CN117492451B - Safety threshold control method for electric wheelchair - Google Patents
Safety threshold control method for electric wheelchair Download PDFInfo
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- CN117492451B CN117492451B CN202410001425.8A CN202410001425A CN117492451B CN 117492451 B CN117492451 B CN 117492451B CN 202410001425 A CN202410001425 A CN 202410001425A CN 117492451 B CN117492451 B CN 117492451B
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- 238000000034 method Methods 0.000 title claims abstract description 45
- 238000005096 rolling process Methods 0.000 claims abstract description 26
- 230000004044 response Effects 0.000 claims abstract description 15
- 230000001276 controlling effect Effects 0.000 claims description 10
- 238000007781 pre-processing Methods 0.000 claims description 7
- 230000001105 regulatory effect Effects 0.000 claims description 4
- 229910010293 ceramic material Inorganic materials 0.000 abstract 1
- 238000004519 manufacturing process Methods 0.000 abstract 1
- 230000007306 turnover Effects 0.000 abstract 1
- 230000008569 process Effects 0.000 description 20
- 230000001133 acceleration Effects 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000004364 calculation method Methods 0.000 description 2
- 230000001174 ascending effect Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000003708 edge detection Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 238000003709 image segmentation Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000011218 segmentation Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 238000012876 topography Methods 0.000 description 1
Classifications
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61G—TRANSPORT, PERSONAL CONVEYANCES, OR ACCOMMODATION SPECIALLY ADAPTED FOR PATIENTS OR DISABLED PERSONS; OPERATING TABLES OR CHAIRS; CHAIRS FOR DENTISTRY; FUNERAL DEVICES
- A61G5/00—Chairs or personal conveyances specially adapted for patients or disabled persons, e.g. wheelchairs
- A61G5/04—Chairs or personal conveyances specially adapted for patients or disabled persons, e.g. wheelchairs motor-driven
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61G—TRANSPORT, PERSONAL CONVEYANCES, OR ACCOMMODATION SPECIALLY ADAPTED FOR PATIENTS OR DISABLED PERSONS; OPERATING TABLES OR CHAIRS; CHAIRS FOR DENTISTRY; FUNERAL DEVICES
- A61G5/00—Chairs or personal conveyances specially adapted for patients or disabled persons, e.g. wheelchairs
- A61G5/10—Parts, details or accessories
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61G—TRANSPORT, PERSONAL CONVEYANCES, OR ACCOMMODATION SPECIALLY ADAPTED FOR PATIENTS OR DISABLED PERSONS; OPERATING TABLES OR CHAIRS; CHAIRS FOR DENTISTRY; FUNERAL DEVICES
- A61G2203/00—General characteristics of devices
- A61G2203/10—General characteristics of devices characterised by specific control means, e.g. for adjustment or steering
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61G—TRANSPORT, PERSONAL CONVEYANCES, OR ACCOMMODATION SPECIALLY ADAPTED FOR PATIENTS OR DISABLED PERSONS; OPERATING TABLES OR CHAIRS; CHAIRS FOR DENTISTRY; FUNERAL DEVICES
- A61G2203/00—General characteristics of devices
- A61G2203/10—General characteristics of devices characterised by specific control means, e.g. for adjustment or steering
- A61G2203/22—General characteristics of devices characterised by specific control means, e.g. for adjustment or steering for automatically guiding movable devices, e.g. stretchers or wheelchairs in a hospital
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61G—TRANSPORT, PERSONAL CONVEYANCES, OR ACCOMMODATION SPECIALLY ADAPTED FOR PATIENTS OR DISABLED PERSONS; OPERATING TABLES OR CHAIRS; CHAIRS FOR DENTISTRY; FUNERAL DEVICES
- A61G2203/00—General characteristics of devices
- A61G2203/70—General characteristics of devices with special adaptations, e.g. for safety or comfort
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- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Animal Behavior & Ethology (AREA)
- General Health & Medical Sciences (AREA)
- Public Health (AREA)
- Veterinary Medicine (AREA)
- Electric Propulsion And Braking For Vehicles (AREA)
Abstract
The present invention relates generally to the field of movement control of electric wheelchairs. In particular to a safety threshold control method of an electric wheelchair, which comprises the following steps: acquiring a rolling angle, a ground gradient and a ground image in front of the electric wheelchair; in response to the grade being less than or equal to the second grade preset value or the travel speed being less than or equal to the second speed preset value, the roll angle is greater than the first safety thresholdControlling the wheelchair to stop; in response to the grade being greater than the second grade preset value and the travel speed being greater than the second speed preset value, the roll angle is greater than the second safety thresholdControlling the wheelchair to decelerate;in,for adjusting the coefficients;in,is a natural constant which is used for the production of the high-temperature-resistant ceramic material,in order to adjust the coefficient of the power supply,for the flatness of the ground surface, the surface of the ground is provided with a plurality of grooves,in order to achieve the speed of travel,is rated speed; flatness is obtained from an imageObtaining the product. The wheelchair solves the problems that the wheelchair is easy to turn over at a higher speed when turning on a road with a larger gradient, and the possibility of turning over is higher when the road is uneven.
