CN105160189B - A kind of wheel slip rate and lateral deviation angle measuring method based on rut information - Google Patents
A kind of wheel slip rate and lateral deviation angle measuring method based on rut information Download PDFInfo
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Abstract
A kind of wheel slip rate and lateral deviation angle measuring method based on rut information, it is related to wheel slip rate and the measuring method of side drift angle, more particularly to a kind of wheel slip rate and lateral deviation angle measuring method based on rut information.The present invention is to solve existing measurement celestial body detecting vehicle wheel slip rate and the method for side drift angle, there is External force interference and indeterminable problem and visual odometry method the problem of can not directly observing single wheel slip in follower method.The inventive method is carried out by following steps：First, rut and wheel slip rate and the relation of side drift angle are determined；2nd, tyre slip angle measurement model is established；3rd, wheel slip rate measurement model is established.The present invention solves the problems, such as that follower method has External force interference and indeterminable problem and visual odometry method can not directly observe single wheel slip, has the advantages that speed is fast, precision is high, practical and widely applicable.The present invention is applied to celestial body detecting field.
Description
Technical Field
The invention relates to a method for measuring wheel slip rate and a wheel slip angle, in particular to a method for measuring wheel slip rate and a wheel slip angle based on rut information.
Background
Since the last 90 s, the united states launched successively Sojouner ("songna"), spirit ("courage"), and Opportunity ("Opportunity"), and the world aerospace world has raised the hot tide of using a star probe vehicle for star detection. The Curiosity ("Curiosity") Mars vehicle in the MSL (Mars Science Lab) mission in the United states has become more of a focus of people in Mars exploration activities. The moon exploration project of 'Chang' in China predicts that the moon rover is launched in 2013 and explores the moon. The complex unknown extraterrestrial environment presents new challenges for the development of mobile robotics.
When the planet detection vehicle works in a soft and rugged foreign planet environment, the wheel slip phenomenon can occur. The degree of wheel slip is described by the slip rate. Slip is defined as follows:
s is the wheel slip, v is the actual forward speed of the wheel, r is the wheel radius, ω is the wheel rotational speed, and r ω is the theoretical peripheral speed. When s is greater than 0, the wheel is in a slip state, and the advancing linear speed of the wheel is less than the peripheral speed; when s =0, the wheel is in a pure rolling state, and the advancing linear speed of the wheel is equal to the peripheral speed; when s is less than 0, the wheel is in a slip state, and the advancing linear velocity is greater than the peripheral velocity.
In general, the planet cart operates on a soft, rugged outer planet surface. The movement of the planet wheel in soft and rugged terrain is usually accompanied by skidding, and the skidding mode mainly comprises longitudinal skidding and lateral skidding. When the wheel of the planet vehicle rolls on soft soil, the wheel and the soil generate shearing and damaging effects to generate longitudinal slip. When the road surface is rough, the gravity of the vehicle body generates a lateral component along the axial direction of the vehicle body in the direction of orientation. Under the action of the transverse component, the planet vehicle wheels generate transverse slip, namely sideslip. The phenomenon of the side slip of the planet wheel is particularly obvious when the planet wheel traverses a slope.
The index for evaluating the sideslip state of the planet probe vehicle is a wheel slip angle, and the slip angle is defined as follows:
wherein beta is s Is the slip angle of the wheel and represents the angle between the tangential linear velocity of the wheel and the actual speed of travel, v x Is the tangential linear velocity of the wheel, v is the actual speed of travel of the wheel, β s Is in the range of 0 to 90 deg.
In 2005, the Mars train "opportunity number" was sunk in soft sand soil of Mars. When the opportunity number sinks, an important phenomenon is that the wheels slip seriously and the slip rate is overlarge. Through accurate slip rate detection, early warning information can be sent for the planet vehicle sinking, so that the vehicle sinking is avoided.
The sliding of the planet detection vehicle wastes a large amount of energy, most planet detection vehicles rely on solar energy for power supply, and the energy generated in unit time is limited, so the control of the sliding rate is also a problem to be considered for the planet detection task. Accurate detection of slip rate is a necessary prerequisite for controlling slip rate. The slip rate information is used as feedback information and transmitted to a control system of the planet detection vehicle, and the control system is a necessary premise for improving the sinking prevention and mobility performance of the planet detection vehicle. The automatic detection of the wheel slip rate information of the planet probe vehicle is realized, and the automatic detection has important significance for the optimal control of the planet probe vehicle.
