Driving performance optimization in an active suspension system

Abstract

Method for controlling a vehicle suspension for a wheel (20) via a control device (40), the method comprising: repeatedly calculating a vertical speed of the wheel (20) until the vertical speed exceeds a first speed threshold, in response to the vertical speed exceeding the first speed threshold, initiating a timer (50) while the vertical speed of the wheel (20) is repeatedly recalculated until the newly calculated vertical speed exceeds a second speed threshold, and In response to the newly calculated vertical velocity exceeding the second velocity threshold before the timer (50) exceeds a first time threshold, increasing a damping level of the suspension, where the first time threshold is varied based on the vehicle's speed.

Description

[0001] Embodiments of the present disclosure relate to active vehicle suspension systems having continuously variable or multi-step suspension dampers and methods for controlling such systems.

[0002] Vehicles may incorporate active or adaptive suspension systems to actively control vertical movements of the vehicle's wheels, rather than allowing such movements to be entirely determined by interactions with the road surface. To maximize ride comfort in such vehicles, it is usually desirable to keep the damping levels in the vehicle's shock absorbers at a relatively low level.

[0003] However, when a vehicle hits a depression (such as a pothole) in the road surface, a lower damping level allows the wheel to drop into the pothole relatively quickly. Generally, the deeper a wheel falls into the hole, the greater the impact forces generated by the wheel hitting the other side of the hole immediately before exiting. With a wheel damping level at a relatively low value, these impact forces are transmitted through the vehicle's suspension to the rest of the vehicle, compromising ride quality.

[0004] Although increasing the level of wheel damping would reduce the impact forces transmitted to the vehicle and suspension, it would negatively impact ride quality when the vehicle is traveling on a normal, smooth road surface. Therefore, it is desirable to increase damping levels only when a pothole is encountered, while maintaining damping levels at a relatively lower level when the vehicle is traveling on a smooth road surface.

[0005] DE 10 2013 211 285 A1 discloses a generic active vehicle suspension system comprising an active damping mechanism coupled to a vehicle wheel and configured to control a damping force applied to the wheel in response to a control signal. A control device is coupled to the damping mechanism and configured to generate a control signal to the damping mechanism in response to a velocity of the wheel in a downward vertical direction.

[0006] The objective technical problem to be solved can be seen as eliminating or at least mitigating the disadvantages of the prior art. This problem is solved by the subject matter of the independent patent claims.

[0007] In accordance with one aspect of the present disclosure, a method for controlling a vehicle suspension for a wheel via a controller is provided. The method includes repeatedly calculating a vertical velocity of the wheel until the vertical velocity exceeds a first velocity threshold; in response to the vertical velocity exceeding the first velocity threshold, initiating a timer while repeatedly recalculating the vertical velocity of the wheel until the recalculated vertical velocity exceeds a second velocity threshold; and in response to the recalculated vertical velocity exceeding the second velocity threshold before the timer exceeds a first time threshold, increasing a damping level of the suspension.The speed threshold and / or the first time threshold are varied based on a speed of the vehicle.

[0008] In accordance with another aspect of the present disclosure, a vehicle suspension system is provided. The vehicle suspension system includes an active damping mechanism operatively coupled to a vehicle wheel and a controller operatively coupled to the active damping mechanism.The controller is configured to repeatedly recalculate a vertical speed of the wheel until the vertical speed exceeds a first speed threshold, initiate a timer when the vertical speed exceeds the first speed threshold, and repeatedly recalculate the vertical speed of the wheel until the recalculated vertical speed exceeds a second speed threshold, and, if the recalculated vertical speed exceeds the second speed threshold before the timer exceeds a first time threshold, increase the damping level applied to the wheel and vary the first time threshold based on a speed of the vehicle.

[0009] In accordance with yet another aspect of the present disclosure, a method for controlling a vehicle suspension for a wheel via a controller includes initiating a timer and maintaining a damping level of an adjustable damping mechanism of the vehicle suspension at an original value, repeatedly calculating a vertical speed of the wheel until the vertical speed exceeds a speed threshold and the timer does not exceed a time threshold, the time threshold being varied based on a speed of the vehicle, and, in response to the vertical speed exceeding the speed threshold before the timer exceeds the time threshold, sending an adjustment signal to the adjustable damping mechanism of the vehicle suspension to increase the damping level.

[0010] In accordance with another aspect of the present disclosure, a vehicle suspension system includes an adjustable damping mechanism operatively coupled to a vehicle wheel and a controller operatively coupled to the active damping mechanism.The controller is configured to initiate a timer and maintain a damping level of the adjustable damping mechanism at an original value, repeatedly calculate a vertical speed of the wheel until the vertical speed exceeds a speed threshold and the timer does not exceed a time threshold, wherein the time threshold is varied based on a speed of the vehicle, and send an adjustment signal to the adjustable damping mechanism to increase the damping level in response to the vertical speed exceeding the speed threshold before the timer exceeds the time threshold.

[0011] In accordance with another aspect of the present disclosure, a method for controlling a vehicle suspension includes initiating a timer and maintaining a damping level of an adjustable damping mechanism at an original value when the vertical speed of a wheel exceeds a first comfort threshold, and increasing the damping level of the mechanism if the vertical speed of the wheel exceeds a second speed threshold before the timer exceeds a time threshold, wherein at least one of the time thresholds is varied on a vehicle speed basis.

[0012] Further advantageous embodiments of the invention are shown in the figures. Fig. 1 is a schematic illustration of a portion of an active vehicle suspension system for implementing a damping force control routine in accordance with an embodiment of the present invention. Fig. 2 is a block diagram of an exemplary adjustable damping mechanism controllable in accordance with a damping force control sequence in accordance with an embodiment of the present disclosure. Fig. 3 is a block diagram showing a flow of a damping force control process for controlling forces in the active damping mechanism according to an exemplary embodiment. Fig. 4 is a block diagram showing a vehicle wheel traveling along a road surface before entering a pothole or other depression in the road surface, according to an exemplary embodiment. Fig. 5 is a block diagram showing a vehicle wheel moving along a road surface after entering a pothole or other depression in the road surface, according to an exemplary embodiment. Fig. 6 is a block diagram showing a flow of a damping force control process for controlling forces in active damping mechanisms according to an exemplary embodiment. Fig. 7 schematically depicts a front wheel and a rear wheel of a vehicle moving along a road surface having a depression, according to an exemplary embodiment.

