# Patent

## Title
Integrated bank and roll estimation using a three-axis inertial-measuring device

## Abstract

A system, for use at a vehicle to estimate vehicle roll angle and road bank angle, in real time and generally simultaneously. The system includes a sensor configured to measure vehicle roll rate, a processor; and a computer-readable medium. The medium includes instructions that, when executed by the processor, cause the processor to perform operations comprising estimating, using an observer and the vehicle roll rate measured by the sensor, a vehicle roll rate. The operations also include estimating, using an observer and a measured vehicle roll rate, the vehicle roll angle, and estimating, based on the vehicle roll rate estimated and the vehicle roll angle estimated, the road bank angle.

## Background
TECHNICAL FIELD
The present disclosure relates generally to systems and methods for estimating road bank and vehicle roll angles and, more particularly, to systems and methods for estimating the angles using a three-axis inertial-measuring device.
BACKGROUND
Modern vehicles are being equipped increasingly with autonomous driving (AD) systems. Operation of these systems is improved with accuracy of vehicle and environmental data available.
Advanced AD systems use data including road bank angle and vehicle roll angle, especially in turning and banked-road situations. The data can also include road grade and vehicle pitch angles.
Road bank angle and vehicle roll angle can be measured, directly, as can be road grade and vehicle pitch angles. The angles can be measured, for instance, using a dedicated optical sensor, and/or a multi-antenna satellite arrangement—e.g., Global Positioning System (GPS). A high-accuracy GPS unit can be placed at each of four corners of a vehicle to measure roll and pitch (and yaw) angles of the vehicle. These methods are very expensive, though, and not feasible within typical consumer price points.
Moreover, measurement data may have inaccuracies due to even slight measurement-device offset or error, noise, and/or failure of the system to still contextualize the measured data—e.g., even if roll-direction movement is accurately detected using GPS units, the system would require accurate road-bank angle data in order to properly determine what proportion of the measured roll-direction movement is due to vehicle roll as opposed to road bank.
The present technology solves these and other shortcomings by estimating accurately both vehicle roll angle and road bank angle, together, using a correcting observer software module applying a tuned observer gain.
SUMMARY
The present disclosure relates, in some embodiments, to a system, for use at a vehicle to estimate vehicle roll angle and road bank angle, in real time and generally simultaneously, comprising a sensor configured to measure vehicle roll rate, a processor, and a computer-readable medium comprising computer-executable instructions that, when executed by the processor, cause the processor to perform various operations.
The operations include estimating, using an observer and a measured vehicle roll rate, a vehicle roll rate. The operations also include estimating, using an observer and a measured vehicle roll rate, vehicle roll angle. And the operations include estimating, based on the vehicle roll rate estimated and the vehicle roll angle estimated, a road bank angle.
In another aspect, the technology includes a method including operations like the operations recited above in connection with the system.
In another aspect, the technology includes a computer-readable storage device, like the computer-readable medium of the system recited above.
Other aspects of the present technology will be in part apparent and in part pointed out hereinafter.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates schematically a vehicle on a banked road, and select variables including road and vehicle angles, according to an embodiment of the present disclosure.
FIG. 2 illustrates an exemplary flow chart of operations of the present technology including a gain adaptation function, according to an embodiment of the present disclosure.
FIG. 3 is a graph showing first example bank and roll estimation data.
FIG. 4 is a graph showing second example bank and roll estimation data.
FIG. 5 is a graph showing first example vehicle roll estimation data as compared to measured roll data.
FIG. 6 is a graph showing second example vehicle roll estimation data as compared to measured roll data.
FIG. 7 is a graph showing third example vehicle roll estimation data as compared to measured roll data.
FIG. 8 illustrates an exemplary computing system for use in performing functions of the present technology.



