System and method for controlling interaction between a vehicle and a road surface

Abstract

Vehicles traveling on road surfaces may encounter various road surface features and characteristics. Encountering certain road surface features can result in undesirable consequences, including discomfort for occupants, potential damage to vehicle components, and safety concerns. Methods and apparatus are disclosed for detecting and characterizing such features and mitigating their effects using on-board systems. These methods and apparatus also include using information about the interaction of the vehicle's front wheels with features to implement control strategies that mitigate the effects of the vehicle's rear wheels interacting with the same features. Additionally, the present disclosure introduces methods and apparatus for gathering information about certain road surface characteristics, such as friction parameters, and assessing those road surface characteristics.

Description

[Technical Field]

[0001] Related Applications

[0001] This application claims the benefit of priority under 35 U.S.C. §119(e) to U.S. patent application Ser. No. 63 / 417,141, filed Oct. 18, 2022, and U.S. patent application Ser. No. 63 / 456,668, filed Apr. 3, 2023, the disclosures of which are incorporated by reference in their entireties.

[0002] Field FIELD OF THE INVENTION

[0002] The disclosed embodiments relate to controlling the movement of a vehicle as it travels over a road surface. [Background technology]

[0003] background

[0003] Roads designed for vehicle travel may contain multiple discrete features or anomalies, such as potholes, speed bumps, manhole covers, cracks in the road surface, etc., and / or distributed surface characteristics, such as various coefficients of friction and various road surface profiles. When a vehicle interacts with such features or surface characteristics, the vehicle and / or vehicle occupants may be exposed to adverse effects induced by the interaction. For example, undesirable vertical motion may be transmitted to the vehicle body, thereby resulting in a degradation of the experience for the vehicle occupants. In addition, interacting with such features may cause damage to vehicle components or affect vehicle safety (e.g., by flattening a tire, bending or deforming a rim, generally increasing wear on suspension components, etc.). Several vehicle motion control systems exist, such as braking systems, active or semi-active suspension systems, driver assistance systems, etc., that can be proactively controlled before traversing such road features or surfaces to prepare the vehicle accordingly and mitigate one or more of these adverse effects. Summary of the Invention [Means for solving the problem]

[0004] overview In some aspects, techniques described herein relate to operating a vehicle, the operating method including: interacting with a negative road feature with a first wheel of the vehicle during a first interaction; receiving data from at least one sensor mounted on the vehicle during the interaction; determining a characteristic of the negative road feature based on the data; developing a control strategy for a second wheel of the vehicle to minimize an amount of penetration of the second wheel of the vehicle into the negative road feature based on the characteristic; interacting with the negative road feature with the second wheel of the vehicle; and implementing the second wheel control strategy during the second interaction. In some embodiments, the negative road feature may be a pothole, the characteristic of the negative road feature may be a length of the pothole or a depth of the pothole, the second wheel control strategy may include use of an active suspension system, a semi-active suspension system, a steering system, or a braking system, and / or the second wheel control strategy may depend at least in part on a value of a vehicle state parameter (e.g., vehicle speed). In some embodiments, the vehicle may further include a third wheel and a fourth wheel, and the second wheel control strategy may include initiating a deflection vertical wheel force pattern between the four wheels and / or bouncing the second wheel at a predetermined frequency (e.g., at the wheel hop frequency of the second wheel).

[0005] As used herein, when referring to a pair of vehicle wheels that may encounter a particular road feature or travel on effectively the same section of road surface, a "front wheel" or "first wheel" refers to the wheel that encounters the road feature or travels on the section of road surface before the "rear wheel" or "second wheel." For example, in a vehicle with more than four wheels, the first wheel or front wheel may be any leading wheel, and the second wheel or rear wheel refers to any trailing wheel that encounters or interacts with a given road feature or a given section of road surface.

[0006] In some aspects, techniques described herein relate to operating a first vehicle, the method including receiving information regarding a first interaction between wheels of a second vehicle and a negative road feature, determining a characteristic of the negative road feature based on the information, developing a wheel control strategy to minimize an amount of penetration of the wheels of the first vehicle into the negative road feature based on the characteristic, interacting with the negative road feature with the wheels of the first vehicle, and implementing the wheel control strategy during the second interaction. In some embodiments, the first vehicle and the second vehicle may be the same vehicle, the negative road feature may be a pothole, the characteristic of the negative road feature may be a length or depth of the pothole, the second wheel control strategy may include use of an active suspension system, a semi-active suspension system, a steering system, or a braking system, and the second wheel control strategy may depend at least in part on a value of a vehicle state parameter (e.g., vehicle speed). In some embodiments, the first vehicle may include a total of four wheels, and the second wheel control strategy may include initiating a deflection vertical wheel force pattern between the four wheels or bouncing the second wheel at a predetermined frequency (e.g., at a wheel hop frequency).

[0007] In some aspects, techniques described herein relate to operating a first vehicle, the method comprising: driving a first vehicle along a road surface, the road surface including a feature; receiving information about the feature using a controller; determining when a first wheel of the vehicle will reach the feature; and determining a force input profile for reducing a normal force on the first wheel when the first wheel reaches the feature, the first force input profile configured to improve at least occupant comfort, vehicle safety, and / or vehicle drivability. The information about the feature may be collected from sensor signals mounted on the first vehicle during one or more previous runs of the same vehicle, or during previous runs of multiple vehicles. In some embodiments, the information about the vehicle may be received by a controller in the first vehicle from sensors mounted on the first vehicle. For example, a sensor mounted on a first vehicle may receive information about a feature when a first wheel of the first vehicle interacts with the feature, and the information may then be used to mitigate the adverse effects of an interaction between a second wheel of the first vehicle and the same feature.

[0008] In some aspects, techniques described herein relate to operating a first vehicle, the operating method including driving the first vehicle along a first road surface, modifying a normal force on at least a first tire of the first vehicle according to a predetermined pattern, determining, using an on-board sensor, a change in wheel angular velocity of the first wheel as a function of the normal force, comparing the change in wheel angular velocity of the first wheel as a function of the normal load with previously obtained reference data, and determining a value of a parameter based on the comparison. In some embodiments, the parameter may be a coefficient of friction between the first tire and the first road surface. In some embodiments, the reference data may be the change in wheel angular velocity of the second wheel as a function of vertical load, the reference data may be a previously obtained change in wheel angular velocity of the first wheel as a function of vertical load, the normal force may be varied by using an active suspension actuator interposed between the first wheel and the body of the first vehicle, and / or the normal force may be varied at a predetermined frequency (e.g., effectively the wheel hop frequency of the first wheel).

[0009]

[0009] In some aspects, the techniques described herein relate to operating a first vehicle, the operating method including driving the vehicle along a road surface; predicting interactions between wheels of the vehicle and positive features, where the height of the features is greater than the available or desired suspension travel; planning a trajectory that limits the suspension travel to the available or desired suspension travel within the limits of available actuator force while maximizing a comfort level for one or more vehicle occupants; and commanding actuators to move portions of the vehicle, where at least portions of the vehicle are commanded to follow the planned trajectory.

[0010]

[0010] It should be understood that the above-described concepts, and additional concepts described below, may be arranged in any suitable combination, as the disclosure is not limited in this respect. Furthermore, other advantages and novel features of the present disclosure will become apparent from the following detailed description of various non-limiting embodiments when considered in conjunction with the accompanying drawings.