[0013] Fig. Figure 1 shows a schematic representation of a portion of one embodiment of an active vehicle suspension system (generally designated by reference numeral 10) configured to control damping forces provided by a damping mechanism (e.g., shock absorbers) of the vehicle's suspension. The active vehicle suspension system includes such active damping mechanisms operatively coupled to associated wheels of the vehicle. These damping mechanisms are configured to control a damping force applied to the wheel in response to control signals generated by a computer processor. The computer may be incorporated into a suspension system controller 40, which is part of an overall vehicle system control system (not shown).

[0014] The active suspension system 10 includes an embodiment of a damping level control sequence as described herein, which can be used to control the damping forces responsive to an interaction between a vehicle wheel supported by the damping element and a depression in a road surface on which the wheel travels. Spring elements and various other elements of a conventional active vehicle suspension system can also be incorporated into the system 10, are in Fig. 1 but not shown.

[0015] At the Fig. 1, the suspension system 10 includes wheel position sensors 12 (indicated by 12-1, 12-2, 12-3, and 12-4) operatively coupled to a corresponding one of the vehicle wheels 20-1, 20-2, 20-3, 20-4 and also to the controller 40. The sensor(s) 12 are configured to sense the vertical position of the corresponding vehicle wheel (i.e., the component of vehicle motion along a vertical or "y" axis 333 extending through the wheel center) and relative to a reference location with respect to which the wheel is movable. In one embodiment, the reference location is a location on a chassis 22 of the vehicle. In one embodiment, signals representative of the vehicle position y are continuously received from sensors 12 by a microcomputer 30 for processing in a manner described below.

[0016] At the Fig. In the embodiment shown in Figure 1, the suspension system 10 also includes a microcomputer 30 operatively coupled to the sensors 12 and configured to process signals indicative of wheel attitude in accordance with the control sequence to generate control signals used to control the damping levels in the adjustable damping mechanism operatively coupled to each wheel. The computer 30 is configured to determine the vertical velocity of the wheel while the wheel is interacting with the road surface. In one embodiment, the vertical velocity of the wheel is determined by taking the time derivative (dy / dt) of the wheel position over a predetermined period of time.In another embodiment, the vertical velocity of the wheel is determined by integrating a value provided, for example, by an accelerometer configured to measure the rate of change of the wheel's velocity in a vertical direction. Computer 30 may include a memory for storing the damping level control sequence and any additional data or programs required for operation of the suspension system. Computer 30 is incorporated into or operatively coupled to suspension control device 40.

[0017] If desired, one or more known filters 32 (e.g., bandpass filters) may be operatively coupled to sensors 12 for filtering noise components from the sensor signals in a known manner. Additionally, a preprocessing circuit 34 may be operatively coupled to sensors 12, if necessary, to convert signals received from sensors 12 into a form suitable for processing by computer 30. If necessary, the control signals generated by microcomputer 30 may be transmitted to a drive circuit or postprocessor 36 for conversion into a form to which adjustable damping mechanisms 18 are responsive.The drive circuit may be configured to process the received control signals into a form suitable for operating, for example, hydraulically actuated cylinders, cylinders actuated by solenoids or electromagnetically energized proportional valves, cylinders containing a magnetorheological fluid, or any other suitable types of active cylinders or shock absorbers.

[0018] A timer element 50 is also incorporated into or operatively coupled to the control device 40. The timer 50 is used in the manner described below to measure the lengths of different time periods during which the vertical position of the vehicle wheel changes as the wheel falls into a depression in the road surface.

[0019] If desired, any elements (e.g., computer 30, filter 32, etc.) required to interface between the sensors 12 and the active damping mechanisms may be incorporated into a suspension control device operatively coupled to the damping mechanisms and configured to generate control signals to the damping mechanisms. As described above, the control device controls the adjustment of the damping levels by receiving the sensor signals and generating corresponding control commands to the active damping mechanism 18.

[0020] With reference to the Fig. 1 and Fig. 2, the suspension system 10 includes an independently operable active damping mechanism 18 operatively coupled to each vehicle wheel between an unsprung mass and a sprung mass of the vehicle. The damping mechanism 18 coupled to each of the wheels is operatively independent of the damping mechanisms 18 coupled to the other wheels.

[0021] Fig. Figure 2 shows a particular structure of an adjustable damping mechanism that can be controlled by the control device 40 to implement embodiments of the damping force control sequence described herein. Referring to Fig. 1 and Fig. 2, each of the damping mechanisms 18-1, 18-2, 18-3, and 18-4 includes a corresponding shock absorber provided between an unsprung mass and a sprung mass of the vehicle. Each shock absorber has a hydraulic cylinder 17 divided into upper and lower fluid chambers by a piston 11 and supported by the unsprung mass of the vehicle. A piston shaft 13 of the piston 11 is supported by the sprung mass of the vehicle. The upper and lower fluid chambers of the hydraulic cylinder 17 are connected to each other by a variable orifice 14. The opening size of the variable orifice 14 is controlled by the operation of an associated stepping motor 15 to control the damping force of the shock absorber. Fig. In the embodiment shown in Figure 2, the stepper motor 15 on each of the adjustable damping mechanisms 18 is driven to control the size of an associated variable orifice 14 to control the damping force provided by the shock absorbers in the adjustable damping mechanisms 18. Therefore, in this embodiment, the drive circuit 36 ​​drives each of the stepper motors 15 in response to control signals received from the computer 30. The lower fluid chamber of the hydraulic cylinder 17 is connected to an associated gas spring unit 16, which is provided to absorb the volume change in the lower fluid chamber caused by the movement of the piston shaft 13.