Description
Technical Field
The present invention relates generally to the field of movement control of electric wheelchairs. More particularly, the invention relates to a safety threshold control method for an electric wheelchair.
Background
At present, a large number of people with inconvenient movement need to move by means of a wheelchair, the people with inconvenient movement can be disabled people or partial patients, and with the improvement of the living standard of people, electric wheelchairs are becoming more popular, and common people can also move by means of the electric wheelchairs. However, the electric wheelchair may travel at a high speed, the ground may be uneven, and the gradient of the ground may be large, so that safety problems in moving the electric wheelchair should be emphasized.
The electric wheelchair turns on a road with a larger gradient at a higher running speed, and the probability of turning on the side is higher when the road is uneven, namely, the safety problem is easy to occur.
Disclosure of Invention
In order to solve one or more of the above-mentioned problems, the present invention proposes to make the electric wheelchair travel more safely by lowering the safety threshold of the rolling angle when the gradient is greater than the second gradient preset value and the travel speed is greater than the second speed preset value. To this end, the present invention provides solutions in various aspects as follows.
In a first aspect of the embodiments of the present invention, there is provided a method for controlling a safety threshold of an electric wheelchair, including:acquiring images of a rolling angle of the electric wheelchair, a gradient of the ground and the ground in front of the electric wheelchair; controlling the electric wheelchair to stop running in response to the gradient being smaller than or equal to a second gradient preset value or the running speed being smaller than or equal to a second speed preset value, wherein the rolling angle is larger than a first safety threshold; controlling the electric wheelchair to decelerate in response to the grade being greater than a second grade preset value and the travel speed being greater than a second speed preset value, the roll angle being greater than a second safety threshold; the second safety threshold value is according toObtained by (1), wherein->For a second safety threshold, ++>For a first safety threshold, ++>For adjusting the coefficients; the adjustment coefficient is according to->Obtained by (1), wherein->For regulating the coefficient->For the flatness of the ground +.>Is natural constant (18)>For the driving speed +.>A rated speed for the electric wheelchair; the flatness is obtained from the image.
In one embodiment, the electric wheelchair is controlled to stop traveling in response to the gradient being greater than a first gradient preset value or the traveling speed of the electric wheelchair being greater than a first speed preset value.
In one embodiment, the image is obtained by a camera or sensor on the electric wheelchair.
In one embodiment, the roll angle of the electric wheelchair is obtained from a gyroscope angle sensor of the electric wheelchair.
In one embodiment, the grade is obtained from a gyroscope angle sensor.
In one embodiment, the flatness is obtained from the image, comprising: preprocessing the image, wherein the preprocessing comprises graying to obtain a gray image; dividing the gray level image to obtain a ground area gray level image; and obtaining the flatness according to the ground area gray level image, wherein the flatness is more than or equal to 0 and less than or equal to 1.
In one embodiment, the roll angle of the electric wheelchair is obtained from a gyro angle sensor of the electric wheelchair, comprising: the roll angle is obtained from quaternion data obtained by the gyroscope angle sensor.