[0011] BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The accompanying drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component shown in various figures may be represented by a similar reference numeral. For purposes of clarity, not every component may be labeled in every drawing. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 shows the main processes and steps by which a vehicle interacts with or traverses a road feature with its front and rear wheels. [Figure 2]

[0013] Figure 2 shows the torsion reduction strategy for the rear wheel. [Figure 3]

[0014] Figure 3 shows a block diagram of the rear wheel preview controller. [Figure 4]

[0015] FIG. 4 shows a possible implementation of the soft saturation algorithm. [Figure 5]

[0016] Figure 5 shows how a wheel encounters a road event. [Figure 6]

[0017] FIG. 6 shows the time traces of wheel acceleration and longitudinal acceleration for a vehicle traversing the event first with its front wheels and then with its rear wheels. [Figure 7]

[0018] Figure 7 shows the schematic layout of the wheels. [Figure 8]

[0019] FIG. 8 shows a typical carpet plot for the longitudinal force on the tire as a function of vertical force and longitudinal slip. [Figure 9]

[0020] FIG. 9 shows the wheel speed difference and road friction for a simulated vehicle while energizing the wheels in a repeating pattern. [Figure 10]

[0021] FIG. 10 shows the calculated relationship of peak-to-peak wheel speed difference to road friction for the simulated vehicle. [Figure 11]

[0022] FIG. 11 shows the relationship between peak-to-peak wheel spin acceleration and road friction for a vehicle with an additional tire load applied in a slow deflection pattern. [Figure 12]

[0023] FIG. 12 shows a schematic diagram of the wheel and suspension about to traverse a positive event. [Figure 13]

[0024] FIG. 13 shows a schematic diagram of the wheels and suspension attempting to traverse a positive event according to a trajectory plan. [Figure 14]

[0025] FIG. 14 shows a schematic diagram of the wheel and suspension during traversing a positive event. [Figure 15]

[0026] FIG. 15 is a schematic diagram of one embodiment of a vehicle including a vehicle control system and vehicle sensors. DETAILED DESCRIPTION OF THE INVENTION

[0013] Detailed Description

[0027] In some embodiments, a cloud-based crowdsourcing system with a database of known road features, communicating with one or more microprocessors onboard the vehicle, may provide information regarding upcoming or anticipated interactions with road features (e.g., potholes, manhole covers, bumps), i.e., road events, to one or more control systems within the vehicle. Alternatively, or in addition, as shown in FIG. 15 , a sensor-based look-ahead system (such as a system based on a camera, LiDAR, RADAR, or similar non-contact look-ahead sensor 223) may be used. However, neither of these systems may be readily available or enabled. Alternatively, or in addition, information from one or more on-board motion sensors 223 a may be utilized in real time as the front wheels (and associated front axle) interact with or traverse a given road feature. Such information may be provided to the vehicle control system regarding upcoming or anticipated events (e.g., the interaction of another part of the vehicle (e.g., the rear wheels) with the same road feature). The vehicle control system may then use one or more actuators to mitigate the impact on the vehicle of the rear wheel or axle's interaction with the road feature. By using such information from on-board motion sensors, in some embodiments and under certain driving conditions, reliance on look-ahead systems may be reduced or eliminated.

[0014]

[0028] To provide these benefits, the following procedures may be implemented. First, a detection method may be utilized to predict vehicle behavior during anticipated interaction of a road feature at the vehicle's rear wheels based on information gathered during the front wheels' interaction with the same road feature. The method may include determining specific characteristics of the feature, such as dimensions and / or shape, based on the information gathered during the front wheels' interaction. Next, an actuation system may be utilized that uses such information. The actuation system may include, but is not limited to, active suspension actuators, active roll actuators, braking actuators, steering actuators, semi-active suspension actuators, or others. Finally, a method may be utilized to command the actuation system to maximize benefits for the vehicle and / or occupants derived at least in part from the a priori information. Such methods may be specific to each particular actuation system and / or each type of feature, or may share common elements.

[0015]

[0029] In some embodiments, there may be discrete steps that occur as the vehicle traverses or interacts with road features. Referring to FIG. 1 , a first step 1A may occur when the front wheel 1 of the vehicle 3 reaches or interacts with a feature 5, e.g., a pothole, in the road surface 7. During Stage 0, in-vehicle detectors, operating continuously or intermittently, may receive and analyze sensor data that may be segmented into buffers of a particular size. Stage 0 may extend beyond and occur simultaneously with Stages 1 and 2. During Stage 0, data may be acquired or received, for example, from motion sensors, such as acceleration, speed, or position sensors, mounted on or near the front axle and / or on the vehicle body, or from other sensors that indicate vehicle motion or the motion of vehicle components, such as, for example, the wheel 1 or portions of the associated unsprung mass. In the embodiment shown in FIG. 1 , in step 1B, a road feature is detected, beginning phase 1, and a vehicle control system (e.g., a central controller, a braking system controller, an active or semi-active suspension controller, a driver assistance system controller, a propulsion system controller, etc.) may be triggered to develop or select a mitigation strategy, for example, in preparation for the rear wheels 9 interacting with or crossing the road feature 5. The mitigation strategy may include controlling actuators and / or changing operating parameters of one or more control systems of the vehicle. For example, in the case of an active suspension system, the mitigation strategy may include activating specific suspension forces or modifying control parameters such as damping coefficients. Due to physical system limitations (e.g., limited actuator bandwidth), the mitigation strategy may require time before it can be fully implemented (at time step 1C). After time step 1C, the control system may be prepared for the rear wheels' interaction with or crossing the road feature 5. At time step 1D, the rear wheels have interacted with or crossed the feature, and the adverse effects from the event have been mitigated.

[0016]

[0030] The duration of Phase 1 may depend on the vehicle control system and determines how much time is available for the detector to categorize and classify the event at the front wheels after detecting that an interaction with a feature has occurred at the front wheels so that mitigation strategies can take effect before the rear wheels reach the event. Without being bound by theory, the duration from time step 1A to time step 1D is the traverse time from the front wheels to the rear wheels, which may be calculated by the following formula:

number

[0017]

[0031] Therefore, the maximum available time for the detector can be given by:

number

[0018]

[0032] where MaxTimeForMitigation may be the maximum time required by the vehicle control system to prepare for crossing a road event. For example, an active suspension system may require approximately 100 ms to achieve the desired force, and the vehicle's wheelbase may be 3 meters long, so it would be:

number

[0019]

[0033] For each vehicle control system and mitigation strategy, there will be a speed at which there may not be enough time for the detector to detect the road feature and implement the mitigation strategy. However, the inventors have recognized that the negative impact of traversing a particular feature, e.g., a pothole, may be less significant at higher speeds where the time available for Stage 1 may be shorter.

[0020]

[0034] MaxAvailTime may determine the maximum length of the buffer used to segment the upcoming data. Buffer length may affect detection performance, as identifying road features within shorter sections of data may be more difficult than within longer ones. Some overlap between consecutive buffers may be advantageous to ensure that vehicle responses while traversing a road feature are fully captured in the data, and not just portions of the response. The appropriate amount of overlap may depend on the type of road feature, as some features may generate longer vehicle responses, and therefore more overlap between segments may be appropriate to ensure that the entire response is captured.

[0021]

[0035] The data contained in each buffer may be processed using a detection algorithm, which may be implemented in a processor onboard the vehicle, or in a second vehicle or another remote processor, e.g., located in the cloud. In some embodiments, conventional approaches for anomaly detection in short time series may be used as the detection algorithm. For example, several statistical measures may be calculated to identify sudden changes in the data. These techniques have several advantages, including low computational cost and sometimes simplicity, but may also have significant limitations. For example, conventional approaches may have several parameters that require separate adjustment for each test case, their detection performance may be moderate, and they may not be easily scalable. Because large libraries of road features may be created, scalability is a desirable attribute or factor for such applications. In some embodiments, each type or category of road feature may require a unique mitigation strategy from the same or a different vehicle control system. Additionally, for a given mitigation strategy, specific categorization of road features based on their characteristics may be required (e.g., classification of potholes based on their length, depth, edge sharpness, width, and / or shape). In some embodiments, machine learning-based approaches may be used for road feature detection because, despite their complexity, they can be highly scalable and modular and can solve categorization problems. Machine learning models may be trained using a representative dataset to perform predictions with high confidence using an unknown dataset. In this context, a positive prediction may correspond to the detection of a road feature, and a negative prediction may correspond to a non-detection. The training process may be performed offline outside the vehicle if sensor data was previously collected and stored in an external storage device, but may also be performed on-board the vehicle if the data can be stored within the vehicle. A compact, trained machine learning model may be deployed and used as input to the data buffer described above. Examples of these models may include, but are not limited to, k-nearest neighbor algorithms, support vector machine algorithms, neural networks, and others.