[0022] As mentioned above, instead of units that use stepper motors to control the damping force of the shock absorbers, adjustable damping mechanisms 18 in accordance with embodiments of the present disclosure may comprise hydraulically actuated cylinders, for example, cylinders actuated by solenoids or electromagnetically energized proportional valves, cylinders containing a magnetorheological fluid, or any other suitable type of active cylinder or shock absorber. However, any adjustable damping mechanism 18 may be of a known type that can be controlled by methods and components described herein to adjust the damping force applied to an associated wheel and that is capable of the dynamic response required to provide the variations in damping levels described herein.

[0023] In the embodiments of the present disclosure, the computer 30 is designed to repeatedly execute the control flow shown in the flowchart of Fig. 3. Therefore, the control of a damping force that damps vertical movement of the wheel with respect to the vehicle body at the right front wheel will be described below with reference to Fig. 3 described.

[0024] Assuming that the computer 30 has been connected to an electrical power supply (not shown) by operating an ignition switch (not shown) of the vehicle, the computer 30 initializes the control program of the Fig. 3 and repeats the execution of processing steps 290-320 of the program.

[0025] Fig. Figure 3 shows one embodiment of a control sequence for the portion of the active suspension system that controls the damping level applied to a single wheel 20 of the vehicle. It will be appreciated that the same control sequence can be applied independently to any of the vehicle's wheels, depending on the road conditions encountered by that wheel.

[0026] The control sequence controls the damping force applied to the wheel in response to a protocol that is activated when the time rate of change of the wheel's vertical position indicates that the wheel may have encountered a pothole or other depression in the road surface. Fig. 4 and Fig. 5, the parameter "y" represents a current position of the wheel 20 along a vertical axis relative to a predetermined reference location (e.g., a location on the chassis 90) relative to which the wheel is vertically movable, and the parameter D represents a damping force level applied to the wheel. The arrow "A" represents the direction of travel of the vehicle along the surface 902.

[0027] At block 290 of the control flow, the parameters y and D are at initial levels representing a state of an associated damping element 18 before the wheel 20 encounters a pothole 900. Fig. 4 also shows the wheel 20 traveling along the road surface 902 prior to entering the pothole 900. Initially, the wheel 20 travels along a relatively smooth portion of the road 902, and the elements of the suspension system are adjusted to provide a damping level D having an initial (i.e., "normal") reference value D1. The initial value of D1 may be any value within the controllable range of damping level D settings, depending on the specific features and elements of the particular suspension system. In the embodiments of the present disclosure described herein, the initial damping level D1 is adjusted to provide a relatively low degree of damping for wheel travel, thus providing a relatively "softer" suspension for improved ride quality.In addition, the vertical position y1 of the wheel relative to the reference point while the wheel is traveling along the smooth road surface is assigned a value of “0” (zero).

[0028] At Block 300 of the Fig. 3 and as in Fig. As shown in Figure 5, the wheel 20 has encountered a relative depression 900 in the road 902, which may or may not be a pothole. Due to the depression 900, the road support is removed from the wheel 20, and the wheel begins to fall into the depression. The position sensor 12, which is operatively coupled to the wheel, continuously detects the vertical wheel position "y" as the wheel falls into the depression and provides this position to the computer 30.

[0029] In the manner described above, and after the elapse of a predetermined time interval Δt, the new, lower position of the wheel is assigned to the variable y2 by the computer. The computer 30 then calculates the absolute value of the time rate of change of the wheel's position Δy1 = y2-y1 during the predetermined time period Δt (i.e., the computer calculates the time derivative of the position coordinate y, which is (dy / dt)). This calculated time rate of change of the wheel position is assigned to the variable V and represents the instantaneous velocity of the wheel in the vertical direction at time Δt and at the wheel position y2. For the purpose of adjusting the damping forces applied to the wheel, the contemplated range of values ​​of Δt includes values ​​of less than 10 milliseconds. In a particular embodiment, the value of Δt is 2 milliseconds.The range of values ​​of Δt depends on the type of suspension concept and the components used, as well as other relevant factors. However, the value of Δt can be set to any desired value depending on the requirements of a particular application. As mentioned above, the predetermined value of Δt can be stored, for example, in a lookup table in the computer memory. In general, and for the purpose of adjusting the damping forces applied to the wheel, it is desirable that the time interval Δt be as short as possible so that a rapid determination can be made as to whether the threshold value Th1 has been exceeded and whether further, rapidly successive measurements of the wheel position y are required.

[0030] At block 302, the calculated value of the instantaneous speed V is compared with a first predetermined speed threshold Th1. If V is lower than Th1, a "false" condition is detected, and the process returns to block 290 (i.e., the damping level D is maintained at the initial reference value of D1). The damping level is maintained until the wheel encounters a depression in the road. However, if V is equal to or greater than Th1, a "true" condition is detected. The fact that the instantaneous speed V has reached or exceeded the threshold Th1 is taken as an indication that the wheel is potentially beginning to fall into a depression 900.Satisfaction of this condition is interpreted as confirmation that the wheel has encountered a potential pothole condition, and following this confirmation, the wheel's "y" position is measured at very short time intervals to monitor the wheel's continued fall (if any) into the depression. The occurrence of a "true" condition indicates that the change in wheel position (Δy) during the elapsed time Δt (i.e., the speed of the vertical component of the wheel's movement into the depression), as measured, is sufficient to justify initializing and activating timer 50 to measure the elapsed time during any further changes in wheel position. In this case, the process proceeds to block 304.

