System and method for controlling interaction between vehicle and road surface

Abstract

A vehicle traveling on a road surface may encounter various road surface features and characteristics. Encountering certain road features may result in undesirable results, including occupant discomfort, potential damage to vehicle components, and safety issues. Methods and apparatus for detecting and characterizing such features and using in-vehicle systems to mitigate their effects are disclosed. These methods and apparatus also include implementing a control strategy using information about the interaction of the front wheels with the feature that mitigates the effects of the interaction of the rear wheels of the vehicle with the feature. In addition, the present disclosure introduces methods and apparatus for collecting information about certain road surface characteristics, such as friction parameters, and evaluating these road surface characteristics.

Description

[0001] Cross - reference to related applications

[0002] This application claims the benefit of priority of U.S. Application Serial No. 63 / 417,141, filed on October 18, 2022, and U.S. Application Serial No. 63 / 456,668, filed on April 3, 2023, under 35 U.S.C.§119(e). The disclosures of the above two U.S. applications are hereby incorporated by reference in their entireties. Technical field

[0003] The disclosed embodiments relate to the motion control of a vehicle when the vehicle is traveling on a road surface. Background art

[0004] Roads designed for vehicle travel can, for example, include multiple discrete features or anomalies such as potholes, speed bumps, manhole covers, road surface cracks, etc. and / or distributed surface characteristics such as various friction coefficients and various road surface profiles. When a vehicle interacts with such features or surface characteristics, the vehicle and / or the vehicle's occupants may suffer adverse effects caused by the interaction. For example, unwanted vertical motion may be transmitted to the vehicle body, resulting in a degraded experience for the vehicle occupants. Additionally, interacting with such features may (e.g., due to flat tires, bent or deformed rims, generally increased wear of suspension components, etc.) cause damage to vehicle components or affect vehicle safety. There are several vehicle motion control systems, such as braking systems, active or semi - active suspension systems, driver assistance systems, etc., which can be proactively controlled before traversing such road features or road surfaces to accordingly prepare the vehicle and mitigate one or more of these adverse effects. Summary of the invention

[0005] In some aspects, the techniques described herein relate to operating a vehicle, including: during a first interaction, causing a first wheel of the vehicle to interact with a negative road feature; during the interaction, receiving data from at least one sensor on-board the vehicle; based on the data, determining a characteristic of the negative road feature; based on the characteristic, developing a control strategy for a second wheel to minimize the amount by which the second wheel of the vehicle sinks into the negative road feature; causing the second wheel of the vehicle to interact with the negative road feature; and during a second interaction, implementing the control strategy for the second wheel. In some embodiments, the negative road feature can be a pothole, the characteristic of the negative road feature can be the length or depth of the pothole, the control strategy for the second wheel can include using an active suspension system, a semi-active suspension system, a steering system, or a braking system, and / or the control strategy for the second wheel can at least partially depend on the value of a state parameter of the vehicle (e.g., the speed of the vehicle). In some embodiments, the vehicle can also include a third wheel and a fourth wheel, wherein the control strategy for the second wheel can include initiating a warping vertical wheel force pattern among the four wheels and / or bouncing the second wheel at a predetermined frequency (e.g., at the wheel hop frequency of the second wheel).

[0006] As used herein, when referring to a pair of wheels that may encounter a particular road feature or are actually traveling on the same section of road surface, "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 having more than four wheels, the first wheel or front wheel can be any leading wheel, and the second wheel or rear wheel can be any trailing wheel that encounters or interacts with a given road feature or a given section of road surface.

[0007] In some aspects, the techniques described herein relate to operating a first vehicle, including: receiving information about a first interaction between a wheel of a second vehicle and a negative road feature; based on the information, determining a characteristic of the negative road feature; based on the characteristic, developing a wheel control strategy to minimize the amount by which the wheels of the first vehicle sink into the negative road feature; causing the wheels of the first vehicle to interact with the negative road feature; and during a second interaction, implementing the wheel control strategy. In some embodiments, the first vehicle and the second vehicle can be the same vehicle, the negative road feature can be a pothole, the characteristic of the negative road feature can be the length or depth of the pothole, the control strategy for the second wheel can include using an active suspension system, a semi-active suspension system, a steering system, or a braking system, and the control strategy for the second wheel can at least partially depend on the value of a state parameter of the vehicle (e.g., the speed of the vehicle). In some embodiments, the first vehicle can include a total of four wheels, wherein the control strategy for the second wheel can include initiating a warping vertical wheel force pattern among the four wheels or bouncing the second wheel at a predetermined frequency (e.g., at the wheel hop frequency).

[0008] In some aspects, the techniques described herein relate to operating a first vehicle, including: driving the vehicle along a road surface, where the road surface includes features; receiving, with a controller, information about the feature; determining when a first wheel of the vehicle will reach the feature; determining a force input curve to reduce the normal force on the first wheel when the first wheel reaches the feature, where the first force input curve is configured to at least improve occupant comfort, vehicle safety, and / or vehicle driving performance. The information about the feature can be collected from sensor signals on-board the first vehicle during one or more previous drives of the same vehicle, during previous drives of multiple vehicles. In some embodiments, the information about the vehicle can be received by a controller in the first vehicle from sensors on-board the first vehicle. For example, when a first wheel of the first vehicle interacts with a feature, sensors on-board the first vehicle can receive information about the feature, which can then be used to mitigate the adverse effects of the interaction between a second wheel of the first vehicle and the feature.

[0009] In some aspects, the techniques described herein relate to operating a first vehicle, including: driving the first vehicle along a first road surface; modifying the normal force on at least a first tire of the first vehicle according to a predetermined pattern; determining, with an on-board sensor, the variation of the wheel angular velocity of the first wheel with respect to the normal force; comparing the variation of the wheel angular velocity of the first wheel with respect to the normal load with previously obtained reference data; and based on the comparison, determining the value of a parameter. In some embodiments, the parameter can be the coefficient of friction between the first tire and the first road surface. In some embodiments, the reference data can be the variation of the wheel angular velocity of a second wheel with respect to the normal load, the reference data can be the previously obtained variation of the wheel angular velocity of the first wheel with respect to the normal load, the normal force can be modified by using an active suspension actuator placed between the first wheel and the vehicle body of the first vehicle, and / or the normal force can vary at a predetermined frequency (e.g., effectively the wheel bounce frequency of the first wheel).

[0010] In some aspects, the techniques described herein relate to operating a first vehicle, including: driving the vehicle along a road surface; anticipating the interaction between a wheel of the vehicle and a positive feature, where the height of the feature is greater than the available suspension travel or greater than the desired suspension travel; planning a trajectory that limits the suspension travel to the available or desired suspension travel within the limits of the available actuator force while maximizing the comfort level of one or more vehicle occupants; and commanding an actuator to move a portion of the vehicle, where at least the portion of the vehicle is commanded to follow the planned trajectory.

[0011] It should be understood that the foregoing concepts, as well as additional concepts discussed below, may be arranged in any suitable combination, as the present disclosure is not limited in this respect. Further, 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component that is illustrated in various figures may be represented by the same reference numeral. For clarity of purpose, not every component may be labeled in every drawing. In the drawings:

[0013] Figure 1 Illustrate the main examples and stages during which a vehicle interacts with or traverses road features through the front and rear wheels.

[0014] Figure 2 Illustrate a torsional mitigation strategy for the rear wheels.

[0015] Figure 3 Illustrate a block diagram of a rear wheel preview controller.

[0016] Figure 4 Illustrate a possible implementation of a soft saturation algorithm.

[0017] Figure 5 Illustrate a wheel encountering a road event.

[0018] Figure 6 Illustrate the time traces of wheel acceleration and longitudinal acceleration of a vehicle traversing an event first on the front wheels and then on the rear wheels.

[0019] Figure 7 Illustrate a schematic layout of the wheels.