[0022]

[0036] Detection of upcoming road features can benefit some vehicle control systems. In some embodiments, the mitigation strategies described herein can be applied by an active suspension system to mitigate the effects of a single wheel negative impact event (SWNIE). As used herein, the term "SWNIE" refers to a road feature that is comparable in size to or smaller than the vehicle and that may occur on either side (left or right) of the vehicle at a given time. During a SWNIE, the road surface drops away from the vehicle until it falls back toward the vehicle. Examples of such features may include, but are not limited to, potholes, manhole covers, drainage grates, diagonal ditches, etc. As a vehicle's wheels traverse such a road feature, the wheels may begin to drop into the feature. Prior to a wheel's interaction with a SWNIE, the suspension spring associated with that wheel may be compressed due to the vehicle's mass (e.g., a load equivalent to approximately ¼ of the vehicle's weight (for a four-wheel vehicle) may be stored in each suspension spring, with the weight distributed approximately evenly between the front and rear, and left and right sides of the vehicle). Due to the energy stored in the springs, the wheel's acceleration during its penetration into the SWNIE may be high. The energy stored in the springs may be released when the wheel becomes airborne, causing the wheel to strike the edge of a road feature, causing adverse impacts to the vehicle, e.g., longitudinally and / or vertically. To mitigate the effects of such an event, torsional forces may be applied by an active suspension system at the four wheels. In a four-wheel vehicle, the torsional forces may include the implementation of simultaneous or effectively simultaneous lift and push down commands for each pair of diagonally opposed wheels, respectively. For example, if a left-rear vehicle is expected to interact with a SWNIE, a compressive force may be applied to the left-rear and right-front wheels, while an extension force may be applied to the right-rear and left-front wheels, effectively simultaneously. In this manner, the left-rear wheel may be prevented from falling into the SWNIE or may fall with reduced acceleration. As a result, the impact of the left-rear wheel at the far end of the SWNIE on the vehicle may be reduced or eliminated.

[0023]

[0037] FIG. 2 illustrates a sequence of events that may occur when a vehicle's front wheel 20 interacts with or traverses a pothole 22, along with a corresponding force command 23 that may be issued to an actuator associated with a rear wheel 24 on the same side of the vehicle. In certain embodiments and operating conditions, a torsional force may be applied in response to the front wheel's interaction with the pothole and a detector detecting its presence. However, a delay period may be considered to allow post-shudder motion to dissipate in the front wheel 20 before the torsional force may be applied. The inventors recognized that such a delay may be necessary to avoid extending the period in which the front wheel is vibrating. When a target force command is given, there may be a delay before the actuator reaches full force. After such a mag, mitigation may become effective or fully effective, and the rear wheel may be held or may fall into the pothole with reduced acceleration (depending on the target force level and the actuator's output capability to generate the commanded or desired force). Detectors may also be used to detect rear wheel impacts. When a rear wheel impact is detected, the controller may return the force command to 0 to conserve energy and / or allow the system to prepare to react to the next road feature. This detector may be a relatively simple one, as the impact may be expected within a specific time window after the front wheel interaction.

[0024]

[0038] It should be noted that the information described herein as being collected on the front wheels of the vehicle can also come from external sources, such as, for example, from a preceding vehicle through vehicle-to-vehicle communication, from a preceding vehicle through communication using a cloud server, or from the own vehicle using non-contact predictive sensing that can determine the characteristics of an event.

[0025]

[0039] As used herein, the term "rear preview" refers to a method of using information from the front or leading wheels, or from sensors ahead of the trailing wheels, to periodically, occasionally, or continuously control actuators at the rear or trailing wheels with the goal of improving overall vehicle isolation from road disturbances. At a high level, it may consist, for example, of a real-time road z estimator operating at the front axle or based on sensor information ahead of the axle. The road z estimation may then be used to determine in advance optimal feedforward or open-loop forces for the rear or trailing wheel actuators, for example, by inverting a model of vehicle or wheel dynamic response.

[0026]

[0040] Because it can be calculated using prior knowledge, this force may not have some of the inherent limitations of forces determined by a feedback-only controller. For example, it may be non-causally filtered, allowing control of a desired frequency range with good phase accuracy, whereas a feedback-only force may have undesirable effects due to phase variations introduced by an equivalent real-time filter. In some embodiments, for example, by reducing the effects of rear wheel interaction with road features, overall vehicle heave and pitch and roll motions may be mitigated. Note that non-causal filtering may require some duration of preview knowledge due to filter transient response. At higher speeds, the time between the front and rear wheels interacting with road features may be shorter. As this time becomes shorter, the frequency range in which rear wheel preview can be used to effectively control rear wheel motion may also be reduced.

[0027]

[0041] In some embodiments, and under certain operating conditions, one or more vehicle controllers running on one or more microprocessors may receive information from on-board motion sensors when the front wheels interact with discrete road features. One or more on-board vehicle controllers may use this information to control aspects of various vehicle systems in response to the rear wheels interacting with the same features.

[0028]

[0042] Additionally or alternatively, in some embodiments and under certain operating conditions, one or more vehicle controllers running on one or more microprocessors may estimate one or more characteristics of the road surface ahead of the rear wheels by monitoring aspects of the motion of the front wheels as they interact with the same or effectively the same road surface, as measured by on-board motion sensors. Estimation of road surface characteristics, such as road surface profile, coefficient of friction, road roughness, road texture, etc., as described above, may be performed intermittently, effectively continuously, or continuously, as the disclosure is not limited in this respect.

[0029]

[0043] FIG. 3 is a block diagram of one embodiment of a preview controller 29 that generates force commands in block 41 for at least one actuator (e.g., an active or semi-active suspension actuator) associated with the rear wheels. The preview controller 29 may receive sensor data in block 30 related to front wheel motion induced by the front wheels' interaction with a portion of the road surface and vehicle speed information in block 31. A road estimator in block 32 is configured to estimate values ​​of parameters related to one or more aspects of the portion of the road surface based at least in part on the information from the sensors in block 30. Referring to FIG. 3, the road estimator 32 may use available sensor information 30, e.g., a z-axis sensor, to generate a real-time estimate of the change in position of the road perpendicular to the road surface, i.e., the profile of the road surface beneath each wheel. In some embodiments of the preview controller 29, the sensors may include one or more accelerometers attached to the unsprung mass or damper, a ground clearance sensor, and an accelerometer or IMU attached to the vehicle body. In some embodiments, the change in direction perpendicular to the nominal road surface, i.e., the z estimate, can be the rate of change or absolute position in the direction perpendicular to the nominal road surface.

[0030]

[0044] As used herein, when referring to a road z estimate, it should be understood that this estimate may be a representation of the vertical road profile at least along the path ahead of the wheel, and may describe a vertical profile or its spatial derivative of a function with respect to the actual road profile that captures how the road interacts with the tire and wheel assembly because the tire will envelop some road content features while following others. In some embodiments, this function may represent the path of the tire contact patch or an abstraction of the tire contact patch as a single point contact. In some embodiments, this function may be a road profile received by a non-contact sensor such as a laser, radar, or lidar, and processed using a tire model to capture the tire envelopment of road content. In some embodiments, the function may be accurate within a predetermined time or spatial frequency range, for example, for features longer than the tire contact patch, or for features acquired between 0.5 Hz and 8 Hz in the time domain, or for features within another time or spatial frequency range, as examples.

[0031]

[0045] Some embodiments of preview controller 29 may use an inverse model of at least a portion of the vehicle and its suspension to estimate one or more characteristics of the road surface. Because the estimator may be a real-time estimator, the inverse model may need to be low-pass filtered. Low-pass filtering may introduce phase errors relative to a perfect road estimator. However, such phase errors may be corrected in a later step during acausal filtering.

[0032]

[0046] For rear-wheel preview, one or more parameters of the road for the surface traversed by the two front wheels may be estimated in real time and passed to a time buffer in the next subsystem, block 33. In some embodiments, the time buffer may maintain a rolling buffer of these road surface estimates, e.g., a 1-second buffer. The length of the buffer may be a more important consideration at very low speeds than at higher speeds. For example, a 1-second buffer may be sufficient as long as the time between forward or rearward travel arriving at the same point in the road surface remains 1 second or less. For a typical vehicle with a wheelbase of approximately 3 meters, this may allow effective control up to a vehicle speed of 3 m / s (approximately 7 mph). For control below that speed, the buffer length may be increased.

[0033]

[0047] In the embodiment of FIG. 3, once the road estimate buffer is generated, it may be non-causally filtered in block 34. Non-causal filtering may consist of applying a bandpass filter to the buffer in a forward direction and then in a reverse direction to achieve a reduction in phase change over a single one-way filtering operation. In some embodiments, this may allow the content of the road estimate (and therefore the force command) to be controlled within an appropriate frequency range. In some embodiments of preview controller 29, the useful frequency range may extend from a lower limit of approximately 1-5 Hz, depending on the vehicle speed, to an upper limit of approximately 7-10 Hz, depending on the accuracy of the inverse model. However, a frequency range extending between a different lower limit and / or a different upper limit than those indicated above may be used, as the disclosure is not so limited.