[0031] The predetermined speed thresholds used by the control flow described herein may, for example, be stored in a lookup table in computer memory. The predetermined speed thresholds may be calculated and / or iteratively determined through experimentation for each configuration of a wheel and associated suspension system and then stored in computer memory. The predetermined speed thresholds are selected with a view to minimizing the detrimental effects on the ride and maximizing the probability of detecting an actual pothole event as soon as possible upon its occurrence. The values ​​typically range between 0.2 meters / second and 5 meters / second. Factors affecting the range of values ​​include suspension tuning, vehicle speed, vehicle tire characteristics, and other factors.The ranges of values ​​for the various speed thresholds can be based on data collected from both pothole and non-pothole driving events. Using such data to program or "fine-tune" the suspension system facilitates rapid detection of actual potholes while helping to minimize negative ride impacts due to suspension increases triggered by "false positive" detections of pothole events.

[0032] At block 304, once it is determined that the wheel may have encountered a pothole event, the timer is set to an initial value of T=0, after which it is allowed to increment.

[0033] The loop or subroutine formed by blocks 305, 306, and 308 aims to compare the instantaneous speed V of the wheel at successive times with another predetermined speed threshold Th2 until either (1) the timer value T exceeds a predetermined first threshold T1, or (2) the instantaneous speed V of the wheel exceeds the predetermined speed threshold Th2. As above, the instantaneous velocities V at successive times are calculated by taking the time derivative of the vertical position y of the wheel (dy / dt), where dt is the time elapsed between any two consecutive times at which the wheel attitude y is measured, and dy is the additional vertical distance the wheel has fallen during the time dt.In the embodiments described herein, the range of values ​​for T1 is 0.001 to 0.100 milliseconds. Generally, the time threshold T1 is longer than the value of Δt. The length of T1 should be sufficient to enable discrimination of an actual pothole event from sensor noise based on passing the speed threshold within the time threshold T1. The ranges of values ​​for the time threshold T1 can be based on data collected from both pothole and non-pothole driving events. Using such data to program or "fine-tune" the suspension system facilitates rapid detection of actual potholes while helping to minimize adverse ride impacts due to suspension increases triggered by "false positive" detections of pothole events.

[0034] At block 305, the timer reading T since initialization is compared with the first predetermined time threshold T1. If the timer reading T is greater than the value of T1 (i.e., if the time elapsed since the driver was reinitialized is greater than T1), a "true" condition is detected, and the damping level D is maintained at the reference value D1. If the time elapsed since the timer was reinitialized is less than T1, a "false" condition is detected, and the process proceeds to block 306, where the instantaneous wheel velocity V = Δy / T (i.e., dy / dt) is recalculated.

[0035] At block 306, the newly calculated value of the instantaneous wheel speed V is compared to a second predetermined threshold value Th2. If the new wheel speed V exceeds Th2, a "true" condition is detected and it is determined that the change in wheel position (Δy) over the elapsed time T (i.e., the new instantaneous speed of the wheel into the depression) is sufficient to justify an increase in the damping level D. The process therefore proceeds to block 310. However, if the instantaneous wheel speed V is equal to or less than Th2, a "false" condition is detected and the process proceeds to block 308, where the instantaneous wheel speed V is recalculated after the elapse of an additional predetermined time interval Δt (i.e., after T has been increased by Δt).The process then proceeds to block 305 to determine whether the total time T elapsed since the timer was initialized is greater than the time threshold T1. If T is greater than T1, control flows back to block 290.

[0036] In the manner described above, loop 305-306-308 repeats as long as the timer value T does not exceed the threshold T1 and as long as the instantaneous wheel speed V does not exceed the speed threshold Th2. If the timer value T exceeds the first timer threshold T1 without the wheel speed V exceeding the speed threshold VTh2, a "false" condition is detected, and it is determined that the wheel has not moved, or has not moved at a sufficient speed, during the elapse of time period T1 to justify an increase in the damping level D. The damping level is therefore reset to the initial reference value D1.However, if the wheel speed V exceeds the speed threshold Th2 in block 306 before the timer value T exceeds a first timer threshold T1, a "true" condition is detected, and the process proceeds to block 310, where the damping level D is increased by a predetermined value ΔD to a higher value of D2. In other words, after each time interval Δt elapses, the instantaneous wheel speed V is recalculated, and both the timer reading T and the instantaneous wheel speed V are compared to respective thresholds to determine whether the damping level D needs to be changed. Incremental increases in the damping level are implemented as a "ramp" or "decline" extending between the initial and new damping levels.If the instantaneous wheel speed V exceeds the threshold Th2 within the time period defined by T1, a "true" condition is detected and the damping level is increased in block 310. However, if the instantaneous wheel speed V remains equal to or lower than the first threshold Th2 within the time period defined by T1, the damping level D is reset to the initial reference value D1.

[0037] The loop formed by blocks 310, 312, and 314 is directed to gradually increase the damping level by a predetermined amount after the elapse of each time interval Δt until either (1) the timer reading T after initialization exceeds a second timer threshold T2, or (2) the instantaneous wheel speed V exceeds a third speed threshold Th3.

[0038] Cases where the wheel continues to exceed the speed thresholds within the associated time intervals indicate a lack of support for the wheel to a depth sufficient to cause the wheel to continue to fall in the "y" direction.

[0039] The amounts by which the damping level D is increased during execution of the control sequence described herein may be constant for each step, or the amounts may be determined according to the requirements of a particular application. The amounts by which the damping level D is increased may be determined according to the requirements of a particular suspension system design, the range of damping settings available with a particular type of damping, the method used to activate the damping, and other relevant factors. Furthermore, the number of steps or increments into which the range of damping levels can be divided to facilitate the incremental increases in the damping levels may be determined according to the requirements of a particular application.

[0040] At block 310, the damping level is increased by a predetermined amount ΔD to level D2. The instantaneous wheel speed V is recalculated after another time interval Δt has elapsed (i.e., after the timer value T has been incremented by another Δt from its value used in the previous instantaneous speed calculation).