The beneficial effects of the invention include:
when the gradient is smaller than or equal to a second gradient preset value or the running speed is smaller than or equal to a second speed preset value, the possibility of safety accidents of the electric wheelchair is smaller, if the rolling angle is smaller than or equal to a first safety threshold, the running safety of the electric wheelchair is higher, if the rolling angle is larger than the first safety threshold, the possibility of safety accidents of the electric wheelchair in the running process is higher, and in order to enable the electric wheelchair to run more safely, the electric wheelchair is controlled to stop running.
When the gradient is larger than a second gradient preset value and the running speed is larger than a second speed preset value, the possibility of safety accidents of the electric wheelchair is larger, and if the rolling angle is larger than a second safety threshold, the second safety threshold is smaller than the first safety threshold, and in order to enable the electric wheelchair to run more safely, the electric wheelchair is controlled to decelerate.
The smaller the flatness of the ground, the smaller the adjustment coefficient and thus the smaller the second safety threshold. The larger the travel speed, the smaller the adjustment coefficient and, in turn, the smaller the second safety threshold. Therefore, the electric wheelchair is safer in the running process, and the probability of rollover of the electric wheelchair in the running process is smaller.
When the gradient is greater than the first gradient preset value, the electric wheelchair is more likely to generate safety accidents during running at the gradient, and when the running speed of the electric wheelchair is greater than the first speed preset value, the running speed of the electric wheelchair is too fast, so that the safety accidents are more likely to occur, and in order to enable the running of the electric wheelchair to be safer, the electric wheelchair is controlled to stop running.
Drawings
The above, as well as additional purposes, features, and advantages of exemplary embodiments of the present invention will become readily apparent from the following detailed description when read in conjunction with the accompanying drawings. In the drawings, embodiments of the invention are illustrated by way of example and not by way of limitation, and like reference numerals refer to similar or corresponding parts and in which:
fig. 1 is a flowchart schematically showing a safety threshold control method of an electric wheelchair according to an embodiment of the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are some, but not all embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.
Fig. 1 is a flowchart schematically showing a safety threshold control method of an electric wheelchair according to an embodiment of the present invention. As shown in fig. 1, first, according to a first aspect of the present invention, there is provided a safety threshold control method of an electric wheelchair,comprising the following steps: acquiring images of a rolling angle of the electric wheelchair, a gradient of the ground and the ground in front of the electric wheelchair; controlling the electric wheelchair to stop running in response to the gradient being smaller than or equal to a second gradient preset value or the running speed being smaller than or equal to a second speed preset value, wherein the rolling angle is larger than a first safety threshold; controlling the electric wheelchair to decelerate in response to the grade being greater than a second grade preset value and the travel speed being greater than a second speed preset value, the roll angle being greater than a second safety threshold; the second safety threshold value is according toObtained by (1), wherein->For a second safety threshold, ++>For a first safety threshold, ++>For adjusting the coefficients; the adjustment coefficient is according to->Obtained by (1), wherein->For regulating the coefficient->For the flatness of the ground surface,is natural constant (18)>For the driving speed +.>A rated speed for the electric wheelchair; the flatness is obtained from the image.
The specific description is as follows, as shown in fig. 1, including steps S1 to S3:
in step S1, an image of a roll angle of an electric wheelchair, a gradient of a ground surface, and a ground surface in front of the electric wheelchair is acquired.
The roll angle of the electric wheelchair at the current moment is obtained, wherein the roll angle of the electric wheelchair is the angle of rotation of the electric wheelchair around the longitudinal axis of the vehicle body, in other words, the roll angle is usually based on the longitudinal center line of the electric wheelchair, and the inclination angle of the left side or the right side of the vehicle body relative to the horizontal plane is measured, and is a positive value. The larger the rolling angle of the electric wheelchair is, the greater the possibility of rollover of the electric wheelchair is, and the greater the possibility of safety accidents of the electric wheelchair is. Acquiring the rolling angle of the electric wheelchair at the current moment is helpful for evaluating the safety of the electric wheelchair in the driving process.