[0034]

[0048] The forward and reverse paths may be split, such that the forward path becomes a regular real-time filter placed immediately after the road estimator. The reverse path may then remain in the location shown in the figure. In some embodiments, this placement may reduce the computational load and avoid the transient response that the forward path would have if applied directly to the buffer.

[0035]

[0049] However, the reverse pass may still have a transient response. In some embodiments, the reverse pass may need to be reapplied each time a new road estimation point is added to the time buffer. It may exhibit the typical transient response expected when applying a filter to the beginning of a signal. This may result in the most recent points in the buffer not representing the ideal non-causally filtered road. The older the points in the buffer, the less the transient response may affect them.

[0036]

[0050] The spread of the transient response may be determined primarily by the lower frequency cutoff of the bandpass filter. Thus, in some embodiments, the transient response may be shortened at the expense of narrowing the frequency range over which rear preview operates. The higher the vehicle speed, the shorter the time delay between the front and rear axles. To keep the filter transient response shorter than this time delay, the low frequency limit of the bandpass filter may be adjusted as a function of speed. However, in some embodiments, above a certain speed (e.g., 45-60 mph), the bandwidth may be so narrow that rear preview may be ineffective.

[0037]

[0051] Also, in some embodiments, a phase correction may be applied to the buffer in block 34 to counteract the phase introduced in the real-time road estimator.

[0038]

[0052] An inverse model (e.g., a transfer function) in block 35 may be used to convert the buffer of filtered road estimates to the force domain. It may, for example, use a model of the rear body and suspension and invert it to determine the force commands that will most effectively isolate the vehicle from the effects of the rear wheels interacting with the road surface. Because this inverse model may be applied to a buffer of preview information rather than processing real-time inputs, it may maintain a perfect, or effectively perfect, phase relationship.

[0039]

[0053] The model itself may be a simplified quarter-car model. In some embodiments, such a model may provide sufficient accuracy up to the wheel hop frequency (typically around 12 Hz). Therefore, the upper frequency of the non-causal bandpass filter may generally be below this value (e.g., 7-10 Hz).

[0040]

[0054] 3 may be rearranged, and blocks may be combined, added, and / or removed, as appropriate, as the disclosure is not so limited. For example, blocks 33, 34, and 35 may be combined into a single linear transform. Such a combined transform may use, for example, methods that apply one or more causal or non-causal filters.

[0041]

[0055] The rear lag estimation in block 36 may continuously estimate the lag between the front and rear wheels. More specifically, given the longitudinal location of the rear wheels, it may calculate how long it has been since the front axle was in that same location. At a near-constant speed, simply dividing the wheelbase by the speed may provide a sufficiently accurate estimate. However, when the vehicle speed is changing speed (i.e., the car is accelerating or decelerating), the estimate may not be sufficiently accurate.

[0042]

[0056] In some embodiments, the velocity may be integrated to calculate a continuously increasing distance value. The distance value may then be added to a rolling 1-second buffer. To determine the rear delay, a search may be performed in the buffer to find a point that is wheelbase less than the vehicle's current distance value. For example, if the vehicle's current distance value is 335.2 meters and the car has a 3-meter wheelbase, a search may be performed in the buffer for 335.2-3=332.2 meters. If that point is found to have occurred 0.35 seconds ago in the buffer, the front-rear delay may be determined to be 0.35 seconds. Traveling at less than 3 m / s may require a buffer longer than 1 second to be able to continue using preview. In interpolation block 37, a delay estimate is then used to select which point in the force command buffer should be used in the current time step.

[0043]

[0057] In some embodiments, a filter 38 may be used to remove spurious measurements that may be received from the motion sensors induced not by road surface, but rather by vehicle-related artifacts, such as wheel imbalance, loose or worn bushings, and engine imbalance. If the effects of such spurious signals are not removed or mitigated, the commanded forces may induce unwanted motion at the rear of the vehicle. For example, wheel imbalance may result in suspension and vehicle motion that is not the result of either the road surface or actuator forces. This anomaly may result in an error in road estimation and, therefore, an error in force command, which may result in poor isolation performance.

[0044]

[0058] The frequency of wheel imbalance-driven anomalies can be a function of how fast the wheels are rotating. The dominant disturbance may occur once per wheel revolution, so if the wheels are rotating 5 times per second, the disturbance will be at 5 Hz. The rotational speed, and therefore the frequency of the disturbance, can vary as a function of vehicle speed, but generally produces components within a very narrow, sharp frequency range based on speed.

[0045]

[0059] In the distance domain, the frequency of the disturbance may be effectively constant, e.g., once per tire circumference. In some embodiments, the imbalance filter may exploit this behavior by, for example, fitting a sine wave to the input at this fixed distance domain frequency. The phase and magnitude of the sine wave may be updated based on the recent input. This fit of the imbalance may then be subtracted from the input to remove its effect.

[0046]

[0060] As a result of the open-loop nature of preview controller 29, applying nonlinear effects can be safer than when using a feedback signal. Therefore, soft saturation can be used in block 39, which effectively limits the preview force below a certain magnitude. For inputs below a certain magnitude (typically around 1000 N), the output can be the same as the input. Then, for inputs above a lower threshold, they can be damped, for example, so that the output can asymptotically approach an upper limit. Figure 4 shows an example implementation of such a relationship between input and output.

[0047]

[0061] In some embodiments and under certain operating conditions, the effects of interaction between a vehicle's rear wheels and discrete road surface features or anomalies (e.g., potholes, speed bumps, manhole covers, cracks, etc.) can be mitigated by pre-loading the rear wheels. This can allow the vehicle to prepare the rear wheels for a potential impact and minimize the fore-aft and / or vertical disturbances created by such an impact. As a vehicle traveling on a road encounters or traverses a feature or object on the road, the wheels may compress or elongate. Due to normal forces acting on the wheels, any road content or feature it traverses can result in forces being applied to the wheels that have horizontal or fore-aft components in addition to a direction perpendicular to the nominal surface of the road. Thus, disturbances can be forces with components either in the direction of travel of the vehicle or opposite to the direction of travel of the vehicle, as well as a component perpendicular to the road.

[0048]

[0062] FIG. 5 shows a schematic diagram of a wheel 50 encountering a sharp, positive road feature 52 on a road surface 54. A vertical force 56 is applied to the wheel 50. This force may include total weight and possible dynamic forces. When the wheel 50 interacts with the road feature 52, a reaction force 58 applied by the road surface 54 and the road feature 52 may have a vertical component that may be equal to the total vertical force, including the vertical force 56 and inertial forces from the motion of the wheel and tire itself. However, the reaction force 52 may also have a horizontal or in-plane component that depends on various characteristics of the road, such as road slope and road geometry; various characteristics of the wheel, such as diameter, shape, and tire and belt properties; suspension characteristics, such as longitudinal force compliance; and the vertical force applied to the tire at any given moment. The longitudinal component of force 58 may be proportional to the vertical force acting on the tire at, or effectively at, the moment of impact with the feature 56.

[0049]

[0063] In some embodiments, a motion condition may be induced in the wheel 50 before the wheel approaches the discrete road feature 52 so that forces induced by the interaction between the wheel 50 and the road feature 52, such as longitudinal forces, normal forces, or resultant forces, are mitigated as they occur, and any resulting adverse effects on the vehicle and vehicle occupants are mitigated.

[0050]

[0064] To establish such a desired motion state, the characteristics and location of the feature may first be identified and / or characterized before the vehicle's wheels interact with the feature. In some embodiments, information about the road surface feature ahead of the vehicle may be based on prior measurements made before the wheels interact with the feature, for example, by using (i) other specialized vehicles equipped with road mapping instruments such as laser road mapping systems, (ii) data about the feature collected during previous trips by one or more vehicles, and / or (iii) look-ahead sensors such as cameras, radar, or LiDAR to identify and characterize the feature. Alternatively, or in addition, data collected during the vehicle's front wheels' interaction with the feature may be used to characterize the feature and establish a desired motion state for the rear wheels before the wheels interact with the feature.