It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. Dimensions of some of the elements may, for example, be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements.
DETAILED DESCRIPTION
As required, detailed embodiments of the present disclosure are disclosed herein. The disclosed embodiments are merely examples that may be embodied in various and alternative forms, and combinations thereof. As used herein, for example, “exemplary,” and similar terms, refer expansively to embodiments that serve as an illustration, specimen, model or pattern.
Descriptions are to be considered broadly, within the spirit of the description. For example, references to connections between any two parts herein are intended to encompass the two parts being connected directly or indirectly to each other. As another example, a single component described herein, such as in connection with one or more functions, is to be interpreted to cover embodiments in which more than one component is used instead to perform the function(s). And vice versa—i.e., multiple components described herein in connection with one or more functions is to be interpreted to cover embodiments in which a single component performs the function(s).
The figures are not necessarily to scale and some features may be exaggerated or minimized, such as to show details of particular components.
In some instances, well-known components, systems, materials or methods have not been described in detail in order to avoid obscuring the present disclosure. Specific structural and functional details disclosed herein are therefore not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to employ the present disclosure.
I. Overview of the Disclosure
In various embodiments, the present disclosure describes at least one algorithm configured to estimate road bank angle and vehicle roll angle. The road bank angle is the angle formed between a road on which the vehicle is positioned and true or environmental-frame horizontal, which can also be referred to as the earth plane or sea plane.
The vehicle roll angle is an angle between a sprung portion of the vehicle and the balance of the vehicle. The sprung portion of the vehicle is generally that portion connected above the suspension and the tires.
In one embodiment, the angles are estimated using output from a three-axis inertial-measuring device. The angles can then be used in various vehicle functions. In a primary scenario, the angles estimated are used in support of autonomous-driving functions.
In some embodiments, the technology is configured to estimate the road bank angle and vehicle roll angle simultaneously, or generally simultaneously.
The algorithm(s) is in some implementations embodied at least partially by computer code configured to cause a processor to perform some or all of the operations described herein.
As provided, operation of autonomous-driving systems is improved when more-accurate data about the vehicle and environment is available. The accurate data is especially useful in situations in which the vehicle is maneuvering, such as turning, and/or when the road varies from flat, such as by having a grade and/or bank.
The present technology can be used to provide accurate road and vehicle position data including road bank angle and vehicle roll angle. The technology can also be used, analogously, to estimate accurately road grade and vehicle pitch angles.
Autonomous-driving-related functions improved by high-accuracy estimations of road angle and vehicle angle includes camera-sensing. The vehicle uses the angle information in interpreting vehicle camera data. The information is helpful especially when the vehicle is on a road that is banked and/or pitched and the system may otherwise not accurately contextualize the camera data.
Cameras are commonly mounted rigidly to the sprung portion of the vehicle, and so move in response to vehicle roll. Without data indicating vehicle sprung movement (e.g., roll, pitch), or with less-accurate sprung-movement data, the system will not be able to accurately interpret the camera data. The system may not be able to determine well, for instance, whether a sensed change in angle between the sprung portion and the road surface is due to a change in the road surface or sprung-portion movement (e.g., roll and/or pitch).
The autonomous-driving-related functions improved by high-accuracy estimations of road angle and vehicle angle include control of brake and steering on angled roads—e.g., banked, pitched, etc. The information can be helpful especially when the vehicle is on a road that is banked and/or pitched, so the autonomous actions are tailored best to the road conditions and vehicle position.
As provided road and vehicle angles, e.g., road bank and vehicle roll angles, can be measured directly, such as by a dedicated optical sensor, or a dual-antenna GPS unit. And high cost of implementation is one shortcoming of these direct-measure approaches.
It is also challenging, and perhaps not even feasible, to measure road and vehicle angles, e.g., road bank and vehicle roll angles, using a standard inertial-movement unit (IMU) sensor set.
The present technology uses at least one additional sensor, beyond the motion sensors found commonly in most present-day vehicles. For estimating road bank and vehicle roll, the additional sensor(s) includes a roll-rate sensor. The additional sensor can be, or be a part of, a three-dimensional inertia-measuring device, such as a 3-axis IMU.
Some vehicles already include some type of roll-rate sensor. Some, for instance, include a roll-rate sensor for use in determining a propensity of the vehicle to roll over. These roll-rate sensors may be configured for their limited rolls, though, such as by having only an accuracy level sufficient for reliably identifying a potential rollover scenario, or by only measuring roll with more accuracy on after triggered by a determination that a threshold vehicle roll rate has been sensed.
The roll-rate sensor used in the present technology is in various embodiments a different roll-rate sensor or a different type of sensor. The roll-rate sensor used can be, for example, more accurate than the roll-rate sensors used commonly.
The technology also includes an algorithm using a virtual observer to process sensor data in estimating road and vehicle angle.
As provided, the present algorithm(s) is in some implementations embodied at least partially by computer code configured to cause a processor to perform any or all of the operations described herein. The code is stored on a storage device, or memory. Example computing structure is described further, below in connection with FIG. 8. Components used in the performing the functions of the present technology are at times referred to generically herein by terms such as system, or sub-system.
In one embodiment, the algorithm includes three (3) primary operations, each of which can include one or more sub-routines. The operations include (1) estimating roll rate and roll angle, (2) estimating road bank, and (3) tuning observer gain. The operations can be summarized as shown in FIG. 2, and are described further, below, in turn.
II. First Operation—Estimate Roll Rate and Roll Angle
As provided, embodiments of the present technology configured to estimate vehicle roll angle and road bank angle use an accurate roll-rate sensor. For the first operation, the system obtains data from the sensor for a present time.
As mentioned, while the present disclosure focuses on an overall goal of estimating accurately vehicle roll angle and road-bank angle, the teachings of the present technology can be extended to include estimating accurately vehicle pitch angle and road grade or slope angle. Or the technology can include accurate estimation of all four of vehicle roll and pitch angles, and road bank and grade angles. For embodiments configured to estimate vehicle pitch angle and road grade or slope angle, an accurate pitch-rate sensor is used in this first operation, and for embodiments in which all four angles are measured, accurate roll-rate and pitch-rate sensors are used in connection with the first operation.
The algorithm, embodied at least in part by computer-executable instructions, is configured to cause the system to use the measured roll rate to determine a roll estimate. The computing components of the present technology are mentioned above and described further below, including in connection with the schematic illustration of FIG. 8.
The algorithm also causes the system to use the measured roll rate to estimate a roll angle. Because of the effectiveness of this estimation, and assuming a high-accuracy roll-rate sensor, the estimated roll rate and the roll-rate measurement are at times very similar or even fully, substantially, or generally identical. The relationship is described further below in connection with the exemplifying data charts of the latter figures, FIGS. 5-7.
For situations in which the roll-rate sensor has more than nominal error, for reasons such as those described above, which may be temporary, the measured roll rate and the estimated roll rate may differ at least slightly. The present technology is configured so that, preferably, the estimated roll rate will be more accurate generally in these situations no matter how transient.
In one embodiment, the roll rate and roll angle are estimated using a Luenberger-type of observer and single degree-of-freedom (1-DOF) dynamics model. The observer and model can be represented by the following relationships:

(Jxx+Msh2){umlaut over (θ)}+Cθθ{dot over (θ)}+Kθθθ=Mshay   (Equation 1)

wherein:

Jxx is a roll moment of inertia of the vehicle 100;
Ms, indicated in the first figure, FIG. 1, by reference numeral 122, is the sprung mass, or the mass of the portion of the vehicle 100 above the suspension and the tires;
h, indicated in FIG. 1 by reference numeral 124, is a height of the center of gravity of the sprung portion of the vehicle measured from the roll center 120;
ë (double derivative of lower-case Roman numeral theta, or, theta^dot-dot) represents a roll acceleration, or the angular acceleration of the vehicle 100 in the roll direction—about the x, longitudinal axis of the vehicle;
Cθθ (or, C_sub_two lower-case Roman numeral thetas) represents a vehicle damping coefficient or constant, which may be pre-determined by a designer of maker of the system, such as in pre-manufacturing testing or simulations, to compensate for damping effects within the system, such as damping effects of the tires;
{dot over (θ)} (first derivative of lower-case Roman numeral theta) represents a roll velocity, or the angular velocity of the vehicle 100 in the roll direction—about the x, longitudinal axis of the vehicle;
Kθθ (or, K_sub_two lower-case thetas) represents a vehicle roll stiffness coefficient or constant, which also may be pre-determined by a designer of maker of the system, such as in pre-manufacturing testing or simulations, to compensate for a stiffness, or inverse of a vehicle spring characteristic;
θ (lower-case Roman numeral theta) represents the roll angle being estimated;
ay represents linear lateral acceleration;

{dot over (θ)}=q+L1(qmeas−q)  (Equation 2)

q is the roll rate being estimated;
L1 represents a first observer gain, which can be determined as described, or determined and tuned, as described further below in connection with the third operation;
qmeas represents measured roll rate;

{dot over (q)}={−Cθθ[q+L2(qmeas−q)]−Kθθθ+Mshay}Jxx−1   (Equation 3)