[0041] At block 312, the timer reading T is compared to a second predetermined time threshold value T2. If the timer reading T is greater than the value of T2 (i.e., if the time elapsed since the timer was initialized at block 304 is greater than T2), a "true" condition is detected, and the attenuation level D is reset to the reference value D1. However, if the time elapsed since the timer was initialized is less than T2, a "false" condition is detected, and the process proceeds to block 314.

[0042] If, in block 314, the instantaneous wheel speed V is equal to or lower than the threshold Th3, a "false" condition is detected, and the process returns to block 310, where the damping level is again increased by a predetermined amount ΔD, and the instantaneous wheel speed V is recalculated after the elapse of an additional predetermined time interval Δt. The process then returns to block 312 to determine whether the elapsed time T is greater than the time threshold T2.

[0043] In the manner described above, the loop 310-312-314 repeats as long as the timer value T does not exceed the second timer threshold T2 and as long as the instantaneous wheel speed V does not exceed the third speed threshold Th3. If the timer value T (measured since initialization) exceeds the second timer threshold T2 without the wheel speed V exceeding the speed threshold Th3, a "false" condition is detected, and it is determined that the wheel has not moved, or has not moved at a sufficient speed, during the elapse of time period T2 to justify an increase in the damping level. The damping level is therefore reset to the initial reference value D1.

[0044] However, if the wheel speed V exceeds the threshold Th3 before the timer value T exceeds the second timer threshold T2, a “true” condition is detected, and it is determined that the change in wheel position (Δy) during the elapsed time T (i.e., the speed of vertical movement of the wheel into the depression) is sufficient to warrant a further increase in the damping level D to the maximum tuned damping level, D MAX , in Block 316.

[0045] As the process runs through the loop defined by blocks 310-312-314, the attenuation level continues to be increased incrementally so that if and when the maximum attenuation level D MAX it is necessary to increase the attenuation level from the current attenuation level D MAX is lower than increasing the damping level from D1 to D MAXThis helps to minimize or eliminate the “shock” or “bump” effect caused by a sudden, sharp shift in hydraulic pressure required to go from D1 to D MAX and which is noticeable to the vehicle's occupants. The process described here also allows the system damping force to be increased incrementally between a first predetermined value and a next, higher predetermined value. Therefore, if it is determined that the next higher predetermined value is required, the magnitude of the remaining increase required to reach the next higher predetermined value is less than the magnitude of the distance between the first predetermined value and the highest predetermined value.

[0046] At block 320 the damping level is set to D = D MAXheld until the elapsed time, as indicated by the timer value T, reaches a predetermined stop point T STOP The attenuation level is then reset to the initial reference value D1.

[0047] By gradually increasing the damping forces exerted by the damper in response to the continued dropping of the wheel into the road depression, the embodiments of the control sequence described herein help minimize the amount of damping force increase and delay the implementation of the force increase as long as possible, so that the relatively higher ride quality offered by a lower damping level is maintained for as long as possible. To achieve such a gradually increasing damping force, a control device for a suspension system may use a plurality of wheel speed thresholds, thereby minimizing or avoiding a sudden, extensive shift in hydraulic pressure when changing from an initial damping level (e.g., damping level D1) to a maximum damping level (e.g., maximum damping level D MAX) is advanced. As described above with reference to the exemplary embodiment of the Fig. 3, three threshold values ​​Th1, Th2, and Th3 may be compared to an instantaneous wheel speed V. Various numbers of wheel speed threshold values ​​are contemplated in the present disclosure for comparison to an instantaneous wheel speed, such as one, two, three, four, five, six, seven, eight, nine, or ten or more threshold values.

[0048] With reference to Fig. Figure 6 shows a damping force control process using four threshold values. A section of the process shown in Fig. 6, uses steps similar to those of the process described above with reference to the exemplary embodiment of the Fig. 3. The process may begin at block 400, where elements of a vehicle suspension system maintain an initial damping level D of D1, as discussed above with reference to block 290 of the Fig. 3. At block 410, a vehicle wheel encounters a depression (for example, depression 900 in the Fig. 4 and Fig. 5) which causes the wheel to fall into the recess, and a sensor (for example the sensor 12 in the Fig. 4 and Fig. 5) to detect the vertical position of the wheel as it falls into the depression, which is used to determine an instantaneous wheel speed V as described above with reference to block 300 of the Fig. 3 discussed.

[0049] The instantaneous wheel speed V is compared with a first predetermined speed threshold value Th1, as described above with reference to block 302 of the Fig. 3. If the wheel speed V is lower than Th1, a "false" condition is detected and the process returns to block 400. If the wheel speed is equal to or exceeds Th1, a "true" condition is detected and the process proceeds to block 430, where the controller sets a timer to an initial value of T=0. The controller then determines whether the timer value T exceeds a predetermined first time threshold T1 at block 440. If so, a "true" condition is detected and the process returns to block 400, causing the damping level to be maintained at the original value D1. If the timer value T does not exceed the first predetermined time threshold T1, a "false" condition is detected and the process proceeds to block 450, where the instantaneous wheel speed V is compared to a second predetermined threshold Th2.If the instantaneous wheel speed V is equal to or does not exceed the second predetermined speed threshold Th2, a "false" condition is detected and the process proceeds to block 460 where the timer value T is incremented and the instantaneous wheel speed V is recalculated after a lapse of a time interval, as described above in connection with block 308 in FIG. Fig. 3 before the process returns to block 440. If the instantaneous wheel speed V exceeds the second predetermined threshold Th2, a "true" condition is detected and the process continues.