[0020] Figure 8 Illustrate a typical carpet plot of the longitudinal force on a tire varying with the vertical force and longitudinal slip.

[0021] Figure 9 Illustrate the difference in wheel speed and road surface friction when simulating a vehicle energizing the wheels in a repetitive pattern.

[0022] Figure 10 Illustrate the relationship between the peak-to-peak wheel speed difference of a calculated simulated vehicle and the road surface friction.

[0023] Figure 11 Illustrate the relationship between the peak-to-peak wheel rotational acceleration of a vehicle with an additional tire load applied in a slow warp mode and the road surface friction.

[0024] Figure 12 Illustrate a schematic representation of a wheel and suspension about to traverse a positive event.

[0025] Figure 13 Shows a schematic representation of a wheel and suspension about to cross a positive event according to a trajectory plan.

[0026] Figure 14 Shows a schematic representation of a wheel and suspension during crossing of a positive event.

[0027] Figure 15 Is a schematic diagram of an embodiment of a vehicle including a vehicle control system and vehicle sensors. Detailed implementation

[0028] In some embodiments, a cloud-based crowdsourcing system with a database of known road features that communicates with one or more microprocessors on board the vehicle can notify one or more control systems in the vehicle of interactions with upcoming or anticipated road features (e.g., potholes, manhole covers, bumps), i.e., road events. Alternatively or additionally, as Figure 15 shown, a sensor-based forward-looking system (e.g., a system based on a camera device, LIDAR, RADAR, or similar non-contact forward-looking sensor 223) can be used. However, either of these systems may not be readily available or effective. Alternatively or additionally, when the front wheel (and associated front axle) interacts with or crosses a given road feature, information from one or more on-board motion sensors 223a can be utilized in real time. Such information can provide the vehicle control system with information about upcoming or anticipated events (e.g., interaction of another part of the vehicle (e.g., the rear wheel) with the road feature). The vehicle control system can then use one or more actuators to mitigate the impact of the interaction of the rear wheel or axle with the road feature on the vehicle. By using such information from on-board motion sensors, in some embodiments and under certain operating conditions, the reliance on a forward-looking system can be reduced or eliminated.

[0029] To provide these benefits, the following process can be implemented. First, based on information collected during the interaction of the front wheels with the road feature in the previous cycle, a detection method can be used to predict the behavior of the vehicle during the expected interaction of the rear wheels of the vehicle with the road feature. The method can include determining certain characteristics of the feature, such as the size and / or shape of the feature, based on information collected during the front wheel interaction. Next, an actuation system that uses such information can be utilized. The actuation system can include, but is not limited to, an active suspension actuator, an active roll actuator, a brake actuator, a steering actuator, a semi-active suspension actuator, or other actuators. Finally, a method for commanding the actuation system can be used to maximize the benefits to the vehicle and / or the occupants that are at least partially derived from prior information. Such methods can be specific to each particular actuation system and / or each type of feature, or they can share common elements.

[0030] In some embodiments, discrete steps can occur when the vehicle traverses or interacts with a road feature. Referring to Figure 1 , when the front wheels 1 of the vehicle 3 reach or interact with a feature 5 (e.g., a pothole) in the road surface 7, a first step 1A can occur. During phase 0, an on-vehicle detector that operates continuously or intermittently can receive and analyze sensor data, which can be segmented into buffers of a certain size. Phase 0 can extend beyond phases 1 and 2 and occur simultaneously with phases 1 and 2. During phase 0, data can be obtained or received, for example, from motion sensors such as acceleration sensors, speed sensors, or position sensors mounted on or near the front axle and / or on the vehicle body, or from other sensors that indicate the motion of the vehicle or the motion of vehicle components such as, for example, a wheel 1 or a portion of the unsprung mass associated therewith. In Figure 1 the illustrated embodiment, at step 1B, the road feature has been detected, phase 1 begins, and a vehicle control system (e.g., a central controller, a brake system controller, an active or semi-active suspension controller, a driver assistance system controller, a propulsion system controller, etc.) can be triggered to develop or select a mitigation strategy to, for example, prepare for the interaction of the rear wheels 9 with the road feature 5 or the traversal of the road feature 5. The mitigation strategy can include controlling the actuators and / or modifying the operating parameters of one or more control systems of the vehicle. For example, in the case of an active suspension system, the mitigation strategy can involve activating certain suspension forces or changing control parameters such as the damping coefficient. Due to physical system limitations (e.g., limited actuator bandwidth), the mitigation strategy may take time before it can be fully implemented (at time step 1C). After time step 1C, the control system can prepare for the interaction of the rear wheels with the road feature 5 or the traversal of the road feature 5. At time step 1D, the rear wheels have interacted with or traversed the feature, and the adverse effects from the event may have been mitigated.

[0031] The duration of Phase 1 can depend on the vehicle control system and determines how much time is available for classifying and categorizing the event at the front wheel after the detector has detected an interaction with the feature at the front wheel, such that the mitigation strategy can take effect before the rear wheel reaches the event. Without wishing to be bound by theory, the duration from time step 1A to time step 1D is the transit time from the front wheel to the rear wheel and can be calculated by the following formula:

[0032]

[0033] Thus, the maximum available time for the detector can be given by the following formula:

[0034]

[0035] where MaxTimeForMitigation can be the maximum time required for the vehicle control system to prepare for the road crossing event. For example, an active suspension system may require approximately 100 ms to achieve the desired force, and the wheelbase of the vehicle can be 3 meters long, and it will follow that:

[0036]

[0037] For each vehicle control system and mitigation strategy, there is a speed at which the detector may not have enough time to detect the road feature and implement the mitigation strategy. However, the inventors have recognized that when less time is available for Phase 1, the negative impact of crossing certain features such as potholes at higher speeds may be less significant.

[0038] MaxAvailTime can determine the maximum length of the buffer used to segment the upcoming data. The length of the buffer can affect the detection performance because it may be more challenging to identify road features in shorter data segments than in longer ones. A certain degree of overlap between consecutive buffers may be beneficial to ensure that the vehicle response when crossing the road feature is fully captured within the data, rather than just a part of the response. The appropriate amount of overlap can depend on the type of road feature, as some features can generate a longer vehicle response and thus more overlap between segments may be appropriate to ensure the entire response is captured.

[0039] The data contained in each buffer can be processed using a detection algorithm that can be implemented in a processor on-board the vehicle or can be implemented in a second vehicle or another remote processor such as a processor located in the cloud. In some embodiments, conventional methods for anomaly detection in short time series can be used as the detection algorithm. For example, several statistical measurements can be computed to identify sudden changes in the data. These techniques have some advantages, including low computational cost and sometimes simplicity, but may also have significant limitations. For example, conventional methods may have several parameters that need to be tuned individually for each test case; their detection performance may be mediocre; and they may not be easily scalable. Scalability is a desirable property or factor for such applications because a large library of road features can be created. In some embodiments, each type or class of road feature may require a unique mitigation strategy from the same or different vehicle control systems. Additionally, for a given mitigation strategy, some classification of the road features may be required based on the nature of the road feature (e.g., classification based on the length, depth, sharpness of the edges, width, and / or shape of a pothole). In some embodiments, machine learning-based methods can be used for road feature detection because, although they are complex, they can be highly scalable, modular, and can address classification problems. A machine learning model can be trained on a representative dataset to perform high-confidence predictions on an unknown dataset. In this context, a positive prediction can correspond to road feature detection, while a negative prediction can correspond to no detection. If sensor data has been previously collected and stored in an external storage device, the training process can be performed offline outside the vehicle, but if the data can be stored in the vehicle, the training process can also be performed on the vehicle. A compact trained machine learning model can be deployed and used as an input to the previously described data buffer. Examples of such models can include, but are not limited to, the k-nearest neighbor algorithm, the support vector machine algorithm, neural networks, etc.