The slip rate measurement is always a difficult problem, the slip rate of the planet detection vehicle is measured by using the driven wheel, the method is simple, but the driven wheel can be contacted with the ground and can interfere the stress condition of the planet detection vehicle.
Nister first proposed measuring slip rate in 2004 using a visual odometer method. The method for detecting the slip rate by using the visual odometer is a non-contact measuring method, and does not introduce the acting force between a probe vehicle and soil. Further studies were performed on the visual odometer of the planet probe car by Yang Cheng et al of JPL (Jet Propulsion Laboratory). The vision odometer uses a telecentric camera to obtain a picture of relative movement of the vehicle body and the ground, and the linear speed of the whole vehicle is detected by comparing the difference of the two pictures. And indirectly estimating the slip rate of each wheel by using the linear speed of the whole vehicle and the angular speed of each wheel. But this method does not allow direct observation of single wheel slip.
Disclosure of Invention
The invention provides a wheel slip rate and side slip angle measuring method based on rut information, aiming at solving the problems that the conventional method for measuring the wheel slip rate and the side slip angle of a star-ball probe vehicle has inaccurate measurement due to external force interference in a passive wheel method and the problem that the single wheel slip cannot be directly observed in a visual odometer method.
The theoretical basis of the invention is as follows:
and (3) rut forming process:
the rut is mainly formed by the interaction process of the wheel pricks and the soil and can be divided into three sections, namely a section where the wheel pricks enter the soil, a section where the wheel pricks slide in the soil and a section where the wheel pricks leave the soil (see figure 2). Under the influence of sideslip, the wheel ruts in the entry section, the slip section and the exit section.
The entering section is from the top of the wheel thorn contacting the soil to the whole wheel thorn entering the soil. In the entry phase, the direction of generation of the ruts is along the direction of the speed of the wheel-stick.
The slipping phase of the wheel thorn in the soil is from the time the wheel thorn completely enters the soil to the time the wheel thorn is about to slip out of the soil. The time of the soil entry and soil separation process is very short compared to the time required for the slip phase, and can be considered as a transient process, which can be ignored. In the slip process, the wheel spines do slip movement to generate a shearing damage effect on soil, strip-shaped pits can be cut in the soil at the edges of the wheel spines, the soil can be rolled by the wheel hubs, and track textures in the slip stage are formed.
The exit phase refers to the beginning of the sprint about to leave the soil until the sprint is completely removed from the soil. Rutting occurs during the exit phase primarily because the wheel stick, when it leaves the soil, will carry a portion of the soil away from the soil surface, which will slide back down to the ground as the wheels roll. During the exit phase, the rut shape generated is related to the wheel spur shape.
The invention adopts straight-through wheel thorns, and the track shape of the leaving section is a columnar deep pit similar to a triangular prism.
Rut construction:
under the action of longitudinal and lateral slip-and-turn coupling, the wheel ruts are divided into a rut contour line and a wheel rolling area (see figure 1). In the process of separating the soil, the wheel pricks can shovel part of the soil (residual soil on the wheel pricks) back off the ground, and the formed area is a wheel prick shearing area. The area formed by the hub rolling is the hub rolling area. The wheel thorn shearing area and the wheel hub rolling area form a wheel rolling area. The boundary between the wheel crush region and the wheel non-crush region is called the rut contour. A complete rut consists of two rut contours and a wheel crush area. The adjacent wheel spine shearing area and the wheel hub rolling area form a rutting unit.
A wheel slip rate and slip angle measuring method based on rut information comprises the following steps:
1. determining the relationship between the ruts and the wheel slip rate and the slip angle:
the advancing distance of the wheel is reduced along with the increase of the slip ratio, and the distance between the rut units is correspondingly reduced, so that the slip ratio of the wheel is determined according to the distance between the rut units;
the larger the slip angle of the wheel is, the smaller the included angle between the track leaving section and the advancing direction is, so that the slip angle of the wheel is determined according to the width of the leaving section of the track unit and the length of the leaving section of the track unit;
2. establishing a wheel cornering angle measurement model:
obtaining a clear rut picture by a technical means, dividing the picture according to a rut analysis method, decomposing a rut leaving section in the picture in a horizontal plane to obtain the length and the width of the rut leaving section (see figure 4), and dividing the two values to obtain the slip angle of the wheel;
wherein: beta is a beta s Is the slip angle, W, of the wheel 1 Width of leaving segment of rut unit, I 1 The length of a leaving segment of the rut unit;
3. establishing a wheel slip rate measurement model:
obtaining the distance between every two rut units by measuring the rut pictures; using the definition formula of the slip ratio and the beta obtained in the second step s The slip rate of the wheel along the direction of the wheel can be obtained;
wherein s is x For the slip ratio of the wheel in the direction of wheel orientation,. DELTA.x p Is the distance between rut units, n is the number of wheel spines, beta s Is the slip angle of the wheel and r is the wheel radius.