[0051]

[0065] Characteristics of the feature that can be determined can include its magnitude (e.g., height, depth, length, and / or width of the event) and its location (relative to the vehicle, relative to the road surface, and / or in absolute terms). As the feature is approached, a motion plan can be prepared for the wheels of the vehicle approaching the feature. Actuators (e.g., active suspension actuators, roll actuators, air spring actuators, or other means of moving the wheels relative to the vehicle body) can then be used to affect the motion of the wheels prior to interaction with the feature.

[0052]

[0066] In some embodiments, the normal force on a tire may be reduced when the wheel encounters a feature, thus mitigating the shock (e.g., front-to-rear, vertical, total) that may be transmitted to the wheel or vehicle body. This reduction may be achieved through multiple means. In some embodiments, two roll actuators may be used, or four actuators mounted in the corners of a four-wheel vehicle, or at least four actuators mounted on at least four wheels of a vehicle with more than four wheels, or at least two actuators capable of lifting an axle on a vehicle with at least three axles. Using such a set of actuators, unloading of some tires may be achieved at the expense of increasing the load on others while maintaining total support for the vehicle. In some embodiments, this may be achieved by activating one of four active suspension, air spring, or load-leveling actuators mounted at or in close proximity to each corner and attached to one wheel or unsprung mass of the vehicle in a torsional or deflection pattern. For example, adjacent actuators may apply equal and opposite forces to their respective wheels. For example, forces may be applied at the four corners of a four-wheel vehicle, where the left front actuator may apply a positive force, causing the right front to apply an equal negative force, the left rear to apply a negative force, and the right rear to apply a positive force. This may result in the right front and left rear wheels being unloaded (given the rule that positive force increases load on a wheel) while supporting the vehicle by increasing the load on the left front and right rear wheels. In another embodiment, a similar effect may be achieved by operating two roll actuators, each mounted on one axle of a two-axle vehicle, in such a way that one actuator creates a roll moment to the left, while the other creates an equal and opposite roll moment to the right.

[0053]

[0067] Alternatively, instead of applying a torsional pattern of force, in some embodiments, the unloading of a wheel about to interact with a feature can be achieved dynamically. The wheel in question can be accelerated to change its inertial force and the direction of that force. The inventors recognized that a tire typically behaves as a lightly damped spring in the vertical direction, and therefore, in combination with the mass moving with the wheel (often referred to as the "unsprung mass"), forms a lightly damped resonant second-order system. An actuator can be used to repeatedly apply forces in an appropriate pattern to excite the resonance of the unsprung mass on the tire, thus producing larger motion with the amplification provided by the resonant behavior of the dynamic system, thus inducing a properly timed unloading of the wheel.

[0054]

[0068] FIG. 6 shows time traces of the vertical acceleration of a vehicle's front wheels in top plot 59a, the vertical acceleration of the same vehicle's rear wheels in middle plot 59b, and the longitudinal acceleration of the vehicle's chassis in bottom plot 59c. At time 60, the front wheels traverse a feature, and at time 62, the rear wheels traverse the same feature. During time period 64, a front actuator can be used to energize the front wheels in a repeating pattern timed to match the resonant frequency of the front unsprung mass on the front tires and so that at time 60 the wheels are at their minimum acceleration (and therefore at their maximum height relative to the road surface, and most unloaded). Similarly, during time period 66, the rear wheels on the same vehicle can be energized by an actuator that produces a force in a pattern timed to excite the resonance of the rear unsprung mass on the rear tires and so that at time 62 the wheels are at their minimum acceleration and therefore at their maximum height relative to the road surface, and so unload the rear wheels as they traverse the event at 62. As can be observed from the highlighted area 68 in plot 59c, the longitudinal acceleration resulting from interaction with the features at 60 and 62 in time as measured on the vehicle chassis (in this case near the driver's seat rail attachment point) is significantly reduced through this method.

[0055]

[0069] It should be noted that while this example shows the wheels being energized in a repeating pattern, other tire unloading patterns may also be used as the disclosure is not so limited. Wheel unloading may be done in a single step or may be done using a pattern that is slower than the resonant frequency of the unsprung mass and tire, which may reduce power consumption, noise and vibration, or occupant discomfort.

[0056]

[0070] It is important to note that the different methods described above can be used to mitigate interaction with different types of features or in combination with other mitigation strategies, such as torsional mitigation strategies. Unloading the wheels in a torsional pattern allows for longer periods of unloading and therefore may be suitable for larger features or conditions where the relative locations of features are not known with sufficient accuracy. As described above, mitigating the impact of interaction between wheels and road features by using tire vibration unloading may require more precise information about the location of one or more features, but may be activated simultaneously on both sides of the vehicle and may be suitable for symmetrical events such as railroad crossings, expansion joints, bumps, and other similar features.

[0057]

[0071] The inventors recognized that changing the wheel loading can also change the dynamics of the interaction between the tire and the road surface. This behavior can be used to estimate road friction or tire grip. Under normal operation, a tire may be compressed by normal forces applied to it (due to the weight and dynamic motion of the vehicle and wheel), so it exhibits some reluctance to roll. This reluctance can be referred to as "rolling resistance" and can cause drag on the wheel. Tires can be driven or slowed by driving or braking torques applied by the propulsion system or brakes, respectively. Tires can also be pulled by non-driven wheels (e.g., rear wheels on a front-wheel drive vehicle) or by forces on other parts of the vehicle, such as those experienced when the vehicle is coasting or rolling down a hill.

[0058]

[0072] FIG. 7 shows a schematic diagram of a wheel 70 moving along a road surface 72. A force 74 is applied to the wheel hub, for example, as a reaction to a driving torque, or due to a pull exerted by another wheel, and / or due to gravity acting on the vehicle. A reaction force 76 acting on the ground may be equal and opposite to 74. The tire 70 may support a load or vertical force 78. The ground reaction force 76 may be generated through friction, and the tire's interaction with the road surface may be characterized by a small amount of slippage, commonly referred to as longitudinal slip ratio. The slip ratio is a function of the load on the tire and the longitudinal force exerted. FIG. 8 shows a typical relationship for a tire, often represented as a carpet plot to illustrate the relationship between longitudinal force, vertical force, and slip.

[0059]

[0073] From this plot, it can be determined that for any given vertical force (resulting, for example, from the weight of the vehicle, any dynamic forces acting on the vehicle, and / or any additional actuator forces) and any given longitudinal force (which may be determined by the traction the vehicle has at any given moment, including traction or resistance from other wheels, gravity, and other forces pulling the vehicle in the longitudinal direction), there is a given slip ratio that the tire will experience, which in turn is correlated to the friction between the tire and the surface it is riding on.

[0060]

[0074] In some embodiments, and under certain conditions, surface friction can be estimated when the vertical load for each tire can be varied in a predetermined pattern. Figure 9 shows a repetitive input pattern 90 applied to one wheel. In some embodiments, it may be advantageous to apply this force pattern at or near the resonant frequency of the unsprung mass on the tire to reduce the effort involved in generating the load change and therefore achieve a similar load change at a lower actuator force, or a higher load change at the same actuator force. However, it should be noted that other input frequency patterns may also be used, and the present disclosure is not limited to excitation at the resonant frequency of the unsprung mass. Curve 90 illustrates the wheel speed difference between the right and left wheels of a vehicle on the same axle, where the wheels may be loaded and unloaded in opposite patterns to intensify the measured difference and improve the resolution of the method. It should be understood that the method may also be applied to a single wheel, and the speed difference may be compared to a reference pattern, to an unenergized wheel, or to an average of all four wheels. On the same plot, referring to the right axis, curve 92 shows the simulated surface friction for this simulation run. For simplicity, the surface friction for the simulation is specified to gradually decrease in regular increments from a value of 1 to near 0, thus allowing a single simulation run to represent the entire curve. The curve suggests that on roads with higher surface friction, the tires will have more grip and less front-to-rear slip, and therefore the difference in wheel speed between the right and left sides of the vehicle will be greater.

[0061]

[0075] Figure 10 illustrates this relationship by comparing surface friction to the measured difference in wheel speed between the left and right sides of the vehicle. The curves show a clear correlation between the two values, thus enabling an algorithm to derive an unknown surface friction value based on wheel speed while the wheels are biased in a predetermined manner.