The method comprises the steps of obtaining the gradient of the ground at the current moment of the electric wheelchair, wherein the gradient of the ground refers to the inclination degree or gradient of the surface of the ground relative to the horizontal plane, and the gradient is used for describing the change condition of the ground and the fluctuation degree of the topography. In one embodiment, the slope is expressed in degrees, and is positive when the ground exhibits an ascending inclination and positive when the ground exhibits a descending inclination, that is, irrespective of the fact that the slope is negative, the slope indicates the degree of inclination of the ground. The larger the gradient, the greater the inclination of the ground. When the electric wheelchair runs on the ground with a larger gradient, safety accidents such as rollover and the like are more likely to occur particularly when the ground with a larger gradient turns. For example, when the electric wheelchair is driven on an uphill, the electric wheelchair needs more traction force to overcome gravity and resistance to keep advancing, and if the gradient is too large, the electric wheelchair may lose traction force and cannot continue advancing or is easy to slip; when the electric wheelchair runs down a slope, the electric wheelchair may accelerate due to the increase of the gradient, and thus it is difficult for a driver to control the electric wheelchair. Therefore, a large gradient may have an important influence on the traction of the electric wheelchair, possibly affecting the driving stability and safety. The electric wheelchair is beneficial to evaluating the safety of the electric wheelchair in the running process by acquiring the gradient of the ground at the current moment.
The method comprises the steps of acquiring an image of the ground in front of the electric wheelchair at the current moment, and acquiring the flatness of the ground, wherein the flatness influences the safety of the electric wheelchair in the running process. Because there is a certain difference between the image of the ground with the larger flatness and the image of the ground with the smaller flatness, and the different ground images with the larger flatness have similar characteristics, the different ground images with the smaller flatness have similar characteristics.
In step S2, in response to the gradient being equal to or less than a second gradient preset value or the running speed being equal to or less than a second speed preset value, the rolling angle is greater than a first safety threshold, and the electric wheelchair is controlled to stop running.
When the gradient of the ground where the electric wheelchair is located at the current moment is smaller than or equal to the second gradient preset value, the electric wheelchair is smaller in possibility of safety accidents in the running process, the rolling angle of the electric wheelchair at the current moment is allowed to be larger, the rolling angle is smaller than or equal to the first safety threshold, and at the moment, the running safety requirement of the electric wheelchair can still be met. In one embodiment, the second grade preset value may be set to 10 degrees. In other embodiments, the practitioner may set the second gradient preset value according to the specific implementation scenario by himself, so that when the rolling angle of the electric wheelchair at the current moment is smaller than or equal to the first safety threshold, the running safety requirement of the electric wheelchair is still satisfied.
In one embodiment, the electric wheelchair has at least one speed gear, the different gears corresponding to different nominal speeds, the greater the gear, the greater the nominal speed of the electric wheelchair, for example, having 5 speed gears, the nominal speed of the electric wheelchair being 6 kilometers per hour, approximately equal to 1.67 meters per second, when the electric wheelchair is in the 5 th gear.
When the running speed of the electric wheelchair at the current moment is smaller than or equal to the preset value of the second speed, the electric wheelchair is less likely to have a safety accident when running at the speed, the rolling angle of the electric wheelchair at the current moment is allowed to be larger, and when the rolling angle is smaller than or equal to the first safety threshold, the running safety requirement of the electric wheelchair can still be met. In one embodiment, the electric wheelchair is rated at a speed of 6 km/h, approximately equal to 1.67 m/s, and the second speed preset may be set at 1 m/s when the electric wheelchair is in the 5 th gear. In other embodiments, the practitioner may set the second speed preset value according to the specific implementation scenario, so that when the rolling angle of the electric wheelchair at the current moment is smaller than or equal to the first safety threshold, the requirement of the running safety of the electric wheelchair is still satisfied.