{dot over (q)} (or, first derivative of q, or, q^dot) represents the first derivative of the roll rate being estimated, or roll acceleration; and
L2 is a second observer gain, which, like the first gain, can be determined as described, or determined and tuned, as described further below in connection with the third operation—a separate, second, gain, different than the first observer gain, is in some embodiments used to accommodate a second state of the system.
III. Second Operation—Estimate Road Bank|FIG. 1
The second operation is described in connection with the figures, and more particularly the first figure. FIG. 1 illustrates schematically a vehicle on a banked road, and select variables including road and vehicle angles, according to an embodiment of the present disclosure.
The vehicle is indicated schematically by reference numeral 100 in the figure. The vehicle 100 includes a left tire 102 and a right tire 104.
The vehicle 100 also includes an axis 106 extending between the tires 102, 104. The axis 106 can generally correspond to an axle 106 of the vehicle 100.
In one embodiment, the tires 102, 104 represent front tires of the vehicle 100, and, in another, the rear tires.
In a contemplated embodiment, the illustrated tires represent an approximation of the position of the entire vehicle 100, such as by the left tire 102 representing an average of left front and left rear tire positions, and the same for the right.
With continued reference to FIG. 1, a roll-neutral, or no-roll, vertical center line of the vehicle 100, extending vertically in a vehicle frame when the vehicle has no roll, is indicated by reference 108. It should be appreciated that the no-roll vertical center line 108 is generally perpendicular to the vehicle axle 106. When conditions cause the vehicle 100 to roll, as may be the case while the vehicle is being slowed while being turned, or while the vehicle is driving on a banked road, such as the bank 110 of FIG. 1, the roll-neutral vertical center line of the vehicle remains the same, as shown in FIG. 1, remaining generally perpendicular to the axle 106.
The vehicle 100 is traveling on a road 110 having a bank in the example of FIG. 1. The amount of bank of the road 110 can be quantified as an angle 112 between the road surface and horizontal 114, or environmental-frame vertical. The bank angle 112 can be referred to by lower-case Roman numeral beta (β).
It will be appreciated that, with the road 110 to ground 114 angle being small beta (β) 112, the vertical center line 108 will form generally the same angle (β) at location 116 with a straight ground vertical line 118 (being perpendicular to the ground 114) based on basic geometric principles. There may be some losses or variations in the components between the road 110 and the vehicle 100, such as by the right tire deforming more than the right tire during the banking maneuver shown in FIG. 1, so that the second angle 116 would vary from the road-to-ground bank angle 112, the difference will generally be minimal with respect to the bank and vehicle roll angles being evaluated.
Further, the algorithm of the present technology, including the observer mentioned above and described further below, can be configured to, in tunings of its observer gain, can adjust to accommodate such variables for even better estimates of roll and bank angles.
FIG. 1 also calls out by reference numeral 120 a roll center of the vehicle 100. The point 120 creates a reference through which the environmental vertical 118 can be located.
As mentioned above, FIG. 1 also shows a sprung-mass point (Ms) by reference numeral 122. As also mentioned, the vehicle roll angle (θ) is an angle between a sprung portion of the vehicle 100 and the balance of the vehicle, the sprung portion being generally that portion connected above the suspension and the tires. The sprung-mass point (Ms) 122 is analogous to a center of gravity of the vehicle, except being specific to the sprung-mass portion of the vehicle 100 instead of the being for the overall vehicle.
As also shown in FIG. 1, the center of gravity 120 and the sprung-mass point 122 are separated by a height 124, or hc, wherein h represents height and c represents center of gravity. As with all names provided by way of example herein, other naming conventions can be used without departing from the scope of the present disclosure. A length of the line 124 can be referred to as length hc, or as length 124.
FIG. 1 further calls out, by reference numeral 126, an angle between the non-roll vehicle-frame vertical 108, described above, and the CG-sprung-mass line 124 (hc). The angle 126 represents the vehicle roll, being estimated, which is also referenced herein by lower-case Roman numeral theta (θ), such as above in the equation above.
From the figure, it will be appreciated that an angle 128 (or, δ) separating the mass-sprung height line 124 (hc) and environmental vertical 118 is a difference between the angle 126 (or, θ) and the angle 116, which angle 116 is generally equivalent to the bank angle (β) as described above. Or, δ=θ−β. The relationship can be used to estimate indirectly the road bank angle (β) 112, as described further below.
FIG. 1 also indicates gravity, acting on the sprung-mass point 122, by a downward-arrowed vector referenced by numeral 130. The vector 130 indicates, by its direction, the direction that the gravity is acting on the vehicle 100—downward, or negatively (−), in the environmental, or world, frame. It will be appreciated that with the gravity 130 acting vertically downward, it is acting parallel to the environmental vertical 118. The vector 130 also indicates, by its length, the amount of the gravity (e.g., 9.81 m/s2).
FIG. 1 also shows a vector representation of a lateral component of vehicle acceleration 132, or ay, which can be considered to act through the sprung-mass point 122, as shown in the figure, and can be perpendicular to the mass-sprung height hc. The lateral acceleration 132 (ay) in some embodiments includes centrifugal acceleration of the vehicle 100 and incorporates affects of any vehicle yaw motion.
FIG. 1 also shows, by reference numeral 134, a vector representing a lateral acceleration ay,s of the sprung-mass portion of the vehicle 100, or lateral mass-sprung acceleration. A lateral mass-sprung velocity vy,s can be viewed as a linear portion of the vehicle roll rate, the vehicle roll rate being an angular velocity. The lateral mass-sprung acceleration ay,s, which can be considered extending laterally perpendicular to environmental vertical 118, is thus a linear representation of the change in vehicle roll rate, the change in vehicle roll rate being an angular acceleration.
The vectors 130 (gravity, g), 132 (lateral acceleration, ay), and 134 (lateral mass-sprung acceleration ay,s) indicate graphically, by their respective lengths, amounts of the respective accelerations. The vectors 130, 132, and 134 also indicate graphically, by the respective directions shown in the figure, the directions that the accelerations g, ay, and ay,s are directed.
An angular difference between the vectors 132 (corresponding to acceleration ay) and 134 (corresponding to acceleration ay,s) is indicated by an angle 136.
FIG. 1 also shows a line 138 extending from an end of the gravity vector 130 parallel to the line 124 (hc).
From the geometrical relationships, it will be appreciated that each of the angles 136, 140 is equivalent to the angle 128 (δ).
With continued reference to the algorithm of the present technology, in the second operation, the system uses the these relationships, and the estimated roll rate and the estimated roll angle determined in the first operation, to estimate the road bank angle (β) 112.
In some embodiments, estimating the road bank angle (β) 112 is based also on other vehicle dynamics data, such as vehicle yaw rate (r), lateral velocity, longitudinal velocity, and/or lateral acceleration.
The vehicle lateral velocity and acceleration can be measured or estimated. The same applies to yaw rate (r).
The lateral velocity vx can be estimated, for example, in accordance with any of the embodiments disclosed in U.S. Pat. No. 8,086,367 (entitled, “Vehicle Lateral Velocity and Surface Friction Estimation Using Force Tables”) and U.S. Pat. No. 8,165,769 (entitled, “Multi-Factor Speed Estimation System and Method for Use”), which are incorporated herein by reference.
In one embodiment, the second operation, of estimating the road bank angle (β), is performed according to the following relationships:

ay,s=ay cos(φ−β)+g sin(φ−β)   (Equation 4)

wherein:

ay,s represents the mass-sprung lateral acceleration 134, described above; and
ay represents the lateral acceleration 134, described above;
θ (lower-case Roman numeral theta) represents the roll angle being estimated;
β (lower-case Roman numeral beta) represents the road bank angle 112 being estimated;

    
    
        g represents gravity, acting straight down as shown;

−ay={dot over (v)}y+rvx+O(β2)   (Equation 5)

wherein:

    
    


{dot over (v)}y (or, first derivative of vy, or, vy^dot) represents a first derivative of lateral velocity of the vehicle 100;
r represents a yaw rate, or first derivative of Roman numeral psi, or ψ^dot;
vx is longitudinal, or forward, x-direction, velocity;
O represents a high-order function, such as a second-order or higher function; and




  
    
      
        
          
            