The invention has the following beneficial effects:
1. the wheel slip rate and the slip angle are accurately calculated through the rutting information, the problems that the prior art is inaccurate in measurement due to external force interference in a driven wheel method and the single wheel slip cannot be directly observed through a visual odometry method are solved, and the wheel slip rate and the wheel slip angle measuring method have the advantages of being high in speed, high in precision, strong in practicability and the like.
2. The method has wide application range, and can be used for calculating the wheel slip rate and the slip angle of the wheel no matter which field is applied to as long as the wheel type vehicle can generate rutting marks.
Drawings
FIG. 1 is a schematic diagram illustrating the segmentation of longitudinal slip and lateral slip coupled motion regions;
FIG. 2 is a schematic view of a longitudinal slip and lateral slip coupled moving rut configuration;
FIG. 3 is a schematic view of the movement of the wheel-stabs in the soil;
FIG. 4 is a schematic view of a rut unit configuration;
FIG. 5 is a schematic view of a rut model;
Detailed Description
In order to make the aforementioned objects, features and advantages of the present invention more comprehensible, the present invention is described in further detail with reference to fig. 1 to 5 and the following detailed description.
In a first embodiment, a wheel slip ratio and slip angle measurement method based on rut information according to this embodiment includes the following steps:
1. determining rut versus wheel slip and slip angle:
the width of the track unit is equal to the distance between two adjacent shearing areas, and the distance is delta x p (see FIG. 2). When the wheel rolls for a circle, each wheel thorn can have a shearing action with the soil. A rut unit is created when the wheel stick is removed from the soil. That is, the number of wheel spines is n, and when the wheel rolls on the soil for a circle, n tracks are generated, so that the advancing distance of the wheel is reduced along with the increase of the slip rate, and the distance delta x between track units p And is correspondingly reduced. The wheel slip rate can be determined according to the rut unit spacing.
When the planet vehicle generates lateral slip, the central linear velocity v of the wheel can be decomposed into a linear velocity v along the direction of the wheel x And linear velocity v in the direction of wheel sideslip y (see FIG. 1). v. of x And v y Are orthogonal. The wheels are oriented v due to the presence of lateral slip x The direction has a slip angle beta with the linear velocity v direction of the wheel s . The larger the side slip angle of the wheel is, the smaller the included angle between the rutting leaving section and the advancing direction is, so that the rutting unit can leave the section according to the width W of the rutting unit 1 And length of leaving segment of track unit I 1 The slip angle of the wheel is determined (see fig. 4).
2. Establishing a wheel cornering angle measurement model:
the wheel runs in soft soil, a part of the wheel is sunk into the soil, the section of the soil and the section of the part of the wheel sunk into the soil are defined as a sunk section, and the width of the sunk section is the same as the width W of the wheel.