In order to reduce the possibility of safety accidents of the electric wheelchair, for example, in order to reduce the possibility of rollover of the electric wheelchair during running, the electric wheelchair is controlled to stop running in response to the gradient being smaller than or equal to a second gradient preset value or the running speed being smaller than or equal to a second speed preset value, and the rolling angle is larger than a first safety threshold. In one embodiment, the first safety threshold may be set at 15 degrees. In other embodiments, the first safety threshold may be set by the practitioner according to the specific implementation scenario, so that the running safety requirement of the electric wheelchair is satisfied when the gradient is less than or equal to the second gradient preset value or the running speed is less than or equal to the second speed preset value.
In step S3, in response to the gradient being greater than a second gradient preset value and the travel speed being greater than a second speed preset value, the roll angle is greater than a second safety threshold, the electric wheelchair is controlled to decelerate. Specifically, in response to the gradient being greater than a second gradient preset value and the travel speed being greater than a second speed preset value, the roll angle is greater than a second safety threshold, controlling the electric wheelchair to decelerate; the second safety threshold value is according toObtained by (1), wherein->For a second safety threshold, ++>For a first safety threshold, ++>For adjusting the coefficients; the adjustment coefficient is according to->Obtained by (1), wherein->For regulating the coefficient->For the flatness of the ground +.>Is natural constant (18)>For the driving speed +.>A rated speed for the electric wheelchair; the flatness is obtained from the image.
When the gradient of the ground of the electric wheelchair at the current moment is greater than a second gradient preset value and the running speed of the electric wheelchair at the current moment is greater than a second speed preset value, the possibility of safety accidents occurring in the running process of the electric wheelchair is greater, in order to improve the safety of the electric wheelchair in the running process, when the rolling angle of the electric wheelchair at the current moment is greater than a second safety threshold value, the electric wheelchair is controlled to decelerate, in one embodiment, the electric wheelchair is controlled to decelerate to be smaller than or equal to a third speed preset value, and then the deceleration is stopped, wherein the third speed preset value is the product of an adjustment factor and the second speed preset value, the adjustment factor is greater than or equal to 0 and smaller than 1, and the larger the adjustment factor is, the speed of the electric wheelchair after deceleration is smaller. In one embodiment, the implementer can set the adjustment factor according to the specific implementation scene by himself so as to meet the safety requirement in the running process of the electric wheelchair. Wherein the second safety threshold is less than the first safety threshold.
The larger the adjustment coefficient, the larger the second safety threshold. In order to obtain a second safety threshold which is more suitable and smaller than the first safety threshold, the second safety threshold is made to be as large as possible on the premise of meeting the safety requirement of the electric wheelchair driving, and the second safety threshold is based on the following conditionsThe adjustment coefficient is obtained according to->Obtained. />The value of (2) is greater than 0 and less than or equal to 1.
In one embodiment of the present invention, in one embodiment,taking 1.5. In other embodiments, the implementer can set the adjustment coefficient according to the specific implementation scene by himself so as to obtain a more suitable adjustment coefficient, and under the premise of meeting the safety requirement of the electric wheelchair in the driving process, obtain a larger adjustment coefficient as much as possible so as to obtain a larger second safety threshold.
The flatness of the ground and the second safety threshold value are in positive correlation. The smaller the flatness of the ground, the smaller the adjustment coefficient and thus the smaller the second safety threshold. The running speed of the electric wheelchair and the second safety threshold value are in a negative correlation. The larger the travel speed, the smaller the adjustment coefficient and, in turn, the smaller the second safety threshold.The purpose of (1) is to make->The accuracy of the obtained adjustment coefficient is not affected by being too small.
The image of the ground in front of the electric wheelchair at the current moment contains the flatness information of the ground, and the flatness of the ground can be obtained by acquiring the characteristic information related to the flatness in the image. For example, the features include texture, edges, corner points, etc., which may be obtained using techniques such as filters, edge detection algorithms, or corner point detection algorithms. The use of image processing and the like to obtain the flatness of the ground is well known in the art.
When the gradient is greater than the second gradient preset value and the running speed is greater than the second speed preset value, at this time, safety accidents are easy to occur in the running process of the electric wheelchair, and in order to reduce the possibility of safety accidents of the electric wheelchair, for example, in order to reduce the possibility of rollover of the electric wheelchair in the running process, when the rolling angle is greater than the second safety threshold value, the electric wheelchair is controlled to decelerate.