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Related to the derivative of the lateral velocity {dot over (v)}y (or, first derivative of vy, or, vy^dot), it should be appreciated that all vehicle movement can be represented by at least longitudinal, or x-direction, velocity, vx, and lateral, or y-direction velocity, vy. If the vehicle is, by way of example, moving fully forward, the lateral velocity portion vy would be zero. The first derivative of the lateral velocity {dot over (v)}y (vy^dot) is the derivative of the lateral velocity vy, or the rate of change of the lateral velocity vy.
While the lateral acceleration 132 (ay) and the first derivative of lateral velocity {dot over (v)}y (vy^dot) may in many, and likely most, scenarios be the same or generally the same, the two variables have different definitions and can at times be at least slightly different. In any event, in embodiments using Equation 6 and 7, above, the lateral acceleration 132 (ay) cancels out between the two equations, and actually need not be measured or determined in the process.
The effect of the high-order function O is expected to be low, or only negligible, in most or all cases. For this reason, the function O is in some embodiments left out of the algorithm.
IV. Third Operation in the Context Of Overall Flow|FIG. 2
The third exemplary operation of the algorithm of the present technology is now described with reference to FIG. 2. As mentioned above, the figure illustrates an exemplary system flow 200 of operations. The flow 200 includes tuning of an observer gain using a tuning, or adaptation function.
The references in FIG. 2 can represent a variety of system flow features, including software modules, inputs thereto, outputs thereof, functions performed by the system, whether by modules or otherwise, and/or other, including as referenced further below.
Data indicating the measured roll rate described above, in connection with the first operation of the algorithm, is referenced by numeral 202. The roll rate can be measured by, for instance, a three-axis inertial-measuring device, such as a 3-axis IMU.
The roll rate measurement has a sign (+/−), or is modified to be signed or supplemented with a sign (+/−), as indicated in FIG. 2 by reference numeral 204.
The signed measurement is an input to roll observer 206. As mentioned above, the system can include as the observer 206, a Luenberger-type of observer.
As an aside, in control theory, an observer, or state observer, is a module that provides an estimate of a state of a given real plant using measurements of system inputs and outputs. In the present use, the real plant is the dynamic vehicle. Observers are useful in common situations in which all aspects of physical state of the system cannot be, for some reason (e.g., capability or cost), determined by direct measurement. Indirect effects of the internal state are estimated based on the system outputs, or system inputs and outputs.
The resulting representation, or model, of the plant, i.e., vehicle, can be adjusted in an ongoing manner, using successive measured values of input and outputs in iterations of operation, in effort to focus or converge the representation to the actual state of the vehicle being evaluated. For the Luenberger observer, adjustments to an initial model are made, include (i) subtracting an output of the observer from observed output of the vehicle, (ii) then multiplying the result by a factor, such as by a matrix, and (iii) then adding the result to equations for the state of the observer to produce the Luenberger observer.
With continued reference to FIG. 2, another input to the roll observer 206, in addition to the roll-rate measurement 202, and for iterations of the flow 200 after a first iteration, is an estimated roll rate 208 resulting from a last iteration of the flow 200. The return of estimated roll rate 208 is illustrated by return path 210.
In some embodiments, the process includes a sub-routine of tuning, or adapting, a gain of the observer. The sub-routine or module, indicated in FIG. 2 by reference numeral 212, receives, as input from an estimation sub-routine or module 214 (to be described further below), output of a last iteration of the flow 200, as illustrated by a corresponding illustrated path 216. Resulting output of the tuning sub-routine or module 212 is provided to the observer 206, as shown schematically by a corresponding path 218.
The tuning can include performance of an optimization tool toward achieving optimal gains for all possible scenarios. While other optimization tools can be used, in one embodiment the tool is an iSight optimization software, available from Dassault Systemes Americas Corp., of Waltham, Mass.
The tuning, or adapting, sub-routine or module 212, and related input/output paths 216, 218, are in some embodiments, performed preferably prior to the vehicle being used by an ultimate customer. They can be performed, for instance, in a manufacturing or pre-manufacturing phase. For example, they can be performed in pre-manufacturing on-road and/or simulation testing of a certain type of vehicle. The algorithm (e.g., code) programmed thereafter into the same-kind vehicles, prior to or in their manufacturing, can include the resulting observer gain(s).
In embodiments in which the gain is pre-tuned for a vehicle, such as described here, the tuning sub-routine or module 212, and related input/output paths 216, 218, can be absent from balance of the flow 200 performed at the vehicle 100 in vehicle operation to estimate vehicle roll rate and vehicle roll. The sub-routine 212, and related input/output paths 216, 218, can, e.g., be considered unneeded because the gain has already been optimized for the vehicle. The flow 200 also operates more efficiently without the sub-routine 212, and related input/output paths 216, 218, due, e.g., to savings of processing resources and time that would otherwise be used.
In some embodiments, the vehicle instructions are programmed with the algorithm such that the tuning 212 is performed during customer operation of the vehicle 100.
An output of the tuning can include one or more gains, such as the gains L1, L2, mentioned above. In some embodiments, the instructions are configured to cause the system to organize, in an organizing structure, multiple determined gains, each in connection with a corresponding condition. The gains may be organized, in an organizing structure such as a table, matrix, list, etc., relating each gain to a condition. For estimating vehicle roll rate, roll angle, and road-bank angle, the processor obtains using, or from, the observer, a specific gain, of the multiple gains pre-populated into the organizing structure, corresponding to a present condition of the vehicle. The condition, for instance, may relate to vehicle dynamics, such as roll rates, lateral velocity, lateral acceleration, the like, and/or other.
Output of the roll observer 206 is provided to the estimation sub-routine, or module, 214, which can also be referred to as, e.g., an estimation module, an estimator function, an estimator module, a bank-angle estimator, angle estimator, etc. As also shown, another input to the angle estimator 214 is lateral acceleration 220. The lateral acceleration 220 is in some embodiments a measured value.
The angle estimator 214, using the input from the observer 206 and the lateral acceleration 220, outputs estimations for the vehicle roll angle 222, for the road bank angle 224, and for the vehicle roll rate 208.
As provided, the angle estimator 214 also outputs, along a path 216, data used by the afore-mentioned gain-adaptation function 214. As referenced above, this data includes estimated bank angle as well as roll angle.
V. FIG. 3
First Example Bank and Roll Estimation Data
FIG. 3 is a graph 300 showing first example bank and roll estimation data.
The graph 300 includes a y-axis 302 incremented in degrees and an x-axis 304 incremented in seconds. A first data line 306 shows road bank angle estimated according to the present technology, and how it changes with time, from left to right in the chart. A second data line 308 shows vehicle roll angle estimated according to the present technology, and how it changes with time.
Data for the graph 300 of FIG. 3 was obtained in private testing of the present technology on a first road surface. The road includes slight banking that the vehicle 100 encounters between about the 90-second and the 125-second marks.
The data 306, 308 also shows that the estimated roll and estimated bank angles are generally about nil, showing mostly system noise, until the bank is encountered around the 90-second mark, and that the two estimates change in like manner until this time.
Once the bank is encountered, the estimated bank line 306 dips significantly, to about −12%, indicating that the bank is about 12% in one direction (e.g., banking raising the right wheel 104 higher than the left wheel 102, depending on the signing convention used). During the banking period (about 90 s-125 s), the estimated vehicle roll 308 departs from changing like the bank estimation, and is slightly positive, reaching a maximum chart-value of about three degrees.
VI. FIG. 4
Second Example Bank and Roll Estimation Data
FIG. 4 is a graph 400 showing second example bank and roll estimation data.
As with the graph 300 of FIG. 3, the graph 400 includes a y-axis 402 incremented in degrees and an x-axis 404 incremented in seconds. A first data line 406 shows road bank angle estimated according to the present technology, and how it changes with time. A second data line 408 shows vehicle roll angle estimated according to the present technology, and how it changes with time.
Data for the graph 400 of FIG. 4 was obtained in private testing of the present technology on a second road surface. The road includes slight banking that the vehicle 100 encounters between about the 85-second and the 100-second marks.