At time 1 the wheel stick starts to enter the soil, leaving the outermost point a' of the rut profile in the soil at the wheel stick edge. The wheel spine movement speed is the sum of the wheel centerline speed v and the wheel rotation linear speed ω r. Elapsed time t s At time 2, the wheel pricks out of the soil. l v A displacement vector generated for the wheel centerline velocity v from time 1 to time 2 (see fig. 5); l ωr The displacement vector generated from time 1 to time 2 for the speed ω r generated on the wheel stick for the wheel rotation. l. the v And l ωr Sum vector l of vp For the displacement vector of the spur from time 1 to time 2, vector l vp The sliding section of the rut, i.e. section a' E in fig. 5 (rut unit sliding section center line), is generated. The wheel pricks produce a rut centerline EB' at the separation section. From the geometric relationship in fig. 5, it can be derived:
β s ＝90°-θ 1 ， (3)
the wheel slip angle can be estimated by measuring the angle between the rut contour and the rut exit segment. The projection of B' E in the vertical direction of v (i.e., the width of the leaving segment of the wheel) is W 1 ＝HG＝Wsinθ 1 . Projection of B' E in v direction (track exit segment length) is I 1 ＝B’I＝Wcosθ 1 . The slip angle is then:
3. establishing a wheel slip rate measurement model:
the slip ratio definition in equation (1) does not consider the case where the wheels slip, and when the wheels slip is considered, the slip ratio of the wheels is defined as the direction v in which the wheels face x The slip rate of the direction. The following:
γ L the angle between two adjacent wheel spines is shown, if the wheel has n wheel spines, then there ist L Indicating the angle of rotation gamma of the wheel L The time required. At t L In time, the wheel rotates by the following angle:
multiplying the numerator and denominator of the formula (5) by t L Then, there are:
thus obtaining
The distance between two adjacent wheel spine traces (equal to the distance between the rut units) delta x p Equal to the actual forward linear velocity v and t of the wheel L The product of (a):
△x p ＝vt L (9)
the finally obtained wheel slip rate is as follows:
in equation (10), the number of wheel lugs n and the wheel radius r are known constants, i.e., only θ is measured from the rut 1 And width of rut unit delta x p Or directly evaluating cos beta with known slip angle s The slip rate s of the wheel along the direction of the wheel can be obtained x 。
The invention has the following beneficial effects:
1. the wheel slip rate and the slip angle are accurately calculated through the rut information, the problems that the prior art is inaccurate in measurement due to external force interference in a driven wheel method and a single wheel cannot be directly observed through a visual odometry method are solved, and the wheel slip rate and the wheel slip angle calculation method have the advantages of being high in speed, high in precision, strong in practicability and the like.
2. The method has wide application range, and can be used for calculating the wheel slip rate and the slip angle of the wheel no matter which field is applied to as long as the wheel type vehicle can generate rutting marks.
In a second embodiment, the present embodiment is further described with respect to the first embodiment, in which the wheel in the first step is a straight-through type wheel spur, in which the wheel slip and the wheel slip are measured based on rut information.
Claims (2)
1. A wheel slip rate and slip angle measuring method based on track information is characterized by comprising the following steps:
1. determining rut versus wheel slip and slip angle:
the advancing distance of the wheel is reduced along with the increase of the slip rate, and the distance between the rutting units is correspondingly reduced, so that the slip rate of the wheel is determined according to the distance between the rutting units;
the larger the side drift angle of the wheel is, the smaller the included angle between the rut leaving section and the advancing direction is, so that the side drift angle of the wheel is determined according to the leaving section width of the rut unit and the leaving section length of the rut unit;
2. establishing a wheel cornering angle measurement model:
dividing the rut picture according to a rut analysis method, decomposing the rut leaving section in the rut leaving picture in a horizontal plane to obtain the length and the width of the rut leaving section, and dividing the two values to obtain the slip angle of the wheel;
wherein: beta is a s Is the slip angle, W, of the wheel 1 Width of the leaving segment of the rut unit, I 1 The length of a leaving segment of the rut unit;
3. establishing a wheel slip rate measurement model:
obtaining the distance between every two rut units by measuring the rut pictures; beta obtained by using a definition formula of the slip ratio and the step two s Obtaining the slip rate of the wheel along the direction of the wheel;
wherein s is x Slip ratio, Δ x, for the wheel facing direction p Is the distance between rut units, n is the number of wheel spines, beta s Is the slip angle of the wheel, r is the wheel radius; by measuring the angle theta between the line of the track contour and the leaving segment of the track 1 And width of rut unit Δ x p Or directly evaluating cos beta with known slip angle s The slip rate s of the wheel along the direction of the wheel can be obtained x 。
2. The method according to claim 1, wherein the wheel in the first step is straight-through wheel-spine.
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| CN111462091B (en) * | 2020-04-02 | 2023-06-06 | 哈尔滨工业大学 | Wheel detection method and detection device of detection equipment |
| CN113524975A (en) * | 2021-08-20 | 2021-10-22 | 吉林大学 | Mileage statistics wheel |
| CN113705498B (en) * | 2021-09-02 | 2022-05-27 | 山东省人工智能研究院 | Wheel slip state prediction method based on distribution propagation diagram network |
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| CN101000282A (en) * | 2006-12-15 | 2007-07-18 | 哈尔滨工业大学 | Multifunction test device for wheel motion performance of planetary detection robot |
| CN103217302A (en) * | 2013-03-19 | 2013-07-24 | 哈尔滨工业大学 | Planet car wheel testing device |
| CN104198200A (en) * | 2014-08-08 | 2014-12-10 | 江苏大学 | Test method of slippage rate of tractor |
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