[0040] The detection of upcoming road features can benefit several 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 may occur on one side (left or right) of a vehicle at a given time and that is comparable in size to or smaller than the vehicle. During a SWNIE, the road surface drops away from the vehicle before returning towards the vehicle. Examples of such features can include, but are not limited to, potholes, manhole covers, drain grates, gullies, etc. When a wheel traverses such a road feature, the wheel may start to fall into the feature. Before the wheel interacts with the SWNIE, the suspension spring associated with the wheel may be compressed due to the mass of the vehicle body (e.g., (for a four-wheel vehicle) equivalent to approximately 1A load of 1 / 4 can be stored in each suspension spring, with the weight being distributed approximately evenly across the front and rear sides and the left and right sides of the vehicle. Due to the energy stored in the springs, the acceleration of the wheel can be high when the wheel drops into a SWNIE. When the wheel is suspended, the energy stored in the spring can be released, and the wheel may strike the edge of a road feature, for example, in the longitudinal and / or vertical directions, resulting in an adverse effect on the vehicle body. To mitigate the effects of such events, an active suspension system can apply a torsional force at the four wheels. In a four-wheel vehicle, the torsional force can include the implementation of simultaneous or substantially simultaneous pull-up and push-down commands for each pair of diagonally opposite wheels. For example, if it is expected that the left rear wheel of the vehicle will interact with a SWNIE, a compressive force can be applied at the left rear wheel and the right front wheel, while, substantially simultaneously, a stretching force can be applied at the right rear wheel and the left front wheel. In this way, the left rear wheel can be prevented from dropping into the SWNIE, or the left rear wheel can drop with a reduced acceleration. Thus, the impact of the left rear wheel at the far end of the SWNIE on the vehicle can be mitigated or eliminated.

[0041] Figure 2 A series of events that may occur when the front wheel 20 of the vehicle interacts with or traverses a pothole 22, and the corresponding force commands 23 that can be issued to an actuator associated with the rear wheel 24 on the same side of the vehicle, are shown. In certain embodiments and operating conditions, a torsional force can be applied after the front wheel interacts with the pothole and the detector detects the presence of the pothole. However, a delay period can be considered to allow the post-shake motion to dissipate at the front wheel 20 before the torsional force can be applied. The inventors have recognized that such a delay may be needed to avoid prolonging the period of front wheel oscillation. Once the target force command is given, there may be a time interval before the actuator reaches full force. After such a time interval, the mitigation may take effect or be fully effective, and the rear wheel may be lifted or may drop into the pothole with a reduced acceleration (depending on the target force level and the ability of the actuator to generate the commanded or desired force). The detector can also be used to detect the rear wheel impact. Once the rear wheel impact is detected, the controller can return the force command to zero to conserve energy and / or enable the system to be ready to respond to the next road feature. The detector can be a relatively simple detector since the impact can be expected within a certain time window after the front wheel interaction.

[0042] It should be noted that the information collected on the front wheels of the vehicle described herein can also be from an external source, such as, for example, from a vehicle ahead via vehicle-to-vehicle communication, from a vehicle ahead via communication using a cloud server, or from the vehicle itself using non-contact preview sensing capable of determining the characteristics of an event.

[0043] As used herein, the term "post-preview" refers to a method of periodically, occasionally, or continuously controlling an actuator using information from a front or pilot wheel or from a sensor in front of a follower wheel at a rear or follower wheel, with the goal of improving the isolation of the overall vehicle from road disturbances. At a high level, it can include a real-time road z estimator operating, for example, at the front axle or based on sensor information in front of the axle. The road z estimate can then be used to determine, for example, the open-loop force or optimal feedforward of a rear or follower actuator in advance by, for example, inverting the wheel motion response or a model of the vehicle.

[0044] Since it can be calculated using prior knowledge, this force may not have some of the inherent limitations of a force determined by a feedback controller alone. For example, it can be filtered non-causally, allowing for the control of a desired frequency range with good phase accuracy, while a force from only feedback may have an undesirable effect due to the phase introduced by an equivalent real-time filter. In some embodiments, by reducing the effects of, for example, the interaction of the rear wheels with road surface features, the overall vehicle heave and pitch motions as well as roll motion can be mitigated. It should be noted that non-causal filtering may require a certain duration of preview knowledge due to the transients of the filter. At higher speeds, the time between the interaction of the front and rear wheels with road surface features may be shorter. As this time becomes shorter, the frequency range for which rear wheel preview can be used to effectively control the rear wheel motion may also decrease.

[0045] In some embodiments and under certain operating conditions, when a front wheel interacts with a discrete road surface feature, one or more vehicle controllers running on one or more microprocessors can receive information from on-vehicle motion sensors. One or more vehicle controllers on-board the vehicle can use this information to control aspects of various vehicle systems in response to the interaction of the rear wheels with the feature.

[0046] Additionally or alternatively, in some embodiments and under certain operating conditions, when a front wheel interacts with the same or substantially the same road surface, one or more vehicle controllers running on one or more microprocessors can estimate one or more characteristics of the road surface in front of the rear wheels by monitoring aspects of the front wheel motion measured by on-vehicle motion sensors. Estimation of road surface characteristics such as, for example, road surface profile, coefficient of friction, road roughness, road texture, etc., as described above, can occur intermittently, substantially continuously, or continuously, as the present disclosure is not limited in this regard.

[0047] Figure 3FIG. 0 is a block diagram of an implementation of a preview controller 29 that generates a force command at block 41 for at least one actuator associated with a rear wheel (e.g., an active or semi-active suspension actuator). The preview controller 29 may receive sensor data regarding front wheel motion caused by the interaction of the front wheels with a portion of the road surface at block 30 and receive vehicle speed information at block 31. A road estimator at block 32 is configured to estimate values of parameters related to one or more aspects of that portion of the road surface based at least in part on information from the sensors at block 30. Referring to Figure 3 , the road estimator 32 may use available sensor information 30, such as a z-axis sensor, for example, to generate a real-time estimate of the change in road position of the road normal, i.e., the road profile under each wheel. In some implementations of the preview controller 29, the sensors may include one or more accelerometers attached to the unsprung mass or shock absorber, ride height sensors, and accelerometers or IMUs attached to the vehicle body. In some implementations, the change in the normal direction of the nominal road surface, i.e., the z-estimate, may be the absolute position or rate of change in the normal direction of the nominal road surface.

[0048] As used herein, when referring to a road z-estimate, it should be understood that the estimate may be a representation of at least the vertical road profile along the path in front of the wheel; the estimate may describe the vertical profile of a function related to the actual road profile or its spatial derivative, which function captures how the road interacts with the tire and wheel assembly, as the tire will envelop some road content features while following others. In some implementations, the function may represent the path of the tire contact patch, or the abstract concept of the tire contact patch as a single point contact. In some implementations, the function may be the road profile received by a non-contact sensor such as a laser, radar, or Lidar, and may be processed using a tire model to capture the tire envelope of the road content. In some implementations, the function may be accurate within a defined time or spatial frequency range, such as, for example, for features longer than the tire contact patch, or for features acquired in the time domain between 0.5 Hz and 8 Hz, or for features in another time or spatial frequency range.

[0049] In some implementations of the preview controller 29, an inverse model of at least a portion of the vehicle and its suspension may be used to estimate one or more characteristics of the road surface. Since the estimator may be a real-time estimator, its inverse model may need to be low-pass filtered. Relative to a perfect road estimator, low-pass filtering may introduce phase errors. However, such phase errors may be corrected during non-causal filtering at a later step.

[0050] For rear wheel preview, one or more road parameters of the road surface traversed by the two front wheels can be estimated in real time and transmitted to the next subsystem, namely the time buffer at block 33. In some embodiments, the time buffer can maintain a rolling buffer of these road surface estimates, such as a one-second buffer. The length of the buffer can be a more important consideration at very low speeds of driving than at higher speeds. For example, a one-second buffer can be sufficient as long as the time between the front and rear driving reaching the same location in the road surface remains at one second or less. In a typical vehicle with a wheelbase of about 3 meters, this can allow effective control of vehicle speeds as low as 3 m / s (about 7 mph). For control below this speed, the buffer length can be increased.