The data 406, 408 again shows that the estimated roll and estimated bank angles are generally about nil, showing mostly system noise, until the bank is encountered around the 85-second mark, and that the two estimates vary in like manner until this time.
Once the bank is encountered, the estimated bank line 406 dips significantly, to about −15%, indicating that the bank is about 15% in one direction, depending on the signing convention used. During the banking period (about 85 s-100 s), the estimated vehicle roll 408 departs from changing like the bank estimation, and is slightly positive, reaching a maximum chart-value of about two or three degrees.
VII. FIG. 5
First Example Roll Estimation vs. Measurement Data
FIG. 5 is a graph 500 showing first example vehicle roll estimation data as compared to measured vehicle roll data.
As with the other graphs, the graph 500 includes a y-axis 502 incremented in degrees and an x-axis 504 incremented in seconds. A first data line 506 shows measured vehicle roll angle, and how it changes with time. A second data line 508 shows vehicle roll angle estimated, using an observer as described herein, according to the present technology, and how it changes with time.
Data for the graph 500 of FIG. 5 was obtained in private testing of the present technology on a third road surface. The third road did not include any significant banking.
The data 506, 508 shows that the measured vehicle roll 506 and the estimated vehicle roll 508 generally trace each other, varying in step together with similar values. The phenomena confirm the accuracy of both the measured and the estimated values, e.g., accuracy of the observer and its tuned, or adapted, gain.
VIII. FIG. 6
Second Example Roll Estimation vs. Measurement Data
FIG. 6 is a graph 600 showing second example vehicle roll estimation data as compared to measured vehicle roll data.
As with the other graphs, the graph 600 includes a y-axis 602 incremented in degrees and an x-axis 604 incremented in seconds. A first data line 606 shows measured vehicle roll angle, and how it changes with time. A second data line 608 shows vehicle roll angle as estimated, using an observer as described herein, according to the present technology, and how it changes with time.
Data for the graph 600 of FIG. 6 was obtained in private testing of the present technology on a fourth road surface. The fourth road did not include any significant banking.
The data 606, 608 shows that the measured vehicle roll 606 and the estimated vehicle roll 608 generally trace each other, varying in step together with similar values. The phenomena again confirm the accuracy of both the measured and the estimated values, e.g., accuracy of the observer and its tuned, or adapted, gain.
IX. FIG. 7
Third Example Roll Estimation vs. Measured Data
FIG. 7 is a graph 700 showing third example vehicle roll estimation data as compared to measured vehicle roll data.
As with the other graphs, the graph 700 includes a y-axis 702 incremented in degrees and an x-axis 704 incremented in seconds. A first data line 706 shows measured vehicle roll angle, and how it changes with time. A second data line 708 shows vehicle roll angle as estimated, using an observer as described herein, according to the present technology, and how it changes with time.
Data for the graph 700 of FIG. 7 was obtained in private testing of the present technology on a fifth road surface. The fifth road did not include any significant banking.
The data 706, 708 shows that the measured vehicle roll 706 and the estimated vehicle roll 708 generally trace each other, varying in step together with similar values. The phenomena again confirms the accuracy of both the measured and the estimated values, e.g., accuracy of the observer and its tuned, or adapted, gain.
X. FIG. 8
Example Computing System
FIG. 8 illustrates schematically a vehicle 800, such as the vehicle 100 described above, including an exemplary computing system 802 for use in performing functions of the present technology.
The system 802 includes a memory, or computer-readable medium 804, such as volatile medium, non-volatile medium, removable medium, and non-removable medium.
The term computer-readable media and variants thereof, as used in the specification and claims, refer to tangible storage media. The media can be a device, and can be non-transitory.
In some embodiments, the storage media includes volatile and/or non-volatile, removable, and/or non-removable media, such as, for example, random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), solid state memory or other memory technology, CD ROM, DVD, BLU-RAY, or other optical disk storage, magnetic tape, magnetic disk storage or other magnetic storage devices.
The computing system 802 also includes a computer processor 806 connected or connectable to the computer-readable medium 804 by way of a communication link 808, such as a computer bus.
The computer-readable medium 804 includes computer-executable instructions 810. The computer-executable instructions 810 are executable by the computer processor 806 to cause the processor, and thus the computing system 802, to perform all or any combination of the functions described in the present disclosure, including those described above.
The computer-executable instructions 810 can be arranged in one or more software modules, or engines. The modules can be referred to by the operations or operations that they cause the computer processor 806 to perform. For instance, a module including instructions that, when executed by the processor 806, cause the processor to perform an operation of estimating vehicle roll angle can be referred to as a roll-estimation module, a roll-estimation engine, a roll estimator, or the like.
Similarly, a module causing the computer processor to perform an operation of tuning observer gains can be referred to as an observer-gain tuner, an observer-gain-tuner module, a gain tuner, a gain-tuning module, a gain-tuning engine, or the like.
The term software module, or variants thereof, is used expansively herein to include routines, program modules, programs, components, data structures, algorithms, and the like. Software modules can be implemented on various system configurations, including servers, network systems, single-processor or multiprocessor systems, minicomputers, mainframe computers, personal computers, hand-held computing devices, mobile devices, microprocessor-based, programmable consumer electronics, combinations thereof, and the like.
The computer processor 806 is also connected or connectable to at least one interface 812 for facilitating communications, between the computing system 802 and local components 814, and between the computing system 802 and remote components 816.
For communicating with the local components 814, the interface 812 can include one or both of wired connections and wireless components—e.g., transceiver, transmitter, and/or receiver.
Example local components include the measurement components described herein, including a three-axis IMU, and any local instrumentation that may be connected at least intermittently at times to the vehicle, e.g., into the interface 812 directly.
For communicating with the remote components 816, the interface 812 includes one or both of a short-range transceiver (or transmitter and/or receiver) and a long-range transceiver (or transmitter and/or receiver).
The remote components 816 can include databases, servers, other processors, other storage mediums, and/or other computing devices.
Although shown as being a part of the computer system 802, completely, the interface 812, or any aspect(s) thereof, can be partially or completely a part of the system 802. The interface 812, or any aspect(s) thereof, can be partially or completely external to and connected or connectable to the computing system 802.
XI. Methods of the Present Technology
Figures illustrating the processes of the present technology are not provided with the present provisional application beyond that provided herewith. Additional flow charts consistent with the teachings herein are considered supported by the present technology and so inherently provided herewith.
The methods include the functions described herein, according to embodiments of the present disclosure. It should be understood that the steps of the methods are not necessarily presented in any particular order and that performance of some or all the steps in an alternative order is possible and is contemplated.
The steps have been presented in the demonstrated order for ease of description and illustration. Steps can be added, omitted and/or performed simultaneously without departing from the scope of the appended claims. It should also be understood that the methods can be ended at any time.
In certain embodiments, some or all steps of this process, and/or substantially equivalent steps are performed by a processor, e.g., computer processor, executing computer-executable instructions stored or included on a computer-readable medium, such as the memory 804 of the system 802 described above.
XII. Conclusion
Various embodiments of the present disclosure are disclosed herein. The disclosed embodiments are merely examples that may be embodied in various and alternative forms, and combinations thereof.
The law does not require and it is economically prohibitive to illustrate and teach every possible embodiment of the present technology. Hence, the above-described embodiments are merely exemplary illustrations of implementations set forth for a clear understanding of the principles of the disclosure.
Variations, modifications, and combinations may be made to the above-described embodiments without departing from the scope of the claims. All such variations, modifications, and combinations are included herein by the scope of this disclosure and the following claims.