[0050] At block 470, for example, the damping level D is increased by a predetermined amount, the timer value T is increased, and the instantaneous wheel speed V is determined as described above with reference to block 310 in Fig. 3, recalculated. The process then proceeds to block 480 where the controller determines whether the timer value T exceeds a second predetermined time threshold T2. If so, a "true" condition is detected and the process returns to block 400 where the damping level D is caused to return to the original value D1. If the timer value T does not exceed the second predetermined time threshold T2, the process proceeds to block 490 where the controller determines whether the instantaneous wheel speed V exceeds a third predetermined speed threshold Th3. If not, a "false" condition is detected and the process proceeds to block 500 where the timer value T is incremented and the instantaneous wheel speed V is recalculated before the process returns to block 480.If the instantaneous wheel speed V exceeds the third predetermined threshold Th3, the process proceeds to block 510 where the damping level D is increased, such as by a predetermined amount, the timer value T is increased, and the instantaneous wheel speed V is increased, similar to the process described above with reference to block 310 in FIG. Fig. 3 was discussed, is recalculated.

[0051] The loop represented by blocks 520, 530, 540 illustrates the use of additional thresholds, such as a third predetermined time threshold T3 and a fourth predetermined time threshold Th4. For example, the timer value T is compared to the third predetermined time threshold T3 at block 520. If the timer value T exceeds the third predetermined time threshold T3, a "true" condition is detected, and the process returns to block 400, where the damping level D is caused to return to the original value D1. If the timer value T does not exceed the third predetermined time threshold T3, the process proceeds to block 530, where the instantaneous wheel speed V is compared to a fourth predetermined speed threshold Th4.If the instantaneous wheel speed V does not exceed the fourth predetermined speed threshold Th4, the process proceeds to block 540, where the timer value T is incremented and the instantaneous wheel speed V is recalculated. If the instantaneous wheel speed V exceeds the fourth predetermined speed threshold Th4, the process proceeds to block 550, where the damping level D is set to a maximum damping level D. MAX as above with reference to block 316 in Fig. 3, and the process continues to block 560 where the attenuation level D is set to the maximum attenuation level D MAX is held until the timer value T reaches a predetermined time, as described above with reference to block 320 in Fig. 3 discussed.

[0052] By using a plurality of thresholds, such as timer thresholds and / or wheel speed thresholds in the process of the exemplary embodiment of the Fig. 6, damping forces can be gradually increased in response to the continued fall of the wheel, minimizing damping force increases while delaying the implementation of the damping force increase as long as possible, thereby maintaining a relatively higher ride quality for as long as possible while minimizing or avoiding sudden, sharp shifts in hydraulic pressure for a damping system.

[0053] Although the exemplary process of Fig. 6 with reference to the use of four wheel speed thresholds Th1, Th2, Th3, and Th4, the processes of the various exemplary embodiments described herein may use other numbers of wheel speed thresholds, as discussed above, to gradually increase the damping force and minimize or prevent large shifts in the damping force. The damping force shifts performed by steps 520, 530, 540 in Fig. For example, the loop illustrated in Figure 6 may be duplicated one or more times between steps 530 and 550, with each duplicate loop using a different wheel speed threshold and timer threshold.

[0054] The present disclosure further contemplates the use of a confidence level when determining whether a vehicle wheel has encountered a depression in a ground surface. The various exemplary embodiments herein contemplate the controller (e.g., controller 40) calculating a confidence level based on more than one wheel speed threshold. For example, a controller may calculate a confidence level based on whether a calculated wheel speed reaches one or more wheel speed thresholds, whether the calculated wheel speed reaches the wheel speed thresholds within a predetermined time (e.g., according to the timer thresholds), and according to a vertical displacement (e.g., vertical position y1 of a wheel in Fig. 5) of a wheel.

[0055] Vehicle speed can affect the impact force experienced by a vehicle wheel when the wheel encounters a depression in a road surface. For example, higher vehicle speeds may result in reduced impact forces for a vehicle wheel when the wheel encounters a depression. This may occur because there is less time for the wheel to fall into the depression while the vehicle is traveling forward at high speed. Therefore, there may be less demand for dampers at high vehicle speeds due to the reduced amount of impact forces encountered at higher vehicle speeds.

[0056] In view of this consideration, the present disclosure considers different thresholds depending on the vehicle speed. Time thresholds are varied as the vehicle speed increases. Time thresholds (for example, the time thresholds T1, T2, T3 in the Fig. 3 and Fig. 4) are varied with vehicle speed. For example, controller 40 may be configured to decrease the values ​​for time thresholds as vehicle speed increases so that there is less time for a calculated wheel speed to exceed a wheel speed threshold, resulting in less damping at higher vehicle speeds given the reduced impact of dips on a vehicle at higher speeds. Conversely, as vehicle speed decreases, controller 40 may be configured to increase the values ​​for the time thresholds so that more time is allocated for a calculated vehicle speed to exceed a wheel speed threshold, thereby facilitating increases in damping at lower vehicle speeds.According to an exemplary embodiment, a time threshold may increase or decrease by about 0.001 second to about 0.05 second at vehicle speeds ranging from about 10 to 80 mph.

[0057] In addition to increasing the time thresholds, the wheel speed thresholds (for example, the thresholds Th1, Th2, Th3, Th4 in the Fig. 3 and Fig. 4) be varied with vehicle speed. For example, the controller 40 may be configured to increase the values ​​of the wheel speed thresholds as the vehicle speed increases. Due to the increased values ​​of the vehicle speed thresholds, incremental increases in the damping level only occur when a calculated wheel speed is large enough to exceed the increased values ​​for the wheel speed thresholds, resulting in less damping at higher vehicle speeds. Conversely, as the vehicle speed decreases, the controller 40 may be configured to decrease the values ​​for the wheel speed thresholds such that lower values ​​for a calculated wheel speed are required to exceed the wheel speed thresholds, facilitating increases in the damping level at lower vehicle speeds.According to an exemplary embodiment, a wheel speed threshold may increase or decrease by about 0.3 m / s to about 2 m / s at vehicle speeds ranging from about 10 to 80 mph.