In one embodiment, the electric wheelchair is controlled to stop traveling in response to the gradient being greater than a first gradient preset value or the traveling speed of the electric wheelchair being greater than a first speed preset value.
The electric wheelchair is not safe when traveling on the ground with a larger gradient. When the gradient of the ground of the electric wheelchair at the current moment is larger than the first gradient preset value, the possibility of safety accidents is higher when the electric wheelchair runs on the ground with the gradient, and in order to enable the electric wheelchair to run more safely, the electric wheelchair is controlled to stop running, that is, the electric wheelchair is controlled to be in a braking state. In one embodiment, the first grade preset value may be set to 15 degrees. In other embodiments, the operator can set the magnitude of the first gradient preset value according to the specific implementation scenario, so as to meet the requirement of the running safety of the electric wheelchair.
The greater the travel speed of the electric wheelchair, the safer it is. When the running speed of the electric wheelchair at the current moment is greater than the first speed preset value, the electric wheelchair is more likely to have a safety accident when running at the speed, and the electric wheelchair is controlled to stop running, namely, is controlled to be in a braking state in order to make the running of the electric wheelchair safer. In one embodiment, the electric wheelchair is rated at a speed of 6 km/h, approximately equal to 1.67 m/s, and the first speed threshold may be set at 1.67 m/s when the electric wheelchair is in the 5 th gear. In other embodiments, the first speed preset value can be set by the practitioner according to the specific implementation scenario, so as to meet the requirement of the electric wheelchair on running safety.
In one embodiment, the image is obtained by a camera or sensor on the electric wheelchair. The image is taken by a camera or sensor at the current moment.
In one embodiment, the roll angle of the electric wheelchair is obtained from a gyroscope angle sensor of the electric wheelchair.
In one embodiment, the roll angle is obtained from quaternion data obtained by the gyroscope angle sensor.
The rotation angle of the electric wheelchair can be measured in real time by a gyroscope angle sensor arranged on the electric wheelchair, and the gyroscope angle sensor comprises a rolling angle, a pitch angle, a deflection angle and the like. The acceleration of the electric wheelchair in three axial directions, including longitudinal, transverse and vertical accelerations, can also be measured by the accelerometer. From these acceleration data, the roll angle of the electric wheelchair can be calculated by integration.
There is at least one method of measuring roll angle in the prior art. For example, quaternion data may be obtained by a gyro angle sensor, and a roll angle, a pitch angle, a yaw angle, and the like may be obtained from the quaternion data.
The quaternion method is applied to gyroscope data processing as follows:
definition of quaternion: on complex plane, ordered four elementsCalled a quaternion, in which each element is complex and the following condition is satisfied: />，/>. It can be seen from the definition of the quaternion that the real part of the quaternion is zero and the sum of squares of the imaginary parts is-1.
Thus, a quaternion represents a rotation, the unitization of which is expressed as:
wherein, the method comprises the steps of, wherein,is natural constant (18)>Indicating the rotation angle +.>Representing imaginary units, ++>、/>、/>Respectively indicate winding->、/>、/>The angle of rotation of the shaft.
The three angular velocity components output by the gyroscope can be expressed as three unit quaternions, and the rotation angle and the rotation speed of the carrier relative to the inertia space can be calculated by multiplying and adding the three quaternions.
In particular, assuming that the carrier coordinate system coincides with the navigation coordinate system, the rotation of the carrier relative to the inertial space may be expressed as three unit quaternions、/>And->Wherein->、/>、/>Respectively indicate winding->、/>And->Quaternion of shaft rotation.
By multiplying and adding the three quaternions, the rotation angle and rotation speed of the carrier relative to the navigation coordinate system can be calculated. For example, aroundAngle of rotation of the shaft>The calculation can be made by the following formula:wherein, the method comprises the steps of, wherein,、/>、/>respectively indicate->、/>、/>Is a complex conjugate of (a) and (b).
By unitizing and quaterning three angular velocity components output by the gyroscope, the rotation angle and rotation speed of the carrier relative to the inertia space can be obtained.