## Claims

1. A system, for use at a vehicle to estimate vehicle roll angle and a road bank angle, comprising:
a sensor configured to measure vehicle roll rate;
a processor; and
a non-transitory computer-readable medium comprising computer-executable instructions that, when executed by the processor, cause the processor to perform operations comprising:
estimating, using a virtual observer and the vehicle roll rate measured by the sensor, a vehicle roll rate, yielding an estimated vehicle roll rate;
estimating, using the virtual observer and the vehicle roll rate measured by the sensor, the vehicle roll angle, yielding an estimated vehicle roll angle; and
estimating, based on the estimated vehicle roll rate and the estimated vehicle roll angle, the road bank angle;

wherein:
the instructions include the virtual observer, including an observer gain; and
the estimated vehicle roll rate is more accurate than the vehicle roll rate measured due at least in part to use of the virtual observer and the observer gain.

2. The system of claim 1, wherein the sensor is, or is part of a three-axis inertial-measurement unit.

3. The system of claim 1, wherein the vehicle roll rate measured differs from the estimated vehicle roll rate.

4. The system of claim 1, wherein:
the operation of estimating the estimated vehicle roll rate comprises estimating the estimated vehicle roll rate using the vehicle roll rate measured and the virtual observer including a Luenberger observer, and a one-degree-of-freedom model; and
the operation of estimating the vehicle roll angle comprises estimating the vehicle roll angle using the vehicle roll rate measured and the virtual observer being the Luenberger observer, and the one-degree-of-freedom model.

5. The system of claim 1, wherein the operations further include tuning at least one observer gain of the virtual observer.

6. The system of claim 5, wherein the tuning includes using an optimization tool toward achieving optimal gains for multiple scenarios.