[0051] In Figure 3 embodiments, once a buffer of road estimates has been generated, it can be filtered non-causally in block 34. Non-causal filtering can include applying a band-pass filter forward on the buffer and then backward on the buffer to achieve reduced phase change through a single one-way filtering operation. In some embodiments, this can allow the content of the road estimate (and thus the force command) to be controlled within an appropriate frequency range. In some embodiments of the preview controller 29, the effective frequency range can extend from a lower limit of about 1 to 5 Hz depending on the vehicle speed to an upper limit of about 7 to 10 Hz depending on the inverse model accuracy. However, a frequency range extending between lower and / or upper limits different from those indicated above can be used, since the present disclosure is not limited thereto.

[0052] The forward pass and the backward pass can be separated such that the forward pass is a normal real-time filter located immediately after the road estimator. Then, the backward pass can remain in the position shown in the figure. In some embodiments, such an arrangement can reduce the computational burden and avoid the transients that the forward pass would have when applied directly to the buffer.

[0053] However, the backward pass may still have transients. In some embodiments, each time a new road estimate point is added to the time buffer, it may be necessary to reapply the backward pass. It can display the typical transients expected when applying the filter to the start of the signal. This can result in the most recent points in the buffer not representing the ideal non-causal filtered road. The transients may have a reduced effect on the older points in the buffer.

[0054] The degree of the transient can be mainly determined by the low-frequency cut-off of the band-pass filter. In this way, in some embodiments, the transient can be shortened at the expense of narrowing the frequency range of the preview operation after reduction. The higher the vehicle speed, the shorter the time delay between the front axle and the rear axle. To keep the filter transient shorter than this time delay, the low-frequency limit of the band-pass filter can be adjusted according to the speed. However, in some embodiments, above a certain speed (e.g., 45 to 60 mph), the band-pass may become too narrow such that the preview after may be ineffective.

[0055] In addition, in some embodiments, at block 34, phase correction can be applied to the buffer to nullify the phase introduced at the real-time road estimator.

[0056] The inverse model (e.g., transfer function) at block 35 can be used to transform the buffer of the filtered road estimate to the force domain. For example, it can use the model of the rear body and the suspension and invert it to determine the force command that will most effectively isolate the effects that make the vehicle and the rear wheels interact with the road surface. Since this inverse model can be applied to the buffer of the preview information rather than processing the real-time input, it can maintain a perfect or virtually perfect phase relationship.

[0057] The model itself can be a simplified quarter-car model. In some embodiments, such models can provide satisfactory accuracy up to the wheel-hop frequency (usually about 12 Hz). Therefore, the upper limit frequency of the non-causal band-pass filter can generally be lower than this value (e.g., 7 to 10 Hz).

[0058] In some embodiments, if appropriate, the Figure 3 shown blocks can be rearranged, blocks can be combined, added, and / or removed, as the present disclosure is not limited thereto. For example, blocks 33, 34, and 35 can be combined into a single linear transformation. Such a combined transformation can use, for example, a method of applying one or more causal or non-causal filters.

[0059] The post-delay estimation at block 36 can continuously estimate the delay between the front wheel and the rear wheel. More specifically, given the longitudinal position of the rear wheel, it can calculate how long it has been since the front axle was at the same position. Simply dividing the wheelbase by the speed can provide a sufficiently accurate estimate at nearly constant speeds. However, when the vehicle speed is a changing speed (i.e., the car is accelerating or decelerating), this estimate may not be accurate enough.

[0060] In some embodiments, the speed can be integrated to calculate continuously increasing distance values. Then, the distance values can be added to a rolling one-second buffer. To determine the front-to-back delay, a search can be performed in the buffer to find the point where the wheelbase is less than the current distance value of the vehicle. For example, if the current distance value of the vehicle is 335.2 meters and the car has a 3-meter wheelbase, a search for 335.2 - 3 = 332.2 meters can be performed in the buffer. If that point is found to have appeared in the buffer 0.35 seconds ago, the front-to-back delay can be determined to be 0.35 seconds. Driving below 3 m / s may require a buffer longer than one second for continuous use of preview. In the interpolation block 37, the delay estimate is used to pick out which point in the force command buffer should be used at the current time step.

[0061] In some embodiments, a filter 38 can be used to remove spurious measurements that may be received from the motion sensors, which are not caused by the road surface but by vehicle-related artifacts such as wheel imbalance, bushing looseness or wear, and engine imbalance. If the effects of such spurious signals are not eliminated or mitigated, the commanded force may cause unnecessary movement at the rear of the vehicle. For example, wheel imbalance may introduce suspension and vehicle movement that is not the result of the road surface or actuator forces. This anomaly can lead to an incorrect road estimate and thus an incorrect force command, which may result in poor isolation performance.

[0062] The frequency of the wheel imbalance-driven anomaly can depend on how fast the wheel is rotating. The main disturbance may occur once per wheel rotation, so if the wheel rotates 5 times per second, the disturbance will be at 5 Hz. The rotational speed and thus the disturbance frequency can change according to the vehicle speed, but typically introduce content within a very narrow, sharp frequency range based on speed.

[0063] In the distance domain, the disturbance frequency can be effectively constant, for example once per tire circumference. In some embodiments, the imbalance filter can utilize this behavior, such as fitting a sine wave to the input at this fixed distance domain frequency. The sine wave phase and magnitude can be updated based on the most recent inputs. Then, the imbalance fit can be subtracted from the input to eliminate its effect.

[0064] As a result of the open-loop nature of the preview controller 29, applying nonlinear effects may be safer than when using feedback signals. Therefore, a soft saturation that effectively limits the preview force to below a certain magnitude can be used at block 39. For inputs below a certain magnitude (usually about 1000 N), the output can be the same as the input. Then, for inputs above the lower threshold, they can be attenuated such that, for example, the output can asymptotically approach the upper limit. Figure 4 An exemplary implementation of such a relationship between the input and the output is shown.

[0065] In some embodiments and under certain operating conditions, the effects of the interaction between the rear wheels of a vehicle and discrete features or irregularities of the road surface, such as, for example, potholes, speed bumps, manhole covers, road cracks, etc., can be mitigated by pre-energizing the rear wheels. This can allow the vehicle to prepare the rear wheels for possible impacts and minimize the longitudinal and / or vertical disturbances caused by such impacts. When a vehicle traveling on a road encounters or traverses a feature or object on the road, the wheels may be compressed or extended. Due to the normal force on the wheels, any road content or feature traversed by the wheels may cause a force to be applied to the wheels that has a component in a horizontal or longitudinal direction in addition to a component in the normal direction of the nominal surface of the road. Thus, the disturbance can be a force having components in the direction of travel of the vehicle or in the direction opposite to the direction of travel of the vehicle and in the road normal.

[0066] Figure 5 A schematic illustration shows 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 can include the total weight and possibly dynamic forces. When the wheel 50 interacts with the road feature 52, the reaction force 58 applied by the road surface 54 and the road feature 52 can have a vertical component that can be equal to the total vertical force, which includes the vertical force 56 and the inertial forces from the motion of the wheel and tire itself. However, the reaction force 56 can also have a horizontal or in-plane component that depends on various characteristics of the road, such as the road grade and road shape; various characteristics of the wheel, such as the diameter, shape, and characteristics of the tire and belt; the characteristics of the suspension, such as longitudinal compliance; and the vertical force applied to the tire at any given moment. At the moment of impact with the feature 56 or actually at the moment of impact with the feature 56, the longitudinal component of the force 58 can be proportional to the vertical force on the tire.

