount in the second air spring for adjusting the gas amount in the second air spring during automatic emergency braking of the vehicle.
3. The control unit (30) according to claim 1 or 2, wherein the actual friction coefficient is obtained by:
the acquisition module further acquires a road friction coefficient defaulted by the stability system and an actual acceleration of the vehicle in the running direction, and
the processing module calculates a predicted acceleration of the vehicle in the direction of motion based on the default road friction coefficient; and calculating the actual coefficient of friction based on the predicted acceleration and the actual acceleration.
4. The control unit (30) of claim 3, wherein the processing module calculates the predicted acceleration based on the formula:
a(request)＝c(default)*g
wherein a (request) is the predicted acceleration, c (default) is the default road surface friction coefficient, g is the gravity acceleration,
the processing module calculates the actual friction coefficient based on the following formula:
c(actual)＝c(default)*a(actual)/a(request)
where a (actual) is the actual acceleration of the vehicle in the direction of motion and c (actual) is the actual coefficient of friction of the road surface.
5. The control unit (30) according to claim 1 or 2, wherein the acquisition module further acquires vehicle parameters comprising vehicle mass, actual acceleration of the vehicle in the direction of motion and distance between front and rear suspensions;
the processing module is configured to calculate an optimal height of the front suspension by: calculating the difference between the maximum vertical load and the static vertical load of the front suspension to obtain the vertical load transfer amount of the front suspension; calculating the optimized height of the front suspension according to the vertical load transfer amount of the front suspension, the actual friction coefficient and the vehicle parameters; and is
The processing module is configured to calculate an optimized height of the rear suspension by: calculating the difference between the maximum vertical load and the static vertical load of the rear suspension to obtain the vertical load transfer amount of the rear suspension; and calculating the optimized height of the rear suspension according to the vertical load transfer amount of the rear suspension, the actual friction coefficient and the vehicle parameters.
6. The control unit (30) of claim 5, wherein the processing module calculates the optimal height of the front suspension by the formula:
h(front,optimal)＝[F(front,max)-F(front,static)]*L(total)/[m*c(actual)*a(brake)]
the processing module calculates the optimized height of the rear suspension through the following formula:
h(rear,optimal)＝[F(rear,max)-F(rear,static)]*L(total)/[m*c(actual)*a(brake)]
wherein F (front, max) is the maximum vertical load of the front suspension, F (front, static) is the static vertical load of the front suspension, F (rear, max) is the maximum vertical load of the rear suspension, F (rear, static) is the static vertical load of the rear suspension, a (break) is the actual acceleration of the vehicle in the moving direction, c (actual) is the actual friction coefficient, m is the vehicle mass, and l (total) is the distance between the front and rear suspensions.
7. A control unit (30) according to claim 5 or 6, wherein the processing module calculates the static vertical load of the front suspension by the formula:
F(front,static)＝m*g*L(front)/L(total)
the processing module calculates the static vertical load of the rear suspension by the following formula:
F(rear,static)＝m*g*L(rear)/L(total)
wherein m is the vehicle mass, g is the gravitational acceleration, l (front) is the distance between the front suspension and the vehicle center of mass, l (rear) is the distance between the rear suspension and the vehicle center of mass, and l (total) is the distance between the front and rear suspensions.
8. The control unit (30) according to any one of claims 1-7,
the acquiring unit is also used for acquiring the tire pressure of a front wheel connected with the front suspension, the tire pressure of a rear wheel connected with the rear suspension and environmental parameters, wherein the environmental parameters at least comprise environmental temperature and road surface humidity;
the processing module determines a maximum vertical load of the front suspension based on a tire pressure of a front wheel, an environmental parameter, and an actual friction coefficient; and is
The processing module determines a maximum vertical load of the rear suspension based on a tire pressure of a rear wheel, an environmental parameter, and an actual friction coefficient.
9. The control unit (30) according to any one of claims 1-8, wherein the processing module is further configured to:
calculating a first target braking force for a front wheel connected to the front suspension based on the optimized height and the static vertical load of the front suspension and the actual friction coefficient; and is
A second target braking force for a rear wheel connected to the rear suspension is calculated based on the optimized height and the static vertical load of the rear suspension and the actual friction coefficient.