[0062]

[0076] In another embodiment, a slowly varying force may be applied to all four wheels in a four-wheel vehicle with the deflection pattern as described above. In this case, changes in surface friction may be more easily identified than changes in wheel speed and may therefore produce changes in wheel spin acceleration that can be used to estimate surface friction. Figure 11 shows the relationship between measured wheel spin acceleration and surface friction. This method may be preferred in scenarios where the actuators cannot create a rapidly varying force pattern or where rapid changes in tire load are undesirable for comfort or safety reasons.

[0063]

[0077] In alternative embodiments, or under different operating conditions, other vehicle sensors may be used to detect changes when a torsional force is applied. For example, changes in yaw rate related to surface friction and / or tire grip may be detected, where the changes cannot be attributed to either the driver or the vehicle controller. Alternatively, if there is a correction by a lane-keeping assist function, or by an operator, or by the steering system in response to changes in steering torque at the wheels due to changes in friction, then this signal may also be used as a metric to estimate surface friction. Thus, when an actuator force is applied in a deflection pattern, the resulting response by the steering system, the operator, or the driver assistance function may be measured, and surface friction may be estimated based on the measurement.

[0064]

[0078] 12 shows a schematic diagram of a vehicle approaching a positive road feature 120, such as a speed bump. A positive road feature, as used herein, refers to a road feature that substantially protrudes toward the vehicle or has a portion that protrudes toward the vehicle. Positive road features may include, but are not limited to, raised bumps, speed bumps, railroad crossings, steps, curbs, road plates, and frost heaves. A negative road feature, as used herein, refers to a feature that substantially drops away from the vehicle. Such features may include, but are not limited to, potholes, drop-offs, depressions, sinkholes, and storm drain covers.

[0065]

[0079] FIG. 12 shows a vehicle having a body 122, a suspension system 124, and wheels and tires 126 approaching a feature 120. While the vehicle is depicted as having a single wheel, it may include multiple wheels. As the wheel approaches the road feature 120 or other obstacle, it may be subjected to multiple forces. In some embodiments, and under certain conditions, the wheels and tires 126 may support the weight and dynamic load of the vehicle. The road surface may apply a reaction force to the tire at an angle that correlates with the slope of the road. If the road is ascending (i.e., when the slope of the road has a component that is opposite the direction of vehicle motion relative to the vehicle's vertical axis), the reaction force on the wheels and tires may push the vehicle backward; if the road is descending (i.e., when the slope of the road is aligned with and has a component in the same direction as the vehicle's direction of motion), the reaction force on the wheels and tires may push the vehicle forward.

[0066]

[0080] Suspension systems can be used to reduce vehicle body motion and increase comfort for occupants. To accomplish this, the suspension can change length when traversing a road obstacle. For example, the suspension can compress when traversing a positive feature to absorb at least a portion of the vehicle body motion that would otherwise be induced by the feature. However, suspension systems have a limited range of travel. There are limits to the degree to which a suspension system can be compressed or extended. The suspension system shown in FIG. 12 has a maximum available compression travel 128 and a maximum extension travel 130.

[0067]

[0081] When traversing a feature having height 132, for example, if height 132 is less than maximum available compression travel 128, the suspension may be able to absorb all or effectively all of the effect of the feature. However, if feature height 132 is greater than available compression travel 128, then the vehicle may not be able to fully absorb the event without exceeding its travel limits. This may induce a significant increase in normal force on the tires. This increase may be perceived by the occupants as a significant disturbance and may be undesirable.

[0068]

[0082] 13 shows how a suspension system can be tuned to anticipate interaction with a feature 140 having a maximum height 142 that exceeds the suspension's maximum available compression travel 144 but not the maximum total travel 146. A trajectory 148 can be planned for the vehicle that will raise the vehicle to a maximum trajectory height of 150. In some embodiments, and under certain operating conditions, if the feature height 142 is greater than the available compression travel 144 but less than the total available travel 146, the maximum trajectory height of 150 can be equal to 0.

[0069]

[0083] In some embodiments, under certain operating conditions, the suspension system may be configured to follow a planned trajectory and may be able to achieve this trajectory without substantially deviating therefrom, and then, as shown in FIG. 14, at the maximum height above the event, the body 152 may be at or near that trajectory height above its original position, while the wheels 154 follow the road and the suspension 144 is compressed by an amount not exceeding its maximum available compression travel.

[0070]

[0084] This can be achieved by reducing the amount of change in tire force while the wheel traverses a road feature. Tire force is given by the portion of the vehicle's weight resting on a particular wheel, plus the sum of the reaction forces due to wheel and body acceleration. Under the simplifying assumption that the wheel follows the road event, the only remaining variable is the body acceleration. Body acceleration relative to the vertical direction can increase the force to which the tire is exposed, while preemptively and gradually accelerating the body prior to interaction with the feature can reduce any change in tire force as a result of the interaction. Therefore, the optimal solution for trajectory 148 can be determined by minimizing the acceleration on the body, subject to the constraints posed by the maximum available suspension travel, maximum available compression travel, and road event height, as described above.

[0071]

[0085] Planning a trajectory such as that described above may require prior knowledge of the upcoming road, which may be based on local sensors or from other sources of prior knowledge. It may require that the suspension actuators be able to change the position of the vehicle body relative to the ground within a suitable time frame to effectively respond to the interaction of road features. The suitable time frame may depend on the road shape and vehicle speed. On generally flat roads with a single positive event, a slow actuator with sufficient warning may be able to raise the vehicle for a long period of time and still prepare for the event. However, most roads have more than a single event, and the actuator may need to change the trajectory after one event and prepare for the next. On most roads, it may be preferable to be able to move the vehicle within one second to perform this function, although slower or faster actuators may still benefit from the method, as the disclosure is not limited in this respect.

[0072]

[0086] In the above description, it should be understood that available travel may be less than the travel that the suspension can sustain without reaching hard (physical) or soft limits or exceeding its design specifications. The available travel limit may be adjustable or set by a designer or controller depending on operating conditions. It may be set to achieve a desired comfort, safety, or drivability goal, or to match the maximum desired force output from the actuator.

[0073]

[0087] In another aspect of the invention, a vehicle may encounter a negative feature on only one side, and the vehicle may be alerted to the presence of such a feature by one of the methods described above, for example, based on data collected during a previous trip, data from a different vehicle or fleet of vehicles, data from a characterized road segment, data transmitted from the cloud, data stored on the vehicle, or any other such method.

[0074]

[0088] As the vehicle approaches the feature, the vehicle's current location relative to the feature, the feature's location, and / or the current vehicle speed can be used to calculate the expected time to encounter the event. This calculation can be performed on the vehicle before the vehicle approaches the feature, or offline in the cloud. If the vehicle changes speed during the time period between when the calculation is made and when the vehicle encounters the feature, the expected time can be recalculated and, if appropriate, the new expected time can be used.

[0075]

[0089] The inventors have recognized that the discomfort to occupants and the potential for damage to vehicle components resulting from encountering a negative event in the road, such as a pothole, is correlated with the amount of normal force exerted on the tire encountering the feature. This is a result of the wheel and tire having to conform to the road contours due to the normal force acting on the tire. This force may consist of the portion of the vehicle's weight supported by a particular tire, along with any changes caused by dynamic loading of the wheel or body.

[0076]

[0090] In some embodiments, and under certain operating conditions, an active suspension or active roll system may be used to reduce the normal force on the tire that is expected to experience a negative event. This may be achieved by suspension actuators applying forces in a twisting or deflection pattern that increases the force on two opposing tires while increasing the normal force on the other two, one of which may interact with the negative feature.

[0077]

[0091] In some embodiments, three factors may be considered when calculating the time at which the force should be applied. First, the actuation system may have a response time that requires the force command to be applied sufficiently in advance to achieve the desired force level at the appropriate time. Second, there may be limitations in the accuracy of either the estimated vehicle location or the estimated feature location. In this case, it may be desirable to apply the force command in advance to compensate for possible errors. Third, rapid force application may adversely affect the comfort or NVH (noise, vibration, and harshness) perceived by the occupants; therefore, the force may need to be applied more gradually. Taking into account whatever of these is appropriate for a given situation and the actuator to be used, along with other possible timing considerations related to processing speed, processor update rate, or the like, the appropriate timing for the force command to the actuator system may be determined to achieve the desired wheel load relief at the moment the vehicle encounters the feature.