In addition, quaternion data obtained by the gyro angle sensor can be converted into euler angles, and the euler angles are composed of three independent angles, and are generally expressed by Yaw (Yaw), pitch (Pitch) and Roll (Roll), so that Roll angles, pitch angles, yaw angles and the like are obtained.
In one embodiment, the grade is obtained from a gyroscope angle sensor.
The quaternion data obtained by the gyroscope angle sensor can be converted into Euler angles, and the obtained pitch angle is the gradient.
In one embodiment, the flatness is obtained from the image, comprising: preprocessing the image, wherein the preprocessing comprises graying to obtain a gray image; dividing the gray level image to obtain a ground area gray level image; and obtaining the flatness according to the ground area gray level image, wherein the flatness is more than or equal to 0 and less than or equal to 1.
The image is first subjected to necessary preprocessing steps, for example, graying to obtain a gray image, and then subjected to denoising operation, etc., so as to improve the accuracy of subsequent processing. The ground area is segmented from the image by utilizing the image segmentation technology in the prior art, so that the ground area gray level image can be obtained, wherein the ground area gray level image can be realized by methods of threshold segmentation, edge tracking, area growth and the like.
One method of calculating ground flatness is: and calculating standard deviation of all gray pixel values in the gray image of the ground area. Or calculating standard deviation of at least two gray pixel points in the gray image of the ground area, for example, in order to increase the calculation speed, a plurality of gray pixel points can be uniformly selected, and the standard deviation is calculated, for example, gray pixel points are selected in an interlaced manner, gray pixel points are selected in a row to be selected in an interval manner, and the standard deviation of the selected gray pixel values is calculated.
If the calculated standard deviation is larger than the preset bump threshold, the ground flatness corresponding to the gray level image of the ground area is made to be the first preset flatness, because if the ground is flatter, the probability of the corresponding standard deviation is larger; the larger the standard deviation is, the smaller the ground flatness is, the larger the possibility that the ground flatness is smaller is, when the standard deviation is larger than a preset bumping threshold value, the larger the possibility that the ground flatness is smaller is indicated, the lower safety of the electric wheelchair in the driving process is higher, and the second safety threshold value is further reduced so as to meet the safety requirement of the electric wheelchair in the driving process. In one embodiment, the first preset flatness may be set to 0.7. In other embodiments, the first preset flatness may be set by the practitioner according to a specific implementation scenario, so as to meet the safety requirement in the running process of the electric wheelchair.
If the calculated standard deviation is smaller than or equal to the preset bumping threshold value, the ground flatness corresponding to the ground area gray level image is 1, because the influence of the ground flatness on the safety in the running process of the electric wheelchair is low and can be ignored when the ground flatness is large.
When the preset bumping threshold takes a larger value, the flatness of the ground has lower influence on the safety of the electric wheelchair in the running process. When the preset bumping threshold takes a smaller value, the flatness of the ground has higher influence on the safety of the electric wheelchair in the running process. In one embodiment, the practitioner can set the preset bump threshold according to the specific implementation scenario by himself, so as to meet the safety requirement in the running process of the electric wheelchair.
When the speed gear of the electric wheelchair is the 5 th gear, the rated speed of the electric wheelchair in the gear is 1.67 m/s, and the adjustment coefficient is 1.5: when the gradient is 9 degrees and the running speed is 0.9 meter per second, the first safety threshold value is 15 degrees; table 1 is a second safety threshold value table for the travel speed of the electric wheelchair with the rated speed of 1.67 meters per second, the gradient of greater than 10 degrees, the travel speed of greater than 1 meter per second, the adjustment coefficient of 1.5, and the flatness of 1 or 0.7, when the speed of the electric wheelchair is the 5 th gear.
Table 1 shows the second safety threshold value when the flatness is 1 or 0.7
In the description of the present specification, the meaning of "a plurality", "a number" or "a plurality" is at least two, for example, two, three or more, etc., unless explicitly defined otherwise.
While various embodiments of the present invention have been shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. Many modifications, changes, and substitutions will now occur to those skilled in the art without departing from the spirit and scope of the invention. It should be understood that various alternatives to the embodiments of the invention described herein may be employed in practicing the invention.