7. The system of claim 5, wherein results from the tuning are incorporated into an organizing structure relating each of multiple observer gains with a distinct vehicle-related condition.

8. The system of claim 7, wherein the organizing structure includes a table.

9. The system of claim 5, wherein:
the operations are part of a process;
the tuning is performed in a tuning sub-routine; and
a first input to the tuning sub-routine is the vehicle roll rate measured, and a second input to the tuning sub-routine is the estimated vehicle roll rate from a last iteration of the process.

10. The system of claim 9, wherein:
an output of the virtual observer is provided to an estimator sub-routine, which estimates the vehicle roll angle, vehicle roll rate, and road bank angle, and an input to the estimator sub-routine is a lateral acceleration; and
the lateral acceleration is a measured value.

11. The system of claim 1, wherein an observer gain of the virtual observer is pre-determined, including by tuning before the system is used by a customer.

12. The system of claim 1, wherein the vehicle roll rate measured is measured by a three-axis inertial-measuring device.

13. A system, for use at a vehicle to estimate vehicle roll angle and a road bank angle, comprising:
a sensor configured to measure vehicle roll rate;
a processor; and
a non-transitory computer-readable medium comprising computer-executable instructions that, when executed by the processor, cause the processor to perform operations comprising:
estimating, using a virtual observer and the vehicle roll rate measured by the sensor, a vehicle roll rate, yielding an estimated vehicle roll rate;
estimating, using the virtual observer and the vehicle roll rate measured, the vehicle roll angle, yielding an estimated vehicle roll angle; and
estimating, based on the estimated vehicle roll rate and the estimated vehicle roll angle, the road bank angle; and
wherein:
the operation of estimating the estimated vehicle roll rate comprises estimating the estimated vehicle roll rate using the vehicle roll rate measured and the virtual observer including a Luenberger observer, and a one-degree-of-freedom model; and
the operation of estimating the vehicle roll angle comprises estimating the vehicle roll angle using the vehicle roll rate measured and the virtual observer being the Luenberger observer, and the one-degree-of-freedom model.

14. The system of claim 13, wherein the virtual observer and model can be represented by relationships including:


(Jxx+Msh2){umlaut over (θ)}+Cθθ{dot over (θ)}+Kθθθ=Mshay  (eqn. 1);

wherein:
Jxx is a roll moment of inertia of the vehicle;
Ms is a sprung mass;
h is a height of the center of gravity of the sprung portion of the vehicle measured from a roll center;
ë (or, second derivative of theta, or theta^dot-dot) represents a roll acceleration;
Cθθ represents a vehicle damping coefficient;
{dot over (θ)} (or, first derivative of theta, or, θ^dot) represents a roll velocity;
Kθθ represents a vehicle roll stiffness coefficient;
θ represents the roll angle being estimated;
ay represents linear lateral acceleration;


{dot over (θ)}=q+L1(qmeas−q)  (eqn. 2);


q is the roll rate being estimated;
L1 represents a first observer gain;
qmeas represents measured roll rate;


{dot over (q)}={−Cθθ[q+L2(qmeas−q)]−Kθθθ+Mshay}Jxx−1  (eqn. 3);


{dot over (q)} (or, first derivative of q, or, q^dot) represents the first derivative of the roll rate being estimated; and
L2 is a second observer gain.

15. The system of claim 14, wherein the operation of estimating the road bank angle (β), comprises:


ay,s=ay cos(φ−β)+g sin(φ−β)  (eqn. 4);

wherein:
ay,s represents a mass-sprung lateral acceleration; and
ay represents the lateral acceleration;
θ represents the roll angle being estimated;
β represents the road bank angle;
g represents gravity;


−ay={dot over (v)}y+rvx+O(β2)  (eqn. 5);



wherein:
{dot over (v)}y (Vy^dot) represents a first derivative of lateral velocity of the vehicle 100;
r represents a yaw rate ({dot over (ψ)}, or, first derivative of Roman numeral psi, ψ^dot);
vx is longitudinal, or forward, x-direction, velocity;
O represents a high-order function; and






  
    
      
        
          
            
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16. The system of claim 13, wherein an observer gain of the virtual observer is pre-determined, including by tuning before the system is used by a customer.

17. A non-transitory computer-readable storage system, for use at a vehicle to estimate vehicle roll angle and a road bank angle, comprising:
a roll-rate estimator module that, when executed by a processor, estimates, using a virtual observer and the vehicle roll rate measured by the sensor, a vehicle roll rate, yielding an estimated vehicle roll rate;
a roll-angle estimator module that, when executed by the processor, estimates, using the virtual observer and the vehicle roll rate measured, the vehicle roll angle, yielding an estimated vehicle roll angle;
a road-bank-angle estimator module that, when executed by the processor, estimates, based on the estimated vehicle roll rate and the estimated vehicle roll angle, the road bank angle; and
wherein:
instructions of the storage system include the virtual observer including an observer gain; and
the vehicle roll rate estimated is more accurate than the vehicle roll rate measured due at least in part to use of the virtual observer and its gain.

18. The non-transitory computer-readable storage system of claim 17, wherein the virtual observer includes the observer gain, and the storage system further comprises a tuning module that, when executed by the processor, tunes the observer gain.

19. The system of claim 18, wherein tuning the observer gain includes using an optimization tool toward achieving optimal gains for multiple scenarios.

20. The system of claim 18, wherein results of tuning the observer gain are incorporated into an organizing structure relating each of multiple observer gains with a distinct vehicle-related condition.