[0078]

[0092] It is also important to consider the fact that when encountering a feature on one side of the vehicle, the feature will first be encountered by the front wheels on one side of the vehicle, and may be encountered shortly thereafter by the rear wheels on the same side of the vehicle. For many road vehicles, the front and rear wheels follow similar paths during most normal driving, except during low-speed parking maneuvers or situations where the vehicle skids sideways (having a large sideslip angle). Most road vehicles also have similar front and rear wheel tracks. That is, the front and rear wheels of a vehicle may have the same lateral spacing relative to the vehicle chassis and therefore may follow the same path on the road surface. For vehicles or driving situations where either the front and rear wheels do not follow the same path, application of the event mitigation strategies described herein may be performed independently for the front and rear. However, in the case of a vehicle in which the front and rear wheels follow substantially or effectively the same path, for example, to within a lateral offset of less than 1 cm, or less than 5 cm, or less than 10 cm, the timing between the front and rear events may be noted. This time will decrease with increasing vehicle speed and is related to the vehicle's wheelbase (the distance between the front and rear wheels along the vehicle's direction of travel). Using similar considerations as described above for the front wheels, the optimal time for application of force to the rear wheels may be determined, for example, by taking into account the particular actuation system used on the rear wheels that are about to experience an event, the delays inherent in such actuation, the NVH and comfort impact of rapid force application, and / or other considerations.

[0079]

[0093] In certain embodiments, and under certain operating conditions, a torsional force strategy may be implemented by unloading the front wheels and loading the rear wheels on the same side of the vehicle. After the front wheels interact with the road surface, the front wheels may be loaded while the rear wheels are unloaded. Thus, a torsional strategy may be effective at a given speed if there is sufficient time to accomplish this transition.

[0080]

[0094] A behavior planning control method is advantageous in considering the mitigation strategy to apply for a given event, driving scenario, speed, user settings, and optionally taking into account other vehicle conditions or user preferences. This behavior planning control method can receive information about the type, characteristics, and location of an upcoming event, calculate the optimal timing for wheel load removal commands, determine the optimal strategy given those timing requirements, and then communicate this decision to downstream control methods that calculate and apply optimal force commands to achieve the desired effect. The decisions made by the behavior planning control method can optionally include deciding to apply torsional forces, deciding to apply other load removal methods, or deciding to apply no mitigation strategy, or a subset or combination thereof, or it can include determining the amount of mitigation to apply in each case.

[0081]

[0095] FIG. 15 illustrates a vehicle 210. The vehicle includes a body 212 that supports various components of the vehicle. As shown in FIG. 15, the vehicle includes a microprocessor system 214 having one or more microprocessors that can communicate with various subsystems via a communication channel 216. It is noted that while FIG. 15 illustrates the microprocessor system 214 as a single unit, it may include multiple microprocessors located in multiple locations within the vehicle, as the disclosure is not limited in this respect. As shown in FIG. 15, the vehicle may include an active suspension system having active suspension actuators 218 operably interposed between the vehicle's wheels 220 (or unsprung mass, wheel assemblies) and the body 212 (e.g., sprung mass). Specifically, an active suspension actuator 218 is operably interposed between each wheel of the vehicle and the body 212, such that separate actuators of the active suspension can independently control the vertical movement of each wheel of the vehicle. Each actuator 218 may be configured to apply a force between the wheel 220 and the body 212. The actuators 218 may affect the motion response of the vehicle body 212, and in particular, one or more vehicle dynamics characteristics. The vehicle may also include a braking system having brakes 222. The braking system may include independent brakes coupled to each of the vehicle's wheels 220, such that braking force may be applied to each wheel independently. According to the embodiment shown in FIG. 15, the vehicle may also include forward-looking sensors 223 and / or other motion sensors 223a (e.g., inertial motion sensors (IMUs), displacement sensors, accelerometers, etc.). The forward-looking sensors may include, for example, one or more cameras, LIDAR, radar, combinations thereof, and may be configured to sense forward-looking road information that may be utilized by one or more vehicle planners or controllers, which may be located within the microprocessor system 214.Alternatively, or in addition, previously collected (e.g., crowd-sourced) forward-looking road information may be received from one or more local (i.e., on-board) or remote databases at one or more microprocessors in microprocessor system 214. Motion sensor 223a may be used to provide information regarding the motion of various parts of the vehicle (e.g., body, wheel assembly, active suspension actuators) to one or more microprocessors in microprocessor system 214.

[0082]

[0096] 15 embodiment, the vehicle may also include a steering system 224, which, in the case of a driving vehicle, includes a steering wheel 224a. The steering wheel 224a may form part of a user interface for the vehicle 210. The user interface may be used to provide user input for controlling various portions of the vehicle or to provide feedback, e.g., haptic feedback, to the user. In some embodiments, the steering system 224 may include a rear steering system configured to control one or more rear wheels of the vehicle. Other user interfaces may also be used, as the disclosure is not limited in this respect.

[0083]

[0097] As shown in Figure 15, a vehicle may be traversing a road 226. As shown in Figure 15, a road may include a plane of road surface 228. As used herein, the term "vehicle body" refers to the sprung mass of a vehicle regardless of the type of body structure, including, but not limited to, a unitary, unibody, or monocoque body structure, a body including a separately formed vehicle chassis attached to other portions of the body, and / or any other type of body structure that functions as a sprung mass supported by the suspension system of the vehicle.

[0084]

[0098] While the present teachings have been described in conjunction with various embodiments and examples, it is not intended that the present teachings be limited to such embodiments or examples. On the contrary, the present teachings encompass various alternatives, modifications, and equivalents, as will be appreciated by those skilled in the art. Accordingly, the foregoing description and drawings are by way of example only.

[0085]

[0099] The above-described embodiments of the techniques described herein may be implemented in any of numerous ways. For example, embodiments may be implemented using hardware, software, or a combination thereof. When implemented in software, the software code may be executed on any suitable processor or collection of processors, whether provided in a single computing device or distributed among multiple computing devices. Such processors may be implemented as integrated circuits with one or more processors within integrated circuit components, including commercially available integrated circuit components known in the art by names such as CPU chips, GPU chips, microprocessors, microcontrollers, or coprocessors. Alternatively, the processor may be implemented in the form of custom circuitry, such as an ASIC, or semi-custom circuitry resulting from constructing a programmable logic device. As a still further alternative, the processor may be part of a larger circuit or semiconductor device, whether commercially available, semi-custom, or custom. As a specific example, some commercially available microprocessors have multiple cores, whereby one or a subset of those cores may constitute a processor. However, the processor may be implemented using circuitry in any suitable format. It should also be understood that any reference to a controller in this disclosure is understood to refer to the use of one or more processors configured to perform one or more of the methods disclosed herein.

[0086]

[0100] Further, it should be understood that a computing device including one or more processors may be embodied in any of a number of forms, such as a rack-mounted computer, a desktop computer, a laptop computer, or a tablet computer. In addition, a computing device may be incorporated within devices not generally considered computing devices but having suitable processing capabilities, including a personal digital assistant (PDA), a smartphone, a tablet, or any other suitable portable or fixed electronic device.

[0087]

[0101] A computing device may also have one or more input and output devices. These devices may be used, among other things, to present a user interface. Examples of output devices that may be used to provide a user interface include a display screen for visual presentation of output and a speaker or other sound-generating device for audible presentation of output. Examples of input devices that may be used for a user interface include keyboards, individual buttons, and pointing devices such as mice, touchpads, and digitizing tablets. As another example, a computing device may receive input information through voice recognition or in other audible formats.

[0088]

[0102] Such computing devices may be interconnected by one or more networks of any suitable form, such as a local area network or a wide area network, such as an enterprise network or the Internet. Such networks may be based on any suitable technology, operate according to any suitable protocol, and may include wireless, wired, or fiber optic networks. Additionally, the various methods or processes outlined herein may be coded as software executable on one or more processors utilizing any of a variety of operating systems or platforms. These methods may be embodied as processor-executable instructions stored on associated non-transitory computer-readable media that, when executed by one or more processors, perform any of the methods disclosed herein. Additionally, such software may be written using any of a number of suitable programming languages ​​and / or programming or scripting tools, and may be compiled as executable machine language code or intermediate code that runs on a framework or virtual machine.