[0067] In some embodiments, a motion state can be induced in the wheel 50 before it approaches the discrete road feature 52 such that when the interaction between the wheel 50 and the road feature 52 occurs, forces such as longitudinal forces, normal forces, or total forces caused by the interaction are mitigated and the adverse effects on the vehicle and vehicle occupants are mitigated.

[0068] To establish such a desired motion state, first, the characteristics and its location of the feature can be identified and / or characterized before the vehicle's wheels interact with the feature. In some embodiments, information about the road surface feature in front of the vehicle can be based on prior measurements made before the wheels interact with the feature, such as by using: (i) other dedicated vehicles equipped with road mapping instruments such as a laser road mapping system; (ii) data about the feature collected by one or more vehicles during a previous drive; and / or (iii) forward-looking sensors such as camera devices, radar, or LiDAR to identify and characterize the feature. Alternatively or additionally, data collected during the interaction of the vehicle's front wheels with the feature can be used to characterize the feature and establish the desired motion state of the rear wheels before the rear wheels interact with the feature.

[0069] The characteristics of the feature that can be determined can include its scale (e.g., the height, depth, length, and / or width of the event) and its location (relative to the vehicle, relative to the road surface, and / or in an absolute sense). When approaching the feature, a motion plan can be prepared for the wheels of the vehicle approaching the feature. Then, actuators (e.g., active suspension actuators, roll actuators, air spring actuators, or other devices that move the wheels relative to the vehicle body) can be used to affect the movement of the wheels before interacting with the feature.

[0070] In some embodiments, the normal force on a tire when a wheel encounters a feature can be reduced, thereby mitigating the shock (e.g., longitudinal, normal, total shock) that may be transmitted to the wheel or the vehicle body. This reduction can be achieved by a plurality of devices. In some embodiments, two roll actuators, or four actuators mounted at the corners of a four-wheel vehicle, or at least four actuators mounted on at least four wheels of a vehicle having more than four wheels, or at least two actuators capable of lifting an axle on a vehicle having at least three axles can be used. Using such a set of actuators, unloading of some tires can be achieved at the expense of increasing the load on other tires while maintaining the total support force on the vehicle. In some embodiments, this can be achieved by driving one of four active suspensions, air springs, or load leveling actuators that are mounted in a torsional or warping mode at or near each corner and attached to a wheel or the unsprung mass of the vehicle. For example, adjacent actuators can apply equal and opposite forces to their respective wheels. For example, forces can be applied at the four corners of a vehicle having four wheels, where the left front actuator can apply a positive force such that the right front applies a negative force of the same magnitude, the left rear applies a negative force, and the right rear applies a positive force. This may result in unloading of the right front and left rear wheels (if the convention is that a positive force increases the load on the wheel), while supporting the vehicle by increasing the load on the left front and right rear wheels. In another embodiment, a similar effect can be achieved by driving two roll actuators each mounted to an axle of a vehicle having two axles such that one actuator generates a roll moment to the left while the other actuator generates an equal and opposite roll moment to the right.

[0071] Alternatively, instead of applying forces in a torsional mode, in some embodiments, unloading of the wheel about to interact with the feature can be achieved dynamically. The target wheel can be accelerated to change its inertial force and the direction of that force. The inventors have recognized that a tire typically behaves as a lightly damped spring in the vertical direction and thus, in combination with the mass that moves with the wheel (commonly referred to as the “unsprung mass”), forms a lightly damped resonant second-order system. Actuators can be used to repeatedly apply forces in an appropriate mode to excite the resonance of the unsprung mass on the tire, thereby using the amplification provided by the resonant behavior of the dynamic system to generate more motion and thus cause proper timed unloading of the wheel.

[0072] Figure 6The time trace of the vertical acceleration of the front wheels of a vehicle is shown in the top figure 59a, the time trace of the vertical acceleration of the rear wheels of the same vehicle is shown in the middle figure 59b, and the time trace of the longitudinal acceleration of the vehicle chassis is shown in the bottom figure 59c. At time 60, the front wheels cross a feature, and at time 62, the rear wheels cross the same feature. During the time period 64, the front actuator can be used to energize the front wheels in a repeating pattern that matches the resonant frequency of the unsprung mass on the front tire, and is timed such that at time 60 the wheel is at its minimum acceleration (and thus at its maximum height relative to the road surface and is maximally unloaded). Similarly, during the time period 66, the rear wheels on the same vehicle can be energized by an actuator that generates a force in a pattern to excite the resonance of the unsprung mass on the rear tire, and is timed such that at time 62, the wheel is at its minimum acceleration, and thus at its maximum height relative to the road surface, so as to unload the rear wheels when the rear wheels cross the event at 62. As can be observed from the highlighted region 68 in figure 59c, by this method, the longitudinal acceleration generated by the interaction with the feature at times 60 and 62 measured on the vehicle chassis (in this case, near the driver's seat rail mounting point) is significantly reduced.

[0073] It should be noted that while this example shows the wheels being energized in a repeating pattern, other tire unloading patterns can be used as the present disclosure is not limited thereto. Unloading the wheels can occur in a single step, or using a pattern slower than the resonant frequency of the unsprung mass and the tire, as this can reduce power consumption, noise, and vibration or occupant discomfort.

[0074] It is important to note that the different methods described above can be used to mitigate interactions with different types of features, or used in combination with other mitigation strategies such as, for example, torsion mitigation strategies. Unloading the wheels in a torsion mode allows for a longer period of unloading and can thus be applicable to larger features or situations where the relative position of the feature cannot be known with sufficient precision. As discussed above, mitigating the effects of the interaction between the wheels and the road surface features by using oscillatory unloading of the tires may require more precise information about the position of one or more features, but can be activated simultaneously on both sides of the vehicle and can be applicable to symmetric events such as railroad crossings, expansion joints, ridges, and other similar features.

[0075] The inventors have recognized that changing the wheel load 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. Since, under normal operation, the tire may be compressed by the normal force exerted on it (due to the weight and dynamic motion of the vehicle and the wheel), the tire exhibits a certain rolling resistance. This resistance can be referred to as "rolling resistance" and can result in a drag force on the wheel. The tire can be driven or decelerated by drive or brake torques applied respectively by the propulsion system or the brakes. The tire may also be pulled by forces on other parts of the vehicle, e.g., the forces experienced by non-driven wheels (e.g., the rear wheels on a front-wheel drive vehicle), or the forces experienced when the vehicle is coasting or rolling down a slope.

[0076] Figure 7 A schematic illustration shows 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 drive torque, or due to a pulling force applied from another wheel, and / or due to gravity on the vehicle. The reaction force 76 on the ground can be equal and opposite to 74. The tire 70 can support a load or vertical force 78. The ground reaction force 76 can be generated by friction, and the interaction between the tire and the road surface can be characterized by a small amount of slip (commonly referred to as the longitudinal slip ratio). The slip ratio is a function of the tire load and the applied longitudinal force. Figure 8 A typical relationship of the tire, expressed in what is commonly referred to as a carpet plot, is shown to illustrate the relationship between the longitudinal force, the vertical force, and the slip.

[0077] From this plot, it can be determined that at any given vertical force (generated by, for example, the weight of the vehicle, any dynamic forces on the vehicle, and / or any additional actuator forces) and any given longitudinal force (determined by the traction forces that the vehicle can have 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. This slip ratio is also related to the friction between the tire and the surface on which it is located.