[0058] The present disclosure contemplates controlling a damping level for one or more rear wheels of a vehicle based on conditions of one or more front wheels of the vehicle. Thus, according to an exemplary embodiment, a rear wheel of a vehicle may be controlled based on how a corresponding front wheel (e.g., a front wheel ahead of the rear wheel, such as a left front wheel ahead of a left rear wheel) is controlled. For example, if a controller determines that a front wheel has entered a depression in a road surface, as described above with reference to the exemplary embodiments of the Fig. 4 to 6, the control device can control a damping level for a rear wheel behind the front wheel.

[0059] Although there is little time for the controller and suspension system to react to a front wheel entering a depression and adjust a damping rate for the front wheel accordingly, the controller can use information obtained for the front wheel to control a damping level for a rear wheel before or at the moment a rear wheel encounters the depression. A damping level for the rear wheel can therefore be prepared, for example, by increasing the damping level for the rear wheel, to minimize a load transferred to the suspension system when the rear wheel encounters the depression.For example, if a front wheel encounters a depression in a road surface, the front wheel may experience an acceleration of approximately 80 G (that is, eighty times the force of gravity) if no control of the damping level for the front wheel is performed, or approximately 60 G if the damping level is controlled in the short amount of time in which the suspension system and control device can react to the front wheel encountering the depression. However, because a rear wheel is some distance behind the front wheel at the time the front wheel encounters the depression, the system can prepare for the event before the rear wheel encounters it. The rear wheel may therefore experience an acceleration of approximately 20 G to 30 G due to the control of the damping level for the rear wheel based on information obtained while controlling the front wheel.

[0060] With reference to Fig. 7 is a side schematic view of a front wheel 600 and a rear wheel 610 of a vehicle traveling along a road surface 902. Each of the front wheels 600 and rear wheels 610 is coupled to an adjustable damping mechanism 18 that is coupled to the vehicle chassis 90 and has a respective sensor 12 configured to measure the vertical position of a respective wheel 600 or 610, as described above with reference to the exemplary embodiment of the Fig. 4 and Fig. 5. The controller 40 is in signal communication with sensors 12 and the adjustable damping mechanism 18 so that the controller 40 can receive signals from sensors 12 and control the adjustable damping mechanisms 18, as discussed above in the exemplary embodiments.

[0061] According to an exemplary embodiment, the damping level for the damping mechanism 18 of the rear wheel 610 can be controlled based on information obtained for the front wheel 600 when the front wheel 600 encounters a depression 900 in the road surface 902. For example, while the front wheel 600 falls into the depression and its adjustable damping mechanism 18 is, for example, according to the exemplary embodiments of the Fig. 3 and Fig. 6, the adjustable damping mechanism 18 for the rear wheel 610 may be controlled using the damping level selected for the adjustable damping mechanism 18 of the front wheel 600. For example, while the calculated instantaneous wheel speed V for the front wheel 600 exceeds predetermined wheel speed thresholds (e.g., thresholds Th1, Th2, Th3, Th4), such as within a predetermined time (e.g., within time thresholds T1, T2, T3), the damping level for the adjustable damping mechanism 18 of the front wheel 600 is increased, as described above with reference to the exemplary embodiments of Fig. 3 and Fig. 6 discussed.

[0062] According to an exemplary embodiment, the adjustable damping mechanism 18 of the rear wheel 610 can be controlled to use the same damping level as the front wheel 600. For example, the damping level for the adjustable damping mechanism 18 of the rear wheel 610 can be controlled assuming that the rear wheel 610 encounters the depression 900 or before the rear wheel 610 encounters the depression 900.The distance 620 between the front wheel 600 and the rear wheel 610, such as between vertical axes 333 of the wheels, a current vehicle speed (e.g., determined from one or more vehicle sensors indicative of vehicle speed, such as wheel speed sensors, engine shaft speed sensors, and other sensors known to those of ordinary skill in the art for determining vehicle speed), may be used, for example, to determine a time at which the rear wheel 610 encounters the depression. The distance 620 may, for example, correspond to a wheelbase of the vehicle. According to an exemplary embodiment, the damping level for the adjustable damping mechanism 18 of the rear wheel 610 is controlled before the rear wheel 610 encounters the depression 900, for example, by using a portion of the distance 620 between the wheels 600, 610.For example, the portion of distance 620 may be about 60% to about 80% of distance 620, such as about 70% of distance 620.

[0063] By using embodiments of the control sequence described here, the implementation of the damping force increase to D MAX (which has the greatest negative impact on ride quality) is ideally limited to cases where it is most desirable (i.e., cases where the wheel encounters a relatively deep pothole or depression). This increase in damping level limits the depth to which the wheel drops into the depression and helps minimize the jarring impact caused by the wheel hitting the opposite side of the pothole while climbing out of the hole.

[0064] A control flow in accordance with an embodiment of the present disclosure may be incorporated as a subroutine in a broader new or existing control flow designed to control additional elements of the suspension system, such as the active damping mechanisms, and / or the elements of the active suspension system based on inputs from both the wheel position sensors and other types of sensors.

[0065] As described above, a control flow in accordance with an embodiment of the present disclosure enables efficient operation of vehicle suspension systems having gradually variable or multi-step suspension dampers to maximize ride quality and reduce stress on the suspension system.

[0066] As described herein, one embodiment of the present disclosure includes an active vehicle suspension system having an active damping mechanism operatively connected to a vehicle wheel and configured to control a damping force applied to the vehicle in response to a control signal. A controller is operatively coupled to the damping mechanism and configured to generate a control signal to the damping mechanism in response to a velocity of the wheel in a downward vertical direction.

[0067] As described herein, another embodiment of the present disclosure provides a method for controlling a damping level applied to a vehicle in an active suspension system. The method includes the steps of determining a velocity defined as a rate of change of a vertical position of the wheel during a first predetermined period of time, comparing the velocity to a threshold velocity, and, if the velocity is greater than the threshold velocity, increasing the damping level.