[0089]

[0103] In this regard, the embodiments described herein may be embodied as a computer-readable storage medium (or multiple computer-readable media) (e.g., computer memory, one or more floppy disks, compact discs (CDs), optical disks, digital video disks (DVDs), magnetic tape, flash memory, RAM, ROM, EEPROM, circuitry in a field programmable gate array or other semiconductor device, or other tangible computer storage medium) encoded with one or more programs that, when executed on one or more computers or other processors, perform methods for implementing the various embodiments described above. As is evident from the above examples, a computer-readable storage medium may retain information for a sufficient time to provide computer-executable instructions in a non-transitory form. Such computer-readable storage medium or media may be portable, such that the program or programs stored thereon can be loaded into one or more different computing devices or other processors to implement various aspects of the present disclosure as described above. As used herein, the term "computer-readable storage medium" encompasses only non-transitory computer-readable media, which may be considered an article of manufacture (i.e., an article of manufacture) or a machine. Alternatively, or in addition, the present disclosure may be embodied as a computer-readable medium other than a computer-readable storage medium, such as a propagating signal.

[0090]

[0104] The terms "program" or "software" are used generically herein to refer to any type of computer code or set of computer-executable instructions that can be used to program a computing device or other processor to implement various aspects of the present disclosure as described above. Additionally, in accordance with one aspect of the present embodiments, it should be understood that one or more computer programs that, when executed, perform the methods of the present disclosure need not reside on a single computing device or processor, but may be distributed in a modular manner among a number of different computers or processors to implement various aspects of the present disclosure.

[0091]

[0105] Computer-executable instructions may be in many forms, such as program modules, executed by one or more computers or other devices. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types. Typically, the functionality of the program modules may be combined or distributed as desired in various embodiments.

[0092]

[0106] The embodiments described herein may be embodied as methods, of which only one example is provided. The acts performed as part of the method may be ordered in any suitable manner. Thus, embodiments may be constructed in which the acts are performed in an order different from that illustrated. This may include performing some acts simultaneously, even if shown as sequential acts in the illustrated embodiment.

[0093]

[0107] Additionally, some actions are described as being taken by a "user." It should be understood that a "user" need not be a single individual, and that in some embodiments, actions attributed to a "user" may be performed by a team of individuals and / or an individual in combination with computer-assisted tools or other mechanisms.

[0094]

[0108] While the present teachings have been described in conjunction with various embodiments and examples, it is not intended that the present teachings be limited to such embodiments or examples. On the contrary, the present teachings encompass various alternatives, modifications, and equivalents, as will be appreciated by those skilled in the art. Accordingly, the foregoing description and drawings are by way of example only.

Claims

1. 1. A method of operating a vehicle, the method comprising: interacting with a negative road feature with a first wheel of the vehicle during a first interaction; receiving data from at least one sensor onboard the vehicle during the first interaction; determining a characteristic of the negative road feature based on the data; and developing a second wheel control strategy based on the characteristic to minimize an amount of penetration of a second wheel of the vehicle into the negative road feature; interacting with the negative road feature with the second wheel of the vehicle during a second interaction; implementing the second wheel control strategy during the second interaction; A method comprising:

2. The method of claim 1 , wherein the negative road features are potholes.

3. 3. The method of claim 1 or 2, wherein the characteristics of the negative road features are selected from the group consisting of the length of the pothole and the depth of the pothole, the sharpness of the edges of the pothole, and the width of the pothole.

4. The method of any one of claims 1 to 3, wherein the second wheel control strategy comprises the use of a system selected from the group consisting of an active suspension system, a semi-active suspension system, a steering system, and a braking system.

5. The method of any one of claims 1 to 4, wherein the second wheel control strategy depends at least in part on the value of the vehicle state parameter.

6. The method of claim 5 , wherein the state parameter is the speed of the vehicle.

7. 7. The method of claim 1, wherein the vehicle further includes a third wheel and a fourth wheel, and the second wheel control strategy includes initiating a deflection vertical wheel force pattern between the four wheels.

8. The method of any one of claims 1 to 7, wherein the second wheel control strategy comprises bouncing the second wheel at a predetermined frequency.

9. 9. The method of claim 8, wherein the predetermined frequency is the wheel hop frequency of the second wheel.

10. The method according to any one of claims 1 to 9, wherein the first wheel and the second wheel are the front and rear wheels, respectively, of the vehicle.

11. 1. A method of operating a first vehicle, the method comprising: receiving information from a second vehicle regarding a first interaction between wheels of the second vehicle traveling in front of the first vehicle and a negative road feature; determining a characteristic of the negative road feature based on the information; and developing a wheel control strategy based on the characteristics to minimize an amount of penetration of the wheels of the first vehicle into the negative road feature; interacting with the negative road feature with the wheels of the first vehicle during a second interaction; implementing the wheel control strategy during the second interaction; and A method comprising:

12. 12. The method of claim 11, wherein the first vehicle and the second vehicle are traveling at a first speed and a second speed, respectively, and the difference between the first speed and the second speed is less than 10 miles per hour.

13. The method of claim 11 or 12, wherein the negative road features are potholes.

14. 14. The method according to any one of claims 11 to 13, wherein the characteristics of the negative road features are selected from the group consisting of: the length of the pothole, the depth of the pothole, the sharpness of the edges of the pothole, and the width of the pothole.

15. The method of any one of claims 11 to 14, wherein the wheel control strategy comprises the use of a system selected from the group consisting of an active suspension system, a semi-active suspension system, a steering system, and a braking system.

16. The method of any one of claims 11 to 15, wherein the control strategy depends at least in part on values ​​of state parameters of the vehicle.

17. The method of claim 16 , wherein the state parameter is the speed of the vehicle.

18. 18. The method of any one of claims 11 to 17, wherein the first vehicle includes a total of four wheels, and the control strategy includes initiating a deflection vertical wheel force pattern between the four wheels.

19. The control strategy includes bouncing the wheels of the first vehicle at a predetermined frequency.

20. 20. The method of claim 19, wherein the predetermined frequency is the wheel hop frequency of the second wheel.

21. 1. A method of operating a vehicle, the method comprising: traveling by the vehicle along a road surface, the road surface including features; receiving, at a controller, information regarding the characteristics; determining when a first wheel of the vehicle will reach the feature; determining a force input profile for reducing a normal force on the first wheel when the first wheel reaches the feature, the first force input profile being configured to improve at least one metric selected from the group consisting of occupant comfort, vehicle safety, and vehicle drivability; A method comprising:

22. 22. The method of claim 21, wherein the information about the characteristics was collected from sensor signals onboard the first vehicle during one or more previous runs of the same vehicle, during previous runs of multiple vehicles.

23. 1. A method for determining a value of a parameter related to friction between a tire of a first wheel of a first vehicle and a first road surface, the method comprising: traveling along the first road surface with the first vehicle; Varying a normal force on at least the first tire of the first vehicle according to a predetermined pattern; determining a change in wheel angular velocity of the first wheel as a function of the normal force using an on-board sensor; comparing the change in wheel angular velocity of the first wheel as a function of the normal load with previously acquired reference data; determining the value of the parameter based on the comparison; and A method comprising:

24. 24. The method of claim 23, wherein the parameter is a coefficient of friction between the first tire and the first road surface.

25. 25. The method according to claim 23 or 24, wherein the reference data is the change in wheel angular velocity of the second wheel as a function of vertical load.

26. A method according to any one of claims 23 to 25, wherein said reference data is a previously obtained variation of the wheel angular velocity of said first wheel as a function of vertical load.

27. 27. The method of any one of claims 23 to 26, wherein the normal force is modified by using an active suspension actuator interposed between the first wheel and the body of the first vehicle.

28. A method according to any one of claims 23 to 27, wherein the normal force is varied at a predetermined frequency.

29. 29. The method of claim 28, wherein the frequency is effectively a wheel hop frequency of the first wheel.

30. 1. A method of operating a vehicle, the method comprising: driving the vehicle along a road surface; predicting an interaction between the vehicle's wheels and a positive feature, the higher the height of the feature, the greater the available suspension travel; and planning a trajectory that limits suspension travel to within the limits of available actuator force while maximizing a comfort level for one or more vehicle occupants; commanding actuators to move portions of the vehicle, wherein at least the portions of the vehicle effectively follow the planned trajectory; A method comprising:

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