[0078] In some embodiments and under certain conditions, if the vertical load of each tire can be varied in a prescribed pattern, then the surface friction can be estimated. Figure 9Shows pattern 90 of a repetitive input applied to a wheel. In some embodiments, this pattern of applying a force at or near the resonance frequency of the unsprung mass on the tire can be advantageous, which can reduce the effort involved in generating load variations, thereby achieving similar load variations at lower actuator forces or higher load variations at the same actuator forces. However, it should be noted that other input frequency patterns can be used, and the present disclosure is not limited to excitation at the resonance frequency of the unsprung mass. Curve 90 shows the wheel speed difference between the wheel on the right side and the wheel on the left side of the vehicle on the same axle, where the wheels can be loaded and unloaded in opposite patterns to enhance the measured difference and improve the resolution of the method. It should be understood that the method can also be applied to a single wheel, and the speed difference can be compared with a reference pattern, an unpowered wheel, or the average of all four wheels. On the same figure, referring to the right axle, curve 92 shows the simulated surface friction for this simulation run. For simplicity, the surface friction used for the simulation is specified to gradually decrease from a value of 1 to near zero in regular increments, allowing a single simulation run to show the entire curve. As can be seen from the curve, on a road with higher surface friction, the wheel speed difference between the right and left sides of the vehicle is greater because the tire will have greater grip and less longitudinal slip.

[0079] Figure 10 This relationship is shown by comparing the surface friction with the measured wheel speed difference between the left and right sides of the vehicle. The curve shows a clear correlation between the two values, allowing an algorithm that extracts the unknown surface friction value based on the wheel speed when the wheels are powered in a specified manner.

[0080] In another embodiment, as discussed above, a slowly varying force can be applied to all four wheels of a four-wheel vehicle in a warping pattern. In this case, a change in surface friction may result in a change in wheel rotational acceleration, which may be more distinguishable than a change in wheel speed and can therefore be used to estimate surface friction. Figure 11 Shows the relationship between the measured wheel rotational acceleration and the surface friction. This method may be preferred in cases where the actuator cannot generate a rapidly varying force pattern or where rapid changes in tire load are not desired for comfort or safety reasons.

[0081] In another embodiment or under different operating conditions, other vehicle sensors can be used to detect changes when a torsional force is applied. For example, changes in the yaw rate related to surface friction and / or tire grip can be detected, where the changes cannot be attributed to the driver or the vehicle controller. Alternatively, if there is a correction by the lane keeping assist function, or the operator, or the steering system in response to a change in the steering torque at the wheel due to a change in friction, then the signal can also be used as a metric for estimating surface friction. Thus, when an actuator force is applied in a warping mode, the response generated by the steering system, the operator, or the driver assist function can be measured, and the surface friction can be estimated based on the measurement.

[0082] Figure 12 A schematic illustration shows a vehicle approaching a positive road feature 120 such as, for example, a speed bump. As used herein, a positive road feature refers to a road feature that protrudes substantially in the vehicle direction, or has a portion that protrudes in the vehicle direction. Positive road features can include, but are not limited to, raised humps, speed bumps, railroad crossings, steps, curbs, road plates, and frost heaves. As used herein, a negative road feature refers to a feature that is substantially away from the vehicle. Such features can include, but are not limited to, potholes, step downs, depressions, sinkholes, and storm drain covers.

[0083] Figure 12 A vehicle is shown having a body 122, a suspension system 124, and a wheel and tire 126 approaching the feature 120. The vehicle is represented as having a single wheel, but can include multiple wheels. When the wheel approaches the road feature 120 or other obstacle, it can be subjected to various forces. In some embodiments and under certain conditions, the wheel and tire 126 can support the weight and dynamic loads of the vehicle. The road surface can exert a reaction force on the tire, which is at an angle related to the slope of the road. In the case of a rising road (meaning when the road inclination has a component opposite to the direction of vehicle motion with respect to the vertical axis of the vehicle), the reaction force on the wheel and tire can push the vehicle backward, while in the case of a road with a downward slope (meaning when the road inclination has a component aligned with and in the same direction as the vehicle motion), the reaction force on the wheel and tire can push the vehicle forward.

[0084] The suspension system can be used to reduce the motion of the body and increase the comfort of the occupants. To achieve this, the suspension can change length when traversing a road obstacle. For example, the suspension can be compressed when traversing a positive feature to absorb at least a portion of the body motion that would otherwise be caused by the feature. However, the travel range of the suspension system is limited. The degree to which the suspension system can be compressed or extended is limited. Figure 12 The illustrated suspension system has a maximum available compression stroke 128 and a maximum extension stroke 130.

[0085] When traversing a feature with a height 132, for example, if the height 132 is less than the maximum available compression stroke 128, the suspension may be able to fully or virtually fully absorb the impact of the feature. However, if the feature height 132 is greater than the available compression stroke 128, the vehicle may not be able to fully absorb the event without exceeding its stroke limit. This can cause a significant increase in the normal force on the tire. Such an increase may be perceived by the occupants as a significant disturbance and may be undesirable.

[0086] Figure 13 Illustrated is the expected interaction with a feature 140, how the suspension system can be adjusted, where the maximum height 142 of the feature 140 exceeds the maximum available compression stroke 144 of the suspension, but does not exceed the maximum total stroke 146. A trajectory 148 of the vehicle can be planned that raises the vehicle to a maximum trajectory height 150. In some embodiments and under certain operating conditions, where the feature height 142 is greater than the available compression stroke 144 but less than the total available stroke 146, the maximum trajectory height 150 can be equal to zero.

[0087] In some embodiments, under certain operating conditions, the suspension system can be configured to follow the planned trajectory and can be able to achieve the trajectory with substantially no deviation therefrom, and then at the maximum height of the event, as Figure 14 shown, the body 152 can be at or near its trajectory height above its original position, while the wheel 154 follows the road and the suspension 144 is compressed by an amount not exceeding its maximum available compression stroke.

[0088] This can be achieved by reducing the amount of change in the tire force when the wheel traverses a road feature. The tire force is given by the sum of the portion of the vehicle's weight on a particular wheel plus the reaction force due to the acceleration of the wheel and the body. Under the simplified assumption of the wheel following a road event, the only remaining variable is the acceleration of the body. The acceleration of the body in the vertical direction can increase the force on the tire, and preferentially and gradually accelerating the body before the interaction can reduce any change in the tire force caused by the interaction. Thus, the optimal solution for the trajectory 148 can be determined by minimizing the acceleration of the body under the constraints provided by the above maximum available suspension stroke, maximum available compression stroke, and road event height.

[0089] Planning trajectories such as the above trajectories may require advance knowledge of the upcoming road, which can be based on local sensors or from other prior knowledge sources. The suspension actuator may be required to be able to modify the position of the vehicle body relative to the ground within a time range suitable for effectively responding to road feature interactions. The appropriate time range can depend on the shape of the road and the vehicle speed. When on a generally flat road with a single positive event, a slow actuator with sufficient warning may be able to lift the vehicle over a long period of time and still be prepared 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 be prepared for the next event. On most roads, it may be preferred to be able to move the vehicle within one second to perform this function, but slower or faster actuators can still benefit from this method as the present disclosure is not limited in this regard.

[0090] It should be understood that in the above discussion, the available stroke may be less than the stroke that the suspension can maintain without hitting hard (physical) or soft limits or exceeding its design specifications. The available stroke limit can be adjustable depending on the operating conditions or set by the designer or controller. It can be set to achieve desired comfort, safety, or driving performance goals, or to match the maximum desired force from the output of the actuator.

[0091] In another aspect of the present invention, the vehicle may encounter unilateral negative features. The vehicle can be warned of the presence of such features by one of the methods described above, such as based on data collected during previous driving, data from one or more different vehicles, data from characterized road segments, data transmitted from the cloud, data stored on the vehicle, or any other such method.

[0092] When the vehicle approaches the feature, the time of the expected encounter event can be calculated using the vehicle's current position relative to the feature, the position of the feature, and / or the current vehicle speed. This calculation can be performed on the vehicle or offline in the cloud before the vehicle approaches the feature. 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 the new expected time can be used if appropriate.

[0093] The inventors have recognized that the likelihood of occupant discomfort and vehicle component damage caused by encountering negative events such as potholes in the road is related to the amount of normal force on the tire that encounters the feature. This is because the wheel and tire must conform to the road profile due to the normal force acting on the tire. This force can include the portion of the vehicle weight supported by a particular tire, as well as any variations caused by dynamic loads on the wheel or vehicle body.