[0068] As also described herein, another embodiment of the present disclosure provides a method for applying a damping force to a wheel moving in a vertically downward direction. The method includes the steps of measuring a time during which the wheel moves in the direction, measuring a speed of the wheel in the direction, comparing the time to a threshold and the speed to another threshold, and, if the time does not exceed the threshold and the speed exceeds the other threshold, applying a maximum available damping force to the wheel.

[0069] It is understood that the above descriptions of embodiments of the present disclosure are merely illustrative. Therefore, the various structural and operational features disclosed herein are susceptible to numerous modifications within the capabilities of one of ordinary skill in the art without departing from the scope of the present disclosure as defined by the appended claims.

Claims

[1] A method for controlling a vehicle suspension for a wheel (20) via a control device (40), the method comprising: repeatedly calculating a vertical speed of the wheel (20) until the vertical speed exceeds a first speed threshold in response to the vertical speed exceeding the first speed threshold, initiating a timer (50) while repeatedly recalculating the vertical speed of the wheel (20) until the recalculated vertical speed exceeds a second speed threshold, and in response to the newly calculated vertical speed exceeding the second speed threshold before the timer (50) exceeds a first time threshold, increasing a damping level of the suspension, wherein the first time threshold is varied based on a speed of the vehicle. [2] The method of claim 1, wherein the first time threshold is varied based on the speed of the vehicle by decreasing the first time threshold as the speed of the vehicle increases. [3] A method according to claim 1 or 2, wherein speed thresholds are varied based on the speed of the vehicle by increasing the speed thresholds as the speed of the vehicle increases. [4] A method according to any one of the preceding claims, wherein adjusting the vehicle suspension to increase the damping level comprises: Recalculating the vertical speed each time the damping level is increased or the timer (50) is increased, and Determining whether the newly calculated vertical speed exceeds a third speed threshold or whether the timer (50) exceeds a second time threshold. [5] The method of claim 4, further comprising, in response to the newly calculated vertical speed being less than the third speed threshold and the timer exceeding the second time threshold, adjusting the adjustable damping mechanism to return to the original damping value. [6] The method of claim 4 or 5, wherein the second time threshold is greater than the first time threshold. [7] The method of any one of claims 4 to 6, further comprising, if the newly calculated vertical speed exceeds the third speed threshold and the timer (50) does not exceed the second time threshold, further comprising: Recalculate the vertical speed each time the timer (50) is increased, and Determining whether the newly calculated vertical speed exceeds a fourth speed threshold or whether the timer (50) exceeds a third time threshold. [8] The method of claim 7, further comprising, in response to the newly calculated vertical speed being less than the fourth speed threshold and the timer (50) exceeding the third time threshold, adjusting the adjustable damping mechanism to return to the original damping value. [9] A method according to any one of the preceding claims, wherein sending the adjustment signal to the adjustable damping mechanism comprises sending the adjustment signal to an adjustable damping mechanism of a front wheel (20) of the vehicle and sending an adjustment signal to an adjustable damping mechanism of the rear wheel (20) of the vehicle based on the adjustment signal sent to the adjustable damping mechanism of the front wheel (20). [10] The method of claim 9, wherein sending the adjustment signal to the adjustable damping mechanism of the rear wheel (20) is timed based on a distance between the front wheel (20) and the rear wheel (20). [11] A method according to any one of the preceding claims, wherein the adjustable damping mechanism comprises a variable orifice, and wherein sending the adjustment signal comprises reporting a change in a size of the variable orifice to provide a corresponding change in the damping level for the vehicle suspension. [12] Vehicle suspension system (10), in particular for carrying out a method according to one of the preceding claims, comprising the following: an active damping mechanism operatively coupled to a vehicle wheel (20), and a control device (40) operatively coupled to the active damping mechanism, the control device (40) being configured to: repeatedly calculate a vertical speed of the wheel (20) until the vertical speed exceeds a first speed threshold, to initiate a timer (50) when the vertical speed exceeds the first speed threshold and to repeatedly recalculate the vertical speed of the wheel (20) until the newly calculated vertical speed exceeds a second speed threshold, if the newly calculated vertical speed exceeds the second speed threshold before the timer (50) exceeds a first time threshold, increase the damping level applied to the wheel (20) and vary the first time threshold based on a speed of the vehicle. [13] The vehicle suspension system (10) of claim 12, wherein the controller (40) is configured to vary the first time threshold based on the speed of the vehicle by decreasing the first time threshold as the speed of the vehicle increases. [14] The vehicle suspension system (10) of claim 12 or 13, wherein the controller (40) is configured to vary the speed thresholds based on the speed of the vehicle by increasing the speed thresholds as the speed of the vehicle increases. [15] Vehicle suspension system (10) according to one of claims 12 to 14, wherein the control device is configured to: to recalculate the vertical speed each time the timer (50) is increased, and adjust the active damping mechanism to increase the damping by an incremental amount when the newly calculated vertical speed exceeds a third speed threshold and the timer (50) does not exceed a second time threshold. [16] The vehicle suspension system (10) of claim 15, wherein the control device is configured to: to recalculate the vertical speed each time the timer (50) is increased, and adjust the active damping mechanism to increase damping when the newly calculated vertical speed exceeds a fourth speed threshold and the timer (50) does not exceed a third time threshold. [17] The vehicle suspension system (10) of claim 15 or 16, wherein the controller (40) is further configured to adjust the active damping mechanism to return to the original damping value in response to the recalculated vertical speed being less than the third speed threshold and the timer (50) exceeding the second time threshold. [18] The vehicle suspension system (10) of any one of claims 12 to 17, further comprising one or more sensors (12) measuring a vertical position of the wheel (20), wherein the controller (40) is configured to calculate the vertical velocities by taking time derivatives of respective vertical position measurements from the one or more sensors (12). [19] A vehicle suspension system (10) according to any one of claims 12 to 18, wherein the active damping mechanism comprises a variable orifice (14) and / or a hydraulically actuated cylinder and / or a cylinder actuated by a solenoid and / or an electromagnetically energized proportional valve and / or a magnetorheological fluid.

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