10. The control unit (30) of claim 9, wherein the processing module calculates the first target braking force according to the formula:
Fbf＝F(front,static)+c(actual)*m*a(brake)*h(front,optimal)/L(total)
the processing module calculates a second target braking force according to the following formula:
Fbr＝F(rear,static)-c(actual)*m*a(brake)*h(rear,optimal)/L(total)
where Fbf is the first target braking force, F (front, static) is the static vertical load of the front suspension, Fbr is the second target braking force, F (rear, static) is the static vertical load of the rear suspension, a (brake) is the actual acceleration of the vehicle in the direction of motion, c (actual) is the actual coefficient of friction, m is the vehicle mass, and l (total) is the distance between the front and rear suspensions.
11. A stability system (100) for a vehicle, comprising:
a sensor unit (10) for detecting a relative distance between the host vehicle and a potential collision object;
a controller (20) coupled with the sensor unit, the controller comprising a control unit (30) according to any one of claims 1-10, the controller being configured to activate the control unit (30) according to any one of claims 1-10 upon determining that the host vehicle enters automatic emergency braking based on the relative distance; and
a suspension system (50) coupled to the controller, the suspension system including a front suspension (56) and a first air spring connected thereto, a rear suspension (57) and a second air spring connected thereto, and a suspension controller (58),
wherein the suspension controller is configured to control the amount of gas in the first air spring under control of the first height control signal so that the height of the front suspension is adjusted to be in line with its optimal height, and to control the amount of gas in the second air spring under control of the second height control signal so that the height of the rear suspension is adjusted to be in line with its optimal height.
12. The stability system (100) of claim 11, wherein said suspension controller is further configured to:
detecting the height variation of the front suspension and the height variation of the rear suspension;
when detecting that the height variation of the front suspension and the height variation of the rear suspension are equal, generating a stop instruction; and
and sending the stop instruction to a controller to stop the operation of the control unit.
13. The stability system (100) of claim 11 or 12, wherein the controller is further configured to send the first and second target braking forces to a hydraulic actuator of the vehicle, such that the actuator performs a braking maneuver of a front wheel connected to the front suspension based on the first target braking force and a braking maneuver of a rear wheel connected to the rear suspension based on the second target braking force.
14. A control method (600) for a stability system of a vehicle, optionally implemented by means of a control unit according to any of claims 1-10 and/or a stability system according to any of claims 11-13, the method comprising:
acquiring the distance between a front suspension and the vehicle mass center and the distance between a rear suspension and the vehicle mass center;
calculating the static vertical load of the front suspension based on the distance between the front suspension and the vehicle mass center, and calculating the static vertical load of the rear suspension based on the distance between the rear suspension and the vehicle mass center;
determining the maximum vertical load of a front suspension and the maximum vertical load of a rear suspension based on the actual friction coefficient of the road surface;
calculating the optimized height of the front suspension based on the static vertical load and the maximum vertical load of the front suspension and the actual friction coefficient, and calculating the optimized height of the rear suspension based on the static vertical load and the maximum vertical load of the rear suspension and the actual friction coefficient; and
generating a first height control signal for adjusting the height of the front suspension during automatic emergency braking of the vehicle in dependence on the optimized height of the front suspension; and forming a second height control signal for adjusting the height of the rear suspension during automatic emergency braking of the vehicle in dependence on the optimized height of the rear suspension.
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| CN201911337738.6A CN113085468A (en) | 2019-12-23 | 2019-12-23 | Stability system for vehicle, control unit and method thereof |
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| CN201911337738.6A CN113085468A (en) | 2019-12-23 | 2019-12-23 | Stability system for vehicle, control unit and method thereof |
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| CN113829826A (en) * | 2021-09-27 | 2021-12-24 | 科大讯飞股份有限公司 | Emergency braking control method and device combined with air suspension and electronic equipment |
| CN114103582A (en) * | 2021-11-16 | 2022-03-01 | 重庆长安汽车股份有限公司 | Automatic suspension adjusting method and automobile |
| CN116198466A (en) * | 2021-11-30 | 2023-06-02 | 比亚迪股份有限公司 | Vehicle brake control method, device and vehicle |
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