[0094] In some embodiments and under certain operating conditions, an active suspension or an active roll system can be used to reduce the normal force on a tire that is expected to encounter a negative event. This can be achieved by applying a force in a torsional or warping mode such that the suspension actuator increases the force on two opposite tires while increasing the normal force on the other two tires, where one of the tires can interact with the negative feature.

[0095] In some embodiments, when calculating the time at which a force should be applied, three factors can be considered. First, the actuation system may have a response time, and it is necessary to give a force command early enough to achieve the desired force level at the appropriate time. Second, the accuracy of the estimated position of the vehicle or the estimated position of the feature may be limited. In this case, it may be desirable to apply the force command early to compensate for possible errors. Third, applying the force quickly may have an adverse effect on the comfort or NVH (noise, vibration, and harshness) felt by the occupants, and thus it may be necessary to apply the force more gradually. Considering any of these factors relevant to a given situation and the actuator to be used, as well as other possible timing considerations related to the processing speed, the update rate of the processor, or similar factors, the appropriate timing for issuing a force command to the actuator system can be determined to achieve the desired wheel unloading at the moment the vehicle encounters the feature.

[0096] When encountering a feature located on one side of the vehicle, it is also important to consider the fact that the feature will first be encountered by the front wheel on one side of the vehicle and may soon after be encountered by the rear wheel on the same side of the vehicle. For many road vehicles, except during slow maneuvers in a parking lot or during a vehicle side slip (with a large side slip angle), the front and rear wheels follow similar paths during most normal driving. Most road vehicles also have similar front and rear track widths, which means that the front and rear wheels of the vehicle can have the same lateral spacing relative to the vehicle chassis and can thus follow the same path on the road surface. For vehicles or driving situations where either the front or rear wheels do not follow the same path, the application of the event mitigation strategy discussed here can be done independently front and back. However, for vehicles where the front and rear wheels follow the same path or a substantially or virtually the same path, for example, within a lateral offset of less than 1 cm, or less than 5 cm, or less than 10 cm, the time between the front event and the rear event can be recorded. This time will decrease as the vehicle speed increases and is related to the wheelbase of the vehicle (the distance between the front and rear wheels along the vehicle's driving direction). Using similar considerations as those described above for the front wheels, such as considering the specific actuation system to be used on the rear wheels about to encounter the event, the delay inherent in such a drive, the impact of rapid force application on NVH and comfort, and / or other considerations, the optimal time to apply a force to the rear wheels can be determined.

[0097] In certain embodiments and under certain operating conditions, a roll force strategy can be achieved by unloading the front wheels on the same side of the vehicle and increasing the rear wheel load. After the front wheels interact with the road surface, the front wheels may be loaded more, while the rear wheels are unloaded. Thus, at a given speed, the roll strategy can be effective if there is sufficient time to perform such a transition.

[0098] The behavior planner control method is beneficial when considering mitigation strategies to be applied to a given event, driving scenario, speed, user settings, and optionally other vehicle states or user preferences. This behavior planner control method can take information about the type, characteristics, and location of an upcoming event, calculate the optimal timing of a wheel unloading command, decide on the optimal strategy given these timing requirements, and then convey that decision to a downstream control method that calculates and applies the optimal force command to achieve the desired effect. The decision made by the behavior planner control method can include optionally deciding to apply a roll force, deciding to apply other unloading methods, or deciding not to apply any mitigation strategy, or a subset or combination of these strategies, or it can include deciding on the amount of mitigation to apply in each case.

[0099] Figure 15 Vehicle 210 is shown. The vehicle includes a body 212 that supports various components of the vehicle. As Figure 15 shown, the vehicle includes a microprocessor system 214 having one or more microprocessors, and the microprocessor system 214 can communicate with various subsystems via a communication channel 216. Note that in Figure 15 , although the microprocessor system 214 is shown as a single unit, it can include multiple microprocessors located at multiple locations in the vehicle, as the present disclosure is not limited in this regard. As Figure 15 shown, the vehicle can include an active suspension system having active suspension actuators 218 that are operably disposed between the vehicle's wheels 220 (or the wheel assemblies of the unsprung mass) and the body 212 (e.g., the sprung mass). In particular, the active suspension actuators 218 can be operably disposed 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 the respective wheels of the vehicle. Each actuator 218 can be configured to apply a force between the wheel 220 and the body 212. The actuators 218 can affect the motion response of the body 212, particularly one or more vehicle motion characteristics. The vehicle can also include a braking system having brakes 222. The braking system can include independent brakes coupled to each of the vehicle's wheels 220 such that braking force can be independently applied to each wheel. According to Figure 15In the illustrated embodiment, the vehicle may also include a forward-looking sensor 223 and / or other motion sensors 223a (e.g., an inertial motion sensor (IMU), a displacement sensor, an accelerometer, etc.). The forward-looking sensor may include, for example, one or more camera devices, 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 that may be located in the microprocessor system 214. Alternatively or additionally, previously collected (e.g., crowdsourced) forward-looking road information may be received at one or more microprocessors in the microprocessor system 214 from one or more local (i.e., on-vehicle) or remote databases. The motion sensors 223a may be used to provide information about the motion of various parts of the vehicle (e.g., the body, wheel assemblies, active suspension actuators) to one or more microprocessors in the microprocessor system 214.

[0100] According to Figure 15 the embodiment, the vehicle may also include a steering system 224, which, in the case of driving the vehicle, includes a steering wheel 224a. The steering wheel 224a may form part of the user interface of the vehicle 210. The user interface may be used to provide user input to control various parts of the vehicle or to provide feedback to the user, such as haptic feedback. 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 present disclosure is not limited in this regard.

[0101] As Figure 15 illustrated, the vehicle may traverse on a road 226. As Figure 15 illustrated, the road may include a plane of a road surface 228. As used herein, the term "body" refers to the sprung mass of the vehicle regardless of the type of body construction and includes, but is not limited to: a unitary, integrated, or monocoque body construction; a body including a separately formed vehicle chassis attached to other parts of the body; and / or any other type of body construction that serves as the sprung mass supported by the suspension system of the vehicle.

[0102] Although the present teachings have been described in connection with various embodiments and examples, the present teachings are not intended to be limited to such embodiments or examples. Instead, as will be understood by those skilled in the art, the present teachings cover various alternatives, modifications, and equivalents. Accordingly, the foregoing description and drawings are provided by way of example only.

[0103] The above-described embodiments of the technology described herein can be implemented in any of a variety of ways. For example, an embodiment can be implemented using hardware, software, or a combination thereof. When implemented in software, the software code can 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 can be implemented as integrated circuits having one or more processors in the integrated circuit components, including commercially available integrated circuit components known by name in the art, such as CPU chips, GPU chips, microprocessors, microcontrollers, or coprocessors. Alternatively, the processor can be implemented in a custom circuit system such as an ASIC or in a semi-custom circuit system generated by configuring a programmable logic device. As yet another alternative, the processor can 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 such that one or a subset of these cores can constitute a processor. However, the processor can be implemented using any suitable format of circuitry. It should also be understood that any reference to a controller in the present disclosure can be understood as a reference to the use of one or more processors configured to implement one or more of the methods disclosed herein.

[0104] In addition, it should be recognized that a computing device including one or more processors can be embodied in any of a variety of forms, such as a rack-mounted computer, a desktop computer, a laptop computer, or a tablet computer. Additionally, the computing device can be embedded in a device that is not typically considered a computing device but has suitable processing capabilities, including a personal digital assistant (PDA), a smart phone, a tablet, or any other suitable portable or stationary electronic device.