Claims (5)
1. A method for controlling a safety threshold of an electric wheelchair, comprising:
acquiring the rolling angle of an electric wheelchair, the gradient of the ground and the image of the ground in front of the electric wheelchair; the rolling angle of the electric wheelchair is the angle of the electric wheelchair rotating around the longitudinal axis of the vehicle body;
controlling the electric wheelchair to stop running in response to the gradient being smaller than or equal to a second gradient preset value or the running speed being smaller than or equal to a second speed preset value, wherein the rolling angle is larger than a first safety threshold;
controlling the electric wheelchair to decelerate in response to the grade being greater than a second grade preset value and the travel speed being greater than a second speed preset value, the roll angle being greater than a second safety threshold; the second safety threshold value is according toObtained by (1), wherein->For a second safety threshold, ++>For a first safety threshold, ++>For adjusting the coefficients; the adjustment coefficient is according toObtained by (1), wherein->For regulating the coefficient->For the flatness of the ground +.>Is natural constant (18)>For the driving speed +.>A rated speed for the electric wheelchair; the flatness is obtained according to the image;
wherein, the roll angle of electronic wheelchair is obtained according to the gyroscope angle sensor of electronic wheelchair, includes: the rolling angle is obtained according to quaternion data, and the quaternion data is obtained by the gyroscope angle sensor; the quaternion data is obtained through a gyroscope angle sensor according to a quaternion method, and the quaternion method is applied to gyroscope data processing as follows:
definition of quaternion: on complex plane, ordered four elementsCalled a quaternion, in which each element is complex and the following condition is satisfied: />，/>The method comprises the steps of carrying out a first treatment on the surface of the The definition of the quaternion shows that the real part of the quaternion is zero, and the square sum of the imaginary parts of the quaternion is-1;
the quaternion represents a rotation, the unitization of which is expressed as:
wherein->Is natural constant (18)>Indicating the rotation angle +.>Representing imaginary units, ++>、/>And->Respectively indicate winding->、/>And->An angle of rotation of the shaft; three angular velocity components output by the gyroscope are expressed as three unit quaternions, and the carrier relative to inertia is obtained through multiplication and addition operation on the three quaternionsRotation angle and rotation speed of the space; the carrier coordinate system coincides with the navigation coordinate system, and the rotation of the carrier relative to the inertial space is expressed as three unit quaternions +.>、/>Andwherein->、/>And->Respectively indicate winding->、/>And->A quaternion of the shaft rotation; the rotation angle and the rotation speed of the carrier relative to the navigation coordinate system are obtained through multiplication and addition operation on the three quaternions; wherein, wind->Angle of rotation of the shaft>Calculated by the following formula:
wherein->、/>And->Respectively indicate->、/>And->Complex conjugate of (2);
the rotation angle and the rotation speed of the carrier relative to the inertia space are obtained through unitization and quaternion operation on three angular velocity components output by the gyroscope; the quaternion data obtained by the gyroscope angle sensor is converted into Euler angles, and the Euler angles are composed of three independent angles and are expressed by Yaw (Yaw), pitch (Pitch) and Roll (Roll), so that a Roll angle, a Pitch angle and a Yaw angle are obtained.
2. The electric wheelchair safety threshold control method of claim 1 further comprising: and controlling the electric wheelchair to stop running in response to the gradient being greater than a first gradient preset value or the running speed of the electric wheelchair being greater than a first speed preset value.
3. The method of claim 1, wherein the image is obtained by a camera or sensor on the electric wheelchair.
4. The electric wheelchair safety threshold control method of claim 1 wherein the grade is obtained from a gyroscopic angle sensor.
5. The electric wheelchair safety threshold control method of claim 1 wherein the flatness is obtained from the image, comprising:
preprocessing the image, wherein the preprocessing comprises graying to obtain a gray image;
dividing the gray level image to obtain a ground area gray level image;
and obtaining the flatness according to the ground area gray level image, wherein the flatness is more than or equal to 0 and less than or equal to 1.
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