[0105] Furthermore, a computing device can have one or more input and output devices. Additionally, these devices can be used to present a user interface and the like. Examples of output devices that can 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 can be used for a user interface include a keyboard, various buttons, and pointing devices such as a mouse, a touchpad, and a digitizing tablet. As another example, a computing device can receive input information by voice recognition or in other audible formats.

[0106] Such computing devices can be interconnected via one or more networks in any suitable form, including a local area network or a wide area network, such as a corporate network or the Internet. Such networks can be based on any suitable technology, and can operate according to any suitable protocol, and can include wireless networks, wired networks, or fiber optic networks. Additionally, the various methods or processes outlined herein can be encoded as software that can be executed on one or more processors employing any of a variety of operating systems or platforms. These methods can be embodied as processor-executable instructions stored on an associated non-transitory computer-readable medium, which instructions, when executed by one or more processors, perform any of the methods disclosed herein. Additionally, such software can be written using any of a variety of suitable programming languages and / or programming or scripting tools, and can also be compiled into executable machine language code or intermediate code to be executed on a framework or virtual machine.

[0107] In this regard, the embodiments described herein can be embodied as a computer-readable storage medium (or multiple computer-readable media) (e.g., computer memory, one or more flexible disks, compact disks (CDs), optical disks, digital video disks (DVDs), magnetic tapes, flash memory, RAM, ROM, EEPROM, circuit configurations in a field programmable gate array or other semiconductor device, or other tangible computer storage media), which computer-readable storage medium is encoded with one or more programs that, when executed on one or more computers or other processors, perform the methods implementing the various embodiments described above. As is apparent from the foregoing examples, a computer-readable storage medium can retain information for a sufficient time to provide computer-executable instructions in a non-transitory form. Such computer-readable storage media or media can be transportable such that one or more programs stored thereon can be loaded onto one or more different computing devices or other processors to implement the various aspects of the present disclosure as discussed above. As used herein, the term "computer-readable storage medium" encompasses only non-transitory computer-readable media that can be considered an article of manufacture (i.e., a manufactured article) or a machine. Alternatively or additionally, the present disclosure can be embodied as a computer-readable medium that is not a computer-readable storage medium, such as a propagated signal.

[0108] The term "program" or "software" is used herein in a general sense 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 the various aspects of the present disclosure as discussed above. Additionally, it should be recognized that, according to one aspect of this embodiment, one or more computer programs that perform the methods of the present disclosure when executed need not reside on a single computing device or processor, but can be distributed in a modular fashion among multiple different computers or processors to implement the various aspects of the present disclosure.

[0109] Computer-executable instructions can come in various forms, such as program modules, and are 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 program modules can be combined or distributed as needed in various embodiments.

[0110] The embodiments described herein can be embodied as methods, examples of which have been provided. The acts performed as part of the method can be ordered in any suitable way. Accordingly, embodiments can be constructed in which the acts are performed in a different order than shown, the order can include performing some acts simultaneously, even though shown as sequential acts in illustrative embodiments.

[0111] In addition, some acts are described as being taken by a "user". It should be recognized that a "user" need not be a single individual, and in some embodiments, the acts attributed to a "user" can be performed by a team of individuals and / or an individual in conjunction with computer-aided tools or other agencies.

[0112] Although the present teachings have been described in conjunction with various embodiments and examples, the present teachings are not intended to be limited to such embodiments or examples. Rather, as will be understood by those skilled in the art, the present teachings cover various alternatives, modifications, and equivalents. Accordingly, the foregoing description and drawings are provided by way of example only.

Claims

1. A method of operating a vehicle, the method comprising: During a first interaction, interacting a first wheel of the vehicle with a negative road feature; During the first interaction, receiving data from at least one sensor on-board the vehicle; Based on the data, determining a characteristic of the negative road feature; Based on the characteristic, developing a second wheel control strategy to minimize the amount by which a second wheel of the vehicle sinks into the negative road feature; During a second interaction, interacting the second wheel of the vehicle with the negative road feature; And During the second interaction, implementing the second wheel control strategy.

2. The method according to claim 1, wherein The negative road feature is a pothole.

3. The method according to one of claims 1 to 2, wherein, The characteristic of the negative road feature is selected from the group including the length and depth of the pothole, the sharpness of the edge of the pothole, and the width of the pothole.

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

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

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

7. The method according to any one of claims 1 to 6, wherein The vehicle further includes a third wheel and a fourth wheel, and wherein the second wheel control strategy includes initiating a warping vertical wheel force mode among the four wheels.

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

9. The method according to claim 8, wherein The predetermined frequency is the wheel bounce frequency of the second wheel.

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

11. A method of operating a first vehicle, the method comprising: Receiving information about a first interaction between a wheel of a second vehicle and a negative road feature from the second vehicle traveling in front of the first vehicle; Based on the information, determining a characteristic of the negative road feature; Based on the characteristic, developing a wheel control strategy to minimize the amount by which the wheels of the first vehicle sink into the negative road feature; During a second interaction, interacting the wheels of the first vehicle with the negative road feature; And During the second interaction, implementing the wheel control strategy.

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

13. The method according to one of claims 11 to 12, wherein The negative road feature is a pothole.

14. The method according to one of claims 11 to 13, wherein, The characteristic of the negative road feature is selected from the group including the length of the pothole, the depth of the pothole, the sharpness of the edge of the pothole, and the width of the pothole.

15. The method according to one of claims 11 to 14, wherein The wheel control strategy includes using a system selected from the group including an active suspension system, a semi-active suspension system, a steering system, and a braking system.

16. The method according to one of claims 11 to 15, wherein, The control strategy depends at least in part on the value of a state parameter of the vehicle.

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

18. The method according to one of claims 11 to 17, wherein, The first vehicle includes a total of four wheels, and wherein the control strategy includes initiating a warping vertical wheel force mode among the four wheels.

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

20. The method according to claim 19, wherein, The predetermined frequency is the wheel bounce frequency of a second wheel.

21. A method of operating a vehicle, the method comprising: Drive the vehicle along a road surface, where the road surface includes features; At a controller, receive information about the features; Determine when a first wheel of the vehicle will reach the feature; and Determine a force input curve to reduce the normal force on the first wheel when the first wheel reaches the feature, where the first force input curve is configured to improve at least one metric selected from the group including occupant comfort, vehicle safety, and vehicle driving performance.

22. The method according to claim 21, wherein, The information about the feature is collected from sensor signals on-board the first vehicle during one or more previous drives of the same vehicle, during previous drives of multiple vehicles.

23. A method of 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: Drive the first vehicle along the first road surface; Modify the normal force on at least a first tire of the first vehicle according to a predetermined pattern; Use an on-board sensor to determine the change in the wheel angular velocity of the first wheel with respect to the normal force; Compare the change in the wheel angular velocity of the first wheel with respect to the normal load with previously obtained reference data; And Based on the comparison, determine the value of the parameter.

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

25. The method according to one of claims 23 to 24, wherein The reference data is the change in the wheel angular velocity of a second wheel with respect to the normal load.

26. The method according to one of claims 23 to 25, wherein, The reference data is the previously obtained change in the wheel angular velocity of the first wheel with respect to the normal load.

27. The method according to one of claims 23 to 26, wherein, Modify the normal force by using an active suspension actuator disposed between the first wheel bodies of the first vehicle.

28. The method according to one of claims 23 to 27, wherein The normal force changes at a predetermined frequency.

29. The method according to claim 28, wherein, The frequency is substantially the wheel hop frequency of the first wheel.

30. A method of operating a vehicle, the method comprising: Drive the vehicle along a road surface; Anticipate an interaction between a wheel of the vehicle and a positive feature, where the height of the feature is greater than the available suspension travel; Plan a trajectory that limits the suspension travel to the available suspension travel within the limits of the available actuator force while maximizing the comfort level of one or more vehicle occupants; and Command an actuator to move a portion of the vehicle, where at least the portion of the vehicle effectively follows the planned trajectory.

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